Diffraction grating lens and imaging device using same

Abstract

A diffraction grating lens according to the present invention is a diffraction grating lens 11 including: a lens body 12; and a plurality of diffraction steps relative to a base shape and a plurality of diffraction gratings 13 interposed between the diffraction steps, provided on a surface of the lens body 12. The lens body 12 is made of a first material having a refractive index n1(λ) at a used wavelength λ; the diffraction grating 13 is in contact with air; and the relationship of an inequality below is satisfied, where d is a design step length of the diffraction steps, and m is an order of diffraction. Each of the plurality of annular zones includes an intermediate portion and a pair of end portions sandwiching the intermediate portion along a radial direction, and in at least one of the plurality of annular zones, either one of a recess 18 and a protrusion 19 is provided in at least a portion of one of the pair of end portions, and the other one of the recess 18 and the protrusion 19 is provided in at least a portion of the other of the pair of end portions. Between two kinds of diffraction steps 17A and 17B of the diffraction grating 13, one is provided at a position where the phase difference from the base shape given the design wavelength λ0 is not 2 nmπ. 0.9  d ≤ m · λ n 1  ( λ ) - 1 ≤ 1.1  d

Description

technical field [0001] The present invention relates to a diffraction grating lens (diffraction optical element) for converging or diverging light by using a diffraction phenomenon, and an imaging device using the diffraction grating lens. Background technique [0002] A diffraction grating lens provided with a diffraction grating on the lens surface is excellent in correcting lens aberrations such as curvature of field and chromatic aberration (deviation of imaging points that vary with wavelength). This is because the diffraction grating has special properties such as inverse scattering and anomalous scattering, and has a large chromatic aberration correction capability. When a diffraction grating is used in the imaging optical system, the same performance can be realized with a smaller number of lenses than in an imaging optical system using only aspheric lenses. Therefore, there is an advantage that the optical length can be shortened while the manufacturing cost can be...

AI Technical Summary

Problems solved by technology

For example, when the wavelength that determines the step height d is set to the wavelength of green light (for example, 540 nm), the first-order diffraction efficiency of the green light wavelength is 100%, and unnecessary order diffraction light of the green light wavelength will not be generated. 156, but at the wavelength of red light (such as 640nm) or blue light wavelength (such as 440nm), the 1st diffraction efficiency is less than 100%, which will produce red 0th diffraction light or blue 2nd diffraction light

These red 0-order diffracted lights or blue 2-order diffracted lights are useless order diffracted lights 156, which become flares or ghosts and diffuse onto the image plane, deteriorating the image and lowering the MTF (Modulation Transfer Function: modulation transfer function) characteristics

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