JP2011180521A - Image display device and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of maintaining color balance of an image. <P>SOLUTION: The image display device includes a light source 1; an image display section 3 for modulating the light emitted by the light source 1 pixel by pixel and displaying the result of the modulation as an image; a light emission period control section 4 for determining light emission period which is the period corresponding to one when the light source 1 emits a light, pixel by pixel, based on input image data; a light emission amount detecting section 6 for detecting the amount of light emitted by the light source 1 as a detected light emission amount; a target light emitted amount calculating section 8 for calculating target light emitted amount, based on the light emission period and a predetermined reference-wave peak value; and a light source control section 5 for controlling the light source 1 so that the detected light emitted amount becomes the target light emitted amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image display apparatus and an image display method using a light modulation device.

  There is an image display apparatus that adopts a DLP (registered trademark) (Digital Light Processing) system using a single-plate DMD (registered trademark) (Digital Micromirror Device) as a light modulation device. DMD (registered trademark) includes a mirror for each pixel. Depending on the inclination of the mirror, there are an on state in which light is reflected on the screen and an off state in which light is not reflected on the screen. In the DLP (registered trademark) system, the tone is expressed by controlling the reflectance by controlling the tilt of the DMD mirror. Specifically, with respect to light of three primary colors (for example, RGB (Red, Green, Blue)) irradiated in a time division manner, the ratio of the on time and the off time of the mirrors constituting the DMD (registered trademark) pixels, respectively. By changing (hereinafter referred to as the ON / OFF time ratio), light and dark (light / dark) is expressed.

  In the above-described method, the light intensity of each color light source is made constant regardless of the size of the image data, and the brightness of the image is expressed by changing the on / off ratio of DMD (registered trademark). Therefore, when displaying a dark image, the light source emits light in the same manner as a bright image, although there is little light to be displayed. Therefore, there is a problem that light unnecessary for display (light other than desired light reflected on the screen by DMD (registered trademark)) increases, energy is wasted, and stray light is generated.

  As an improvement measure for this problem, by assigning a light emission period to the light source of each color according to the input image data of each color, the light emission of the light source is minimized to save energy, and stray light is reduced to reduce the image. A technique for increasing the contrast is disclosed (for example, see Patent Document 1 below).

JP 2008-281707 A

  However, according to the conventional technique for assigning the light emission time according to the input image data (input image), the light emission period is controlled, but the light emitter element has the temperature characteristics of the light emitter. Does not consider the characteristics. On the other hand, the amount of light emitted by the light emitter is not constant and may vary due to the characteristics of the light emitter element. Therefore, if the light emission period is changed, there is a difference between the light emission amount that is the control target and the actual light emission amount, and there is a difference between the light emission amount that is the control target and the actual light emission amount, and color balance is lost. There was a problem.

  The present invention has been made in view of the above, and an object of the present invention is to provide an image display device and an image display method capable of maintaining a color balance of a video while controlling a light emission period according to an input image. .

  In order to solve the above-described problems and achieve the object, the present invention modulates light emitted from one or more colors, light emitted from the light source for each pixel, and uses the modulation result as an image. An image display unit to display, a light emission period control unit that determines a light emission period that is a period during which the light source emits light for each pixel based on input image data, and emission of light emitted from the light source A light emission amount detection unit that detects the amount of light emitted as a detected light emission amount, and a target light emission that calculates a target light emission amount that is a control target value of the light emission amount of light emitted from the light source, based on the light emission period and a predetermined reference peak value And a light source control unit configured to control the light source so that the detected light emission amount becomes the target light emission amount.

  According to the present invention, it is possible to maintain the color balance of the video while controlling the light emission period according to the input image.

FIG. 1 is a diagram illustrating a functional configuration example of the image display apparatus according to the first embodiment. FIG. 2 is a diagram illustrating an example of a light emission pattern of a conventional image display apparatus and a control pattern of a light modulation device. FIG. 3A is a diagram illustrating an example in which the light modulation device is turned on in all periods within the light emission period of the light emitter. FIG. 3B is a diagram of an example in which the on period of the light modulation device is shortened. FIG. 3-3 is a diagram illustrating an example in which the on periods of the light modulation device are dispersed. FIG. 4 is a diagram illustrating an internal configuration example of the light emission period control unit. FIG. 5 is a diagram for explaining an example of the light emission timing signal. FIG. 6 is a diagram illustrating an example of a light emission period control signal of the light emitter R. FIG. 7 is a diagram illustrating an internal configuration example of the target light emission amount calculation unit 8. FIG. 8 is a diagram illustrating an internal configuration example of the wave height generation unit. FIG. 9 is a diagram illustrating an internal configuration example of the light source control unit. FIG. 10 is a diagram illustrating an example of a light emission drive signal for each light emitter generated by the light source control unit. FIG. 11 is a diagram illustrating a functional configuration example of the image display apparatus according to the second embodiment. FIG. 12 is a diagram illustrating a configuration example of the light emission period control unit of the second embodiment. FIG. 13 is a diagram illustrating an example of a temporary light emission period control signal and a light emission period control signal.

  Embodiments of an image display device and an image display method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a functional configuration example of an image display apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the image display apparatus according to the present embodiment includes a light source 1, an illumination unit 2, an image display unit 3, a light emission period control unit 4, a light source control unit 5, a light emission amount detection unit 6, and a wave height generation unit 7. , A target light emission amount calculation unit 8 and a reference wave height storage unit 9. The light source 1 includes a light emitter R (Red) 11, a light emitter G (Green) 12, and a light emitter B (Blue) 13.

