| 摘要 |
PURPOSE:To drive a photosensor with a low power by a method wherein digital drive signals which enable a light emitting element to increase or decrease gradually in emission volume are converted into analog signals and stored when digital signals from a photodetective element reach to a certain level. CONSTITUTION:A CPU 10 gives digital drive signals, which drive a transistor 5 and enables a light emitting element 1 to increase or decrease gradually in emission volume, to a D/A converter 7. The digital drive signals are converted into analog drive signals through the D/A converter 7, which are transmitted to the base of the transistor 5. The transistor 5 enables the light emitting element 1 to emit light as analog output signals corresponding to the analog drive signals concerned, and the analog output signals are converted into digital signals by an A/D converter 8, which are transmitted to the CPU 10. The CPU 10 stores the level of the digital signals when it becomes equal to a certain level which is previously set in the CPU 10. |
