JP2009182445A - Imaging device - Google Patents

Abstract

A pixel value of a light modulation image is set to an appropriate value.
An arithmetic processing unit (4) includes a subject (person's character) based on a position (pixel coordinates) of a face region extracted in the region extraction process and a distance to the subject (X) estimated from the size of the face region. One or more light emitting diodes 1a are selected from the range in which the distance from the face) X is relatively closest. Then, the arithmetic processing unit 4 controls the light emission control unit 2 so that only the selected one or more light emitting diodes 1a are lit. Therefore, the modulated light is emitted from the light emitting unit 1 only to a narrow area including the person's face in the target space, and the amount of the modulated light is adjusted to a level corresponding to the distance to the person's face. The pixel value of the light modulation image can be set to an appropriate value.
[Selection] Figure 1

Description

  The present invention relates to an imaging device that captures a target space and acquires a light modulation image.

The present applicant has already proposed a face authentication system that can ensure high authentication accuracy even under outdoor sunlight by acquiring a stable grayscale image that is not affected by ambient light (for example, sunlight). (For example, refer to Patent Document 1). In this face authentication system, an imaging device that captures the face of a person to be authenticated irradiates a target region with modulated light obtained by high-speed modulation of infrared light emitted from a light-emitting diode, and receives the light with an imaging device comprising a CCD. A reflected light component of modulated light and a reflected light component of ambient light are distinguished from each other, and an image (light modulated image) containing only the modulated light is acquired. Then, in the authentication device of the face authentication system, the position of the person's face is detected from the light modulation image acquired by the imaging device, the feature amount of the person's face is extracted from the pixel value of the position, and the feature amount is extracted. The face of the person corresponding to the template is authenticated by collating with a template registered in advance.
JP 2006-155422 A

  By the way, in the imaging device for acquiring a light modulation image as described above, not only the pixel value decreases as the distance to the subject (such as a person's face) increases, but also when the distance to the subject is too close. There is a problem that the pixel value is saturated. Therefore, exposure control is necessary to set the pixel value to an appropriate value, but general exposure control, for example, adjustment of exposure time and aperture only allows the pixel value of the light modulation image to be an appropriate value. It was difficult to control the exposure.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging apparatus capable of setting the pixel value of a light modulation image to an appropriate value.

  In order to achieve the above object, the invention according to claim 1 outputs modulated light irradiation means for irradiating the target space with modulated light, an image sensor for receiving light incident from the target space, and each pixel of the image sensor. A light-modulated image generating means for generating a light-modulated image having only the reflected light component of the modulated light as a pixel value by processing the processed signal, and a specific feature from the light-modulated image generated by the light-modulated image generating means An area extracting means for extracting the area having the exposure, and an exposure control means for adjusting the modulated light by controlling the modulated light irradiation means so that the pixel value of the area extracted by the area extracting means falls within a predetermined appropriate range; The modulated light irradiating means has a plurality of light sources that irradiate light to different positions in the target space, and the exposure control means is adapted to the position and size of the area extracted by the area extracting means, Turn on and off multiple light sources It is characterized by adjusting the either one of at least a light emission amount.

  According to the invention of claim 1, the modulated light irradiation means has a plurality of light sources that irradiate light to different positions in the target space, and the exposure control means includes the position of the region extracted by the region extraction means and Depending on the size, at least one of the lighting and extinction of multiple light sources or the amount of light emission is adjusted, so that the pixel value of the light-modulated image is adjusted appropriately by increasing or decreasing the amount of light incident from a region with a specific feature It can be set to any value.

  According to a second aspect of the present invention, in the first aspect of the invention, the modulated light irradiation means has a plurality of types of light sources that are different from each other in at least one of the irradiation range and the light emission amount, and the exposure control means is an area extraction means. In accordance with the position and size of the plurality of extracted regions, at least one of turning on and off the plurality of types of light sources and the amount of emitted light is adjusted.

  According to the second aspect of the present invention, when a plurality of regions having specific characteristics are extracted, the amount of light incident from each region is increased or decreased separately to set the pixel value of the light modulation image to an appropriate value. it can.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, when the region having a specific feature is moving, the image processing device includes a predicting unit that predicts a moving direction and a distance of the region, and controls exposure. The means adjusts at least one of lighting and extinction of a plurality of light sources and a light emission amount according to the movement direction and movement distance of the region predicted by the prediction means.

