| 摘要 |
PURPOSE:To prevent the variation in recording density due to the change in circumferential temp., by employing a gradation level threshold value as the function of the circumferential temp. of a thermal head to compensate the circumferential temp. of the thermal head by a recording/auxiliary pulse generating circuit of simple constitution. CONSTITUTION:A gradation level threshold value calculation means 11 calculates a gradation level threshold value from an inputted sub-line value and the circumferential temp. value of a thermal head to output the same to a comparing means 12. The comparing means 12 compares the gradation level threshold value with gradation data and forms a signal having the recording pulse width (Wa-Wc) and auxiliary pulse width (Wa1-Wc1) corresponding to a gradation level to output the same to a polarity selection means 14. The polarity selection means 13 selects the polarities of the recording pulse and auxiliary pulse inputted by a recording/auxiliary pulse applying state signal to apply the same to a thermal head. ROM 61 as a means generating the threshold value for binarizing the gradation data uniquely, a comparator 62 as a means for comparing said threshold value with the gradation data, AND gates 1, 2 calculating AND and an OR gate 3 calculating OR are provided. |
