JPS58150838A - Measuring apparatus for optical constant of lens - Google Patents

Abstract

PURPOSE:To make it possible to measure an optical constant of a lens simply and precisely in a short time, by detecting by an image sensor a distance between optical beams whose aperture is much enlarged through the lens. CONSTITUTION:A light source device 8, having a laser oscillator 9 and a slit mask 10, projects a pair of parallel optical beams 3 and 4 to a lens 1. The mask 10, which is prepared by applying non-transparent coating on the surface of a transparent base plate, has a pair of parallel slits 11A and 11B at a prescribed aperture 2a between them. The arrangement length of each photoelectric transfer element 13 and a distance l are selected so that an aperture 2b between beams 6 and 7 projected from the lens 1 is within the effective detection width of a light-receiving detector 12, and output signals from the detector 12 are supplied to a beam aperture measuring device 14. On the occasion, the detecting surface of the detector 12 receives lights each having an intensity distribution wherein two peaks appear corresponding to the images of the slits 11A and 11B. Then a clock pulse between corresponding sampling pulses is counted, and a refractive index distribution constant is calculated.

Description

【発明の詳細な説明】 本発明はレンズの光学窓′＃測定装置に関し、特に屈折
率分布型レンズの屈折率分布定数を簡便に測定するのに
好適な光学定数測定装置に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical window measuring device for a lens, and more particularly to an optical constant measuring device suitable for easily measuring the refractive index distribution constant of a gradient index lens.

屈折率分布型レンズは、中心軸上の屈折率ｎｏを最大と
して中心軸から半径方向Ｋｒの距離での屈折率ｎ（ｒ）
が、 ｎ２（ｒ）　−ｎ２ｏ　（／　−（ｇｒ）”　）　　−
−−−−−・・（１）の式で表わされる屈折率分布をも
っている両端面が平行平面の円柱状のレンズである。A gradient index lens has a refractive index n(r) at a distance Kr in the radial direction from the central axis, with the maximum refractive index no on the central axis.
But, n2(r) −n2o (/ −(gr)” ) −
-------It is a cylindrical lens with a refractive index distribution expressed by the formula (1), and both end faces are parallel planes.

このような屈折率分布型レンズでは屈折率分布定数ｇに
よってレンズの諸光学特性が定まり、またこの分布定数
ｇと他の種々の光学特性値との相関関係が詳細に理論解
析されているので分布定数ｇを個々のレンズついて求め
ておけば、屈折率分布型レンズを用いて光学系を組む場
合に非常に有用である。In such a refractive index distribution type lens, various optical properties of the lens are determined by the refractive index distribution constant g, and the correlation between this distribution constant g and various other optical characteristic values has been theoretically analyzed in detail. Determining the constant g for each lens is extremely useful when constructing an optical system using gradient index lenses.

従来においては、上記の分布定数ｇを求める場合顕微鏡
で画像を観察しながらレンズの焦点位置を求め、これを
もとに上記分布定数ｇを算出するという方法によってい
たため測定に非常に手間がかかり、また屈折率分布型レ
ンズは一般に直径がコ＋ａｍφ　以下といった微小なも
のであるため作業に熟練を要するとともにあまり高精廖
な測定が行なえないという問題があった。Conventionally, when determining the above distribution constant g, the method was to find the focal position of the lens while observing the image with a microscope, and then calculate the above distribution constant g based on this, which was very time-consuming. In addition, since the gradient index lens is generally very small with a diameter of less than 0.0 mm, there is a problem in that it requires skill to operate and it is not possible to perform highly precise measurements.

本発明は上述の従来の問題点を解決し、屈折率分布定数
等のレンズ光学定数を極めて短時間で簡便にしかも高精
度に測定することのできるレンズの光学定数測定装置を
提供することを目的としている。SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a lens optical constant measurement device that can measure lens optical constants such as refractive index distribution constants easily and with high precision in an extremely short time. It is said that

本発明の装置は、レンズの片面側の光軸を挾む対称位置
に互いにほぼ平行な一対の光ビームを投射する光源ハレ
ンズ他面から出た後、拡散するこれら光ビームを横切っ
て配列された多数の微小な光電変換受光素子群と、ピー
ク光量を示す前記受光素子間の距離を求める信号処理回
路で構成されるＯ 以下本発明を図面に示した実施例について説明する。The device of the present invention has a light source that projects a pair of light beams substantially parallel to each other at symmetrical positions sandwiching the optical axis on one side of the lens, and a light source that is arranged across these light beams to diffuse after exiting from the other side of the lens. It is composed of a large number of small photoelectric conversion light-receiving element groups and a signal processing circuit for determining the distance between the light-receiving elements indicating the peak light intensity.Embodiments of the present invention shown in the drawings will be described below.

