JP2008281707A - Color image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image display device capable of improving visibility by suppressing the occurrence of a color-breakage phenomenon. <P>SOLUTION: The color image display device includes: a plurality of light sources 2, 3, 4 which emit light rays of different colors; an optical modulation part 7 which modulates the light rays from the plurality of light sources 2, 3, 4; and a sub-frame control part 9 which controls the light sources 2, 3, 4 and the optical modulation part 7 by assigning sub-frame times to respective sub-frame image data in accordance with sizes of a plurality of input sub-frame image data with different colors, wherein the sub-frame control part 9 shortens the sub-frame time assigned to the respective sub-frame image data in accordance with the reduction of the sub-frame image data. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color image display device.

Conventionally, a single-plate DLP type color image display apparatus uses a sequential color system and uses a DMD (Digital Micromirror).
Device) A single plate is illuminated with RGB light to display a color image. At that time, since the illumination light from the lamp of the white light source is converted into RGB light by the rotating color filter turret and sequentially emitted, the subframe time of each color is fixed (for example, see Patent Documents 1 to 4). .)

Japanese Patent No. 3645350 JP 2003-241714 A JP 2003-102030 A JP 2003-284088 A

  However, in the case of the sequential color method, light of the three primary colors such as RGB light is sequentially emitted, and therefore, when the eye movement is performed rapidly, the separation of the three primary colors, that is, a so-called color break phenomenon occurs around the image. There is. Since the color break phenomenon leads to eye strain and mental stress, it is preferable to suppress it as much as possible.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a color image display device capable of suppressing the occurrence of a color break phenomenon and improving the visibility.

In order to achieve the above object, the present invention provides the following means.
The present invention provides a plurality of light sources that emit light of different colors, a light modulation unit that modulates light from the plurality of light sources, and a plurality of input sub-frame image data of different colors. A subframe control unit that controls the light source and the light modulation unit by allocating a subframe time to subframe image data;
The subframe control unit provides a color image display device that shortens a subframe time allocated to each subframe image data as the subframe image data becomes smaller.

  According to the present invention, when subframe image data of a plurality of different colors is input to the subframe control unit, a subframe time is allocated to each subframe image data according to the size of each subframe image data. It is done. The subframe time is shortened when the subframe image data is small, the display time for each color can be further shortened, and the occurrence of the color break phenomenon can be suppressed.

  In the above invention, the sub-frame control unit analyzes gradation values of a plurality of pixels in the sub-frame image data for each color, multiplies the data gain by the sub-frame image data of each color, and outputs the result to the light modulation unit. A scaling unit and a lighting control unit that controls to turn on the light source according to the subframe time may be provided.

  By doing so, the operation of the image signal analysis unit analyzes the gradation values of a plurality of pixels of the input subframe image data for each color, and outputs the data gain and subframe time for each color. Then, by the operation of the scaling unit, the data gain is multiplied by the sub-frame image data of each color and output to the light modulation unit. Further, the light source is turned on according to the subframe time. As a result, light of a light amount corresponding to each subframe time is emitted from a plurality of light sources, and the light is obtained so that the gradation value is achieved by the data obtained by multiplying the subframe image data and the data gain. The modulator is activated.

In the above invention, the image signal analysis unit detects a maximum value of gradation values of a plurality of pixels in the subframe image data for each color, and sets a subframe time corresponding to the detected maximum value for each color. A value obtained by dividing the upper limit value of the input subframe image data by the detected maximum value for each color may be output as the data gain.
In this way, for example, when the maximum value for each color is small, the data gain is set large and the subframe time is set short, so the display period is shortened and the color break phenomenon (color separation is performed). Occurrence of a rainbow-colored phenomenon) can be suppressed. In addition, energy saving can be achieved by minimizing the lighting time of the light source, and stray light can be reduced to prevent a decrease in image contrast.

In the above invention, the frame time, which is one period of time for displaying the sub-frame image data of all the different colors, is constant, and the total of the sub-frame times output from the image signal analysis unit is shorter than the frame time. In this case, a non-display time during which the light source is not turned on may be provided.
In this way, it is possible to handle a moving image with a fixed frame time. In each frame provided with a non-display time, the display period is shortened, so that the occurrence of a color break phenomenon can be suppressed.

