JP2008216560A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of obtaining ample power consumption reduction effect, even when an image signal includes a small number of pixel signals of saturation gradations. <P>SOLUTION: In the display device, an image feature quantity extracting unit 22 generates histograms of the luminance level distributions of respective pixels included in the image signal by light emission colors, and finds the threshold levels that reach a previously set pixel number ratio by the light emission colors from pixels, having the lowest or the highest luminance level in the histograms by the light emission colors, and a CPU 18 calculates light source control values and image correction values by the light emission colors based on the threshold levels. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly, to a display device including a light source that emits light of a plurality of different colors.

  In recent years, projectors and the like using LEDs that emit red (R), green (G), and blue (B) light as light sources have been developed due to high output and high efficiency of light emitting diodes (LEDs). In such a display device using a plurality of LEDs of different colors, it is possible to easily and instantaneously change the light amount of the light source by increasing or decreasing the current level applied to the LEDs.

For this reason, in a conventional liquid crystal display device using a plurality of LEDs of different colors as a light source, display information (image signal) on the screen is separated into color information, and the illumination intensity from the light source according to the maximum value of the color information of each color In addition, the transmittance of the liquid crystal panel is increased according to both the illumination intensity and the display information, and the power consumption is reduced while maintaining the brightness of the display image (for example, see Patent Document 1).
Japanese Patent Laying-Open No. 2005-49362 (first page, FIGS. 1 and 2)

  In the above liquid crystal display device (for example, see Patent Document 1), when the maximum value for each RGB of the display information of the image does not reach the saturation gradation (for example, 255 for 8-bit data), the light source amount of each color Is reduced to (maximum value of color information of each color / saturation gradation), and the transmittance of the liquid crystal panel is increased by the reciprocal thereof, thereby reducing the power consumption while maintaining the brightness of the display image. Yes. However, in such a liquid crystal display device, there is a problem in that if there is even a small amount of saturation gradation pixel information in the display information, the amount of light source cannot be reduced, and a sufficient power consumption reduction effect cannot be obtained. .

  The present invention has been made in view of the above problems, and provides a display device that can obtain a sufficient power consumption reduction effect even when there are a small number of saturated gradation pixel signals in an image signal. The purpose is to provide.

  The display device according to the present invention emits light of a plurality of different colors and can adjust the light emission amount for each light emission color, and the light source for controlling the light emission amount of the light emitted by the light source device for each light emission color. Based on the control means, an image processing means for inputting an image signal including a luminance level for each emission color corresponding to each pixel to be displayed, performing predetermined processing on the image signal to generate image data, and the image data The image modulation means for spatially modulating the light emitted from the light source means for each emission color, the image feature quantity extraction means for inputting the image signal and extracting the feature quantity of the image signal, and the image feature quantity extraction means Based on the feature amount of the image signal, a light source control value for changing the light emission amount of the light source means is calculated and supplied to the light source control means, and an image correction value for correcting the image data is calculated and supplied to the image processing means. Arithmetic processing means to be supplied; And an image feature amount extraction unit creates a luminance level distribution histogram for each luminescent color for each pixel included in the image signal, and presets from the pixel with the lowest or highest luminance level in the histogram for each luminescent color. A threshold level corresponding to the ratio of the number of pixels is obtained for each emission color, and the arithmetic processing means calculates a light source control value and an image correction value for each emission color based on the threshold level.

  In the display device according to the present invention, the image feature amount extraction unit and the calculation processing unit obtain a threshold level having the largest value among the threshold levels obtained for each emission color as the clip level, and obtain the largest value. For pixels whose threshold level is the reference clip color and the reference clip color has a brightness level equal to or higher than the clip level, the reference clip color brightness level is set to the clip level, and the brightness level of the emission color other than the reference clip color is set. Multiply the clip level and divide by the luminance level of the reference clip color of that pixel. From the luminance level of the processed pixel and the luminance level of the pixel whose reference clip color luminance level is less than the clip level, for each emission color The maximum clip value is obtained, and the arithmetic processing means calculates the light source control value based on the maximum clip value to obtain the light The amount of light emitted by the means is adjusted, and for each pixel included in the image signal, it is determined whether the luminance level of the reference clip color is equal to or higher than the clip level, and the luminance level of the reference clip color is equal to or higher than the clip level. And different image correction values are calculated for pixels whose luminance level of the reference clip color is lower than the clip level.

  In the display device according to the present invention, the arithmetic processing unit calculates a light source control value so that a light emission amount of light emitted from the light source unit for each emission color is proportional to a maximum clip value. It is what.

  Further, in the display device according to the present invention, the arithmetic processing unit performs image processing on a pixel whose luminance level of the reference clip color is less than the clip level as a value inversely proportional to the light emission amount of the light emitted from the light source unit for each emission color. Calculate a correction value, and for a pixel whose luminance level of the reference clip color is equal to or higher than the clip level, multiply the value that is inversely proportional to the amount of light emitted by the light source means for each emission color by multiplying the clip level by the reference clip color of that pixel The image correction value is calculated as a value divided by the brightness level, and the image processing means multiplies the image data by the calculated image correction value to perform correction.

  In the display device according to the present invention, the image feature amount extraction unit or the calculation processing unit sets the threshold level obtained for each emission color as the clip level of each emission color, and the calculation processing unit controls the light source based on the clip level. The value is calculated, the light emission amount of the light emitted by the light source means is adjusted, and for each pixel included in the image signal, it is determined whether or not at least one of the luminance levels for each emission color is equal to or higher than the clip level. It is characterized in that different image correction values are calculated for pixels in which at least one of the luminance levels for each color is higher than or equal to the clip level and for pixels whose luminance levels for each emission color are all lower than the clip level.

  Further, the display device according to the present invention is characterized in that the arithmetic processing means calculates a light source control value so that a light emission amount of light emitted from the light source means for each emission color is an amount proportional to a clip level. To do.

  Further, in the display device according to the present invention, the arithmetic processing unit determines that the pixel whose luminance level for each emission color is less than the clip level is inversely proportional to the amount of light emitted by the light source unit for each emission color. The image correction value is calculated, and for the pixels where at least one of the luminance levels for each emission color is equal to or higher than the clip level, in the orthogonal graph in which each axis represents the luminance level for each emission color, the plane passing through the origin and orthogonal to each axis Light that the light source means emits for each emission color by defining a rectangular parallelepiped with a plane perpendicular to each axis by the clip level value of each emission color and obtaining the intersection of the straight line connecting the origin and the coordinates of that pixel and the rectangular parallelepiped The image correction value is calculated as a value obtained by multiplying the value inversely proportional to the light emission amount by the distance from the intersection to the origin and dividing the value by the distance from the coordinates of the pixel to the origin, and the image processing means calculates the calculated image correction value. It is characterized in adding a correction by multiplying the image data.