第７図は本発明装置の測定原理を示す模式図であり、ｌ
は前述（１）式゛で表わされる屈折率分布をもつ透明の
ガラスあるいは合成樹脂からなる屈折率分布型レンズで
その長さｚＯをダ分の１周期長（ピッチ）よりも若干短
かくしである。いまこのレンズｌの片端面／Ａの光軸２
から等間隔ａだけ離れた対称位置に互いに平行な光線Ｊ
、ｌＩを入射させるとこれらの光線はレンズｌ内をサイ
ンカーブを描いて進行し、レンズ／の他端面／Ｂからｔ
ａｎθ−ｎｏ・ｇ−ａ−８ｉｎ（ｇＺｏ）の傾きをもっ
て出射されレンズ面からｋだけ離れた位置ムに集束した
後、拡散する。FIG. 7 is a schematic diagram showing the measurement principle of the device of the present invention.
is a refractive index distribution type lens made of transparent glass or synthetic resin with a refractive index distribution expressed by the above-mentioned formula (1), and its length zO is a comb slightly shorter than one period length (pitch). . Now, one end surface of this lens l/optical axis 2 of A
Rays J parallel to each other at symmetrical positions spaced apart by an equal distance a from
, lI, these rays travel inside the lens l drawing a sine curve, and from the other end surface /B of the lens / t
The light is emitted with an inclination of an θ-no·ga-8 in (gZo), is focused at a position k away from the lens surface, and then diffuses.

そこで焦点Ａからｌたけ離れた地点に仮想スクリーンｊ
をレンズ光軸−に垂直に置き、このスクリーンｊ上に投
影された両出射ビーム６．７間の距離を−すとすると距
離ｌがｋＫ比して充分大であるとき次の関係式が成立す
る。Therefore, a virtual screen j is placed at a point l away from the focal point A.
is placed perpendicular to the lens optical axis -, and if the distance between both output beams 6.7 projected onto this screen j is -, then the following relational expression holds when the distance l is sufficiently large compared to kK. do.

ｂ／ｌ−ｎｏ−ｇ−ａｓｉｎ（ｇＺｏ）　＋−＋・＋−
＊＋（Ｊ）したがって、レンズ中心の屈折率ｎｏをアツ
ベ屈折計、浸液法等周知の屈折率測定方法で測定し、第
１図中のａ、ｌおよびｚＯを予め一定値に設定か しておけば、あとは仮想スクリーン上瓢での両ビーム間
距離２ｂを実測するだけで上記（コ）式から屈折率分布
定数ｇを求めることができる。b/l-no-g-asin (gZo) +-+・+-
*+(J) Therefore, measure the refractive index no at the center of the lens using a well-known refractive index measurement method such as an Atsube refractometer or immersion method, and set a, l, and zO in Figure 1 to constant values in advance. Once this is done, the refractive index distribution constant g can be obtained from the above equation (c) simply by actually measuring the distance 2b between the two beams on the virtual screen.

このようにして１つの製造ロフト内の代表的なレンズ試
料について測定された分布定数ｇは、その製造ロフト内
のすべての製品レンズについてレンズ長によらず適用す
ることができる。The distribution constant g thus measured for a representative lens sample within one manufacturing loft can be applied to all product lenses within that manufacturing loft, regardless of lens length.

上記の測定原理に基づく本発明装置の一例を第一図に示
す。An example of the apparatus of the present invention based on the above measurement principle is shown in FIG.

第一図においてｌはレンズｌに一対の平行な光ビーム３
．りを投射するための光源装置であり、レーザー発振器
９および、この発振器９とレンズｌとの間に置いたスリ
ットマスクＩＯで構成される。In Figure 1, l is a pair of parallel light beams 3 to lens l.
．． This is a light source device for projecting light, and is composed of a laser oscillator 9 and a slit mask IO placed between the oscillator 9 and a lens l.

スリットマスクＩＯは透明基板面に金属薄膜等の不透光
被覆を施すとともに前述した所定間隔２ａをおいて一対
の平行な透光スリン）　／／Ａ、／／Ｂを設けたもので
ある。The slit mask IO has a transparent substrate surface coated with a non-light-transmitting coating such as a thin metal film, and a pair of parallel light-transmitting slits (//A, //B) are provided at a predetermined interval 2a as described above.

透光スリン）　／／Ａ−／／Ｂは例えば幅を７０μｍと
し、間隔−ａはレンズ周辺部の収差による悪影響を避け
るためレンズ径が／〜、２　ＩＩＩ／Ｉｌｌφの場合に
１００μ痰前後にとるのがよい。For example, the width of //A-//B is set to 70 μm, and the interval -a is set to around 100 μm when the lens diameter is /~, 2III/Illφ to avoid adverse effects due to aberrations at the lens periphery. It is better.

