JP5278090B2 - Video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video display and light source control method therefor, capable of controlling brightness of a semiconductor light source, without degrading image quality of a displayed video image. <P>SOLUTION: A video feature detection section 5 creates a histogram data for each frame in each input video image signal corresponding to each color of R, G and B. A control section 6 determines a required light amount value of each color for each frame based on the histogram data, and determines target duty ratios of driving pulses of LED 14R, 14G and 14B, based on the light amount value. A correction section 18 corrects the target duty ratios corresponding to the LED 14R, 14G and 14B, by using detection values of LED temperature detection section 16R, 16G and 16B, and an ambient temperature detection section 17, an LED &Delta; temperature table 21, and a correction coefficient table 22. An LED driving section 15 drives the LED 14R, 14G and 14B by the target duty ratio after correction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention is a light emitting diode (LED: Light Emitting Diode) relates to a video display equipment using the semiconductor light source such as.

  Conventionally, in a projection display device, it is known to control the amount of light using an optical iris in order to improve the contrast of an image (see, for example, Patent Document 1).

  FIG. 6 is a schematic configuration diagram showing an example of a conventional projection display device having an optical iris. In the projection display device 1 shown in FIG. 6, white light emitted from a light source 2 such as a metal halide lamp is converted into red light (R light), green light (G light), and blue light (B light) by the color separation unit 3. After being decomposed, each color light enters the corresponding light modulation element 4R, 4G, 4B.

  The video feature detection unit 5 generates histogram data indicating the distribution of gradations in the video signal corresponding to each input color, and the control unit 6 is based on the histogram data generated by the video feature detection unit 5. Determine the amount of light required for display.

  The control unit 6 opens and closes the iris 8 by the iris driving unit 7 in order to adjust the light amount based on the determined light amount value. Further, the gradation correction unit 9 corrects the gradation of the input video signal corresponding to each color based on the light amount value determined by the control unit 6. The light modulation element driving unit 10 drives the light modulation elements 4R, 4G, and 4B based on the corrected video signals corresponding to the respective colors that have been subjected to gradation correction by the gradation correction unit 9.

  The light modulation elements 4R, 4G, and 4B modulate the R light, G light, and B light from the color separation unit 3 in accordance with the corresponding corrected video signals, and send the modulated color lights to the color synthesis unit 11. Eject. The color synthesizing unit 11 synthesizes and emits the respective color lights from the light modulation elements 4R, 4G, and 4B. The combined light emitted from the color combining unit 11 is projected onto the screen 13 by the projection lens 12 after the light amount is adjusted by the iris 8.

  FIG. 7 is a diagram for explaining the light amount control by the iris 8. As shown in FIG. 7, when the light amount incident on the projection lens 12 is decreased, the iris 8 is closed (the iris amount is increased), and when the light amount is increased, the iris 8 is opened (the iris amount is decreased). Be controlled.

  As described above, in the projection display device 1, the light amount incident on the projection lens 12 is adjusted by the iris 8 based on the detection result of the video feature detection unit 5, and the gradation of the input video signal is corrected.

  FIG. 8 is a diagram for explaining the effect of improving the contrast of an image by the iris operation in the projection display device 1. As shown in FIG. 8A, in a dark scene, the iris is narrowed down, and the gradation correction unit 9 performs gradation correction such that the intermediate gradation is raised with respect to the input gradation of the video signal. On the other hand, in a bright scene, as shown in FIG. 8B, the iris 8 is opened and tone correction of the video signal is not performed.

  Thus, by using the iris 8, it is possible to realize a greater contrast (dynamic contrast) than the contrast obtained without using the iris 8 (native contrast), and to improve the contrast of the video.

  However, when the amount of light incident on the projection lens 12 is limited by the iris 8 as in the projection display device 1, more light than necessary is emitted from the light source 2, resulting in wasted power consumption. It was. In addition, since the iris 8 is operated by a mechanical mechanism, it easily breaks down and the operation speed is limited.

