Patent ID: 8636365

Claim:
A projection display device, comprising: a first display panel configured to realize an image of only a first color; a second display panel configured to realize an image of only a second color; a third display panel configured to realize an image of only a third color, the first, second, and third colors being different; a fourth display panel configured to realize only a white image; an optical system configured to combine the images of the first to third colors into a full color image, to combine the full color image and the white image into a combined image, and to project the combined image onto a screen; and an image processing unit configured to transmit a video signal into the first through third display panels and to extract grayscale data from the video signal, wherein the first to third display panels are self-emissive, wherein the fourth display panel is between the screen and one of the first to third display panels, the fourth display panel being configured to display the white image according to a grayscale of the full color image, wherein, when the extracted grayscale data is lower than a specific grayscale, the image processing unit is configured to generate a white video signal that corresponds to a grayscale that is lower than the extracted grayscale by a predetermined low level, and to transmit the white video signal to the fourth display panel, and wherein, when the extracted grayscale data is higher than a specific grayscale, the image processing unit is configured to generate a white video signal that corresponds to a grayscale that is higher than the extracted grayscale by a predetermined high level and to transmit the white video signal to the fourth display panel.