JP5595063B2 - Image projection device and image display device - Google Patents

Description

  The present invention relates to an image projection apparatus and an image display apparatus, and more particularly to a projection-type image projection apparatus and an image display apparatus having an optical system for projecting light emitted from a light source onto a screen using a scanner. is there.

  Various types of image display devices have been developed as means for providing video to the user. For example, flat-screen televisions using liquid crystal or plasma as display devices are rapidly spreading with the momentum to drive out CRT (Cathode Ray Tube). Projection-type image display methods using so-called micro devices such as DMD (Digital Mirror Device (registered trademark)), HTPS (High Temperature Poly-Silicon), and LCOS (Liquid Crystal on Silicon) are known as data projectors and rear projections. Widely used as large-screen display devices such as type televisions.

  In addition to conventional cold cathode fluorescent lamps and high-pressure mercury lamps as light sources for liquid crystals and micro devices, LEDs (Light Emitting Diodes) and lasers have begun to be used to increase the color reproduction range and power consumption. Reduction is progressing.

  In addition to the advancement of MEMS (Micro Electro Mechanical System) technology, it has become possible to make a compact scanner device, and in addition, semiconductor lasers have been developed for all three primary colors. Image display devices are attracting attention.

  By the way, in an image display device using a laser, display of an image suitable for observation and safety of image display are required. For example, the scanning projector disclosed in Patent Document 1 directly blocks the generation of laser light when the laser light is not scanned normally.

Japanese Patent No. 4088188 (paragraphs 0005 to 0007, FIG. 1)

  However, the above-described conventional technique is a processing technique for a problem of a scanner, and cannot cope with a case where a defect occurs on the optical path and an image unsuitable for observation is displayed. For example, when a hole is formed in the screen, a video is partially lost in the front projection type image display device. Further, in the rear projection type image display device, in addition to the partial loss of an image, light passes through a hole in the screen depending on a location where a failure occurs. For this reason, there is a possibility that light that has not been diffused by the screen may directly enter the pupil of the observer for a long time. Further, even when light does not enter the pupil directly, there is a possibility that unpleasant reflected light may be generated at an unexpected place outside the screen such as a room wall.

  In addition, when an obstacle enters the optical path from the scanner to the screen, the image is partially lost in the front projection type and rear projection type image display devices. Furthermore, unpleasant reflected light on the obstacle surface may occur. As described above, in the above conventional technique, when a defect occurs on the optical path, partial omission of images, direct incidence of light on the pupil for a long time, generation of reflected light at an unexpected position, and the like occur. There was a problem that there was a case.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an image projection apparatus and an image display apparatus that quickly detect unintended light generated during image display and stop image display.

In order to solve the above-described problems and achieve the object, the present invention provides a light source in which the amount of emitted light in the visible light region is controlled by a light emission amount command value that is a light emission amount command value, and the light source Based on the optical scanning unit that scans and projects the light emitted from the screen, a plurality of light amount sensors that detect the light amount of light transmitted from the screen side as the received light amount, and the video signal input from the outside, A light emission amount command value generating unit that generates a command reference value used to generate the light emission amount command value; a light emission amount command value converting unit that generates the light emission amount command value based on the received light amount and the command reference value; An addition unit that adds the received light amounts detected by the plurality of light amount sensors and outputs the added received light amount to the emission amount command value conversion unit, and receives an instruction for the light source to emit light in case, the light emission quantity finger The value conversion unit compares a light amount ratio, which is a value obtained by dividing the added received light amount by the emitted light amount of the light emitted from the light source, with a preset threshold value, and the light amount ratio is greater than the threshold value. A light emission amount command value for stopping light from the light source when the light source is small is output to the light source.

  According to the present invention, it is possible to quickly detect unintended light generated during image display and to stop image display.

FIG. 1 is a block diagram showing a configuration example of an image projection apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram illustrating a configuration example of the light emission amount command value generation unit according to the first embodiment. FIG. 3 is a diagram illustrating an example of the relationship between the video signal IMG set in advance in the LUT and the reference light emission amount command value LA. FIG. 4 is a block diagram illustrating a configuration example of the light emission amount command value conversion unit. FIG. 5 is a diagram for explaining the amount of delay compensation in the delay compensator. FIG. 6 is a diagram for explaining an example of a relationship between an input signal and an output signal in the numerical comparison unit according to the first embodiment. FIG. 7 is a block diagram illustrating a configuration example of the command signal conversion unit according to the first embodiment. FIG. 8 is a diagram for explaining the operation of the zero gain holding unit. FIG. 9 is a block diagram illustrating a configuration example of the light source according to the first embodiment. FIG. 10 is a diagram for explaining the IP characteristic of the LD. FIG. 11 is a diagram illustrating a configuration example of a lens unit according to the first embodiment. FIG. 12 is a diagram illustrating a configuration example of the photosynthesis unit according to the first embodiment. FIG. 13 is a diagram for explaining an example of the operation of the scanner. FIG. 14 is a diagram for explaining another example of the operation of the scanner. FIG. 15 is a diagram illustrating an arrangement example of a front projection type image display device. FIG. 16 is a diagram illustrating an arrangement example of a rear projection type image display device. FIG. 17 is a block diagram illustrating a configuration example of the light amount sensor. FIG. 18 is a diagram illustrating an example of a transmittance curve of the bandpass filter according to the first embodiment. FIG. 19 is a block diagram illustrating a configuration example of the image projection apparatus according to the second embodiment. FIG. 20 is a perspective view illustrating an arrangement example of the scanner and the light amount sensor. FIG. 21 is a block diagram illustrating a configuration example of an image projection apparatus according to the third embodiment. FIG. 22 is a diagram illustrating a relationship example between an input signal and an output signal in the angle correction unit. FIG. 23 is a block diagram illustrating a configuration example of an image projection apparatus according to the fourth embodiment. FIG. 24 is a block diagram illustrating a configuration example of the lens unit according to the fourth embodiment. FIG. 25 is a block diagram illustrating a configuration example of a light emission amount command value conversion unit according to the fourth embodiment. FIG. 26 is a diagram for explaining an example of the relationship between the input signal and the output signal in the numerical comparison unit according to the fourth embodiment. FIG. 27 is a block diagram illustrating a configuration example of a light source according to the fifth embodiment. FIG. 28 is a block diagram illustrating a configuration example of a lens unit according to the fifth embodiment. FIG. 29 is a diagram illustrating a configuration example of a photosynthesis unit according to Embodiment 5. FIG. 30 is a diagram illustrating an example of a transmittance curve of the bandpass filter according to the fifth embodiment. FIG. 31 is a block diagram illustrating a configuration example of the light emission amount command value conversion unit according to the fifth embodiment.

  Hereinafter, an image projection apparatus and an image display apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration example of an image projection apparatus according to Embodiment 1 of the present invention. The image projecting device 81 according to the first embodiment shown in FIG. 1 is a device that projects image light onto the screen 7. When a malfunction occurs on the optical path (for example, on the screen 7), the malfunction (unintentionally inappropriate inappropriateness) occurs. Light) is detected promptly and image display is stopped. The image projection device 81 includes a light emission amount command value generation unit 1, a light emission amount command value conversion unit 2, a light source 3, a lens unit 4, a scanner (light scanning unit) 5, and a light amount sensor 6.

  The light emission amount command value generation unit 1 inputs (receives) a video signal IMG sent from a video signal output device (not shown) from the outside, and based on the externally input video signal IMG, a reference light emission amount command value Generate LA. The reference light emission amount command value LA is a reference value (data before conversion) of the light emission amount command value LB generated by the light emission amount command value conversion unit 2. If there is no problem on the optical path, for example, the reference light emission amount command value LA becomes the light emission amount command value LB as a command value (voltage command value or current command value) for driving the light source 3 as it is. . In other words, the reference light emission amount command value LA is a command value generated according to the video signal IMG (a command value of the light emission amount to the light source 3), and is a command reference value used for generating the light emission amount command value LB. . Further, the light emission amount command value LB is a command value obtained by correcting the reference light emission amount command value LA in accordance with a defect on the optical path. The light emission amount command value generation unit 1 outputs the generated reference light emission amount command value LA to the light emission amount command value conversion unit 2.

  The light emission amount command value conversion unit 2 inputs (receives) the received light amount RA output from the light amount sensor 6 and inputs (receives) a reset signal RST sent from the outside of the image projection device 81. The light emission amount command value conversion unit 2 determines a failure on the optical path based on the light reception amount RA and the reset signal RST, and converts the reference light emission amount command value LA into a light emission amount command value LB corresponding to the presence or absence of the failure. The light emission amount command value conversion unit 2 generates the light emission amount command value LB by converting the reference light emission amount command value LA into a value corresponding to the reference light emission amount command value LA and the light reception amount RA. The light emission amount command value conversion unit 2 outputs the generated light emission amount command value LB to the light source 3.

  The light source 3 modulates the light amount of the emitted light according to the light emission amount command value LB, and emits the light whose light amount has been modulated to the lens unit 4. In other words, the light amount emitted from the light source 3 (the light emission amount) is controlled by the light emission amount command value LB.

  The lens unit 4 shapes the light emitted from the light source 3 into a shape suitable for the scanner 5 and emits the light to the scanner 5. The scanner 5 two-dimensionally scans and projects the light emitted from the lens unit 4 onto the screen 7 installed outside the image projector 81. The screen 7 receives light emitted from the scanner 5 and displays an image (video).

