| 摘要 |
<p>PURPOSE:To enhance detection sensitivity by determining the high-band cut-off frequency of a band-pass filter from the frequency spectrum of an incoming infrared ray which is calculated from the width of an object for detection, the width of a detecting beam, and the upper limit speed of movement of the object for detection. CONSTITUTION:When an object for detection with width Ls passes a detecting beam of width Lr at a moving speed V, the fundamental wave component fs(fr) of the frequency spectrum of the temperature (detecting beam sensitivity) distribution characteristic of the object for detection V/Ls (fr V/Lr). The fundamental wave component fx of the frequency spectrum Y(f) of an incoming infrared ray = fs (Ls>Lr) or = fr (Ls<Lr). When frequencies lower than the peak level of the spectrum Y(f) by several dB, e.g. those in a band higher than near fx/2 are eliminated, infrared outputs can be taken out efficiently. Therefore, the high-band cut-off frequency of a band-pass filter 13 is theoretically supported and determined by the spectrum Y (f) calculated from the widths Ls, Lr and the upper limit speed of movement of the object for detection.</p> |
