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WO2008155771A2 - Système de projection d'image avec rétroaction - Google Patents

Système de projection d'image avec rétroaction Download PDF

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Publication number
WO2008155771A2
WO2008155771A2 PCT/IL2008/000839 IL2008000839W WO2008155771A2 WO 2008155771 A2 WO2008155771 A2 WO 2008155771A2 IL 2008000839 W IL2008000839 W IL 2008000839W WO 2008155771 A2 WO2008155771 A2 WO 2008155771A2
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WO
WIPO (PCT)
Prior art keywords
image
display surface
sensor
operative
sensor output
Prior art date
Application number
PCT/IL2008/000839
Other languages
English (en)
Other versions
WO2008155771A3 (fr
Inventor
Elon Littwitz
Raviv Erlich
Matan Naftali
Adi Baram
Original Assignee
Maradin Technologies Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maradin Technologies Ltd. filed Critical Maradin Technologies Ltd.
Publication of WO2008155771A2 publication Critical patent/WO2008155771A2/fr
Publication of WO2008155771A3 publication Critical patent/WO2008155771A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3191—Testing thereof
    • H04N9/3194—Testing thereof including sensor feedback
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen

Definitions

  • the present invention relates generally to image display devices and more particularly to image projectors.
  • Scalable Display Technology's Multi-Projector System is a technology for narrow, high-aspect-ratio images as well as cylindrical and spherical surfaces.
  • the system claims to program as many as four projectors with a single computer, and to link multiple computers to control systems that require more projectors.
  • the Multi- Projector System is said to consist of calibration software, video player software, and a graphical user interface.
  • the company website illustrates the system, including N projectors trained on a display screen, a camera imaging the display screen, and a personal computer associated with the camera and the projectors.
  • Certain embodiments of the present invention pertain to display projection of data, images, videos etc. and include quality feedback and eye-safe mechanisms for display projection systems.
  • Such mechanisms typically facilitate use of the projector by the user without requiring any manual adjustment of the projector and the projecting screen.
  • This typically includes usage of portable projection systems, which may operate in changeable environments and conditions such that adjustment of the projection system to the surroundings each time the projector is used, is advantageous.
  • Certain embodiments of the present invention allow all further adjustments to be done internally by means of image acquisition and image processing, to bring the picture into the desired form.
  • the above is also typically applied for aspects of eye-safety.
  • the system seeks to prevent risk to the user's eyes, and hence a mechanism is provided that reduces light power, when an object (e.g., a human eye) is located adjacent to the projector.
  • a system and method for providing an image quality feedback mechanism for display projection systems comprising a display projection system, an image sensor (such as CCD 5 CMOS 5 IR image sensor, proximity sensor, etc.) and a CPU for image processing.
  • an image sensor such as CCD 5 CMOS 5 IR image sensor, proximity sensor, etc.
  • a CPU for image processing.
  • Certain embodiments of the present invention seek to provide image quality and eye safety mechanisms for display projection systems.
  • the display projection system projects its image onto a target screen.
  • the screen may be either a standard white sheet, or any other shape including a white wall, colored wall, wall with pictures, granulated wall, rounded wall etc.
  • the system is able to collect images and power from the target, to compare this to the source image and source power and to make adjustments which facilitate a clearer image for the human eye.
  • the device is able to respond to changes in a room's internal lightning and to adjust its contrast and brightness as a result of light changes such as dimming lights, opening curtains etc.
  • the projector is able to focus itself by feedback from the collected CCD images, and by contour adjustment.
  • the image sensor typically detects the output image, compares it to the source, and corrects the output by meaning of image processing, so that the human eye sees a corrected image.
  • a method of providing an eye-safety mechanism may also be implemented by adding a proximity sensor or other image sensor in conjunction with the system shown and described above or by itself in conjunction with a CPU.
  • the device may be activated only when no objects are near its front projecting unit, within a predefined distance and or view angles thereof. Hence, when a human enters the field of projection of the device, the system automatically decreases its output light power.