  The display device according to the present invention emits red, green, and blue light, and can adjust the light emission amount for each emission color, and controls the light emission amount of the light emitted by the light source unit for each emission color. A light source control means, an image signal including a luminance level for each emission color corresponding to each pixel to be displayed, an image processing means for performing a predetermined process on the image signal to generate image data, and image data The image modulation means for spatially modulating the light emitted from the light source means for each emission color, the image feature quantity extraction means for inputting the image signal and extracting the feature quantity of the image signal, and the image feature quantity extraction means Calculates a light source control value for changing the light emission amount of the light source means based on the feature quantity of the image signal extracted by the image signal, supplies the light source control value to the light source control means, calculates an image correction value for correcting the image data, and calculates the image processing means. Arithmetic processing means for supplying to The image feature amount extraction unit or the arithmetic processing unit calculates the Y luminance level by performing YUV conversion on the luminance level of each pixel included in the image signal, creates a histogram of the Y luminance level distribution, and generates the Y luminance level. In the histogram of the distribution, a threshold level that is a ratio of the number of pixels set in advance is obtained from the pixel with the lowest or highest Y luminance level, and the Y luminance level of each pixel is processed based on this threshold level and then the inverse YUV By performing the conversion, the corrected luminance data of red, green, and blue is calculated for each pixel, and the clip maximum value that is the maximum value for each emission color is obtained from the corrected luminance data. The light source control value and the image correction value are calculated for each emission color based on the maximum clip value.

  In the display device according to the present invention, the image feature amount extraction unit or the arithmetic processing unit performs a process of setting a Y luminance level of a pixel to a threshold level for a pixel having a Y luminance level equal to or higher than the threshold level. The corrected luminance data is calculated using the Y luminance level subjected to the above, the Y luminance level of the pixel whose Y luminance level is less than the threshold level, and the U and V values of each pixel obtained by YUV conversion. To do.

  In the display device according to the present invention, the arithmetic processing unit calculates a light source control value so that a light emission amount of light emitted from the light source unit for each emission color is proportional to a maximum clip value. It is what.

  In the display device according to the present invention, the arithmetic processing unit calculates the image correction value as a value inversely proportional to the light emission amount of the light emitted from the light source unit for each emission color, and the image processing unit calculates the calculated image. The correction is performed by multiplying the image data by the correction value.

  In the display device according to the present invention, the image feature amount extraction unit creates a histogram of the luminance level distribution for each pixel included in the image signal for each emission color, and the lowest or highest luminance in the histogram for each emission color. A threshold level that is a ratio of the number of pixels set in advance from the level is obtained for each emission color, and the arithmetic processing unit calculates the light source control value and the image correction value for each emission color based on the threshold level. By reducing the light source control value and reducing the light emission amount of the light source means for each emission color, and increasing the image data by the image correction value by the amount of this light emission amount, the pixel of saturation gradation in the image signal Even when there are a small number of signals, it is possible to obtain a sufficient power consumption reduction effect while maintaining the brightness of the display image.

(Embodiment 1)
The display device according to Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an overall configuration of a display device according to Embodiment 1 of the present invention. Although FIG. 1 shows a three-plate liquid crystal panel type image projection apparatus (projector) as an example of the display apparatus, the present invention may be applied to other display apparatuses such as a liquid crystal display. Further, the present invention is not limited to the three-panel liquid crystal panel method, and may be applied to a single-plate color plane sequential image projection apparatus using a DMD (Digital Mirror Device).

  The image projection apparatus shown as an example of the display device in FIG. 1 includes an image processing unit 10, and the image processing unit 10 includes an R image processing unit 10r, a G image processing unit 10g, and a B image processing unit 10b. An R image signal, a G image signal, and a B image signal are input to the R image processing unit 10r, the G image processing unit 10g, and the B image processing unit 10b, respectively, and predetermined processing is performed for each color to generate image data. Is done. The R image signal, the G image signal, and the B image signal are analog RGB signals from a personal computer or the like, or image signals from a television (NTSC), etc., and the luminance level for each RGB corresponding to each pixel displayed by the image projection device. Is included.

  Each image signal input to the image processing unit 10 is subjected to processing such as synchronization separation, Y / C separation, IP conversion, scaling (resolution conversion), color (color matrix) conversion, and keystone correction. It is desirable that The generated image data for each color is corrected by an image correction value supplied from the CPU 18 to the image processing unit 10 as shown below, and then the R image modulation unit 12r and the G image modulation of the image modulation unit 12, respectively. The image is sent to the unit 12g and the B image modulation unit 12b, and an image for each RGB is formed in the image modulation unit of each color. In the present embodiment, it is assumed that each of the R image modulation unit 12r, the G image modulation unit 12g, and the B image modulation unit 12b includes a liquid crystal panel.

  1 includes a light source 14 that emits red (R), green (G), and blue (B) light corresponding to an R image signal, a G image signal, and a B image signal. The light source 14 includes an R light source 14r that emits R light, a G light source 14g that emits G light, and a B light source 14b that emits B light. The light sources of each color are, for example, light emitting diodes (hereinafter referred to as LEDs). It is composed of In this embodiment, the R light source 14r, the G light source 14g, and the B light source 14b are each configured by one LED. However, for example, two or more LEDs may be used for each RGB. The number of LEDs may be different for each. Further, as the light source 14, an organic electroluminescence element (organic EL element) that emits a plurality of different colors may be used instead of the LED.

  The R light source 14r, the G light source 14g, and the B light source 14b of the light source 14 are respectively connected to the R light source control unit 16r, the G light source control unit 16g, and the B light source control unit 16b of the light source control unit 16, and the R light source control unit 16r. The G light source control unit 16 g and the B light source control unit 16 b are connected to the CPU 18. The CPU 18 supplies the R light source control value to the R light source control unit 16r, the G light source control value to the G light source control unit 16g, and the B light source control value to the B light source control unit 16b. The unit 16r, the G light source control unit 16g, and the B light source control unit 16b adjust the light emission amounts of the R light source 14r, the G light source 14g, and the B light source 14b based on the light source control values of the respective colors. At this time, for example, the R light source control unit 16r, the G light source control unit 16g, and the B light source control unit 16b control the current values of the currents supplied to the R light source 14r, the G light source 14g, and the B light source 14b to emit light for each RGB. To change. As shown below, the CPU 18 calculates an R light source control value, a G light source control value, and a B light source control value based on the threshold level obtained by the image feature amount extraction unit 22.

  The CPU 18 is connected to the R image processing unit 10r, the G image processing unit 10g, and the B image processing unit 10b of the image processing unit 10, and outputs the R image correction value to the R image processing unit 10r and the G image processing unit. The G image correction value is supplied to 10 g and the B image correction value is supplied to the B image processing unit 10 b. The R image correction value, the G image correction value, and the B image correction value are input to the image processing unit 10. Correction is added by multiplying the value of the image data of each color. As shown below, the CPU 18 calculates the R image correction value, the G image correction value, and the B image correction value based on the threshold level obtained by the image feature amount extraction unit 22.