  In recent years, semiconductor light sources such as LEDs and semiconductor lasers have attracted attention as light sources. These light sources are expected to be able to widen the color gamut and express more realistic images. In addition, since the light amount can be adjusted without using a mechanical mechanism such as an iris mechanism, the light amount can be adjusted at high speed with little failure.

  FIG. 9 is a schematic configuration diagram showing an example of a conventional projection display device using an LED as a light source. In FIG. 9, the same or equivalent components as those in FIG.

  The projection display device 1A shown in FIG. 9 omits the light source 2, the color separation unit 3, the iris driving unit 7, and the iris 8 from the projection display device 1 shown in FIG. The LED 14R, 14G, and 14B that emit light and the LED driving unit 15 that drives the LEDs 14R, 14G, and 14B by PWM (Pulse Width Modulation) are provided.

  The control unit 6 controls the light emission luminance of the LEDs 14R, 14G, and 14B by controlling the duty ratio of the driving pulses of the LEDs 14R, 14G, and 14B by the LED driving unit 15.

  FIG. 10 is a diagram for explaining the luminance control of the LED by the duty ratio of the drive pulse. As shown in FIG. 10, when the duty ratio of the drive pulse is decreased, the light emission luminance of the LED is lowered, and when the duty ratio is increased, the light emission luminance of the LED is increased.

  FIG. 11 is a diagram for explaining the effect of improving the contrast of an image by controlling the duty ratio of the drive pulses of the LEDs 14R, 14G, and 14B in the projection display device 1A. As shown in FIG. 11A, in a dark scene, the duty ratio is reduced to lower the luminance of the LEDs 14R, 14G, and 14B, and the gradation correction unit 9 performs intermediate gradation with respect to the input gradation of the video signal. Tone correction that lifts up. On the other hand, in a bright scene, as shown in FIG. 11 (b), the duty ratio is increased to increase the luminance of the LEDs 14R, 14G, and 14B, and the gradation correction of the video signal is not performed.

  In this way, by controlling the duty ratio of the drive pulses of the LEDs 14R, 14G, and 14B, it is possible to improve the contrast of the image as in the case of controlling the iris 8 with the projection display device 1 shown in FIG. it can.

JP 2008-2087A

  As described above, when the LED is PWM driven, the brightness is changed by changing the duty ratio of the drive pulse. However, when the duty ratio is changed relatively abruptly, the brightness of the LED changes more than expected. Will occur.

  This phenomenon will be described. FIG. 12 is a diagram showing a change in the duty ratio of the drive pulse and a corresponding change in the brightness and temperature of the LED, and FIG. 13 is a relationship between the LED temperature and the brightness when the duty ratio of the drive pulse is constant. FIG.

  When the duty ratio is increased from D1 to D2 as shown in FIG. 12A, the luminance of the LED increases from Y1 to Y2, but the time t1 when the duty ratio is changed as shown in FIG. Immediately after, the brightness of the LED increases rapidly and becomes higher than Y2. In particular, the luminance changes abruptly within a few hundred ms immediately after time t1.

  As shown in FIG. 13, the LED has a temperature characteristic that the luminance is higher when the temperature is lower. When the duty ratio is increased as shown in FIG. 12A, as shown in FIG. 12C, the temperature of the LED gradually increases from T1, reaches a thermal equilibrium state at time t2, and reaches the temperature T2. Stabilize. Between time t1 and t2, although it depends on the heat capacity of a heat sink or heat pipe provided to cool the LED, it takes about several tens of seconds.

  As shown in FIG. 12C, immediately after the duty ratio is increased, the LED is not sufficiently warmed, so that the brightness of the LED is higher than Y2 from the temperature characteristics of FIG. As time elapses and the LED becomes in a thermal equilibrium state and stabilizes at the temperature T2, the luminance is also stabilized at Y2.

  When the duty ratio of the LED drive pulse is lowered, the reverse phenomenon occurs when the duty ratio is raised, and the brightness of the LED decreases rapidly immediately after the change of the duty ratio, and then gradually increases. The brightness stabilizes after 10 seconds.