  • a quality image feedback mechanism embedded in a display projector typically including an image sensor (for example, CCD, CMOS, IR image sensor, etc.) and a CPU for image processing and quality feedback.
  • This device may be used for geometry and aspect ratio corrections due to different projection angles, and/or for correction of image distortion due to difference target screen surfaces, and/or for correction of image colors due to different target screen colors and patterns, and/or for adjustment of contrast and brightness according to a room's lighting.
  • an eye safety device including a proximity sensor (such as a photo diode, a CCD, CMOS, IR sensor) and a processing unit (typically a CPU).
  • the device may be used to reduce or even shut down, output light power in order to avoid damage to a human eye by detecting a close object located in front of the field of projection, and/or to alert as to any close objects located in front of the field of projection, and/or to stop or pause a presentation, or a movie or any other media when a close object such as a waving hand is detected in front of the projection unit, and/or to mark the location of a movie or presentation or any other media when a close object such as a waving hand is detected in front of the projection unit, and/or as a safety mechanism for light projection, typically such that when the proximity sensor is not operated, no light power is projected from the projection system.
  • an image display system comprising an image projector operative to receive image content and to project, accordingly, an output image onto a display surface; a sensor (such as but not limited to a photo diode, CCD, CMOS, IR sensor, proximity sensor or cellphone camera) generating a sensor output pertinent to operation of the image projector, thereby to generate a sensor output; and an image projector feedback unit operative to provide at least one control signal to the image projector, responsive to the sensor output.
  • a sensor such as but not limited to a photo diode, CCD, CMOS, IR sensor, proximity sensor or cellphone camera
  • the senor comprises a camera imaging at least a portion of the display surface.
  • the image projector projects a light beam toward the display surface thereby to define a light path and the camera's field of view includes a vicinity of the light path.
  • the image projector feedback unit includes an object identifier using the sensor output to identify objects which are at least close to the light path and operative to interrupt the image projector's projection of the output image onto the display surface if the objects are identified.
  • the image projector feedback unit includes a display surface characterizer using the camera output to characterize at least one characteristic of the display surface.
  • the image projector feedback unit is operative to generate the output image by modifying the image content to take into account the at least one characteristic of the display surface such that the output image, when projected onto the display surface, resembles the image content more closely than a projected image generated by projecting the image content onto the display surface would resemble the image content.
  • the at least one characteristic includes at least one characteristic of the display surface's color.
  • the image content comprises a colored image to be displayed and wherein the at least one characteristic of the display surface's color comprises a colored image of the display surface and wherein the output image is computed by subtracting the colored image of the display surface from the colored image to be displayed.
  • the image projector projects a light beam having an intensity toward the display surface and wherein the image projector feedback unit includes an object identifier using the sensor output to identify objects which are at least close to the light path and operative to reduce the intensity of the light beam if the objects are identified.
  • the sensor output is operative to generate an indication of stability of the sensor relative to the display surface and wherein the number of outputs the sensor generates per time unit depends on the indication of stability.
  • the at least one characteristic includes at least one characteristic of the display surface's contour.
  • a safe illumination system comprising a light source operative to provide illumination of a target area in which illumination is hazardous if impinging on a human being for a certain time period, a human presence sensor sensing events related to human presence in at least a portion of the target area, thereby to generate a sensor output indicative of a human presence and a light source control unit operative to at least reduce the illumination in the portion of the target area, responsive to the sensor output.
  • the light source comprises a laser or LED. Still further in accordance with at least one embodiment of the present invention, the light source control unit is operative to terminate the illumination in the portion of the target area, responsive to the sensor output.
  • the light source control unit is operative to restore the illumination responsive to a subsequent sensor output indicative of termination of the human presence.
  • the senor comprises a temperature difference detector. Further in accordance with at least one embodiment of the present invention, the sensor comprises an image capturing device oriented to capture an image of at least a portion of the target area.
  • the image content has a dynamic range and wherein the feedback unit is operative to reduce the dynamic range of at least some of the image content.