  The light amount sensor 6 receives a light amount of a part of the light transmitted from the screen 7 side, and detects the received light amount (the received light amount). For example, the light quantity sensor 6 receives a part of the light emitted from the scanner 5 and reflected by the irradiating unit 8 on the screen 7 to detect the amount of received light. The light amount sensor 6 generates a received light amount RA as a signal corresponding to the detected received light amount, and outputs it to the emitted light amount command value conversion unit 2.

  FIG. 2 is a block diagram illustrating a configuration example of the light emission amount command value generation unit according to the first embodiment. The light emission amount command value generation unit 1 includes a video signal conversion unit 9 and a lookup table (hereinafter referred to as LUT) 10. Here, a case where the video signal IMG inputted to the light emission amount command value generation unit 1 is divided into R (red), G (green), and B (blue) colors, which are IMG_r, IMG_g, and IMG_b, respectively. explain.

  Video signals IMG_r, IMG_g, and IMG_b that are input to the light emission amount command value generation unit 1 are input to the video signal conversion unit 9, respectively. The video signal conversion unit 9 converts the video signals IMG_r, IMG_g, and IMG_b into reference light emission amount command values LA_r, LA_g, and LA_b, respectively, according to the relationship (conversion formula) given to the LUT 10 in advance. The reference light emission amount command values LA_r, LA_g, and LA_b are the command values of the voltage to the light source 3 when the light source 3 is a voltage drive type, and the current to the light source 3 when the light source 3 is a current drive type. It is a command value. Below, the case where the light source 3 is a current drive system will be described as an example.

  FIG. 3 is a diagram illustrating an example of the relationship between the video signal IMG set in advance in the LUT and the reference light emission amount command value LA. The graph of FIG. 3 shows the conversion relationship from the video signal IMG to the reference light emission amount command value LA. The horizontal axis in FIG. 3 is the gradation level (IMG_x) of the video signal IMG input to the video signal converter 9, and the vertical axis is the reference light emission amount command value LA (LA_x) corresponding to the video signal IMG.

  Ic is a cut-off current value determined by the specifications of the light source 3, and LA = Ic_x when the gradation level of the input video signal IMG is 0. As the gradation level of the video signal IMG increases, the reference light emission amount command value LA also gradually increases. Here, for simplicity of explanation, the case where the relationship between the video signal IMG and the reference light emission amount command value LA is linear is shown, but the relationship between the two changes depending on the characteristics of the light source 3 and the use environment. It is not limited to a linear relationship.

  FIG. 4 is a block diagram illustrating a configuration example of the light emission amount command value conversion unit. The light emission amount command value conversion unit 2 includes a light reception luminance correction unit 11, a light emission luminance estimation unit 12, a delay compensation unit 13, a numerical comparison unit 14, and a command signal conversion unit 15.

  The received light intensity correction unit 11 generates a corrected received light amount RB by correcting the received light amount RA input from the light amount sensor 6 and outputs the corrected received light amount RB to the numerical value comparison unit 14. For example, if the received light amount RA output from the light amount sensor 6 is an analog amount, the received light intensity correction unit 11 digitizes the received light amount RA. In addition, the received light intensity correction unit 11 performs noise removal of the received light amount RA using a low-pass filter or the like as necessary, thereby generating a corrected received light amount RB and outputting it to the numerical value comparison unit 14.

  Based on the reference light emission amount command values LA_r, LA_g, LA_b from the light emission amount command value generation unit 1, the light emission luminance estimation unit 12 calculates the light amount (light emission amount) emitted from the light source 3. The light emission luminance estimation unit 12 generates an estimated light emission luminance LY as a calculation result of the light amount emitted from the light source 3 and outputs the estimated light emission luminance LY to the delay compensation unit 13. The estimated light emission luminance LY is a value that predicts the amount of light emitted from the light source 3, and is calculated based on the reference light emission amount command values LA_r, LA_g, and LA_b. The delay compensation unit 13 generates a reference reflected light amount LYd obtained by delaying the estimated light emission luminance LY by a predetermined time (delay compensation amount dt2 described later), and outputs the reference reflected light amount LYd to the numerical comparison unit 14.

  The numerical comparison unit 14 generates a light emission amount conversion gain value LG based on the corrected received light amount RB, the reference reflected light amount LYd, and the threshold value TH, and outputs the light emission amount conversion gain value LG to the command signal conversion unit 15. The light emission amount conversion gain value LG is information indicating whether or not a defect has occurred on the optical path. The light emission amount conversion gain value LG is a value obtained by dividing the luminance of light transmitted from the screen 7 to the image projection device 81 by the luminance of light transmitted from the video signal output device to the image projection device 81 ( It is a value derived on the basis of (light quantity ratio) (gain). The light emission amount conversion gain value LG indicates, for example, “0” when a defect occurs on the optical path, and indicates “1” when a defect does not occur.

  The threshold value TH is a value that serves as a criterion for determining whether or not a defect has occurred on the optical path, and is a value that is compared with the luminance ratio of the light. When the light luminance ratio is smaller than the threshold value TH, the numerical value comparison unit 14 outputs “0” indicating the occurrence of a malfunction on the optical path as the light emission amount conversion gain value LG. The numerical comparison unit 14 outputs “1” indicating a normal state on the optical path as the light emission amount conversion gain value LG when the light luminance ratio is equal to or greater than the threshold value TH.

  Based on the light emission amount conversion gain value LG and the reset signal RST input from the outside of the image projection device 81, the command signal conversion unit 15 converts the reference light emission amount command values LA_r, LA_g, and LA_b into the light emission amount command values LB_r, LB_g, It converts to LB_b and outputs it to the light source 3. The reset signal RST is a signal (release instruction) for canceling the emission stop of the light source 3. The reset signal RST is externally input by a user or a microcomputer, for example, when it is confirmed that the optical path is in a normal state.

  FIG. 5 is a diagram for explaining the amount of delay compensation in the delay compensator. The chart of FIG. 5 shows the respective transmission timings of the reference light emission amount command value LA, the light emission amount command value LB, the corrected light reception amount RB, the estimated light emission luminance LY, and the reference reflected light amount LYd.

  In the light emission amount command value conversion unit 2, reference light emission amount command values LA0 to LAn (n is a natural number) are input as the reference light emission amount command value LA. Further, light emission amount command values LB0 to LBn corresponding to the respective reference light emission amount command values LA0 to LAn are output as the light emission amount command value LB, and corrected light reception amounts corresponding to the respective light emission amount command values LB0 to LBn as the corrected light reception amount RB. RB0 to RBn are output.

  Specifically, the reference light emission amount command values LA_r, LA_g, LA_b output from the light emission amount command value generation unit 1 are converted into light emission amount command values LB_r, LB_g, LB_b by the command signal conversion unit 15. The light source 3 emits light to the screen 7 based on the light emission amount command values LB_r, LB_g, and LB_b. The light reflected by the irradiation unit 8 on the screen 7 is received by the light quantity sensor 6, and the received light quantity RA is output from the light quantity sensor 6. The received light amount RA output from the light amount sensor 6 is corrected by the received light luminance correction unit 11 and output as a corrected received light amount RB.

  For example, after the reference emission amount command value LA0 is input, the emission amount command value LB0 corresponding to the reference emission amount command value LA0 is output with a delay of a predetermined time. Further, after the light emission amount command value LB0 is output, the corrected light reception amount RB0 corresponding to the light emission amount command value LB0 is output with a delay of a predetermined time. Similarly, after the reference light emission amount command value LAn is input, the light emission amount command value LBn corresponding to the reference light emission amount command value LAn is output with a delay of a predetermined time. Further, after the light emission amount command value LBn is output, the corrected light reception amount RBn corresponding to the light emission amount command value LBn is output with a delay of a predetermined time. The time required for a series of operations from the input of the reference light emission amount command values LA_r, LA_g, LA_b to the output of the corrected received light amount RB is defined as a feedback delay amount Dt.

  In the light emission amount command value conversion unit 2, the estimated light emission luminances LY0 to LYn are output as the estimated light emission luminance LY. Specifically, the light emission luminance estimation unit 12 calculates the amount of light emitted from the light source 3 based on the reference light emission amount command values LA_r, LA_g, LA_b, and generates and outputs the calculation result as the estimated light emission luminance LY.

  For example, after the reference emission amount command value LA0 is input, the estimated emission luminance LY0 corresponding to the reference emission amount command value LA0 is output with a delay of a predetermined time. Similarly, after the reference light emission amount command value LAn is output, the estimated light emission luminance LYn corresponding to the reference light emission amount command value LAn is output with a delay of a predetermined time. If the time required for a series of operations from the input of the reference light emission amount command values LA_r, LA_g, LA_b to the output of the estimated light emission luminance LYn is a delay amount dt1 (a delay amount in the light emission luminance estimation unit 12), the delay compensation amount dt2 = Dt−dt1.

  In other words, the delay compensation unit 13 outputs the reference reflected light amount LYd obtained by delaying the estimated light emission luminance LY by the delay compensation amount dt2. The corrected received light amount RB output from the received light luminance correction unit 11 and the reference reflected light amount LYd output from the delay compensation unit 13 are both input to the numerical value comparison unit 14. Accordingly, the reference reflected light amounts LYd0 to LYdn corresponding to the estimated light emission luminance LY output from the delay compensation unit 13 are input to the numerical comparison unit 14 at the same timing as the corrected received light amounts RB0 to RBn.