  Due to such a phenomenon, the brightness and white balance are stable in an apparatus that improves the contrast of the image by controlling the brightness of the LEDs 14R, 14G, and 14B as the light sources, such as the projection display apparatus 1A shown in FIG. In some cases, the image quality deteriorates.

The present invention has been made in view of the above, and an object thereof is to provide a video display equipment that can without degrading the image quality of the image to be displayed, controls the brightness of the semiconductor light source such as an LED.

According to one aspect of the present invention, there is provided a video display device including a display unit that modulates incident light based on a video signal input from the outside and displays a video according to the video signal, the display unit in a semiconductor light source for generating the light used to view the image, and the image feature detection means for detecting the distribution of gradation in the image signal, a light source temperature detecting means for detecting a temperature of the semiconductor light source, wherein An ambient temperature detecting means for detecting an ambient temperature around the video display device; and a light emission luminance of the semiconductor light source based on a detection result of the video feature detection means; and the semiconductor light source based on the obtained light emission luminance. control means for determining a target duty ratio of the drive pulse for driving the temperature difference der temperature and said environmental temperature of the semiconductor light source when the semiconductor light source is a thermal equilibrium state Storage means storing a correspondence relationship between the first temperature difference and the target duty ratio, and a correspondence relationship between the target duty ratio and the correction coefficient, and the detected temperature of the semiconductor light source at predetermined time intervals. A difference value between a second temperature difference that is a temperature difference from the detected ambient temperature and the first temperature difference corresponding to the target duty ratio determined by the control unit is calculated, and the second temperature difference is calculated. And the difference value is multiplied by the correction coefficient corresponding to the target duty ratio determined by the control means to calculate a duty ratio correction value, and the target duty ratio determined by the control means is calculated as the duty ratio. There is provided a video display device comprising correction means for performing correction for adding correction values .

According to another aspect of the present invention, there is provided a video display device including a display unit that modulates incident light based on a video signal input from the outside and displays a video according to the video signal. A semiconductor light source that generates the light used to display the video by means, a video feature detection unit that detects a gradation distribution in the video signal, a light source temperature detection unit that detects a temperature of the semiconductor light source, An ambient temperature detecting means for detecting an ambient temperature around the video display device; and a light emission brightness of the semiconductor light source based on a detection result of the video feature detection means; and the semiconductor light source based on the obtained light emission brightness And a first temperature difference that is a temperature difference between the temperature of the semiconductor light source and the environmental temperature when the semiconductor light source is in a thermal equilibrium state. The correspondence relationship between the target drive current value, and the target drive current value and a storage unit that stores a correspondence relationship between the correction coefficient for each predetermined time, is the detected temperature of the detected the semiconductor light source Calculating a difference value between the second temperature difference, which is a temperature difference from the environmental temperature, and the first temperature difference corresponding to the target drive current value determined by the control means, and the second temperature difference and the A drive current correction value is calculated by multiplying the difference from the difference value by the correction coefficient corresponding to the target drive current value determined by the control means, and the target drive current value determined by the control means is calculated as the drive current. There is provided a video display device comprising correction means for correcting based on the correction value.

According to the onset bright, it can without degrading the image quality of the image to be displayed, controls the brightness of the semiconductor light source such as an LED.

