Image signal processing device, dither pattern generating method and dither pattern generating program

A storage device stores dither patterns composed of a three-dimensional block consisting of the number H of dots in a horizontal direction×the number V of lines in a vertical direction×the number F in a frame direction. Each value from a minimum value to a maximum value of dither values of n bits is written in each address of the storage device. When each value is written into the storage device, processing of obtaining a spatiotemporal density value indicating a degree of density of an address in which a dither value has already been written in a three-dimensional predetermined area centered on each of the addresses in which a new dither value is writable, and processing of selecting an address having the smallest spatiotemporal density value among the addresses in which a new dither value is writable and writing a dither value are repeated.