Liquid crystal display apparatus for generating an output video signal based on an input video signal and a lighting signal

Abstract

A LCD display includes a light source section, a LCD panel including a plurality of pixels each having sub-pixels of R, G, B, and Z, and a display control section including an output signal generation section. The display control section performs a display drive on the sub-pixels with use of the respective output video signals, and performs a lighting drive on the light source section with use of the lighting signal. The output signal generation section generates output video signals corresponding to the respective four colors, based on the input video signals, and generates a lighting signal of the light source section, based on the input video signals, to perform a predetermined dimming processing, based on both the input video signals and the generated lighting signal, and finally generates the output video signals through performing a predetermined color conversion processing, based on a resultant video signal from the dimming processing.

What is claimed is: 
     
       1. A liquid crystal display apparatus, comprising:
 a light source; 
 a liquid crystal display panel including a plurality of pixels, each pixel of the plurality of pixels having sub-pixels of three colors including red (R), green (G), and blue (B), and a sub-pixel of a color (Z) with a luminance higher than those of the three colors; and 
 a display control circuit including an output signal generation circuit, a backlight driving circuit and a data driver for the liquid crystal display panel, wherein 
 the output signal generation circuit includes a backlight level calculation circuit, a level calculation circuit and a predetermined color conversion circuit, 
 the backlight level calculation circuit receives an input video signal that includes only colors R, G and B, and generates a lighting signal by processing the input video signal, 
 the level calculation circuit receives the input video signal and the lighting signal and generates a resultant video signal that includes only colors R, G and B, by performing a dimming processing on the input video signal according to the lighting signal, and 
 the predetermined color conversion circuit generates an output video signal that includes colors R, G, B and Z, by processing the resultant video signal, the processing including performing predetermined chromaticity point adjustment on the resultant video signal to allow a chromaticity point of display light emitted from the liquid crystal display panel to come to a white color chromaticity point, and performing a color conversion processing on the resultant video signal after the chromaticity point adjustment. 
 
     
     
       2. The liquid crystal display apparatus according to  claim 1 , wherein the predetermined color conversion circuit uses a look-up table (LUT) when generating the output video signal, the LUT provided in advance according to nonlinearity in a relationship between a signal level of a Z-sub-pixel video signal of the output video signal and a signal level of each of R-, G-, and B-sub-pixel intermediate video signals which are specified when an assumption is made that the signal level of the Z-sub-pixel video signal is replaced by a set of the R-, G-, and B-sub-pixel intermediate video signals. 
     
     
       3. The liquid crystal display apparatus according to  claim 1 , wherein the output signal generation circuit performs the color conversion processing to allow the signal levels of sub-pixel video signals configuring the output video signal to be substantially equal to one another. 
     
     
       4. The liquid crystal display apparatus according to  claim 1 , wherein the output signal generation circuit limits, in a color conversion processing, signal levels of sub-pixel video signals configuring the output video signal to be equal to or less than a predetermined upper limit. 
     
     
       5. The liquid crystal display apparatus according to  claim 1 , wherein the output signal generation circuit generates the lighting signal with use of a look-up table (LUT) which specifies, in advance, a relationship between a chromaticity represented by the input video signal and a highest signal level expressible for a corresponding chromaticity or the inverse of the highest signal level. 
     
     
       6. The liquid crystal display apparatus according to  claim 5 , wherein the LUT limits signal level variation in the lighting signal which is specified by a chromaticity variation in the input video signal to be equal to or lower than a predetermined threshold level. 
     
     
       7. The liquid crystal display apparatus according to  claim 1 , wherein each of the pixels includes a sub-pixel of white (W) as the sub-pixel of Z. 
     
     
       8. The liquid crystal display apparatus according to  claim 7 , wherein the sub-pixels of the three colors are provided with color filters corresponding to respective colors of R, G, and B, and the sub-pixel of W is provided without a color filter. 
     
     
       9. The liquid crystal display apparatus according to  claim 1 , wherein
 the predetermined color conversion circuit further includes a chromaticity point adjustment circuit and a color conversion circuit, 
 the chromaticity point adjustment circuit adjusts the chromaticity of the resultant video signal, and 
 the color conversion circuit generates the output video signal by performing the color conversion processing on the resultant video signal. 
 
     
     
       10. The liquid crystal display apparatus according to  claim 1 , wherein
 the display control circuit further includes a timing control circuit, 
 the backlight level calculation circuit outputs the lighting signal to the timing control circuit, and 
 the predetermined color conversion circuit outputs the output video signal to the timing control circuit. 
 
     
     
       11. The liquid crystal display apparatus according to  claim 10 , wherein
 the timing control circuit supplies a driving signal based on the lighting signal and the output signal to the data driver. 
 
     
     
       12. The liquid crystal display apparatus according to  claim 1 , wherein the backlight level calculation circuit generates the lighting signal by processing only the input signal. 
     
     
       13. A video signal generating apparatus, comprising:
 a backlight level calculation circuit that receives an input video signal and generates a lighting signal by processing the input video signal; 
 a level calculation circuit that receives the input video signal and the lighting signal and generates a resultant video signal by performing a dimming processing on the input video signal according to the lighting signal; and 
 a predetermined color conversion circuit that generates an output video signal by processing the resultant video signal, the processing including performing a predetermined chromaticity point adjustment on the resultant video signal to allow a chromaticity point of display light emitted from the liquid crystal display panel to come to a white color chromaticity point, and performing a color conversion processing on the resultant video signal after the chromaticity point adjustment, wherein 
 the input video signal and the resultant video signal include only colors red (R), green (G), and blue (B), and 
 the output video signal includes colors R, G, B and a fourth color (Z). 
 
     
     
       14. The video signal generating apparatus according to  claim 13 , wherein the predetermined color conversion circuit uses a look-up table (LUT) when generating the output video signal, the LUT provided in advance according to nonlinearity in a relationship between a signal level of a Z-sub-pixel video signal of the output video signal and a signal level of each of R-, G-, and B-sub-pixel intermediate video signals which are specified when an assumption is made that the signal level of the Z-sub-pixel video signal is replaced by a set of the R-, G-, and B-sub-pixel intermediate video signals. 
     
     
       15. The video signal generating apparatus according to  claim 13 , wherein the predetermined color conversion circuit performs the color conversion processing to allow the signal levels of sub-pixel video signals configuring the output video signal to be substantially equal to one another. 
     
     
       16. The video signal generating apparatus according to  claim 13 , wherein the backlight level calculation circuit generates the lighting signal by processing only the input signal. 
     
     
       17. The video signal generating apparatus according to  claim 13 , wherein
 the predetermined color conversion circuit further includes a chromaticity point adjustment circuit and a color conversion circuit, 
 the chromaticity point adjustment circuit adjusts the chromaticity of the resultant video signal, and 
 the color conversion circuit generates the output video signal by performing the color conversion processing on the resultant video signal. 
 
     
     
       18. The video signal generating apparatus according to  claim 13 , further comprising a timing control circuit, wherein
 the backlight level calculation circuit outputs the lighting signal to the timing control circuit, 
 the predetermined color conversion circuit outputs the output video signal to the timing control circuit, and 
 the timing control circuit generates a driving signal based on the lighting signal and the output signal.