  Light from the R light source 14r, the G light source 14g, and the B light source 14b is guided to the R image modulation unit 12r, the G image modulation unit 12g, and the B image modulation unit 12b of the image modulation unit 12, respectively, and is output by the image modulation unit of each color. Spatial modulation. The image for each RGB generated in this way is guided to the image composition unit 20 composed of a dichroic prism or the like, and the image composition unit 20 synthesizes each color image generated by the image modulation unit 12 into an RGB mixed color image, This image is projected as a display image on a screen (not shown) or the like outside the image projection apparatus.

  Further, an image feature quantity extraction unit 22 and a pixel number ratio setting unit 24 are connected to the CPU 18, and an R image signal, a G image signal, and a B image signal are input to the image feature quantity extraction unit 22. The image feature quantity extraction unit 22 extracts the feature quantity of the image signal of each color for each frame and sends it to the CPU 18. The pixel number ratio setting unit 24 receives, for example, the following pixel number ratios from the user, and the pixel number ratio setting unit 24 sets the pixel number ratio in the CPU 18. The CPU 18 sends the set pixel number ratio to the image feature quantity extraction unit 22, and the image feature quantity extraction unit 22 obtains the following threshold level based on this pixel number ratio and feeds it back to the CPU 18.

  In the image projection apparatus shown in FIG. 1, the pixel number ratio setting unit 24 is provided in the CPU 18 or the image feature amount extraction unit 22, and the pixel number ratio is automatically set according to the average luminance level (APL) of the image signal. You may make it set to. Further, the image feature quantity extraction unit 22 may be provided inside the CPU 18 or the image feature quantity extraction unit 22 may have the function of the CPU 18. Further, in order to synchronize the delay time of the light emission amount change of the light source 14 and the spatial modulation by the image modulation unit 12, the image processing unit 10 may be provided with image delay means such as a memory. Further, a predetermined limit may be provided for the ratio of the number of pixels.

  In the present embodiment, the image feature amount extraction unit 22 creates a luminance level distribution histogram for each of the luminance levels of each pixel included in the image signal for each RGB, and the lowest or highest luminance level in the histogram for each RGB. A threshold level corresponding to a preset number of pixels is determined for each RGB from the pixels, and the CPU 18 calculates a light source control value and an image correction value for each RGB based on this threshold level. As a result, the amount of light emitted from the light source of each color of the light source 14 decreases, and the value of the corrected image data sent to the image modulation unit of each color of the image modulation unit 12 increases. In the case of this embodiment, the R image modulation unit 12r, the G image modulation unit 12g, and the B image modulation unit 12b configured by a liquid crystal panel are proportional to the value of the corrected image data sent to the image modulation unit of each color. Light transmittance increases. For this reason, it is possible to reduce power consumption while maintaining the brightness of the display image.

  FIG. 2 is a flowchart illustrating a procedure in which the image feature amount extraction unit 22 and the CPU 18 calculate the light source control value and the image correction value to control the light source 14 and the image modulation unit 12 in the present embodiment. FIG. 3 is a graph showing an example of a luminance level distribution histogram created by the image feature quantity extraction unit 22, FIG. 3 (a) shows a histogram for an R image signal, and FIG. 3 (b) shows a G image. FIG. 3C shows a histogram for the B image signal. Hereinafter, the control method of the display device according to the present embodiment will be described by taking as an example a case where an image signal having a histogram shown in FIG. 3 is input.

  First, for example, the pixel number ratio setting unit 24 sets the pixel number ratio input by the user in the CPU 18 (S101). This pixel number ratio is set in the form of a predetermined number of pixels counted from the lowest luminance level pixel or the highest luminance level pixel in the histogram shown in FIG. In the example of FIG. 3, it is assumed that a pixel number ratio of 99% is set from the pixel having the lowest luminance level. Note that the ratio of the number of pixels may be set in a form such as 5% from the pixel having the highest luminance level.

  Then, the image feature quantity extraction unit 22 creates a histogram of luminance level distribution as shown in FIG. 3 for each pixel included in the image signal for each RGB (S102). The luminance level distribution histogram shown in FIG. 3 is obtained by extracting pixels for one frame of an image, and each RGB image signal is 8-bit data (256 gradations, luminance levels 0 to 255). The histogram of the luminance level distribution shown in FIG. 3 is for a dark image as a whole with few pixels on the high luminance side.

  Then, the image feature quantity extraction unit 22 obtains, for each RGB, a threshold level that is the ratio of the number of pixels preset in S101 in the histogram of the luminance level distribution for each RGB as shown in FIG. 3 (S103). Here, a pixel number ratio of 99% is set from the pixel of the lowest luminance level, and the luminance level that is the pixel number ratio is the threshold level. In the example of FIG. 3, it is assumed that the threshold level for the R image signal is 200, the threshold level for the G image signal is 223, and the threshold level for the B image signal is 190. This means that, for example, in the R image signal of FIG. 3 (a), pixels with an R luminance level of 0 to 200 occupy 99% of all pixels.

  Next, the image feature quantity extraction unit 22 or the CPU 18 obtains the largest threshold level among the RGB threshold levels obtained in S103 as the clip level, and determines the color having the largest threshold level as the reference clip color. (S104). In the example of FIG. 3, the threshold level for the R image signal is 200, the threshold level for the G image signal is 223, and the threshold level for the B image signal is 190 as described above. The level is 223.

  Then, the image feature quantity extraction unit 22 or the CPU 18 sets the luminance level of the reference clip color as the clip level for pixels whose luminance level of the reference clip color is equal to or higher than the clip level, and sets the luminance level of the color other than the reference clip color ( A process of multiplying a coefficient of clip level / luminance level of the reference clip color of the pixel is performed (S105).

  FIG. 4 is a graph showing the luminance level of each pixel included in the image signal as coordinates. In FIG. 4, the luminance level of G is plotted on the horizontal axis (g) and the luminance level of R is plotted on the vertical axis (r), and as an example, two pixels ▲ and ■ where the luminance level of the reference clip color is equal to or higher than the clipping level are shown. ing. The pixel ▲ is assumed to have an R luminance level of 231 and a G luminance level of 240, and is hereinafter expressed as ▲ (R231, G240). Further, it is assumed that (2) (R159, G247). In FIG. 4, the R threshold level (r = 200) and the G threshold level (g = 223) are indicated by dotted lines, and the G threshold level (x = 223) is the clip level.

  By performing the process of S105, the pixel ▲ (R231, G240) moves to Δ (R215, G223), which is the intersection of the straight line connecting the origin of the dotted line x = 223 and the pixel ▲, and the pixel ■ (R159, G247). ) Moves to □ (R144, G223) which is the intersection of the dotted line of x = 223 and the straight line connecting the pixel ■ and the origin. Here, the values of R for Δ and □ are obtained from the calculation of (231 × (223/240)) = 215 and (159 × (223/247)) = 144 using the above formula. The same processing is performed for the luminance level of B. Hereinafter, such a process is referred to as a one-side clip process.

