JP2008102305A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of achieving high color reproducibility while reducing the cost of manufacture. <P>SOLUTION: The display device includes: LEDs 12R, 12G, 12B as a light source unit supplying light; spatial light modulation devices 14R, 14G, 14B modulating the light from the light source unit responding to image signals; a light sensor 26 as a measuring unit measuring the intensity of light from the spatial light modulation devices in a given period while the light modulated corresponding to image signals are exiting; and an adjusting unit 23 adjusting the intensity of light from the spatial light modulating devices by controlling driving of at least one of the light source unit and the spatial light modulation devices based on the measurement results by the measuring unit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device, and more particularly to a technology of an image display device that displays an image using light modulated in accordance with an image signal.

  Solid-state light sources, especially light-emitting diode elements (LEDs), are expected to be used in image display devices because of their small size, instant lighting and extinction, high color purity, and long life. ing. An LED is known to have a property that the light emission intensity easily changes depending on the temperature change of the element. Since the amount of heat generated by the element increases as the lighting time elapses, it becomes difficult to display an image with a stable amount of light. Moreover, since the structure and material of LED differ for every color light, the temperature dependence of emitted light intensity changes for every color light to generate. If the intensity of light changes to a different degree for each color, the color balance of the image is lost, leading to a decrease in color reproducibility. For this reason, especially when using each LED for red (R), green (G), and blue (B), it becomes difficult to maintain high color reproducibility with progress of lighting time. On the other hand, conventionally, a technique for maintaining high color reproducibility by detecting illumination light and controlling the light source according to the detection result has been proposed (for example, see Patent Document 1).

JP 2004-317800 A

  Patent Document 1 proposes a technique for detecting illumination light using a photoelectric conversion element provided on the outer periphery of a display area of a spatial light modulator. If a photoelectric conversion element is added to a region other than the display region of the spatial light modulator, the manufacturing process becomes complicated, the time required for the manufacturing increases, the yield decreases, and the like. For this reason, manufacturing cost will increase compared with the case where the conventional spatial light modulator is used. In addition, since the illumination light is detected only at the outer periphery of the display area, the measurement value may vary depending on the mechanical accuracy of the illumination optical system. When the measured value fluctuates, accurate control of the light source becomes difficult.

  The characteristics of the spatial light modulator, for example, the transmittance characteristics of the liquid crystal display device may change depending on the temperature. The decrease in color reproducibility is caused not only by the temporal change of the emission intensity by the light source but also by the temporal change of the spatial light modulator. When the photoelectric conversion element provided in the spatial light modulation device is used, it cannot cope with a decrease in color reproducibility due to a temporal change of the spatial light modulation device. Furthermore, by providing the photoelectric conversion element in the spatial light modulator, the temperature of the photoelectric conversion element itself increases. For this reason, the structure for correct | amending the measurement shift resulting from the temperature characteristic of a photoelectric conversion element is needed. As described above, according to the conventional technique, there arises a problem that the manufacturing cost can be reduced and it is difficult to realize high color reproducibility. The present invention has been made in view of the above-described problems, and an object thereof is to provide an image display device that can reduce the manufacturing cost and realize high color reproducibility.

  In order to solve the above-described problems and achieve the object, according to the present invention, a light source unit that supplies light, a spatial light modulation device that modulates light from the light source unit according to an image signal, and an image signal A measurement unit that measures the intensity of light from the spatial light modulation device within a fixed period during which the modulated light is emitted, and at least the light source unit and the spatial light modulation device based on the measurement result by the measurement unit It is possible to provide an image display device including an adjustment unit that adjusts the intensity of light from the spatial light modulation device by controlling one of the drives.

  The adjustment unit corrects the color balance of the image by adjusting the intensity of the plurality of color lights from the spatial light modulation device. The adjustment of the light intensity by the adjustment unit is performed within a certain period during display of an image, for example, within one frame period. By adjusting according to the intensity of light from the spatial light modulator, it is possible to maintain high color reproducibility even when the spatial light modulator as well as the light source section changes over time. Since the measurement unit for measuring the intensity of light can be installed outside the spatial light modulation device, the manufacturing cost can be reduced as compared with the case where the measurement unit is provided in the spatial light modulation device. For example, by detecting leakage light that travels in a direction other than the direction of the projection optical system from the spatial light modulator, the measurement unit can calculate the average intensity of light for the entire screen. In addition, the measurement unit can measure the light intensity near the center of the optical path by moving the measurement unit in the optical path of the light from the spatial light modulation device within a certain period of time during which measurement is performed. The light near the center of the optical path has a great influence on the state of the image. By performing highly effective measurement in this way, the color balance of the image can be accurately adjusted. Furthermore, by installing a measurement unit outside the spatial light modulation device, it is possible to eliminate the need for correction of measurement deviation caused by the temperature rise of the measurement unit. Thereby, it is possible to obtain an image display device that can reduce the manufacturing cost and can realize high color reproducibility.

  As a preferred aspect of the present invention, the spatial light modulation device is switched from the first state controlled according to the image signal to the second state controlled according to another signal other than the image signal. The measurement unit preferably measures the intensity of light from the spatial light modulation device in the second state. The spatial light modulation device is controlled in accordance with a control signal that makes the gradation of the entire screen constant, for example, in the second state. Thereby, it is possible to correct the color balance using the measurement result in a predetermined state such as making the gradation of the entire screen constant. By shortening the period during which the spatial light modulation device is in the second state, it is possible to reduce the effect on image viewing.