In the above invention, display of all subframe images may be repeated when the total subframe time output from the image signal analysis unit is shorter than half of the frame time.
Even in this way, it is possible to handle moving images with a fixed frame time, suppress the color break phenomenon, and display repeatedly using the free time to express gradation in one frame. Can be improved.

  According to the present invention, it is possible to suppress the occurrence of the color break phenomenon and improve the visibility.

A color image display device 1 according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
As shown in FIG. 1, the color image display device 1 according to this embodiment includes three light sources 2, 3, and 4 that can emit light of RGB three primary colors, and light from the light sources 2, 3, and 4, respectively. A combining prism 5 to combine, an illumination optical system 6 that enhances directivity while guiding the light combined in the same optical path by the combining prism 5, and a liquid crystal element (light) disposed at the exit of the illumination optical system 6 A modulation unit 7, a projection lens 8 that projects light transmitted through the liquid crystal element 7, and a subframe control unit 9 that controls the light sources 2, 3, and 4 and the liquid crystal element 7.
The light sources 2, 3, 4 are, for example, LEDs 2 a, 3 a, 4 a, driving units 2 b, 3 b, 4 b that drive and control the LEDs 2 a, 3 a, 4 a and light from the LEDs 2 a, 3 a, 4 a in one direction, respectively. Reflectors 2c, 3c, and 4c that are directed toward the surface.

The sub-frame control unit 9 analyzes input frame image data and determines a data gain (Gr, Gg, Gb) and a sub-frame time (Fr, Fg, Fb), A scaling unit 11 that generates subframe image data based on the input frame image data and the data gain (Gr, Gg, Gb) and outputs the subframe image data to the liquid crystal element 7, and the determined subframe time (Fr, Fg) , Fb) and a lighting control unit 12 for driving the driving units 2b, 3b, 4b.
Here, the input frame image data will be described below on the assumption that it consists of image data obtained by separating a color image into three colors of red (R), green (G), and blue (B). The input frame image data is not limited to RGB, and may be a color image such as YCrCb, for example. When YCrCb color image data is input, a process of converting YCrCb to RGB may be added at the input stage of the subframe control unit 9.

The image signal analysis unit 10 analyzes the gradation values of all the pixels of the subframe image data for each color and detects the maximum values (Rmax, Gmax, Bmax). Then, the data gain (Gr, Gg, Gb) and the subframe time (Fr, Fg, Fb) are output according to the detected maximum value.
Here, the R, G, B maximum values are obtained by normalization so that the maximum gradation value (hereinafter referred to as the upper limit value) that can be expressed by the image data is 1, and will be described later. It is the same.
Here, the data gain (Gr, Gg, Gb) is determined by calculating the value obtained by dividing the upper limit value 1 by the maximum value, that is, the reciprocal of the maximum value. On the other hand, the subframe time (Fr, Fg, Fb) is determined by multiplying the prescribed value of the subframe time by the maximum value.

  The prescribed value of the subframe time will be described with reference to FIG. The specified value of the subframe time is such that when the data gains (Gr, Gg, Gb) of the three RGB colors are equal to each other, the combined light of the RGB three colors becomes white, that is, the light source light quantity and the light modulation unit This is the ratio of RGB subframe times determined so that the white balance is matched in consideration of the transmittance and the like. The specified value of each RGB subframe time is 1 which is the longest subframe time of RGB. Normalize as follows. In the following, for the sake of simplicity, the specified value for each subframe time is set to 1 for all three RGB colors.

The first frame is a case where the detected maximum value is (Rmax, Gmax, Bmax) = (1, 1, 1), and the subframe time (Fr, Fg, Fb) of each color is the reciprocal of the maximum value. (1,1,1) of the frame time is multiplied by a prescribed value (1,1,1) of the frame time.

  Next, in the second frame, the detected maximum value is (Rmax, Gmax, Bmax) = (1, 1, 0.5), and the subframe times (Fr, Fg, Fb) of the respective colors. ) Is determined as (1, 1, 0.5).