  • the senor comprises a motion detector operative to identify objects which are at least close to the light path. Further in accordance with at least one embodiment of the present invention, the sensor comprises a volume detector operative to identify objects which are at least close to the light path.
  • the senor comprises an IR detector operative to identify objects which are at least close to the light path.
  • the senor comprises a proximity sensor (such as but not limited to a photo diode, CCD, CMOS, IR sensor, or cell phone camera) operative to identify objects which are at least close to the light path.
  • a proximity sensor such as but not limited to a photo diode, CCD, CMOS, IR sensor, or cell phone camera
  • the camera's field of view includes the output image.
  • an image displaying method comprising receiving image content and projecting, accordingly, an output image onto a display surface, generating a sensor output pertinent to the projecting, thereby to generate a sensor output, and providing at least one control signal to control the projecting, responsive to the sensor output.
  • a safe illumination method comprising providing illumination of a target area, in which illumination is hazardous if impinging on a human being for a certain time period, sensing events related to human presence in at least a portion of the target area, thereby to generate a sensor output indicative of a human presence; and at least reducing the illumination in the portion of the target area, responsive to the sensor output.
  • the sensor comprises a cell phone camera.
  • the cell phone camera is positioned and oriented to perform at least one of the following: (a) identify objects which are at least close to said light path; and (b) capture an image of at least a portion of said display surface.
  • a method for generating an image displaying system comprising providing a mobile communication device including a cell phone camera and a mobile image projector, the mobile image projector being operative to receive image content and to project, accordingly, an output image onto a display surface, thereby to define a light path, the cell phone camera being operative to generate a sensor output pertinent to operation of the image projector, thereby to generate a sensor output; and providing an image projector feedback unit operative to provide at least one control signal to said image projector, responsive to said sensor output.
  • processors Any suitable processor, display and input means may be used to process, display, store and accept information, including computer programs, in accordance with some or all of the teachings of the present invention, such as but not limited to a conventional personal computer processor, workstation or other programmable device or computer or electronic computing device, either general-purpose or specifically constructed, for processing; a display screen and/or printer and/or speaker for displaying; machine-readable memory such as optical disks, CDROMs, magnetic- optical discs or other discs; RAMs, ROMs, EPROMs, EEPROMs, magnetic or optical or other cards, for storing, and keyboard or mouse for accepting.
  • the term "process” as used above is intended to include any type of computation or manipulation or transformation of data represented as physical, e.g. electronic, phenomena which may occur or reside e.g. within registers and /or memories of a computer.
  • the above devices may communicate via any conventional wired or wireless digital communication means, e.g. via a wired or cellular telephone network or a computer network such as the Internet.
  • the apparatus of the present invention may include, according to certain embodiments of the invention, machine readable memory containing or otherwise storing a program of instructions which, when executed by the machine, implements some or all of the apparatus, methods, features and functionalities of the invention shown and described herein.
  • the apparatus of the present invention may include, according to certain embodiments of the invention, a program as above which may be written in any conventional programming language, and optionally a machine for executing the program such as but not limited to a general purpose computer which may optionally be configured or activated in accordance with the teachings of the present invention.
  • sociating refers to the action and/or processes of a computer or computing system, or processor or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories, into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.
  • Figs. IA and IB 5 taken together, form a pictorial illustration of geometry correction effected by an image projection device to compensate for a particular geometry of a display surface;
  • Figs. 2A and 2B taken together, form a pictorial illustration of color correction effected by an image projection device to compensate for a particular colored pattern (shown in black and white for simplicity) appearing on a display surface;
  • Fig. 3A is a pictorial illustration of an undistorted rectangular grid
  • Fig. 3B is a barrel distortion of the grid of Fig. 3 A;
  • Fig. 3C is a pincushion distortion of the grid of Fig. 3 A;
  • Fig. 4 A is a simplified diagram of a Laser beam projection geometry
  • Fig. 4B is a table of example Laser beam specification parameters.