  As a preferred aspect of the present invention, the spatial light modulation device is controlled so that the gradation of the entire screen in the second state substantially matches the average value of the gradation of the entire screen in the first state. It is desirable. The flickering of the image can be reduced by making the average value of the gradation in the first state substantially coincide with the gradation of the entire screen in the second state.

  Moreover, as a preferable aspect of the present invention, it is desirable that the measurement unit measures the intensity of light modulated according to the image signal. Since the measurement is performed in parallel with the display of the image without setting the spatial light modulation device in the state for measurement, it is possible to reduce the influence on the image viewing.

  Moreover, as a preferable aspect of the present invention, it is desirable that the adjustment unit adjusts the intensity of light from the spatial light modulator according to the average intensity of light emitted from the spatial light modulator. The drive control of the light source unit or the spatial light modulator is performed based on the difference between the average light intensity calculated based on the image signal and the average light intensity measured by the measurement unit. As a result, the color balance of the image can be corrected.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a moving unit that moves the measuring unit in and out of the optical path of the light from the spatial light modulator. Thereby, it can adjust based on the intensity | strength of the light measured in the arbitrary positions in the optical path of the light from a spatial light modulator. By measuring the light intensity in the optical path of the light from the spatial light modulator, measurement with high accuracy can be performed. Thereby, the color balance can be adjusted with high accuracy. By shortening the period during which the measurement unit is placed in the optical path as much as possible, the influence on image viewing can be reduced.

  As a preferred aspect of the present invention, it is desirable that the moving unit moves the measuring unit to a plurality of positions in the optical path of light from the spatial light modulation device. By moving the measurement unit to a plurality of positions, the measurement unit can measure the light intensity at the plurality of positions. By performing adjustment based on the measurement results at a plurality of positions, the accuracy of color balance adjustment can be improved. Further, the intensity of light from the spatial light modulation device can be adjusted for each area based on the measurement result at each position.

  Moreover, as a preferable aspect of the present invention, a projection lens that projects light from the spatial light modulator is provided, and the moving unit moves the measurement unit to the image plane in the projection lens or in the vicinity of the image plane. desirable. By measuring the light at or near the image plane in the projection lens, the average intensity of the light emitted from the spatial light modulator can be measured. Further, by measuring the light intensity at the position where the light is concentrated, measurement with high accuracy can be performed.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a projector 10 that is an image display apparatus according to Embodiment 1 of the present invention. The projector 10 is a front projection type projector that projects light onto a screen and observes an image by observing light reflected on the screen. The projector 10 includes a red (R) light illumination device 11R, a green (G) light illumination device 11G, and a blue (B) light illumination device 11B.

  FIG. 2 shows a schematic configuration of the R light illumination device 11R. The LED 12R for R light is a solid light source that supplies R light. The field lens 13 collimates the light beam from the R light LED 12R. Returning to FIG. 1, the R light spatial light modulation device 14 </ b> R is a transmissive liquid crystal display device that modulates the R light from the R light illumination device 11 </ b> R according to an image signal. As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used. The R light modulated by the R light spatial light modulator 14R is incident on the cross dichroic prism 15 which is a color synthesis optical system.

  Both the G light illumination device 11G and the B light illumination device 11B have the same configuration as the R light illumination device 11R. The G light LED 12G of the G light illumination device 11G is a solid-state light source that supplies G light. The G light spatial light modulator 14G is a transmissive liquid crystal display device that modulates the G light from the G light illumination device 11G according to an image signal. The G light modulated by the G light spatial light modulator 14 G is incident on the cross dichroic prism 15.

  The B light LED 12B of the B light illumination device 11B is a solid-state light source that supplies B light. The B light spatial light modulator 14B is a transmissive liquid crystal display device that modulates the B light from the B light illumination device 11B in accordance with an image signal. The B light modulated by the B light spatial light modulator 14 </ b> B enters the cross dichroic prism 15. Note that each of the illumination devices 11R, 11G, and 11B may be provided with a uniformizing optical system that uniformizes the intensity distribution of the light beam, such as a rod integrator, a fly-eye lens, and a superimposing lens.

  The cross dichroic prism 15 has two dichroic films 16 and 17 arranged so as to be substantially orthogonal to each other. The first dichroic film 16 reflects R light and transmits G light and B light. The second dichroic film 17 reflects B light and transmits R light and G light. The cross dichroic prism 15 combines R light, G light, and B light incident from different sides, and emits the light toward the projection lens 18. The projection lens 18 projects the light from the cross dichroic prism 15 onto a screen (not shown).

  The projector 10 is not limited to using a transmissive liquid crystal display device. As the spatial light modulator, a reflective liquid crystal display (Liquid Crystal On Silicon; LCOS), DMD (Digital Micromirror Device), GLV (Grating Light Valve), or the like may be used. Further, the present invention is not limited to the case where the spatial light modulation device provided for each color light is used, and may be configured to perform modulation by a color sequential method that sequentially supplies each color light to the common spatial light modulation device. The projector 10 is not limited to the case where an LED is used as the light source unit. As the light source unit, for example, a solid light source other than the LED, or a lamp such as an ultrahigh pressure mercury lamp may be used.

  The control device 20 including a microcomputer or the like controls the driving of the illumination devices 11R, 11G, and 11B and the spatial light modulation devices 14R, 14G, and 14B. Image signals from external devices such as a computer, a DVD player, and a TV tuner are input to the image signal processing unit 21 of the control device 20. The image signal processing unit 21 performs image resizing, gamma adjustment, color adjustment, and the like by characteristic correction and amplification of the image signal. Further, the image signal processing unit 21 decomposes the image signal into R, G, and B video data. The spatial light modulation signal generation unit 22 generates a spatial light modulation signal for driving the spatial light modulation devices 14R, 14G, and 14B based on the video data from the image signal processing unit 21. Each of the spatial light modulation devices 14R, 14G, and 14B is driven according to the spatial light modulation signal from the spatial light modulation signal generation unit 22.