  For example, the reference reflected light amount LYd0 and the corrected received light amount RB0 are input to the numerical comparison unit 14 at the same time. Similarly, the reference reflected light amount LYdn and the corrected received light amount RBn are simultaneously input to the numerical comparison unit 14. The numerical value comparison unit 14 outputs a light emission amount conversion gain value LG based on the result of comparing the input corrected received light amount RB and the reference reflected light amount LYd.

  FIG. 6 is a diagram for explaining an example of a relationship between an input signal and an output signal in the numerical comparison unit according to the first embodiment. The input signal to the numerical comparison unit 14 is the reference reflected light amount LYd and the corrected light emission amount RB, and the output signal from the numerical comparison unit 14 is the light emission amount conversion gain value LG. In the graph shown in FIG. 6, the horizontal axis represents the ratio (RB / LYd) between the reference reflected light amount LYd and the corrected light emission amount RB, and the vertical axis represents the light emission amount conversion gain value LG output from the numerical comparison unit 14. The light emission amount conversion gain value LG is set to 0 when RB / LYd, which is the ratio of the reference reflected light amount LYd and the corrected received light amount RB, is smaller than the threshold value TH, and is set to 1 when it is equal to or larger than the threshold value TH.

  The received light amount RA of the light received by the light amount sensor 6 is a part of the light emitted from the light source 3 and reflected by the irradiation unit 8 on the screen 7 and external light. In a reference state in which the influence of external light is small, RB / LYd is determined mainly by the influence of the position of the irradiation unit 8 on the screen 7 and the like, such as the structure of the image projection device 81 and the image display device including the screen 7. It can take a value within the fluctuation range (predicted fluctuation range s) expected from the knowledge. Assuming that the lower limit value of the expected fluctuation range s is the threshold value TH, if RB / LYd is smaller than the threshold value TH, the light emitted from the light source 3 due to a defect on the optical path is reflected by the screen 7 and is reflected on the light amount sensor 6. It can be determined that the amount of incident light has decreased.

  Therefore, when RB / LYd is smaller than the threshold value TH, the numerical value comparison unit 14 determines that a problem has occurred on the optical path. In order to stop the light emission from the light source 3, the numerical value comparison unit 14 outputs the light emission amount conversion gain value LG as 0. When RB / LYd is larger than the threshold value TH, the numerical value comparison unit 14 outputs the light emission amount conversion gain value LG as 1. The threshold value TH may be determined in advance at the time of designing the system based on knowledge such as the transmittance of the lens optical system (the lens unit 4 and the like), the reflectance of the screen 7, and the maximum deflection angle of the scanner 5. Calibration may be performed every time setup is performed, and the threshold value TH may be determined each time.

  The reference light emission amount command values LA_r, LA_g, LA_b output from the light emission amount command value generation unit 1, the light emission amount conversion gain value LG output from the numerical comparison unit 14, and the reset signal input from the outside of the image projection device 81 Each RST is input to the command signal converter 15.

  FIG. 7 is a block diagram illustrating a configuration example of the command signal conversion unit according to the first embodiment. The command signal conversion unit 15 includes a zero gain holding unit 16 and a multiplication unit 17. The light emission amount conversion gain value LG output from the numerical comparison unit 14 and the reset signal RST input from the outside of the image projection device 81 are input to the zero gain holding unit 16. The zero gain holding unit 16 generates a light emission amount conversion gain reset value RG based on the input light emission amount conversion gain value LG and the reset signal RST, and outputs the light emission amount conversion gain reset value RG to the multiplication unit 17. The light emission amount conversion gain reset value RG is information for instructing whether to emit or stop the light from the light source 3. For example, when the light is emitted from the light source 3, the zero gain holding unit 16 outputs “1” as the light emission amount conversion gain reset value RG, and when the light from the light source 3 is stopped, the zero gain holding unit 16 is reset. “0” is output as the value RG.

  Based on the light emission amount conversion gain reset value RG, the multiplication unit 17 converts the reference light emission amount command values LA_r, LA_g, LA_b output from the light emission amount command value generation unit 1 into light emission amount command values LB_r, LB_g, LB_b. Output to the light source 3.

  FIG. 8 is a diagram for explaining the operation of the zero gain holding unit. FIG. 8 shows output timing charts of the clock signal (Clock), the light emission amount conversion gain value LG, the light emission amount conversion gain reset value RG, and the reset signal RST. Here, the case where the light emission amount conversion gain value LG output from the numerical comparison unit 14 is a binary value of “0” or “1” will be described as an example.

  Clock is a pixel clock of the video signal. The light emission amount command value conversion unit 2 operates according to the pixel clock. When the light emission amount conversion gain value LG output from the numerical comparison unit 14 is “1”, “1” is output as the light emission amount conversion gain reset value RG. When the light emission amount conversion gain value LG changes from “1” to “0”, “0” is output as the light emission amount conversion gain reset value RG. Thereafter, even if the light emission amount conversion gain value LG changes from “0” to “1”, “0” is continuously output as the light emission amount conversion gain reset value RG.

  When the light emission amount conversion gain reset value RG is “0”, the light emission amount conversion gain value LG output from the numerical comparison unit 14 is “1”, and the reset signal is input from the outside of the image projection device 81. If RST is “1” (active), the light emission amount conversion gain reset value RG changes to “1”. In other words, once the light emission amount conversion gain reset value RG becomes “0”, “0” is continuously output as the light emission amount conversion gain reset value RG unless an active reset signal RST is input.

  The light emission amount conversion gain reset value RG output from the zero gain holding unit 16 and the reference light emission amount command values LA_r, LA_g, LA_b output from the light emission amount command value generation unit 1 are input to the multiplication unit 17. The multiplication unit 17 multiplies the input reference light emission amount command values LA_r, LA_g, and LA_b by the light emission amount conversion gain reset value RG to generate and output the light emission amount command values LB_r, LB_g, and LB_b. At this time, if the light emission amount conversion gain reset value RG is “0”, the light emission amount command values LB_r, LB_g, and LB_b are all “0”, and the light source 3 stops emitting light. On the other hand, if the light emission amount conversion gain reset value RG is “1”, the light source 3 emits light of a light amount corresponding to the light emission amount command values LB_r, LB_g, and LB_b.

  FIG. 9 is a block diagram illustrating a configuration example of the light source according to the first embodiment. The light source 3 includes a power supply unit 18, current modulation units 19a, 19b, and 19c, LD_r20, LD_g21, and LD_b.

  The power supply unit 18 supplies energy (currents I_r, I_g, I_b) for causing the light source 3 to emit light to the current modulation units 19a, 19b, 19c. The current modulators 19a, 19b, and 19c are configured with a constant current circuit, for example. Based on the light emission amount command values LB_r, LB_g, and LB_b output from the light emission amount command value conversion unit 2, the current modulation units 19a, 19b, and 19c supply currents I_r, I_g, and I_b to be supplied to LD_r20, LD_g21, and LD_b22, respectively. Modulate and output to LD_r20, LD_g21, and LD_b22, respectively.

  LD_r20, LD_g21, and LD_b22 are laser diodes (hereinafter referred to as LDs) that emit light in the visible light region having different wavelengths. Specifically, LD_r20 emits red, LD_g21 emits green, and LD_b22 emits blue. The LD_g21 may be, for example, an infrared laser that has been wavelength-converted with a half-wave plate.

  FIG. 10 is a diagram for explaining the IP characteristic of the LD. In FIG. 10, the horizontal axis represents the current amount I_x, and the vertical axis represents the optical output P_x. The optical outputs P_x from the LD_r20, LD_g21, and LD_b22 are set as optical outputs P_r, P_g, and P_b, respectively. FIG. 10 shows the magnitude of the optical output P_x (x is one of r, g, or b) with respect to the current amount I_x (x is any of r, g, or b). The light output P_x starts to emit light with a current amount I_x equal to or greater than the cut-off current Ic_x, and the light output P_x increases as the current amount I_x increases.

  When the scanner 5 of the image projection apparatus 81 does not use a spatial modulation element such as DMD (registered trademark), HTPS, or LCOS, the gradation of each pixel is controlled by analog control of the amount of light emitted from the light source 3 (hereinafter referred to as light source modulation). Need to be generated. At this time, the light source modulation frequency is required to be a speed equivalent to the pixel clock (dot clock) of the input video signal IMG. In order to improve the frequency characteristics of the light source modulation, it is better to reduce the modulation amplitude, and even when the level of the input video signal IMG is 0, the current amount I_x is not set to 0 but is set to the cut-off current Ic_x. It is desirable.

  Light emitted from the LD_r20, LD_g21, and LD_b22 of the light source 3 enters the lens unit 4. FIG. 11 is a diagram illustrating a configuration example of a lens unit according to the first embodiment. The lens unit 4 includes condensing lenses 23a, 23b, and 23c, a light combining unit 26, and a projection lens 27.

  The light emitted from the LD_r 20 enters the light combining unit 26 through the condenser lens 23a. Further, the light emitted from the LD_g21 enters the light combining unit 26 via the condenser lens 23b, and the light emitted from the LD_b22 enters the light combining unit 26 via the condensing lens 23c. In the light combining unit 26, three light beams having different wavelengths are combined and output to the projection lens 27. The projection lens 27 collects the light emitted from the light combining unit 26 and outputs the collected light to the scanner 5.