  According to the invention of claim 3, even when an area having a specific feature moves, the pixel value of the light modulation image can be set to an appropriate value.

  According to a fourth aspect of the present invention, according to any one of the first to third aspects, the region extracting means extracts a human face as a region having a specific feature.

  The invention according to claim 5 is the invention according to any one of claims 1 to 3, wherein the region extracting means extracts a region drawn with a character or a specific pattern as a region having a specific feature. And

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the region extracting means extracts a region that moves as a region having a specific feature.

  A seventh aspect of the invention is characterized in that, in the invention of any one of the first to sixth aspects, the light modulation image generating means integrates a plurality of time-modulated light modulation images.

  According to the invention of claim 7, by integrating a plurality of time-modulated light modulation images, a random noise component included in each light modulation image is attenuated, and light modulation with a high signal-to-noise ratio is performed. An image can be obtained.

  According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the region extracting unit extracts a moving region as a region having a specific feature, and the light modulation image generating unit includes a plurality of temporally continuous light beams. The modulation image is integrated so that the regions overlap.

  According to the invention of claim 8, even when a region having a specific feature moves, a random noise component included in a plurality of light modulation images is attenuated to obtain a light modulation image with a high signal-to-noise ratio. be able to.

  According to the present invention, the pixel value of the light modulation image can be set to an appropriate value.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, the imaging apparatus A according to the present embodiment is configured as a face authentication apparatus that detects a person's face from the light modulation image and authenticates the individual by comparing the detected person's face with a pre-registered template. Has been.

  FIG. 5 shows a system configuration example of a security system for an apartment house including the imaging device (face authentication device) A of the present embodiment. This security system for collective housing is installed in a collective housing such as a condominium. In addition to the imaging device A, the lobby intercom B, the alarm monitoring panel C, the electric lock control device D, the elevator control panel E, the home delivery It consists of a box control panel F, a system control panel G, a numeric keypad H, a housing information panel (not shown) installed in each dwelling unit, and the like.

  The lobby intercom B is equipped with a camera for imaging visitors, a telephone device for making calls with the alarm monitoring panel C and the housing information panel, and a numeric keypad for the visitors to enter the dwelling unit number of the visited unit. It is installed outside the common entrance J of the apartment house. When a visitor operates the numeric keypad of the lobby intercom B and inputs the dwelling unit number of the visited residence unit, the lobby intercom B passes through the alarm monitoring panel C to the housing information panel installed in the dwelling unit of that dwelling unit number. Thus, a call signal and a visitor image captured by the camera of the lobby intercom B are transmitted. And in the house information board which received the calling signal, the image received from the lobby intercom B is displayed on the display and the calling sound is emitted from the speaker. When the resident of the dwelling unit presses the response button on the housing information board, a communication path is formed between the housing information board and the lobby intercom B, and the visitor and the resident use the lobby intercom B and the housing information board, respectively. You can make a call. Since this type of lobby interphone B, alarm monitoring panel C, and house information panel are well known in the art, detailed illustration and description thereof will be omitted.

  The electric lock control panel D controls locking / unlocking of an electric lock (not shown) provided at the common entrance J. The elevator control panel E controls the operation of an elevator (not shown) installed in the apartment house. The delivery box control panel F controls locking / unlocking of delivery boxes installed in the apartment house. The system control panel G causes the electric lock control panel D to unlock the electric lock or causes the elevator control panel E to operate the elevator according to the control command transmitted from the house information panel and the authentication result of the imaging device A. The delivery box control panel F is made to unlock the delivery box. That is, when a resident of any dwelling unit operates the numeric keypad H to input an ID number assigned to the resident, the imaging apparatus A uses the template corresponding to the ID number received from the numeric keypad H. The resident's face is authenticated, and if authentication is possible, authenticable information is transmitted to the system control panel G. When the system control board G receives the information that can be authenticated from the image pickup apparatus A, the system control board G causes the electric lock control board D to unlock the electric lock, causes the elevator control board E to operate the elevator, or delivers to the home delivery box control board F. Unlock the box. On the other hand, if the authentication by the imaging device A is impossible, the system control panel G receives the information indicating that the authentication cannot be performed from the imaging device A, and does not unlock the electric lock to the electric lock control panel D, so that the elevator control panel E The elevator is not operated and the delivery box control panel F is not unlocked. Since the electric lock control device D, the elevator control panel E, and the delivery box control panel F are well known in the art, detailed illustration and description thereof are omitted.

