JP3315806B2 - Image plane measuring device - Google Patents
Image plane measuring deviceInfo
- Publication number
- JP3315806B2 JP3315806B2 JP06292294A JP6292294A JP3315806B2 JP 3315806 B2 JP3315806 B2 JP 3315806B2 JP 06292294 A JP06292294 A JP 06292294A JP 6292294 A JP6292294 A JP 6292294A JP 3315806 B2 JP3315806 B2 JP 3315806B2
- Authority
- JP
- Japan
- Prior art keywords
- diffraction grating
- image plane
- lens
- measured
- image
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Description
【0001】[0001]
【産業上の利用分野】本発明は、カメラレンズ等により
形成される像面の状態を測定する像面測定装置に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image plane measuring apparatus for measuring a state of an image plane formed by a camera lens or the like.
【0002】[0002]
【従来技術およびその問題点】複数のレンズ素子から構
成される撮影レンズ系では、レンズ素子が1個でも偏心
ないし傾斜すると、これが結像系である場合には像面に
倒れを生じ、さらに諸収差のバランスが崩れて結像性能
が劣化する。つまり、被写体像が、画面中央付近ではフ
ィルム面上に結像するが、周辺部ではフィルム面の前方
または後方に結像してしまい、撮影画面の周辺がぼける
という問題を生じてしまう。そのため、各レンズ素子を
偏心および傾斜しないようにレンズ鏡筒に対して正確に
位置決めする必要がある。2. Description of the Related Art In a photographing lens system composed of a plurality of lens elements, if even one lens element is decentered or inclined, if the lens element is an imaging system, the image plane is tilted. The aberration balance is lost, and the imaging performance is degraded. In other words, the subject image forms on the film surface near the center of the screen, but forms on the front or rear of the film surface in the peripheral portion, causing a problem that the periphery of the shooting screen is blurred. Therefore, it is necessary to accurately position each lens element with respect to the lens barrel so as not to be decentered and tilted.
【0003】しかしながら、レンズ素子の組付け時の機
械的精度を向上させるためには、各部品の精度や、組付
けの精度が高く要求され、コスト、時間がかかるという
問題があった。したがって、レンズ素子を鏡筒などに組
み付けた後に像面の傾斜を簡単に測定できる装置が望ま
れていた。However, in order to improve the mechanical accuracy at the time of assembling the lens element, there is a problem that the accuracy of each component and the assembling accuracy are required to be high, and the cost and the time are increased. Therefore, there has been a demand for an apparatus that can easily measure the inclination of the image plane after assembling the lens element to a lens barrel or the like.
【0004】[0004]
【発明の目的】本発明は、前記従来技術の問題に鑑みて
なされたもので、レンズにより形成される像面の傾きを
簡単かつ迅速に検出できる像面測定装置を提供すること
を目的とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide an image plane measuring apparatus capable of easily and quickly detecting the inclination of an image plane formed by a lens. .
【0005】[0005]
【発明の概要】この目的を達成する本願発明は、被測定
レンズに測定光束を照射する測定光源と、被測定レンズ
の前に配置され、前記測定光源から発した測定光束を回
折させる回折格子と、前記被測定レンズの焦点位置また
はその近傍に配置され、前記回折格子で回折して被測定
レンズを透過した回折光を反射する基準反射面と、この
基準反射面で反射され、前記被測定レンズ、前記回折格
子を介して合成された異なる次数の回折光により形成さ
れる干渉縞を受光して画像データに光電変換する受光手
段と、前記受光手段が光電変換した画像データに基づい
て上記被測定レンズの像面の状態を測定する測定手段
と、前記回折格子を移動させて上記受像手段上の干渉縞
の位相をシフトさせる回折格子移動手段と、を備えたこ
とに特徴を有する。SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a measuring light source for irradiating a measured light beam to a lens to be measured, a diffraction grating disposed in front of the measured lens and diffracting the measuring light beam emitted from the measuring light source. A reference reflection surface that is disposed at or near the focal position of the lens to be measured and reflects the diffracted light diffracted by the diffraction grating and transmitted through the lens to be measured; A light-receiving means for receiving interference fringes formed by diffracted lights of different orders synthesized via the diffraction grating and photoelectrically converting the interference fringes into image data; and performing the measurement based on the image data photoelectrically converted by the light-receiving means. It is characterized by comprising measuring means for measuring the state of the image plane of the lens, and diffraction grating moving means for moving the diffraction grating to shift the phase of interference fringes on the image receiving means.
