HK1127720B

HK1127720B - Spatial information detecting device

Info

Publication number: HK1127720B
Application number: HK09106830.2A
Authority: HK
Inventors: 熊原稔; 桥本裕介; 坂本慎司; 高田裕司
Original assignee: Panasonic Corporation
Priority date: 2006-10-18
Filing date: 2007-10-10
Publication date: 2012-06-01

Description

Spatial information detection apparatus

Technical Field

The present invention relates to a spatial information detecting apparatus that detects spatial information, such as a distance from an object and a reflectivity of the object, using intensity-modulated light based on a relationship between the intensity-modulated light projected toward a target space and the intensity-modulated light reflected by the object located in the target space.

Background

Japanese patent application publication No.2004-45304 discloses a technique of measuring a distance to an object located in a target space by using intensity-modulated light. When intensity-modulated light of a sinusoidal waveform is used, light reflected from an object remains in a sinusoidal waveform with a phase difference that varies with distance from the object. Accordingly, the distance to an object in the illuminated target space can be measured based on the phase difference between the emitted intensity modulated light and the reflected intensity modulated light.

Based on the intensity measurement of the received intensity-modulated light for each of the plurality of phase zones, the phase difference can be obtained from the relationship between the position of the phase zone and the received light intensity. For example, the received light intensity Ir may be expressed as Ir ═ η · I (t-d) + Ie, where I (t) represents the projected light intensity as a function of time t, η is the light attenuation factor due to the distance from or reflection coefficient at the object, Ie is the intensity of ambient (interference) light, and d is the delay time corresponding to the distance L from the object and is expressed as d ═ 2L/c.

The above expression has three unknowns: attenuation factor η, delay time d, and intensity Ie of the ambient light, which may be obtained by measuring the intensity of the received light at three or more different times, respectively. Therefore, the distance to the object and the reflection coefficient of the object can be obtained as spatial information. Since the intensity-modulated light is generally designed to periodically change its intensity, integration of the received-light intensity over a plurality of cycle periods can suppress the influence of fluctuations in ambient light or noise occurring in the device.

In order to detect spatial information using the above-described technique, it is necessary to accurately correlate the phase zone of the intensity-modulated light projected toward the target space and the phase zone of the received light. There are conventional techniques for extracting electric charges at a specific one of the phase zones from a light receiving element, one of which is to transmit a signal specifying a specific phase zone for extracting electric charges from a light receiving element having a control electrode for controlling the timing of extracting electric charges (as in the case of a light receiving element constituted by a Charge Coupled Device (CCD) or the like), and the other of which is to select only electric charges extracted in a period corresponding to the specific phase zone (as in the case of a light receiving element constituted by a photodiode or the like). In order to improve the measurement accuracy, the above-described techniques each have to precisely synchronize a signal supplied to the light-emitting element with another signal for charge extraction supplied to the light-receiving element.

However, the light emitting element, the light receiving element, and the circuit for generating signals related to these elements may be damaged due to their characteristics that vary according to varying ambient temperature and humidity. Therefore, even if the device is operated after calibration of the device, there is always a possibility that an error of the measurement result is increased due to environmental change.

Disclosure of Invention

The present invention has been achieved in view of the above problems. An object of the present invention is to provide a spatial information detecting apparatus which utilizes intensity-modulated light and is arranged to reduce detection errors due to changes in the surrounding environment to ensure accurate measurement.

The spatial information detecting apparatus according to the present invention includes: a light emitting element 100 that emits intensity-modulated light to a target space; a light receiving element 200 that receives intensity-modulated light reflected from an object in a target space; and an information output circuit 300 configured to extract a light intensity of light received at the light receiving element for each of the plurality of phase zones P0, P1, P2, and P3, to determine a relationship between the intensity-modulated light emitted from the light emitting element and another intensity-modulated light received at the light receiving element based on the extracted light intensity, and to output spatial information within the target space.

In order to generate intensity-modulated light from the light emitting element, the spatial information detecting apparatus includes: a light emission signal generation circuit 10 configured to generate a light emission timing signal that determines a light emission timing of the light emitting element; and a light emitting element driving circuit 30 configured to output a light emitting element driving signal in response to the light emission timing signal so as to generate intensity-modulated light from the light emitting element.

Further, in order to operate the light receiving element to receive light at each phase zone, the apparatus includes: a light receiving element driving circuit 40 configured to output a plurality of light receiving element driving signals having a phase difference with each other to the light receiving elements; and a detection signal generation circuit 20 configured to supply a detection timing signal, which determines a timing of generating the light receiving element driving signal, to the light receiving element driving circuit. The spatial information detecting device of the present invention is characterized by having timing synchronization circuits 70, 70A and 70B configured to compare a periodic variation E2 relating to the output of the light emitting element driving circuit with periodic variations D1, D2 determined by the detection timing signal and to correct at least one of the detection timing signal and the light emission timing signal to maintain a constant phase difference between these periodic variations.

With this arrangement, it is possible to synchronize the phase of the intensity-modulated light from the light-emitting element with the timing of receiving the intensity-modulated light at the light-receiving element, thereby making the operation timings at the light-emitting element and the light-receiving element drive circuit coincide even in the event of a possible response change occurring in the components thereof due to a change in the ambient environment, and thus providing an accurate measurement that is not affected by the change in the ambient environment.

Preferably, the timing synchronization circuit is configured to obtain the periodic variation of the light-receiving element driving signal D2 from the light-receiving element driving circuit 40 as the periodic variation to be determined by detecting the timing signal for comparison with the light-emitting element driving signal E2 from the light-emitting element driving circuit.

It is also preferable that the timing synchronization circuit 70 is configured to correct the light emission timing signal to a corrected light emission timing signal and feed the corrected light emission timing signal to the light emitting element driving circuit. With this configuration, it is made possible to adjust the phase of the intensity-modulated light from the light emitting element to match the timing of receiving the intensity-modulated light at the light receiving element, thereby making the operation timing on the light emitting element side coincide with the operation timing on the light receiving element side. In this case, the synchronization of the operation timing between the light emitting element and the light receiving element can be performed only by the correction of the light emission timing signal for determining the periodic variation of the intensity-modulated light from the light emitting element, which enables simplification of the circuit arrangement of the timing synchronization circuit.

In this regard, it is also preferable that the timing synchronization circuit 70 is interposed between the light emission signal generation circuit 10 and the light emitting element drive circuit 30, and includes: a phase adjustment circuit 76 configured to shift the phase of the light emission timing signal output from the light emission signal generation circuit to the light emitting element drive circuit 30 by a variable phase shift value; and a phase comparator 72 configured to determine the phase shift value in accordance with a phase difference between the periodic variation from the light receiving element driving circuit and a light emitting element driving signal E2 from the light emitting element driving circuit.

Preferably, the light receiving element driving circuit 40 is configured to determine a light receiving element driving signal based on a plurality of detection timing signals D1 output from the detection signal generating circuit 20, and includes a selector 80, the selector 80 being configured to selectively extract one of a plurality of light receiving element driving signals D2 that are mutually out of phase. In this case, the timing synchronization circuit 70 is configured to correct the light emission timing signal based on the phase difference between the light-receiving element driving signal D2 extracted by the selector 80 and the periodic variation E2 related to the output of the light-emitting element driving circuit 30. Therefore, the light emission timing signal can be adjusted within the period of one cycle based on the light receiving element driving signals each determining the phase intervals P0, P1, P2, and P3.