  The light emission period control unit 4 analyzes the input image data for each display color, determines the light emission timing of each light emitter (light emitter R11, light emitter G12, light emitter B13) of the light source 1, and for each light emitter. The light emission period control signal is output. The light source controller 5 determines the amount of light emission using the light emission period control signal output from the light emission period controller 4 and the driving wave height value output from the wave height generator 7, and the light emitter R 11 and light emitter G 12 of the light source 1. , A light emission drive signal for causing each of the light emitters B13 to emit light is output, and a light detection period signal indicating the light emission period of each light emitter is output in order to detect the light emission amount of each light emitter. The illumination unit 2 irradiates the image display unit 3 almost uniformly with illumination light emitted from the light source 1. The image display unit 3 modulates the illumination light for each pixel based on the input image data to form a display image.

  Further, the target light emission amount calculation unit 8 calculates a target light emission amount serving as a control target according to image data and a width of the light emission period for each light emitter using the light emission period control signal output from the light emission period control unit 4. To do. The light emission amount detection unit 6 detects light emitted from the light emitter R11, light emitter G12, and light emitter B13 in synchronization with the light detection period signal output from the light source control unit 5, and the light emission amount of each light emitter. The detection value (detection amount) is output. The wave height generation unit 7 generates a driving wave height value such that the detection amount for each illuminant output from the light emission amount detection unit 6 matches the target light emission amount output from the target light emission amount calculation unit 8.

  Hereinafter, the image display apparatus according to the present embodiment will be described as a projection-type image display apparatus using DMD (registered trademark) as a display device of the image display unit 3. In this case, the image display unit 3 includes, for example, a DMD (registered trademark), a screen, and an optical system that projects light modulated by the DMD (registered trademark) onto the screen. The illumination unit 2 is an optical system for illuminating DMD (registered trademark).

  Any light emitter may be used as the light emitter R11, the light emitter G12, and the light emitter B13 included in the light source 1. For example, a laser or LED (Light Emitting Diode) that emits red, green, and blue light, respectively. Can be used.

  DMD (registered trademark) displays the image by controlling the brightness of each pixel according to the ratio (on / off time ratio) between the on time and the off time of the micromirror corresponding to the number of pixels of the display image. In a conventional image display device using DMD (registered trademark), the light source emits light, and the DMD (registered trademark) on / off time always has the same light emission pattern regardless of the input image. Illuminate body B in chronological order. In the following, DMD (registered trademark) is described as an optical modulation device.

  FIG. 2 is a diagram illustrating an example of a light emission pattern of a conventional image display apparatus and a control pattern of a light modulation device. In FIG. 2, the light emission patterns of the light emitter R, the light emitter G, and the light emitter B and the state (control pattern) of the light modulation device (micromirror) are shown in order from the top. In the lower part of FIG. 2, a plurality of control patterns (on time and off time) are illustrated as states of the light modulation device.

  In the lower part of FIG. 2, the control pattern of the light modulation device when a bright image is displayed at the top is shown, and the control pattern of the light modulation device when a darker image is displayed at the bottom. As shown in FIG. 2, in the conventional image display apparatus, the light emitter R, the light emitter G, and the light emitter B of the light source emit light in order by the light emission period t in a fixed time-division pattern. The brightness of the image is expressed by controlling the ratio of the on-time of the light modulation device within the light emission period t of each light emitter. The longer the on-time of the light modulation device, the brighter the image. When expressing a dark image, the on-time of the light modulation device is shortened. By controlling such a light modulation device for each pixel (for each minute mirror), an image is projected onto the screen. Note that FIG. 2 shows an example in which an image is one pixel for simplicity.

  Since the illumination light is not projected onto the screen when the light modulation device is turned off, the illumination light during the off period is not used for image display, and wasteful energy is consumed. Furthermore, illumination light during the off period causes a reduction in contrast such as stray light. For this reason, in the present embodiment, light emission during the off period is stopped by controlling the light emission period as described below, thereby reducing energy consumption and stray light.

  Next, a method for controlling the light emission period according to the present embodiment will be described. 3A to 3C are diagrams illustrating examples of control patterns for the light emission period according to the present embodiment. In this embodiment, the same period (light emission allocation period) is assigned to each light emitter for each frame, and each light emitter actually emits light within the light emission assignment period assigned to itself. Suppose that the period (light emission period) to be performed is determined. Here, the length of the light emission allocation period allocated to each light emitter is fixed and is the same period between the light emitters, but the length of the light emission allocation period may be variable, or the light emission allocation period between the light emitters. You may change the length. Also, in FIGS. 3-1 to 3-3, for the sake of simplicity, the light emission period is shown for one light emitter (any one of the light emitter R11, light emitter G12, and light emitter B13), and the image is one pixel. Show.

  In the example of FIG. 3A, the light modulation device is turned on in all periods within the light emission allocation period of the light emitter. In such a state, the brightness of the projected image is maximized. This is the same as the conventional image display apparatus.

  In the example of FIG. 3-2, an example of the control pattern of the light emission period when an image darker than that of FIG. 3A is expressed by the conventional method is shown in the upper part (a), and in the lower part (b). The example of the control pattern of the light emission period by the control method of this Embodiment is shown. As shown in FIG. 3A, in the conventional method, the light emission period is the same as that in FIG. 3A and the on-time of the light modulation device is shorter than that in FIG. 3A. On the other hand, in the control method of the present embodiment shown in FIG. 3B, the ON time of the light modulation device is shortened similarly to (a), and the period during which the light modulation device is OFF is Light emission of the light emitter is stopped, and light is emitted during a period when the light modulation device is turned on.

