Patent ID: 8531769
Filing Date: 2013-09-10
Classification: G02B

Abstract:
1. A dispersion element comprising: a prism having a first transmission surface and an oppositely disposed second transmission surface; and an optical element having a third transmission surface and an oppositely disposed diffraction optical surface on which a diffraction grating is arranged, wherein the prism and the optical element are integrated into one body by cementing the first transmission surface to the third transmission surface, and the third transmission surface and the diffraction optical surface are non-parallel to each other in a plane perpendicular to grooves of the diffraction grating, wherein an angle Δθ between the third transmission surface and the diffraction optical surface satisfies Expression (1): λ/(nW)<Δθ<α(1) where, λ is wavelength in use, n is a refractive index of a medium of the optical element, W is an effective length in a direction perpendicular to the grooves on the diffraction optical surface, and α is an apex angle of the prism.