| 摘要 |
PURPOSE:To improve the S/N, and to detect a more minute particle by shaping an optical pulse from a particle to a form having a periodicity by using a double slit, making it pass through a BPF conforming to its period and executing a square-law integration. CONSTITUTION:A scattered light from a particle 3 is condensed by a condensing lens 4 and made to form an image on a double slit 10. In this case, since the particle 3 is moving, the image also moves on the slit 10. A signal from a photoelectric converting element 5 is amplified by an amplifier 6, and its output C shows a waveform (c) consisting of a signal c1 having a periodicity from the particle 3 and a high and low noise c2. A signal of this waveform (c) passes through a BPF 11 and an output D becomes a pulse (d) having a periodicity. That is to say, a noise except a movement of the particle 3 and a frequency generated from the slit 10 becomes an eliminated signal. By making it pass through a square-law integration circuit 12, an output E of the circuit 12 becomes a single pulse (e). This pulse (e) is led to a comparator 8 and a counter 9, and submitted for counting the particle.
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