  FIG. 3C illustrates an example in which control is performed so that the ON periods of the light modulation devices are dispersed within one light emission allocation period. The upper part (a) of FIG. 3-3 shows an example of control by the conventional method, and the lower part (b) of FIG. 3-3 shows an example of performing control by the control method of the present embodiment. Yes. As shown in FIG. 3A, when the on-time of the light modulation device is dispersed, the light emission period is the same as the light emission period of FIG. On the other hand, as shown in FIG. 3B, in the present embodiment, light emission of the light emitter is stopped during the period when the light modulation device is turned off, and light emission is performed during the period when the light modulation device is turned on. I am letting. By dispersing and emitting light in this way, the number of control bits for controlling the ON period held in the control of the light emission period can be reduced as described later, compared to the case of continuously emitting light. .

  In the above description, the image is described as one pixel for the sake of simplicity. However, in the case of a plurality of pixels, light emission of the light emitter may be stopped during a period in which the light modulation device is turned off for all pixels. In general, when the entire image is dark, the period during which the light modulation device is turned off increases for all pixels, and when the entire image is bright, the period during which the light modulation device is turned off for all pixels decreases. Therefore, in the present embodiment, in the case of a dark image, the period during which light emission is stopped increases compared to the case of a bright image. In this way, by analyzing the input image data and controlling the light emission timing so that the light emitter does not emit light for the period in which the light modulation device is turned off in all pixels, without changing the maximum brightness, Energy consumption can be reduced.

  Next, a method for controlling the light emission period of the present embodiment will be specifically described. The input image data is assumed to be composed of three types of data for each pixel: color data R (x, y), color data G (x, y), and color data B (x, y). Here, the color data R (x, y), the color data G (x, y), and the color data B (x, y) are red, corresponding to each pixel in the image formed by the image display unit 3. Data values of green and blue are respectively shown, and x and y represent positions (two-dimensional coordinate values) of pixels corresponding to the data values on the screen.

  The light emission period control unit 4 emits light emitters corresponding to each color data (light emitter R11 for color data R (x, y), light emitter G12 for color data G (x, y), and color data B (x, y). ), The light emission timing of the light emitter B13) is determined, and a light emission period control signal indicating the light emission timing is output to the light source control unit 5 and the target light emission amount calculation unit 8.

  Hereinafter, the light emission period control unit 4 will be described. FIG. 4 is a diagram illustrating an internal configuration example of the light emission period control unit 4. The light emission period control unit 4 includes a light emission timing conversion unit 41 and a control signal generation unit 42.

  The light emission timing conversion unit 41 converts the input image signal into a light emission timing signal for each color data for each pixel. This conversion is performed, for example, by storing the value of each color data and the corresponding light emission timing in advance in a lookup table, reading this, and generating a light emission timing signal based on the read timing. The light emission timing corresponding to each color data value is linked with the on / off of the light modulation device, and is determined to emit light during the period when the light modulation device is turned on and not during the period when the light modulation device is turned off. To do. Therefore, the light emission timing calculation method can be the same as the method for obtaining the period during which the light modulation device is turned on in the conventional on / off control of the light modulation device.

  The light emission timing signal for each data determined here is a signal corresponding to a predetermined period (one frame), and a binarized signal indicating on (light emission) and off (light emission stop). And The light emission timing conversion unit 41 outputs a light emission timing signal of each color data for each pixel to the control signal generation unit 42.

  Here, the light emission timing is obtained using the look-up table. However, the present invention is not limited to this. For example, the light emission timing is determined based on a predetermined calculation formula based on the data value of the color data. The light emission timing signal may be determined by other methods.

  An example of the light emission timing signal will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of light emission control when the data value of input image data is 3 bits. FIG. 5A shows the brightness of the video signal when the bits of the input image data are # 1 (lower) to # 3 (upper). In this example, 8 levels of brightness from “0” to “7” can be expressed by 3-bit data. FIG. 5B shows an example of the on period of the light modulation devices corresponding to # 1 to # 3.

  As shown in FIG. 5B, for each bit of the input image data, one frame when the bit is “1” (light emission allocation period allocated to the light emitter in one frame). Suppose that the on-period is defined. The ON period of each bit is set to be an ON period that is twice the ON period of the bit lower than that bit, and the ON periods corresponding to each bit are determined so as not to overlap each other.

  FIG. 5B is an example, and the ON period corresponding to each bit is not limited to the example of FIG. 5B, and is twice as long as the ON period of the next lower bit. The ON period may be determined as long as the ON periods corresponding to the bits do not overlap each other within one frame.

  FIG. 5C shows the ON period of the light modulation device corresponding to the brightness “0” to “7” when the light emission period for each bit is determined as shown in FIG. . For example, when a continuous on period corresponding to each of brightness “0” to “7” is ensured in one frame, patterns of on periods corresponding to each stage of brightness “0” to “7” are set. Each must be retained. On the other hand, in this embodiment, the ON period may be distributed within one frame as illustrated in FIG. 3-3, but the pattern of the ON period to be retained is 3 shown in FIG. Kind is OK. Therefore, it is possible to reduce the pattern of the timing of light emission to be held while ensuring the light emission period corresponding to the brightness “0” to “7”. In the present embodiment, since the light emission period (on period) of the light emitter and the on period of the light modulation device are linked, the light emission period of the light emitter is the same as in FIG. 5 (b) and FIG. 5 (c). Depending on the brightness, any one of (c) in FIG. 5 becomes the light emission timing signal.

