JP2015011293A - Method for manufacturing diffraction optical element - Google Patents
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Abstract
Description
本発明は、回折光学素子の製造方法に関する。 The present invention relates to a method for manufacturing a diffractive optical element.
ブレーズ構造の回折光学素子は特定の一つの次数（以下、「特定次数」又は「設計次数」とも言う）と特定の波長に対して高い効率で光を回折することができる。特許文献１は、２つの回折格子を密着配置し、各回折格子を構成する材料に低屈折率高分散材料と高屈折率低分散材料を用い、回折格子の高さを適切に設定した（以下、このような回折光学素子を「密着２層ＤＯＥ」という）構成を開示している。特許文献２は、可視波長域全域で９９％以上の高い回折効率を得るために部分分散比θｇＦが通常の材料より小さな値（リニア異常分散性）を有する材料を用いることを開示している。 The blazed diffractive optical element can diffract light with high efficiency with respect to a specific one order (hereinafter also referred to as “specific order” or “design order”) and a specific wavelength. In Patent Document 1, two diffraction gratings are arranged in close contact, a low refractive index high dispersion material and a high refractive index low dispersion material are used as materials constituting each diffraction grating, and the height of the diffraction grating is appropriately set (hereinafter referred to as the diffraction grating height). Such a diffractive optical element is referred to as a “close-contact two-layer DOE”. Patent Document 2 discloses using a material having a partial dispersion ratio θgF smaller than that of a normal material (linear anomalous dispersion) in order to obtain a high diffraction efficiency of 99% or more in the entire visible wavelength range.
また、特許文献３は、保護膜を形成したときに発生する設計形状からのずれを相殺する変形を、予め回折光学素子を成形する金型に与える方法を提案している。特許文献４は、回折光学素子に蒸着する反射防止膜の膜厚が不均一になることを防止するために、金型に反射防止膜の膜厚の変化を相殺する変形を与える方法を提案している。特許文献５は、回折格子表面にパッドで光学調整層を設ける場合に、硬化収縮による表面の変形を中心の輪帯ピッチを変えることで抑制する方法を提案している。 Further, Patent Document 3 proposes a method in which a deformation that cancels a deviation from a design shape that occurs when a protective film is formed is applied to a mold that molds a diffractive optical element in advance. Patent Document 4 proposes a method of giving a mold a deformation that offsets the change in the thickness of the antireflection film in order to prevent the thickness of the antireflection film deposited on the diffractive optical element from becoming uneven. ing. Patent Document 5 proposes a method of suppressing surface deformation due to curing shrinkage by changing the center annular zone pitch when an optical adjustment layer is provided with a pad on the surface of the diffraction grating.
２つのレンズの間に密着２層ＤＯＥを形成する際に、回折効率を高めるためにベースの樹脂材料に無機微粒子を使用し、成形によって製造することが考えられるが、成形時に、樹脂の硬化収縮によるレンズ表面が変形し、光学性能が低下する。これに対して、特許文献３〜４は、いずれも回折光学素子が樹脂を硬化して作成される場合の樹脂の硬化収縮に起因するレンズ面の変形を効果的に抑制することができなかった。 When forming a close-contact two-layer DOE between two lenses, it is conceivable to use inorganic fine particles as the base resin material to increase diffraction efficiency, and to manufacture it by molding. The lens surface is deformed and the optical performance is deteriorated. On the other hand, Patent Documents 3 to 4 cannot effectively suppress the deformation of the lens surface due to the curing shrinkage of the resin when the diffractive optical element is formed by curing the resin. .
本発明は、回折光学素子が樹脂を硬化して作成される場合の樹脂の硬化収縮に起因するレンズ面の変形を低減することが可能な回折光学素子の製造方法を提供することを例示的な目的とする。 The present invention provides an exemplary method for manufacturing a diffractive optical element capable of reducing deformation of a lens surface caused by curing shrinkage of a resin when the diffractive optical element is formed by curing a resin. Objective.
本発明の回折光学素子の製造方法は、第１のレンズと第２のレンズの間に設けられ、複数の回折格子が密着配置された回折光学素子を形成する回折光学素子の製造方法であって、前記複数の回折格子は、前記第１のレンズに最も近い、第１の樹脂材料から構成される第１の回折格子と、前記第２のレンズに最も近い、第２の樹脂材料から構成される第２の回折格子を含み、前記第１のレンズの上に金型を配置して前記第１のレンズと前記金型の間に前記第１の樹脂材料を充填し、前記第１の樹脂材料を硬化し、前記第１の回折格子を前記第１のレンズの上に形成するステップと、前記複数の回折格子の中で前記第２の回折格子よりも前記第１のレンズ側にある回折格子と前記第２のレンズの間に前記第２の樹脂材料を充填し、前記第２の樹脂材料を硬化し、前記第２の回折格子を形成するステップと、を有し、前記第１の回折格子の格子頂点が形成する第１の面は非球面の部分を有し、前記非球面の部分は前記第２のレンズの回折光学素子側の面とは異なる形状を有し、前記第１のレンズの光軸付近に前記第２のレンズ側に凸面を有することを特徴とする。 The method of manufacturing a diffractive optical element according to the present invention is a method of manufacturing a diffractive optical element that is provided between a first lens and a second lens and forms a diffractive optical element in which a plurality of diffraction gratings are closely arranged. The plurality of diffraction gratings are composed of a first diffraction grating composed of a first resin material closest to the first lens and a second resin material closest to the second lens. The first resin material is disposed between the first lens and the mold, and the first resin material is filled between the first lens and the mold. Curing the material, forming the first diffraction grating on the first lens, and diffracting the plurality of diffraction gratings closer to the first lens than the second diffraction grating. The second resin material is filled between the grating and the second lens, and the second resin Curing the material to form the second diffraction grating, wherein the first surface formed by the grating vertex of the first diffraction grating has an aspherical portion, The portion has a shape different from the surface of the second lens on the diffractive optical element side, and has a convex surface near the optical axis of the first lens on the second lens side.
本発明によれば、回折光学素子が樹脂を硬化して作成される場合の樹脂の硬化収縮に起因するレンズ面の変形を低減することが可能な回折光学素子の製造方法を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the diffractive optical element which can reduce the deformation | transformation of the lens surface resulting from the hardening shrinkage | contraction of resin when a diffractive optical element is produced by hardening | curing resin can be provided. .
図６（ａ）は、本実施形態の光学機器の一例である一眼レフカメラシステムの断面図である。本発明の光学機器は、デジタルスチルカメラ、デジタルビデオカメラ、ミラーレスカメラ、双眼鏡、プロジェクタなどに適用することができる。 FIG. 6A is a cross-sectional view of a single-lens reflex camera system which is an example of the optical apparatus of the present embodiment. The optical apparatus of the present invention can be applied to digital still cameras, digital video cameras, mirrorless cameras, binoculars, projectors, and the like.
図６（ａ）において、２１０はカメラ本体（撮像装置）、２１１はカメラ本体２１０に着脱可能に装着される交換レンズ（光学機器）である。２１２は交換レンズ２１１を通して得られる被写体像を記録するフィルムや撮像素子等の感光体である。２１３は交換レンズ２１１からの被写体像を観察するファインダー光学系である。２１４は矢印に示すように光路に進退可能なクイックリターンミラーである。 In FIG. 6A, reference numeral 210 denotes a camera body (imaging device), and 211 denotes an interchangeable lens (optical device) that is detachably attached to the camera body 210. Reference numeral 212 denotes a photoconductor such as a film or an image sensor for recording a subject image obtained through the interchangeable lens 211. Reference numeral 213 denotes a viewfinder optical system for observing a subject image from the interchangeable lens 211. Reference numeral 214 denotes a quick return mirror that can advance and retract in the optical path as indicated by an arrow.