Preferably, the information output circuit 300 is configured to integrate the received light intensity over a plurality of times for each phase section respectively corresponding to the light-receiving element driving signals so as to obtain the spatial information based on the respective integrated values respectively for the phase sections. In this regard, the information output circuit is configured to extract the received light intensity from the light receiving element for each phase zone in synchronization with the light receiving element driving signal extracted from the selector. With this arrangement, the intensity of the intensity-modulated light received at the light-receiving element can be accurately obtained to improve the detection accuracy of the spatial information.

Further, the spatial information detecting apparatus of the present invention may include: an auxiliary phase adjustment circuit 90 interposed between the detection signal generation circuit 20 and the light-receiving element drive circuit 40 for shifting the phase of the detection timing signal D1 output to the light-receiving element drive circuit 40 by a variable phase shift value; and an auxiliary phase comparator 92 configured to detect a phase difference between the detection timing signal D1 and the periodic variation D2 output from the light reception drive circuit 40, so as to provide an output indicating the phase difference to the auxiliary phase adjustment circuit 90. With this arrangement, the auxiliary phase adjusting circuit can determine the phase shift value based on the phase difference so that the phase difference between the detection timing signal and the light receiving element driving signal from the light receiving element driving circuit is maintained at a predetermined value, thereby making it possible to maintain the phase difference between the light emitting element driving signal and the light receiving element driving signal constant to improve the detection accuracy of the spatial information.

The timing synchronization circuit 70, 70A may be configured to compare the periodic variation E2 associated with the output of the light-emitting element driving circuit 30 with the detection timing signal D1 from the detection signal generation circuit 20.

In this case, the timing synchronization circuit 70 may be configured to correct the light emission timing signal based on the above comparison, and supply the corrected light emission timing signal E1x to the light emitting element driving circuit 30.

Alternatively, the timing synchronization circuit 70A may be configured to correct the detection timing signal to a corrected detection timing signal (D1x) based on the above comparison, and supply the corrected detection timing signal to the light-receiving element drive circuit 40.

In the latter case, the timing synchronization circuit 70A is preferably interposed between the detection signal generation circuit 20 and the light receiving element drive circuit 40, and includes: a phase adjustment circuit 76A configured to shift the phase of the detection timing signal D1 output from the detection signal generation circuit to the light-receiving element drive circuit by a variable phase shift value; and a phase comparator 72A configured to determine the phase shift value based on a phase difference between the periodic variation from the light emitting element driving circuit and the detection timing signal from the detection signal generating circuit. With this arrangement, it is made possible to correct the timing of driving the light receiving element in accordance with the intensity-modulated light from the light emitting element, so that the intensity-modulated light can be received at the light receiving element in exact correspondence with the intensity-modulated light emitted from the light emitting element.

Further, the spatial information detecting apparatus of the present invention may be arranged to provide a timing adjustment function to the light emitting side and the light receiving side. In this case, the timing synchronization circuit includes a first timing synchronization circuit interposed between the light emission signal generation circuit and the light emitting element drive circuit, and a second timing synchronization circuit interposed between the detection signal generation circuit and the light receiving element drive circuit.

The first timing synchronization circuit 70 includes: a first phase adjustment circuit 76 configured to shift the phase of the light emission timing signal E1 output from the light emission signal generation circuit 10 to the light emitting element drive circuit 30 by a variable phase shift value; and a first phase comparator 72 configured to determine the phase shift value based on the phase difference between the periodic variation E2 output from the light-emitting element driving circuit 30 and the detection timing signal D1 from the detection signal generating circuit 20. Similarly, the second timing synchronization circuit 70A includes: a second phase adjustment circuit 76A configured to shift the phase of the detection timing signal D1 output from the detection signal generation circuit 20 by a variable phase shift value; and a second phase comparator 72A configured to determine the phase shift value based on the phase difference between the light emission timing signal E1 from the light emission signal generation circuit 10 and the light-receiving element driving signal D2 from the light-receiving element driving circuit 40. Therefore, complementary timing adjustments can be made more accurately on the light-emitting side and the light-receiving side.

When the timing adjustment is performed on the light receiving side, it is desirable to maintain a constant phase difference between the corrected detection timing signal from the timing synchronization circuit and the light receiving element driving signal from the light receiving element driving circuit, in consideration of a possible input-output delay in the light receiving element driving circuit itself due to the influence of the ambient temperature. In this case, the spatial information detecting apparatus of the present invention may include: an auxiliary phase adjustment circuit 90A configured to shift the phase of the corrected detection timing signal output to the light-receiving element drive circuit by a variable phase shift value; and an auxiliary phase comparator 92A configured to detect a phase difference between the corrected light emission timing signal and the light-receiving element driving signal D2 from the light-receiving element driving circuit 40, and to provide a corresponding output to the auxiliary phase adjustment circuit. The auxiliary phase adjustment circuit 90A determines the phase shift value based on the detected phase difference so that the phase difference between the corrected detection timing signal D1x from the timing synchronization circuit 70A and the light-receiving element drive signal D2 from the light-receiving element drive circuit 40 is maintained at a predetermined value. Therefore, it is possible to correct the timing of driving the light receiving element in phase with the intensity-modulated light from the light emitting element.

Further, the reference light receiving element 110 may be arranged to receive a portion of the intensity modulated light from the light emitting element to read out periodic variations related to the output of the light emitting element driving circuit.

The timing synchronization circuit 70B of the light receiving side may be configured to include: an oscillation circuit 78 configured to use a signal whose frequency varies with an input voltage and supply the signal as a corrected detection timing signal to the light receiving element driving circuit; and a phase comparator 72B configured to generate a voltage indicating a phase difference between the periodic variation E2 relating to the output of the light-emitting element driving circuit and the detection timing signal D1 from the detection signal generating circuit 20, and apply the voltage to the oscillation circuit. In this case, the detection timing signal fed to the light receiving element driving circuit can be corrected by the oscillation circuit so as to adjust the timing of operating the light receiving element in phase with the intensity-modulated light from the light emitting element.

The light receiving element may be an element such as a CCD image pickup element having a capacitive reactance and operating based on a direct current supplied from a direct current power supply. The capacitive reactance may be affected by the ambient temperature, which may cause a time delay from a planned start time specified by the detection timing signal D1 input to the light receiving element driving circuit 40 to a change in an actual start time at which the light receiving element 200 performs a predetermined operation in response to the light receiving element driving signal D2 generated from the light receiving element driving circuit 40. The present invention proposes a light receiving element driving circuit having an effective configuration for eliminating such an indeterminate time delay to enable more accurate detection of spatial information. The light receiving element drive circuit 40B includes: an output switch 50 connected between the direct current power supply and the light receiving element for supplying a direct current to the light receiving element in synchronization with the detection timing signal; a temperature sensor 150 for detecting an ambient temperature; and a current controller 160 for adjusting the current fed to the light receiving element in such a manner that the current maintains a predetermined rate of change. With this arrangement, the time delay from the reception time of the detection timing signal to the time when a current sufficient for full operation is supplied to the light receiving element can be adjusted so that the time delay between the occurrence of the detection timing signal and the actual start time of operating the light receiving element is kept constant so that the actual start time is substantially synchronized with the occurrence of the detection timing signal.

The current controller 160 may include a memory device 162, the memory device 162 storing a rate of change of the current flowing through the light receiving element in association with the temperature, and configured to read out a rate of change of the current corresponding to the temperature output from the temperature sensor from the memory device so as to control the current flowing through the light receiving element to match the read out rate of change of the current.