【0006】[0006]
【実施例】以下図示実施例に基づいて本発明を説明す
る。図1は、本発明を適用した像面測定装置の光学的構
成を示す光路図である。レーザ光源11から照射された
平行光束は、ハーフミラー13を透過して回折格子15
により回折されて、被測定レンズ17により基準反射面
19に集束される。基準反射面19は、±一次回折光の
みを反射して他の次数の回折光を吸収するものであり、
被測定レンズ17の焦点位置に光軸Oと直交する向きに
配置されている。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. FIG. 1 is an optical path diagram showing an optical configuration of an image plane measuring apparatus to which the present invention is applied. The parallel light beam emitted from the laser light source 11 passes through the half mirror 13 and passes through the diffraction grating 15
And is focused on the reference reflecting surface 19 by the lens under measurement 17. The reference reflection surface 19 reflects only the ± first-order diffracted lights and absorbs other-order diffracted lights,
It is arranged at the focal position of the lens 17 to be measured in a direction orthogonal to the optical axis O.
【0007】この基準反射面19は、円形の中心部分1
9a、これと同心の環状の反射部分19bおよび外方部
分19cを備えている。反射部分19bは、入射光を反
射するが、中心部分19aおよび外方部分19bは入射
光を吸収して反射しない。つまり基準反射面19は、中
心を光軸Oと一致させた状態で、反射部分19bに±一
次回折光が入射し、中心部分19aに0次回折光が入射
し、外方部分19cに他の次数の回折光が入射するよう
に形成してある。なお、基準反射面19は、±一次回折
光のみを反射し、他の次数の回折光は透過する構成でも
よい。[0007] The reference reflecting surface 19 has a circular central portion 1.
9a, an annular reflecting portion 19b and an outer portion 19c concentric with the reflecting portion 9a. The reflecting portion 19b reflects the incident light, but the central portion 19a and the outer portion 19b absorb the incident light and do not reflect it. That is, in the reference reflecting surface 19, with the center aligned with the optical axis O, the ± first-order diffracted light enters the reflecting portion 19b, the 0th-order diffracted light enters the central portion 19a, and another order enters the outer portion 19c. Is formed so that the diffracted light of the incident light enters. The reference reflecting surface 19 may be configured to reflect only the ± first-order diffracted lights and transmit diffracted lights of other orders.
【0008】基準反射面19で反射された±1次回折光
は、光路を逆行して再び被測定レンズ17を透過し、回
折格子15で回折され、ハーフミラー13で結像レンズ
21方向に反射される。そして、回折格子15により、
往路で+1次方向に回折されさらに復路で−1次方向に
回折された回折光、および往路で−1次方向に回折され
復路で+1次方向に回折された回折光のみが、結像レン
ズ21のほぼ焦点位置に配設された空間フィルタ23に
より選択透過され、測定面25上に集束される。そし
て、測定面25上に集束された±1次回折光により形成
される干渉縞(図3参照)が撮像素子31により撮像
(光電変換)され、画像データ処理装置により処理され
る。空間フィルタ23は、中央に上記±1次回折光のみ
を透過させる孔23aを有する。孔23aの周辺部分2
3bは、入射光を吸収する。The ± 1st-order diffracted light reflected by the reference reflecting surface 19 travels back through the optical path, passes through the lens 17 to be measured again, is diffracted by the diffraction grating 15, and is reflected by the half mirror 13 toward the imaging lens 21. You. And, by the diffraction grating 15,
Only the diffracted light that is diffracted in the +1 order direction on the outward path and further diffracted in the −1 order direction on the return path, and the diffracted light that is diffracted in the −1 order direction on the outward path and diffracted in the +1 order direction on the return path. Are selectively transmitted by a spatial filter 23 disposed at a substantially focal point of the light-emitting device, and focused on a measurement surface 25. Then, interference fringes (see FIG. 3) formed by the ± 1st-order diffracted light focused on the measurement surface 25 are imaged (photoelectric conversion) by the image sensor 31 and processed by the image data processing device. The spatial filter 23 has a hole 23a at the center for transmitting only the ± first-order diffracted light. Peripheral part 2 of hole 23a
3b absorbs incident light.
【0009】回折格子15は、所定ピッチの格子であ
り、被測定レンズ17のほぼ前側焦点位置に光軸Oと直
交する向きに配置されている。撮像素子31としては、
CCDイメージセンサ等が利用できる。撮像素子31か
ら出力される画像データは、マイクロコンピュータ等の
画像処理装置33で所定の画像処理を施して所定のデー
タを演算し、記録媒体に記録し、あるいはディスプレイ
に表示して像面の倒れを視覚的に観察する。The diffraction grating 15 is a grating having a predetermined pitch, and is disposed substantially at the front focal position of the lens 17 to be measured in a direction orthogonal to the optical axis O. As the image sensor 31,
A CCD image sensor or the like can be used. The image data output from the image sensor 31 is subjected to predetermined image processing by an image processing device 33 such as a microcomputer to calculate predetermined data, recorded on a recording medium, or displayed on a display to cause the image plane to tilt. Is visually observed.