  FIG. 12 is a diagram illustrating a configuration example of the photosynthesis unit according to the first embodiment. The light combining unit 26 includes a mirror 31 and half mirrors 32 and 33. The red light emitted from the condenser lens 23 a is bent by the mirror 31 and then overlapped with the blue light emitted from the condenser lens 23 c by the half mirror 32. The mixed light of red and blue generated by the half mirror 32 is superimposed on the green light emitted from the condenser lens 23 b by the half mirror 33 and emitted to the projection lens 27. Note that the order of combining light is not limited to the order shown in FIG. 12, and may be combined in any order.

  The scanner 5 scans (scans and projects) two-dimensionally the light emitted from the lens unit 4 with respect to the screen 7. The scanner 5 has a structure similar to that of a scanner used in a printer, an exposure apparatus, or the like. The scanner 5 is configured using a biaxial scanning technique using MEMS as disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-116696 (paragraphs 0009 to 0010, FIG. 1).

  FIG. 13 is a diagram for explaining an example of the operation of the scanner, and shows the locus of light emitted from the scanner. FIG. 13 shows an example when the screen 7 is viewed from the image viewer side. The broken lines in FIG. 13 indicate the scan locus 36 of the scanner 5 during the video blanking period. A solid line indicates a scan locus 35 of the scanner 5 in the effective video period 34 and is also a locus on which the irradiation unit 8 moves. The irradiation unit 8 moves on the scan trajectories 35 and 36 according to the scan position so as to be the same position as the scan position by the scanner 5.

  The effective video period 34 is a period during which an effective video to be displayed is scanned on the screen 7. The effective video period 34 is a video display area, and the video scanned by the scan locus 35 in the effective video period 34 is displayed on the screen 7. The video blanking period is a period during which an invalid video (blank) that is not a display target is scanned on the screen 7, and during this period, the video scanned by the scan locus 36 is not displayed on the screen 7.

  The scanning trajectories 35 and 36 of the scanner 5 are started from the upper left of the screen 7 according to a general video signal format, sequentially scanned from the upper line to the lower line, and when scanning each line. , Each line is scanned from left to right. When the scanning of the last line (the lowermost line) is completed, the scan locus 36 of the scanner 5 returns to the upper left start position.

  FIG. 14 is a diagram for explaining another example of the operation of the scanner, and shows another example of the locus of light emitted from the scanner. 13 differs from the scan trajectories 35 and 36 in FIG. 13 in that odd-numbered lines, which are odd-numbered lines, are scanned from left to right, and even-numbered lines, which are even-numbered lines, are scanned from right to left. . The advantage of this scanning method is that the driving frequency of the scanner can be reduced to half that of the method shown in FIG.

  Further, after the last line is scanned, the trajectory from the upper left to the lower right may be traced in reverse instead of returning to the upper left of the screen 7. In this case, since the time for returning the scan locus 36 of the scanner 5 from the lower right to the upper left is not required, the drive frequency of the scanner 5 can be lowered.

  FIG. 15 is a diagram illustrating an arrangement example of a front projection type image display device. FIG. 15 shows a cross-sectional view of the image display device 90 when the light emitted from the scanner 5 is viewed from the irradiation unit 8 side of the screen 7. The front projection type image display device 90 includes an image projection device 81 and a screen 7.

  In the front projection type image display device 90, the light projected on the screen 7 from the scanner 5 in the image projection device 81 is appropriately scattered on the screen 7, and the reflected scattered light is observed by the observer 40. At this time, when there is a defect on the optical path (for example, when there is an abnormality in the screen 7), when there is an abnormality in the screen 7, or between the image projection device 81 and the screen 7 or between the screen 7 and the observer 40 If there is, the observer 40 cannot properly observe the image.

  For example, when a hole is opened in the screen 7, the light emitted from the scanner 5 in the image projection device 81 is not diffusely reflected at the holed portion of the screen 7. For this reason, the observer 40 observes the external light inserted from the back surface of the screen 7.

  Further, since the space between the image projection device 81 and the screen 7 is not shielded from the outside, for example, when an obstacle enters the optical path, a shadow appears on the screen 7. Furthermore, since the obstacle reflects the light emitted from the scanner 5 in the image projection device 81 in an unexpected direction, the reflected light may enter the pupil of the observer 40 directly. All of these are observed as images unpleasant for the observer 40.

  FIG. 16 is a diagram illustrating an arrangement example of a rear projection type image display device. FIG. 16 shows a cross-sectional view of the image display device 91 when the observer 40 views the light emitted from the scanner 5 through the screen 7. For example, the rear projection type image display device 91 includes an image projection device 81, a screen 7, and a housing 24. The light emitted from the scanner 5 in the image projection device 81 is appropriately diffused by passing through the screen 7, and the diffuse transmitted light is observed by the observer 40.

  Unlike the image display device 90 shown in FIG. 15, the image display device 91 has an image projection device 81 housed in the housing 24. In the case of the image display device 91, by using an LD for the light source 3 in the image projection device 81, the projection optical system can be downsized due to the excellent convergence of the laser as compared with the case where other types of light sources are used. Become. In addition, by using an LD for the light source 3, it is possible to reduce the beam spot diameter at the irradiation unit 8 on the screen 7, so that the resolution is improved.

  Further, in the image display device 91, since the image projection device 81 is housed in the housing 24, an obstacle enters before the light emitted from the scanner 5 in the image projection device 81 enters the screen 7. I won't do it. Furthermore, since the light quantity sensor 6 is not directly exposed to outside light, noise during light quantity detection can be reduced.

  On the other hand, when there is an abnormality in the screen 7, particularly when the screen 7 has a hole, the image display device 91 directly observes the light emitted from the scanner 5 without being diffused by the screen 7 depending on the position of the hole. Since it enters the retina of the person 40, it will be recognized as a very unpleasant image. In particular, when an LD is used as the light source, it is not preferable to irradiate the retina with direct light for a long time even if the light has low power. Therefore, in the present embodiment, the emission of light from the light source 3 is stopped so that the light emitted from the scanner 5 does not directly enter the retina of the observer 40.

  Both the front projection type image display device 90 and the rear projection type image display device 91 are reflected by the irradiation unit 8 on the screen 7 when there are no obstacles on the optical path and no trouble on the optical path such as an abnormality of the screen 7. A part of the light enters the light amount sensor 6 together with outside light that is light from other than the light source 3. However, for example, when an obstacle enters the optical path, or when a hole is formed in the screen 7, the light emitted from the scanner 5 is not reflected by the screen 7, and only external light enters the light amount sensor 6. . In particular, when an LD is used as the light source 3, the beam spot diameter can be reduced due to the excellent convergence of the laser, so that even a minute hole on the screen 7 causes a difference in the amount of light incident on the light amount sensor 6.

  FIG. 17 is a block diagram illustrating a configuration example of the light amount sensor. The light quantity sensor 6 includes a condenser lens 37, a band pass filter 38, and a photo sensor 39. Part of the light reflected by the irradiation unit 8 on the screen 7 is collected by the condenser lens 37 and enters the bandpass filter 38. The band-pass filter 38 selectively transmits (filters) a specific wavelength of incident light and outputs it to the photosensor 39. The photo sensor 39 photoelectrically converts incident light and outputs a received light amount RA.

  FIG. 18 is a diagram illustrating an example of a transmittance curve of the bandpass filter according to the first embodiment. In FIG. 18, the spectrum of the light emitted from LD_r20, LD_g21, and LD_b22 is also shown by broken lines. The transmittance curve L1 of the band-pass filter 38 is a transmittance curve having a transmission center wavelength of the light emitted from the light source 3 (LD_r20 is about 640 nm, LD_g21 is about 530 nm, and LD_b22 is about 450 nm).

  The band pass filter 38 is used to accurately detect light emitted from the light source 3 and reflected by the screen 7 as light incident on the light amount sensor 6. In other words, the band pass filter 38 is used to reduce the influence of outside light from other than the light source 3. Therefore, it is desirable that the bandpass filter 38 transmits light having a wavelength emitted from the light source 3 as much as possible and shields light having a wavelength not emitted from the light source 3 as much as possible.

  In the transmittance curve L1 shown in FIG. 18, the FWHM of the transmissive region is indicated by about 10 nm. However, as long as the light receiving sensitivity of the light sensor 6 and the manufacturing cost of the bandpass filter 38 allow, the FWHM of the transmissive region is a little. But narrower is better. The fact that the FWHM of the transmission region can be narrowed is also an advantage of using an LD having a sharp spectrum for the light source 3.

  The light that has passed through the bandpass filter 38 enters the photosensor 39. The photosensor 39 generates a received light amount RA by photoelectrically converting the integrated value of light incident during the sampling time t, and outputs the received light amount RA to the light emission amount command value conversion unit 2. If the sampling time t is, for example, the time of the dot clock cycle of the input video signal IMG, a minute hole on the screen 7 having a width of one pixel can be detected.

  As described above, the numerical value comparison unit 14 compares the ratio RB / LYd between the reference reflected light amount LYd and the corrected received light amount RB with the threshold value TH, so that an unintended light toward the observer 40 is obstructed on the optical path. An intrusion of an object or a malfunction on the screen 7 (for example, a hole in the screen 7 is detected) is detected. Therefore, it is possible to easily and accurately detect a defect on the optical path with a simple configuration.

  Further, once the light emission amount conversion gain value LG output as a comparison result between RB / LYd and the threshold value TH becomes “0”, the numerical value comparison unit 14 performs the light emission amount conversion gain value LG unless an active reset signal RST is input. Is not set to “1” again. For this reason, when a problem on the optical path occurs, no light is emitted from the light source 3, and the observer 40 does not continue to view an unpleasant image.