  FIG. 1A shows a block diagram of the imaging apparatus A of the present embodiment. The imaging apparatus A of the present embodiment includes a light emitting unit 1, a light emission control unit 2, an imaging unit 3, an arithmetic processing unit 4, a template matching processing unit 5, and a memory unit 6. As shown in FIG. 1B, the light emitting unit 1 includes a plurality of light emitting diodes 1a arranged vertically and horizontally on the same plane, and a plurality of the light emitting diodes 1a individually or in groups of several. And a drive circuit (not shown) for lighting. The light emitting diode 1a emits infrared light. The light emission control unit 2 controls the drive circuit to drive the light emitting diode 1a at a very high frequency (for example, 10 megahertz), thereby irradiating the target space where the person is present with the modulated light. That is, in the present embodiment, the light emitting unit 1 and the light emission control unit 2 correspond to modulated light irradiation means.

  The imaging unit 3 is synchronized with the light emission period of the light emitting unit 1 based on an imaging device having sensitivity to infrared light (for example, a CCD <charge coupled device>) and a timing signal output from the light emission control unit 2. A signal processing circuit that performs processing for extracting only the reflected light component of infrared light from the output of each pixel of the image sensor (hereinafter referred to as “synchronous detection processing”), and infrared light on the light receiving surface of the image sensor. And a diaphragm arranged between the lens and the image sensor. The arithmetic processing unit 4 performs light modulation image generation processing for generating a light modulation image using the reflected light component extracted by the signal processing circuit as a pixel value, and a region having a specific feature (a person's face) from the light modulation image. Region extraction processing for extracting the region), exposure control processing for adjusting the modulated light by controlling the light emission control unit 2 so that the pixel value of the face region falls within a predetermined appropriate range, And a feature amount extraction process for extracting feature amounts (for example, information corresponding to features of facial organ shapes such as eyes, nose, and mouth). For example, the light modulation image generation is performed on a general-purpose microcomputer. This is realized by installing a program for performing processing, region extraction processing, exposure control processing, and feature amount extraction processing. However, the light modulation image generation processing and the region extraction processing are already well-known techniques as described in Patent Document 1, and thus detailed description thereof is omitted.

  The template matching processing unit 5 collates the feature amount extracted by the feature amount extraction process of the arithmetic processing unit 4 with the template registered (stored) in the memory unit 6 in advance, so that a person in the target space can be identified. It is determined whether or not the person is registered in advance (in this embodiment, a resident of an apartment house). Then, the processing result by the template matching processing unit 5, that is, the authentication result (authentication enabled or disabled) is transmitted to the system control board G.

  If the authentication result received from the imaging device A is authentic, the system control panel G causes the electric lock control panel D to unlock the electric lock, causes the elevator control panel E to operate the elevator, and further delivers the delivery box control panel F. Unlock the delivery box. On the other hand, if the authentication result received from the imaging device A cannot be authenticated, the system control panel G performs no control on the electric lock control panel D, the elevator control panel E, and the delivery box control panel F. Therefore, it is possible to prevent an unregistered person (a person other than the resident of the apartment house) from entering the apartment house without permission.

  Next, the operation (particularly the exposure control process) of the arithmetic processing unit 4 will be described in more detail.

  The arithmetic processing unit 4 controls the light emission control unit 2 to uniformly irradiate the entire target space with the modulated light. At this time, it is desirable to reduce the power consumption of the light emitting unit 1 by, for example, thinning out every other light emitting diode 1a of the light emitting unit 1 instead of lighting it. From the light modulation image thus obtained, the arithmetic processing unit 4 extracts a face region by performing region extraction processing. However, when the pixel value of the light modulation image is reduced by thinning the light emitting unit 1 and the face region extraction by the region extraction processing fails, the arithmetic processing unit 4 increases the light emission amount of the light emitting unit 1. Then, the light modulation image is acquired again, and the region extraction process is performed again on the light modulation image.

