| 摘要 |
PURPOSE:To enable read-time measurement eliminating effect of extraneous light, by incorporating laser transmitting and receiving sections into the same substrate while a laser beam from a laser transmitter is used by amplitude modulation. CONSTITUTION:A laser transmitting section and a laser receiving section are incorporated into the same substrate while a laser beam 41 to be emitted from a laser oscillator 4 is turned to a laser beam 42 amplitude modulated 5, which is separated into a reference laser beam 43 and a measuring laser beam 44. The measuring laser beam 44 is reflected on a reflection mirror 8 arranged in a space to be measured and received with a detector 74. Then, the reference signal and measurement signal of synchronous detection circuits 101 and 102 are inputted into a computing circuit such as microcomputer, with which the concentration of dust can be measured in real time from a propagation loss of a light wave. Outputs of detectors 72 and 74 are only confined to a light signal of a modulation frequency component thereby enabling measurement free from effect of external invasion light. |