  The optical sensor 26 is a measuring unit that measures the intensity of light from the spatial light modulators 14R, 14G, and 14B. As the optical sensor 26, for example, a photodiode which is a photoelectric conversion element can be used. The optical sensor 26 is provided outside the optical path of light traveling from the cross dichroic prism 15 to the projection lens 18 and at a position where leakage light from the cross dichroic prism 15 enters. Here, the leakage light refers to light that travels away from the ideal optical path due to irregular reflection in an optical component or the like. By disposing the optical sensor 26 on the exit side of the cross dichroic prism 15, it is possible to measure the intensities of the R light, G light, and B light after being combined by the cross dichroic prism 15.

  In the present embodiment, for example, the optical sensor 26 is disposed at a position where leakage light for the entire screen is incident. Thereby, the average intensity of light for the entire screen can be calculated. By performing highly effective measurement in this way, the color balance of the image can be accurately adjusted. By adopting a configuration in which the optical sensor 26 is installed outside the spatial light modulators 14R, 14G, and 14B, the manufacturing cost can be reduced as compared with the case where the optical sensor 26 is provided in the spatial light modulators 14R, 14G, and 14B. Further, by installing the optical sensor 26 outside the spatial light modulators 14R, 14G, and 14B, it is possible to eliminate the need for correction of measurement deviation caused by the temperature increase of the optical sensor 26. Furthermore, since leak light having a relatively low intensity is incident on the optical sensor 26, an increase in temperature of the optical sensor 26 can be reduced.

  The optical sensor 26 needs to be able to measure each intensity of R light, G light, and B light. The optical sensor 26 has an R light filter that transmits only R light, a G light filter that transmits only G light, and a B light filter that transmits only B light. By providing each filter, the optical sensor 26 can simultaneously measure the intensity of each color light. In addition, the intensity of each color light may be sequentially measured by sequentially emitting R light, G light, and B light during measurement by the optical sensor 26. The optical sensor 26 desirably has a sensitivity close to human visibility with respect to R light, G light, and B light.

  The optical sensor driving unit 25 drives the optical sensor 26 by supplying current to the optical sensor 26. The optical sensor driving unit 25 includes a current-voltage conversion circuit, an amplifier circuit, and an AD converter. The current-voltage conversion circuit converts the amount of change in current in the optical sensor 26 into a voltage value. The amplifier circuit amplifies the output from the optical sensor 26 according to the measurement level. The amplification factor in the amplifier circuit is adjusted in accordance with an output from the adjusting unit 23 described later. The AD converter converts the output from the optical sensor 26 into a digital value. The measurement result by the optical sensor 26 is input as digital data from the optical sensor driving unit 25 to the adjusting unit 23.

  The adjustment unit 23 generates a light source drive signal based on the result of measurement by the optical sensor 26 that is a measurement unit. Each of the light source driving units 24R, 24G, and 24B supplies current, power, or voltage that is modulated in accordance with the light source driving signal from the adjustment unit 23. The R light source drive unit 24R drives the R light LED 12R according to the light source drive signal from the adjustment unit 23. The G light source drive unit 24G drives the G light LED 12G according to the light source drive signal from the adjustment unit 23. The B light source drive unit 24 </ b> B drives the B light LED 12 </ b> B according to the light source drive signal from the adjustment unit 23. The adjustment unit 23 feedback-controls the driving of the LEDs 12R, 12G, and 12B that are the light source units based on the light source drive signal.

  When the adjustment of the light intensity is started, each of the spatial light modulators 14R, 14G, and 14B is switched from the normal display mode to the adjustment mode for adjusting the light intensity. The display mode is a first state controlled according to the image signal. The adjustment mode is a second state controlled in accordance with a control signal from the adjustment unit 23 that is a signal other than the image signal. The optical sensor 26 as a measurement unit measures the intensity of light from the spatial light modulators 14R, 14G, and 14B in the adjustment mode.

  The adjustment unit 23 outputs a control signal for switching the spatial light modulation devices 14R, 14G, and 14B to the adjustment mode to the spatial light modulation signal generation unit 22. The spatial light modulation signal generation unit 22 outputs an adjustment signal for changing each of the spatial light modulation devices 14R, 14G, and 14B to the adjustment mode according to the control signal from the adjustment unit 23. Each of the spatial light modulation devices 14R, 14G, and 14B is driven according to the adjustment signal from the spatial light modulation signal generation unit 22.

  FIG. 3 is a flowchart showing a procedure for adjusting the intensity of light from each of the spatial light modulators 14R, 14G, and 14B by the adjusting unit 23. In step S1, each of the spatial light modulators 14R, 14G, and 14B is set to the adjustment mode according to the adjustment signal. As shown in the timing chart of FIG. 4, the adjustment signal is input in one frame period between periods in which image signals are input as spatial light modulation signals. By the adjustment signal, for example, driving for displaying the maximum gradation of 255 gradations is performed for the entire screen. By setting each color light to 255 gradations, the entire screen is displayed in white.