  The arithmetic processing unit 4 determines the subject (person's face) X based on the position of the face region (pixel coordinates) extracted by the region extraction processing and the distance to the subject X estimated from the size of the face region. One to a plurality of light emitting diodes 1a are selected from the range in which the distances are relatively closest. For example, as shown in FIG. 2A, if the subject X is on the right side of the center in the angle of view and the distance from the imaging device A is relatively far, a plurality of light emitting diodes 1a on the right side of the light emitting unit 1 are connected. select. Further, as shown in FIG. 2B, if the subject X is on the right side of the center in the angle of view and the distance from the imaging device A is relatively close, the right light emitting diode 1a in the light emitting unit 1 is connected. select. Then, the arithmetic processing unit 4 controls the light emission control unit 2 so that only the selected one or more light emitting diodes 1a are lit. 2 is an overhead view of the light emitting unit 1 and the subject X, and the light emitting diode 1a that emits light when selected is indicated by a broken line.

  Thus, when the arithmetic processing unit 4 performs the exposure control processing as described above, the modulated light is emitted from the light emitting unit 1 only to a narrow region including the face of the person in the target space. Is adjusted to a level corresponding to the distance to the person's face (for example, if the distance is double, the light amount is increased four times), the pixel value of the light modulation image is set to an appropriate value (feature amount). A value within an appropriate range suitable for extraction). In addition, since the intensity (light quantity) of the modulated light applied to the subject (person's face) X is greater than that during thinning lighting, the signal-to-noise ratio (( There is also an advantage that the (S / N ratio) can be improved. And if the light modulation image acquired in this way is used, the authentication accuracy in the subsequent authentication process can be improved. In the above example, the light quantity of the light emitting unit 1 is adjusted by increasing / decreasing the number of light emitting diodes 1a according to the size of the face area (distance to the subject X). In addition, the light amount of the light emitting unit 1 may be adjusted by increasing or decreasing the current value flowing through the same number of light emitting diodes 1a. Further, instead of arranging the light emitting diodes on the same plane to form the light emitting unit 1, for example, the light emitting unit 1 is arranged by arranging a plurality of light emitting diodes on a curved surface (such as a spherical surface or a cylindrical surface) that is convex toward the target space. May be configured.

  Here, it is not always necessary that all the light emitting diodes 1a constituting the light emitting unit 1 have the same directivity. For example, the light emitting unit 1 is configured by alternately arranging a light emitting diode 1b having a relatively low directivity and a light emitting diode 1c having a relatively high directivity. It is also possible (see FIG. 3). In this case, as shown in FIG. 3A, the arithmetic processing unit 4 extracts a face area from a light modulation image obtained by emitting only the low directivity light emitting diode 1b, and then the position and size of the face area. Based on the above, only the highly directional light-emitting diode 1c having the closest distance to the subject X as shown in FIG. Thus, if the subject X is irradiated with the modulated light emitted from the highly directional light-emitting diode 1c, the light emitted from the light-emitting unit 1 is compared with the case where the subject X is irradiated with the modulated light emitted from the low-directional light-emitting diode 1b. Even if the power consumption is the same, the amount of light applied to the subject X increases, so the S / N ratio of the light-modulated image can be improved without increasing the power consumption.

  Incidentally, the video processing unit 4 can also extract a plurality of face regions from one (one frame) light modulation image. For example, as shown in the overhead view of FIG. 4A, when two subjects X1 and X2 are present in the target space at the same time, a light modulation image acquired by first emitting only the low-directional light emitting diode 1b. From each of the subjects X1 and X2, and based on the position and size of each of the face regions, as shown in FIG. 4B, a highly directional light emitting diode having the closest distance to the subjects X1 and X2 Only 1c needs to emit light. However, the highly directional light emitting diodes 1c corresponding to the subjects X1 and X2 may emit light at the same time, or may emit light one by one in order. Further, in consideration of the case where the subjects X1 and X2 move as shown in FIG. 4C, only the low-directional light emitting diode 1b is caused to emit light again and the position and size of the face area of each subject X1 and X2. And the light emitting diode 1c having the highest directivity closest to the distance may be selectively emitted following the moved subjects X1 and X2 (see FIG. 4D).

  Here, in the light modulation image generation processing of the arithmetic processing unit 4, if a light modulation image is generated by integrating a plurality of temporally continuous (multiple frames) light modulation images, it is included in each light modulation image. It is possible to obtain a light modulation image having a high signal-to-noise ratio by attenuating random noise components. At this time, when the subject (person) can be considered to be stationary, the entire light-modulated image of a plurality of frames can be simply integrated (frame integration) as it is, but when the subject is moving, the frame is simply When integrated, not only the noise component but also the pixel value of the face region is attenuated. Therefore, when extracting a face region from a plurality of temporally continuous light-modulated images, the motion of the face region (moves) using a motion prediction method in an image compression technique standardized by MPEG4 or the like. A prediction process for predicting (direction and moving distance) is executed by the arithmetic processing unit 4, and for example, as shown in FIG. 5A, the face region Y1 extracted in the frame m-1 is moved in the next frame m. Predict the distance traveled. Then, the arithmetic processing unit 4 controls the light emission control unit 2 to irradiate the modulated light to the predicted position of the face area Y2 in the next frame m and further to the position of the face area Y3 in the next frame m + 1. By combining the prediction process and the exposure control process in this way, the pixel value of the light modulation image can be set to an appropriate value even when an area (face area) having a specific feature moves.

