| 摘要 |
<p>If the thickness of a birefringence plate that forms an optical low-pass filter is not appropriately set, problems in terms of optical characteristics or machine works are posed. Hence, there is provided an optical low-pass filter which has at least one birefringence plate which is made of a uniaxial single crystal that causes birefringence of incoming rays, has a refractive index difference of 0.02 or more for ordinary and extraordinary rays, and satisfies one of: <DF NUM="(1)">10 DEG < &thetas; < 30 DEG </DF> <DF NUM="(2)">60 DEG < &thetas; < 80 DEG </DF> where &thetas; is the angle the optic axis of the birefringence plate makes with the normal to the surface of the birefringence plate. <IMAGE></p> |