In addition to using control based on the ambient temperature, it is equally possible to control the output current flowing to the light receiving element based on the rate of change of the current flowing through the light receiving element. In this case, the light receiving element driving circuit 40, 40A includes: a current monitoring circuit 60 that monitors a rate of change of a current fed to the light receiving element and provides a current change output indicating the rate of change; and a current controller 66 that adjusts the current fed to the light receiving element in response to the current change output so that the current change rate is maintained at a predetermined value. Therefore, keeping the current supplied to the light receiving element at a constant rate of change enables the light receiving element to be operated after a constant time has elapsed from the reception of the detection timing signal, without being affected by environmental changes.

Preferably, the current monitoring circuit 60 includes: a differentiating circuit 62 that calculates an instantaneous rate of change of the current flowing through the light receiving element; and a peak detection circuit 64 for detecting a maximum value of the instantaneous rate of change obtained by the differentiation circuit. In this regard, the current controller is configured to control the current flowing through the light receiving element at a predetermined rate of change according to a maximum value of the instantaneous rate of change. This arrangement ensures stable control of the operation time of the light receiving element.

Further, the light receiving element driving circuit 40A may be configured to allow the following functions: the output current to the light receiving element is controlled based on the current flowing through the light receiving element only under a predetermined temperature condition. In this case, the light receiving element driving circuit 40A includes: a temperature sensor 130 for detecting an ambient temperature; a register 68 holding the maximum value of the instantaneous rate of change detected at the peak detection circuit 64; a temperature table 140 that stores outputs of the temperature sensors at predetermined time intervals; and a start circuit 120 for starting the differentiating circuit 62 and the peak detecting circuit 64 only when a temperature difference between the detected current temperature and a recorded previous temperature at a predetermined previous time exceeds a predetermined level. Therefore, the differentiating circuit and the peak detecting circuit can be kept deactivated in a temperature range adversely affecting the operation of the light receiving element to reduce power consumption.

The present invention may employ a timing synchronization circuit 70, the timing synchronization circuit 70 being configured to compare a periodic variation of a light emission timing signal from the light emission signal generation circuit with a periodic variation determined by detecting the timing signal. In this case, the timing synchronization circuit may include: an oscillation circuit 78, the oscillation circuit 78 using a signal whose frequency varies with an input voltage and supplying the signal to the light emitting element driving circuit as a corrected light emission timing signal; and a phase comparator 72, the phase comparator 72 generating a voltage indicating a phase difference between a periodic variation relating to an output of the light receiving element driving circuit and a light emission timing signal from the light emission signal generating circuit.

Drawings

Fig. 1 is a block diagram showing a spatial information detecting apparatus according to a first embodiment of the present invention;

fig. 2 is a block diagram showing an internal configuration of a phase comparator used in the above-described apparatus;

fig. 3 is a circuit diagram showing a driving circuit of a light emitting element used in the above-described apparatus;

fig. 4 shows a waveform diagram illustrating a timing adjustment operation of the above-described apparatus;

FIG. 5 is a block diagram showing a modification of the above-described apparatus;

fig. 6 is a block diagram showing a spatial information detecting apparatus according to a second embodiment of the present invention;

fig. 7 is a block diagram showing a spatial information detecting apparatus according to a third embodiment of the present invention;

fig. 8 is a block diagram showing a spatial information detecting apparatus according to a fourth embodiment of the present invention;

fig. 9 is a block diagram showing a spatial information detecting apparatus according to a fifth embodiment of the present invention;

fig. 10 is a block diagram showing a spatial information detecting apparatus according to a sixth embodiment of the present invention;

fig. 11 is a block diagram showing a spatial information detecting apparatus according to a seventh embodiment of the present invention;

fig. 12 is a block diagram showing a spatial information detecting apparatus according to an eighth embodiment of the present invention;

fig. 13 is a block diagram showing a spatial information detecting apparatus according to a ninth embodiment of the present invention;

fig. 14 is a block diagram showing a light receiving element driving circuit used in the apparatus of the present invention;

fig. 15 is a block diagram showing another light receiving element driving circuit used in the apparatus of the present invention;

fig. 16 is a block diagram showing a modification of the above-described light receiving element driving circuit; and

fig. 17 is a block diagram showing a spatial information detecting apparatus according to a tenth embodiment of the present invention.

Detailed Description

(first embodiment)

A spatial information detecting apparatus according to a first embodiment of the present invention is explained with reference to fig. 1 to 4. The spatial information detecting apparatus includes: a light emitting element 100 configured to emit intensity-modulated light to a target space; a light receiving element 200 configured to receive intensity-modulated light reflected from an object in a target space; and an information output circuit 300 configured to extract light intensity of light received at the light receiving element for each of the plurality of phase zones, to determine a relationship between the intensity-modulated light emitted from the light emitting element and another intensity-modulated light received at the light receiving element based on the extracted light intensity, and to output spatial information within the target space.

The light emitting element 100 is constituted by a light emitting diode, and the light emission intensity thereof is modulated at a frequency of 100Hz to 1GHz to provide intensity-modulated light of a sinusoidal waveform. The light receiving element 200 is implemented by a CCD image sensing element to receive intensity-modulated light reflected from an object in a target space, and the light receiving element 200 is disposed adjacent to the light emitting element 100 so as to receive the intensity-modulated light, which is emitted from the light emitting element 100 and reflected at the object while passing through an optical path twice the distance T from the light emitting element to the object. The light emitting element 100 is not necessarily limited to a light emitting diode, and may include other light sources. Further, the light receiving element 200 is not limited to the CCD, and may include a Complementary Metal Oxide Semiconductor (CMOS) image sensing element or the like.

The light emitting element 100 and the light receiving element 200 are configured to operate based on the light emission timing signal E1 output from the light emission signal generating circuit 10 and the detection timing signal output from the detection signal generating circuit 20, respectively. The light emission signal generation circuit 10 and the detection signal generation circuit 20 operate based on a common clock CLK generated in a timing generation circuit (not shown).

The light emission signal generation circuit 10 is connected to the light emitting element drive circuit 30 via a timing synchronization circuit 70 described later, and therefore the light emission timing signal E1 is corrected to a corrected timing signal E1x at the timing synchronization circuit 70, and then the corrected timing signal E1x is fed to the light emitting element drive circuit 30. Based on the corrected timing signal E1x, the light emitting element driving circuit 30 generates a light emitting element driving signal E2, which E2 drives the light emitting element 100 to generate intensity-modulated light. As shown in fig. 3, the light emitting element drive circuit 30 includes a field effect transistor FET 32 and a resistor 33 connected in series with the light emitting element 100 between the direct current power supply 31 and the ground, and is configured to turn on and off the FET 32 at the above-described frequency in response to the modified timing signal E1x of the rectangular waveform. That is, the light emitting element is turned on at the rising edge of the corrected light emission timing signal E1x, and is turned off at the falling edge of the corrected light emission timing signal E1 x. Thus, the light emitting element 100 is turned on and off at this frequency to emit light whose intensity varies sinusoidally as shown in fig. 4, thereby generating a sinusoidal waveform of intensity-modulated light IMR. The details of the timing synchronization circuit 70 will be discussed later.

The detection signal generation circuit 20 is connected to the light receiving element drive circuit 40, and the light receiving element drive circuit 40 generates a light receiving element drive signal D2 for driving the light receiving element 200 at a predetermined frequency based on the detection timing signal. The light receiving element 200 implemented by the CCD image sensing element has a capacitive reactance, and enters a state of accumulating electric charges in proportion to the intensity of the intensity-modulated light reflected from the object when charged to a predetermined level by the light receiving element driving signal D2. As shown in fig. 4, by repeating charging and discharging within one cycle period of the intensity modulated light, a plurality of phase zones P0, P1, P2, and P3 are provided to the light receiving element within the one cycle period. The electric charge accumulated for each phase zone, that is, the received light intensity, is read by the information output circuit 300, the information output circuit 300 determines the waveform of the received intensity-modulated light, calculates the phase difference f between the intensity-modulated light projected from the light emitting element 100 and the intensity-modulated light received at the light receiving element 200 based on the waveform, and obtains the distance to the light reflection object based on the phase difference f.