ファインダーで被写体像を観察する場合は、クイックリターンミラー２１４を光路中に配置してピント板２１５に結像した被写体像をペンタプリズム２１６で正立像とした後、接眼光学系２１７で拡大して観察する。撮影時には、クイックリターンミラー２１４を矢印方向に回動して光路から退避させて被写体像を感光体２１２に結像する。 When observing the subject image with the viewfinder, the quick return mirror 214 is arranged in the optical path, and the subject image formed on the focus plate 215 is made into an erect image with the pentaprism 216, and then magnified with the eyepiece optical system 217 for observation. To do. At the time of shooting, the quick return mirror 214 is rotated in the direction of the arrow and retracted from the optical path to form a subject image on the photosensitive member 212.
図６（ｂ）は、交換レンズ２１１に設けられた、被写体像を形成する撮影光学系の光路図である。本実施形態の撮影光学系を使用することによって色収差を抑え、高い光学性能を有した一眼レフカメラシステムを提供することができる。図６（ｂ）において、１１は回折光学素子（ＤＯＥ）、１２は絞り、１３は像面、１４は最大画角の光束、１５は撮像光学系の光軸を示している。 FIG. 6B is an optical path diagram of a photographing optical system that is provided on the interchangeable lens 211 and forms a subject image. By using the photographing optical system of the present embodiment, it is possible to provide a single lens reflex camera system that suppresses chromatic aberration and has high optical performance. In FIG. 6B, 11 is a diffractive optical element (DOE), 12 is a stop, 13 is an image plane, 14 is a light beam having a maximum angle of view, and 15 is an optical axis of the imaging optical system.
望遠レンズのように第１群レンズが正のパワーを有する場合には、ＤＯＥはできるだけ物体側で使用した方が倍率色収差の補正に効果がある。図６（ｂ）に示す撮影光学系は、正の屈折力の第１群レンズＢ１、負の屈折率の第２群レンズＢ２、正の屈折率の第３群レンズＢ３を有し、最も倍率色収差の補正に効果がある第１レンズと第２レンズの間にＤＯＥ１１が設けられている。ＤＯＥ１１は、正のパワーを有する位相を付加するように格子中央から外側にかけて格子ピッチが狭くなっており、撮影光学系の色収差を改善している。 When the first lens group has a positive power like a telephoto lens, it is more effective to correct the lateral chromatic aberration when the DOE is used on the object side as much as possible. The imaging optical system shown in FIG. 6B includes a first lens unit B1 having a positive refractive power, a second lens unit B2 having a negative refractive index, and a third lens unit B3 having a positive refractive index. A DOE 11 is provided between the first lens and the second lens that are effective in correcting chromatic aberration. The DOE 11 has a narrow grating pitch from the center of the grating to the outside so as to add a phase having a positive power, thereby improving the chromatic aberration of the photographing optical system.
ＤＯＥは、ベースの形状に位相差関数で定義される位相項を付加した形状となっている。ベースの形状は、レンズ表面の形状であり、球面形状や非球面形状、平面形状であったりする。回折レンズ構造による光路長の付加量は、光軸からの高さｈ、ｎ次（偶数次）の位相差関数係数Ｃｎ、波長λを用いて、次式で定義される位相差関数φ（ｈ）により表される。 The DOE has a shape obtained by adding a phase term defined by a phase difference function to the shape of the base. The shape of the base is the shape of the lens surface, and may be a spherical shape, an aspherical shape, or a planar shape. The added amount of the optical path length by the diffractive lens structure is obtained by using the height h from the optical axis, the nth order (even order) phase difference function coefficient Cn, and the wavelength λ, and the phase difference function φ (h ).
φ（ｈ）＝（Ｃ２ｈ２＋Ｃ４ｈ４＋Ｃ６ｈ６＋…）×２π／λ ・・・（１）
曲率がＲのレンズ表面に位相差関数φ（ｈ）にて格子形状を付加する場合、光軸方向の位置をｘ、ｋを中心の輪帯を１輪帯として中心から数えた輪帯番号、ｄ０を格子高さとした時、次式で表される形状とする。
φ (h) = (C2h 2 + C4h 4 + C6h 6 +...) × 2π / λ (1)
When a lattice shape is added to the lens surface having a curvature R by the phase difference function φ (h), the zone number counted from the center with the ring zone centered on x and k as the center in the optical axis direction, When d0 is the lattice height, the shape is expressed by the following formula.
数式（２）において、最初の２項はベース形状を示しており、第３項は位相差関数で位相項を付加した形状を示している。また、第２項については輪帯番号が変わる部分でｘの位置が不連続となっており、これにより格子形状が生じる。 In the formula (2), the first two terms indicate a base shape, and the third term indicates a shape with a phase term added by a phase difference function. In the second term, the position of x is discontinuous at the portion where the ring number changes, and this causes a lattice shape.
ＤＯＥを光学系中に用いるときには使用波長域全域において設計次数の光線の回折効率が十分高いことが必要になる。回折効率が低いと、設計次数以外の回折次数をもった光線が多く存在することになり、これらの光線は、設計次数の光線とは別な所に結像してフレア光となる。 When DOE is used in an optical system, it is necessary that the diffraction efficiency of a light beam of the designed order is sufficiently high over the entire wavelength range used. When the diffraction efficiency is low, there are many light rays having diffraction orders other than the design order, and these light rays are imaged at a place different from the light of the design order and become flare light.
図７（ａ）、（ｂ）は従来のＤＯＥ１００の平面図と断面図であり、図７（ｃ）は別の従来のＤＯＥの部分拡大断面図である。ＯＡは光軸である。図７（ａ）において、１０１は回折格子の輪帯であり、格子の間隔（ピッチ）を変えることで光学的なパワーを与えることができる。図７（ｂ）、図７（ｃ）は光軸を含む断面図である。 7A and 7B are a plan view and a sectional view of a conventional DOE 100, and FIG. 7C is a partially enlarged sectional view of another conventional DOE. OA is the optical axis. In FIG. 7A, reference numeral 101 denotes a ring zone of the diffraction grating, and optical power can be given by changing the interval (pitch) of the grating. FIGS. 7B and 7C are cross-sectional views including the optical axis.
図７（ｂ）において、ＤＯＥ１００は、第１の回折格子１１０Ａと第２の回折格子１２０Ａを密着して配置しており、広い波長域に対して高い回折効率を得ている。２つのレンズ１３０Ａ、１４０Ａの間に形成される。 In FIG. 7B, the DOE 100 has the first diffraction grating 110A and the second diffraction grating 120A in close contact with each other, and obtains high diffraction efficiency over a wide wavelength range. It is formed between the two lenses 130A and 140A.
図７（ｃ）において、ＤＯＥ１００は、第１の回折格子１１０Ｂと第２の回折格子１２０Ｂを密着して配置しており、広い波長域に対して高い回折効率を得ている。第１のレンズ１３０Ｂと第２のレンズ１４０Ｂの間に形成される。 In FIG.7 (c), DOE100 has arrange | positioned the 1st diffraction grating 110B and the 2nd diffraction grating 120B closely_contact | adhering, and has acquired high diffraction efficiency with respect to a wide wavelength range. It is formed between the first lens 130B and the second lens 140B.
図７（ｂ）において、第１の回折格子１１０Ａの格子頂点が形成する第１の面１１２Ａと、第２の回折格子１２０Ａの格子頂点が形成する第２の面１２２Ａを、以下「包絡線」と呼ぶ場合がある。同様に、図７（ｃ）において、第１の回折格子１１０Ｂの格子頂点が形成する第１の面１１２Ｂと、第２の回折格子１２０Ｂの格子頂点が形成する第２の面１２２Ｂを、以下「包絡線」と呼ぶ場合がある。 In FIG. 7B, the first surface 112A formed by the grating vertex of the first diffraction grating 110A and the second surface 122A formed by the grating vertex of the second diffraction grating 120A are hereinafter referred to as an “envelope”. Sometimes called. Similarly, in FIG. 7C, the first surface 112B formed by the grating vertex of the first diffraction grating 110B and the second surface 122B formed by the grating vertex of the second diffraction grating 120B are referred to as “ Sometimes called an “envelope”.