  The control signal generation unit 42 calculates the logical sum of the light emission timing signals for each data (for each pixel) in one frame for each color, and generates a light emission period control signal for each color. A method for generating the light emission period control signal will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of a light emission period control signal of the light emitter R11 when the number of pixels is four.

  FIG. 6A shows the relationship between video and pixels displayed by the image display unit 3. Here, as shown in FIG. 6A, it is assumed that an image is composed of four pixels of coordinate values (0, 0), (1, 0), (0, 1), and (1, 1). The brightness of the light emitter R11 corresponding to each pixel is R (0,0) = 1, R (1,0) = 0, R (0,1) = 4, R (1,1) = It will be described as being 4. Further, it is assumed that the light emission timing signal is generated based on the method for determining the on period described with reference to FIG.

  Since the light emitter R11 emits light only during the period when the light modulation device is turned on, the light emission timing signal of each pixel is as shown in FIG. When the logical sum of the light emission timing signals for each pixel shown in FIG. 6B is calculated, the result is as shown in FIG. A signal obtained by calculating a logical sum of the light emission timing signals of all the pixels as shown in FIG. 6C is a light emission period control signal.

  Thus, by calculating the light emission period control signal as the logical sum of the light emission timing signals of all the pixels, the light emission period control signal is a signal including all the periods during which any one of the pixels emits light even once. That is, the light emission period control signal of each color generated here is a signal indicating the light emission timing determined so that the light emitter does not emit light during the period in which the light modulation device is turned off in all pixels for each color. . The control signal generation unit 42 outputs the generated light emission period control signal for each color to the light source control unit 5 and the target light emission amount calculation unit 8.

  In addition, when the timing of light emission in which the light emission period is dispersed within one frame is allowed as described above, eight levels of brightness are obtained by combining three types of light emission patterns as illustrated in FIG. 5B. Can be expressed. In other words, it is not necessary to control eight types of light emission patterns when expressing eight levels of brightness, and control of three types of light emission patterns is sufficient, and the number of control bits (the number of bits used to specify the pattern) is set. Can be reduced.

  As described above, by determining the light emission timing so that light is not emitted during the period when the light modulation device is turned off in all pixels based on the input image data, the light emission period of each light emitter is minimized. Therefore, the generation of stray light can be reduced.

  On the other hand, light emitting bodies such as lasers and LEDs can change the intensity of light emission due to changes in the temperature of the element, and there are individual differences in the amount of light emission in the light emitting element itself. Have difficulty. As a result, there may be a difference between the target light emission amount and the actual light emission amount when calculating the light emission period control signal for changing the light emission period. When such a difference occurs, the color balance of the illumination light changes and the displayed image may be discolored or colored.

  For this purpose, the image display device according to the present embodiment detects the amount of illumination light emitted from each of the light emitter R11, the light emitter G12, and the light emitter B13, and calculates the actual light emission amount from the light emission period control signal. Control is performed so as to coincide with the target light emission amount that is the control target. With this control, even when the light emission period is modulated according to the video, the color balance of the video can be adjusted to be constant without depending on the fluctuation of the light emission period.

  The light emission amount detector 6 detects light emitted from the light emitter R11, light emitter G12, and light emitter B13 in synchronization with a light detection period signal output from the light source controller 5 described later, and detects each light within one frame. Detection amounts Sr, Sg, and Sb (corresponding to the light emitter R11, light emitter G12, and light emitter B13, respectively), which are the total light emission amounts emitted from the light emitter, are output.

  The light emission amount detection unit 6 distinguishes each light emitter based on the light detection period signal for each light emitter output from the light source control unit 5. Specifically, the light emission amount detection unit 6 recognizes the light emission period for each light emitter based on the light detection period signal. Then, for each recognized light emission period, the total amount of light emitted by each light emitter within one frame is obtained assuming that the light emitter corresponding to that light emission period emits light during that light emission period. Therefore, the light emission amount detection unit 6 does not need to include a plurality of sensors for detecting the light emission of each light emitter, and one sensor is installed at a position where the light from the light emitter R11, the light emitter G12, and the light emitter B13 can be detected. Thus, the light emission of each light emitter can be detected. However, the present invention is not limited thereto, and the light emission amount detection unit 6 may include a sensor that detects light emission for each light emitter.

  The reference wave height storage unit 9 stores a wave height value serving as a reference for each light emitter, and outputs the stored wave height value to the target light emission amount calculation unit 8 as a reference wave height value. In the present embodiment, the light emission amount is controlled to an optimum value by making the peak value of light emitted for each light emitter constant and adjusting the light emission period according to the image data. Therefore, the crest value for causing each light emitter to emit light is determined, for example, when the color balance is adjusted when the image display device is manufactured. The reference wave height storage unit 9 stores the detected wave height value of each light emitter detected by the sensor of the light emission amount detection unit 6 after the color balance adjustment as the reference wave height value when adjusting the color balance.

  Based on the emission period control signal for each illuminant output from the light emission period control unit 4 and the reference peak value for each illuminant output from the reference wave height storage unit 9, the target light emission amount calculation unit 8 The target light emission amount of each light emitter is calculated, and the target light emission amount is output to the wave height generation unit 7. In addition, the target light emission amount calculation unit 8 outputs the width of the light emission period calculated at the same time to the wave height generation unit 7 when calculating the target light emission amount.