Referring to fig. 4, a scheme for calculating the phase difference f will be described. The phase zones P0, P1, P2, and P3 determined by the light-receiving element drive signal D2 are set to 0 ° to 90 °, 90 ° to 180 °, 180 ° to 270 °, and 270 ° to 360 °, respectively, of the phase of the intensity-modulated light IMR from the light-emitting element 100. Assuming that the light receiving element 200 receives light RFR reflected from an object in a target space to which intensity-modulated light is projected, the received-light amounts a0, a1, a2, and A3 at the respective phase intervals are obtained, respectively, and the relational expressions between the phase difference f and the received-light amounts a0, a1, a2, and A3 are established: phi is tan^-1(A3-A1)/(A0-A2). This calculation is performed at the information output circuit 300, and the information output circuit 300 calculates the distance L from the object (L ═ Φ · c/2f) again from the phase difference Φ, the frequency f of the intensity-modulated light, and the speed of light c thus obtained.

As can be understood from the above, an accurately obtained phase difference phi is necessary for measuring the distance to the object. For this reason, the received light intensity must be determined with precise timing synchronized with the waveform of the intensity-modulated light IMR. However, it is considered that there may be cases: since the intensity-modulated light from the light emitting element 100 does not precisely coincide with the light emission timing signal E1 due to the varying ambient temperature, it becomes important to correct the light emission timing signal E1 based on the actual waveform of the intensity-modulated light and the light receiving element driving signal D2. For example, as shown by the broken line in fig. 4, as the ambient temperature decreases, the phase of the light emitting element driving signal E2 defined by the current flowing through the light emitting element 100 will be delayed with respect to the light emission timing signal E1, resulting in a phase lag of the intensity modulated light IMR with respect to the light emission timing signal E1.

Due to the above, the present embodiment is configured to insert the timing synchronization circuit 70 between the light emission signal generation circuit 10 and the light emitting element drive circuit 30 so as to correct the phase of the light emission timing signal E1 such that the phase difference between the light emitting element drive signal E2 and the light receiving element drive signal D2 is maintained at zero or a predetermined constant value, and to prepare the light emitting element drive signal E2 based on the corrected light emission timing signal E1 x. As shown by the solid line in fig. 4, in response to the light-emitting element drive signal E2 thus prepared, the light-emitting element 100 generates intensity-modulated light IMR in synchronization with the phase of the light-receiving element drive signal D2. With this result, it is possible to precisely synchronize the respective phase zones P0, P1, P2, and P3 determined by the light-receiving element driving signal D2 with the intensity-modulated light from the light-emitting element 100, thereby enabling to obtain a precise phase difference f between the intensity-modulated light IMR from the light-emitting element 100 and the reflected light RFR at the light-receiving element 200, and to calculate a precise distance to the object based on the phase difference.

As shown in fig. 1, the timing synchronization circuit 70 includes: a phase comparator 72 configured to detect a phase difference between the light-emitting element drive signal E2 and the light-receiving element drive signal D2; and a phase adjustment circuit 76 configured to determine a phase shift value of the light emission timing signal E1 based on the phase difference output from the phase comparator 72. As shown in fig. 2, the phase adjustment circuit 76 includes: a waveform shaping circuit 73 configured to shape the light-emitting element drive signal E2 and the light-receiving element drive signal D2 into rectangular waveforms, respectively; a comparator 74 for comparing the waveform-shaped signals; and an integrator 75 configured to integrate the output of the comparator 74 to provide a phase shift value corresponding to the phase difference between the drive signals.

The light receiving element driving circuit 40 includes an output switch 50 for turning on and off the switch 50 in response to the detection timing signal D1 for supplying the current from the direct current power supply 210 to the light receiving element 200 to start the light receiving element 200 at the timing determined by the detection timing signal D1. That is, the drive circuit 40 is configured to cause the light receiving element 200 to be activated by a current from the direct current power supply 210 to enter an operation state for detecting the intensity of the reflected light. However, since the light receiving element 200 has a capacitive reactance, the following may occur: the current fed to the light receiving element 200, that is, the rate of change in the current of the light receiving element driving signal D2 changes in response to a significantly changing ambient temperature, resulting in a delay in activating the light receiving element 200 with respect to the detection timing signal D1. For example, when a significant drop in the ambient temperature is seen, the light receiving element driving signal D2, i.e., the driving current, is slowly increased to start the light receiving element 200 with a delay with respect to the detection timing signal D1.

In order to eliminate the above problem, the light receiving element driving circuit 40 of the present embodiment is configured to include: a current monitoring circuit 60 that monitors a current change rate of the current defined by the light receiving element driving signal D2; and a current controller 66 that adjusts, based on the output of the current monitoring circuit 60, a rate of change in current of the output current supplied from the dc power supply 210 to the light receiving element 200 via the output switch 50, that is, a rise time during which the current reaches a level at which the light receiving element 200 is actually activated and a fall time during which the current falls to a level at which the light receiving element 200 is deactivated. The output switch 50 includes an n-type Metal Oxide Semiconductor Field Effect Transistor (MOSFET)51 and a p-type MOSFET52 connected in series with the light receiving element 200 between the direct current power supply 210 and the ground, and the light receiving element 200 is connected between the connection point of these FETs and the ground. The detection timing signal D1 is input to the gate of the FET to turn on the FET 51 when the detection timing signal D1 is on, thereby supplying current from the dc power supply 210 to the light receiving element 200 to charge the light receiving element 200, and to turn on the FET52 when the detection timing signal D1 is off to discharge the light receiving element. A resistor 53 is interposed between the direct-current power supply 210 and the FET 51 for limiting the current fed to the light-receiving element 200, while a resistor 54 is interposed between the FET52 and the ground for limiting the discharge current from the light-receiving element.

The current monitoring circuit 60 includes: a differentiating circuit 62 that detects the instantaneous rate of change of the light receiving element drive signal D2, i.e., the current flowing through the light receiving element 200; and a peak detection circuit 64 that detects the maximum value of the instantaneous rate of change. The current controller 66 is configured to control the resistors 53 and 54 so as to maintain the rate of change of the current passing through the light receiving element 200 at a predetermined value in accordance with the maximum value of the rate of change output from the peak detection circuit 64. Thereby, it is possible to provide a constant activation time for activating the light receiving element 200 and a constant deactivation time for deactivating the element after receiving the detection timing signal D1 without being affected by the ambient temperature, thereby improving the detection accuracy of the spatial information.

Each of the resistors 53 and 54 is constituted by a MOSFET that continuously changes its on-resistance in response to a gate voltage of the MOSFET changed by an output of the current controller 66.

Fig. 5 shows a modification of the above-described embodiment, which is the same in configuration and function as the above-described embodiment except that a selector 80 is provided for selectively inputting a plurality of light-receiving element driving signals D2 to the phase comparator 72 of the timing synchronization circuit 70. Like parts are denoted by like reference numerals and thus will not be described again.