図７（ｂ）に示すように、第１の面１１２Ａは第２のレンズ１４０ＡのＤＯＥ１００側の面１４２Ａと同一の（曲面）形状であり、第２の面１２２Ａは第１のレンズ１３０ＡのＤＯＥ１００側の面１３２Ａと同一の（曲面）形状である。同様に、図７（ｃ）に示すように、第１の面１１２Ｂは第２のレンズ１４０ＡのＤＯＥ１００側の面１４２Ａと同一の（平面）形状であり、第２の面１２２Ａは第１のレンズ１３０ＡのＤＯＥ１００側の面１３２Ａと同一の（平面）形状である。 As shown in FIG. 7B, the first surface 112A has the same (curved surface) shape as the surface 142A on the DOE 100 side of the second lens 140A, and the second surface 122A has the DOE 100 of the first lens 130A. It has the same (curved surface) shape as the side surface 132A. Similarly, as shown in FIG. 7C, the first surface 112B has the same (planar) shape as the surface 142A on the DOE 100 side of the second lens 140A, and the second surface 122A is the first lens. It has the same (planar) shape as the surface 132A on the DOE 100 side of 130A.
図７（ｃ）に示すように、２種類の異なる材料からなる回折格子を密着配置したＤＯＥにおいて波長λの光の回折効率を最大とする条件は、次式で表すように、回折格子を通過する光の光路長を波長の整数倍とすることである。 As shown in FIG. 7C, the condition for maximizing the diffraction efficiency of light of wavelength λ in a DOE in which diffraction gratings made of two different materials are closely arranged passes through the diffraction grating as represented by the following equation. The optical path length of the light to be made is an integral multiple of the wavelength.
（ｎ２−ｎ１）ｄ０＝ｍ×λ ・・・（３）
ここで、ｎ１と、ｎ２はそれぞれ、第１の回折格子、第２の回折格子の材料の波長λ０の光に対する屈折率で、ｎ１＜ｎ２とする。また、ｄ０（＞０）は格子厚、ｍは回折次数である。
(N2-n1) d0 = m × λ (3)
Here, n1 and n2 are refractive indexes with respect to light of wavelength λ0 of the materials of the first diffraction grating and the second diffraction grating, and n1 <n2. D0 (> 0) is the grating thickness, and m is the diffraction order.
数式（３）は波長の項を含むが、広い波長域で高い回折効率を得るためには、ＤＯＥが使用される各波長における屈折率が数式（３）を満たすことが好ましい。例えば、可視域の広い波長範囲で高い回折効率を得るためには、ｄ線だけでなく、Ｆ線やＣ線等の波長においても、数式（３）を満たす必要がある。 Formula (3) includes a wavelength term, but in order to obtain high diffraction efficiency in a wide wavelength range, it is preferable that the refractive index at each wavelength in which DOE is used satisfy Formula (3). For example, in order to obtain high diffraction efficiency in a wide wavelength range in the visible range, it is necessary to satisfy Equation (3) not only for d-line but also for wavelengths such as F-line and C-line.
ここで、ｎ１ｄ、ｎ１Ｆ、ｎ１Ｃをそれぞれ第１の回折格子の材料の、ｄ線、Ｆ線、Ｃ線の波長における屈折率、ｎ２ｄ、ｎ２Ｆ、ｎ２Ｃをそれぞれ第２の回折格子の材料の、ｄ線、Ｆ線、Ｃ線の波長における屈折率とし、ΔｎとΔｎＦＣを次のように定義する。
Δｎ＝（ｎ２ｄ−ｎ１ｄ） ・・・（４）
ΔｎＦＣ＝｛（ｎ２Ｆ−ｎ２Ｃ）−（ｎ１Ｆ−ｎ１Ｃ）｝ ・・・（５）
すると、ｄ線、Ｆ線、Ｃ線において１００％の回折効率を得る条件は次式のようになり、２つの材料の屈折率差と、分散の差が一定の値をとることが分かる。
Here, n1d, n1F, and n1C are refractive indexes of the first diffraction grating material, d-line, F-line, and C-line, respectively, and n2d, n2F, and n2C are the second diffraction grating material. The refractive indexes at the wavelengths of the line, the F line, and the C line are defined, and Δn and ΔnFC are defined as follows.
Δn = (n2d−n1d) (4)
ΔnFC = {(n2F−n2C) − (n1F−n1C)} (5)
Then, the conditions for obtaining 100% diffraction efficiency for the d-line, F-line, and C-line are as follows, and it can be seen that the difference in refractive index between the two materials and the difference in dispersion take constant values.
Δｎ／ΔｎＦＣ＝−３．４５ ・・・（６）
数式（６）の値が負であることから、回折格子を形成する材料は、高屈折率低分散材料と低屈折率高分散材料の組合せが好ましいことが分かる。このタイプのＤＯＥにおいて、９８％以上の高い回折効率は可視の波長域全域にて確保するためには、低屈折率高分散材料についてθｇＦを通常の材料より小さな値（リニア異常分散性）とする方が有利である。このような材料への要求を達成するためにベースの樹脂材料に無機微粒子を用いてもよい。
Δn / ΔnFC = −3.45 (6)
Since the value of Formula (6) is negative, it can be seen that the material forming the diffraction grating is preferably a combination of a high refractive index low dispersion material and a low refractive index high dispersion material. In this type of DOE, in order to ensure a high diffraction efficiency of 98% or more in the entire visible wavelength range, θgF is set to a smaller value (linear anomalous dispersion) than a normal material for a low refractive index and high dispersion material. Is more advantageous. In order to achieve the requirement for such a material, inorganic fine particles may be used in the base resin material.
一方、各回折格子を作成する方法としては、格子形状を切削等によって型に作成し、ＵＶ硬化や熱硬化、射出成形などの成形プロセスによって樹脂に形状を転写する方法が採用されている。図８（ａ）~（ｄ）は、このＤＯＥの製造方法を示す断面図である。図８（ｅ）はＤＯＥの製造方法を説明するフローチャートであり、「Ｓ」はステップを表している。 On the other hand, as a method for creating each diffraction grating, a method is employed in which a grating shape is created in a mold by cutting or the like, and the shape is transferred to a resin by a molding process such as UV curing, thermosetting, or injection molding. 8A to 8D are cross-sectional views showing a method for manufacturing this DOE. FIG. 8E is a flowchart for explaining a method of manufacturing a DOE, and “S” represents a step.
図８（ａ）おいて、内面に第１の回折格子の形状が切削等によって作成された金型９１と第１のレンズ９３との間に未硬化の紫外線硬化樹脂（第１の樹脂材料）９２が充填され（Ｓ１０）、紫外線ＵＶが第１のレンズを介して紫外線硬化樹脂９２に照射される。これにより、紫外線硬化樹脂９２が硬化して、第１の回折格子９４が第１のレンズ９３の上に形成される（Ｓ１２）。次に、図８（ｂ）に示すように、金型９１を離型する（Ｓ１４）。次に、図８（ｃ）に示すように、ディスペンサー９５から紫外線硬化樹脂９２とは異なる紫外線硬化樹脂（第２の樹脂材料）９６を第１の回折格子９４の表面に滴下する（Ｓ１６）。次に、図８（ｄ）に示すように、第２のレンズ９８を紫外線硬化樹脂９６の上に配置し（Ｓ１８）、紫外線ＵＶを照射することによって紫外線硬化樹脂９６を硬化し（Ｓ２０）、第２の回折格子９７を形成する。第１の回折格子９４と第２の回折格子９７によってＤＯＥが完成する。 In FIG. 8A, an uncured ultraviolet curable resin (first resin material) is formed between a mold 91 and a first lens 93 whose first diffraction grating is formed on the inner surface by cutting or the like. 92 is filled (S10), and the ultraviolet curable resin 92 is irradiated with ultraviolet rays UV through the first lens. Thereby, the ultraviolet curable resin 92 is cured, and the first diffraction grating 94 is formed on the first lens 93 (S12). Next, as shown in FIG. 8B, the mold 91 is released (S14). Next, as shown in FIG. 8C, an ultraviolet curable resin (second resin material) 96 different from the ultraviolet curable resin 92 is dropped from the dispenser 95 onto the surface of the first diffraction grating 94 (S16). Next, as shown in FIG. 8D, the second lens 98 is placed on the ultraviolet curable resin 96 (S18), and the ultraviolet curable resin 96 is cured by irradiating with ultraviolet UV (S20). A second diffraction grating 97 is formed. The DOE is completed by the first diffraction grating 94 and the second diffraction grating 97.