【0010】次に、像面の倒れにより発生する±1次回
折光の光路差を、図2を参照して説明する。図2は、基
準反射面19付近の光路の様子を示してある。同図にお
いて、像面31は、光軸Oを含む面内において基準反射
面19から反時計方向に角度φだけ倒れている。この倒
れ角φが最大になる光軸周りの回転角θを基準反射面1
9に対する最大傾斜方向とする。本実施例において、回
転角θは光軸Oと直交する面内の角度、倒れ角φは光軸
Oを含む面内の角度であって、回転角θの初期位置はX
軸方向(図面においては紙面に垂直な方向)とし、倒れ
角φは基準反射面19から測る。Next, the optical path difference of ± 1st-order diffracted light generated by the tilt of the image plane will be described with reference to FIG. FIG. 2 shows a state of an optical path near the reference reflection surface 19. In the figure, the image plane 31 is tilted counterclockwise by an angle φ from the reference reflection surface 19 in a plane including the optical axis O. The rotation angle θ about the optical axis at which the tilt angle φ becomes maximum is determined by the reference reflection surface 1.
9 as the maximum inclination direction. In this embodiment, the rotation angle θ is an angle in a plane orthogonal to the optical axis O, the tilt angle φ is an angle in a plane including the optical axis O, and the initial position of the rotation angle θ is X
The inclination angle φ is measured from the reference reflection surface 19 in the axial direction (in the drawing, the direction perpendicular to the paper surface).
【0011】+1次回折光は、入射方向から見ると、あ
たかもA点から発散(反射)したように見える。したが
って、+1次回折光の見掛け上の発散位置は、距離2T
だけ像面から遠くなる。一方、対応する−1次回折光
は、入射方向から見ると、あたかもB点から発散(反
射)したように見える。したがって、−1次回折光の見
掛け上の発散位置は距離2Tだけ像面に近くなる。When viewed from the incident direction, the + 1st-order diffracted light appears to diverge (reflect) from point A. Therefore, the apparent divergence position of the + 1st-order diffracted light is the distance 2T
Only far from the image plane. On the other hand, when viewed from the incident direction, the corresponding -1st-order diffracted light appears to diverge (reflect) from point B. Therefore, the apparent divergence position of the -1st-order diffracted light is closer to the image plane by the distance 2T.
【0012】このように+1次回折光と−1次回折光と
では、見掛け上の発散点のずれが計4T生じるので、こ
の発散点のずれにより±1次回折光の干渉縞は、デフォ
ーカスに相当する曲がりを生じる。この干渉縞の曲り量
をPDとすると、この曲り量PDから、基準面19に対
する像面31の総倒れ量dおよび倒れ角φが下記式によ
り求まる。 d=PD/2[1−{4F2 /(4F2 +1)}1/2 ] … ただし、Fは、被検レンズの有効FNOである。倒れ角φ
は、+1次回折光の高さをy(光軸Oから発散点Aまで
の距離)とすると、 φ=d/2y =PD/4y[1−{4F2 /(4F2 +1)}1/2 ] =PD・Pitch /4λf[1−{4F2 /(4F2 +1)}1/2 ]… となる。ただし、Pitch は回折格子のピッチ、λは測定
レーザの波長、fは被測定レンズ17の焦点距離、dは
発散点A、B間の光軸方向距離である。したがって、曲
り量PDを測定すれば倒れの量Tおよび倒れ角φが求ま
る。なお、倒れ角φは正確には、φ=tan-1d/2y
であるが、通常、yに比してdが非常に小さいので、t
an-1d/2y≒d/2yと近似できる。As described above, the apparent divergence point of the + 1st-order diffracted light and the -1st-order diffracted light have a shift of 4T in total, so that the interference fringe of the ± 1st-order diffracted light corresponds to defocus due to the shift of the divergence point. Causes bending. Assuming that the amount of bending of the interference fringes is PD, the total amount of tilt d and the tilt angle φ of the image plane 31 with respect to the reference plane 19 can be obtained from the following formula from the amount of bending PD. d = PD / 2 [1− {4F 2 / (4F 2 +1)} 1/2 ] where F is the effective FNO of the lens to be measured. Falling angle φ
It is + 1 when the height of the order diffracted light and y (the distance from the optical axis O to the diverging point A), φ = d / 2y = PD / 4y [1- {4F 2 / (4F 2 +1)} 1/2 ] = PD · Pitch / 4λf [1− {4F 2 / (4F 2 +1)} 1/2 ]. Here, Pitch is the pitch of the diffraction grating, λ is the wavelength of the measurement laser, f is the focal length of the lens 17 to be measured, and d is the distance between the diverging points A and B in the optical axis direction. Therefore, by measuring the amount of bending PD, the amount of tilt T and the tilt angle φ can be obtained. Note that the tilt angle φ is exactly φ = tan −1 d / 2y
However, since d is very small compared to y, t
It can be approximated as an −1 d / 2y ≒ d / 2y.
