Patent ID: 7567382

Claim:
An optical filter for varying the optical characteristics of a ray transmitted by an optically anisotropic crystal plate, wherein at least one optically anisotropic crystal plate and at least one substrate are stuck together in a state in which a principal face of the optically anisotropic crystal plate and a principal face of the substrate are perpendicular to the direction of transmission of the ray, the optically anisotropic crystal plate or the substrate is used as an end face on a ray incident side, and another optically anisotropic crystal plate or another substrate that is thinner than the optically anisotropic crystal plate or the substrate that is the end face on the ray incident side is stuck onto the optically anisotropic crystal plate or the substrate, the optically anisotropic crystal plate and the substrate are stuck together with a UV adhesive, the thickness of the UV adhesive is no more than 1/20 the thickness of at least one of the optically anisotropic crystal plate and the substrate, and the optically anisotropic crystal plate and the substrate are respectively set to the thickness of at least 100 μm.