図７（ｄ）は、図７（ｂ）のＤＯＥ１００において硬化収縮によるレンズ表面の変形を示す断面図である。同図において、第１の回折格子１１０Ａは、例えば、低屈折率高分散の紫外線硬化樹脂、第２の回折格子１２０Ａは、例えば、高屈折率低分散の紫外線硬化樹脂から構成されている。ＤＯＥ１００のパワーは正であり、回折格子の格子と格子の間隔である格子ピッチは光軸ＯＡからレンズの周辺にいくに従って狭くなっている。図８に示す成形プロセスによりＤＯＥ１００を作製すると、第１のレンズ１３０Ａの上に第１の回折格子１１０Ａが形成され、その上に第２の回折格子１２０Ａの樹脂が塗付され第２のレンズ１４０Ａが配置されて硬化される。この時、第２の回折格子１２０Ａの樹脂が硬化収縮することで応力が発生し、第２のレンズ１４０Ａの外側の面１４４Ａが破線１４６で示すように変形する。特に、格子ピッチの広い、光軸付近は樹脂量が多くなるために硬化収縮による大きな応力が発生し易く、レンズ表面の変形も破線で示したようにレンズの光軸付近の変形が大きくなる。 FIG.7 (d) is sectional drawing which shows a deformation | transformation of the lens surface by hardening shrinkage | contraction in DOE100 of FIG.7 (b). In the drawing, the first diffraction grating 110A is made of, for example, a low refractive index and high dispersion ultraviolet curable resin, and the second diffraction grating 120A is made of, for example, a high refractive index and low dispersion ultraviolet curable resin. The power of the DOE 100 is positive, and the grating pitch, which is the distance between the gratings of the diffraction grating, becomes narrower from the optical axis OA to the periphery of the lens. When the DOE 100 is manufactured by the molding process shown in FIG. 8, the first diffraction grating 110A is formed on the first lens 130A, and the resin of the second diffraction grating 120A is applied thereon to form the second lens 140A. Is placed and cured. At this time, stress is generated by the resin of the second diffraction grating 120A being cured and contracted, and the outer surface 144A of the second lens 140A is deformed as indicated by a broken line 146. In particular, since the amount of resin increases in the vicinity of the optical axis with a wide lattice pitch, a large stress is likely to occur due to curing shrinkage, and the deformation of the lens surface also increases near the optical axis of the lens as indicated by the broken line.
図１は、実施例１のＤＯＥ１１の断面図である。同図において、ＯＡは光軸、３０Ａは第１のレンズ、４０Ａは第２のレンズである。第１のレンズ３０Ａは凸メニスカスレンズであり、第１のレンズ３０ＡのＤＯＥ１１側の面３２Ａは凹面である。第２のレンズは正のパワーを有する凸レンズであり、第２のレンズ４０ＡのＤＯＥ１１側の面４２Ａは凸面である。 FIG. 1 is a cross-sectional view of the DOE 11 according to the first embodiment. In the figure, OA is an optical axis, 30A is a first lens, and 40A is a second lens. The first lens 30A is a convex meniscus lens, and the surface 32A on the DOE 11 side of the first lens 30A is a concave surface. The second lens is a convex lens having positive power, and the surface 42A on the DOE 11 side of the second lens 40A is a convex surface.
２１Ａは低屈折率高分散の紫外線硬化樹脂（第１の樹脂材料）から構成される第１の回折格子、２５Ａは高屈折率低分散の紫外線硬化樹脂（第２の樹脂材料）から構成される第２の回折格子である。第１の回折格子２１Ａの格子頂点が形成する第１の面２２Ａと、第２の回折格子２５Ａの格子頂点が形成する第２の面２６Ａは、図１では共に点線で示された包絡線となっている。点線２３Ａは、本実施例を適用しない場合に第１の回折格子の格子頂点が形成する第１の面であり、第２のレンズ４０ＡのＤＯＥ１１側（回折光学素子側）の面４２Ａと同一形状を有する。ＤＯＥ１１のパワーは正であり、格子ピッチは光軸ＯＡからレンズの周辺に行くに従って狭くなっている。 21A is a first diffraction grating composed of an ultraviolet curable resin (first resin material) with a low refractive index and high dispersion, and 25A is composed of an ultraviolet curable resin (second resin material) with a high refractive index and low dispersion. This is the second diffraction grating. The first surface 22A formed by the grating vertex of the first diffraction grating 21A and the second surface 26A formed by the grating vertex of the second diffraction grating 25A are both envelopes indicated by dotted lines in FIG. It has become. A dotted line 23A is the first surface formed by the grating vertex of the first diffraction grating when this embodiment is not applied, and has the same shape as the surface 42A on the DOE 11 side (diffractive optical element side) of the second lens 40A. Have The power of the DOE 11 is positive, and the grating pitch becomes narrower from the optical axis OA to the periphery of the lens.
第１の回折格子２１Ａの第１の樹脂材料の屈折率をｎｄ１、第２の回折格子２５Ａの第２の樹脂材料の屈折率をｎｄ２、第１の樹脂材料のアッベ数をνｄ１、第２の樹脂材料のアッベ数をνｄ２とすると、次式が成立する。 The refractive index of the first resin material of the first diffraction grating 21A is nd1, the refractive index of the second resin material of the second diffraction grating 25A is nd2, the Abbe number of the first resin material is νd1, and the second When the Abbe number of the resin material is νd2, the following equation is established.
ｎｄ２＞ｎｄ１ （７）
νｄ１＞νｄ２ （８）
図３は、実施例１の回折格子の材料のアッベ数と屈折率を示すグラフであり、横軸はアッベ数、縦軸は屈折率である。高屈折率低分散材料として、アクリル系の紫外線硬化樹脂（ｎｄ＝１．５２、νｄ＝５１）にＺｒＯ２微粒子を９．５ｖｏｌ％混ぜた材料を使用した。微粒子分散後の高屈折率低分散材料の屈折率とアッベ数は、図３の５２に示すように、ｎｄ＝１．５６５，νｄ＝５０．０であった。低屈折率高分散材料として、同じ紫外線硬化樹脂にＩＴＯの微粒子分散濃度を６ｖｏｌ％とした樹脂を使用した。微粒子分散後の低屈折率高分散材料の屈折率とアッベ数は、図３の５１に示すように、ｎｄ＝１．５４４，νｄ＝３１．４であった。ＩＴＯ微粒子を混合することで、材料としてはリニアの異常分散性を有した低アッベ数の材料を提供することができる。これにより格子の厚みは２８．２μｍの時に最も高い回折効率となった。
nd2> nd1 (7)
νd1> νd2 (8)
FIG. 3 is a graph showing the Abbe number and the refractive index of the material of the diffraction grating of Example 1, where the horizontal axis represents the Abbe number and the vertical axis represents the refractive index. As a high refractive index and low dispersion material, a material in which 9.5 vol% of ZrO 2 fine particles were mixed with an acrylic ultraviolet curable resin (nd = 1.52, νd = 51) was used. The refractive index and Abbe number of the high refractive index and low dispersion material after fine particle dispersion were nd = 1.565 and νd = 50.0, as indicated by 52 in FIG. As the low-refractive index high-dispersion material, a resin having an ITO fine particle dispersion concentration of 6 vol% in the same ultraviolet curable resin was used. The refractive index and Abbe number of the low refractive index and high dispersion material after dispersion of the fine particles were nd = 1.544 and νd = 31.4, as indicated by 51 in FIG. By mixing the ITO fine particles, a low Abbe number material having linear anomalous dispersion can be provided. Accordingly, the highest diffraction efficiency was obtained when the thickness of the grating was 28.2 μm.