  • Fig. 4C is a table of AEL Class 1 photochemical and photo-thermal powers for different wavelengths
  • Fig. 5 is a screenshot of a Laser beam footprint located 100 mm distant from the exit of the laser
  • Fig. 6 is a table of real space X and Y coordinates, and MEMS X and Y angles, for 9 different positions;
  • Fig. 7 is a footprint diagram of a footprint useful in certain embodiments of the present invention.
  • Fig. 8 is a simplified functional block diagram illustration of an image projection system with feedback, constructed and operative in accordance with certain embodiments of the present invention.
  • Figs. 9A - 9C are pictorial illustrations of an example of a use of the apparatus of Fig. 8 in which a human being enters the scene, at which point of projection (Fig. 9A) the human being remains within the scene (Fig. 9B) such that restoration of the light beam remains inadvisable, and eventually (Fig. 9C), the human being departs, the light beam can safely be restored, and projection of the image is renewed.
  • Figs. 1OA — 1OC are pictorial illustrations comparing use and failure to use the apparatus of Fig. 8, including Fig. 1OA illustrating a color texture on a wall, Fig. 1OB in which the apparatus of Fig.
  • Fig. 1OC in which the apparatus of Fig. 8 is used for color correction thereby to eliminate the inconvenient superposition of the color texture on the image to be projected shown in Fig. 1OB;
  • Fig. 1OD is a key for Figs. 1OA - 1OC showing that two kinds of hatching represent light blue and light green respectively.
  • Figs. IA and IB taken together, form a pictorial illustration of geometry correction effected by an image projection device 10 to compensate for a particular geometry of a display surface.
  • Figs. 2 A and 2B taken together, form a pictorial illustration of color correction effected by an image projection device 210 to compensate for a particular colored pattern 220 (shown in black and white for simplicity) appearing on a display surface.
  • An eye safety mechanism is provided in accordance with certain embodiments of the present invention, the mechanism typically including a feedback control mechanism that reduces light radiation power in the event that an object passes closely to the light source aperture in a way that may cause damage to a human eye, according to regulations.
  • the eye-safety mechanism typically comprises: (1) a light source such as LED or laser diode; (2) a sensor (e.g., CCD, Photo-diode, CMOS imager, cell phone camera, etc.), to determine the proximity of a passing object to the light source emitter; and (3) a processing unit to process control regime and to order the reduction of light power.
  • Applicable regulations and documents may for example include the IEC60825-1: 1994 and updates including Al: 1997 + A2:2001.
  • To construct an eye-safety mechanism such as that described above, some or all of the following steps may be performed, in any suitable order e.g. as follows: a. Determine suitable wavelengths for the light sources. b.
  • a light source such as LED or laser diode
  • a sensor e.g., CCD, Photo- diode, CMOS imager, cell phone camera, etc.
  • a processing unit to process control regime and to order the reduction of light power, taking into consideration the response time of the system (sensors, CPU etc.).
  • a Picture Dynamic Quality Mechanism is provided which is similar to the eye-safety mechanism described above.
  • the sensor of the system is typically capable of discerning the projected picture state, including information characterizing the projected picture's brightness, distortions, and/or key stoning.
  • picture quality may be improved in real time by controlling certain parameters that affect its state, such as but not limited to light source power, projected field of view corrections, and pincushion corrections.
  • Applications include but are not limited to portable projectors, angled projection situations, and front projection systems.
  • Figs. 3A - 3C are prior art illustrations of possible distortions of the display surface which may be compensated for using certain embodiments of the present invention.
  • An image display generation method constructed and operative in accordance with certain embodiments of the present invention may include some or all of the following steps, in any suitable order e.g. as follows: a. Providing an image projection system with a CCD or CMOS imager. b. Comparing collected data, representing desired data projected onto an individual display surface, to the desired data itself. c. Determining changes to be effected in the desired data before it is projected, such as but not limited to corrections of power, field of projection, distortions; and d. Command controllers regarding the changes computed in step c, and rechecking quality EXAMPLE:
  • a pocketsize projector may be provided, with RGB laser sources.
  • the three sources are scanned to present, at a screen located 100 cm ahead, a footprint of 408x307 mm dimensions, projected at 23x17.4 degrees.
