| 摘要 |
<p>PURPOSE:To correct deviations of the quantity of light emitted from each LED while using a simple circuit, by providing a correction value ROM for preliminarily storing correction command data for correcting variations in the density of dots printed by a plurality of LEDs. CONSTITUTION:Constant current driving circuits 3-1 3-3 so function that constant currents determined by external resistances R, 2R, 4R are supplied respectively to LED1-LEDn in an added manner. The value of the current is increased exponentially with 2 as a base, namely, in the manner of 1 time, 2 times and 4 times as large as a fundamental value under the functions of the external resistances R, 2R and 4R. Where a bit supplied from a correction value ROM 1 is '1' and serial data (b) is '1', constant current I13, I12, I11 corresponding to the external resistances 4R, 2R, R are supplied from the constant current driving circuits 3-3, 3-2, 3-1 to the LED in an added manner. Accordingly, variations in the quantity of light emitted from each of LEDs constituting an LED array can be corrected by a simple circuit construction.</p> |
