| 摘要 |
PURPOSE:To prevent malfunction due to light from a mercury lamp by transmitting light within some wavelength range and cutting off light of other wavelength as completely as possible. CONSTITUTION:An optical filter which transmits a light beam of 780-1,000nm is effective to prevention against malfunction. A plate of 0.1-5mm which is formed by mixing a color agent with plastic absorbing none of light of 780-1,000nm and does not transmit light beams of <=780nm-<=900nm and a plate of 0.1-5.0mm which is formed by mixing a near infrared-ray absorber with plastic absorbing none of light of 780-1,000nm are combined together to obtain an infrared-ray band-pass filter which transmit light of 780-1,000nm in wavelength. The operating wavelength of an infrared diode is 500-1,200nm.
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