図２（ａ）は、この時の１次光の回折効率を示し、図２（ｂ）は、０次光（点線）と２次回折光（実線）の回折効率を示す。図２において、横軸は波長（ｎｍ）、縦軸は回折効率（％）である。１次回折光が撮像光学系の結像に使用している回折光であり、図２（ａ）から殆ど１００％の非常に良好な回折効率を全波長域において維持していることがわかる。また、図２（ｂ）から、高輝度光源の周辺に同心円状に発生する不要回折光の原因となる０次光と２次光は共に全波長域で０．０２％以下の非常に小さい値となっていることが分かる。 FIG. 2A shows the diffraction efficiency of the first-order light at this time, and FIG. 2B shows the diffraction efficiency of the zero-order light (dotted line) and the second-order diffracted light (solid line). In FIG. 2, the horizontal axis represents wavelength (nm) and the vertical axis represents diffraction efficiency (%). The first-order diffracted light is the diffracted light used for imaging of the imaging optical system, and it can be seen from FIG. 2A that a very good diffraction efficiency of almost 100% is maintained in the entire wavelength region. Also, from FIG. 2 (b), both the 0th order light and the secondary light that cause unnecessary diffracted light concentrically generated around the high-intensity light source are very small values of 0.02% or less in the entire wavelength range. It turns out that it is.
ＩＴＯは、電子遷移による屈折率の変化に加え、錫によるドーピングや酸素の空孔によりフリーキャリアが発生し、屈折率が変化する。電子遷移による屈折率分散は可視域においては４００ｎｍ〜４５０ｎｍの短波長側で急激に変化し、屈折率の２次分散（θｇＦ）が通常の硝子が分布する所謂ノーマルラインより高い（ノンリニアの）特性を有している。一方、フリーキャリアによる屈折率分散は可視域においては６００ｎｍ〜７００ｎｍの長波長側でその変化が急激となり、非常に強いリニア特性を有している。その二つの影響が組み合わさることにより、屈折率の２次分散（θｇＦ）は他の無機酸化物に比べ非常に小さくなる。従って、ＩＴＯと同様に透明でフリーキャリアの影響があるＳｎＯ２及びＡＴＯ（アンチモンをドーピングしたＳｎＯ２）等も使用することができる。 In addition to the change in refractive index due to electronic transition, ITO generates free carriers due to doping with tin and oxygen vacancies, and the refractive index changes. Refractive index dispersion due to electronic transition changes abruptly on the short wavelength side of 400 nm to 450 nm in the visible region, and the secondary dispersion (θgF) of the refractive index is higher (nonlinear) than the so-called normal line in which normal glass is distributed. have. On the other hand, the refractive index dispersion due to free carriers rapidly changes on the long wavelength side of 600 nm to 700 nm in the visible region, and has very strong linear characteristics. By combining these two effects, the secondary dispersion (θgF) of the refractive index becomes very small compared to other inorganic oxides. Accordingly, SnO 2 and ATO (antimony-doped SnO 2 ), which are transparent and have the influence of free carriers, can be used as well as ITO.
本実施例は、各回折格子の格子頂点が形成する面の形状を従来とは変形することによって樹脂材料の硬化収縮によるレンズ表面の変形を低減している。本実施例では、第１のレンズ３０Ａの上に第１の回折格子２１Ａが形成され、その後、第１の回折格子２１Ａの上に第２の回折格子２５Ａの第２の樹脂材料が塗付され、第２のレンズ４０Ａが配置されて第２の樹脂材料が硬化される。この時、図１示す第１の面２２Ａ、２３Ａを比較すると理解されるように、第１の面２２Ａを光軸周りで凸形状にし、第２の面２６Ａを光軸周りで凹形状にしている。第１の面２２Ａの凸面は第２のレンズ側にあり、第２の面２６Ａの凹面は第１のレンズ側にある。この結果、第１の面２２Ａは第２のレンズ４０ＡのＤＯＥ１１側の面４２Ａと同一形状ではなくない非球面形状であり、第２の面２６Ａは第１のレンズ３０ＡのＤＯＥ１１側の面３２Ａと同一形状ではない非球面形状となっている。 In this embodiment, the deformation of the lens surface due to the curing shrinkage of the resin material is reduced by changing the shape of the surface formed by the grating vertex of each diffraction grating. In the present embodiment, the first diffraction grating 21A is formed on the first lens 30A, and then the second resin material of the second diffraction grating 25A is applied on the first diffraction grating 21A. The second lens 40A is disposed and the second resin material is cured. At this time, as is understood by comparing the first surfaces 22A and 23A shown in FIG. 1, the first surface 22A has a convex shape around the optical axis, and the second surface 26A has a concave shape around the optical axis. Yes. The convex surface of the first surface 22A is on the second lens side, and the concave surface of the second surface 26A is on the first lens side. As a result, the first surface 22A is not the same shape as the DOE11 side surface 42A of the second lens 40A, and the second surface 26A is the same as the DOE11 side surface 32A of the first lens 30A. It is an aspherical shape that is not the same shape.
ＤＯＥ１１は、光軸付近の格子ピッチが広く、光軸から離れるに従って狭くなっていくので、第２の回折格子２５Ａの第２の樹脂材料の塗布量は光軸の周りで最も多く、光軸ＯＡから離れるに従って少なくなる。紫外線硬化樹脂は紫外線を照射することで硬化収縮するが、樹脂量が多い部分においては収縮による応力が大きくなり、光軸付近のレンズ表面の変形量が大きくなり易い。ＤＯＥ１１は、第１の面２２Ａを変形させることでレンズ光軸付近の樹脂量を減らし、第２のレンズ４０Ａの面４４Ａの変形を低減することが可能となる。ＤＯＥ１１の格子高さは２０μｍ程度であり、２μｍ程度の包絡線の変形でも十分にレンズ面精度を改善する効果がある。第１の面２２と第２の面２６の両方を変えることにより、回折格子の各格子によって付加される位相差を設計値と変えること無く面精度の調整が可能である。 The DOE 11 has a wide grating pitch in the vicinity of the optical axis, and becomes narrower as it moves away from the optical axis. Therefore, the amount of the second resin material applied to the second diffraction grating 25A is the largest around the optical axis, and the optical axis OA. Decreases as you move away from The ultraviolet curable resin cures and shrinks when irradiated with ultraviolet rays, but the stress due to the shrinkage increases in a portion where the amount of the resin is large, and the deformation amount of the lens surface near the optical axis tends to increase. The DOE 11 can reduce the deformation of the surface 44A of the second lens 40A by reducing the amount of resin in the vicinity of the lens optical axis by deforming the first surface 22A. The grating height of the DOE 11 is about 20 μm, and even if the envelope is deformed by about 2 μm, the lens surface accuracy is sufficiently improved. By changing both the first surface 22 and the second surface 26, the surface accuracy can be adjusted without changing the phase difference added by each grating of the diffraction grating from the design value.
本実施例によれば、レンズ表面の変形を低減し、色収差を抑えた高い高性能な撮像光学系を実現することができる。 According to the present embodiment, it is possible to realize a high-performance imaging optical system that reduces deformation of the lens surface and suppresses chromatic aberration.
