| 摘要 |
PURPOSE:To enable to always perform printing in a high density and with high quality, by a method wherein the reflective density of a printing paper before printing and that of blank part of the paper immediately after printing are detected, and the heating power of a thermal head is controlled so that the difference between the densities detected becomes constant. CONSTITUTION:A detector 12 for the reflective density of the printing paper 3 before printing is provided at a former stage of the thermal head 2, while a detector 13 for the reflective density of the blank parts left between characters or symbols on the paper after printing is provided at a later stage of the head 2. Both detection signals are fed into a comparing circuit 15 through a memory circuit 14, and are compared to each other on the basis of a printing command 19, and when there is a difference between the signals, a command for correcting a voltage impressed on the head 2 is fed to correcting circuit 16. Accordingly, it is possible to always print in a high density and with high quality, in response to changes in the ambient temperature and the temperature of the thermal head. |