【0013】しかし、図では、理解を容易にするために
同心円状の複数の干渉縞を示してあるが、通常は1本以
下の干渉縞しか表われないので、干渉縞から直接曲り量
PDを求めることができない。そこで本実施例では、こ
の干渉縞、つまり明るさを撮像素子31で撮像し、画像
処理装置33で所定の分析を行なって曲り量PDを求め
る。[0013] However, in the figure, a plurality of concentric interference fringes are shown for easy understanding, but usually only one or less interference fringes are shown. I can't ask. Therefore, in the present embodiment, the interference fringe, that is, the brightness is imaged by the image sensor 31, and the image processing device 33 performs a predetermined analysis to obtain the amount of bending PD.
【0014】本発明では、干渉縞の曲がり量PDを、回
折格子15を移動させて測定することに特徴がある。つ
まり、回折格子15を格子ベクトル方向に移動させたと
きに生じる干渉縞の位相シフト(明暗の変化)を測定す
るのである。干渉縞を1フリンジ位相シフトさせるため
の回折格子15の移動距離は式、 Pith/m・P …… により求まる。ただし、mは干渉させる回折光の回折次
数の差、Pは回折格子15を通る回数により定まる係数
である。例えば±1次回折光を干渉させる場合はm=
2、回折格子15を2回通るときにはP=2、回折格子
15を1回しか通らないときにはP=1であり、本実施
例では2回通るのでP=2である。The present invention is characterized in that the bending amount PD of the interference fringes is measured by moving the diffraction grating 15. That is, the phase shift (change in brightness) of the interference fringe caused when the diffraction grating 15 is moved in the grating vector direction is measured. The movement distance of the diffraction grating 15 for shifting the interference fringes by one fringe phase is obtained by the following equation: Pith / m · P. Here, m is a difference between diffraction orders of diffracted light to be interfered, and P is a coefficient determined by the number of times of passing through the diffraction grating 15. For example, when making ± 1st-order diffracted light interfere, m =
2. P = 2 when the light passes through the diffraction grating 15 twice, and P = 1 when the light passes through the diffraction grating 15 only once. In this embodiment, P = 2 because the light passes through the diffraction grating 15 twice.
【0015】本実施例では、回折格子15を上記式で
求めた所定距離移動し、その移動の前後に亙って観測面
25上の干渉縞を測定し、その測定結果に基づいて最小
2乗法等により処理した干渉縞情報からデフォーカス成
分、つまり曲り量を抽出してこの曲り量PDを補正量と
する。そして、式および式により、最大倒れ量d、
倒れ方向θを求める。In this embodiment, the diffraction grating 15 is moved by a predetermined distance determined by the above equation, interference fringes on the observation surface 25 are measured before and after the movement, and the least squares method is performed based on the measurement result. The defocus component, that is, the amount of bending is extracted from the interference fringe information processed in the above-described manner, and the amount of bending PD is used as a correction amount. Then, the maximum falling amount d,
Obtain the falling direction θ.
【0016】次に、測定装置による像面測定について、
図4〜図8に示した実施例に基づいてより具体的に説明
する。図4に示した実施例の回折格子移動装置29は、
回折格子15を光軸Oまたは光軸Oと平行な軸を中心に
して回転し、かつ光軸Oに対して直交する任意の方向
に、所定距離精密に移動できるマイクロステージを備え
ている。また、本実施例において、光軸Oを中心とした
回折格子15の回転角をψとし、格子ベクトルがX軸と
平行な状態を初期位置としてこの角度をψ0 =0(図4
(A)参照)とし、格子ベクトルがY軸と平行になる状
態を角度ψ90(図4(B)参照)、格子ベクトルが初期
位置から反時計方向に45゜回転した状態を角度ψ+45
(図5(A)参照)、初期位置から時計方向に45゜回
転した状態を角度ψ-45 (図5(B)参照)とする。Next, regarding the image plane measurement by the measuring device,
This will be described more specifically on the basis of the embodiment shown in FIGS. The diffraction grating moving device 29 of the embodiment shown in FIG.
A micro-stage is provided, which rotates the diffraction grating 15 about the optical axis O or an axis parallel to the optical axis O, and can precisely move a predetermined distance in an arbitrary direction perpendicular to the optical axis O. Further, in the present embodiment, the rotation angle of the diffraction grating 15 about the optical axis O is 、, and the angle is ψ 0 = 0 (FIG. 4
(See FIG. 4A), the state where the lattice vector is parallel to the Y axis is angle ψ 90 (see FIG. 4B), and the state where the lattice vector is rotated 45 ° counterclockwise from the initial position is angle ψ +45.
