Abstract: In an RGBW-type liquid crystal display device, luminance is improved by the addition of W sub-pixels while an image is displayed without any change in chromaticity of halftones. Digital corrected values of red, green and blue are obtained by adding a predetermined digital value for driving a W sub-pixel to each of RGB digital values which correspond respectively to pixels of an acquired image. A converting calculation is effected on the digital corrected values such that the ratio of these digital corrected values for red, green and blue is made equal to the ratio of the red, green and blue digital values corresponding to the pixels of said acquired image. The RGBW sub-pixels are driven with the converted values and the predetermined digital value of driving W sub-pixel to thereby display an image.

Abstract: A video signal interpolation can adapt an image of input video signal to voluntary aspect ratios widely. The invention also allows a display device to uniformly line-sequential scan and uses at least two line-memories (LM1, LM2) which are applied with an input digital video signal and controls writing and reading for these line-memories to generate a video signal subjected to vertical interpolation from a reading output of the line-memories. In the control, any one of the line-memories are circularly selected, and a sample sequence of the input digital video signal is sequentially written into the selected line-memory at its sample rate while sequentially reading out samples of the written sequence at a constant rate which is higher than the sample rate and which is according to a desired ratio of interpolation (vertical expansion ratio), wherein, when one of the line-memories is in writing operation, the other one of the line-memories is repeatedly read out.