It is a schematic block diagram which shows the video display apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between the duty ratio of the drive pulse of LED, and LED (DELTA) temperature. It is a figure which shows the relationship between a duty ratio correction value and LED (DELTA) temperature difference. It is a figure which shows the relationship between a target duty ratio and a correction coefficient. It is a figure for demonstrating changes, such as a drive duty ratio and the brightness | luminance of LED, according to the change of the target duty ratio in the video display apparatus shown in FIG. It is a schematic block diagram which shows an example of the conventional projection display apparatus. It is a figure for demonstrating light quantity control by the iris in the projection display apparatus shown in FIG. It is a figure for demonstrating the effect of the contrast improvement of the image | video by iris operation | movement. It is a schematic block diagram which shows an example of the conventional projection display apparatus using LED as a light source. It is a figure for demonstrating the brightness | luminance control of LED by the duty ratio of a drive pulse. It is a figure for demonstrating the effect of the contrast improvement of the image | video by duty ratio control of the drive pulse of LED in the projection display apparatus shown in FIG. It is a figure which shows the change of the luminance and temperature of LED corresponding to the change of the duty ratio of a drive pulse, and it. It is a figure which shows the relationship between the temperature of LED, and a brightness | luminance when the duty ratio of a drive pulse is made constant.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a video display apparatus according to an embodiment of the present invention. In FIG. 1, the same or equivalent components as those in FIG. 9 are given the same or equivalent reference numerals.

  As shown in FIG. 1, an image display device 100 according to the present embodiment includes LEDs (semiconductor light sources) 14R, 14G, and 14B that emit red light, green light, and blue light, respectively, and an image feature detection unit (image feature). Detection means) 5, control section (control means) 6, LED temperature detection sections (light source temperature detection means) 16R, 16G, 16B, environmental temperature detection section (environment temperature detection means) 17, and correction section (correction means). ) 18, LED drive unit 15, gradation correction unit 9, light modulation element drive unit 10, light modulation elements (display means) 4R, 4G, 4B, color synthesis unit 11, and projection lens 12. Prepare. The video display device 100 is a projection display device.

  The LEDs 14R, 14G, and 14B are light sources that generate light used to display an image based on a video signal input from the outside in the video display device 100 on the screen 13, and emit R light, G light, and B light, respectively. To do. Light emitted from the LEDs 14R, 14G, and 14B is incident on the light modulation elements 4R, 4G, and 4B.

  The video feature detection unit 5 generates histogram data indicating the distribution of gradation for each frame for each of the video signals corresponding to the R, G, and B colors input from the outside. Output to.

  Based on the histogram data generated by the video feature detection unit 5, the control unit 6 determines the light amount value of each color necessary for displaying the video for each frame, and based on the determined light amount value, the LED driving unit 15. The target duty ratio of the drive pulses of the LEDs 14R, 14G, and 14B is determined, and the target duty ratio for each of the LEDs 14R, 14G, and 14B is output to the correction unit 18.

  The LED temperature detection units 16R, 16G, and 16B detect the temperatures of the LEDs 14R, 14G, and 14B, and output the detection results to the correction unit 18.

  The environmental temperature detection unit 17 detects the environmental temperature around the video display device 100 and outputs the detection result to the correction unit 18.

  The correction unit 18 includes a correction control unit 19 and an addition unit 20. The correction control unit 19 holds an LEDΔ temperature table 21 and a correction coefficient table 22 in each of the LEDs 14R, 14G, and 14B, and the detection values of the LED temperature detection units 16R, 16G, and 16B and the environmental temperature detection unit 17, and the LEDΔ Using the temperature table 21 and the correction coefficient table 22, a duty ratio correction value for correcting the target duty ratio input from the control unit 6 is calculated for each of the LEDs 14R, 14G, and 14B.

  The LED Δ temperature table 21 is a table that stores the relationship between the duty ratio of the drive pulse and the LED Δ temperature for each of the LEDs 14R, 14G, and 14B. Here, the LED Δ temperature is a difference value between the temperature of the LED and the environmental temperature when the LED is in a thermal equilibrium state and the temperature and brightness are stabilized. As shown in FIG. 2, the duty ratio and the LED Δ temperature have a linear relationship, and the LED Δ temperature table 21 is calculated based on the duty ratio and LED Δ shown in the graph of FIG. 2 for each LED 14 R, 14 G, and 14 B measured experimentally in advance. The relationship with temperature is preserved.

  The duty ratio correction value used in this embodiment is that the luminance of the LED immediately after the change when the drive duty ratio, which is the duty ratio of the drive pulse, is changed from a certain value to the corrected target duty ratio depends on the target duty ratio. It is a value experimentally measured in advance for each target duty ratio as a value equal to the luminance when the driven LED is in a thermal equilibrium state.

