| 摘要 |
PURPOSE:To count number of passing objects accurately even when plural objects pass simultaneously. CONSTITUTION:When number of objects, for instance human bodies, that pass in front of an infrared-ray sensor 1 is two, infrared rays 41, 42 from the two bodies are inputted to the infrared-ray sensor 1 between time t1 and t2, and between time t3 and t4, and change of respective charge accumulated in the infrared-ray sensor 1 becomes as shown (2) in the figure. Accordingly, pyroelectric current Ip of waveform as shown by (3) in the figure is given to the gate of a field effect transistor 6, and output corresponding to the pyroelectric current Ip is applied to a positive phase input terminal + of the first comparison amplifier 7 through a capacitor C1, and output V of the amplifier 7 becomes waveform (solid line) as (4) in the figure. The output V is applied to the second comparator 8. A signal obtained by differentiating the output V' by a differentiation circuit 9 is applied to the inversion input terminal of the comparator 8. Accordingly, the output V' becomes as shown by solid lines of (5) in the figure, and a signal level of high output can be obtained. |