  Then, the maximum clip value, which is the maximum value for each RGB, is obtained from the luminance level that has been subjected to the one-plane clipping process of S105 and the luminance level of the pixel for which the luminance level of the reference clip color is less than the clip level (S106). Note that the one-plane clipping process of S105 is not performed for pixels whose luminance level of the reference clip color is less than the clip level. In the example of FIG. 3, it is assumed that the R clip maximum value is 215, the G clip maximum value is 223, and the B clip maximum value is 195. Here, the maximum clip value of the reference clip color (here, G) is necessarily the same value (223) as the clip level by performing the process of S105. In FIG. 3, the maximum R clip value r = 215 (R value of Δ) is indicated by a dotted line.

  Then, the CPU 18 calculates a light source control value for each RGB based on the maximum clip value obtained in S106, and adjusts the amount of light emitted from the light source 14 (S107). At this time, the CPU 18 calculates the light source control value so that the light emission amount of the light emitted from the light source 14 for each RGB is proportional to the maximum clip value. In this embodiment, the maximum light emission amount of the light source of each color is set to 1, and the light source control value at which the light emission amount for each RGB is (clip maximum value / 255) is obtained. For example, in the example of FIG. 3, since the R clip maximum value is 215, the G clip maximum value is 223, and the B clip maximum value is 195, the light emission amount of the R light source 14r is (215/255) and the G light source 14g. Is set to (223/255), and the B light source 14b is set to (195/255).

  FIG. 5 is a graph showing the light emission amount of each color adjusted by the light source control value. FIG. 5 shows a case where an image signal having the histogram shown in FIG. 3 is input, and shows only the G light source 14g and the R light source 14r.

  As shown in FIG. 5, the light emission amount of G can be reduced to 87.5% (223/255) compared to the maximum light emission amount (100%) of the G light source 14g, and the light emission amount of R can be reduced to the R light source 14r. Can be reduced to 84.3% (215/255) compared to the maximum light emission amount (100%). Note that the amount of light emission of B is similarly reduced.

  Then, the CPU 18 determines whether or not the luminance level of the reference clip color is equal to or higher than the clip level for each pixel included in the image signal, and the luminance level of the reference clip color and the pixel whose luminance level of the reference clip color is equal to or higher than the clip level is clipped. A different image correction value is calculated for each of RGB for pixels less than the level (S108).

  At this time, the CPU 18 calculates an image correction value for each RGB as a value that is inversely proportional to the light emission amount of the light source 14 adjusted in S107 for pixels whose luminance level of the reference clip color is less than the clip level. In the present embodiment, the RGB image correction value is the reciprocal of the light emission amount of the light source. For example, in the example of FIG. 3, the R light emission amount is (215/255), the G light emission amount is (223/255), and the B light emission amount is (195/255). Therefore, the R image correction value is (255). / 215), the G image correction value is (255/223), and the B image correction value is (255/195).

  For a pixel whose luminance level of the reference clip color is equal to or higher than the clip level, a value of (clip level / brightness level of the reference clip color of the pixel) is multiplied by a value inversely proportional to the light emission amount of the light source 14 adjusted in S107. The image correction value is calculated for each RGB as the obtained value. In this embodiment, the image correction value for each RGB is a value obtained by multiplying the reciprocal of the light emission amount of the light source by (clip level / brightness level of the reference clip color of the pixel). For example, in the example of FIG. 3, the luminance level of the reference clip color of the pixel in the image signal is Gin, the R image correction value is ((255/215) × (223 / Gin)), and the G image correction value is ((255 / 223) × (223 / Gin)) and the B image correction value is ((255/195) × (223 / Gin)). At this time, the image data after the correction of the reference clip color is Gin × ((255/223) × (223 / Gin)) = 255 (maximum gradation).

  The image correction value of each color is multiplied by the image data of each color generated by the image processing unit 10 to correct the image data. In this embodiment, the image modulation unit for each color has a light transmittance proportional to the corrected image data. Therefore, for pixels whose luminance level of the reference clip color is less than the clip level, the image correction value is set for each RGB of the light source 14. By setting the reciprocal of the light emission amount, the luminance and color balance in the display image are maintained even if the light emission amount of the light source 14 changes for each RGB. In addition, in pixels whose luminance level of the reference clip color is equal to or higher than the clip level, the light emission amount of the light source 14 changes for each RGB by providing the image correction value of each color with a factor of the reciprocal of the light emission amount for each RGB of the light source 14. Even in this case, the color balance in the display image is maintained. In addition, if the luminance level of the reference clip color is equal to or higher than the clip level, the image data after correction of the reference clip color is set to the maximum gradation because the coefficient of (clip level / brightness level of the reference clip color of the pixel) is multiplied. Therefore, even if the light emission amount of the light source 14 is reduced, a reduction in luminance in the display image can be minimized.

  In the present embodiment, the image feature amount extraction unit 22 creates a histogram of luminance level distribution for each of the pixels included in the image signal for each RGB, and presets the lowest or highest luminance level in the histogram for each RGB. Since the threshold level corresponding to the ratio of the number of pixels is obtained for each RGB and the CPU 18 calculates the light source control value and the image correction value for each RGB based on the threshold level, the light source control value is reduced according to the threshold level and the light source Can be reduced for each emission color, and the image data can be increased by the image correction value corresponding to the reduction in the emission amount. As a result, even when there are a small number of saturated gradation pixel signals in the image signal, it is possible to obtain a sufficient power consumption reduction effect while maintaining the brightness of the display image.

(Embodiment 2)
FIG. 6 is a flowchart illustrating a procedure in which the image feature amount extraction unit 22 and the CPU 18 calculate the light source control value and the image correction value to control the light source 14 and the image modulation unit 12 in the display device according to the second embodiment. The configuration of the display device according to the present embodiment is the same as that of the image projection device shown in FIG. 1 of the first embodiment, and the same components are denoted by the same reference numerals for description. FIG. 7 is a graph showing an example of a histogram of luminance level distribution created by the image feature quantity extraction unit 22, FIG. 7A shows a histogram for an R image signal, and FIG. 7B shows a G image. FIG. 7C shows a histogram for the B image signal. Hereinafter, the control method of the display device according to the present embodiment will be described by taking as an example a case where an image signal having a histogram shown in FIG. 7 is input.

  First, as in the first embodiment, the pixel number ratio setting unit 24 sets the pixel number ratio in the CPU 18 (S201). In the example of FIG. 7, it is assumed that a pixel number ratio of 95% is set from the pixel having the lowest luminance level.

  Then, as in the first embodiment, the image feature quantity extraction unit 22 creates a luminance level distribution histogram for each of RGB as shown in FIG. 7 for each pixel included in the image signal (S202). The luminance level distribution histogram shown in FIG. 7 is obtained by extracting pixels for one frame of the image as in the first embodiment, and each RGB image signal is 8-bit data (256 gradations, luminance levels 0 to 255). Suppose that The histogram of the luminance level distribution shown in FIG. 7 is also for an image signal of a dark image as a whole with few pixels on the high luminance side.