図４は、実施例２の回折光学素子の断面図である。同図において、ＯＡは光軸、３０Ｂは第１のレンズ、４０Ｂは第２のレンズである。第１のレンズ３０Ｂは凸メニスカスレンズであり、第１のレンズ３０ＢのＤＯＥ１１側の面３２Ｂは凹面である。第２のレンズは凹メニスカスレンズであり、第２のレンズ４０ＢのＤＯＥ１１側の面４２Ａは凸面である。 FIG. 4 is a cross-sectional view of the diffractive optical element of Example 2. In the figure, OA is the optical axis, 30B is the first lens, and 40B is the second lens. The first lens 30B is a convex meniscus lens, and the surface 32B on the DOE 11 side of the first lens 30B is a concave surface. The second lens is a concave meniscus lens, and the surface 42A on the DOE 11 side of the second lens 40B is a convex surface.
２１Ｂは低屈折率高分散の紫外線硬化樹脂（第１の樹脂材料）から構成される第１の回折格子であり、アクリル系樹脂材料に無機微粒子を微粒子分散させることで屈折率とアッベ数が最適化されている。２５Ｂは高屈折率低分散の紫外線硬化樹脂（第２の樹脂材料）である。第１の回折格子２１Ｂの格子頂点が形成する第１の面２２Ｂは実線で示された包絡線であり、第２の回折格子２５Ｂの格子頂点が形成する第２の面２６Ｂは点線で示された包絡線となっている。点線２３Ｂは、本実施例を適用しない場合に第１の回折格子の格子頂点が形成する第１の面であり、第２のレンズ４０ＢのＤＯＥ１１側の面４２Ｂと同一形状を有する。ＤＯＥ１１のパワーは正であり、格子ピッチは光軸ＯＡからレンズの周辺に行くに従って狭くなっている。 21B is a first diffraction grating composed of an ultraviolet curable resin (first resin material) having a low refractive index and a high dispersion. The refractive index and the Abbe number are optimal by dispersing inorganic fine particles in an acrylic resin material. It has become. 25B is a high refractive index and low dispersion ultraviolet curable resin (second resin material). The first surface 22B formed by the grating vertex of the first diffraction grating 21B is an envelope indicated by a solid line, and the second surface 26B formed by the grating vertex of the second diffraction grating 25B is indicated by a dotted line. It has become an envelope. A dotted line 23B is a first surface formed by the grating vertex of the first diffraction grating when the present embodiment is not applied, and has the same shape as the surface 42B on the DOE 11 side of the second lens 40B. The power of the DOE 11 is positive, and the grating pitch becomes narrower from the optical axis OA to the periphery of the lens.
第１の回折格子２１Ｂの第１の樹脂材料は無機微粒子を分散させた樹脂材料であるため、紫外線硬化する過程で微粒子が偏り、結果として回折格子に屈折率分布を有している。このような場合、微粒子の偏りによっては片方の包絡線については変形させること無く、片方の包絡線についてだけ非球面とすることで樹脂量を調整すると同時に位相差を波長の整数倍付近の値とすることが可能となる。 Since the first resin material of the first diffraction grating 21B is a resin material in which inorganic fine particles are dispersed, the fine particles are biased during the ultraviolet curing process, and as a result, the diffraction grating has a refractive index distribution. In such a case, depending on the deviation of the fine particles, one envelope is not deformed, and only one envelope is aspherical, and the resin amount is adjusted, and at the same time, the phase difference is set to a value near an integral multiple of the wavelength. It becomes possible to do.
本実施例は、第１の回折格子２１Ｂの格子頂点が形成する第１の面２２Ｂの形状を従来とは変形することによって樹脂材料の硬化収縮によるレンズ表面の変形を低減している。本実施例では、第１のレンズ３０Ｂの上に第１の回折格子２１Ｂが形成され、その後、第１の回折格子２１Ｂの上に第２の回折格子２５Ｂの第２の樹脂材料が塗付され、第２のレンズ４０Ｂが配置されて第２の樹脂材料が硬化される。この時、図４示す第１の面２２Ｂ、２３Ｂを比較すると理解されるように、第１の面２２Ｂを光軸周りで凸形状にしている。第１の面２２Ｂの凸面は第２のレンズ側にある。この結果、第１の面２２Ｂは第２のレンズ４０ＢのＤＯＥ１１側の面４２Ｂと同一形状ではないが、第２の面２６Ｂは第１のレンズ３０ＢのＤＯＥ１１側の面３２Ｂと同一形状のままである。 In this embodiment, the deformation of the lens surface due to the curing shrinkage of the resin material is reduced by deforming the shape of the first surface 22B formed by the grating vertex of the first diffraction grating 21B from the conventional one. In the present embodiment, the first diffraction grating 21B is formed on the first lens 30B, and then the second resin material of the second diffraction grating 25B is applied on the first diffraction grating 21B. The second lens 40B is disposed and the second resin material is cured. At this time, as is understood by comparing the first surfaces 22B and 23B shown in FIG. 4, the first surface 22B has a convex shape around the optical axis. The convex surface of the first surface 22B is on the second lens side. As a result, the first surface 22B does not have the same shape as the DOE11 side surface 42B of the second lens 40B, but the second surface 26B remains the same shape as the DOE11 side surface 32B of the first lens 30B. is there.
回折格子の格子高さとしては、微粒子の濃度を変えることで屈折率とアッベ数のチューニングを行うことで格子高さを１０μｍ程度とすることも可能となる。このような場合には１μｍ程度の包絡線の変形によってもレンズ表面の形状変化を抑制することが可能となる。 As the grating height of the diffraction grating, it is possible to adjust the refractive index and the Abbe number by changing the concentration of the fine particles so that the grating height can be about 10 μm. In such a case, the shape change of the lens surface can be suppressed even by deformation of the envelope of about 1 μm.
本実施例によれば、レンズ表面の変形を低減し、色収差を抑えた高い高性能な撮像光学系を実現することができる。 According to the present embodiment, it is possible to realize a high-performance imaging optical system that reduces deformation of the lens surface and suppresses chromatic aberration.
図５は、実施例３のＤＯＥの断面図である。同図において、ＯＡは光軸、３０Ｃは第１のレンズ、４０Ｃは第２のレンズである。第１のレンズ３０Ｃは凸メニスカスレンズであり、第１のレンズ３０ＣのＤＯＥ１１側の面３２Ｃは凹面である。第２のレンズ４０Ｃは正のパワーを有する凸レンズであり、第２のレンズ４０ＣのＤＯＥ１１側の面４２Ｃは凸面である。 FIG. 5 is a cross-sectional view of the DOE of the third embodiment. In the figure, OA is the optical axis, 30C is the first lens, and 40C is the second lens. The first lens 30C is a convex meniscus lens, and the surface 32C on the DOE 11 side of the first lens 30C is a concave surface. The second lens 40C is a convex lens having positive power, and the surface 42C on the DOE 11 side of the second lens 40C is a convex surface.
２１Ｃは低屈折率高分散の紫外線硬化樹脂（第１の樹脂材料）から構成される第１の回折格子、２５Ｃは高屈折率低分散の紫外線硬化樹脂（第２の樹脂材料）から構成される第２の回折格子である。第１の回折格子２１Ｃの格子頂点が形成する第１の面２２Ｃと、第２の回折格子２５Ｃの格子頂点が形成する第２の面２６Ｃは、図５では共に実線で示された包絡線となっている。点線２３Ｃは、本実施例を適用しない場合に第１の回折格子の格子頂点が形成する第１の面であり、点線２７Ｃは、本実施例を適用しない場合に第２の回折格子の格子頂点が形成する第２の面である。従って、第１の面２３Ｃは、第２のレンズ４０ＣのＤＯＥ１１側の面４２Ｃと同一形状を有し、第２の面２７Ｃは、第１のレンズ３０ＣのＤＯＥ１１側の面３２Ｃと同一形状を有する。ＤＯＥ１１のパワーは正であり、格子ピッチは光軸ＯＡからレンズの周辺に行くに従って狭くなっている。 21C is a first diffraction grating composed of an ultraviolet curable resin (first resin material) having a low refractive index and high dispersion, and 25C is composed of an ultraviolet curable resin (second resin material) having a high refractive index and low dispersion. This is the second diffraction grating. The first surface 22C formed by the grating vertex of the first diffraction grating 21C and the second surface 26C formed by the grating vertex of the second diffraction grating 25C are both envelopes indicated by solid lines in FIG. It has become. The dotted line 23C is the first surface formed by the grating vertex of the first diffraction grating when this embodiment is not applied, and the dotted line 27C is the grating vertex of the second diffraction grating when this embodiment is not applied. Is the second surface formed. Accordingly, the first surface 23C has the same shape as the surface 42C on the DOE 11 side of the second lens 40C, and the second surface 27C has the same shape as the surface 32C on the DOE 11 side of the first lens 30C. . The power of the DOE 11 is positive, and the grating pitch becomes narrower from the optical axis OA to the periphery of the lens.