  In addition, by using an LD for the light source 3, the projection optical system can be reduced in size and the beam spot diameter can be reduced compared to the case of using another type of light source due to the excellent convergence of the laser, and the high definition. Image display becomes possible. Further, since the beam spot diameter can be reduced, it is possible to detect minute holes on the screen 7.

  Further, the transmittance curve L1 of the band-pass filter 38 mounted on the light quantity sensor 6 is a transmittance curve with the wavelength of the light emitted from the light source 3 as the transmission center wavelength. It is possible to prevent the light from entering the photosensor 39. Therefore, the light quantity sensor 6 can efficiently detect a part of the light reflected by the irradiation unit 8 on the screen 7.

  In the present embodiment, the case where the light source 3 is not illuminated when RB / LYd is smaller than the threshold TH has been described. However, when a reflector other than the screen 7 enters the optical path (for example, without intention) When a mirror or the like enters the optical path), it is assumed that the amount of light received by the light receiving sensor 6 becomes extremely large. For this reason, processing may be performed so that the light source 3 is not illuminated even when RB / LYd is extremely larger than the threshold value TH.

  As described above, according to the first embodiment, unintended light (inappropriate light) (such as light that has not been diffused by the screen 7) due to the occurrence of a defect on the optical path is promptly based on the received light amount RA. Therefore, the emission of light from the light source 3 is stopped, so that it is possible to stop the unintentional emission of light from the screen 7. Therefore, when there is a defect on the optical path, no light is emitted from the light source 3, and it is reflected in an unexpected direction by the light that has not been diffused by the screen 7, the shadow of the obstacle on the optical path, or the obstacle. Do not continue to watch unpleasant images including light.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, a part of the reflected light from the screen 7 is detected using the respective light quantity sensors arranged at a plurality of positions.

  FIG. 19 is a block diagram illustrating a configuration example of the image projection apparatus according to the second embodiment. Of the constituent elements shown in FIG. 19, the constituent elements that achieve the same functions as those of the image projection apparatus 81 of the first embodiment shown in FIG.

  The image projection device 82 according to the second embodiment is different from the image projection device 81 shown in FIG. 1 in that the image projection device 82 includes two light quantity sensors 6a and 6b, and the image projection device 82 is newly added. For example, an accumulating unit (adding unit) 41 is added.

  The video signal IMG is input to the light emission amount command value generation unit 1. The light emission amount command value generation unit 1 generates a reference light emission amount command value LA based on the input video signal IMG and outputs it to the light emission amount command value conversion unit 2.

  The light emission amount command value conversion unit 2 inputs the received light amount RA output from the accumulation unit 41 and also receives a reset signal RST sent from the outside of the image projection device 82. The light emission amount command value conversion unit 2 converts the reference light emission amount command value LA into the light emission amount command value LB based on the light reception amount RA and the reset signal RST, and outputs the light emission amount command value LB to the light source 3.

  The light quantity sensors 6a and 6b receive a part of the light emitted from the scanner 5 and reflected by the irradiation unit 8 on the screen 7, and detect the amount of received light. The light quantity sensors 6a and 6b of the present embodiment detect the amount of received light from the irradiation unit 8 at different positions on the screen 7, respectively. The light quantity sensors 6 a and 6 b generate received light amounts RAa and RAb as signals corresponding to the detected received light amounts, and output them to the accumulating unit 41. The accumulating unit 41 generates the received light amount RA by adding the received light amounts RAa and RAb input from the light quantity sensors 6a and 6b, respectively, and outputs the received light amount RA to the emitted light amount command value converting unit 2.

  FIG. 20 is a perspective view illustrating an arrangement example of the scanner and the light amount sensor. In the projection method using the scanner 5, when the scanner 5 is arranged on the central axis 25 of the screen 7, the amount of amplitude of the scanner 5 can be minimized, and distortion on the screen 7 caused by scanning is also reduced. Actually, there are problems such as interference with other devices, and, for example, in the case of the front projection type, there is a problem of crossing with the observer. Therefore, the scanner 5 is arranged offset in the vertical direction with respect to the central axis 25. There are many cases. In the present embodiment, the scanner 5 may be arranged on the central axis 25 of the screen 7, or the scanner 5 may be arranged offset in the vertical direction with respect to the central axis 25.

  As the irradiation unit 8 moves to the periphery of the screen 7, the incident angle φ of the light emitted from the scanner 5 with respect to the screen 7 increases. For this reason, there may occur a case where only one light quantity sensor 6 fixed at an arbitrary place cannot sufficiently receive a part of the reflected light from the entire screen 7. Therefore, in the present embodiment, two light quantity sensors, a light quantity sensor 6a and a light quantity sensor 6b, are arranged. The light amount sensor 6a receives a part of the reflected light from the irradiation unit 8 corresponding to the light amount sensor 6a and detects the amount of received light, and the light amount sensor 6b reflects from the irradiation unit 8 corresponding to the light amount sensor 6b. A part of the light is received and the amount of received light is detected. The received light amounts RAa and RAb output from the two light quantity sensors 6a and 6b are added by the accumulating unit 41 to generate the received light amount RA.

  In order to improve the detection accuracy of the reflected light from the irradiation unit 8, the two light quantity sensors 6 a and 6 b are arranged symmetrically with respect to the virtual axis including the central axis 25 of the screen 7 and the scanner 5. It is desirable.

  In FIGS. 19 and 20, two light quantity sensors 6 a and 6 b are arranged as light quantity sensors. However, the number of arranged light quantity sensors is not limited to two, and three or more light quantities are arranged. A sensor may be arranged. In this case as well, the detection accuracy is improved by arranging the light amount sensor symmetrically with respect to the central axis of the screen 7.

  In the present embodiment, the image projecting device 82 includes the accumulating unit 41, but the image projecting device 82 may not include the accumulating unit 41. In this case, the received light amounts RAa and RAb output from the light quantity sensors 6a and 6b are input to the emitted light amount command value conversion unit 2, respectively. When the image projection device 82 does not include the accumulating unit 41, the light emission amount command value conversion unit 52 determines which of the light amount sensors 6 a and 6 b detects the light amount from the detection unit 8 based on the position of the detection unit 8. Get information about. And the malfunction on an optical path is detected for every position of the detection part 8. FIG.

  As described above, according to the second embodiment, the light receiving amount of the reflected light from the screen 7 is detected by being shared by the plurality of light quantity sensors 6a and 6b, so that the irradiation unit 8 of the light emitted from the scanner 5 is provided. Even when it is in the peripheral part (near the peripheral part) of the screen 7, it becomes possible to detect a part of the reflected light from the screen 7 with high accuracy.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. In the third embodiment, the received light amounts RAa and RAb are amplified with an amplification factor according to the magnitude of the emission angle of light transmitted from the scanner 5 to the screen 7 (an emission angle signal dθ described later).

  FIG. 21 is a block diagram illustrating a configuration example of an image projection apparatus according to the third embodiment. Of the constituent elements in FIG. 21, the same reference numerals are used for constituent elements that achieve the same functions as those of the image projecting apparatus 81 of the first embodiment shown in FIG. 1 and the image projecting apparatus 82 of the second embodiment shown in FIG. The description which overlaps is abbreviate | omitted.

  The image projection device 83 is different from the image projection devices 81 and 82 in that the image projection device 83 has angle correction units (light reception amount correction units) 42a and 42b as new components, and the angle correction is performed from the scanner 5. For example, the emission angle signal dθ is sent to the portions 42a and 42b. The emission angle signal dθ is information indicating the emission angle of light transmitted from the scanner 5 to the screen 7 and is detected by the scanner 5. The light emission angle signal dθ is an angle in the light scanning direction with respect to the screen 7 and is a scanning angle of the scanner 5 when scanning light. The scanner 5 includes an angle detection unit 55, and the angle detection unit 55 detects an emission angle signal dθ of light.

  The video signal IMG is input to the light emission amount command value generation unit 1. The light emission amount command value generation unit 1 generates a reference light emission amount command value LA based on the input video signal IMG and outputs it to the light emission amount command value conversion unit 2.

  The light emission amount command value conversion unit 2 inputs the light reception amount RA output from the accumulation unit 41 and also receives a reset signal RST sent from the outside of the image projection device 83. The light emission amount command value conversion unit 2 converts the reference light emission amount command value LA into the light emission amount command value LB based on the light reception amount RA and the reset signal RST, and outputs the light emission amount command value LB to the light source 3.

  The scanner 5 scans the light emitted from the lens unit 4 two-dimensionally with respect to the screen 7, detects the light emission angle signal dθ by the angle detection unit 55, and outputs it to the angle correction units 42 a and 42 b. The light quantity sensors 6a and 6b receive a part of the light emitted from the scanner 5 and reflected by the irradiation unit 8 on the screen 7, and detect the amount of received light. The light quantity sensors 6a and 6b generate received light amounts RAa and RAb as signals corresponding to the detected received light amounts, and output them to the angle correction units 42a and 42b, respectively.

  The angle correction units 42a and 42b normalize and correct the received light amounts RAa and RAb, respectively, based on the emission angle signal dθ output from the scanner 5, thereby generating the angle corrected received light amounts RAA and RAB and accumulating units. 41 is output. The accumulating unit 41 generates the received light amount RA by adding the angle corrected received light amounts RAA and RAB input from the angle correcting units 42 a and 42 b, and outputs the received light amount RA to the emitted light amount command value converting unit 2.

