| 摘要 |
PURPOSE:To stably record an image increased in the number of gradations, by realizing the magnification of the number of gradations due to lower rank (m+n) bits (m and n are a positive integer) of the gradation data of one pixel unit 2<k>(k is a positive integer) gradation by aeral gradation due to a matrix of longitudinal/lateral 2<m>X2<n> pixels. CONSTITUTION:Four-bit threshold value data corresponding to the block internal position of 4X4 pixels shown by lower rank 2 hits of an address counter 6 and a line counter 10 written in an ROM 11 and the data of the lower rank bits of a line memory 5 are compared with each other by the second comparator 12 and, when the latter is larger than the former, a raising signal (b) is set to 1 and the pixel pulse width thereof is made long. As mentioned above, 2<k> gradation due to higher rank (k) bits of the gradation data stored in the line memory 5 is realized in one pixel unit on the basis of the density gradation due to the control of the current supply pulse width of both of a gradation counter 8 and the first comparator 9, and the magnification of the number of gradations due to the lower rank (m+n) bits of gradation data is realized by the areal gradation due to the matrix of the longitudinal/lateral 2<m>X2<n> pixels of the ROM 11. By this method, an image increased in the number of gradations can be stably recorded. |