  As a result, the sum of the subframe times (Fr, Fg, Fb) of all colors is (2.5) compared with the case of (Fr, Fg, Fb) = (1, 1, 1) of the first frame. / 3 times shorter.

  Further, in the third frame, the detected maximum value is (Rmax, Gmax, Bmax) = (0.3, 0.7, 0.5), and the subframe time (Fr, Fg, Fb) is determined such that (Fr, Fg, Fb) = (0.3, 0.7, 0.5). As a result, the sum of the sub-frame times (Fr, Fg, Fb) for all colors is halved compared to the case of (Fr, Fg, Fb) = (1, 1, 1) in the first frame. Shortened.

  In the image signal analysis unit 10, a synchronization signal is generated according to the determined subframe time (Fr, Fg, Fb), and the determined subframe time (Fr, Fg, Fb) and the synchronization signal are scaled to be described later. Output to the unit 11 and the lighting control unit 12.

  Next, an example in which the data gain (Gr, Gg, Gb) is output according to the maximum value will be described with reference to FIG.

  Since the data gain (Gr, Gg, Gb) is the reciprocal of the maximum value of each frame image data, in the case of the first frame, (Gr, Gg, Gb) = (1, 1, 1), in the case of the second frame , (Gr, Gg, Gb) = (1, 1, 1 / 0.5), and in the case of the third frame, (Gr, Gg, Gb) = (1 / 0.3, 1 / 0.7, 1 / 0.5). The determined data gain is output to the scaling unit 11.

The scaling unit 11 multiplies the frame image data by the data gain (Gr, Gg, Gb) output from the image signal analysis unit 10 to generate subframe image data, and outputs the subframe image data to the liquid crystal element 7. It has become.
Further, the scaling unit 11 outputs the subframe image data to the liquid crystal element 7 in synchronization with the synchronization signal generated according to the subframe time (Fr, Fg, Fb) output from the image signal analysis unit 10. It is like that.

  The lighting control unit 12 uses the subframe time (Fr, Fg, Fb) and the synchronization signal input from the image signal analysis unit 10 and uses the subframe time (Fr, Fg) at the timing synchronized with the synchronization signal. , Fb), a command signal is output to the drive units 2b, 3b, 4b so that the LEDs 2a, 3a, 4a are lit.

The operation of the color image display device 1 according to this embodiment configured as described above will be described.
When the frame image data is input, the data gain (Gr, Gg, Gb) and the subframe time (Fr, Fg, Fb) are determined by the operation of the image signal analysis unit 10, and the subframe time (Fr, Fg, Fb) is determined. A synchronization signal is generated based on Fb). The determined data gain (Gr, Gg, Gb) and the synchronization signal are sent to the scaling unit 11, and the subframe time (Fr, Fg, Fb) and the synchronization signal are sent to the lighting control unit 12.

In the scaling unit 11, subframe image data is generated by multiplying the input frame image data by a data gain (Gr, Gg, Gb), and in synchronization with the synchronization signal input from the image signal analysis unit 10. It is output to the liquid crystal element 7.
In the lighting control unit 12, the LEDs 2a, 3a, 4a are turned on over the same input subframe time (Fr, Fg, Fb) in synchronization with the synchronization signal input from the image signal analysis unit 10.

  In this case, according to the color image display device 1 according to the present embodiment, since the subframe time (Fr, Fg, Fb) is determined by the size of the input frame image data, the frame image data is small. In this case, the subframe image data is displayed with a short subframe time (Fr, Fg, Fb). As a result, the display time for each color can be further shortened, and the occurrence of the color break phenomenon can be suppressed.

  Further, according to the color image display device 1 according to the present embodiment, the data gain (Gr, Gg, Gb) is obtained by dividing the upper limit value of the input sub-frame image data of each color by the detected maximum value for each color. Therefore, for a color with a large maximum value, a small data gain (Gr, Gg, Gb) is multiplied to reduce the supply current to the LEDs 2a, 3a, 4a. Instead, since an image is displayed with a subframe time (Fr, Fg, Fb) corresponding to the maximum value, a long subframe time (Fr, Fg, Fb) is set for a color with a large maximum value.

