Image Number 3 for United States Patent #5216440.
A gradation modulating apparatus is provided in a line thermal printer having a plurality of resistive elements arranged linearly widthwise of a medium sheet for printing gradated dots line-sequentially according to gradation image data. A memory is provided for storing individual weight data representative of energy generation rates of respective resistive elements, in corresponding addresses. An address generator is responsive to serial input of the gradation image data for generating an addressing signal effective to read out the stored individual weight data. A modulator is receptive of the inputted gradation data and the read weight data in synchronization with each other for producing modulated gradation image data according to the weight data. A latching circuit is connected for latching the modulated gradation image data line-sequentially. A driver is connected for applying driving signals regulated according to the latched modulated gradation image data to the resistive elements to enable the same to print dots having substantially the same print density for a given gradation level defined by the input gradation data.