  Next, in step S <b> 2, each intensity of R light, G light, and B light is measured by the optical sensor 26. Measurement by the optical sensor 26 is performed in response to the supply of current from the optical sensor driving unit 25 to the optical sensor 26. Supply of current from the optical sensor driving unit 25 to the optical sensor 26 is controlled by the adjusting unit 23. The optical sensor 26 measures the intensity of light within one frame period, which is a certain period during which light modulated according to the image signal is emitted. As shown in FIG. 4, the measurement of the light intensity by the optical sensor 26 is performed at a timing as late as possible in one frame period in which each of the spatial light modulators 14R, 14G, and 14B is driven according to the adjustment signal. Thereby, each spatial light modulator 14R, 14G, 14B can measure after the transmittance | permeability fully stabilized according to the signal for adjustment, and can measure the intensity | strength of each color light correctly.

  The LEDs 12R, 12G, and 12B that are the light source units are controlled by the control value A in the normal display mode before that while the spatial light modulators 14R, 14G, and 14B are in the adjustment mode. In this case, adjustment based on the intensity of each color light when each LED 12R, 12G, 12B is controlled by the control value A can be performed. In addition, while the spatial light modulators 14R, 14G, and 14B are in the adjustment mode, the LEDs 12R, 12G, and 12B may be controlled with control values that are appropriately set according to the purpose of adjustment. While each of the spatial light modulators 14R, 14G, and 14B is in the adjustment mode, the transmittance of each of the spatial light modulators 14R, 14G, and 14B is set to a state that displays the maximum gradation of 255 gradations. By setting each color light to 255 gradations, the entire screen is displayed in white.

  Next, in step S3, correction values for the LEDs 12R, 12G, and 12B are calculated. As shown in FIG. 4, the correction value is calculated immediately after the measurement by the optical sensor 26. For example, as shown in FIG. 5, it is assumed that the voltage reference values for R, G, and B in white display are set to 1.000, 4.591, and 0.060 (arbitrary units; the same applies hereinafter). The voltage reference value varies depending on the white color temperature used for the setting. The setting conditions such as the white color temperature used for the setting are input to the adjustment unit 23 as shown in FIG.

  Assume that the measured values for R, G, and B measured in step S2 are 1.000, 5.050, and 0.060, respectively. When these are compared, the measured values of R and B are the same as the reference value, while the measured value of G is approximately 10% higher than the reference value. From this result, the adjustment unit 23 calculates the current value when the intensity of the G light is reduced by approximately 10% as a correction value. When the light intensity and the current value are in a linear relationship, a current value obtained by reducing the current value before adjustment by about 10% is set as the correction value. The correction value is output as the pulse width of a pulse width modulation (PWM) signal, for example. The relationship between the intensity of each color light and the current value is stored as, for example, the adjustment unit 23 as initial data. Data on the relationship between the intensity of each color light and the current value is updated as needed.

  In step S4, the driving of the LEDs 12R, 12G, and 12B is controlled in accordance with the light source driving signal from the adjusting unit 23. A light source drive signal for each of the LEDs 12R, 12G, and 12B is generated based on the correction value calculated in step S3. Each LED 12R, 12G, 12B is controlled with a control value B different from the control value A by adjustment. The control value B is set so that the intensity of the G light is approximately 10% smaller than that of the control value A. Here, since the setting of the transmittance of each of the spatial light modulators 14R, 14G, and 14B is not changed, the transmittance of each of the spatial light modulators 14R, 14G, and 14B is kept at the setting A before adjustment. The When the measurement in step S2 is performed immediately before switching to the next frame, the calculation of the correction value in step S3 may be performed in the frame next to the frame in which the measurement has been performed.

  The intensity of light from each of the spatial light modulators 14R, 14G, and 14B is adjusted by controlling the driving of the LEDs 12R, 12G, and 12B. The color balance of the image is corrected by adjusting the intensity of each color light. When it can be predicted that the change in the color balance is mainly due to the temporal change of the LEDs 12R, 12G, and 12B, the high color reproducibility can be maintained by controlling the driving of the LEDs 12R, 12G, and 12B. The adjustment described above can be performed about once every time the projector 10 performs image display for one minute, for example. If it is about once in one minute of image display, the color balance can be adjusted with little influence on image viewing. The frequency of performing such adjustment is stored in the adjustment unit 23, for example. Further, the frequency of adjustment can be appropriately changed by inputting setting conditions.

  During measurement by the optical sensor 26, the driving of the LEDs 12R, 12G, and 12B may be appropriately controlled. For example, when the intensity of each color light is changed according to the setting by the user or the content of the image, the driving of each LED 12R, 12G, 12B can be controlled according to the purpose. By performing measurement when controlling the driving of the LEDs 12R, 12G, and 12B, it is possible to adjust the color balance when changing the intensity of each color light according to the purpose.

  FIG. 6 is a flowchart showing another procedure for adjusting the intensity of light from each of the spatial light modulators 14R, 14G, and 14B by the adjusting unit 23. In the procedure shown in FIG. 3, measurement is performed while displaying white, whereas here, measurement is performed while displaying white and displaying black. In step S11, as in step S1 shown in FIG. 3, each of the spatial light modulators 14R, 14G, and 14B performs driving for displaying the maximum gradation of 255 gradations. By setting each color light to 255 gradations, the entire screen is displayed in white. In step S12, each intensity of R light, G light, and B light is measured as in step S2.

  Next, in step S13, each of the spatial light modulators 14R, 14G, and 14B performs driving for displaying 0 gradation which is the lowest gradation for the entire screen. By setting each color light to 0 gradation, the entire screen is displayed in black. In step S14, each intensity of R light, G light, and B light is measured by the optical sensor 26. In step S15, correction values for the LEDs 12R, 12G, and 12B are calculated based on the measurement results in steps S12 and S14.