  As a result, an output image corresponding to the input frame image data can be displayed. Further, it is possible to improve the gradation expressing ability within one frame of a color having a large maximum value. Furthermore, since the power supplied to the LEDs 2a, 3a, 4a is reduced, the light emission efficiency can be improved. Moreover, since the light emission time of the LEDs 2a, 3a, 4a can be minimized, it is effective for energy saving.

  In the present embodiment, when the frame image data is small, the subframe time (Fr, Fg, Fb) of each color is shortened and the total frame time itself is shortened. Instead of this, as shown in FIG. 3, it is possible to provide a turn-off time Ts during which the LEDs 2a, 3a, 4a are not turned on, and to make the frame time constant. In this way, the present invention can be applied even when the frame time is kept constant and the frame image data is a moving image. Moreover, by doing in this way, since a light extinction time increases compared with what always lights, stray light can be reduced and the contrast fall can be suppressed.

  In the present embodiment, as shown in FIG. 4, the ratio is extended while maintaining the ratio of the subframe times (Fr, Fg, Fb) for each color (in the example shown in FIG. 4, it is increased to 10/7). Instead, the light quantity of the light sources 2, 3, and 4 may be reduced by that amount (7/10 times). In this way, further energy saving can be achieved.

  Further, when the sum of the subframe times (Fr, Fg, Fb) is less than half of the frame time, the output of the subframe image data may be repeated as shown in FIG. In this way, the gradation expression power can be improved. In addition, when the integral multiple of the sum of the subframe times (Fr, Fg, Fb) does not become the frame time, the remaining time can be used as the non-display time Ts, and the frame time can be kept constant, so that the video can be handled. This is the same as described above.

Further, in the present embodiment, the liquid crystal element 7 is exemplified as the light modulation unit, but it goes without saying that a DMD may be employed instead.
In this embodiment, when determining the data gain (Gr, Gg, Gb) and the subframe time (Fr, Fg, Fb), the frame image data is analyzed for each color, and the maximum gradation value of all the pixels is obtained. Instead of this, instead of this, a histogram for each color of all pixels may be calculated, and for example, a value obtained by obtaining 1% of values in descending order for each of RGB may be detected. Further, since the pixels of 1% or more in the descending order cannot be expressed, it is preferable to perform a clipping process that is visually unnoticeable.

In addition, although the three LEDs 2a, 3a, and 4a that emit RGB light are used as the light source, RGMCY, RGBY, RGBCYM, or the like may be used instead.
Here, in a so-called sequential color display method for displaying a color image by sequentially outputting light of a predetermined number of colors such as three different colors of RGB which are sequentially changed to the liquid crystal element 7, brightness, color gamut, and color balance are different. A technique for freely switching display modes will be described.

  The color image display device 20 shown in FIG. 6 includes a storage unit 21 for storing a sequence pattern, a mode switching unit 22 for selecting a display mode, and a sequence pattern corresponding to the display mode switched by the mode switching unit 22. A light source control unit 23 that controls the light sources 2a, 3a, and 4a, and a light modulation control unit 24 that outputs light modulation data obtained by color-separating the input frame image data to the liquid crystal element 7 according to the sequence pattern. I have.

  The mode switching unit 22 includes, for example, a display mode selection button on an operation panel (not shown), and reads a sequence pattern from the storage unit 21 according to the display mode designated by pressing the mode button. The read sequence pattern is input to the light source control unit 23 and the light modulation control unit 24 and set to the designated display mode.

The light source control unit 23 drives the drive units 2b, 3b, 4b of the LEDs 2a, 3a, 4a according to the sequence pattern, and generates R + G, R + B, G + B, R + G + B light in addition to R, G, B light. It can be done.
Table 1 shows an example of a sequence pattern stored in the storage unit 21.

In Table 1, I indicates a sequence pattern. T defines the subframe time, and divides the frame time to indicate the respective time ratios.
These sequence patterns P1 to P5 are shown in FIG.

  For example, the sequence pattern P1 in Table 1 is a display pattern that lights in the order of R, G, and B, and the frame time is divided into 1: 2: 1, and the sub-frame time (Fr, Fg, Fb) of each color. It is what. In the period of 1: 2: 1, if one frame time is 1/60 seconds, only the R light LED 2a is lit for 1/240 seconds, only the G light LED 3a is lit for 2/240 seconds, and the B light LED 4a is lighted. Is a subframe time (Fr, Fg, Fb) of 1/240 seconds.