(See FIG. 5 (A)), the state rotated 45 ° clockwise from the initial position is defined as an angle ψ -45 (see FIG. 5 (B)).
【0017】(実施例1)この実施例1では、回折格子
15を、初期位置ψ0 (図4(A)の向き)と、初期位
置から90゜回転させた回転位置ψ90(図4(B)の向
き)に回転させる。そして、それぞれの回転位置におい
て格子ベクトル方向に、上記式で求めた所定距離移動
させて、その移動により生じる干渉縞の明暗の回数から
像面31の倒れ量Δdx 、Δdy を測定(演算)する。
そして、これらの倒れ量Δdx 、Δdy から、像面31
の最大倒れ量dおよびその倒れ方向(回転角θ)をそれ
ぞれ式、 d=(Δdx 2+Δdy 2)1/2 …… θ=tan-1 (Δdy /Δdx ) …… により求める。(Embodiment 1) In this embodiment 1, the diffraction grating 15 has an initial position ψ 0 (the direction of FIG. 4A) and a rotation position ψ 90 (FIG. 4 (B) direction). Then, the grating vector direction in the respective rotational position, by a predetermined distance moved was determined by the above formula, the amount of inclination [Delta] d x of the image plane 31 from the number of light and dark interference fringes caused by the movement, measuring [Delta] d y (operation) I do.
Then, these inclination amount [Delta] d x, from [Delta] d y, the image plane 31
Expression of the maximum amount of inclination d and its collapse direction (rotation angle theta) respectively, determined by d = (Δd x 2 + Δd y 2) 1/2 ...... θ = tan -1 (Δd y / Δd x) .......
【0018】(実施例2)実施例1は回折格子15を直
交する異なる方向(X軸、Y軸方向)に移動して測定し
ているが、図5の実施例2は、回折格子15を同一方向
(X軸)方向に移動して測定する実施例である。この実
施例2では、回折格子15の移動方向に対して、回折格
子15の格子ベクトルが+45゜、−45゜をなす角度
ψ+45 、ψ-45 に回転させる。そして、回折格子15を
各回転位置においてそれぞれ1フリンジ分移動させて、
その移動過程における干渉縞の変化を測定し、像面31
の倒れ量Δd+45 、Δd-45 を演算により求める。そし
て、これらの演算値から、像面31の最大倒れ量dおよ
び倒れ方向θが、ぞれぞれ式、 d=(Δd+45 2+Δd-45 2)1/2 …… θ=tan-1 (Δd+45 /Δd-45 )−45゜ …… により求まる。この実施例2では、回折格子15の移動
量を、実施例1の移動量の21/2 倍にする。(Embodiment 2) In Embodiment 1, measurement is performed by moving the diffraction grating 15 in different directions orthogonal to each other (X-axis and Y-axis directions). In Embodiment 2 of FIG. This is an example in which measurement is performed while moving in the same direction (X axis). In the second embodiment, the diffraction grating 15 is rotated by angles 回転 +45 and ψ -45 with respect to the moving direction of the diffraction grating 15 so that the grating vector of the diffraction grating 15 forms + 45 ° and −45 °. Then, the diffraction grating 15 is moved by one fringe at each rotation position.
The change of the interference fringes in the moving process is measured, and the
The inclination amounts Δd +45 and Δd -45 are obtained by calculation. From these calculated values, the maximum amount of inclination d and inclination direction theta of the image plane 31, Zorezo Re formula, d = (Δd +45 2 + Δd -45 2) 1/2 ...... θ = tan -1 (Δd +45 / Δd -45 ) −45 °... In the second embodiment, the moving amount of the diffraction grating 15 is set to 21/2 times the moving amount of the first embodiment.
【0019】実施例1では、得られる干渉縞情報は格子
ベクトル方向に依存する情報であり、干渉縞情報と回折
格子の移動方向とは基本的には関係しないものであっ
た。一方、回折格子15を移動する回折格子移動装置2
9のステージは高分解能が要求される。例えば、Pitch
=25(μm)の回折格子で±1次回折光を干渉させ、位
相シフトアルゴリズムに4ステップ法を用いたときに
は、ステージを1.5625μm単位で移動させる。In the first embodiment, the obtained interference fringe information is information dependent on the direction of the grating vector, and the interference fringe information and the moving direction of the diffraction grating are basically unrelated. On the other hand, the diffraction grating moving device 2 that moves the diffraction grating 15
Stage 9 requires high resolution. For example, Pitch
When the ± 1st-order diffracted light interferes with the diffraction grating of = 25 (μm) and the 4-step method is used for the phase shift algorithm, the stage is moved in units of 1.5625 μm.