  Hereinafter, the target light emission amount calculation unit 8 will be described in detail. FIG. 7 is a diagram illustrating an internal configuration example of the target light emission amount calculation unit 8. The target light emission amount calculation unit 8 includes a light emission period calculation unit 81 and a light emission amount calculation unit 82.

  Based on the light emission period control signal of each color output from the light emission period control unit 4, the light emission period calculation unit 81 is the width of the light emission period of each light emitter within one frame (if the light emission periods are dispersed, The width obtained by adding the light emission periods) is calculated, and the calculated width of the light emission period is output to the light emission amount calculation unit 82 and the wave height generation unit 7. The width of the light emission period is, for example, t + 4t = 5t in the case of (c) in FIG. 6, but the minimum period (for example, t in FIG. 6 (c)) is 1 instead of the unit of time. The unit may be expressed by a numerical value (“5” in the case of FIG. 6C).

  The light emission amount calculation unit 82 calculates a target light emission amount serving as a control target for each light emitter based on the width of the light emission period output from the light emission period calculation unit 81 and the reference peak value. The target light emission amount is calculated as, for example, the width of the light emission period × the reference peak value. A table reference method may be used in which the relationship between the width of the light emission period and the target light emission amount is obtained in advance and stored as a table, and the target light emission amount is obtained by referring to the table.

  As described above, in this embodiment, since the width of the light emission period and the light emission amount are calculated according to the input image data, the target light emission amount serving as a control target can be obtained as the light emission amount according to the image data. it can.

  The wave height generation unit 7 determines the driving wave height value so that the detection amounts Sr, Sg, and Sb of the respective light emitters output from the light emission amount detection unit 6 respectively match the corresponding target light emission amounts. In the present embodiment, since the light emission period is determined to be optimal based on the input image data, the peak value is corrected so as to match the target light emission amount. However, the present invention is not limited to this, and instead of correcting the peak value, the light emission period may be corrected so that the detected amounts Sr, Sg, Sb match the corresponding target light emission amounts.

  Hereinafter, the wave height generation unit 7 will be described. FIG. 8 is a diagram illustrating an internal configuration example of the wave height generation unit 7. The pulse height generation unit 7 includes a difference calculation unit 71, a peak value calculation unit 72, and a driving peak value conversion unit 73.

The difference calculation unit 71 obtains a difference in light emission amount based on the target light emission amount and the detection amount for each light emitter, and outputs the difference in light emission amount to the peak value calculation unit 72. The difference in the light emission amount can be calculated as the detection amount−the target light emission amount. The peak value calculation unit 72 calculates a differential peak value corresponding to the difference in light emission amount output from the difference calculation unit 71 and outputs the differential peak value to the driving peak value conversion unit 73. The difference peak value can be calculated based on the following formula (1) based on the width of the light emission period output from the target light emission amount calculation unit 8 and the difference between the light emission amounts output from the difference calculation unit 71. it can.
Difference peak value = difference in light emission amount / width of light emission period (1)

  The driving peak value converter 73 obtains a driving peak value representing the magnitude of the current for causing the light emitter to emit light based on the differential peak value. The differential peak value calculated by the correction value calculation unit 72 is a differential peak value obtained based on the detection amount of the sensor. In order to control the light emission of the light emitter, the differential peak value obtained from the detection amount of the sensor must be converted into a drive peak value indicating the magnitude of the current that causes the light emitter to emit light. In this conversion, for example, the magnitude of the current for causing the light emitter corresponding to the differential peak value to emit light is obtained in advance and held as a table, and the differential peak value is converted into the differential driving peak value by reading the table. To implement.

  In addition, the driving peak value conversion unit 73 stores a reference driving peak value that is a magnitude of a reference current for causing each light emitter to emit light, and a value obtained by adding the reference driving peak value to the differential driving peak value is a driving peak value. Output as. As the reference driving peak value, for example, the peak value (driving peak value) of the control signal input to each light emitter immediately after the color balance adjustment at the time of manufacturing the image display device is used.

  The light source controller 5 emits light for each light emitter based on the light emission period control signal for each light emitter output from the light emission period controller 4 and the driving wave height value for each light emitter output from the wave height generator 7. A drive signal is output. The light source control unit 5 outputs a light detection period signal indicating the light emission period of each light emitter in synchronization with the light emission period control signal for each light emitter.

  Hereinafter, the light source control unit 5 will be described. FIG. 9 is a diagram illustrating an internal configuration example of the light source control unit 5. The light source control unit 5 includes a light emission drive signal generation unit 51 and a light detection period signal generation unit 52.

  The light emission drive signal generation unit 51 is provided for each light emitter based on the light emission period control signal for each light emitter output from the light emission period controller 4 and the drive peak value for each light emitter output from the wave height generator 7. The light emission drive signals (corresponding to the light emitter R11, the light emitter G12, and the light emitter B13, respectively) so that the peak value during the light emission period indicated in the light emission period control signal becomes the drive peak value output from the wave height generator 7. A light emission drive signal R, a light emission drive signal G, and a light emission drive signal B). The light emission drive signal generation unit 51 outputs the light emission drive signal R, the light emission drive signal G, and the light emission drive signal B to the corresponding light emitters (light emitter R11, light emitter G12, light emitter B13). That is, the generated wave height of each light emission driving signal is a value that controls the light emission wave height value of each light emitting body, and the light emission wave height of each light emitting body is changed by the change in the wave height of each light emission driving signal. Thus, for each light emitter, control is performed so that the total light emission amount emitted in one frame matches the target light emission amount for each corresponding light emitter.

