| 摘要 |
<p>PURPOSE:To minimize the waviness of a signal waveform by a temperature difference in a visual field and to improve resolution by generating a compensating voltage in accordance with the scanning period of a circular scanning optical system and subtracting the compensating voltage from the output signal of a preamplifying part to amplify the output of an infrared detecting element. CONSTITUTION:The output of an infrared detecting element 2 is amplified by a preamplifying part 3, after that, inputted to a differential amplifying part 8 and the compensating voltage generated by a compensating voltage generating part 7 is subtracted. A/D-converted waveforms are successively fetched while the scanning angle of a circular scanning optical system is from pi/2 radian to 3pi/2 radian. The compensating voltage generating part 7 is controlled so as to boost the compensating voltage when the scanning angle becomes pi/2 radian and drop the compensating voltage when the scanning angle becomes 3pi/2 radian. In a judging part 5, an output waveform at the time when a human body does not exist in a detecting area is stored beforehand in a memory as a reference waveform and an input waveform is compared with the reference waveform in the memory and the presence and absence of the human body and the number of persons are judged simultaneously.</p> |
