Display device for creating intermediate gradation levels in pseudo manner and image signal processing method

A display apparatus comprising:

• a gradation change detector to generate a control signal when a gradation change of one gradation level is detected between adjacent image data among a plurality of pieces of image data which is input continuously with respect to time, and when a number of gradations of a plurality of pieces of image data input before the gradation change are detected to be equal to each other and a number of gradations of a plurality of pieces of image data input after the gradation change are detected to be equal to each other, in a case where one screen is displayed on a display section according to one of a plurality of fields and frames, and when a number of gradation bits possessed by image data is equal to a number of gradation bits possessed by said display section, a display of a number of gradation bits, which is greater than the numbers of gradation bits, is produced by said display section;
• and
• an image data converter to receive said control signal and perform at least one of (i) a process to convert the gradation level of image data before said gradation change into the gradation level of image data after said gradation change either in one of two fields which are adjacent with respect to time or in one of two frames which are adjacent with respect to time, and (ii) a process to convert the gradation level of image data after said gradation change into the gradation level of image data before said gradation change either in one of two fields which are adjacent with respect to time or in one of two frames which are adjacent with respect to time.