  For example, as shown in FIG. 7, the voltage reference values for R, G, and B in white display are 1.000, 4.591, and 0.060, respectively, while the measured value in white display is 1.000. , 5.050, and 0.060. Moreover, while the voltage reference values of R, G, and B in black display are 0.01000, 0.04591, and 0.00060, respectively, the measurement values in black display are 0.01000, 0.0505050, and 0.005. Suppose that it is 0,060.

  When these are compared, the measured values of R and B are the same as the reference values in both the white display and the black display, whereas the measured values of G are the reference values in both the white display and the black display. About 10% higher. From this result, the adjustment unit 23 calculates the current value when the intensity of the G light is reduced by approximately 10% as a correction value. In step S <b> 16, the driving of the LEDs 12 </ b> R, 12 </ b> G, and 12 </ b> B is controlled according to the light source driving signal from the adjustment unit 23.

  FIG. 8 is a flowchart showing still another procedure for adjusting the intensity of light from each of the spatial light modulators 14R, 14G, and 14B by the adjusting unit 23. In the procedure shown in FIG. 3 and the procedure shown in FIG. 6, the intensity of light from each of the spatial light modulators 14R, 14G, and 14B is adjusted by controlling the LEDs 12R, 12G, and 12B. On the other hand, here, the intensity of light from each of the spatial light modulators 14R, 14G, and 14B is adjusted by changing the setting of the transmittance of each of the spatial light modulators 14R, 14G, and 14B.

  In step S21, as in step S1 shown in FIG. 3, each of the spatial light modulation devices 14R, 14G, and 14B performs driving for displaying 255 gradations. In step S22, each intensity of R light, G light, and B light is measured as in step S2. In step S23, as in step S13 shown in FIG. 6, each of the spatial light modulators 14R, 14G, and 14B performs driving for displaying 0 gradation. In step S24, each intensity of R light, G light, and B light is measured as in step S14. In step S25, correction values for the spatial light modulators 14R, 14G, and 14B are calculated based on the measurement results in steps S22 and S24.

  For example, as shown in FIG. 9, the voltage reference values for R, G, and B in white display are 1.000, 4.591, and 0.060, respectively, while the measured value in white display is 1.000. , 5.050, and 0.060. Further, it is assumed that the voltage reference values for R, G, and B in black display and the measured values in black display are 0.01000, 0.04591, and 0.00060, respectively. When these are compared, the measured values of R and B are the same as the reference values in both the white display and the black display. The measured value of G is the same as the reference value in black display, and is approximately 10% higher than the reference value in white display.

  From the measurement result of the intensity of G light at the 255th gradation and the 0th gradation, the spatial light modulation device 14G for G light gradually increases in intensity from the 0th gradation to the 255th gradation from the reference value as shown in FIG. It can be inferred that the characteristic is From this result, the adjusting unit 23 gives a correction value of the driving voltage for the G light spatial light modulator 14G so that the transmittance of the liquid crystal is gradually lowered from the 0th gradation to the 255th gradation than before the adjustment. calculate.

  In step S26, the setting of the transmittance of each of the spatial light modulators 14R, 14G, and 14B is changed according to the output from the adjustment unit 23. The spatial light modulation signal generation unit 22 generates a spatial light modulation signal corrected using the correction value calculated by the adjustment unit 23. In this way, the adjusting unit 23 adjusts the intensity of light from each of the spatial light modulators 14R, 14G, and 14B by controlling the driving of each of the spatial light modulators 14R, 14G, and 14B.

  The procedure shown in FIG. 6 and the procedure shown in FIG. 8 are performed when it is unclear whether the change in color balance is due to the temporal change of the LEDs 12R, 12G, and 12B or the temporal change of the spatial light modulators 14R, 14G, and 14B. Useful. The projector 10 is not limited to adjusting only one of the LEDs 12R, 12G, and 12B and the spatial light modulators 14R, 14G, and 14B. Both the LEDs 12R, 12G, and 12B and the spatial light modulators 14R, 14G, and 14B may be adjusted according to the measurement result by the optical sensor 26.

  For example, the correction values for the LEDs 12R, 12G, and 12B are first calculated in accordance with the measurement result of the optical sensor 26. Further, correction values for the spatial light modulators 14R, 14G, and 14B are calculated in accordance with the color balance shift that cannot be eliminated only by adjusting the LEDs 12R, 12G, and 12B. Accordingly, the color balance can be corrected even when the change in the color balance is due to the temporal change of the LEDs 12R, 12G, and 12B and the spatial light modulators 14R, 14G, and 14B.

  In the projector 10 of the present invention, not only the LEDs 12R, 12G, and 12B but also the spatial light modulators 14R, 14G, and 14B are changed with time by adjustment according to the intensity of light from the spatial light modulators 14R, 14G, and 14B. Even in this case, high color reproducibility can be maintained. As described above, the manufacturing cost can be reduced and high color reproducibility can be realized. High contrast can also be maintained by adjustment according to the intensity of light from the spatial light modulators 14R, 14G, and 14B.

  The correction value calculated by the adjustment unit 23 is preferably reflected in stages, not at once for driving the LEDs 12R, 12G, 12B and the spatial light modulators 14R, 14G, 14B. By changing the current value to the correction value in stages using, for example, a plurality of frames of 1 to several seconds, it is possible to reduce a sense of incongruity such as flicker.

  In the adjustment mode, it is not limited to the case where the highest gradation and the lowest gradation are set for the entire screen. The gradation in the adjustment mode is arbitrary. For example, in addition to white and black, each color light may be measured in a gray display of 128 gradations which is an intermediate gradation. By measuring many gradations, the accuracy of color balance adjustment can be increased. In addition, for example, when a measurement error is likely to occur in the case of 0 gradation black display, gray display close to black may be performed instead of black display. Thereby, the precision of color balance adjustment can be improved. In the case where R light, G light, and B light are sequentially emitted and measurement of each color light is performed sequentially, display of, for example, 255 gradations of R, G, and B is sequentially performed. In this case, each of the LEDs 12R, 12G, and 12B is controlled to stop emitting color light other than the color light to be measured.

