| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a photoelectronic circuit by which an object to be measured can be measured with high accuracy by feeding back even a change in the emission spectrum of a light emitting element to the driving current of a drive circuit. SOLUTION: A driving current Id is supplied to a light emitting diode LED from a drive circuit 9, light hν' is introduced into an optical sensor 8, and modulated light hν' is received by a photodiode PD. A photocurrent Ip which is generated in the photodiode PD and a reference current Iref are compared by a current comparison circuit 10. At this time, when the emission spectrum of the light emitting diode LED is changed due to a temperature change, a temperature compensation circuit 12 gives a temperature compensation corresponding to the change to the reference current Iref. A comparison currentΔIp which is generated by their comparison is converted into a voltage signalΔVp by a current/voltage conversion circuit 14 so as to be passed through a low-pass filter 15. A DC voltage componentΔVdc in a voltage signalΔVp' which is output from it is extracted by a DC component extraction circuit 16, and the drive circuit 9 is fed back by the DC voltage componentΔVdc.</p> |