  The duty ratio correction value measured as described above has a linear relationship with the LED Δ temperature difference as shown in FIG. In FIG. 3, only four values (25%, 50%, 75%, 100%) are shown as the target duty ratio, and other values are omitted. Here, the LED Δ temperature difference is a value obtained by subtracting the LED Δ temperature from the difference value between the current LED temperature and the environmental temperature.

  Therefore, if the slope of each straight line corresponding to each target duty ratio as shown in FIG. 3 is known, the current LED temperature detected by the LED temperature detectors 16R, 16G, and 16B and the environmental temperature detector 17 and The LED Δ temperature difference corresponding to the target duty ratio is obtained from the environmental temperature and the LED Δ temperature table 21, and this LED Δ temperature difference is multiplied by the slope of the straight line corresponding to the target duty ratio in FIG. The duty ratio correction value can be calculated.

  Therefore, in this embodiment, the slope of the straight line for each target duty ratio in FIG. 3 experimentally measured for each LED 14R, 14G, 14B is stored in the correction coefficient table 22 as a correction coefficient. An example of the relationship between the target duty ratio and the correction coefficient stored in the correction coefficient table 22 is shown in FIG.

  When the target duty ratios corresponding to the LEDs 14R, 14G, and 14B are input from the control unit 6 to the correction control unit 19, the duty ratio correction values dr and dg for correcting the target duty ratios of the LEDs 14R, 14G, and 14B, respectively. , Db are calculated by the following (Equation 1).

dr = {(Tr−Ta) −ΔTr} × Kr
dg = {(Tg−Ta) −ΔTg} × Kg (Formula 1)
db = {(Tb−Ta) −ΔTb} × Kb
Here, Tr, Tg, and Tb are detection values of the LED temperature detection units 16R, 16G, and 16B, Ta is a detection value of the environmental temperature detection unit 17, and ΔTr, ΔTg, and ΔTb are LEDΔ temperature tables for the LEDs 14R, 14G, and 14B, respectively. LED Δ temperature differences corresponding to the target duty ratio obtained from 21, Kr, Kg, Kb are correction coefficients corresponding to the target duty ratio obtained from the correction coefficient table 22 for the LEDs 14 R, 14 G, 14 B, respectively.

  The adding unit 20 adds the target duty ratio input from the control unit 6 and the duty ratio correction value calculated by the correction control unit 19, and calculates the corrected target duty ratio for each of the LEDs 14R, 14G, and 14B. Output to the drive unit 15.

  The LED drive unit 15 drives the LEDs 14R, 14G, and 14B by the drive pulse of the corrected target duty ratio for each of the LEDs 14R, 14G, and 14B input from the correction unit 18.

  The gradation correction unit 9 corrects the gradation of the video signal corresponding to each input color based on the light amount value determined by the control unit 6.

  The light modulation element driving unit 10 drives the light modulation elements 4R, 4G, and 4B based on the corrected video signals corresponding to the respective colors that have been subjected to gradation correction by the gradation correction unit 9.

  The light modulation elements 4R, 4G, and 4B modulate the R light, G light, and B light from the LEDs 14R, 14G, and 14B in accordance with the corresponding corrected video signals supplied from the light modulation element driving unit 10, Each modulated color light is emitted to the color synthesis unit 11.

  The color synthesizing unit 11 includes a reflection mirror, a synthesis prism, and the like, and synthesizes and emits each color light incident from the light modulation elements 4R, 4G, and 4B. The projection lens 12 projects the light emitted from the color synthesis unit 11 onto the screen 13.

  Next, the operation of the video display device 100 will be described.

  When a video signal corresponding to each color of R, G, and B is input from the outside, the video feature detection unit 5 generates histogram data indicating a gradation distribution for each frame for each video signal corresponding to each color. The histogram data is output to the control unit 6.