  Further, the spatial light modulators 14R, 14G, and 14B are configured so that the gradation of the entire screen in the adjustment mode substantially matches the average value of the gradation of the entire screen in at least one of the immediately preceding display mode and the immediately following display mode. It is good also as being controlled by. For example, if an image with 100 gradations 50% and 120 gradations 50% is displayed for each color light in the display mode immediately before the adjustment mode, the entire screen has 110 gradations for each color light in the adjustment mode. . By making the average value of the gradation in the display mode substantially coincide with the gradation of the entire screen in the adjustment mode, it is possible to reduce image flicker.

  The optical sensor 26 is not limited to measuring the intensity of light from the spatial light modulation devices 14R, 14G, and 14G in the adjustment mode switched from the display mode. The optical sensor 26 may measure the intensity of light modulated according to the image signal, that is, measure the intensity of light from the spatial light modulators 14R, 14G, and 14G in the display mode. In this case, control of the spatial light modulators 14R, 14G, and 14B for switching between the display mode and the adjustment mode is unnecessary. Since the spatial light modulators 14R, 14G, and 14B are measured in parallel with the display of the image without making the state for measurement, the influence on the image viewing can be reduced.

  When measuring the intensity of the light modulated according to the image signal, the adjustment unit 23 adjusts the spatial light modulators 14R, 14G, 14B according to the average intensity of the light emitted from the spatial light modulators 14R, 14G, 14B. The intensity of light from the can be adjusted. Control of driving of the LEDs 12R, 12G, 12B or the spatial light modulators 14R, 14G, 14B based on the difference between the average intensity of the light calculated based on the image signal and the average intensity of the light measured by the optical sensor 26 I do. As a result, the color balance of the image can be corrected.

  Moreover, it is good also as determining the timing which measures the intensity | strength of light according to an image signal. For example, a display in which the entire screen is white, black, or a color similar to these (light gray or dark gray) appears relatively frequently in normal video images and television images. The timing for making the entire screen white or black can be detected by analyzing the image signal. Since these displays usually last several frames, it is possible to measure the light intensity after detecting such timing. By measuring the light intensity using these timings, the adjustment can be performed in the same manner as when the control for switching to the adjustment mode is performed.

  The optical sensor 26 is not limited to measuring the intensity of leaked light for the entire screen, and may measure the intensity of leaked light for a part of the entire screen. In this case, the color balance can be corrected for the range in which the intensity of leakage light is measured. There may be a plurality of optical sensors 26. In this case, the adjustment may be performed on the entire screen collectively based on the measurement result of each optical sensor 26, or the adjustment may be performed for each area of the screen. Further, an optical element for condensing leakage light on the optical sensor 26 may be provided as long as it does not affect the image display.

  The optical sensor 26 is not limited to being provided on the exit side of the cross dichroic prism 15. The optical sensor 26 only needs to be able to measure the intensity of light from the spatial light modulators 14R, 14G, and 14B, and may be provided at least on the emission side from the spatial light modulators 14R, 14G, and 14B.

  FIG. 11 shows a schematic configuration of a projector 30 that is an image display apparatus according to Embodiment 2 of the present invention. The projector 30 of the present embodiment includes a motor 31 that is a moving unit. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The motor 31 is a stepping motor that rotates in predetermined step units.

  FIG. 12 illustrates a portion where the optical sensor 26 and the motor 31 are provided. FIG. 13 shows a state in which a portion where the optical sensor 26 and the motor 31 are provided is viewed from the projection lens 18 side. One end of an arm 32 is connected to the motor 31. The optical sensor 26 is attached to the opposite end of the both ends of the arm 32 to the end connected to the motor 31. With the rotation of the motor 31, the optical sensor 26 moves between the position P1 and the position P0. The position P1 is a position facing the center of the exit surface of the cross dichroic prism 15. The position P1 is in the optical path of the light from the spatial light modulators 14R, 14G, and 14B.

  The position P0 is a position above the exit surface of the cross dichroic prism 15. The position P0 is outside the optical path of the light from the spatial light modulators 14R, 14G, and 14B. The motor 31 moves the optical sensor 26 between the optical path of the light from the spatial light modulators 14R, 14G, and 14B and the outside of the optical path. Further, since the light from the spatial light modulators 14R, 14G, and 14B spreads away from the cross dichroic prism 15, it is desirable that the motor 31 can move the optical sensor 26 to a position as close to the cross dichroic prism 15 as possible.

  In the normal display mode, the optical sensor 26 is placed at the position P0. The motor 31 moves the optical sensor 26 from the position P0 to the position P1 immediately before the optical sensor 26 measures light. Then, immediately after the optical sensor 26 measures light, the motor 31 moves the optical sensor 26 from the position P1 to the position P0. By measuring in the optical path of the light from the spatial light modulators 14R, 14G, and 14B, the light from the spatial light modulators 14R, 14G, and 14B can be accurately detected. In addition, by making it possible to detect light with high intensity, a high S / N ratio can be realized, and highly accurate correction can be performed.

  The light in the vicinity of the center of the optical path greatly affects the state of the image. By performing highly effective measurement in this way, the color balance of the image can be accurately adjusted. Since light is incident on the optical sensor 26 instantaneously, correction of measurement deviation caused by the temperature rise of the optical sensor 26 can be eliminated. Thereby, manufacturing cost can be reduced and high color reproducibility can be realized. By setting the optical sensor 26 in the optical path to be as short as possible, for example, about one frame period, the influence on image viewing can be reduced.