  As a method for detecting the light emission angle θ in the scanner 5, for example, a change in the rotation angle of the scanning mirror using a position sensing element as disclosed in Japanese Patent Application Laid-Open No. 2007-183264 (paragraph 0023, FIG. 3). Use a method that directly detects. Further, since the scanner 5 vibrates in synchronization with the synchronization signal of the input video signal IMG, the video signal IMG may be analyzed using a counter to calculate the light emission angle θ.

  Next, the angle correction units 42a and 42b will be described in detail. FIG. 22 is a diagram illustrating a relationship example between an input signal and an output signal in the angle correction unit. The horizontal axis in FIG. 22 is the emission angle signal dθ, and the vertical axis is the angle-corrected received light amount RAA / received light amount RAa. In FIG. 22, the angle corrected light reception amount RAA / light reception amount RAa with respect to the emission angle signal dθ is shown, but the angle correction light reception amount RAB / light reception amount RAb with respect to the emission angle signal dθ has the same relationship.

  Since the image projection device 83 is arranged to face the screen surface of the screen 7, the light emission angle θ = the screen incident angle φ. Therefore, as the light emission angle θ from the scanner 5 increases, the incident angle to the screen 7 increases, and as the incident angle to the screen 7 increases, the reflection from the screen 7 that can be received by the light quantity sensors 6a and 6b. Light decreases.

  Therefore, in the present embodiment, the angle correction units 42a and 42b greatly amplify the received light amounts RAa and RAb output from the light quantity sensors 6a and 6b as the emission angle signal dθ output from the scanner 5 increases. Output as corrected received light amounts RAA and RAB. In other words, the angle correction units 42a and 42b amplify (correct) the received light amounts RAa and RAb with an amplification factor according to the magnitude of the emission angle signal dθ output from the scanner 5.

  Specifically, the angle correction unit 42a amplifies the light reception amount RAa to the angle correction light reception amount RAA so that the relationship between the emission angle signal dθ and the angle correction light reception amount RAA / light reception amount RAa is as shown in FIG. To do. Similarly, the angle correction unit 42b converts the light reception amount RAb into the angle correction light reception amount RAB so that the relationship between the emission angle signal dθ and the angle correction light reception amount RAB / light reception amount RAb is similar to the relationship shown in FIG. Amplify to.

  As described above, according to the third embodiment, as the emission angle signal dθ is larger, the received light amounts RAa and RAb output from the light quantity sensors 6a and 6b are corrected so as to be greatly amplified. Even when 8 is in the peripheral portion of the screen 7, the reflected light from the screen 7 can be detected with high accuracy.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In the fourth embodiment, a defect on the optical path is detected using the light emission luminance of light incident on the lens unit and the luminance of light received from the screen 7.

  FIG. 23 is a block diagram illustrating a configuration example of an image projection apparatus according to the fourth embodiment. 23, the same number is attached | subjected about the component which achieves the same function as the image projector 81 of Embodiment 1 shown in FIG. 1 among each component of FIG.

  The image projection device 84 is different from the image projection device 81 in that the image projection device 84 has a light amount sensor (light source light amount detection unit) 56 as a new component. The image projection device 84 includes a light emission amount command value conversion unit 52 instead of the light emission amount command value conversion unit 2, and includes a lens unit 54 instead of the lens unit 4.

  The video signal IMG is input to the light emission amount command value generation unit 1. The light emission amount command value generation unit 1 generates a reference light emission amount command value LA based on the input video signal IMG and outputs it to the light emission amount command value conversion unit 52.

  The light emission amount command value conversion unit 52 is based on the light reception amount RA output from the light amount sensor 6, the reset signal RST sent from the outside of the image projection device 82, and the light emission amount EA output from the light amount sensor 56. The light emission amount command value LA is converted into a light emission amount command value LB and output to the light source 3.

  The light quantity sensor 56 is disposed between the light source 3 and the scanner 5. The light quantity sensor 56 receives a part of the light that enters and is combined with the lens unit 54 and detects the amount of received light. The light amount sensor 56 generates a light emission amount EA as a signal corresponding to the detected light reception amount, and outputs the light emission amount EA to the light emission amount command value conversion unit 52.

  FIG. 24 is a block diagram illustrating a configuration example of the lens unit according to the fourth embodiment. 24, the same number is attached | subjected about the component which achieves the same function as the lens part 4 of Embodiment 1 shown in FIG. 11 among each component of FIG. 24, and the overlapping description is abbreviate | omitted.

  The lens unit 54 according to the fourth embodiment is different from the lens unit 4 according to the first embodiment illustrated in FIG. 11 in that the lens unit 54 includes a half mirror 46 between the light combining unit 26 and the projection lens 27. It is a point. The half mirror 46 emits a part of the light synthesized by the light synthesis unit 26 to the projection lens 27 and reflects a part of the light to be emitted to the light quantity sensor 56.

FIG. 25 is a block diagram illustrating a configuration example of a light emission amount command value conversion unit according to the fourth embodiment.
25, the same number is attached | subjected about the component which achieves the same function as the light emission quantity command value conversion part 2 of Embodiment 1 shown in FIG. 4 among each component of FIG. 4, and the overlapping description is abbreviate | omitted. .

  The light emission amount command value conversion unit 52 differs from the light emission amount command value conversion unit 2 in that the light emission amount command value conversion unit 52 uses a light emission luminance correction unit 47 instead of the light emission luminance estimation unit 12 and the delay compensation unit 13. This is the point they have.

  The received light intensity correction unit 11 generates a corrected received light amount RB by correcting the received light amount RA input from the light amount sensor 6 and outputs the corrected received light amount RB to the numerical value comparison unit 14. The light emission luminance correction unit 47 generates a corrected light emission amount EB by correcting the light emission amount EA input from the light amount sensor 56 and outputs the corrected light emission amount EB to the numerical value comparison unit 14. For example, if the light emission amount EA output from the light amount sensor 56 is an analog amount, the light emission luminance correction unit 47 digitizes the light emission amount EA and performs noise removal using a low-pass filter or the like as necessary. Thus, a corrected light emission amount EB is generated and output to the numerical value comparison unit 14.

  The numerical comparison unit 14 generates a light emission amount conversion gain value LG based on the corrected light reception amount RB, the corrected light emission amount EB, and the threshold value TH, and outputs the light emission amount conversion gain value LG to the command signal conversion unit 15. The light emission amount conversion gain value LG here is a value derived based on a ratio (gain) between the luminance of light transmitted to the screen 7 and the luminance of light transmitted from the screen 7 to the image projection device 81. It is. The numerical value comparison unit 14 of the present embodiment outputs a light emission amount conversion gain value LG based on the result of comparing the ratio between the input corrected light reception amount RB and the correction light emission amount EB and the threshold value TH.

  Based on the light emission amount conversion gain value LG and the reset signal RST input from the outside of the image projection device 84, the command signal conversion unit 15 converts the reference light emission amount command values LA_r, LA_g, LA_b to the light emission amount command values LB_r, LB_g, It converts to LB_b and outputs it to the light source 3.

  FIG. 26 is a diagram for explaining an example of the relationship between the input signal and the output signal in the numerical comparison unit according to the fourth embodiment. In the graph shown in FIG. 26, the horizontal axis represents the ratio (RB / EB) of the corrected light emission amount EB and the corrected light reception amount RB, and the vertical axis represents the light emission amount conversion gain value LG output from the numerical comparison unit 14. The light emission amount conversion gain value LG is set to 0 when RB / EB, which is the ratio of the corrected light emission amount EB and the corrected light reception amount RB, is smaller than the threshold value TH, and is set to 1 when it is equal to or larger than the threshold value TH. Here, the threshold value TH may be a value different from the threshold value TH used by the numerical value comparison unit 14 of the first embodiment.

  The received light amount RA of the light received by the light amount sensor 6 is a part of the light emitted from the light source 3 and reflected by the irradiation unit 8 on the screen 7 and external light. In a reference state in which the influence of external light is small, RB / EB is determined mainly by the influence of the position of the irradiation unit 8 on the screen 7, and the structure of the image projection device 84 and the image display device including the screen 7 is determined. A value within the predicted fluctuation range s predicted from the knowledge can be taken. When the lower limit value of the expected fluctuation range s is the threshold value TH, if RB / EB is smaller than the threshold value TH, the light emitted from the light source 3 due to a defect on the optical path is reflected by the screen 7 and is reflected on the light amount sensor 6. It can be determined that the amount of incident light has decreased.

  Therefore, when RB / EB is smaller than the threshold value TH, the numerical value comparison unit 14 determines that a defect has occurred on the optical path. In order to stop the light emission from the light source 3, the numerical value comparison unit 14 outputs the light emission amount conversion gain value LG as 0. When RB / EB is larger than the threshold value TH, the numerical value comparison unit 14 outputs the light emission amount conversion gain value LG as 1. The threshold value TH may be determined in advance based on knowledge such as the transmittance of the lens optical system, the reflectance of the screen 7, and the maximum deflection angle of the scanner 5 at the time of designing the system. And the threshold value TH may be determined each time.

  The reference light emission amount command values LA_r, LA_g, LA_b output from the light emission amount command value generation unit 1, the light emission amount conversion gain value LG output from the numerical value comparison unit 14, and the reset signal input from the outside of the image projection device 84. Each RST is input to the command signal converter 15.

  The command signal conversion unit 15 has the same function as the command signal conversion unit 15 of the first embodiment, and performs the same operation. Further, the zero gain holding unit 16 and the multiplication unit 17 have the same functions as the zero gain holding unit 16 and the multiplication unit 17 of the first embodiment, and perform the same operation.

