| 摘要 |
PURPOSE:To accomplish a simple and stable gradation image recording by a method wherein a plurality of heating elements are provided corresponding to one picture element of an original picture and the duration of supply of current to each element is varied, in a thermal recording system using a plurality of heating element. CONSTITUTION:One-line portion of information representing the gradations corresponding to the picture elements is transferred to a line buffer 6. A signal converting circuit 4 receives the gradation information and converts it into a driving signal corresponding to a printing unit 3. At this instant, one of the printing patterns which belong to the same gradation information is selected by a random number generating circuit 5. The heating elements 1' conduct a printing in a gradation of white, halftone or black under the function of the driving signal. Accordingly, a stable gradation image can be obtained by a system in which the whole gradation is obtained from coloring densities, and it is unnecessary to use paper of extreme smooth surface. In addition, since the pringing patterns are selected at random, it is possible to prevent the generation of grain direction streaks. |