  In the normal display mode, the motor 31 may move the optical sensor 26 to a position P0 'below the exit surface of the cross dichroic prism 15. In addition to reciprocating the optical sensor 26 between the position P0 and the position P1, the motor 31 may reciprocate the optical sensor 26 between the position P1 and the position P0 '. Further, the motor 31 may reciprocate the optical sensor 26 between the position P0 and the position P0 '. In this case, light can be measured while the optical sensor 26 moves from the position P0 to the position P0 'and while the optical sensor 26 moves from the position P0' to the position P0.

  The motor 31 may move the optical sensor 26 to a plurality of positions in the optical path of the light from the spatial light modulators 14R, 14G, and 14B. For example, the motor 31 may move the optical sensor 26 at three positions P2, P1, P2 'in the optical path and a position P0 outside the optical path. The positions P2, P1, and P2 'correspond to the upper part, the center, and the lower part of the exit surface of the cross dichroic prism 15, respectively.

  At the position P2, the optical sensor 26 mainly measures the light emitted from the upper part of the emission surface of the cross dichroic prism 15. At the position P1, the optical sensor 26 mainly measures light emitted from the center of the emission surface of the cross dichroic prism 15. At the position P <b> 2 ′, the optical sensor 26 mainly measures light emitted from the lower part of the emission surface of the cross dichroic prism 15. By performing adjustment based on the measurement results at a plurality of positions, the accuracy of color balance adjustment can be improved.

  Moreover, it is good also as adjusting the intensity | strength of the light from spatial light modulator 14R, 14G, 14B for every area based on the measurement result in each position. The position of the optical sensor 26 when measuring light can be appropriately changed according to the configuration and driving of the motor 31 and the arm 32. Thereby, it can adjust based on the intensity | strength of the light measured in the arbitrary positions in the optical path of the light from spatial light modulator 14R, 14G, 14B.

  FIG. 14 illustrates a first modification of the second embodiment. The motor 41 used in this modification is a linear motor that performs linear motion. The motor 41 is a moving unit that moves the optical sensor 26. The arm 42 is provided through the motor 41. The arm 42 moves in the horizontal direction by driving the motor 41. The optical sensor 26 is attached to one end of the arm 42.

  FIG. 15 shows a state where the portion where the optical sensor 26 and the motor 41 are provided is viewed from the projection lens 18 side. By driving the motor 41, the optical sensor 26 moves between the position P4 and the position P3. The position P4 is a position facing the center of the exit surface of the cross dichroic prism 15. The position P4 is in the optical path of the light from the spatial light modulators 14R, 14G, and 14B. The position P3 is a position on the left side of the exit surface of the cross dichroic prism 15. The position P3 is outside the optical path of the light from the spatial light modulators 14R, 14G, and 14B. The motor 41 moves the optical sensor 26 between the optical path of the light from the spatial light modulators 14R, 14G, and 14B and the outside of the optical path.

  In the normal display mode, the optical sensor 26 is placed at the position P3. The motor 41 moves the optical sensor 26 from the position P3 to the position P4 immediately before the optical sensor 26 measures light. Then, immediately after the light sensor 26 measures light, the motor 41 moves the light sensor 26 from the position P4 to the position P3. Also in the case of this modification, it is possible to measure with high accuracy by measuring the light with the optical sensor 26 moved to the approximate center of the optical path of the light from the spatial light modulators 14R, 14G, 14B.

  The motor 41 may move the optical sensor 26 to a position P3 'on the right side of the exit surface of the cross dichroic prism 15 in the normal display mode. The motor 41 may reciprocate the optical sensor 26 between the position P4 and the position P3 'in addition to reciprocating the optical sensor 26 between the position P3 and the position P4. Further, the motor 41 may reciprocate the optical sensor 26 between the position P3 and the position P3 '. In this case, light can be measured while the optical sensor 26 moves from the position P3 to the position P3 'and while the optical sensor 26 moves from the position P3' to the position P3.

  Also in this modification, the motor 41 may move the optical sensor 26 to a plurality of positions in the optical path of the light from the spatial light modulators 14R, 14G, and 14B. For example, the motor 41 may move the optical sensor 26 at three positions P5, P4, P5 'in the optical path and a position P3 outside the optical path. The positions P5, P4, and P5 'correspond to the left part, the center, and the right part of the exit surface of the cross dichroic prism 15, respectively. The position of the optical sensor 26 when measuring light can be appropriately changed according to the configuration and driving of the motor 41 and the arm 42. The position of the optical sensor 26 can be accurately controlled by using, for example, an encoder.

  FIG. 16 illustrates a second modification of the second embodiment. The linear actuator 50 used in this modification performs a linear motion. The linear actuator 50 is a moving unit that moves the optical sensor 26. The arm 54 is sandwiched between a plurality of rollers 53. The arm 54 can easily move in the horizontal direction by the rotation of the roller 53. The optical sensor 26 is attached to one end of the arm 54. The vibrating body 51 is installed in the linear actuator 50 in a state where the contact portion 52 is in contact with the arm 54. The arm 54 is fixed so as not to move freely in the horizontal direction by being pressed by the contact portion 52.

