Method and apparatus for thermal printing

Claim 3

The method according to claim 1 wherein said resistance value detection is performed each time said apparatus is connected to a source of electric power.

Claim 4

The method according to claim 1 wherein said updating of the contents of said memory means is effected each time the resistance value of any heat generating resistor is detected.

Claim 5

The method according to claim 1 which further comprises the steps of preparing a memory table storing electric power values to be supplied to respective heat generating resistors and calculating electric power values supplied to said heat generating resistors by reading out contents of said table.

Claim 6

The method according to claim 1 wherein said thermal head is driven by a source of constant voltage or constant current, and said power is supplied by controlling an interval of supplying said constant voltage or constant current to said heat generating resistors.

Claim 7

Thermal printing apparatus comprising: a thermal head including a plurality of heat generating resistors which generate heat when supplied with electric power; means for detecting resistance values of said heat generating resistors in accordance with a signal at a predetermined time before driving said thermal head; memory means for storing resistance values of said heat generating resistors detected by said detecting means; means for updating contents of said memory means each time said detecting means operates; an arithmetic operating circuit for calculating quantity of electric power to be supplied to respective heat generating resistors in accordance with the contents of said memory means; and a thermal head drive circuit for selecting one of said heat generating resistors to be operated in accordance with a picture information supplied to said thermal printing apparatus; said thermal head drive circuit supplying to said selected one of said heat generating resistors electric power of a quantity calculated by said arithmetic operating circuit.

Claim 8

Thermal printing apparatus comprising: a thermal head including a plurality of heat generating resistors which generate heat when supplied with electric power; means for detecting resistance values of said heat generating resistors in accordance with a signal at a predetermined time before driving said thermal head; memory means for storing resistance values of said heat generating resistors detected by said detecting means; means for updating contents of said memory means each time said detecting means operates; an arithmetic operating circuit for calculating quantity of electric power to be supplied to respective heat generating resistors in accordance with the contents of said memory means; and a thermal head drive circuit for selecting one of said heat generating resistors to be operated in accordance with a picture information supplied to said thermal printing apparatus; said thermal head drive circuit supplying to said selected one of said heat generating resistors electric power of a quantity calculated by said arithmetic operating circuit.

Claim 9

The apparatus according to claim 6 wherein said signal generated at said predetermined time is a source ON signal when a switch for connecting said apparatus to an electric source is closed.

Claim 10

The apparatus according to claim 6 wherein said memory means comprises a random access memory circuit.

Claim 11

The apparatus according to claim 6 wherein said arithmetic operation circuit includes a memory table for storing quantities of electric power to be supplied to respective heat generating resistors corresponding to the resistance values detected by said detecting means.

Claim 12

The apparatus according to claim 6 wherein said thermal head drive circuit includes a source of constant voltage or constant current and wherein supply of electric power to respective heat generating resistors is controlled by controlling intervals of energizing said heaters.