DIFFRACTION OPTICAL ELEMENT, DESIGN METHOD OF DIFFRACTION OPTICAL ELEMENT

• Main Authors: TOYAMA NOBUTO, ADACHI TAKASHI, INAZUKI YUICHI
• Format: Patent
• Language: English; Japanese
• Published: 20.05.2021
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

To provide a diffraction optical element capable of suppressing reduction in diffraction efficiency of high order diffraction light even when the high order diffraction light is diffracted at high angle to suppress zero-order light, and a design method of the diffraction optical element.SOLUTION: A diffraction optical element 10 has a diffraction grating which has a pattern in which when viewed from a normal direction of a surface on which a rugged shape is formed comprising a high refractive index part including a protrusion 11, and a low refractive index part including a recess 12 having lower refractive index than the protrusion 11, a boundary between the protrusion 11 and the recess 12 includes at least one of a curve and a polygonal line connecting a plurality of lines. When the height of the protrusion 11 is denoted by H, the width of the protrusion 11 by WP, an aspect ratio of the protrusion 11 by arP=H/WP, the relation of 3.8<arP<5.6 is satisfied, and when the width of the recess 12 is denoted by WN, and the aspect ratio of the recess 12 by arN=H/WN, the relation of 2.2<arN<3.1 is satisfied.SELECTED DRAWING: Figure 1 【課題】高次回折光を高角度に回折させて０次光を低く抑える場合であっても、高次回折光の回折効率の低下を抑えることができる回折光学素子、回折光学素子の設計方法を提供する。【解決手段】回折光学素子１０は、凸部１１を有する高屈折率部と、凸部１１よりも屈折率が低い凹部１２を有する低屈折率部とを備える凹凸形状が形成された面の法線方向から見て凸部１１と凹部１２との境界が曲線と複数の線分を繋げた折れ線との少なくとも一方を含むパターンを有する回折格子を有する回折光学素子１０であって、凸部１１の高さをＨとし、凸部１１の幅をＷＰとし、凸部１１のアスペクト比をａｒＰ＝Ｈ／ＷＰとすると、３．８＜ａｒＰ＜５．６の関係を満たし、かつ、凹部１２の幅をＷＮとし、凹部１２のアスペクト比をａｒＮ＝Ｈ／ＷＮとすると、２．２＜ａｒＮ＜３．１の関係を満たす。【選択図】図１