  The vibrating body 51 is configured using a piezoelectric element and stainless steel. The piezoelectric element expands and contracts when a voltage is applied. The vibrating body 51 generates vibration by expansion and contraction of the piezoelectric element. The vibrating body 51 can appropriately change the vibration direction of the contact portion 52 according to a method of applying a voltage to the piezoelectric element. When the contact portion 52 is vibrated in the oblique direction indicated by the double arrow, the arm 54 reciprocates in the horizontal direction. By using the linear actuator 50, the optical sensor 26 can be moved in the horizontal direction as in the case of the first modification. Also in the case of this modification, it is possible to measure with high accuracy by measuring the light with the optical sensor 26 moved to the approximate center of the optical path of the light from the spatial light modulators 14R, 14G, 14B.

  In the present embodiment, the spatial light modulators 14R, 14G, and 14B may switch only the portion corresponding to the position of the optical sensor 26 in the optical path from the display mode to the adjustment mode. By switching only a part to the adjustment mode, the image display can be continued in a part other than the part corresponding to the position of the optical sensor 26. Therefore, the influence on image viewing can be further reduced. Further, as in the case of the first embodiment, the color balance may be adjusted by measuring the intensity of light modulated in accordance with the image signal.

  In the present embodiment, the moving unit is not limited to moving the optical sensor 26 to a position facing the exit surface of the cross dichroic prism 15. For example, as shown in FIG. 17, the motor 61 that is a moving unit moves the optical sensor 26 within the projection lens 18. The motor 61 moves the optical sensor 26 to an image plane on which images of the spatial light modulation devices 14R, 14G, and 14B are formed immediately before the optical sensor 26 measures light.

  By moving the optical sensor 26 to the image plane in the projection lens 18, the average intensity of the light emitted from the spatial light modulators 14R, 14G, 14B can be measured. Further, by measuring the light intensity at the position where the light is concentrated, a higher SN ratio can be realized, and correction with higher accuracy is possible. The moving unit may move the optical sensor 26 to the vicinity of the image plane in addition to moving the optical sensor 26 to the image plane in the projection lens 18. The image display apparatus according to the present invention is not limited to a projector. The image display device may be a so-called direct-view display, for example.

  As described above, the image display device according to the present invention is useful when displaying a color image corresponding to an image signal.

1 is a diagram illustrating a schematic configuration of a projector according to a first embodiment of the invention. The figure which shows schematic structure of the illuminating device for R lights. The flowchart which shows the procedure which adjusts the intensity | strength of the light from each spatial light modulator. The figure explaining the timing etc. which measure the intensity | strength of light. The figure which shows the example of a voltage reference value and a measured value. The flowchart which shows the procedure which adjusts the intensity | strength of the light from each spatial light modulator. The figure which shows the example of a voltage reference value and a measured value. The flowchart which shows the procedure which adjusts the intensity | strength of the light from each spatial light modulator. The figure which shows the example of a voltage reference value and a measured value. The figure explaining the characteristic of a spatial light modulation device. FIG. 5 is a diagram illustrating a schematic configuration of a projector according to a second embodiment of the invention. The figure explaining the part in which the optical sensor and the motor were provided. The other figure explaining the part in which the optical sensor and the motor were provided. FIG. 6 is a diagram for explaining a first modification of the second embodiment. The figure explaining the part in which the optical sensor and the motor were provided. FIG. 6 is a diagram illustrating a second modification of the second embodiment. The figure explaining the case where an optical sensor is moved within a projection lens.

Explanation of symbols

  10 projector, 11R R light illumination device, 11G G light illumination device, 11B B light illumination device, 12R R light LED, 12G G light LED, 12B B light LED, 13 field lens, 14R R light Spatial light modulation device, 14G G light spatial light modulation device, 14B B light spatial light modulation device, 15 cross dichroic prism, 16 first dichroic film, 17 second dichroic film, 18 projection lens, 20 control device, 21 image Signal processing unit, 22 spatial light modulation signal generation unit, 23 adjustment unit, 24R R light source driving unit, 24G G light source driving unit, 24B B light source driving unit, 25 photo sensor driving unit, 26 photo sensor, 30 projector, 31 motor, 32 arm, 41 motor, 42 arm, 50 linear actuator, 51 Vibrating body, 52 contact portion, 53 roller, 54 arm, 61 motor

Claims (8)

A light source unit for supplying light;
A spatial light modulation device that modulates light from the light source unit according to an image signal;
A measuring unit that measures the intensity of light from the spatial light modulator within a certain period of time during which light modulated in accordance with the image signal is emitted;
An adjustment unit that adjusts the intensity of light from the spatial light modulation device by controlling driving of at least one of the light source unit and the spatial light modulation device based on a result of measurement by the measurement unit. An image display device characterized by the above. The spatial light modulation device is switched from a first state controlled according to the image signal to a second state controlled according to a signal other than the image signal,
The image display device according to claim 1, wherein the measurement unit measures the intensity of light from the spatial light modulation device in the second state.   The spatial light modulator is controlled so that the gradation of the entire screen in the second state substantially matches the average value of the gradation of the entire screen in the first state. 2. The image display device according to 2.   The image display apparatus according to claim 1, wherein the measurement unit measures the intensity of light modulated according to the image signal.   The said adjustment part adjusts the intensity | strength of the light from the said spatial light modulation apparatus according to the average intensity | strength of the light radiate | emitted from the said spatial light modulation apparatus. The image display device described.   6. The image display device according to claim 1, further comprising a moving unit that moves the measurement unit into and out of an optical path of light from the spatial light modulation device.   The image display device according to claim 6, wherein the moving unit moves the measurement unit to a plurality of positions in an optical path of light from the spatial light modulation device. A projection lens for projecting light from the spatial light modulator;
The image display apparatus according to claim 6, wherein the moving unit moves the measuring unit to an image plane in the projection lens or in the vicinity of the image plane.

Images