  • Fig. 4A illustrates an example laser beam projection system geometry, including a laser source 410, an aperture 420 and a screen or other display area 430.
  • Fig. 4B presents an example of laser beam specifications, hi the illustrated example, the vertical scanning reaches a 7 mm dimension, which is the pupil's maximal size, at a distance of 17.2 mm from the laser exit.
  • the projector is based on scanning beams, a 7 mm aperture which is representative of the eye pupil diameter is placed up to 17.2 mm from the laser exit and is continuously exposed to the laser beams. Therefore, a continuous exposure scenario is evaluated, e.g. according to IEC60825-1: 1994 + Al:1997 + A2:2001.
  • the AEL Class 1 is determined for the given laser beams. For two wavelengths (455 and 532 nm) dual AEL class 1 (for thermal and photochemical hazards) may be evaluated, where the most restrictive case is taken.
  • the following parameters may be determined, e.g. as follows:
  • the time base is 100 seconds.
  • the angle ⁇ is a function of the distance: for each distance, ⁇ is determined to be the lowest of the angular substance by the projection lens (1/D, where D given in mm units) and the beam divergence (that is 0.5 mR, but any angle less than 1.5 mR is taken as 1.5 mR).
  • ⁇ is determined to be the lowest of the angular substance by the projection lens (1/D, where D given in mm units) and the beam divergence (that is 0.5 mR, but any angle less than 1.5 mR is taken as 1.5 mR).
  • T 2 10xl0 [( ⁇ - ⁇ l)/98 - 5]
  • ⁇ 1.5 mR
  • T 2 IO s
  • C 3 may be determined for 460 and 532 nm.
  • C 3 is computed using the following equation:
  • Fig. 4C presents formulae to compute the photochemical and photo-thermal AEL class 1, including the values accepted for each wavelength.
  • the photochemical limit is the most restrictive case for 460 nm while for 532 nm and 635 nm the photo-thermal limit is the most restrictive case.
  • the power through a 7 mm aperture placed at 14 mm distance from the laser exit is typically lower than the AEL class 1 values presented in the table of Fig. 4B.
  • the power of the three wavelengths typically fulfills the following equation:
  • Pl, P2 and P3 being as defined in Fig. 4B as the power (in W units) of 460, 532 and 635 nm respectively.
  • Equation 6 shows that the permitted power for 460 nm may be 40 ⁇ W maximum, and the power for 532 nm and 635 nm may be 50 ⁇ W each. These power levels seem to be too low to suit the projector's needs, hence the criteria for class IM may be examined.
  • the power through a 7 mm aperture placed at 100 mm distance from the laser exit is typically lower than the AEL class 1 values presented in the table of Fig. 4C.
  • Fig. 5 illustrates the footprint of the scanned beam at 100 mm distance from the laser exit, with a 7 mm aperture at the center of this footprint.
  • the proportion of the power passing through the 7 mm aperture (Pa) is exactly the proportion of the aperture area from the total laser beam footprint area, namely:
  • the laser beam power for class IM may be 33 times greater than the power accounted for Class 1.
  • the following power levels are permitted:
  • APR automatic power reduction
  • the total power (P1+P2+P3) may be 36 mW.
  • the total power (P1+P2+P3) may be 36 mW.
  • (P1+P2+P3) may be 43 mW.
  • the total power (P1+P2+P3) may be 63 mW.
  • the table of Fig. 6 sets forth actual MEMS angles for an example projector system such as that described above.
  • the footprint diagram of Fig. 7 illustrates all 9 points at the screen surface.
  • the rectangular boundary, 370 mm x 280 mm, is larger than the optical boundary of 360 mm x 270mm.
  • Fig. 8 is a simplified functional block diagram illustration of an image projection system with feedback, constructed and operative in accordance with certain embodiments of the present invention.
  • an image projector 810 receives image content 815 to be projected on a display surface 820 which may be colored and may also be other than smooth.
  • the image projector generates a beam which in turn generates a projected image on the display surface 820.