  Similarly to the first embodiment, the image feature amount extraction unit 22 obtains a threshold level for each RGB that is the ratio of the number of pixels set in advance in S201 in the histogram of the luminance level distribution for each RGB (S203). Here, a pixel number ratio of 95% is set from the pixel with the lowest luminance level, and the luminance level that is the pixel number ratio is the threshold level. In the example of FIG. 7, the threshold level for the R image signal is 179, the threshold level for the G image signal is 241, and the threshold level for the B image signal is 254.

  Next, the image feature quantity extraction unit 22 or the CPU 18 sets the threshold level for each RGB obtained in S203 as the clip level for each RGB (S204). In the example of FIG. 7, since the threshold level for the R image signal is 179, the threshold level for the G image signal is 241 and the threshold level for the B image signal is 254 as described above, the R clip level is 179, The G clip level is 241 and the B clip level is 254. Hereinafter, such processing is referred to as three-side clip processing.

  Then, the CPU 18 calculates a light source control value for each RGB based on the clip level, and adjusts the light emission amount of the light emitted from the light source 14 (S205). At this time, the CPU 18 calculates the light source control value so that the light emission amount of the light emitted from the light source 14 for each RGB is proportional to the clip level. In this embodiment, the maximum light emission amount of the light source of each color is set to 1, and the light source control value at which the light emission amount for each RGB is (clip level / 255) is obtained. For example, in the example of FIG. 7, since the R clip level is 179, the G clip level is 241, and the B clip level is 254, the light emission amount of the R light source 14r is (179/255) and the light emission amount of the G light source 14g. Is (241/255), and the light emission amount of the B light source 14b is (254/255).

  FIG. 8 is a graph showing the light emission amount of each color adjusted by the light source control value. FIG. 8 shows a case where an image signal having the histogram shown in FIG. 7 is input.

  As shown in FIG. 8, the light emission amount of R is 70.2% (179/255) compared to the maximum light emission amount (100%) of the R light source 14r, and the light emission amount of G is the maximum light emission amount of the G light source 14g ( The light emission amount of B is reduced to 99.6% (254/255) compared to the maximum light emission amount (100%) of the B light source 14b. it can.

  Then, the CPU 18 determines whether or not at least one of the luminance levels for each RGB included in the image signal is equal to or higher than the clip level, and at least one of the luminance levels for each RGB is equal to or higher than the clip level. Different image correction values are calculated for each of RGB for pixels whose luminance levels are all less than the clip level (S206).

  At this time, the CPU 18 calculates an image correction value for each RGB as a value that is inversely proportional to the light emission amount of the light source 14 adjusted in S105 for pixels whose luminance levels for each RGB are less than the clip level. In the present embodiment, the RGB image correction value is the reciprocal of the light emission amount of the light source. For example, in the example of FIG. 7, the R emission amount is (179/255), the G emission amount is (241/255), and the B emission amount is (254/255). Therefore, the R image correction value is (255). / 179), the G image correction value is (255/241), and the B image correction value is (255/254).

  In addition, for at least one of the luminance levels for each of the RGB, the image correction value for each RGB is calculated as follows for a pixel having a clip level or higher. First, in the orthogonal graph in which each axis represents the luminance level for each RGB, the plane (RG plane, GB plane, BR plane) passing through the origin and orthogonal to each axis (RG plane, GB plane, BR plane) and RGB clip levels A rectangular parallelepiped is defined by a plane orthogonal to each axis. FIG. 9 is a diagram illustrating a rectangular parallelepiped defined in an orthogonal graph in which each axis represents a luminance level for each RGB. In FIG. 9, the surface perpendicular to the R axis at the R clip level is the R clip surface, the surface perpendicular to the G axis at the G clip level is the G clip surface, and the surface perpendicular to the B axis at the B clip level is the B clip. It is a surface. In FIG. 9, the clip level shown in FIG. 7 is used.

Then, assuming that the luminance level for each of RGB of the target pixel is r, g, b, the coordinates P (r, g, b) are plotted on an orthogonal graph, and a straight line connecting the origin and P (r, g, b) The intersection P ′ (r ′, g ′, b ′) with the rectangular parallelepiped is obtained. For example, assuming that the intersection point P ′ (r ′, g ′, b ′) is on the G clip plane, r ′, g ′, b ′ are as follows.
r ′ = (r × (G clip level) / g)
g ′ = (G clip level)
b ′ = (b × (G clip level) / g)
Then, a distance d ′ from the intersection P ′ (r ′, g ′, b ′) to the origin and a distance d from the coordinates P (r, g, b) of the target pixel to the origin are obtained. The distances d ′ and d are given by the following equations.

  Note that the processing in the orthogonal graph is conceptual and can be numerically calculated by the CPU 18.

  Then, an image correction value is calculated for each RGB as a value obtained by multiplying a value inversely proportional to the light emission amount of the light source 14 adjusted in S205 by a coefficient of (distance d ′ / distance d). In the present embodiment, the RGB image correction value is a value obtained by multiplying the reciprocal of the light emission amount of the light source by (distance d ′ / distance d). The (distance d ′ / distance d) can also be obtained from the ratio of the intersection point P ′ (r ′, g ′, b ′) and the coordinates P (r, g, b) of the target pixel for each RGB. For example, in the example of FIG. 7, the R image correction value is ((255/179) × (d ′ / d)), the G image correction value is ((255/241) × (d ′ / d)), and the B image correction is performed. The value is ((255/254) × (d ′ / d)). At this time, for example, if the intersection point P ′ (r ′, g ′, b ′) is on the G clip plane, the image data for G after correction is 255 (maximum gradation).

  The image correction value of each color is multiplied by the image data of each color generated by the image processing unit 10 to correct the image data. In the present embodiment, the light emission amount of the light source 14 changes for each RGB by setting the image correction value to the reciprocal of the light emission amount for each RGB of the light source 14 for pixels whose luminance levels for each RGB are less than the clip level. Also, the brightness and color balance in the display image are maintained. In addition, in a pixel in which at least one of the luminance levels for each RGB is the clip level or higher, the light emission amount of the light source 14 is set for each RGB by providing the image correction value for each color with a factor of the reciprocal of the light emission amount for each RGB of the light source 14. The color balance in the display image is maintained even when the display changes. Furthermore, since at least one of the luminance levels for each of RGB is multiplied by a coefficient of (distance d ′ / distance d) in a pixel at or above the clip level, the corrected image data for one color can be set to the maximum gradation, Even if the light emission amount of the light source 14 decreases, a decrease in luminance in the display image can be minimized.

  Other effects are the same as those of the display device according to the first embodiment.

(Embodiment 3)
FIG. 10 is a flowchart illustrating a procedure in which the image feature amount extraction unit 22 and the CPU 18 calculate the light source control value and the image correction value to control the light source 14 and the image modulation unit 12 in the display device according to the third embodiment. The configuration of the display device according to the present embodiment is the same as that of the image projection device shown in FIG. 1 of the first embodiment, and the same components are denoted by the same reference numerals for description.