【0020】そこで、実施例2のように、回折格子15
の移動方向を格子ベクトル方向から所定角度ψ回転させ
る。このように格子ベクトル方向とは異なる方向に移動
することにより、ステージ移動に対する干渉縞の変化感
度が鈍くなり、ステージ移動量が1/cos ψ(<1)倍
されて干渉縞の変化に表われるので、ステージの分解能
が機械的分解能よりも高くなる。また、この移動方向
は、回折格子15の面内(光軸Oと直交する方向)で
も、面外(光軸Oと直交しない方向)でもよい。先の実
施例2は、ψ=45゜の例である。実施例2での回折格
子15の移動量は、実施例1の21/2 倍、つまり、分解
能が21/2 倍になる。なお、角度ψは任意である。Therefore, as in the second embodiment, the diffraction grating 15
Is rotated by a predetermined angle か ら from the lattice vector direction. By moving in a direction different from the lattice vector direction in this manner, the sensitivity of the change of the interference fringes to the stage movement becomes slow, and the stage movement amount is multiplied by 1 / cosψ (<1) and appears in the change of the interference fringes. Therefore, the resolution of the stage is higher than the mechanical resolution. The moving direction may be in the plane of the diffraction grating 15 (a direction orthogonal to the optical axis O) or out of the plane (a direction not orthogonal to the optical axis O). The second embodiment is an example where {= 45}. The moving amount of the diffraction grating 15 in the second embodiment is 2 1/2 times that in the first embodiment, that is, the resolution is 2 1/2 times. Note that the angle ψ is arbitrary.
【0021】被測定レンズ17の像面に倒れおよび曲が
りが存在すると、±1次回折光の基準反射面19付近の
発散点が、倒れのみで曲りがないときの発散点よりもず
れる。例えば、倒れがないときの発散点A、Bに対し
て、図6に示した発散点Ad、Bdに示すようにずれ
る。基準面反射19からの発散点Ad、Bdまでの距離
をそれぞれd+10 、d-10 とする。距離d+10 、d-10
はそれぞれ、0次回折光と1次回折光、0次回折光と−
1次回折光を空間フィルタで選択してそれらを干渉さ
せ、その干渉縞を実施例1、2により測定し、演算する
ことにより求まる。そして、平均倒れ量および像面の曲
りは式、 (平均倒れ量)=d+10 −d-10 (像面の曲り)=d+10 +d-10 により求まる。If the image plane of the lens 17 to be measured has a tilt and a bend, the divergence point of the ± 1st-order diffracted light near the reference reflection surface 19 is shifted from the divergence point when only the tilt and no bend. For example, divergence points A and B when there is no fall are shifted as shown by divergence points Ad and Bd shown in FIG. The distances from the reference surface reflection 19 to the divergence points Ad and Bd are d +10 and d -10 , respectively. Distance d +10 , d -10
Are the 0th-order diffracted light and the 1st-order diffracted light, and the 0th-order diffracted light and-
The first order diffracted light is selected by a spatial filter to cause them to interfere with each other, and the interference fringes are measured and calculated according to the first and second embodiments. The average amount of inclination and the image plane of the bend of the formula, obtained by (average inclination amount) = d +10 -d -10 (curvature of image surface) = d +10 + d -10.
【0022】さらに複雑な像面の変化があるときには、
±1次回折光以外の次数の回折光を選択する。例えば、
1次回折光と+0次回折光とを選択し、回折格子15の
回折格子ベクトルの回転角をψとしたときの発散点のず
れd10(ψ)を、回折格子15を回転しながら、0次回
折光の照射位置に対する1次回折光の照射位置のずれを
測定する。なお、格子ベクトルが水平方向、図4の
(A)の向きにあるときを初期位置、ψ=Oとする。同
様に、2、3、……、n次回折光に対して測定し、d20
(ψ)、d30(ψ)、…dn0(ψ)を求める。そして、
d10(ψ)、d20(ψ)、…を結んだ曲線が、像面位置
の2次元分布(極座標表示)になる(図7参照)。図8
には、その3次元分布を示してある。When there is a more complicated image plane change,
Select a diffracted light of an order other than the ± first-order diffracted light. For example,
The first order diffracted light and the +0 order diffracted light are selected, and the deviation d 10 (ψ) of the divergence point when the rotation angle of the diffraction grating vector of the diffraction grating 15 is set to 0 is obtained by rotating the diffraction grating 15 to the 0th order diffracted light. The deviation of the irradiation position of the first-order diffracted light with respect to the irradiation position is measured. When the lattice vector is in the horizontal direction, that is, in the direction shown in FIG. 4A, the initial position is defined as ψ = O. Similarly, 2,3, ..., measured against n-order diffracted light, d 20
(Ψ), d 30 (ψ),... D n0 (ψ) are obtained. And
The curve connecting d 10 (ψ), d 20 (ψ),... becomes a two-dimensional distribution (polar coordinate display) of the image plane position (see FIG. 7). FIG.