  • at least one feedback sensor 830 which may, for example, comprise a camera whose field of view includes display surface 820 and/or includes the entire beam generated by the image projector.
  • the feedback sensor 830 may alternatively or in addition include an apparatus for sensing human presence other than a camera.
  • the feedback generated by the sensor 830 is provided to a feedback based projector controller 840 which is operative to control at least one aspect of the operation of the image projector 810.
  • controller 840 may generate control signals which are operative e.g. for reducing or interrupting the beam generated by the image projector 810, responsive to object detection in the beam's vicinity.
  • the controller 840 may modify the image content (the color thereof &/or geometry thereof &/or other), responsive to display surface characteristics sensed by feedback sensor 830.
  • the eye is sensitive to high intensity light radiation.
  • the user might inadvertently locate Ms eye in front of high intensity light emitted from the projector, and damage his/her eyes. This is even worse if the projector generates a laser beam but nonetheless, current regulations for laser apparatus only require placing a warning label on the device.
  • the projection system 810 of Fig. 8 typically projects an image/movie on a target. It polls its sensor/s 830 and analyses incoming data. As soon as it recognizes an object entering the scene of the projection, it stops projection.
  • the sensor/s 830 may for example include one or more of a volume detector, an Infra Red diode, a CCD detector, a CMOS detector and a cell phone camera.
  • the volume detector and IR diode typically produce an indicative signal responsive to detection, in their field of view, of heat of a live body, human or animal. Recognition is typically achieved by detecting a heat difference between the body and the environment.
  • CCD and CMOS sensors and cell phone cameras typically capture an image projected on the target.
  • These sensors know which kind of image may be projected and are operative, using conventional image processing techniques, to recognize whether an object is located in front of the projector or not.
  • These sensors carry out more processing than the heat difference detectors do, however, they have the advantage of being able to simultaneously support various embodiments of the present invention such as the safety stop-and-replay embodiment shown and described herein, together with the embodiment in which image content is pre-processed before being projected, to take into account color and/or contour characteristics of the display area.
  • Figs. 9A — 9C are pictorial illustrations of an example of a use of the apparatus of Fig.
  • a human being enters the scene, at which point of projection (Fig. 9A), the human being remains within the scene (Fig. 9B) such that restoration of the light beam remains inadvisable, and eventually (Fig. 9C), the human being departs, the light beam can safely be restored, and projection of the image is renewed.
  • the projection system is switched on.
  • its IR sensor say
  • the projection is switched off, and light intensity decreases.
  • the detector typically responds within 10-100 ms, according to the emitted light radiation intensity.
  • the power to the laser source is immediately shut down
  • CMOS/cell phone camera sensor When a CCD/CMOS/cell phone camera sensor is used, the sensor captures the image. When there is an above-threshold difference between a previous original image and the captured one, this indicates that there is some kind of interference in the picture. Capturing another image allows the system to determine if this a constant interference, such as a picture on the wall, or whether it is a human being (who is seen to be moving). Alternatively or in addition, motion detection may be used. An image stabilization algorithm may facilitate recognition of a human being.
  • a "stop- and-auto replay when intruder is gone" feature may be provided. For example, an image projection system enables children to watch a movie on the living room's wall.
  • Fig. 8 Another application of the feedback loop of Fig. 8 is color correction as described herein, e.g. as per the example shown in Figs. 1OA — 1OC.
  • the projection target (display area) is a plain white screen or wall.
  • the display area may be colored, or a wall with a picture or other object mounted thereupon, or a texture.
  • Image feedback and correction are useful in facilitating image projection under these conditions.
  • the projector may add 156,0,0 to create the effect of a complete blue, in the area of the rectangle, and an additional 256,0,0 for the rest. This causes the rectangular texture of the screen to be faint.
  • the projector uses a feedback from a camera, such as a CCD or CMOS camera, that captures the screen.
  • a camera such as a CCD or CMOS camera
  • FIGs. 1OA - 1OC show how an image of a flower 1010 can be projected onto a light blue wall 1020 with a light green spot 1030 shown in Fig. 1OA, either without recourse to the invention shown and described herein as shown in Fig. 1OB, or with recourse to certain embodiments of the invention shown and described herein as shown in Fig. 1OC, as a result of which the inconvenient green spot 1030 fades or even disappears.