  The image projection apparatus may be configured by combining the image projection apparatus 84 of the present embodiment and the image projection apparatuses 82 and 83 of the second and third embodiments. For example, in the present embodiment, the case where there is one light quantity sensor 6 that receives the reflected light from the screen 7 has been described, but a plurality of light quantity sensors may be used. The image projection device 84 may include the angle correction units 42a and 42b.

  As described above, according to the fourth embodiment, the light incident on the lens unit 54 is received by the light amount sensor 56 to generate the light emission amount EA, and the reference light emission amount command is based on the light emission amount EA and the corrected light emission amount EB. Since the values LA_r, LA_g, and LA_b are converted into the light emission amount command values LB_r, LB_g, and LB_b, it is not necessary to estimate the luminance of the light emitted from the light source 3 by calculation. For this reason, even when a device whose output changes with time is used for the light source 3, it is possible to accurately detect an intrusion of an obstacle into the optical path and a defect on the screen 7.

Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In the fifth embodiment, invisible light is emitted from the light source together with red, green, and blue, and a defect on the optical path is detected based on the luminance of the invisible light. In the present embodiment, the light source of the fifth embodiment (a light source 53 to be described later) is arranged instead of the light source 3 with respect to any of the image projection devices 81 to 84, so that the image projection device of the present embodiment is changed. Configure. Below, the case where the light source 53 of Embodiment 5 is arrange | positioned to the image projector 81 is demonstrated as an example of the image projector of this Embodiment.

  FIG. 27 is a block diagram illustrating a configuration example of a light source according to the fifth embodiment. 27, the same number is attached | subjected about the component which achieves the same function as the light source 3 of Embodiment 1 shown in FIG. 9 among each component of FIG. 27, and the overlapping description is abbreviate | omitted.

  The light source 53 according to the fifth embodiment is different from the light source 3 according to the first embodiment in that the light source 53 has at least one LD_Ir 49 as a new component. The power supply unit 18 supplies energy for illuminating the light source to the current modulation units 19a, 19b, 19c, and LD_Ir49. LD_Ir49 is an LD that emits invisible light (for example, infrared light) having a wavelength different from that of LD_r20, LD_g21, and LD_b22.

  The current modulators 19a, 19b, and 19c are configured with a constant current circuit, for example. Based on the light emission amount command values LB_r, LB_g, and LB_b output from the light emission amount command value conversion unit 2, the current modulation units 19a, 19b, and 19c supply currents I_r, I_g, and I_b to be supplied to LD_r20, LD_g21, and LD_b22, respectively. Modulate and output to LD_r20, LD_g21, and LD_b22, respectively.

  On the other hand, the LD_Ir 49 is not connected to the light emission amount command values LB_r, LB_g, and LB_b output from the light emission amount command value conversion unit 2. For this reason, the LD_Ir 49 always outputs invisible light such as infrared light, regardless of the input video signal IMG, while the energy for illuminating the light source 3 is supplied from the power supply unit 18.

  FIG. 28 is a block diagram illustrating a configuration example of a lens unit according to the fifth embodiment. 28, the same number is attached | subjected about the component which achieves the same function as the lens part 4 of Embodiment 1 shown in FIG. 11 among each component of FIG.

  The lens unit 64 according to the fifth embodiment is different from the lens unit 4 shown in FIG. 11 in that the lens unit 64 has a condensing lens 23d as a new component, and photosynthesis is performed instead of the photosynthesis unit 26. For example, it has a portion 66. Light emitted from the LD_r20, LD_g21, and LD_b22 is incident on the light combining unit 66 through the condenser lens 23a, the condenser lens 23b, and the condenser lens 23c, respectively. In addition, the light emitted from the LD_Ir 49 enters the light combining unit 66 through the condenser lens 23d. In the light combining unit 66, the four light beams having different wavelengths are combined and output to the projection lens 27. The projection lens 27 collects the light emitted from the light combining unit 66 and outputs the collected light to the scanner 5.

  FIG. 29 is a diagram illustrating a configuration example of a photosynthesis unit according to Embodiment 5. 29, the same number is attached | subjected about the component which achieves the same function as the photosynthesis part 26 of Embodiment 1 shown in FIG. 12 among each component of FIG. 29, and the overlapping description is abbreviate | omitted.

  The light combining unit 66 according to the fifth embodiment is different from the light combining unit 26 illustrated in FIG. 12 in that the light combining unit 66 includes the half mirror 30 as a new component. The red light emitted from the condenser lens 23 a is bent by the mirror 31 and then overlapped with the blue light emitted from the condenser lens 23 c by the half mirror 32. The mixed red and blue light generated by the half mirror 32 is superposed on the green light emitted from the condenser lens 23b by the half mirror 33. The mixed light of red, blue and green generated by the half mirror 33 is superposed on the red light emitted from the condenser lens 23d by the half mirror 30. The mixed light of red, blue, green, and infrared emitted from the half mirror 30 is emitted to the projection lens 27. Note that the order of combining light is not limited to the order shown in FIG. 29, and may be combined in any order.

  The light emitted from the lens unit 64 is projected onto the screen 7 via the scanner 5. Since LD_Ir49 is invisible infrared light, the front projection type and the rear projection type do not cause a difference in the appearance of the image from the observer 40 due to the addition of LD_Ir.

  The light quantity sensor 6 of the present embodiment has a configuration substantially similar to that of the light quantity sensor 6 shown in FIG. The light amount sensor 6 of the present embodiment, as the bandpass filter 38, transmits invisible light (infrared light) from the LD_Ir 49 and does not transmit red, blue, and green light.

  FIG. 30 is a diagram illustrating an example of a transmittance curve of the bandpass filter according to the fifth embodiment. The difference between the bandpass filter 38 according to the fifth embodiment and the bandpass filter 38 shown in FIG. 18 is that the bandpass filter 38 according to the fifth embodiment cuts off all wavelengths in the visible light region and newly For example, the transmittance curve L2 transmits only the wavelength of light emitted from the LD_Ir 49 (in this example, around 1060 nm).

  The light amount sensor 6 selectively transmits a specific wavelength of incident light by the built-in bandpass filter 38 and outputs the light to the photosensor 39. The photosensor 39 photoelectrically converts incident light and outputs a received light amount RA. As described above, since the light quantity sensor 6 of the present embodiment uses the band-pass filter 38 (transmittance curve L2) that transmits only a part of the invisible light region, external light is almost incident on the photosensor 39. There is no. The received light amount RA output from the light amount sensor 6 is output to the light emission amount command value conversion unit 2, for example, as shown in FIG.

  FIG. 31 is a block diagram illustrating a configuration example of the light emission amount command value conversion unit according to the fifth embodiment. 29, the configuration that achieves the same function as the light emission amount command value conversion unit 2 of the first embodiment shown in FIG. 4 and the light emission amount command value conversion unit 52 of the fourth embodiment shown in FIG. Elements are given the same numbers, and duplicate descriptions are omitted.

  The light emission amount command value conversion unit 62 according to the fifth embodiment is different from the light emission amount command value conversion unit 2 shown in FIG. 2 in that the light emission amount command value conversion unit 62 uses the light emission luminance estimation unit 12 and the delay compensation unit 13. This is a point that they do not have. The light emission amount command value conversion unit 62 differs from the light emission amount command value conversion unit 52 shown in FIG. 25 in that the light emission amount command value conversion unit 62 does not have the light emission luminance correction unit 47.

  The received light intensity correction unit 11 generates a corrected received light amount RB by correcting the received light amount RA input from the light amount sensor 6 and outputs the corrected received light amount RB to the numerical value comparison unit 14. The numerical comparison unit 14 generates a light emission amount conversion gain value LG based on the corrected light reception amount RB, the preset light emission luminance YIr, and the threshold value TH, and outputs the light emission amount conversion gain value LG to the command signal conversion unit 15. The light emission luminance YIr is the light emission luminance (predicted value) of the light emitted from the LD_Ir49. The light emission amount conversion gain value LG here is the luminance (predicted value) of light from the LD_Ir 49 sent to the screen 7 and the luminance (measured value) of light from the LD_Ir 49 sent from the screen 7 to the image projection device 81. And is derived based on the ratio. The numerical value comparison unit 14 of the present embodiment outputs a light emission amount conversion gain value LG based on the result of comparing the ratio between the input corrected received light amount RB and the light emission luminance YIr and the threshold value TH.

  The light emission luminance YIr may be a predicted value of the corrected received light amount RB generated by being input from the light amount sensor 6, or a value for comparison with the corrected received light amount RB. Also in this case, a threshold value TH corresponding to the magnitude of the light emission luminance YIr is set. Further, the corrected received light amount RB and the threshold value TH may be directly compared.

  The command signal conversion unit 15 converts the reference light emission amount command values LA_r, LA_g, and LA_b into the light emission amount command values LB_r and LB_g, respectively, based on the light emission amount conversion gain value LG and the reset signal RST input from the outside of the image projection device 81. , LB_b and output to the light source 3.

  In the present embodiment, LD_r20, LD_g21, and LD_b22 constituting the light source 53 change the intensity of the emitted light according to the level of the input video signal IMG, but LD_Ir49 does not depend on the level of the input video signal IMG. The light of the emission luminance YIr is always emitted. For this reason, the received light amount RA output from the light quantity sensor 6 is always the light emitted by the LD_Ir as long as there is no obstacle in the optical path or there is an abnormality on the screen 7 even if the video signal IMG is black. A part of the light is received.