そしてレンズ／の焦点から適宜距離ｌ隔てた地点に受光
検出器／２を配置する。Then, the light receiving detector /2 is arranged at a point separated by an appropriate distance l from the focal point of the lens /.

受光検出器／コは第３図に示すように微小な光電変換素
子／３を一次元的に多数配列して構成されているもので
あり、素子／３の配列方向をレンズ／からの両出射ビー
ム６．７を結ぶ線と一致させ且つレンズ光軸−に直交さ
せて受光検出器／Ｊを配置する。As shown in Fig. 3, the light receiving detector is constructed by arranging a large number of minute photoelectric conversion elements in one dimension, and the arrangement direction of the elements is aligned with both outputs from the lens. The light receiving detector /J is arranged to coincide with the line connecting the beams 6 and 7 and to be perpendicular to the lens optical axis.

このとき両出射ビーム乙、７間の間隔コｂが検出器ｌ−
の有効検出幅内に入るように光電変換素子１３の配列長
さおよび距離ｌを選定する。At this time, the distance b between both output beams B and 7 is the detector l-
The array length and distance l of the photoelectric conversion elements 13 are selected so as to fall within the effective detection width of .

具体的数値例で示すならばｋをｊＯＯμ簡、ｌをｉ　ｓ
　ｏ　＊／ｍ程度とし、△Ｓ−約コｌμｌの間隔でよｌ
−個の１０μｍ前後の大きさの７オトセンサー／Ｊを並
べた受光検出器ｌコを使用する。To give a concrete numerical example, k is jOOμ, l is i s
o */m, and spaced at intervals of △S - about 1 μl.
- A photodetector consisting of 7 sensors/J each with a size of around 10 μm is used.

受光検出器ｌコから出力される電気信号はビーム間隔測
定器ｌｌＩに入る。The electrical signal output from the photodetector I enters the beam distance measuring device III.

このビーム間隔測定器ｌダは第３図にブロック図で示す
ような回路構成となっている。This beam distance measuring device LD has a circuit configuration as shown in a block diagram in FIG.

すなわち充分に短かい一定時間間隔△ｔのクロックパル
スを発生するクロックパルス発生回路１ｊ１７０ツ７ この各Ｐ〒ｉパルス毎に次々と各素子１３の発生電力を
出力する切換回路（図外）、この発生電圧を定電１１／
７から発生する基準電圧ｖｔｈと比較するコンパレータ
＃、、クロック周期△ｔよゝり長い時定数Ｔ　（Ｔ＞△
ｔ）をもつ単安定マルチバイブレータ／Ｉ、これに続く
トリガ７リツプ７０ツブ回路ｌり、このフリップフロッ
プ回路１９からの信号およびクロックパルス発生回路／
ｊからの信号の論理積をとるＡＮＤ回路回路コバ１バル
ス力ウンタコ／よびカウントしたパルス数を表示する表
示器−２を備えている。That is, a clock pulse generation circuit 1j170 which generates clock pulses with a sufficiently short constant time interval Δt, a switching circuit (not shown) which outputs the generated power of each element 13 one after another for each P〒i pulse, and this Constant voltage 11/
Comparator #, which is compared with the reference voltage vth generated from 7, has a time constant T longer than the clock period △t (T>△
A monostable multivibrator /I with t), followed by a trigger 7-lip 70-tube circuit, a signal from this flip-flop circuit 19 and a clock pulse generation circuit /I.
The circuit is provided with an AND circuit for calculating the AND of the signals from j, and a display 2 for displaying the number of pulses counted.

上記測定装置の作用について説明すると、マスクＩＯの
透光スリブ）　／／Ａ、／／Ｂから出た一対の平行なレ
ーザビーム３．ダは一方の端面がらレンズ／に入射し、
レンズ／の他端面からビーム６゜７として出射した後、
受光検出器／コに入光する。To explain the operation of the above measurement device, a pair of parallel laser beams 3. Da enters the lens/ from one end face,
After exiting as a beam 6°7 from the other end surface of the lens,
Light enters the light receiving detector.

すなわち受光検出器／コの検出面では透光スリブ）／／
Ａ、／／Ｈの像に対応して第１図（Ａ）に示すように−
すの間隔をおいて２つのピークの表われる強度分布をも
った光が受光される。In other words, the detection surface of the light-receiving detector is a transparent sleeve) //
As shown in FIG. 1 (A), corresponding to the images of A and //H, -
Light is received with an intensity distribution in which two peaks appear at an interval of 1.

するとクロックパルス発生回路１５からのクロックパル
スに乗って△ｔの時間間隔で第ｑ図（Ｂ）　Ｋ示すよう
に各光電変換素子／３から受光量に比例した電気信号が
次々とパルス出力される。Then, on the clock pulse from the clock pulse generation circuit 15, electric signals proportional to the amount of light received are outputted as pulses one after another from each photoelectric conversion element/3 at time intervals of △t, as shown in Fig. q (B) K. .