  In this embodiment, the Y luminance level is obtained by performing YUV conversion on the image signal for each RGB, and the corrected luminance data for each RGB is obtained by inverse YUV conversion after performing predetermined processing on this Y luminance level. For example, when the control using the three-surface clip processing of the second embodiment is performed on a sunset scene, the brightness of the sunset (high luminance part) and the sky (low luminance part) may be reversed. However, in the control using the Y clip processing described in the present embodiment, such a luminance reversal phenomenon can be prevented.

  First, the pixel number ratio setting unit 24 sets the ratio of the number of pixels for the Y luminance level in the CPU 18 (S301). The ratio of the number of pixels for the Y luminance level is set in the form of a predetermined number of pixels counted from the pixel with the lowest Y luminance level or the pixel with the highest Y luminance level.

Then, the image feature amount extraction unit 22 or the CPU 18 performs YUV conversion on the luminance level for each of the RGB included in the image signal to calculate the Y luminance level of each pixel (S302). The Y luminance level (y), the U level (u), and the V level (v) are expressed by the following linear conversion, where R luminance level is r, G luminance level is g, and B luminance level is b. Desired.
y = 0.299r + 0.587g + 0.114b
u = −0.169r−0.331 g + 0.500b
v = 0.500r-0.419g-0.081b
Then, the image feature amount extraction unit 22 creates a histogram of Y luminance level distribution for each pixel included in the image signal (S303). At this time, similarly to the first embodiment, pixels for one frame of the image are extracted to create a histogram of Y luminance distribution.

  Then, the image feature amount extraction unit 22 obtains a threshold level for the Y luminance level which is the ratio of the number of pixels set in advance in S301 in the histogram of Y luminance level distribution (S304). The method for obtaining the threshold level for the Y luminance level is the same as the method for obtaining the threshold level for the RGB image signals in the first and second embodiments.

  Next, the image feature amount extraction unit 22 or the CPU 18 sets the threshold level for the Y luminance level obtained in S304 as the clip level, and sets the Y luminance level of the pixel with the Y luminance level equal to or higher than the threshold level as the threshold level. (S305). Hereinafter, such processing is referred to as Y-clip processing.

Then, the image feature amount extraction unit 22 or the CPU 18 performs the Y luminance level that has been subjected to the Y clipping process in S305, the Y luminance level of the pixel whose Y luminance level is less than the threshold level, and the U and V obtained in the YUV conversion in S302. Inverse YUV conversion is performed using the values, and corrected luminance data for each RGB is calculated for each pixel (S306). Note that in the inverse YUV conversion in S306, the Y luminance level and the U and V values of the pixels whose Y luminance level is less than the threshold level are the same as those obtained in the YUV conversion in S302. The inverse YUV conversion is an inverse conversion of the above YUV conversion and is expressed as follows.
r = 1.000y + 0.000u + 1.402v
g = 1.000y + 0.344u-0.714v
b = 1.000y-1.772u + 0.000v
Then, the image feature amount extraction unit 22 or the CPU 18 obtains the maximum clip value that is the maximum value for each RGB from the corrected luminance data (S307).

  Then, the CPU 18 calculates a light source control value for each RGB based on the clip maximum value, and adjusts the light emission amount of light emitted from the light source 14 (S308). At this time, as in the first embodiment, the CPU 18 calculates the light source control value so that the amount of light emitted from the light source 14 for each RGB is proportional to the maximum clip value. In this embodiment, the maximum light emission amount of the light source of each color is set to 1, and the light source control value at which the light emission amount for each RGB is (clip maximum value / 255) is obtained.

  Then, the CPU 18 calculates an image correction value for each RGB (S309). At this time, the CPU 18 calculates an image correction value for each RGB as a value inversely proportional to the light emission amount of the light source 14 adjusted in S308 for all pixels. In the present embodiment, the RGB image correction value is the reciprocal of the light emission amount of the light source. That is, the image correction value for each RGB is (255 / maximum clip value).

  In the present embodiment, it is possible to prevent image degradation such as a luminance reversal phenomenon from occurring by performing clip processing at the Y luminance level.

  Other effects are almost the same as those of the display device according to the first embodiment.

(Embodiment 4)
For the control using the one-side clip processing shown in the first embodiment, the control using the three-side clip processing shown in the second embodiment, and the control using the Y clip processing shown in the third embodiment, There are advantages and disadvantages in terms of power consumption reduction effect. For this reason, if the control is fixed to use one clip process, the image quality may be deteriorated depending on the scene of the image, or a sufficient power consumption reduction effect may not be obtained.

  For this reason, in this embodiment, a display device that automatically determines control using optimal clip processing from the feature amount of an input image signal will be described. The configuration of the display device according to the present embodiment is the same as that of the image projection device shown in FIG. 1 of the first embodiment, and the same components are denoted by the same reference numerals for description.

  In this embodiment, as in the first embodiment, the image feature amount extraction unit 22 creates a histogram of luminance level distribution for each RGB, and obtains a threshold level for each RGB from a preset ratio of the number of pixels. Further, the image feature amount extraction unit 22 calculates the Y luminance level and creates a histogram of the Y luminance level distribution in the same manner as in the third embodiment, and obtains a threshold level for the Y luminance level from a preset ratio of the number of pixels. Further, the image feature amount extraction unit 22 analyzes the image signal by obtaining feature amounts such as the average brightness level, mode value (mode), and variance value of the brightness level distribution histogram and the Y brightness level distribution histogram for each RGB. .

  FIG. 11 is a diagram illustrating a luminance level distribution histogram and a Y luminance level distribution histogram for each RGB generated by the image feature amount extraction unit 22 for an image. 11A is a histogram for an R image signal, FIG. 11B is a histogram for a G image signal, FIG. 11C is a histogram for a B image signal, and FIG. 11D is a Y luminance level. It is a histogram about. In addition, FIG. 11 is obtained by extracting pixels for one frame of the image, and each RGB image signal is 8-bit data (256 gradations, luminance levels 0 to 255). Further, in FIG. 11, it is assumed that the ratio of the number of pixels in all the RGB and Y luminance levels is set to 99% from the pixel having the lowest luminance level, and the threshold level is shown in each histogram.

  In the example of FIG. 11, the histogram shape of the luminance level distribution for each RGB is greatly different, and the difference in threshold level for each RGB is relatively small. Further, the maximum luminance level is around 255 in all of RGB.

  When control using single-plane clipping processing is performed on the image having the histogram of FIG. 11, the light emission amount of the R light source 16r is 100% (255/255), and the light emission amount of the G light source 16g is 91.3% (233/255). ), The light emission amount of the B light source 16b is 83.9% (214/255), and the display image hardly changes.