  The numerical comparison unit 14 does not need to estimate the amount of light emitted from the light source 3 based on the video signal IMG, but based on the ratio RB / YIr of the ratio of the corrected received light amount RB and the preset emission luminance YIr. A light emission amount conversion gain value LG is generated and output. For example, RB / YIr normally indicates a value of 1 or less, but when RB / YIr takes an extremely small value (a value smaller than a predetermined value), it is determined that reflected light cannot be obtained from the screen 7. be able to. Therefore, in this case, the numerical comparison unit 14 can determine that the screen 7 has a defect such as a pinhole.

  When at least RB / YIr is greater than the threshold value TH, the numerical comparison unit 14 determines that the reflected light from the screen 7 has not been obtained, and outputs the light emission amount conversion gain value LG to 0 to the command signal conversion unit 15. . On the other hand, when RB / YIr is smaller than the threshold value TH, the numerical comparison unit 14 determines that the reflected light from the screen 7 is appropriate, and outputs the light emission amount conversion gain value LG to 1 to the command signal conversion unit 15. . The operation of the command signal conversion unit 15 is the same as the operation described with reference to FIGS.

  In this embodiment, the case where the bandpass filter 38 transmits only the wavelength of the light emitted from the LD_Ir49 has been described. However, the bandpass filter 38 uses a wavelength other than the wavelength of the light emitted from the LD_Ir49. It may be permeated.

  In this embodiment, the case where invisible light for measuring the amount of received light is emitted from the light source 53 has been described. However, the light for measuring the amount of received light may be a wavelength (wavelength region) of visible light. In this case, visible light for measuring the amount of received light and video display light (red, green, blue) have different wavelengths.

  As described above, the numerical value comparison unit 14 compares the ratio RB / YIr with the threshold value TH, thereby preventing the intrusion of an obstacle on the optical path and the problem on the screen 7 as unintended light to the viewer 40 side. Detected. Therefore, it is possible to easily and accurately detect a defect on the optical path with a simple configuration. Further, when unintended light is detected, emission of unintended light is stopped, so that light is not emitted from the light source 53, and the observer 40 does not continue to view an unpleasant image.

  Since the image projection apparatus 81 of the present embodiment is configured as described above, the light quantity sensor 6 always receives the light emitted by the LD_Ir 49 as long as there is no obstacle in the optical path or there is an abnormality on the screen 7. can do. For this reason, even if the video signal IMG is at the black level, it is possible to detect an optical path defect (for example, a broken screen 7) at an early stage.

  In addition, since the light amount emitted from the LD_Ir 49 can be constant output regardless of the video signal IMG, it is possible to always ensure the constant light amount that is reflected from the screen 7 and incident on the light amount sensor 6. Therefore, the output of the reflected light or transmitted light from the LD_Ir 49 can be adjusted so that the light from the screen 7 incident on the light amount sensor 6 is sufficiently stronger than the external light incident on the light amount sensor 6. . Thereby, it is possible to reduce the influence of the light from the LD_Ir 49 received by the light amount sensor 6 from the external light.

  The bandpass filter 38 used in the light receiving sensor 6 transmits only a part of infrared light having the transmission center wavelength of LD_Ir49. For this reason, it is possible to reduce the influence of external light in the detection of reflected light, compared to the case of using the bandpass filter 38 that transmits each wavelength band of LD_r20, LD_g21, and LD_b22.

  As described above, according to the fourth embodiment, since the defect on the optical path is detected using the invisible light emitted from the light source, it is possible to reduce the influence of the light quantity sensor 6 from the external light. Therefore, it is possible to accurately detect obstacles entering the optical path and defects on the screen 7.

  In the first to fifth embodiments described above, the video signal IMG used for image display is composed of signals of three colors IMG_r, IMG_g, and IMG_b, and the light sources 3 and 53 emit three visible lights having different wavelengths. However, the video signal IMG used for image display may be a signal of two colors or less or a signal of four colors or more. The visible light emitted from the light source may be visible light having one wavelength, visible light having two different wavelengths, or visible light having four or more different wavelengths.

  As described above, the image projection apparatus and the image display apparatus according to the present invention are suitable for projecting light emitted from a light source onto a screen using a scanner.

DESCRIPTION OF SYMBOLS 1 Light emission amount command value production | generation part 2,52,62 Light emission amount command value conversion part 3,53 Light source 4,54,64 Lens part 5 Scanner 6,6a, 6b, 56 Light quantity sensor 7 Screen 8 Irradiation part 11 Light-receiving luminance correction part DESCRIPTION OF SYMBOLS 12 Light-emission luminance estimation part 13 Delay compensation part 14 Numerical comparison part 15 Command signal conversion part 16 Zero gain holding part 19a, 19b, 19c Current modulation part 38 Bandpass filter 39 Photosensor 41 Accumulation part 42a, 42b Angle correction part 47 Light emission luminance correction Unit 55 Angle detection unit 81-84 Image projection device 90, 91 Image display device L1, L2 Transmittance curve

Claims (11)

A light source in which the amount of light emitted in the visible light region is controlled by a light emission amount command value that is a command value of the light emission amount;
A light scanning unit that scans and projects the light emitted from the light source onto a screen;
A plurality of light amount sensors for detecting the amount of light transmitted from the screen side as the amount of received light;
A light emission amount command value generation unit that generates a command reference value used to generate the light emission amount command value based on an externally input video signal;
A light emission amount command value conversion unit that generates the light emission amount command value based on the received light amount and the command reference value;
An addition unit that adds the received light amounts detected by the plurality of light amount sensors and outputs the added received light amount to the emission amount command value conversion unit;
Have
In the case where the light source has received a command to emit light, the light emission amount command value conversion unit preliminarily calculates a light amount ratio that is a value obtained by dividing the added received light amount by the light emission amount of light emitted from the light source. An image projection apparatus that outputs to the light source a light emission amount command value for stopping light from the light source when the light amount ratio is smaller than the threshold value as compared with a preset threshold value.   The image projection apparatus according to claim 1, wherein the plurality of light quantity sensors are arranged symmetrically with respect to a virtual plane including a central axis of the screen and the optical scanning unit.   The light emission amount command value conversion unit calculates a light emission amount of light emitted from the light source based on the command reference value, and uses the calculated light emission amount as a light emission amount of light emitted from the light source. The image projection apparatus according to claim 1, wherein the light quantity ratio is calculated. A light source light amount detection unit that is disposed between the light source and the light scanning unit and detects a light emission amount of light emitted from the light source;
The light emission amount command value conversion unit calculates the light amount ratio using the light emission amount detected by the light source light amount detection unit as the light emission amount of light emitted from the light source. The image projection apparatus as described in any one. The optical scanning unit includes an angle detection unit that detects a scanning angle of the optical scanning unit when scanning the light as an angle in a scanning direction of the light with respect to the screen,
Based on the scanning angle, the received light quantity is corrected by normalizing the received light quantity, and outputting the corrected received light quantity to the emitted light quantity command value converter,
The image projection apparatus according to claim 1, wherein the light emission amount command value conversion unit calculates the light amount ratio using the corrected received light amount. The light emission quantity command value conversion unit, if the light emission quantity command value to stop the light from the light source is output to the light source, emission of stopping the light from the light source until a release instruction of the beam extraction stop that is an external input The image projection apparatus according to claim 1, wherein a quantity command value is continuously output to the light source.   The light source includes a plurality of laser light sources having different wavelengths, and a light combining unit that combines light emitted from the plurality of laser light sources. The image projection apparatus described. The light amount sensor includes a bandpass filter that selectively transmits light in a predetermined wavelength band, and detects the amount of light transmitted through the bandpass filter as a received light amount.
The image projection apparatus according to claim 7, wherein a transmission band of the band pass filter includes a wavelength band of light emitted from the plurality of laser light sources. It further has an invisible laser beam source that emits a constant amount of light regardless of an externally input video signal ,
The laser light source emits light having a wavelength in an invisible light region,
The light amount sensor includes a bandpass filter that selectively transmits light in a predetermined wavelength band, and detects the amount of light transmitted through the bandpass filter as a received light amount.
The image projection apparatus according to claim 7, wherein a transmission band of the band-pass filter includes a wavelength of the invisible light region and does not include a wavelength band of light emitted from the plurality of laser light sources.   The image projection apparatus according to claim 1, wherein the light emission amount command value conversion unit operates according to a pixel clock of the video signal. A screen to display an image;
A light source in which the amount of light emitted in the visible light region is controlled by a light emission amount command value that is a command value of the light emission amount
A light scanning unit that scans and projects the light emitted from the light source onto the screen;
A plurality of light amount sensors for detecting the amount of light transmitted from the screen side as the amount of received light;
A light emission amount command value generation unit that generates a command reference value used to generate the light emission amount command value based on an externally input video signal;
A light emission amount command value conversion unit that generates the light emission amount command value based on the received light amount and the command reference value;
An addition unit that adds the received light amounts detected by the plurality of light amount sensors and outputs the added received light amount to the emission amount command value conversion unit;
Have
In the case where the light source has received a command to emit light, the light emission amount command value conversion unit preliminarily calculates a light amount ratio that is a value obtained by dividing the added received light amount by the light emission amount of light emitted from the light source. An image display device that outputs a light emission amount command value for stopping light from the light source to the light source when the light amount ratio is smaller than the threshold value as compared with a preset threshold value.

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