Patent ID: 9612449
Date: 2017-04-04
CPC Classifications: G02B

Claim:
1. An axially symmetric polarization conversion element that converts incident light into an axially symmetric polarized beam, the axially symmetric polarization conversion element having a shape obtained by rotating a cross section of a Fresnel rhomb wave plate along a direction of an optical axis around an axis that is parallel to the optical axis, the axially symmetric polarization conversion element converting the incident light into the axially symmetric polarized beam by utilizing N number of Fresnel reflections, wherein N is a positive integer, the axially symmetric polarization conversion element having an outer circumferential surface that corresponds to a slope of a truncated conical shape, and an inner circumferential surface that corresponds to a slope of an inverted conical shape that is present inside the truncated conical shape, and reflecting an linearly polarized Gaussian beam incident on a vertex of the inverted conical shape by the inner circumferential surface and the outer circumferential surface to emit a ring-shaped axially symmetric polarized beam, and the axially symmetric polarized beam is in a ring shape having linearly polarized light at 90 degree intervals and circularly polarized light at 90 degree intervals, and each linearly polarized light is spaced apart from each circularly polarized light by 45 degrees.