The light receiving element driving signals D2 are prepared in accordance with the four detection timing signals D1, respectively, to define phase sections P0, P1, P2, and P3 of intensity-modulated light. The selector 80 selects one of the light-receiving element driving signals D2 for feeding the selected one of the light-receiving element driving signals D2 to the phase comparator 72 to synchronize the light-receiving element driving signal D2 with the light-emitting element driving signal E2. For example, the first light receiving element driving signal D2 is selected during one period of the intensity-modulated light so as to specify the first phase zone P0, and the second light receiving element driving signal D2 is selected during the next period, and so on. In this way, timing adjustment can be performed over a plurality of periods by selecting different light receiving element driving signals D2 for different periods. Alternatively, the selector 80 may be arranged to select a random one of the four light receiving element driving signals D2 in consideration that the detection of the spatial information requires calculation over a plurality of cycles.

(second embodiment)

Fig. 6 shows a spatial information detecting device according to a second embodiment of the present invention, which is basically the same in configuration and function as the first embodiment except for an auxiliary phase adjusting circuit 90 interposed between the detection signal generating circuit 20 and the light receiving element driving circuit 40 for synchronizing the detection timing signal D1 with the light receiving element driving signal D2. This embodiment also uses the selector 80 having the above-described function. Like parts are denoted by like reference numerals and thus will not be described again.

The embodiment comprises the following steps: an auxiliary phase comparator 92 for phase comparison between the light-receiving element driving signal D2 and the detection timing signal D1 to cause the auxiliary phase adjustment circuit 90 to prepare a corrected detection timing signal D1x in response to the detected phase difference and feed the corrected detection timing signal D1x to the light-receiving element driving circuit 40 to thereby synchronize the detection timing signal D1 with the light-receiving element driving signal D2 and thus feed the detection timing signal D1 thus synchronized to the timing synchronization circuit 70 via the selector 80. With this result, the light-emitting element drive signal E2 is synchronized with the detection timing signal D1, that is, with the light-receiving element drive signal D2, thereby making it possible to keep the phase difference between the intensity-modulated light from the light-emitting element 100 and the light-receiving element drive signal D2 at zero or a predetermined value.

(third embodiment)

Fig. 7 shows a spatial information detecting device according to a third embodiment of the present invention, which is basically the same in configuration and function as the first embodiment except that a timing synchronization circuit 70A is provided on the driving path side of the driving light receiving element 200. Like parts are denoted by like reference numerals and are not described in detail.

A timing synchronization circuit 70A is interposed between the detection signal generation circuit 20 and the light-receiving element drive circuit 40 for comparing the detection timing signal D1 with the light-emitting element drive signal E2, correcting the detection timing signal D1 into a corrected detection timing signal D1x in accordance with the detected phase difference, and inputting the corrected detection timing signal D1x into the light-receiving element drive circuit 40, thereby synchronizing the light-receiving element drive signal D2 with the light-emitting element drive signal E2, that is, with the intensity-modulated light emitted from the light-emitting element 100. The timing synchronization circuit 70A has the same configuration as the first embodiment of fig. 1 and 2. With this result, the light receiving element 200 can detect the intensity of the reflected light from the object at each phase zone in accurate synchronization with the phase of the intensity-modulated light, thereby ensuring accurate detection of spatial information. In the present embodiment, the same selector 80 as used in the embodiment of fig. 5 is employed for selecting one of the four detection timing signals D1 for each different period of intensity-modulated light, and supplying the selected signal to the timing synchronization circuit 70A.

The timing synchronization circuit 70A includes: a phase comparator 72A configured to detect a phase difference between the light-emitting element drive signal E2 from the light-emitting element drive circuit 30 and the detection timing signal D1 from the detection signal generation circuit so as to provide a phase shift value corresponding to the detected phase difference; and a phase adjustment circuit 76A configured to shift the phase of the detection timing signal D1 by the phase shift value to correct the detection timing signal D1 and output a corrected detection timing signal D1 x.

(fourth embodiment)

Fig. 8 shows a spatial information detecting device according to a fourth embodiment of the present invention, which is basically the same in configuration and function as the third embodiment except that the reference light receiving element 110 is used to directly receive the intensity-modulated light from the light emitting element 100 so as to provide an output to the timing synchronization circuit 70A as an indication of the periodic variation in relation to the output of the light emitting element driving circuit 30. Like parts are denoted by like reference numerals and are not described in detail.

The reference light receiving element 110 is disposed adjacent to the light emitting element 100, for directly receiving the intensity-modulated light from the light emitting element 100, and outputting an in-phase signal to the timing synchronization circuit 70A. The reference light receiving element 110 uses a part of a CCD image sensing element that implements the light receiving element 200, and is oriented toward the light emitting element 100.

(fifth embodiment)

Fig. 9 shows a spatial information detecting apparatus according to a fifth embodiment of the present invention, which is basically the same as the third embodiment in configuration and function except that an auxiliary phase adjusting circuit 90A and an auxiliary phase comparator 92A having a similar configuration to that of the second embodiment of fig. 6 are used to make phase matching between the detection timing signal D1 and the light-receiving element driving signal D2. Like parts are denoted by like reference numerals and are not described in detail.

The auxiliary phase comparator 92A is configured to compare the phase of the corrected detection timing signal D1x from the timing synchronization circuit 70A with the phase of the light-receiving element driving signal D2, so that the auxiliary phase adjustment circuit 90A operates to further correct the corrected detection timing signal D1x into a further corrected detection timing signal D1y to be output to the light-receiving element driving circuit 40, so that the phase of the light-receiving element driving signal D2 matches the phase of the corrected detection timing signal D1x, that is, matches the phase of the intensity-modulated light synchronized with the corrected detection timing signal D1 x. With this result, it is possible to obtain the received light intensity for a phase zone strictly coinciding with the phase of the intensity-modulated light from the light-emitting element 100 to improve the detection accuracy of the spatial information.

(sixth embodiment)

Fig. 10 shows a spatial information detecting device according to a sixth embodiment of the present invention, which is substantially the same in configuration and function as the third embodiment except that a timing synchronization circuit 70A is configured to detect a phase difference between a light-receiving element driving signal D2 and a light-emitting element driving signal E2 for correcting a detection timing signal D1. Like parts are denoted by like reference numerals and are not described in detail.

The timing synchronization circuit 70A determines a phase difference between the light emitting element drive signal E2 and the light receiving element drive signal D2 output from the light receiving element drive circuit 40 via the selector 80A, corrects the detection timing signal D1 to a corrected detection timing signal D1x based on the phase difference, and inputs the corrected detection timing signal D1x to the light receiving element drive circuit 40. With this result, the light receiving element driving circuit 40 prepares the light receiving element driving signal D2 in phase with the intensity-modulated light from the light emitting element 100 so as to operate the light receiving element 200 in strict synchronization with the light emitting element 100.

(seventh embodiment)

Fig. 11 shows a spatial information detecting device according to a seventh embodiment of the present invention, in which a first timing synchronization circuit 70 and a second timing synchronization circuit 70A are formed on driving paths of a light emitting element 100 and a light receiving element 200, respectively. The configuration of the timing synchronization circuit and other parts is the same as that of the first or sixth embodiment. Like parts are denoted by like reference numerals and are not described in detail.

The first timing synchronization circuit 70 is interposed between the light emission signal generation circuit 10 and the light emitting element drive circuit 30, and is configured by a first phase comparator 72 and a first phase adjustment circuit 76, the first phase comparator 72 comparing the phase of the light emitting element drive signal E2 with the phase of the detection timing signal D1, the first phase adjustment circuit 76 correcting the light emission timing signal E1 to a corrected light emission timing signal E1x based on the detected phase difference, and outputting the corrected light emission timing signal E1x to the light emitting element drive circuit 30. A selector 80 is interposed between the first phase comparator 72 and the detection signal generation circuit 20 to sequentially output a plurality of detection timing signals to the first phase comparator 72 in a manner similar to the embodiment of fig. 6.

