JPS6442256A - Thermal printer - Google Patents

Abstract

PURPOSE:To make photographic printing density uniform, by controlling heating energy to be applied to a thermal head by detecting current flowing to each heating resistor in each block of the thermal head. CONSTITUTION:When current is preliminarily supplied to all of respective heating resistors 121, 122, 123, 124 in each block of a thermal head either in making of a power source or in initial setting, this current is detected with a resistor 7, and the detected current is inputted to an A/D converter 6, is converted to a digital value to be transferred to a CPU 3. The CPU 3 uses those values measured at each block, calculates so that heating energy in each block becomes constant, and stores in a RAM 5. Then, in actual photographic printing operation, an electroenergizing pulse width is so controlled that the preliminarily stored heating energy is applied to the thermal head 1 with RAM 5 storing electroenergizing time in which the heating energy in each block becomes constant. Thus, a density of the obtained photographic printing becomes uniform.