| 摘要 |
<p>PURPOSE:To obtain uniform light exposure by a method wherein the previously measured light emitting characteristic information of an LED is written in a ROM, and an initializing action is conducted after the throw-in of a device power source in accordance with the light emitting characteristic information. CONSTITUTION:An n-bit LED of this circuit is emitted in accordance with input data. An n-bit shift register 1 shifts the input data in synchronism with a shift clock and holds it. A latch 2 latches the corresponding content of the shift register on a set signal pulse. Four-bit light quantity correction data is previously written in a register 3 by an initializing action. The OR of the latch 2 with the register 3 is inputted to a constant current driver 6 through an AND circuit 4. A reference current is generated in a current control circuit 7, and the constant current driver 6 allows a constant drive current to flow to an LED 8 to make it emit. A control circuit 5 generates an address signal assigning which bit should be outputted to the AND circuit 4 out of the 4 bits of the register 3 and a reset signal for the latch 2. In this manner, an LED emitting time can be corrected per dot to ensure a uniform light exposure.</p> |