The second timing synchronization circuit 70A is interposed between the detection signal generation circuit 20 and the light receiving element drive circuit 40, and is configured by a second phase comparator 72A and a second phase adjustment circuit 76A, the second phase comparator 72A determines a phase difference between the light emission timing signal E1 and the light receiving element drive signal D2, the second phase adjustment circuit 76A corrects the detection timing signal D1 to a corrected detection timing signal D1x based on the detected phase difference, and outputs the corrected detection timing signal D1x to the light receiving element drive circuit 40. In this embodiment, one of the four light-receiving element drive signals D2 is selected for each cycle of intensity-modulated light using a selector 80A having the same configuration as that of the embodiment of fig. 5, and the selected signal is input to the second phase comparator 72A.

The two timing synchronization circuits 70 and 70A are used in the present embodiment to correct the light emission timing signal E1 and the detection timing signal D1 in a direction in which the phases of the light emission timing signal E1 and the detection timing signal D1 are closer to each other, thereby enabling the light receiving element 200 to be operated in precise phase synchronization with the intensity-modulated light from the light emitting element 100 to improve the detection accuracy of the spatial information.

(eighth embodiment)

Fig. 12 shows a spatial information detecting apparatus according to an eighth embodiment of the present invention, which is identical in configuration and function to the sixth embodiment of fig. 10 except for the internal configuration of the timing synchronization circuit 70B and the related configuration. Like parts are denoted by like reference numerals and are not described in detail.

The timing synchronization circuit 70B includes: an oscillation circuit 78 that generates a signal whose frequency varies with a varying input voltage; and a phase comparator 72B for detecting a phase difference between the detection timing signal D1 and the light-emitting element drive signal E2. The detected phase difference is fed to the oscillation circuit 78, and the oscillation circuit 78 then supplies a signal having a frequency that varies based on the phase difference, and outputs the signal to the light receiving element driving circuit 40 as a corrected detection timing signal D1 x. With this result, the light receiving element driving signal D2 becomes phase-synchronized with the intensity-modulated light from the light emitting element 100, thereby enabling the operation of the light emitting element 100 to be synchronized with the operation of the light receiving element 200.

(ninth embodiment)

Fig. 13 shows a spatial information detecting apparatus according to a ninth embodiment of the present invention, which is the same as the embodiment of fig. 12 except that a timing synchronization circuit 70B provides an output for defining a light emission timing signal. Like parts are denoted by like reference numerals and are not described in detail.

The timing synchronization circuit 70B includes a phase comparator 72B and an oscillation circuit 78. The phase comparator 72B is configured to compare the detection timing signal D1 from the detection-time generation circuit 20 with the light-emitting-element drive signal E2 from the light-emitting-element drive circuit 30 to supply a voltage indicating a phase difference between signals going to the oscillation circuit 78. In the present embodiment, the oscillation circuit 78 defines a light emission signal generation circuit and is configured to generate a light emission timing signal E1, outputting the light emission signal E1 to the light emitting element drive circuit 30. The oscillation circuit is provided for adjusting the frequency of the light emission timing signal E1 in accordance with the output voltage from the phase comparator 72B, and is configured to determine the frequency of the light emission timing signal E1 so as to maintain a constant phase difference between the detection timing signal D1 detected at the phase comparator 72B and the light emitting element driving signal E2. The detection timing signal D1 is fed to the phase comparator 72B via the selector 80 having the same configuration as the embodiment of fig. 11.

Fig. 14 shows an exemplary light receiving element driving circuit applicable to the above-described embodiment, which is substantially the same in operation as the light receiving element driving circuit 40 in the embodiment of fig. 1. Like parts are denoted by like reference numerals and are not described in detail.

The light receiving element drive circuit 40A includes: a current monitoring circuit 60 including a differentiating circuit 62 and a peak detecting circuit 64, the differentiating circuit 62 being configured to obtain an instantaneous rate of change of a light-receiving element driving current flowing through the light-receiving element 200; the peak detection circuit 64 is configured to detect a maximum value of the instantaneous rate of change obtained at the differentiation circuit 62. The maximum value of the rate of change detected at the peak detection circuit 64 is updated and stored in the register 68. As discussed with reference to the first embodiment, the current controller 66 controls the FETs 53 and 54 serving as a single resistor based on the maximum value of the rate of change in current read out from the register 68 so as to maintain the charging current flowing from the direct-current power supply 210 into the light receiving element 200 via the output switch 50 at a predetermined level and also maintain the discharging current flowing from the light receiving element 200 to the ground via the output switch 50 at a predetermined level. With this result, it is ensured that constant rise time and fall time are provided for the charging current and the discharging current flowing through the light receiving element 200 in response to the detection timing signal D1, which makes it possible to operate the light receiving element 200 without being affected by the ambient temperature for accurately detecting the spatial information.

The light receiving element drive circuit 40A includes: a temperature sensor 130 for sensing an ambient temperature; a temperature table 140 for storing the detected temperature at predetermined time intervals; and a start-up circuit 120 coupled to the temperature sensor 130 and the thermometer 140. The enabling circuit 120 is configured to compare the instantaneous temperature with a previous temperature recorded at a predetermined previous time and enable the differentiating circuit 62 and the peak detecting circuit 64 only if the temperature difference exceeds a predetermined threshold, otherwise disabling the differentiating circuit 62 and the peak detecting circuit 64. When the temperature difference is lower than the threshold value, the current controller 66 controls the current flowing through the light receiving element 200 based on the current value obtained from the register. Therefore, it is possible to deactivate the differentiating circuit and the peak detecting circuit in a temperature range that does not adversely affect the operation of the light receiving element 200, thereby reducing power consumption.

Fig. 15 shows another light receiving element driving circuit which is applicable to the above-described embodiment and can be configured to correct the rate of change of the light receiving element driving current D2 based on the ambient temperature to cancel the ambient temperature-dependent change in the operation response of the light receiving element 200. The light receiving element drive circuit 40B includes: a temperature sensor 150 for sensing an ambient temperature; and a memory device 162 for storing predetermined control parameters related to the detected temperature. The current controller 160 reads a control parameter corresponding to the detected temperature from the memory device 162 to apply a voltage defined by the control parameter to the gates of the FETs 53 and 54, which serve as resistors, respectively, to adjust the on-resistance of each FET, thereby maintaining a constant current change rate of the charging current flowing from the direct-current power supply 210 into the light-receiving element 200 via the output switch 50 and the discharging current flowing from the light-receiving element 200 to the ground via the output switch 50. With this result, it is ensured that constant rise time and fall time are provided for the charge current and the discharge current flowing through the light receiving element 200, which makes it possible to operate the light receiving element 200 without being affected by the ambient temperature for accurately detecting the spatial information.

Fig. 16 shows a current control scheme applicable to the light receiving element driving circuit described above. In the present example, a plurality of direct current power supplies 210A, 210B, and 210C are used to supply current from any combination of direct current power supplies to the light receiving element 200 while interposing the output switches 50A, 50B, and 50C between the respective direct current power supplies and the ground. Each output switch has the same configuration as the output switch used in the embodiment of fig. 1. The light receiving element 200 is connected to the FETs 51A, 52A connected in series; 51B, 52B; 51C, 52C, and ground. The gates of the FETs defining each output switch are connected to each other for simultaneously receiving the detection timing signal D1 to turn on and off the FETs for charging and discharging the light receiving element 200 according to the detection timing signal D1 in a similar manner as in the embodiment of fig. 1.