Shows the three-dimensional distribution.
【0023】以上の通り本実施例1では、平行なレーザ
光を、回折格子15で回折させて被測定レンズ17によ
り基準反射面19付近に結像させ、基準反射面19で±
1次回折光のみを反射させ、再び回折格子15で回折さ
せ、空間フィルタ23により往路における+1次回折光
で復路での−1次回折光、および往路における−1次回
折光で復路での+1次回折光のみを透過させてこれらを
干渉させ、その干渉縞を測定する装置であって、回折格
子15を初期位置と初期位置から90゜回転させた位置
とでそれぞれ格子ベクトル方向に移動させているので、
2倍の精度で像面の倒れ量および倒れ方向を測定するこ
とができる。実施例2では回折格子15を格子ベクトル
に対して45゜方向に移動するので、回折格子15の移
動精度が21/2 倍に高くなる。As described above, in the first embodiment, the parallel laser light is diffracted by the diffraction grating 15 and formed into an image near the reference reflection surface 19 by the lens 17 to be measured.
Only the first-order diffracted light is reflected and diffracted by the diffraction grating 15 again, and the spatial filter 23 extracts only the + 1st-order diffracted light on the return path with the + 1st-order diffracted light on the outward path and the + 1st-order diffracted light on the return path with the -1st-order diffracted light on the outward path. Since the diffraction grating 15 is moved in the grating vector direction at an initial position and a position rotated by 90 ° from the initial position, this is an apparatus for measuring the interference fringes by transmitting the light and interfering them.
The amount and direction of tilt of the image plane can be measured with twice the accuracy. In the second embodiment, since the diffraction grating 15 is moved in the direction of 45 ° with respect to the grating vector, the movement accuracy of the diffraction grating 15 is increased by a factor of 2 1/2 .
【0024】また、本実施例では回転格子15を相対的
に90゜回転させているが、その相対角は90゜でなく
てもよい。例えば、回折格子15を初期位置からα回転
させたときの倒れ量をΔα、β回転させたときの倒れ量
をΔβとすると、最大倒れ量dは式、 d=(Δα2 +Δβ2 )1/2 により求まる。このときの回転角θは式、 θ=tan-1S/C により求まる。なお、ここで、S=Δαcosα+Δβ
cosβ C=Δαsinα+Δβsinβ である。さらに、異なる次数の回折光を干渉させること
により、像面の倒れおよび諸収差を二次元、三次元的に
測定することが可能になる。Further, in the present embodiment, the rotating grating 15 is rotated by 90 ° relatively, but the relative angle may not be 90 °. For example, if the amount of tilt when the diffraction grating 15 is rotated α from the initial position is Δα, and the amount of tilt when β is rotated β is Δβ, the maximum amount of tilt d is given by the following equation: d = (Δα 2 + Δβ 2 ) 1 / Determined by 2 . The rotation angle θ at this time is obtained by the following equation: θ = tan −1 S / C. Here, S = Δαcosα + Δβ
cosβC = Δαsinα + Δβsinβ. Furthermore, by making diffracted lights of different orders interfere, it becomes possible to measure the tilt of the image plane and various aberrations two-dimensionally and three-dimensionally.
【0025】[0025]
【発明の効果】以上の通り本発明は、以上の通り本発明
は、回折格子を移動させて被測定レンズにより形成され
る干渉縞を測定するので、簡単に被測定レンズの像面の
倒れ量および倒れ方向を測定することができる。しかも
本発明によれば、異なる次数の回折光を干渉させること
により、像面の倒れ、および像面の状態を測定すること
もできる。As described above, according to the present invention, since the interference fringes formed by the lens to be measured are measured by moving the diffraction grating, the tilt amount of the image plane of the lens to be measured can be easily determined. And the falling direction can be measured. Moreover, according to the present invention, it is also possible to measure the tilt of the image plane and the state of the image plane by causing diffracted lights of different orders to interfere with each other.
【図1】本発明を適用した像面位置測定装置の一実施例
の光路図を示した図である。FIG. 1 is a diagram showing an optical path diagram of an embodiment of an image plane position measuring apparatus to which the present invention is applied.
【図2】同実施例における基準面付近の様子を拡大して
示す図である。FIG. 2 is an enlarged view showing a state near a reference plane in the embodiment.
【図3】本装置による干渉縞の様子を示す図である。FIG. 3 is a diagram showing a state of interference fringes by the present apparatus.