  As an example, a light emission waveform (light emission drive signal) of one frame of each of the light emitters R, G, and B controlled by the light source controller 5 when the drive peak value is constant will be described with reference to FIG. FIG. 10 is a diagram illustrating an example of a light emission drive signal for each light emitter generated by the light source control unit 5. In FIG. 10, the light emission drive signal R, the light emission drive signal G, the light emission drive signal B, and the state of the light modulation device are shown in order from the top.

  As shown in FIG. 10, one frame is divided into light emission assignment periods (subframes) 10r, 10g, and 10b assigned to each light emitter in a time division manner. Each light emitter always emits light within the light emission allocation periods 10r, 10g, and 10b when displaying at the maximum brightness. In the example of FIG. 10, each light emitter does not emit light during the period indicated by the dotted line in the light emission allocation periods 10r, 10g, and 10b. Further, the heights of the light emission drive signal R, the light emission drive signal G, and the light emission drive signal B (the difference between the value of the signal in the off period (non-light emission period) and the value of the signal in the on period (light emission period)) are the drive waves. It shows a high price.

  As described above, the light emission drive signal generation unit 51 generates the light emission drive signal R, the light emission drive signal G, and the light emission drive signal B based on the light emission period control signal output from the light emission period control unit 4. The light emission drive signal R, the light emission drive signal G, and the light emission drive signal B are output to the corresponding light emitter R11, light emitter G12, and light emitter B13, respectively.

  The light detection period signal generator 52 adjusts the timing so that the light emission period control signal of each light emitter is synchronized with the light emission drive signal output from the light emission drive signal generator 51, and indicates the light emission period for each light emitter. The light emission amount detection unit 6 outputs the light detection period signal.

  In this embodiment, the case where DMD (registered trademark) is used as the light modulation device has been described. However, the present invention is not limited to this as long as it is a light modulation device that determines the brightness according to the ratio between the on period and the off period. Alternatively, the light modulation device may be used.

  In the present embodiment, as a method of controlling the light emission period according to the input image, the light emission period is controlled in synchronization with the on period of the light modulation device (each light emitter is not caused to emit light during the light modulation device off period). Although the method has been described, any other method may be used as long as it is a method for controlling the light emission period according to the input image. For example, a method of changing the length of the light emission allocation period allocated to each color according to the brightness of the input image may be used. In that case, the light emission period control signal is generated as a signal indicating the light emission period based on the control method.

  In the present embodiment, an example is shown in which three types of light emitters having different colors are used as the light source 1 on the assumption that a color image is displayed. However, the operation of the present embodiment is also performed in the case of a monochromatic light source. May be applied. In that case, it is not necessary to divide one frame for each light emitter, and the light emission period and light emission amount in the frame may be controlled in the same manner as the control method for each light emitter in this embodiment.

  As described above, in the image display device according to the present embodiment, the light emission period of each light emitter is determined based on the input image data, the light emission amount detector 6 detects the light emission amount of each light emitter, and the target light emission amount. The calculation unit 8 obtains the target light emission amount based on the light emission period and the reference peak value, and the light source control unit 5 controls the light emitter so that the detected light emission amount matches the target light emission amount. For this reason, the light emission amount can be accurately controlled so as to be the target light emission amount calculated according to the video, and the color balance of the video can be adjusted to be constant without depending on the fluctuation of the light emission period.

  Further, in the present embodiment, the light emitters are prevented from emitting light during a period in which video display is not performed. For this reason, when the input image is bright, the light emission period of each light emitter is long, and when it is dark, the light emission period is short. Thus, each light emitter is always lit by providing a light extinction period that does not emit light according to the image. Power consumption can be reduced and stray light can be reduced as compared with conventional ones, and a reduction in contrast can be suppressed.

Embodiment 2. FIG.
FIG. 11 is a diagram illustrating a functional configuration example of the image display apparatus according to the second embodiment of the present invention. The image display apparatus according to the present embodiment is the same as the image display apparatus according to the first embodiment except that the light emission period control unit 4 of the image display apparatus according to the first embodiment is replaced with a light emission period control unit 4a. Components having the same functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  In the first embodiment, the light emission period control unit 4 determines the light emission timing so that the light emitter does not emit light in the period in which the light modulation device is turned off in all pixels for each color according to the input image data. In the present embodiment, a lower limit value (minimum width) is provided in the light emission period, and when the light emission period obtained according to the input image data is equal to or lower than the lower limit value, the light emission period is determined to be the lower limit value. .

  When the light emission period is controlled according to the input image data, the light emission period of the light emitter can be shortened in a dark image or the like. On the other hand, when the light emission period is short to some extent, the light amount detected by the light emission amount detection unit 6 becomes insufficient, and is easily affected by disturbances such as circuit noise, making it difficult to accurately detect the light emission amount. In order to avoid this problem, in this embodiment, a minimum width is provided in the light emission period, and when the light emission period calculated from the image data is equal to or smaller than the minimum width, the minimum width is set as the light emission period. The minimum width is set in advance as a period in which the influence of circuit noise or the like is not problematic in practice. In this way, by always setting the light emission period to a certain width or more, the light emission quantity detection unit 6 can accurately detect the light emission quantity without depending on the fluctuation of the light emission period. As for the minimum width, a different value may be used for each light emitter, or the same value may be used regardless of the light emitter.

