Ricoh Company, Ltd.

Chiharu Okada

Masaaki Mori

Toshio Kawakami

A pattern memory for use in a thermal printer system stores a temperature-compensated pattern of a character to be printed on recording paper using a thermal print head having a plurality of heat-producing elements arranged in a single array is provided. The pattern is defined in the form of a dot matrix, each dot containing two or more binary data, each of which, if having a predetermined one of the two possible states, is associated with a predetermined activation time period for activating one of the heat-producing elements. The binary state of each of the two or more data in each dot is determined such that a level of heat produced by any of the heat-producing elements may be maintained at constant. In one embodiment having two binary data in each dot, the pattern is determined such that the one of the two data of a dot has '0' and the other has '1' if this dot is to be printed for a second time or more by the same heat-producing element in succession.

Pattern memory for use in thermal recording

A thermal print head driving system supplies a predetermined number of driving pulses to each of a plurality of heat-producing elements arranged in a line to record a single dot of desired tone. The pulse width of driving pulse is controlled in accordance with the temperature at or in the vicinity of the heat-producing elements thereby allowing to maintain the density level of desired tone at constant. In another aspect of the present invention, it is so structured that driving pulses may be applied to the heat-producing elements in a continuous manner without producing a cooling period during switching between tone levels. In a further aspect of the present invention, it is so structured that a predetermined number of driving pulses for each of predetermined number of tone levels is altered in consideration of the data in at least one of preceding recording lines, thereby allowing to carry out a high speed recording operation without causing fluctuations in predetermined tone density level.

Thermal print head driving system

A thermal recording system includes a thermal print head provided with a plurality of electrical resistors arranged in the form of a single row and selectively activated when an activation pulse is supplied, a brute supply for supplying a power supply voltage to the resistors and a pulse generator for controlling the duration of the activation pulse in accordance with the level of the power supply voltage actually applied to the resistors. The pulse generator controls the pulse width of the activation pulse so as to maintain substantially constant the activation energy defined as a product of (power supply voltage actually applied).sup.2 and (pulse width of activation pulse).

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Tokyo, Japan

Chiharu Okada