  When the control using the three-surface clipping process is performed, the light emission amount of the R light source 16r is 75.7% (193/255), the light emission amount of the G light source 16g is 66.3% (169/255), and the B light source 16b. Is 83.9% (214/255), but the gray portion of the display image is discolored and image degradation occurs.

  When the control using the Y clip process is performed, the light emission amount of the R light source 16r is 99.6% (254/255), the light emission amount of the G light source 16g is 73.3% (187/255), and the B light source 16b The light emission amount is 94.1% (240/255), but the gray portion of the display image is discolored similarly to the control using the three-side clip processing, and image degradation occurs.

  For this reason, the CPU 18 determines that the control using the one-side clip process is optimal for an image having the characteristics as shown in FIG.

  FIG. 12 is a diagram showing a luminance level distribution histogram and a Y luminance level distribution histogram for each RGB created by the image feature amount extraction unit 22 for another image. 12A is a histogram for an R image signal, FIG. 12B is a histogram for a G image signal, FIG. 12C is a histogram for a B image signal, and FIG. 12D is a Y luminance level. It is a histogram about. FIG. 12 also shows pixels extracted for one frame of the image, and each RGB image signal is assumed to be 8-bit data (256 gradations, luminance levels 0 to 255). Further, in FIG. 12, it is assumed that the ratio of the number of pixels in all of the RGB and Y luminance levels is set to 99% from the pixel having the lowest luminance level, and the threshold level is shown in each histogram.

  In the example of FIG. 12, the histogram shape of the luminance level distribution for each RGB is relatively similar, but the threshold level difference for each RGB is relatively large. Further, although the image is a dark image with many pixels on the low luminance side, the maximum luminance level is around 255 in all of RGB.

  When control using single-plane clipping processing is performed on the image having the histogram of FIG. 12, the light emission amount of the R light source 16r is 58.8% (150/255), and the light emission amount of the G light source 16g is 43.5% (111). / 255), the light emission amount of the B light source 16b is 47.5% (121/255), and the display image hardly changes.

  When the control using the three-surface clipping process is performed, the light emission amount of the R light source 16r is 58.8% (150/255), the light emission amount of the G light source 16g is 43.5% (111/255), and the B light source 16b. Is 47.5% (121/255), and the display image hardly changes.

  When the control using the Y clip process is performed, the light emission amount of the R light source 16r is 66.3% (169/255), the light emission amount of the G light source 16g is 48.2% (123/255), and the B light source 16b The light emission amount is 54.5% (139/255), and the display image hardly changes.

  For this reason, the CPU 18 determines that the control using the three-side clipping process having the largest power consumption effect is optimal for an image having the characteristics shown in FIG.

  FIG. 13 is a diagram showing a luminance level distribution histogram and a Y luminance level distribution histogram for each RGB created by the image feature amount extraction unit 22 for another image. 13A is a histogram for an R image signal, FIG. 13B is a histogram for a G image signal, FIG. 13C is a histogram for a B image signal, and FIG. 13D is a Y luminance level. It is a histogram about. FIG. 13 also shows pixels extracted for one frame of the image, and each RGB image signal is 8-bit data (256 gradations, luminance levels 0 to 255). Further, in FIG. 13, it is assumed that the ratio of the number of pixels in all the RGB and Y luminance levels is set to 99% from the pixel having the lowest luminance level, and the threshold level is shown in each histogram.

  In the example of FIG. 13, the histogram shape of the luminance level distribution for each RGB is greatly different, there are many pixels with a high R luminance level, and many pixels with a low G and B luminance level (for example, a sunset scene). .

  When control using single-plane clipping processing is performed on the image having the histogram of FIG. 13, the light emission amount of the R light source 16r is 99.6% (254/255), and the light emission amount of the G light source 16g is 100% (255/255). ), The light emission amount of the B light source 16b is 100% (255/255), and the display image hardly changes, but the power consumption can hardly be reduced.

  When the control using the three-surface clipping process is performed, the light emission amount of the R light source 16r is 99.6% (254/255), the light emission amount of the G light source 16g is 99.2% (253/255), and the B light source 16b. Is 31.8% (81/255), but the luminance is reversed between the high luminance portion and the low luminance portion, and image degradation occurs.

  When control using the Y clip process is performed, the light emission amount of the R light source 16r is 99.6% (254/255), the light emission amount of the G light source 16g is 100% (255/255), and the light emission amount of the B light source 16b. Is 91.2% (234/255), and the display image hardly changes.

  For this reason, the CPU 18 determines that the control using the Y clip process is optimal for an image having the characteristics shown in FIG.

  In the present embodiment, since it is possible to perform control using optimal clip processing according to the characteristics of an image, it is possible to reduce power consumption without causing image degradation.

  Needless to say, the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea. For example, in the above embodiment, an image projection device is shown as an example of a display device, but the present invention can also be applied to other display devices such as a liquid crystal display. In the above embodiment, the light emission color of the light source 14 is RGB. However, for example, the light emission color of the light source 14 can be a combination of cyan, magenta, yellow, and the like. Furthermore, in the above embodiment, the case of RGB three colors has been described. However, the present invention can also be applied to a display device including light sources of four or more colors (for example, four colors of RGB and emerald green). In the case of using four-color light sources, the clip processing performed on the three-dimensional orthogonal graph may be extended to the four-dimensional orthogonal graph.

It is a block diagram which shows the whole structure of the display apparatus which concerns on Embodiment 1 of this invention. 5 is a flowchart illustrating a procedure in which an image feature amount extraction unit and a CPU calculate a light source control value and an image correction value in the first embodiment. It is a graph which shows the example of the histogram of the luminance level distribution produced by the image feature-value extraction part. It is the graph which represented the luminance level of each pixel contained in an image signal as a coordinate. It is the graph which showed the emitted light amount of each color adjusted with the light source control value. 12 is a flowchart illustrating a procedure in which an image feature amount extraction unit and a CPU perform a light source control value and an image correction value in the display device according to the second embodiment. It is a graph which shows the example of the histogram of the luminance level distribution produced by the image feature-value extraction part. It is the graph which showed the emitted light amount of each color adjusted with the light source control value. It is a figure which shows the rectangular parallelepiped prescribed | regulated in the orthogonal graph in which each axis | shaft represents the luminance level for every RGB. 14 is a flowchart illustrating a procedure in which an image feature amount extraction unit and a CPU calculate a light source control value and an image correction value in the display device according to the third embodiment. It is the figure which showed the histogram of the luminance level distribution for every RGB and the histogram of Y luminance level distribution which the image feature-value extraction part produced about a certain image. It is the figure which showed the histogram of the luminance level distribution for every RGB which the image feature-value extraction part produced | generated about another image, and the histogram of Y luminance level distribution. It is the figure which showed the histogram of the luminance level distribution for every RGB and the histogram of Y luminance level distribution which the image feature-value extraction part produced about another image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image processing part 12 Image modulation part 14 Light source 16 Light source control part 18 CPU
20 Image composition unit 22 Image feature amount extraction unit 24 Pixel number ratio setting unit