  According to this, the sequence pattern P1 is a standard display pattern, and the sequence pattern P2 indicates a sequence pattern in MYC color order. In this display pattern, the color gamut is about 1/3 of the sequence pattern P1 and the brightness is about twice. A sequence pattern P3 indicates an RGBCYM sequence pattern. Although it is the same as the sequence pattern P1 on the chromaticity diagram, the color gamut including the luminance direction is narrowed, and the brightness is 1.5 times. The sequence pattern P4. P5 is a display pattern that has the same color gamut as the sequence pattern P3, but has a brightness that is about 1.5 times that of the sequence pattern P1, and can extend the G light emission time. .

  That is, as compared with the standard sequence pattern P1, the sequence pattern P2 can be brightest, and the sequence pattern P3 can be brightened 1.5 times while maintaining a certain degree of saturation. The sequence patterns P3, P4, and P5 are all about 1.5 times as bright as the sequence pattern P1, and there is no significant difference in color gamut. It may be used as a sequence pattern including Y and C that compensates for the G light that is likely to be insufficient with the light emission amount of the LED.

Compared to the sequence pattern P1, the other sequence patterns P2 to P5 compensate for insufficient brightness at the expense of the color gamut. When displaying an image that does not require vivid colors such as R, G, and B pure colors. There is an advantage that a bright display can be performed.
Conversely, by suppressing vivid colors by image processing and displaying them with the sequence pattern P2, it is possible to display the image sufficiently brighter than the sequence pattern P1.

  Note that the sequence pattern is not limited to P1 to P5, and may be expressed by a current value instead of being expressed by the color order and the ratio of the subsequence time. Further, instead of expressing with a time ratio, it may be set by information specifying a time width.

1 is an overall configuration diagram showing a color image display device according to an embodiment of the present invention. It is a figure which shows an example of the sequence pattern of the color image display apparatus of FIG. FIG. 10 is a diagram showing a first modification of the sequence pattern in FIG. 2. It is a figure which shows the 2nd modification of the sequence pattern of FIG. It is a figure which shows the 3rd modification of the sequence pattern of FIG. It is a whole block diagram which shows the other Example of a color image display apparatus. It is a figure which shows the example of the sequence pattern of the color image display apparatus of FIG.

Explanation of symbols

Fr, Fg, Fb Subframe time Gr, Gg. Gb Data gain 1 Color image display device 2, 3, 4 Light source 7 Liquid crystal element (light modulation unit)
9 Subframe control unit 10 Image signal analysis unit 11 Scaling unit 12 Lighting control unit

Claims (5)

A plurality of light sources that emit light of different colors;
A light modulator for modulating light from the plurality of light sources;
A subframe control unit that controls the light source and the light modulation unit by allocating a subframe time to each subframe image data according to the size of the input subframe image data of different colors.
The color image display device, wherein the subframe control unit shortens a subframe time allocated to each subframe image data as the subframe image data becomes smaller.   The sub-frame control unit analyzes gradation values of a plurality of pixels in the sub-frame image data for each color, multiplies the data gain to the sub-frame image data of each color, and outputs to the light modulation unit; The color image display apparatus according to claim 1, further comprising: a lighting control unit that controls the light source to light according to a subframe time.   The image signal analysis unit detects a maximum value of gradation values of a plurality of pixels in the subframe image data for each color, outputs a subframe time corresponding to the detected maximum value for each color, and is input The color image display device according to claim 2, wherein a value obtained by dividing the upper limit value of the subframe image data by the detected maximum value for each color is output as the data gain. The frame time, which is one cycle time for displaying the sub-frame image data of all the different colors, is constant,
4. The color image display device according to claim 2, wherein a non-display time during which the light source is not turned on is provided when a total of subframe times output from the image signal analysis unit is shorter than a frame time.   The color image display device according to claim 4, wherein display of all subframe images is repeated when a total of subframe times output from the image signal analysis unit is shorter than half of the frame time.

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