| 摘要 |
<p>The appts (10) includes at least one detector circuit (12) having circuitry (14) for cancelling background radiation, a signal amplifier stage (16) adapted to receive and amplify a signal from the detector circuit (12) and a number of discrete frequency detection circuits (18), which have a common input (20) and a number of outputs (22). A photodetector is also included which is of the type for generating an electronic signal contg all modulation frequencies of the illuminating light. The laser detector circuit generates an output signal contg all laser modulation frequencies of an illuminating light. The signal amplifier stage is adapted to receive the output signal generated by the laser detector circuit and provide an amplified output signal. Each discrete frequency detection circuit includes a device for providing an output signal in response to the presence of a preselected laser modulation frequency in the amplified output signal.</p> |