本実施例は、第１の回折格子２１Ｃの格子頂点が形成する第１の面２２Ｃと第２の回折格子２５Ｃの格子頂点が形成する第２の面２６Ｃの形状を従来とは変形することによって樹脂材料の硬化収縮によるレンズ表面の変形を低減している。本実施例では、第２のレンズ４０Ｃの上に第２の回折格子２５Ｃが形成され、その後、第２の回折格子２５Ｃの上に第１の回折格子２１Ｃの第１の樹脂材料が塗付され、第１のレンズ３０Ｃが配置されて第１の樹脂材料が硬化される。即ち、実施例１、２とは硬化の順序が逆である。この時、図４示す第１の面２２Ｃ、２３Ｃ、第２の面２６Ｃ、２７Ｃを比較すると理解されるように、第１の面２２Ｃを光軸周りで凹形状にしている。第１の面２２Ｃの凹面は第２のレンズ側にある。第２の面２６Ｃを光軸周りで凸形状にしている。第２の面２６Ｃの凸面は第１のレンズ側にある。この結果、第１の面２２Ｃは第２のレンズ４０ＣのＤＯＥ１１側の面４２Ｃと同一形状ではなく、第２の面２６Ｃは第１のレンズ３０ＣのＤＯＥ１１側の面３２Ｃと同一形状ではない。このように、成形プロセスによっては従来と逆方向の格子先端の包絡線とすることでレンズ表面の形状を抑制することが可能である。また、実施例２に対応する材料を使用して成形順序を逆にした場合は第１の面を第２のレンズ４０ＣのＤＯＥ１１側の面４２Ｃと同一形状ではなく、第２の面は第１のレンズ３０ＣのＤＯＥ１１側の面３２Ｃと同一形状にしてもよい。この場合、第１の面は光軸周りで凹形状になり、第１の面の凹面は第２のレンズ側にある。 In the present embodiment, the shapes of the first surface 22C formed by the grating vertices of the first diffraction grating 21C and the second surface 26C formed by the grating vertices of the second diffraction grating 25C are modified from the conventional ones. The deformation of the lens surface due to the curing shrinkage of the resin material is reduced. In the present embodiment, the second diffraction grating 25C is formed on the second lens 40C, and then the first resin material of the first diffraction grating 21C is applied on the second diffraction grating 25C. The first lens 30C is disposed and the first resin material is cured. That is, the order of curing is opposite to that in Examples 1 and 2. At this time, as is understood by comparing the first surfaces 22C and 23C and the second surfaces 26C and 27C shown in FIG. 4, the first surface 22C has a concave shape around the optical axis. The concave surface of the first surface 22C is on the second lens side. The second surface 26C has a convex shape around the optical axis. The convex surface of the second surface 26C is on the first lens side. As a result, the first surface 22C does not have the same shape as the surface 42C on the DOE 11 side of the second lens 40C, and the second surface 26C does not have the same shape as the surface 32C on the DOE 11 side of the first lens 30C. Thus, depending on the molding process, it is possible to suppress the shape of the lens surface by setting the envelope at the grating tip in the opposite direction to the conventional one. Further, when the molding order is reversed using the material corresponding to Example 2, the first surface is not the same shape as the surface 42C on the DOE 11 side of the second lens 40C, and the second surface is the first surface. The lens 30 </ b> C may have the same shape as the surface 32 </ b> C on the DOE 11 side. In this case, the first surface has a concave shape around the optical axis, and the concave surface of the first surface is on the second lens side.
本実施例によれば、レンズ表面の変形を低減し、色収差を抑えた高い高性能な撮像光学系を実現することができる。 According to the present embodiment, it is possible to realize a high-performance imaging optical system that reduces deformation of the lens surface and suppresses chromatic aberration.
実施例１〜３において、ＤＯＥの光路長の付加量を数式（１）に示す位相差関数φ（ｈ）で定義した場合を考える。この時、光路長を付加するベース面をＸ（ｈ）すると、回折格子の形状を次式で定義すると、ベース面Ｘ（ｈ）の少なくとも一部が非球面形状を有する。なお、各変数の定義は数式（２）と同様である。 In the first to third embodiments, let us consider a case where the additional amount of the optical path length of the DOE is defined by the phase difference function φ (h) shown in Expression (1). At this time, if the base surface to which the optical path length is added is X (h), and the shape of the diffraction grating is defined by the following equation, at least a part of the base surface X (h) has an aspherical shape. In addition, the definition of each variable is the same as that of Numerical formula (2).
以上、本発明の好ましい実施例について説明したが、本発明はこれらの実施例に限定されず、その要旨の範囲内で種々の変形及び変更が可能である。 As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.
例えば、樹脂材料は紫外線硬化樹脂に限定されず、他の波長で硬化する樹脂や、熱硬化樹脂などを使用してもよい。 For example, the resin material is not limited to the ultraviolet curable resin, and a resin curable at other wavelengths, a thermosetting resin, or the like may be used.
また、本実施例では、密着２層ＤＯＥについて説明したが、本発明は密着３層ＤＯＥ以上に拡張することができる。この場合、回折光学素子は、第１のレンズと第２のレンズの間に設けられ、複数の回折格子が密着配置されることによって構成される。複数の回折格子は、その中で最も第１のレンズに近い、第１の樹脂材料から構成される第１の回折格子と、最も第２のレンズに近い、第２の樹脂材料から構成される第２の回折格子を含む。 In the present embodiment, the adhesion two-layer DOE has been described. However, the present invention can be expanded beyond the adhesion three-layer DOE. In this case, the diffractive optical element is provided between the first lens and the second lens, and is configured by closely arranging a plurality of diffraction gratings. The plurality of diffraction gratings are composed of a first diffraction grating composed of the first resin material closest to the first lens, and a second resin material closest to the second lens. Includes a second diffraction grating.
また、第１の面において非球面の部分は少なくとも光軸付近の中央部であり、中央部は第２のレンズの内面と形状が異なるが、第１の面が周辺部（像高が高い位置）において球面部や平面部を含んでもよい。また、第１の面の周辺部において第２のレンズの内面と形状が同じでもよい。同様に、第２の面において非球面の部分は少なくとも光軸付近の中央部であり、中央部は第１のレンズの内面と形状が異なるが、第２の面が周辺部において球面部や平面部を含んでもよい。また、第２の面の周辺部において第１のレンズの内面と形状が同じでもよい。 In addition, the aspherical portion of the first surface is at least the central portion near the optical axis, and the central portion is different in shape from the inner surface of the second lens, but the first surface is the peripheral portion (position where the image height is high). ) May include a spherical surface portion or a flat surface portion. Further, the shape of the inner surface of the second lens may be the same in the peripheral portion of the first surface. Similarly, in the second surface, the aspherical portion is at least a central portion near the optical axis, and the central portion is different in shape from the inner surface of the first lens, but the second surface is a spherical portion or a flat surface in the peripheral portion. Part may be included. Further, the shape of the inner surface of the first lens may be the same in the peripheral portion of the second surface.
