| 摘要 |
PURPOSE:To detect signal light having S/N of <=1 by receiving the pulse signal of a light emitting element by a light receiving element and amplifying the reception output and sampling it plural times by an integrating part after digital conversion and integrating the sample value. CONSTITUTION:AD optical pulse signal P outputted from the light emitting element is received through an optical filter 8. The output electric signal is converted to a voltage by a resonance circuit 9, and the DC component and harmonic components are eliminated. The output of the circuit 9 is inputted to a positive terminal 11a of an analog comparator 11 through an amplifying circuit 10. The signal obtained by integrating the output or the circuit 10 for a time sufficiently longer than the period of light emission of the optical signal P is inputted to a negative terminal 11b, and the output signal of the comparator 11 is a binary signal of '0' and '1'. This signal is inputted to an integrating circuit 12, and an adder 15 adds data in each address of a RAM 16 and data inputted from the comparator 11 and writes data in each address. This operation is repeated to perform integration, and the integrated value is stored in each address of the RAM, and each addition data is outputted to a comparator 18, and signal '1' indicating detection of the signal P is outputted when it exceeds the threshold. |
