| 摘要 |
PURPOSE:To materialize gradation processing by a method wherein a plurality of drive circuits are provided to an image formation apparatus, and drive signals from the drive circuits are added up. CONSTITUTION:Output current from constant-current circuits A1-A64 of a drive circuit 16 is made 1mA, the output current from the constant-current circuits B1-B64 of the drive circuit 18 is made 2mA, the output current from the constant-current circuits C1-C64 of the drive circuit 20 is made 4mA and the output current from the constant-current circuits D1-D64 of the drive circuit 22 is made 8mA. By providing above-mentioned four drive circuits 16-22, 4 bit gradation in 1mA-15mA can be achieved. Strobe signal to the constant- current circuits A1-A64 and others is controlled on every 2mus in 16 gradations from 0 to 32mus. The strobe signal is controlled on every drive circuit in 16 gradations, while the drive signal is controlled on every LED in 16 gradations and by summing both up, gradations approximately in 240 can be achieved for any one of the LED's. Thereby gradation processing can be materialized. |