Each of the output switches 50A, 50B, and 50C is connected in series with each of the charging current control FETs 53A, 53B, and 53C serving as resistors, and is also connected in series with each of the discharging current control FETs 54A, 54B, and 54C serving as resistors. The current controller 160 activates any combination of the charging current control FET and the discharging current control FET to cause a current to flow through the light receiving element 200 at a predetermined rate of change. The current controller 160 supplies an analog voltage of a defined current value corresponding to a predetermined rate of change to the analog-to-digital converter 164, and the analog-to-digital converter 164 generates digital signals that respectively determine the combination of the charge current control FETs 53A, 53B, and 53C to be turned on and the combination of the discharge current control FETs 54A, 54B, and 54C to be turned on. The digital signal is applied to the gates of the charge current control FET and the discharge current control FET to turn on the FETs of the designated combination to control the current flowing through the light receiving element 200.

Accordingly, the plurality of charging-current control FETs respectively connected to the plurality of output switches can be turned on in any combination, thereby enabling accurate control of the charging current flowing to the light receiving element 200. In this example, the charging-current control FETs 53A, 53B, and 53C are fabricated to have equal or different on-resistances. The same is true for the discharge current control FETs 54A, 54B, and 54C.

(tenth embodiment)

Fig. 17 shows a spatial information detecting apparatus according to a tenth embodiment of the present invention, which is identical in configuration and function to the embodiment of fig. 1 and 5 except for the internal configuration of the timing synchronization circuit 70. Like parts are denoted by like reference numerals and are not described in detail.

The timing synchronization circuit 70 includes an oscillation circuit 78 and a phase comparator 72, the oscillation circuit 78 being for generating a signal whose frequency varies with the input voltage, the phase comparator 72 being for detecting a phase difference between the light emission timing signal E1 and the light-receiving element driving signal D2. The detected phase difference is fed to the oscillation circuit 78 in the form of a voltage signal, and the oscillation circuit 78 supplies a signal whose frequency varies with the phase difference and outputs the signal to the light-receiving element driving circuit 30 as a corrected light emission timing signal E1 x. With this result, the intensity-modulated light in phase with the light-receiving element driving signal D2 is emitted from the light-emitting element 100, so that the operation of the light-emitting element 100 can be synchronized with the operation of the light-receiving element 200.

The individual features and modifications thereof described in each of the above embodiments may be combined with or replaced by features and modifications thereof of other embodiments within the scope of the present invention.

Further, although the above-described embodiment is explained as being for obtaining the distance to the object in the target space as one typical spatial information, the present invention should not be limited thereto, and the present invention may be equally applied to identifying the object based on the reflectance of light from the object, which is obtained by analyzing the intensity of intensity-modulated light reflected from the object.

Claims

1. A spatial information detecting apparatus, comprising:

a light emitting element (100) configured to emit intensity-modulated light to a target space;

a light emission signal generation circuit (10) configured to generate a light emission timing signal (E1) that determines a light emission timing of the light emitting element;

a light emitting element driving circuit (30) configured to output a light emitting element driving signal (E2) in response to the light emission timing signal so as to generate the intensity-modulated light from the light emitting element;

a light receiving element (200) configured to receive the intensity modulated light reflected from an object in the target space;

an information output circuit (300) configured to extract, for each of a plurality of phase zones (P0, P1, P2, and P3), light intensity of light received at the light receiving element, determine a relationship between the intensity-modulated light from the light emitting element and the intensity-modulated light received at the light receiving element based on a variation in the extracted light intensity, and output spatial information within the target space;

a light-receiving element drive circuit (40; 40A; 40B) configured to output a plurality of light-receiving element drive signals (D2) having phase differences with each other to the light-receiving elements to activate the light-receiving elements for each of the phase sections;

a detection signal generation circuit (20) configured to supply a detection timing signal (D1) to the light-receiving element drive circuit to determine a timing of generating the light-receiving element drive signal; and

a timing synchronization circuit (70; 70A; 70B) configured to compare a periodic variation related to an output of the light emitting element driving circuit with a periodic variation determined by the detection timing signal and to correct at least one of the detection timing signal (D1) and the light emission timing signal (E1) to maintain a constant phase difference between the periodic variations,

wherein the timing synchronization circuit (70) is configured for obtaining from the light-receiving element drive circuit a periodic variation of the light-receiving element drive signal (D2) as the periodic variation to be determined by the detection timing signal for comparison with a light-emitting element drive signal (E2) from the light-emitting element drive circuit (30).

2. The spatial information detecting device as set forth in claim 1, wherein said timing synchronization circuit (70) is configured to modify said light emission timing signal to a modified light emission timing signal (E1x) and to feed said modified light emission timing signal to said light emitting element driving circuit.

3. The spatial information detecting device according to claim 1, further comprising:

an auxiliary phase adjustment circuit (90) interposed between the detection signal generation circuit (20) and the light-receiving element drive circuit (40), configured to shift the phase of the detection timing signal by a variable phase shift value, and output the detection timing signal to the light-receiving element drive circuit;

an auxiliary phase comparator (92) configured to detect a phase difference between the detection timing signal (D1) and a periodic variation (D2) output from the light-receiving element driving circuit to provide an output indicating the phase difference to the auxiliary phase adjustment circuit;

the auxiliary phase adjustment circuit (90) is configured to determine the phase shift value based on the phase difference so that a phase difference between the detection timing signal (D1) and the light-receiving element driving signal (D2) from a light-receiving element driving circuit is maintained at a predetermined value.

4. A spatial information detecting apparatus, comprising:

wherein the timing synchronization circuit (70) is interposed between the light emission signal generation circuit (10) and the light emitting element drive circuit (30), and includes:

a phase adjustment circuit (76) configured to shift a phase of a light emission timing signal output from the light emission signal generation circuit to the light emitting element drive circuit (30) by a variable phase shift value; and

a phase comparator (72) configured to determine the phase shift value according to a phase difference between the periodic variation output from the light-receiving element driving circuit and a light-emitting element driving signal from the light-emitting element driving circuit (30).

5. A spatial information detecting apparatus, comprising:

wherein the timing synchronization circuit (70) is configured to modify the light emission timing signal to a modified light emission timing signal (E1x) and to feed the modified light emission timing signal to the light emitting element driving circuit, an

Wherein the light receiving element driving circuit (40) is configured to determine the light receiving element driving signal based on a plurality of detection timing signals output from the detection signal generating circuit, and

a selector (80) is provided for selectively extracting light receiving element drive signals that are out of phase with each other,

the timing synchronization circuit (70) is configured to correct the light emission timing signal based on a phase difference between the light-receiving element driving signal (D2) selected from the selector (80) and a periodic variation (E2) related to an output of the light-emitting element driving circuit (30).

6. The spatial information detecting device according to claim 5, wherein said information output circuit (300) is configured to integrate received light intensities over a plurality of times for each of said phase sections (P0, P1, P2, P3) corresponding to said light-receiving element driving signals, said information output circuit being configured to obtain received light intensities from said light-receiving elements (200) at each of said phase sections (P0, P1, P2, P3) in synchronization with a light-receiving element driving signal (D2) selected from said selector (80).

7. A spatial information detecting apparatus, comprising:

wherein the timing synchronization circuit (70; 70A) is configured to compare a periodic variation (E2) caused by an output of the light-emitting element drive circuit (30) with the detection timing signal (D1) from a detection signal generation circuit (20).

8. The spatial information detecting device as set forth in claim 7, wherein said timing synchronization circuit (70) is configured to modify said light emission timing signal to provide a modified light emission timing signal (E1x) to said light emitting element driving circuit.

