Diffraction device

Abstract

To provide a diffraction element having no wavelength dependency without using a special liquid crystal. In the diffraction element 1 for diffracting incident light, a plurality of first and second phase difference regions 10 and 20 for diffracting incident light are alternately arranged to form a diffraction pattern on a transparent substrate 30. A plurality of fine projecting and recessed structures are arranged in the first and the second phase difference regions 10 and 20 in nano order at a pitch interval shorter than the shortest wavelength of a plurality of wavelength regions for making phase differences of a plurality of wavelengths of incident light even. The fine projecting and recessed structures of the first phase difference region 10 and the fine projecting and recessed structures of the second phase difference region 20 are orthogonal to each other. Phase differences are made even by the fine projecting and recessed structures in the nano order and a diffraction function having diffraction efficiency nearly free from wavelength dependency can be exhibited by the diffraction pattern.

Description

technical field [0001] The present invention relates to a diffraction element that diffracts incident light, and particularly to a diffraction element that is less dependent on wavelength. Background technique [0002] Among the optical elements, there is a diffraction element that diffracts incident light, and the diffraction element can be used, for example, in an optical pickup or the like. The optical pickup can use the light emitted by the light source not only as an optical signal but also as a focus error detection signal and a tracking error detection signal. In this way, the diffraction element diffracts the signal light as 0th-order light, and diffracts the focus error detection signal and tracking error detection signal as ±1st-order light among incident light. For this reason, the diffraction element adopts a structure in which a concave-convex structure is formed on a glass substrate at the micron level. [0003] However, optical pickups in recent years are be...

AI Technical Summary

Problems solved by technology

That is to say, if such adjustment items are not fully performed, the diffraction efficiency will fluctuate

On the contrary, if the strictness of various adjustment items is pursued, the production of diffraction elements will be extremely difficult, and the production cost will become a big problem.

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