  Based on the histogram data of each color generated by the video feature detection unit 5, the control unit 6 determines the light quantity value of each color necessary for displaying the video for each frame. Moreover, the control part 6 determines the target duty ratio of the drive pulse of LED14R, 14G, 14B by the LED drive part 15 based on the determined light quantity value. The control unit 6 outputs the determined light amount value of each color to the gradation correction unit 9, and outputs the target duty ratio for each of the LEDs 14R, 14G, and 14B to the correction unit 18.

  When the target duty ratio corresponding to each LED 14R, 14G, 14B is input from the control unit 6 to the correction control unit 19, the detection values of the LED temperature detection units 16R, 16G, 16B and the environmental temperature detection unit 17, and the LED Δ temperature With reference to the table 21 and the correction coefficient table 22, the duty ratio correction values dr, dg, and db are calculated by the above-described (Equation 1). The duty ratio correction value is calculated every predetermined time (for example, every frame).

  Next, the adding unit 20 adds the target duty ratio input from the control unit 6 and the duty ratio correction value calculated by the correction control unit 19 to correct the target duty ratio after correction for each of the LEDs 14R, 14G, and 14B. Is output to the LED drive unit 15.

  Then, the LED drive unit 15 drives the LEDs 14R, 14G, and 14B by the drive pulse of the corrected target duty ratio for each of the LEDs 14R, 14G, and 14B input from the correction unit 18.

  Further, the gradation correction unit 9 corrects the gradation of the video signal corresponding to each input color based on the light amount value input from the control unit 6, and optically modulates the corrected video signal corresponding to each corrected color. Output to the element drive unit 10. The light modulation element driving unit 10 drives the light modulation elements 4R, 4G, and 4B based on the corrected video signals corresponding to the respective colors that have been subjected to gradation correction by the gradation correction unit 9.

  The light modulation elements 4R, 4G, and 4B modulate the R light, G light, and B light from the LEDs 14R, 14G, and 14B in accordance with the corrected video signal supplied from the light modulation element driving unit 10, and each modulated color Light is emitted to the color composition unit 11.

  The color synthesizing unit 11 synthesizes and emits the respective color lights incident from the light modulation elements 4R, 4G, and 4B. The projection lens 12 projects the light emitted from the color synthesis unit 11 onto the screen 13. As a result, an image is displayed on the screen 13.

  FIG. 5 is a diagram for explaining changes in drive duty ratio, LED brightness, and the like according to changes in the target duty ratio in the video display device 100. Here, it shall show about LED14R.

  During the operation of displaying an image on the image display device 100, the correction control unit 19 calculates a duty ratio correction value every predetermined time by the procedure as described above. The LED 14 </ b> R is driven with a corrected target duty ratio (drive duty ratio) obtained by adding the target duty ratio and the duty ratio correction value by the adding unit 20.

  As shown in FIG. 5A, the change in the duty ratio correction value when the target duty ratio increases from D1 to D2 at time t1 is shown in FIG. 5B, and the drive duty ratio that is the corrected target duty ratio is shown in FIG. The change of FIG. 5 is shown in FIG. As shown in FIGS. 5B and 5C, for example, if the duty ratio correction value at time t1 is d1, the drive duty ratio is D2 + d1 larger than D1.

  As the drive duty ratio increases, the temperature of the LED 14R increases, so the difference value between the current temperature Tr of the LED 14R detected by the LED temperature detection unit 16R and the current environmental temperature Ta detected by the environmental temperature detection unit 17 is also obtained. growing. Therefore, from the above-described (Equation 1), the duty ratio correction value and the drive duty ratio calculated next are larger than the duty ratio correction value d1 and the drive duty ratio D2 + d1 at time t1.

  As described above, the duty ratio correction value and the drive duty ratio are changed as shown in FIGS. 5B and 5C by the change of the drive duty ratio due to the correction of the target duty ratio and the repeated temperature change of the LED 14R. The drive duty ratio changes step by step until the drive duty ratio reaches D2.