9. The spatial information detecting device as set forth in claim 7, wherein said timing synchronization circuit (70A) is configured to correct said detection timing signal (D1) to a corrected detection timing signal (D1x) and to supply the corrected detection timing signal to said light receiving element driving circuit (40).

10. The spatial information detecting device according to claim 9, wherein said timing synchronization circuit (70A) is interposed between said detection signal generating circuit (20) and said light receiving element driving circuit (40), and includes:

a phase adjustment circuit (76A) configured to shift a phase of the detection timing signal (D1) from the detection signal generation circuit by a variable phase shift value and output the detection timing signal to the light-receiving element drive circuit (40); and

a phase comparator (72A) configured to determine the phase shift value based on a phase difference between a periodic variation output from the light emitting element driving circuit and the detection timing signal from the detection signal generation circuit.

11. The spatial information detecting device as set forth in claim 9, further comprising:

an auxiliary phase adjustment circuit (90A) interposed between the timing synchronization circuit (70A) and the light-receiving element drive circuit (40), and configured to shift the phase of the corrected detection timing signal (D1x) by a variable phase shift value;

an auxiliary phase comparator (92A) configured to detect a phase difference between the corrected detection timing signal (D1x) and a light-receiving element drive signal (D2) from the light-receiving element drive circuit (40) to provide an output indicative of the phase difference to the auxiliary phase adjustment circuit (90A), and

the auxiliary phase adjustment circuit (90A) is configured to determine the phase shift value based on the phase difference so that a phase difference between the corrected detection timing signal (D1x) from the timing synchronization circuit (70A) and the light-receiving element drive signal (D2) from a light-receiving element drive circuit (40) is maintained at a predetermined value.

12. The spatial information detecting device as set forth in claim 9, further comprising:

a reference light receiving element (110) configured to receive a portion of the intensity modulated light from the light emitting element to output a corresponding light intensity; and

the timing synchronization circuit (70A) is configured to use light intensity as an indication of a periodic variation related to an output of the light-emitting element driving circuit (30).

13. The spatial information detecting device as set forth in claim 9, wherein said timing synchronization circuit (70B) comprises:

an oscillation circuit (78) configured to use a signal whose frequency varies with a varying input voltage and supply the signal to the light-receiving element drive circuit (40) as the corrected detection timing signal; and

a phase comparator (72B) configured to generate a voltage indicating a phase difference between a periodic variation (E2) relating to an output of the light-emitting element driving circuit (30) and a detection timing signal (D1x) from the detection signal generation circuit (20), and supply the voltage to the oscillation circuit.

14. A spatial information detecting apparatus, comprising:

wherein the timing synchronization circuit comprises:

a first timing synchronization circuit (70) interposed between the light emission signal generation circuit (10) and the light emitting element drive circuit; and

a second timing synchronization circuit (70A) interposed between the detection signal generation circuit and the light-receiving element drive circuit;

the first timing synchronization circuit (70) includes: a first phase adjustment circuit (76) configured to shift a phase of the light emission timing signal (E1) from the light emission signal generation circuit by a variable phase shift value and output the light emission timing signal to the light emitting element drive circuit (30); and a first phase comparator (72) configured to determine the phase shift value based on a phase difference between a periodic variation (E2) output from the light-emitting element driving circuit (30) and the detection timing signal (D1) from the detection signal generation circuit (20);

the second timing synchronization circuit (70A) includes: a second phase adjustment circuit (76A) configured to shift a phase of the detection timing signal (D1) from the detection signal generation circuit (20) by a variable phase shift value and output the detection timing signal to the light-receiving element drive circuit (40); and a second phase comparator (72A) configured to determine the phase shift value based on a phase difference between the light emission timing signal (E1) from the light emission signal generation circuit (10) and the light-receiving element driving signal (D2) from the light-receiving element driving circuit (40).

15. A spatial information detecting apparatus, comprising:

wherein the light receiving element has a capacitive reactance and is configured to operate based on a direct current supplied from a direct current power supply (210), the light receiving element driving circuit (40B) includes:

an output switch (50) connected between the direct-current power supply and the light-receiving element, for supplying the direct current to the light-receiving element in synchronization with the detection timing signal;

a temperature sensor (150) for detecting an ambient temperature; and

a current controller (160) configured to adjust the current fed to the light receiving element in such a manner that the current fed to the light receiving element maintains a predetermined rate of change.

16. The spatial information detecting device according to claim 15, wherein said current controller (160) includes a memory means (162), the memory means (162) being configured to store a rate of change of a current flowing through said light receiving element in association with a temperature,

the current controller is configured to read out a current change rate corresponding to the temperature output from the temperature sensor (150) from the memory device (162), and control the current flowing through the light receiving element to match the read out current change rate.

17. A spatial information detecting apparatus, comprising:

wherein the light receiving element has a capacitive reactance and is configured to operate based on a direct current supplied from a direct current power supply (210), the light receiving element driving circuit (40A) includes:

a current monitoring circuit (60) configured to monitor a rate of change of a current fed to the light receiving element and provide a current change output indicative of the rate of change; and

a current controller (66) configured to operate in response to the current change output for adjusting the current fed to the light receiving element in such a manner that the current fed to the light receiving element maintains a predetermined rate of change.

18. The spatial information detecting device as set forth in claim 17, wherein said current monitoring circuit (60) comprises:

a differentiating circuit (62) configured to calculate an instantaneous rate of change of a current flowing through the light receiving element; and

a peak detection circuit (64) configured to detect a maximum value of the instantaneous rate of change from the differentiating circuit;

the current controller (66) is configured to control the current flowing through the light receiving element based on a maximum value of the instantaneous rate of change from the peak detection circuit to keep the rate of change at a predetermined value.

19. The spatial information detecting device as set forth in claim 18, wherein said light receiving element driving circuit further comprises:

a temperature sensor (130) for detecting an ambient temperature;

a register (68) configured to hold a maximum value of the instantaneous rate of change detected at the peak detection circuit (64);

a temperature table (140) configured to store an output of the temperature sensor at predetermined time intervals; and

a start-up circuit (120) for starting up the differentiating circuit and the peak detecting circuit only when a temperature difference between the detected current temperature and a recorded previous temperature at a predetermined previous time exceeds a predetermined level.

20. A spatial information detecting apparatus, comprising:

a light emitting element drive circuit (30) configured to output a light emitting element drive signal (E2) to generate the intensity modulated light at the light emitting element in response to the light emission timing signal;

an information output circuit (300) configured to obtain, for each of a plurality of phase zones (P0, P1, P2, and P3), a light intensity of light received at the light receiving element, determine a relationship between the intensity-modulated light from the light emitting element and the intensity-modulated light received at the light receiving element based on a change in the light intensity, and output spatial information within the target space;

a timing synchronization circuit (70; 70A; 70B) configured to compare a periodic variation of a light emission timing signal from the light emission signal generation circuit with a periodic variation determined by the detection timing signal and to correct at least one of the detection timing signal (D1) and the light emission timing signal (E1) to maintain a constant phase difference between the periodic variations;

wherein the timing synchronization circuit (70) comprises:

an oscillation circuit (78) configured to use a signal whose frequency varies with an input voltage and supply the signal to the light emitting element driving circuit as the corrected detection timing signal (E1 x); and

a phase comparator (72) configured to generate a voltage indicating a phase difference between a periodic variation (D2) relating to an output of the light-receiving element driving circuit and a light emission timing signal (E1) from the light emission signal generating circuit, and supply the voltage to the oscillation circuit.