| 摘要 |
<p>PURPOSE: To prevent the worsening of input characteristic of a photosensor section by driving and controlling emission by a signal as modulation signal subjected to a low pass filter processing from a photosensor to obtain a light- emitting element drive signal with modulation components removed completely. CONSTITUTION: When a current flows through a conductor 3 while light from a light-emitting element 9 is being supplied to a photocurrent sensor 5, a sensor 5 modulates the supplied light and supplys it to a photo detector 10. The light signal received by the element 10 is amplified 11 and converted (13) into digital from analog to be inputted to a digital signal processor 14 and undergoes a signal processing to be outputted as current value of the conductor 3. A modulation signal from the element 10 is converted 24 digital from analog to be inputted to a CPU 17 while a current measured value of the conductor 3 obtained by the processor 14 is inputted as reference value. The modulation digital signal inputted to the CPU 17 is subjected to a digital processing with a low pass filter to be turned to a DC component Pd with the removal of the modulation signal. Thus, a difference of emissions of the element 9 is judged and driving and controlling of the emission is performed.</p> |