  FIG. 5D shows a change in the difference value Tr−Ta between the current temperature Tr of the LED 14R detected by the LED temperature detection unit 16R and the current environmental temperature Ta detected by the environmental temperature detection unit 17 in this case. . As shown in FIG. 5 (d), the difference value Tr-Ta increases as the drive duty ratio increases. In FIG. 5D, ΔT1 and ΔT2 are LED Δ temperatures corresponding to the duty ratios D1 and D2 for the LED 14R in the LED Δ temperature table 21, respectively.

  Further, the difference between the current value Tr-Ta of the LED 14R and the ambient temperature Ta and the value ΔTr of the LED Δ temperature table 21 (in the example shown, ΔT1 until time t1, ΔT2 after time t1). The temperature error ΔTr− (Tr−Ta) = − {(Tr−Ta) −ΔTr} is shown in FIG. The duty ratio correction value changes according to this temperature error, as can be seen from the above-described (Equation 1).

  As described above, the duty ratio correction value indicates that the LED luminance immediately after the change when the duty ratio is changed from a certain value to the corrected target duty ratio is the thermal equilibrium of the LED driven by the target duty ratio. It is a value measured in advance as a value that is equal to the luminance at the time of entering the state. For example, the drive duty ratio D2 + d1 in which the target duty ratio D2 is corrected with the duty ratio correction value d1 is such that the luminance of the LED 14R immediately after the drive duty ratio is changed to D2 + d1 is the thermal equilibrium of the LED 14R driven with the target duty ratio D2. The value is equal to the luminance Y2 when the state is reached. The same applies to the drive duty ratio corrected with the duty ratio correction value calculated after time t1, so that the luminance of the LED 14R driven with the drive duty ratio shown in FIG. 5C is as shown in FIG. 5F. At time t1, it changes from Y1 to Y2, and Y2 is maintained thereafter.

  Even when the target duty ratio decreases, it is possible to obtain appropriate luminance immediately after the change of the target duty ratio by correcting the target duty ratio using the duty ratio correction value calculated by the above (Equation 1).

  As described above, in the present embodiment, the target duty ratios corresponding to the LEDs 14R, 14G, and 14B are determined based on the detected values of the LED temperature detection units 16R, 16G, and 16B and the environmental temperature detection unit 17, the LED Δ temperature table 21, and the correction coefficient. By correcting with the duty ratio correction value calculated using the table 22 and driving the LEDs 14R, 14G, and 14B with the corrected target duty ratio, a desired luminance can be obtained immediately after the change of the target duty ratio. For this reason, the luminance of the LEDs 14R, 14G, and 14B can be controlled without degrading the image quality of the displayed video.

  In the present embodiment, a necessary light amount value is obtained for each color, and the target duty ratio is determined and corrected for each LED 14R, 14G, 14B, but this is not restrictive. For example, the video feature detection unit 5 generates histogram data based on the luminance signal component of the input video signal, and based on the histogram data, the control unit 6 determines a necessary light amount value and a target duty ratio for each color. The ratio may be corrected using the detection values of the LED temperature detection units 16R, 16G, and 16B and the environmental temperature detection unit 17, the LED Δ temperature table 21, and the correction coefficient table 22. In this case, the correction control unit 19 holds the LED Δ temperature table 21 and the correction coefficient table 22 common to the respective colors.

  Further, in the present embodiment, the case where the LEDs 14R, 14G, and 14B are PWM driven and the luminance of the LEDs 14R, 14G, and 14B is changed by changing the duty ratio of the drive pulse has been described. The luminance may be changed by changing the drive current value.

  In this case, the target drive current value is determined instead of the target duty ratio, and the detected values of the LED temperature detection units 16R, 16G, and 16B and the environmental temperature detection unit 17, and the LED Δ that maintains the relationship between the drive current value and the LED Δ temperature. The drive current correction value is calculated using the temperature table 21 and the correction coefficient table 22 that holds the relationship between the drive current value and the correction coefficient, and the target drive current value is corrected using the drive current correction value. The LEDs 14R, 14G, and 14B are driven by the corrected target drive current value.