  FIG. 12 is a diagram illustrating a configuration example of the light emission period control unit 4a according to the present embodiment. The light emission period control unit 4 a includes a light emission timing conversion unit 41, a control signal generation unit 42, a light emission period calculation unit 43, and a light emission period control signal determination unit 44. The light emission timing conversion unit 41 and the control signal generation unit 42 are the same as in the first embodiment, convert input image data into a light emission timing signal for each color data, and the light emission timing signal for each data within one frame. A logical sum is calculated for each color, and a light emission period control signal corresponding to the image data is generated for each light emitter. In this embodiment, this light emission period control signal is used as a temporary light emission period control signal.

  The light emission period calculation unit 43 calculates the light emission period of each light emitter in one frame according to the provisional light emission period control signal and outputs the light emission period control signal determination unit 44 to the light emission period control signal determination unit 44. Here, it is assumed that one frame is divided into three light emission allocation periods, and different light emission allocation periods are allocated to the respective light emitters.

  The light emission period control signal determination unit 44 holds the minimum width that is the lower limit value of the light emission period, and compares the light emission period for each light emitting body output from the light emission period calculation unit 43 with the minimum width. For light emitters larger than the small width, the provisional light emission period control signal of the corresponding light emitter output from the control signal generator 42 is output as it is as the light emission period control signal.

  On the other hand, the light emission period control signal determination unit 44 includes the light emission periods indicated by the temporary light emission period control signal of the light emitters for which the light emission period output from the light emission period calculation unit 43 is less than the minimum width, The temporary light emission period control signal is corrected so that the light emission period becomes the minimum width and the light emission period falls within the light emission allocation period, and the corrected signal is output as the light emission period control signal. For example, the light emission period indicated by the temporary light emission period control signal is matched with the light emission start point, and the temporary light emission period control signal is corrected so that the light emission period has the minimum width, or the center of the light emission period indicated by the temporary light emission period control signal And the light emission period including the light emission period indicated by the temporary light emission period control signal is not limited thereto. As long as the correction method is such that the width is the minimum width and the light emission period is within the light emission allocation period, any method may be used.

  Here, the timing of light emission when the light emission period has the minimum width will be described with reference to FIG. FIG. 13 is a diagram illustrating an example of a temporary light emission period control signal and a light emission period control signal. 13A shows a temporary light emission period control signal, and FIG. 13B shows a light emission period control signal after the temporary light emission period control signal shown in FIG. 13A is corrected. . Here, a description will be given assuming that the minimum width is 5t as an example.

  In the case of the temporary light emission period control signal as shown in FIG. 13A, the light emission period output from the light emission period calculator 43 is 4t. The light emission period control signal determination unit 44 determines that the light emission period is 5t because the light emission period 4t of the temporary light emission period control signal is equal to or less than the minimum width 5t of the light emission period, and the temporary light emission period control signal in FIG. The light emission timing is corrected so that the light emission period becomes 5t including the light emission timing shown in FIG. 13, and a light emission period control signal as shown in FIG. 13B is generated. Here, the start point of the light emission period of the temporary light emission period control signal is corrected to match the corrected light emission period.

  On the other hand, the excess light emission period, which is the light emission period extended by the light emission period control signal determination unit 44 to be the minimum width, exceeds the light emission period indicated by the temporary light emission period control signal, Become. Therefore, when the light emission period control signal determination unit 44 corrects the light emission period to have the minimum width, if the light emission periods of the same color are dispersed within one frame (one light emission allocation period), FIG. As shown in (b), it is desirable to determine the timing of light emission so that the short light emission period is as long as possible, and so that the interval between intermittent light emission (the period of no light emission between the light emission period and the light emission period) is as short as possible. . Thus, by determining the light emission timing so that the light emission period is long and continuous, even when intermittent light emission is performed, it is less likely to be affected by disturbances such as circuit noise. The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  Thus, in the image display device according to the present embodiment, the light emission period of each light emitter is provided with a minimum width, and the light emission period is maximized when the light emission period determined by the input image data is shorter than the minimum width. Modified to narrow. Therefore, the same effects as those of the first embodiment can be obtained, and the light emission amount can be detected more accurately than the first embodiment because it is less susceptible to disturbances such as circuit noise. Therefore, even when the light emission period based on the input image data is short, the light emission amount can be controlled with higher accuracy, and the color balance of the video can be adjusted to be constant without depending on the fluctuation of the light emission period.

  As described above, the image display apparatus and the image display method according to the present invention are useful for an image display apparatus using a light modulation device, and are particularly suitable for an image display apparatus using DMD (registered trademark) as a light modulation device. Yes.

DESCRIPTION OF SYMBOLS 1 Light source 2 Illumination part 3 Image display part 4, 4a Light emission period control part 5 Light source control part 6 Light emission amount detection part 7 Wave height generation part 8 Target light emission amount calculation part 9 Reference | standard wave height memory | storage part 11 Light emitter R
12 Light emitter G
13 Light emitter B
41 light emission timing conversion unit 42 control signal generation unit 43 light emission period calculation unit 44 light emission period control signal determination unit 51 light emission drive signal generation unit 52 light detection period signal generation unit 71 difference calculation unit 72 wave height value calculation unit 73 drive wave height value conversion unit 81 Light emission period calculation unit 82 Light emission amount calculation unit 10r, 10g, 10b Light emission allocation period

Claims (14)