Claims (11)

A light source means that emits light of a plurality of different colors, and capable of adjusting a light emission amount for each emission color;
Light source control means for controlling the amount of light emitted by the light source means for each emission color;
Image processing means for inputting an image signal including a luminance level for each emission color corresponding to each pixel to be displayed, and performing predetermined processing on the image signal to generate image data;
Image modulation means for spatially modulating the light emitted by the light source means for each of the emission colors based on the image data;
Image feature amount extraction means for inputting the image signal and extracting the feature amount of the image signal;
Based on the feature amount of the image signal extracted by the image feature amount extraction unit, a light source control value for changing the light emission amount of the light source unit is calculated and supplied to the light source control unit, and the image data is corrected. Arithmetic processing means for calculating an image correction value and supplying the calculated value to the image processing means;
With
The image feature amount extraction unit creates a histogram of luminance level distribution for each of the emission colors for each pixel included in the image signal, and in advance from the pixel of the lowest or highest luminance level in the histogram for each emission color. A threshold level that is a ratio of the set number of pixels is obtained for each emission color, and the arithmetic processing unit calculates the light source control value and the image correction value for each emission color based on the threshold level. Display device. The image feature amount extraction unit and the arithmetic processing unit obtain a threshold level having the largest value among the threshold levels obtained for each of the emission colors as a clip level, and determine the emission color that becomes the largest threshold level. The reference clip color
For a pixel having a luminance level of the reference clip color equal to or higher than the clip level, the luminance level of the reference clip color is set as the clip level, and the luminance level of the emission color other than the reference clip color is multiplied by the clip level. Apply the process of dividing by the luminance level of the reference clip color of the pixel,
From the luminance level subjected to the processing and the luminance level of the pixel whose luminance level of the reference clip color is less than the clip level, a maximum clip value that is the maximum value for each emission color is obtained,
The arithmetic processing means calculates the light source control value based on the maximum clip value, and adjusts the amount of light emitted by the light source means,
For each pixel included in the image signal, it is determined whether the luminance level of the reference clip color is equal to or higher than the clip level, and the luminance of the pixel of which the luminance level of the reference clip color is equal to or higher than the clip level and the luminance of the reference clip color The display device according to claim 1, wherein different image correction values are calculated for pixels whose level is less than the clip level.   3. The light source control value according to claim 2, wherein the arithmetic processing unit calculates a light source control value so that a light emission amount of the light emitted from the light source unit is proportional to the clip maximum value for each light emission color. Display device. The arithmetic processing means calculates the image correction value as a value that is inversely proportional to the light emission amount of the light emitted by the light source means for each light emission color for pixels whose luminance level of the reference clip color is less than the clip level. For a pixel having a luminance level of the reference clip color equal to or higher than the clip level, a value that is inversely proportional to the light emission amount of the light emitted by the light source unit for each emission color is multiplied by the clip level to obtain the reference clip color of the pixel. The image correction value is calculated as a value divided by the luminance level of
The display device according to claim 2, wherein the image processing unit performs correction by multiplying the image data by the calculated image correction value. The image feature amount extraction unit or the arithmetic processing unit sets a threshold level obtained for each emission color as a clip level of each emission color,
The arithmetic processing means calculates the light source control value based on the clip level, and adjusts the amount of light emitted by the light source means,
For each pixel included in the image signal, it is determined whether at least one of the luminance levels for each emission color is equal to or higher than the clip level, and at least one of the luminance levels for each emission color is equal to or higher than the clip level. 2. The display device according to claim 1, wherein different image correction values are calculated for pixels whose luminance levels for each pixel and the emission color are all lower than the clip level.   6. The light source control value according to claim 5, wherein the arithmetic processing unit calculates a light source control value so that a light emission amount of light emitted from the light source unit is proportional to the clip level for each of the light emission colors. Display device. The arithmetic processing unit calculates the image correction value as a value that is inversely proportional to the light emission amount of the light emitted by the light source unit for each light emission color for pixels whose luminance levels for each light emission color are less than the clip level. For a pixel in which at least one of the luminance levels for each of the emission colors is equal to or higher than the clip level, in the orthogonal graph in which each axis represents the luminance level for each of the emission colors, a plane that passes through the origin and is orthogonal to each axis; The light source means defines the rectangular parallelepiped in a plane perpendicular to each axis with the clip level value of each light emitting color, obtains the intersection of the straight line connecting the origin and the coordinates of the pixel and the rectangular solid, and the light source means for each light emitting color. The image correction value is calculated as a value obtained by multiplying the value inversely proportional to the amount of light emitted by the distance from the intersection to the origin and dividing by the distance from the coordinates of the pixel to the origin,
The display device according to claim 5, wherein the image processing unit performs correction by multiplying the image data by the calculated image correction value. Light source means that emits red, green, and blue light, and can adjust the amount of light emission for each emission color;
Light source control means for controlling the amount of light emitted by the light source means for each emission color;
Image processing means for inputting an image signal including a luminance level for each emission color corresponding to each pixel to be displayed, and performing predetermined processing on the image signal to generate image data;
Image modulation means for spatially modulating the light emitted by the light source means for each of the emission colors based on the image data;
Image feature amount extraction means for inputting the image signal and extracting the feature amount of the image signal;
Based on the feature amount of the image signal extracted by the image feature amount extraction unit, a light source control value for changing the light emission amount of the light source unit is calculated and supplied to the light source control unit, and the image data is corrected. Arithmetic processing means for calculating an image correction value and supplying the calculated value to the image processing means;
With
The image feature amount extraction unit or the arithmetic processing unit calculates the Y luminance level by performing YUV conversion on the luminance level of each pixel included in the image signal, creates a histogram of the Y luminance level distribution, In the luminance level distribution histogram, a threshold level that is a ratio of the number of pixels set in advance is determined from the pixels with the lowest or highest Y luminance level, and the Y luminance level of each pixel is processed based on this threshold level. From the corrected luminance data, the maximum luminance value for each emission color is calculated from the corrected luminance data for each pixel by performing inverse YUV conversion from
The display device characterized in that the arithmetic processing means calculates the light source control value and the image correction value for each light emission color based on the maximum clip value.   The image feature amount extraction unit or the arithmetic processing unit performs a process of setting the Y luminance level of the pixel to the threshold level for a pixel having the Y luminance level equal to or higher than the threshold level, The corrected luminance data is calculated using a Y luminance level of a pixel whose Y luminance level is lower than the threshold level, and U and V values of each pixel obtained by the YUV conversion. Item 9. The display device according to Item 8.   10. The arithmetic processing unit calculates a light source control value so that a light emission amount of light emitted from the light source unit is proportional to the clip maximum value for each emission color. The display device described in 1. The arithmetic processing means calculates the image correction value as a value that is inversely proportional to the amount of light emitted by the light source means for each emission color,
The display device according to claim 8, wherein the image processing unit multiplies the calculated image correction value by the image data to perform correction.

Images