Patent ID: 8284488
Filing Date: 2012-10-09
Classification: G02B,G03B

Abstract:
1. A low pass filter which separates incident light into four light beams of two light beams composed of a component in an A polarization direction, and two light beams composed of a component in a B polarization direction orthogonal to the A polarization direction, comprising: a first optical path separation birefringent plate for separating the components in the two polarization direction in a first separation direction; a wave plate; and a second optical path separation birefringent plate for performing separation in a second separation direction intersecting the first separation direction for each of the components in the two polarization directions which are disposed therein in an order of incidence of the light, wherein the wave plate includes at least one phase plate for changing a polarization state of the incident light, when the wave plate is constituted of one phase plate, an optic axis of the one phase plate is so disposed as to intersect both of the A polarization direction and the B polarization direction, when the wave plate is constituted of two or more phase plates, the respective optic axes of at least two of the phase plates are so disposed as to intersect each other and intersect both of the A polarization direction and the B polarization direction, and when a light quantity of light having passed through the wave plate in the A polarization direction with respect to a total light quantity of light of a given wavelength out of light having passed through the wave plate is assumed to be I wherein the light having passed through the wave plate is a linearly polarized light or an elliptically polarized light.