  Further, if the light-modulated image of each frame m-1, m, m + 1 is frame-integrated so that the face regions Y1, Y2, Y3 predicted as described above are overlapped, even when the face region moves, A random noise component included in each light modulation image can be attenuated to obtain a light modulation image with a high signal-to-noise ratio.

  By the way, in the present embodiment, the human face area is exemplified as the area having the specific feature extracted from the light modulation image, but the feature area is not limited to the face area. For example, not only a person's face but also a moving object may be extracted as a feature region. Or you may extract the area | region drawn with the character or the specific pattern like the automobile registration number mark (number plate) attached to the motor vehicle as a feature area. For example, if a license plate is used as a feature area, characters and symbols written on the license plate are extracted as feature quantities, and the license plate is matched with a car registration number template registered in advance. It is possible to apply the present invention to a parking gate control system that authenticates the attached vehicle and automatically opens the parking gate when it is determined that authentication is possible.

1 shows an embodiment of the present invention, (a) is an overall block diagram, and (b) is a schematic configuration diagram of a light emitting unit. (A), (b) is explanatory drawing of the exposure control processing in the same as the above. (A), (b) is explanatory drawing of the exposure control processing in the same as the above. (A)-(d) is explanatory drawing of the exposure control processing in the same as the above. (A), (b) is explanatory drawing of the exposure control processing in the same as the above. It is a system configuration figure of the security system for apartment houses using the same.

Explanation of symbols

A Imaging device 1 Light emitting part (modulated light irradiation means)
2 Light emission control unit (modulated light irradiation means)
3 imaging unit 4 arithmetic processing unit (light modulation image generation unit, region extraction unit, exposure control unit)

Claims (8)

Modulated light irradiation means for irradiating the target space with modulated light, an image sensor that receives light incident from the target space, and a signal output from each pixel of the image sensor to process only the reflected light component of the modulated light A light modulation image generation unit that generates a light modulation image having a pixel value as a pixel value, a region extraction unit that extracts a region having a specific feature from the light modulation image generated by the light modulation image generation unit, and a region extraction unit Exposure control means for adjusting the modulated light by controlling the modulated light irradiation means so that the pixel value of the extracted region falls within a predetermined appropriate range,
The modulated light irradiation means has a plurality of light sources that irradiate light to different positions in the target space, and the exposure control means has a plurality of light sources according to the position and size of the area extracted by the area extraction means. An image pickup apparatus that adjusts at least one of turning on / off and light emission amount.   The modulated light irradiating means has a plurality of types of light sources that are different from each other in at least one of the irradiation range and the light emission amount, and the exposure control means corresponds to the positions and sizes of the plurality of areas extracted by the area extracting means. The image pickup apparatus according to claim 1, wherein at least one of turning on / off of a plurality of types of light sources and light emission amount is adjusted.   When the region having a specific feature is moving, the region is provided with a predicting unit that predicts a moving direction and a distance of the region, and the exposure control unit moves and moves the region predicted by the predicting unit. The imaging apparatus according to claim 1, wherein at least one of turning on and off of the plurality of light sources and the amount of emitted light is adjusted according to the distance.   The imaging apparatus according to claim 1, wherein the area extraction unit extracts a human face as an area having a specific feature.   The imaging apparatus according to claim 1, wherein the area extraction unit extracts an area drawn with a character or a specific pattern as an area having a specific feature.   The imaging apparatus according to claim 1, wherein the area extracting unit extracts a moving area as an area having a specific feature.   The imaging apparatus according to claim 1, wherein the light modulation image generation unit integrates a plurality of time-sequential light modulation images.   The area extracting means extracts a moving area as an area having a specific feature, and the light modulation image generating means integrates a plurality of temporally continuous light modulation images so that the areas overlap. The imaging apparatus according to claim 7, characterized in that:

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