Device for expanding light-amount correction dynamic range

Abstract

A light-amount correction dynamic range expanding device that can increase the number of exposure gray levels without increasing the memory capacity of the storage section for light-amount correction. Input data is formed of (n+k) bits to increase exposure gray-scale level. A first look-up table stores the output densities to the number of exposure gray levels for photosensitive substances classified by photosensitivity. Of (n+k) bits output from the first table, a first selector selectively outputs only effective n bits to a second table 2 to use m bits needed for a photosensitive substance. The second look-up table stores brightness information to correct variations in brightness between luminous dots of a print head, with a memory capacity of n bits. A FIFO memory temporarily stores the brightness information. A selector 2 again converts the output from the FIFO memory into a (n+k)-bit form and ten it to a gray-scale control means. The gray-scale control means controls the gray scale of the print head with the (n+k) bit data, so that the brightness variation is corrected with n-bit data and with necessary and sufficient accuracy.