| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical low-pass filter (OLPF) in which the static electricity generated on the surface of the OLPF is reduced when lithium tantalate is used as substrate material for the OLPF. SOLUTION: The OLPF 1 comprises a birefringent plate 2 made of a crystal, etc. which is worked into a prescribed plate thickness and has birefringence, lithium tantalate is used as substrate material of the birefringent plate, a transparent conductive film 3 is formed on incidence and emission surfaces of a light ray and a conductive film 4 is formed on a surrounding side surface of the birefringent plate 2. When being emitted from the OLPF 1, incident light rays to the OLPF 1 are separated into a normal light ray L2 and an abnormal light ray L3. Upon the use of the OLPF 1, the conductive film 4 is electrically grounded, thereby, the OLPF hardly generates static electricity and the sticking of dusts to the OLPF 1 is reduced. COPYRIGHT: (C)2007,JPO&INPIT
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