  In this embodiment, the case where an LED is used as the light source has been described. However, any semiconductor light source such as an LED or a semiconductor laser may be used.

  In the present embodiment, the case where the LEDs 14R, 14G, and 14B that respectively emit red light, green light, and blue light are used as the light source has been described. However, one white LED may be used, in which case the LED One temperature detection unit can be provided, and the projection display device can be downsized. At this time, the video feature detection unit 5 only has to detect the histogram data of the level of the luminance signal from the video signal input from the outside, and the circuit configuration can be simplified.

DESCRIPTION OF SYMBOLS 1,1A Projection display apparatus 2 Light source 3 Color separation part 4R, 4G, 4B Light modulation element 5 Image | video feature detection part 6 Control part 7 Iris drive part 8 Iris 9 Tone correction part 10 Light modulation element drive part 11 Color composition part 12 Projection lens 13 Screen 14R, 14G, 14B LED
DESCRIPTION OF SYMBOLS 15 LED drive part 16R, 16G, 16B LED temperature detection part 17 Environment temperature detection part 18 Correction | amendment part 19 Correction control part 20 Addition part 21 LED (DELTA) temperature table 22 Correction coefficient table 100 Image | video display apparatus

Claims (2)

A video display device comprising display means for modulating incident light based on a video signal input from the outside and displaying a video corresponding to the video signal,
A semiconductor light source for generating the light used for displaying the video on the display means;
Video feature detection means for detecting gradation distribution in the video signal;
Light source temperature detecting means for detecting the temperature of the semiconductor light source;
Environmental temperature detecting means for detecting the environmental temperature around the video display device;
Control means for determining the emission luminance of the semiconductor light source based on the detection result of the video feature detection means, and determining a target duty ratio of a driving pulse for driving the semiconductor light source based on the obtained emission luminance;
Correspondence relationship between a first temperature difference that is a temperature difference between the temperature of the semiconductor light source and the ambient temperature when the semiconductor light source is in a thermal equilibrium state and the target duty ratio, and the target duty ratio and a correction coefficient Storage means for storing the correspondence relationship with
The first temperature corresponding to a second temperature difference, which is a temperature difference between the detected temperature of the semiconductor light source and the detected environmental temperature, and the target duty ratio determined by the control means at predetermined time intervals. A difference value with a temperature difference is calculated, and a duty ratio correction value is calculated by multiplying the difference between the second temperature difference and the difference value by the correction coefficient corresponding to the target duty ratio determined by the control means. A video display device comprising: correction means for performing correction by adding the duty ratio correction value to the target duty ratio determined by the control means. A video display device comprising display means for modulating incident light based on a video signal input from the outside and displaying a video corresponding to the video signal,
A semiconductor light source for generating the light used for displaying the video on the display means;
Video feature detection means for detecting gradation distribution in the video signal;
Light source temperature detecting means for detecting the temperature of the semiconductor light source;
Environmental temperature detecting means for detecting the environmental temperature around the video display device;
Control means for determining a light emission luminance of the semiconductor light source based on a detection result of the video feature detection means, and determining a target drive current value for driving the semiconductor light source based on the obtained light emission luminance;
Correspondence between a first temperature difference that is a temperature difference between the temperature of the semiconductor light source and the ambient temperature when the semiconductor light source is in a thermal equilibrium state and the target drive current value, and the target drive current value Storage means for storing the correspondence with the correction coefficient;
At predetermined time intervals, and the second temperature difference is a difference between the temperature and the detected the environmental temperature of the detected the semiconductor light source, the first corresponding to the target drive current value in which the control means has determined A difference value with respect to one temperature difference is calculated, and a difference between the second temperature difference and the difference value is multiplied by the correction coefficient corresponding to the target drive current value determined by the control means to obtain a drive current correction value. A video display apparatus comprising: a correction unit that calculates and corrects the target drive current value determined by the control unit based on the drive current correction value.

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