  • the image processing unit may for example compute the difference between the image stored on the memory of the projector and the captured output. By subtracting the difference, and optionally taking into account known eye sensitivity curves for difference light frequencies, color correction is effected in the image content before projection.
  • the entire dynamic range of the projected image may be reduced into a smaller set, that starts with a different DC level.
  • RGB complete 8 bits x 3 representation
  • the projector would now use a DC of only 0,0,30, to complete the color distortion, and re-scale the image into the range of 0-245-50, i.e. 0-206 (or 0-128). It is appreciated that even 6 bits (i.e. 0-64) is sufficient for the human eye to adequately perceive color.
  • Another application of the apparatus of Fig. 8 is correction of image geometry to compensate for geometry of the display area.
  • the projector may be placed on a surface disposed at an angle to the projected screen.
  • the result is that a rectangular image results in a projected trapezoid 20 (Fig. IA) rather than the original rectangle (Fig. IB).
  • the feedback received from the captured image may be used, as shown in Figs. IA - IB, to appropriately correct the geometry of the image content, by reducing and enlarging the projecting angles, by changing mirror scanning angles, reducing and enlarging spacing between pixels emitted to screen and/or by any other suitable geometry modification method.
  • An optional power saving mode is provided, for any suitable one of the embodiments shown and described herein. This mode saves power by reducing feedback frequency and hence performing correction computations at lower rates. For example, if a projection system is placed in front of a constant wall with a texture, in order to display a 1.5 hours movie, the target screen does not change and hence computations of color correction and geometry correction may be performed as infrequently as only once, or perhaps only a few times in the course of 1.5 hours. Therefore, the projector optionally traces sensed changes, assumes that the situation is stationary and steady when appropriate, and reduces the sensor's capturing frequency and color correction as well as geometry computation rates. For example, the feedback loop might initially occur for each frame.
  • the feedback loop may be actuated by the low power functionality only each 10 frames. If no change is detected for an even longer period, the feedback loop may be actuated by the low power functionality only each 10 frames (e.g., 1 second @ 30fps), and eventually even only once a minute. Conversely, the feedback rate may be increased. For example, when the projector is held by a human hand, there is a high probability that the human being is not stable, and hence when this situation is detected by suitable means, feedback is typically performed at a high rate, perhaps even for each and every frame. In this case, the projector may also implement a suitable image stabilization process to correct for vertical and horizontal human vibration. This embodiment is also useful for other geometric corrections.
  • a single image projection system such as that shown and described in Fig. 8, may be constructed and operative to simultaneously provide eye safety, and both color correction and geometry correction in accordance with display surface characteristics.
  • Any of the image projection systems shown and described herein may be portable and may, for example, be integrated into a mobile communication system such as a cell phone.
  • any of the image display systems shown and described herein may use camera output to characterize at least one characteristic (typically color and/or contour) of the display surface and may then modify the image content which is projected to take into account that characteristic such that the output image, when projected onto the display surface, resembles the image content.
  • This process may make any suitable underlying assumptions, depending on the application, regarding the color or contour characteristics of the display surface and of the image content and regarding interactions therebetween. For example, the process may, but need not, assume additivity of the color contributions of the display surface and of the image content.
  • results may improve if it is not assumed, that (say) a 20 gray level image or pixel component projected onto an 80 gray level display surface appears the same as a 50 gray level image or pixel component projected onto an 50 gray level display surface or a 10 gray level image or pixel component projected onto an 90 gray level display surface.
  • the image or portions thereof to be projected is computed in accordance with the underlying assumptions. Similarly, linearity of the color components of the display surface and of the image content may or may not be assumed.
  • software components of the present invention including programs and data may, if desired, be implemented in ROM (read only memory) form including CD-ROMs, EPROMs and EEPROMs, or may be stored in any other suitable computer-readable medium such as but not limited to disks of various kinds, cards of various kinds and RAMs.
