| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic diaphragm device capable of controlling the transmitted light quantity of infrared rays too. SOLUTION: As for the diaphragm device 10 for a CCTV camera lens, a resin-based ND filter 41 having spectral transmittance characteristics that the transmittance in an infrared region is nearly equal to or below the transmittance in a visible ray region, and having a surface reflectance of S about 20/6 is stuck to a an aperture blade 21.
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