【図4】実施例1における回折格子の移動態様を説明す
る図である。FIG. 4 is a diagram illustrating a movement mode of a diffraction grating according to the first embodiment.
【図5】実施例2における回折格子の移動態様を説明す
る図である。FIG. 5 is a diagram illustrating a movement mode of a diffraction grating according to a second embodiment.
【図6】像面に曲りがある場合の基準反射面付近の像面
の様子を説明する図である。FIG. 6 is a diagram illustrating a state of an image surface near a reference reflection surface when the image surface has a curvature.
【図7】像面に倒れの外に収差などがある場合の様子を
示した図である。FIG. 7 is a diagram illustrating a state in which there is an aberration or the like in addition to the tilt on the image plane.
【図8】像面に倒れの外に収差などがある場合の様子を
3次元で示した図である。FIG. 8 is a three-dimensional diagram illustrating a state in which an aberration or the like is present in addition to the tilt on the image plane.
11 レーザ光源 13 ハーフミラー 15 回折格子 17 被測定レンズ 19 基準反射面 23 空間フィルタ 25 観測面 29 回折格子移動装置 31 撮像素子 33 画像処理装置 Reference Signs List 11 laser light source 13 half mirror 15 diffraction grating 17 lens to be measured 19 reference reflection surface 23 spatial filter 25 observation surface 29 diffraction grating moving device 31 image sensor 33 image processing device
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7,DB名) G01M 11/00 - 11/08 G01B 11/00 - 11/30 ──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. 7 , DB name) G01M 11/00-11/08 G01B 11/00-11/30
Claims (5)
光源と、 被測定レンズの前に配置され、前記測定光源から発した
測定光束を回折させる回折格子と、 前記被測定レンズの焦点位置またはその近傍に配置さ
れ、前記回折格子で回折して被測定レンズを透過した回
折光を反射する基準反射面と、 この基準反射面で反射され、前記被測定レンズ、前記回
折格子を介して合成された異なる次数の回折光により形
成される干渉縞を受光して画像データに光電変換する受
光手段と、 前記受光手段が光電変換した画像データに基づいて上記
被測定レンズの像面の状態を測定する測定手段と、 前記回折格子を移動させて上記受像手段上の干渉縞の位
相をシフトさせる回折格子移動手段と、を備えたことを
特徴とする像面測定装置。1. A measurement light source for irradiating a measurement light beam to a lens to be measured, a diffraction grating arranged in front of the measurement light lens to diffract a measurement light beam emitted from the measurement light source, and a focal position of the measurement lens or A reference reflection surface that is disposed in the vicinity thereof and reflects the diffracted light that has been diffracted by the diffraction grating and transmitted through the lens to be measured; and reflected by the reference reflection surface and synthesized through the lens to be measured and the diffraction grating. A light receiving unit that receives interference fringes formed by diffracted lights of different orders and photoelectrically converts the interference fringes into image data, and measures a state of an image plane of the lens to be measured based on the image data photoelectrically converted by the light receiving unit. An image plane measuring apparatus comprising: a measuring unit; and a diffraction grating moving unit that moves the diffraction grating to shift the phase of an interference fringe on the image receiving unit.
段は、前記回折格子をその格子ベクトルと直交しない方
向に移動することを特徴とする像面測定装置。2. An image plane measuring apparatus according to claim 1, wherein said diffraction grating moving means moves the diffraction grating in a direction not orthogonal to the grating vector.
段は、前記回折格子の格子ベクトルの向きを変えて、そ
れぞれの方向において格子ベクトルと直交しない方向に
移動させることを特徴とする像面測定装置。3. The image plane measurement method according to claim 2, wherein the diffraction grating moving means changes the direction of the grating vector of the diffraction grating and moves the diffraction grating in a direction not orthogonal to the grating vector in each direction. apparatus.
きにおける移動方向は同一であることを特徴とする像面
測定装置。4. The image plane measuring apparatus according to claim 3, wherein the directions of movement of the diffraction grating in each direction are the same.
て、干渉縞像画像入力手段は、異なる次数の回折光を干
渉させて干渉縞を測定する像面測定装置。5. An image plane measuring apparatus according to claim 1, wherein said interference fringe image input means measures interference fringes by causing diffracted lights of different orders to interfere with each other.
Priority Applications (1)
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JP06292294A JP3315806B2 (en) | 1993-04-12 | 1994-03-31 | Image plane measuring device |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP8440893 | 1993-04-12 | ||
JP5-84408 | 1993-04-12 | ||
JP06292294A JP3315806B2 (en) | 1993-04-12 | 1994-03-31 | Image plane measuring device |
Publications (2)
Publication Number | Publication Date |
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JPH06347368A JPH06347368A (en) | 1994-12-22 |
JP3315806B2 true JP3315806B2 (en) | 2002-08-19 |
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