  • ROM read only memory
  • EEPROM electrically erasable programmable read-only memory
  • Components described herein as software may, alternatively, be implemented wholly or partly in hardware, if desired, using conventional techniques.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Projection Apparatus (AREA)
  • Transforming Electric Information Into Light Information (AREA)

Abstract

L'invention concerne un système d'affichage d'image comprenant un projecteur d'image conçu pour recevoir un contenu d'image et pour projeter, par conséquent, une image de sortie sur une surface d'affichage, un capteur générant une sortie de capteur qui est appropriée au fonctionnement du projecteur d'image pour générer ainsi une sortie de capteur; et une unité de rétroaction de projecteur d'image conçue pour commander le projecteur d'image en réponse à la sortie de capteur.
PCT/IL2008/000839 2007-06-21 2008-06-19 Système de projection d'image avec rétroaction WO2008155771A2 (fr)

Applications Claiming Priority (2)

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US94535807P 2007-06-21 2007-06-21
US60/945,358 2007-06-21

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WO2008155771A2 true WO2008155771A2 (fr) 2008-12-24
WO2008155771A3 WO2008155771A3 (fr) 2009-02-12

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101917631A (zh) * 2010-07-30 2010-12-15 浙江大学 一种在日常照明环境下的投影显示颜色再现方法
CN101959072A (zh) * 2010-07-30 2011-01-26 浙江大学 一种彩色表面投影显示颜色再现方法
EP2373039A3 (fr) * 2010-03-16 2012-03-21 Canon Kabushiki Kaisha Appareil de projection d'images de balayage
WO2013178213A3 (fr) * 2012-06-01 2014-01-23 Cornelius Heiko Procédé de correction automatique de reproduction d'un projecteur
US8665286B2 (en) 2010-08-12 2014-03-04 Telefonaktiebolaget Lm Ericsson (Publ) Composition of digital images for perceptibility thereof
WO2014063020A1 (fr) * 2012-10-18 2014-04-24 Chornenky T Eric Appareil et procédé de détermination d'informations spatiales concernant un environnement
CN112995627A (zh) * 2020-09-27 2021-06-18 深圳市当智科技有限公司 投影机安全工作方法和投影机

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19640404A1 (de) * 1996-09-30 1998-04-09 Ldt Gmbh & Co Vorrichtung zur Darstellung von Bildern
CN100449440C (zh) * 2003-02-03 2009-01-07 西门子公司 综合信息的投影
US6984039B2 (en) * 2003-12-01 2006-01-10 Eastman Kodak Company Laser projector having silhouette blanking for objects in the output light path
CN100505852C (zh) * 2004-09-21 2009-06-24 株式会社尼康 电子设备

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2373039A3 (fr) * 2010-03-16 2012-03-21 Canon Kabushiki Kaisha Appareil de projection d'images de balayage
US8358456B2 (en) 2010-03-16 2013-01-22 Canon Kabushiki Kaisha Scanning image projection apparatus
CN101917631A (zh) * 2010-07-30 2010-12-15 浙江大学 一种在日常照明环境下的投影显示颜色再现方法
CN101959072A (zh) * 2010-07-30 2011-01-26 浙江大学 一种彩色表面投影显示颜色再现方法
US8665286B2 (en) 2010-08-12 2014-03-04 Telefonaktiebolaget Lm Ericsson (Publ) Composition of digital images for perceptibility thereof
WO2013178213A3 (fr) * 2012-06-01 2014-01-23 Cornelius Heiko Procédé de correction automatique de reproduction d'un projecteur
WO2014063020A1 (fr) * 2012-10-18 2014-04-24 Chornenky T Eric Appareil et procédé de détermination d'informations spatiales concernant un environnement
CN112995627A (zh) * 2020-09-27 2021-06-18 深圳市当智科技有限公司 投影机安全工作方法和投影机
CN112995627B (zh) * 2020-09-27 2023-10-03 深圳市当智科技有限公司 投影机安全工作方法和投影机

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