回折光学素子は回折作用を必要とする光学機器に適用することができる。 The diffractive optical element can be applied to an optical instrument that requires a diffractive action.
１１…回折光学素子、２１Ａ〜Ｃ…第１の回折格子、２２Ａ〜Ｃ…第１の面、２５Ａ〜Ｃ…第２の回折格子、２６Ａ〜Ｃ…第２の面、３０Ａ〜Ｃ…第１のレンズ、４０Ａ〜Ｃ…第２のレンズ DESCRIPTION OF SYMBOLS 11 ... Diffractive optical element, 21A-C ... 1st diffraction grating, 22A-C ... 1st surface, 25A-C ... 2nd diffraction grating, 26A-C ... 2nd surface, 30A-C ... 1st Lens, 40A-C ... second lens
Claims (9)
前記複数の回折格子は、前記第１のレンズに最も近い、第１の樹脂材料から構成される第１の回折格子と、前記第２のレンズに最も近い、第２の樹脂材料から構成される第２の回折格子を含み、
前記第１のレンズの上に金型を配置して前記第１のレンズと前記金型の間に前記第１の樹脂材料を充填し、前記第１の樹脂材料を硬化し、前記第１の回折格子を前記第１のレンズの上に形成するステップと、
前記複数の回折格子の中で前記第２の回折格子よりも前記第１のレンズ側にある回折格子と前記第２のレンズの間に前記第２の樹脂材料を充填し、前記第２の樹脂材料を硬化し、前記第２の回折格子を形成するステップと、
を有し、
前記第１の回折格子の格子頂点が形成する第１の面は非球面の部分を有し、前記非球面の部分は前記第２のレンズの回折光学素子側の面とは異なる形状を有し、前記第１のレンズの光軸付近に前記第２のレンズ側に凸面を有することを特徴とする回折光学素子の製造方法。 A method of manufacturing a diffractive optical element that is provided between a first lens and a second lens and forms a diffractive optical element in which a plurality of diffraction gratings are closely arranged,
The plurality of diffraction gratings are composed of a first diffraction grating composed of a first resin material closest to the first lens and a second resin material closest to the second lens. Including a second diffraction grating;
A mold is disposed on the first lens, the first resin material is filled between the first lens and the mold, the first resin material is cured, and the first Forming a diffraction grating on the first lens;
The second resin material is filled between the second lens and a diffraction grating that is closer to the first lens than the second diffraction grating among the plurality of diffraction gratings. Curing a material to form the second diffraction grating;
Have
The first surface formed by the grating vertex of the first diffraction grating has an aspheric surface portion, and the aspheric surface portion has a shape different from the surface of the second lens on the diffractive optical element side. A method of manufacturing a diffractive optical element, comprising a convex surface on the second lens side in the vicinity of the optical axis of the first lens.
前記複数の回折格子は、前記第１のレンズに最も近い、第１の樹脂材料から構成される第１の回折格子と、前記第２のレンズに最も近い、第２の樹脂材料から構成される第２の回折格子を含み、
前記第２のレンズの上に金型を配置して前記第２のレンズと前記金型の間に前記第２の樹脂材料を充填し、前記第２の樹脂材料を硬化し、前記第２の回折格子を前記第２のレンズの上に形成するステップと、
前記複数の回折格子の中で前記第１の回折格子よりも前記第２のレンズ側にある回折格子と前記第１のレンズの間に前記第１の樹脂材料を充填し、前記第１の樹脂材料を硬化し、前記第１の回折格子を形成するステップと、
を有し、
前記第１の回折格子の格子頂点が形成する第１の面は非球面の部分を有し、前記非球面の部分は前記第２のレンズの回折光学素子側の面とは異なる形状を有し、前記第１のレンズの光軸付近に前記第２のレンズ側に凹面を有することを特徴とする回折光学素子の製造方法。 A method of manufacturing a diffractive optical element that is provided between a first lens and a second lens and forms a diffractive optical element in which a plurality of diffraction gratings are closely arranged,
The plurality of diffraction gratings are composed of a first diffraction grating composed of a first resin material closest to the first lens and a second resin material closest to the second lens. Including a second diffraction grating;
A mold is disposed on the second lens, the second resin material is filled between the second lens and the mold, the second resin material is cured, and the second resin material is cured. Forming a diffraction grating on the second lens;
Among the plurality of diffraction gratings, the first resin material is filled between the first lens and a diffraction grating located closer to the second lens than the first diffraction grating, and the first resin Curing a material to form the first diffraction grating;
Have
The first surface formed by the grating vertex of the first diffraction grating has an aspheric surface portion, and the aspheric surface portion has a shape different from the surface of the second lens on the diffractive optical element side. A method of manufacturing a diffractive optical element, comprising a concave surface on the second lens side in the vicinity of the optical axis of the first lens.
ｎｄ２＞ｎｄ１
νｄ１＞νｄ２ The refractive index of the first resin material of the first diffraction grating is nd1, the refractive index of the second resin material of the second diffraction grating is nd2, and the Abbe number of the first resin material is νd1, 6. The method of manufacturing a diffractive optical element according to claim 1, wherein the following equation is established when the Abbe number of the second resin material is νd <b> 2.
nd2> nd1
νd1> νd2
φ（ｈ）＝（Ｃ２ｈ２＋Ｃ４ｈ４＋Ｃ６ｈ６＋…）×２π／λ
前記ベース面の少なくとも一部は非球面形状を有することを特徴とする請求項１または３に記載の回折光学素子の製造方法。
The height from the optical axis is h, the n-th order (even order) coefficient is Cn, the wavelength is λ, the optical path length addition amount of the diffractive optical element is φ (h), and the base surface to which the optical path length is added is X (H) When the position in the optical axis direction is x, the center ring is one ring zone, the ring number is k, and the lattice height is d0, the following equation holds:
φ (h) = (C2h 2 + C4h 4 + C6h 6 +...) × 2π / λ
The method for manufacturing a diffractive optical element according to claim 1, wherein at least a part of the base surface has an aspherical shape.
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|---|---|---|---|---|
| CN109870809A (en) * | 2017-12-01 | 2019-06-11 | 苏州苏大维格光电科技股份有限公司 | A kind of nearly eye display eyeglass and nearly eye display device |
| CN112394512A (en) * | 2019-08-16 | 2021-02-23 | 苏州苏大维格科技集团股份有限公司 | Head-mounted display device |
| WO2021199707A1 (en) * | 2020-03-31 | 2021-10-07 | 富士フイルム株式会社 | Diffraction optical element and method for producing diffraction optical element |
| JP7418079B2 (en) | 2019-09-30 | 2024-01-19 | キヤノン株式会社 | Diffractive optical elements, optical instruments, imaging devices |
| JP7433765B2 (en) | 2018-03-16 | 2024-02-20 | キヤノン株式会社 | Optical elements, optical instruments and imaging devices |
-
2013
- 2013-07-02 JP JP2013138563A patent/JP2015011293A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109870809A (en) * | 2017-12-01 | 2019-06-11 | 苏州苏大维格光电科技股份有限公司 | A kind of nearly eye display eyeglass and nearly eye display device |
| JP7433765B2 (en) | 2018-03-16 | 2024-02-20 | キヤノン株式会社 | Optical elements, optical instruments and imaging devices |
| CN112394512A (en) * | 2019-08-16 | 2021-02-23 | 苏州苏大维格科技集团股份有限公司 | Head-mounted display device |
| JP7418079B2 (en) | 2019-09-30 | 2024-01-19 | キヤノン株式会社 | Diffractive optical elements, optical instruments, imaging devices |
| WO2021199707A1 (en) * | 2020-03-31 | 2021-10-07 | 富士フイルム株式会社 | Diffraction optical element and method for producing diffraction optical element |
| JP7434530B2 (en) | 2020-03-31 | 2024-02-20 | 富士フイルム株式会社 | Diffractive optical element and method for manufacturing the diffractive optical element |
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