Diffraction type optical element and optical pickup using this diffraction type optical element

TL;DR: In this article, the problem of providing an optical element capable of taking out diffracted light beams in accordance with the pattern of a diffraction optical element outside a substrate even when the pattern pitch of the patter of the diffraction optic element is less than the wavelength of incident light is solved.

Abstract: PROBLEM TO BE SOLVED: To provide an optical element capable of taking out diffracted light beams in accordance with the pattern of a diffraction optical element outside a substrate even when the pattern pitch of the patter of the diffraction optical element is less than the wavelength of incident light. SOLUTION: The first pattern 4 of the diffraction optical element which has the pattern pitch less than the wave length of the incident light is formed on one part of the main surface 2 of the substrate 1 made of glass, etc., and polarization is imparted thereto. On the other hand, second patterns 5, 6 of the diffraction optical element are disposed on the parts which are respectively irradiated with +1st diffracted light beams and -1st diffracted light beams which are diffracted by the first pattern 4 of the diffraction optical elements on the main surface 3 of the substrate 1. The -1st diffracted light beams L22, L32 which are respectively refracted on the second patterns 5, 6 of the diffraction optical element are made incident to the boundary surface of the main surface 2 with an angle smaller than the critical angle of total reflection and are taken outside the substrate 1.