この信号と閾値ｖｔｈとがコンパレータｌ≦で比較され
、このｖｔｈ　を越えた信号のみがコンパレータｌ乙か
ら出力する（第ダ図Ｃ）。This signal and a threshold value vth are compared by a comparator l≦, and only the signal exceeding this vth is output from the comparator lB (FIG. 1C).

次に△ｔより長い遅延を単安定マルチバイブレータ／ｌ
でかけると第４図（Ｄ）で示されるパルスが得られる。Next, set the delay longer than △t to monostable multivibrator/l
When the pulse is applied, the pulse shown in FIG. 4(D) is obtained.

このパルスの立ち上がりでトリガフリップフロップｌり
をトリガすると前述した両ビーム４．７による光強度ピ
ークの間隔−すに対応するｔｂのパルス幅をもつサンプ
リングパルスが得られる（第参図Ｅ）。When the trigger flip-flop is triggered at the rising edge of this pulse, a sampling pulse having a pulse width of tb corresponding to the interval between the light intensity peaks of the two beams 4.7 described above is obtained (see Figure E).

このサンプリングパルスの間にクロックパルスコ３の発
生数ｍをカウンターｌで計数してディジタル表示器コ２
に表示させる。During this sampling pulse, the number m of clock pulses 3 generated is counted by a counter 1 and displayed on a digital display 2.
to be displayed.

そしてΔ５Ｘｎｔ−Ｊｂの関係及び前述の（コ）式から
、 ΔＳ−ｍ−コ１−ｎｏ　ａａ＊ｇ　＠　ｓｉｎ　（ｇ　
ｚＯ）　”・（Ｊ）と表わすことができ、上記のように
してパルス数ｍを電気的にカウントすることにより（３
）式から計測について説明したが、本発明の装置は一般
のレンズの焦点距離測定に使用することもできる。Then, from the relationship of Δ5Xnt-Jb and the above equation (c), ΔS-m-ko1-no aa*g @ sin (g
zO) ”・(J), and by electrically counting the number of pulses m as described above, it can be expressed as (3
Although the measurement has been explained using the equation ), the device of the present invention can also be used to measure the focal length of a general lens.

この場合、焦点距離ｆは ｆ−コａ−ｌ／△５−１１　−・−−−−−（ｌｌ）か
ら求めることができる。In this case, the focal length f can be determined from f-coal/Δ5-11 -.----(ll).

本発明によれば機械的な微動調整が不要でありレンズを
通して間隔が大きく拡大された光ビーム間の距離をイメ
ージセンサ−で電気的に検出するため、従来の光学像観
察による方法に比べて測定時間が著しく短縮されるとと
もに、簡便かつ安価な装置で収差の影響を受けずに高精
度で屈折率分布定数等のレンズの光学定数を測定するこ
とができる。According to the present invention, there is no need for mechanical fine adjustment and the distance between the light beams, whose spacing has been greatly expanded through a lens, is electrically detected using an image sensor. In addition to significantly shortening the time, it is possible to measure optical constants of lenses such as refractive index distribution constants with high precision without being affected by aberrations using a simple and inexpensive device.

【図面の簡単な説明】[Brief explanation of the drawing]

図は本発明の実施例を示し、第１図は本発明の測定原理
を示す模式図、第２図は本発明装置の一例を示す斜視図
、第３図は第一図の装置における信号処理系を示すブロ
ック図、第４図（Ａ）〜（Ｇ）は第３図の信号処理系に
おける信号処理の方法を段階的に示す図である。The figures show an embodiment of the present invention, Fig. 1 is a schematic diagram showing the measurement principle of the invention, Fig. 2 is a perspective view showing an example of the apparatus of the invention, and Fig. 3 is signal processing in the apparatus of Fig. 1. Block diagrams showing the system, FIGS. 4(A) to 4(G) are diagrams showing step-by-step the signal processing method in the signal processing system of FIG. 3.

Claims (1)

【特許請求の範囲】[Claims] レンズの片面側の光軸を挾む対称位置に互いにほぼ平行
な一対の光ビームを投射する光源を設け、レンズ他面か
ら出た後、拡散するこれら光ビームを横切って多数の微
小な光電変換受光素子を配列し、ピーク光量を示す受光
素子間の距離を求める信号処理回路、を設けたことを特
徴とするレンズの光学定数測定装置。A light source that projects a pair of nearly parallel light beams is installed at symmetrical positions sandwiching the optical axis on one side of the lens, and after exiting from the other side of the lens, a large number of minute photoelectric conversions are carried out across these diffused light beams. 1. An optical constant measuring device for a lens, comprising a signal processing circuit for arranging light-receiving elements and determining a distance between the light-receiving elements indicating a peak light amount.