A light source that emits light of one or more colors;
An image display unit that modulates light emitted from the light source for each pixel and displays the modulation result as an image;
A light emission period control unit that determines a light emission period, which is a period during which the light source emits light, for each pixel, based on input image data;
A light emission amount detection unit that detects the light emission amount of the light emitted from the light source as a detection light emission amount;
A target light emission amount calculation unit that calculates a target light emission amount that is a control target value of the light emission amount of light emitted from the light source, based on the light emission period and a predetermined reference peak value;
A light source control unit that controls the light source so that the detected light emission amount becomes the target light emission amount;
An image display device comprising: The image display unit
Based on the image data, for each pixel, a ratio between a display state in which the light emitted from the light source is displayed as an image and a non-display state in which the light emitted from the light source is not displayed as an image. A light modulator that modulates the light emitted by the light source by determining and controlling itself to be in the display state or the non-display state based on the ratio;
With
The light emission period control unit determines a period during which the light modulation unit is in the display state as the light emission period.
The image display apparatus according to claim 1. The light modulation unit is a reflection type image display element including a minute mirror corresponding to the pixel, and the display state and the non-display state are determined by inclination of the minute mirror of the reflection type image display element.
The image display device according to claim 2. The light source is
A plurality of light emitters that emit light of different colors,
With
The light emission period control unit determines the light emission period for each of the light emitters based on the image data,
The light emission amount detection unit detects the detected light emission amount for each of the light emitters,
The target light emission amount calculation unit calculates the target light emission amount for each of the light emitters,
The light source control unit controls the detected light emission amount to be the target light emission amount for each of the light emitters;
The image display device according to claim 1, 2, or 3. For each of the light emitters, a predetermined period is divided into a plurality of light emission assignment periods, and the light emission assignment periods different for each of the light emitters are assigned.
The light emission period control unit determines the light emission period within a light emission allocation period allocated to each light emitter;
The image display device according to claim 4. For each bit representing the data value of the image data, a bit unit emission period, which is a period during which the light source emits light within the emission allocation period when the bit is a value of 1, is determined.
The light emission period control unit holds the bit unit light emission period for each bit, and performs a logical OR operation on all bits of the bit unit light emission period corresponding to a bit having a data value of 1 in the image data. Period
The image display device according to claim 5. The light emission period control unit determines the light emission period within the predetermined period when the light emission period determined based on the image data within the predetermined period is equal to or less than a predetermined minimum value for each of the light emitters. Re-determining the emission period to be the minimum value;
The image display device according to claim 4, 5 or 6. The light emission period controller is
A light emission timing conversion unit that generates a light emission timing signal indicating a period during which the light emitter should emit light in the pixel based on a predetermined rule from the image data for each light emitter and for each pixel;
A control signal generation unit that generates a light emission period control signal indicating the light emission period based on the light emission timing signal for each pixel, for each of the light emitters;
The image display apparatus according to claim 4, 5 or 6. The light emission period controller is
A light emission timing conversion unit that generates a light emission timing signal indicating a period during which the light emitter should emit light in the pixel based on a predetermined rule from the image data for each light emitter and for each pixel;
A control signal generation unit that generates a temporary light emission period control signal indicating the light emission period based on the light emission timing signal for each pixel, for each of the light emitters;
A light emission period calculation unit that calculates an intra-frame light emission period that is the predetermined light emission period based on the temporary light emission period control signal for each of the light emitters;
A light emission period control signal that determines a light emission period control signal so that the light emission period within the predetermined period is set to the minimum value based on the temporary light emission period control signal when the light emission period within the frame is equal to or less than the minimum value. A decision unit;
The image display apparatus according to claim 7, further comprising: The control signal generation unit generates the light emission period control signal as a logical sum of all the pixels of the light emission timing signal for each pixel.
The image display device according to claim 8, wherein the image display device is an image display device. The target light emission amount calculation unit
A light emission period calculation unit that calculates the light emission period in one frame based on the light emission period control signal for each light emitter;
A target light emission amount calculation unit for calculating the target light emission amount based on the light emission period and the reference peak value for each of the light emitters;
The image display apparatus according to claim 8, comprising: For each of the light emitters, a difference calculation unit for obtaining a difference between the target light emission amount and the light emission amount;
For each of the light emitters, a peak value calculation unit that converts the difference into a peak value difference that is a difference in peak values;
A driving peak value conversion unit that converts the peak value difference into a driving peak value that represents the magnitude of current for controlling the amount of light emitted from the light source for each of the light emitters;
A wave height generator comprising:
Further comprising
The light source control unit controls the light source based on the driving peak value;
The image display device according to claim 11. The light source controller is
A light emission drive signal generation unit that determines the light emission period based on the light emission period control signal for each light emitter, and generates a light emission drive signal in which the peak value of the light emission period becomes the drive peak value;
A light detection period signal generation unit that generates a light detection period signal indicating the light emission period for each light emitter based on the light emission period control signal;
With
The light emission amount detection unit detects the detected light emission amount based on the light detection period signal.
The image display device according to claim 12. A light emission period control step for determining a light emission period, which is a period during which the light source emits light, for each pixel based on input image data;
A target light emission amount calculating step of calculating a target light emission amount, which is a control target value of the light emission amount of light emitted from the light source, based on the light emission period and a predetermined reference peak value;
An emission step in which the light source emits light of one or more colors;
An image display step of modulating the light emitted in the emission step for each pixel and displaying the modulation result as an image;
A light emission amount detection step for detecting the light emission amount of the light emitted in the emission step as a detection amount;
A light amount control step for controlling the light amount of light emitted in the emission step so that the detected amount becomes the target light emission amount;
An image display method comprising:

Images