JP5991230B2 - Phase difference measuring method and apparatus - Google Patents
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本発明はＰＥＴ（Polyethylene terephthalate）、ＰＥＮ（Polyethylene naphthalate）、ＰＩ（Polyimide）やＰＣ（Polycarbonate）等の樹脂フィルム、特に高位相差樹脂フィルムの位相差と光学主軸（遅相軸又は進相軸）方位を測定する方法と装置に関するものである。 The present invention relates to the phase difference and optical principal axis (slow axis or fast axis) orientation of resin films such as PET (Polyethylene terephthalate), PEN (Polyethylene naphthalate), PI (Polyimide), and PC (Polycarbonate), particularly high retardation resin films. The present invention relates to a method and an apparatus for measuring.
液晶表示装置に使用される反射防止フィルム、配向フィルム、偏光フィルム、位相差フィルムなどのように様々な光学的効果を与える光学フィルムについては、位相差と光学主軸方位が管理されている。 For optical films that give various optical effects such as antireflection films, alignment films, polarizing films, and retardation films used in liquid crystal display devices, the retardation and optical principal axis orientation are managed.
近年、液晶表示装置は、携帯電話やタブレット端末等のモバイル機器の表示画面に限らず、カーナビゲーション装置の表示画面としても多用されている。これらの表示画面にはタッチパネルが付いているものが多い。タッチパネル自体の構成部材として又は表面の保護フィルムとして、主にＰＥＴフィルムが使用されることが多くなっている。 In recent years, liquid crystal display devices are frequently used as display screens for car navigation devices as well as display screens for mobile devices such as mobile phones and tablet terminals. Many of these display screens have a touch panel. A PET film is mainly used as a constituent member of the touch panel itself or as a protective film for the surface.
ＰＥＴフィルムを使用したこれらの表示画面を、偏光サングラスを通して見たときに、虹模様が見えて見づらくなる現象がある。ＰＥＴフィルムは、一般的に逐次二軸延伸法で製造され、配向状態が幅方向において大きく変化する、いわゆるボーイング現象を示すことは広く知られている。そのため、幅広のＰＥＴフィルムから所定形状に切り出す、いわゆる取り位置によって位相差や光学主軸方位が異なり、それが虹模様の見え方に大きく影響する。そのような場合の視認性を改善するためには、タッチパネルの構成部材や保護フィルムとして使用されるＰＥＴフィルムについても、光学フィルムと同様に位相差と光学主軸方位を管理する必要がある。タッチパネルの構成部材や保護フィルムとしてＰＥＴフィルム以外のフィルムが使用される場合にも同様の問題が生じる。 When these display screens using a PET film are viewed through polarized sunglasses, there is a phenomenon in which a rainbow pattern appears and is difficult to see. It is widely known that a PET film is generally manufactured by a sequential biaxial stretching method and exhibits a so-called bowing phenomenon in which the orientation state changes greatly in the width direction. For this reason, the phase difference and the optical principal axis orientation differ depending on the so-called removal position cut out from a wide PET film, which greatly affects the appearance of the rainbow pattern. In order to improve the visibility in such a case, it is necessary to manage a phase difference and an optical principal axis direction similarly to an optical film also about the PET film used as a structural member of a touch panel or a protective film. The same problem occurs when a film other than a PET film is used as a constituent member or a protective film of a touch panel.
さらに、このような問題はタッチパネルに使用されるフィルムに限らず、他の液晶表示装置に使用されるフィルムについても同様に生じる。 Further, such a problem occurs not only in the film used for the touch panel but also in the film used for other liquid crystal display devices.
本発明は、そのような位相差と光学主軸方位を管理する必要のあるフィルムを測定対象とする。 In the present invention, a film that needs to manage such retardation and optical axis orientation is a measurement object.
フィルムの位相差を測定する従来の方法としては、図９のような構成の測定装置が使用される。複数の波長を含む光を発する光源装置１からの測定光をライトガイド２で集光レンズ３に導いて平行光にして被測定物５に照射する。集光レンズ３と被測定物５の間にバンドパスフィルタ７を配置して測定波長を選択するとともに、偏光子４を配置して直線偏光にする。被測定物５を透過した測定光を検光子６を通して光検出器８に導いて透過光量を検出する。光検出器８の検出信号は増幅器及びＡ／Ｄ変換器を含む電気回路１０によりデジタル信号に変換して演算処理部１１に導く。このとき、被測定物５の前後に配置した偏光子４と検光子６の透過軸を同じ方向に保ちながら偏光子４と検光子６を一回転したときの光検出器８による検出光強度の変化から、被測定物５の位相差と光学主軸方位を求める。これを平行ニコル回転法という。 As a conventional method for measuring the retardation of a film, a measuring apparatus having a configuration as shown in FIG. 9 is used. The measurement light from the light source device 1 that emits light including a plurality of wavelengths is guided to the condensing lens 3 by the light guide 2 to be collimated, and is irradiated on the object to be measured 5. A bandpass filter 7 is arranged between the condenser lens 3 and the object to be measured 5 to select a measurement wavelength, and a polarizer 4 is arranged to make linearly polarized light. The measurement light transmitted through the object to be measured 5 is guided to the photodetector 8 through the analyzer 6 to detect the amount of transmitted light. The detection signal of the photodetector 8 is converted into a digital signal by an electric circuit 10 including an amplifier and an A / D converter and led to the arithmetic processing unit 11. At this time, the intensity of light detected by the photodetector 8 when the polarizer 4 and the analyzer 6 are rotated once while the transmission axes of the polarizer 4 and the analyzer 6 arranged in front of and behind the object to be measured 5 are kept in the same direction. From the change, the phase difference and the optical principal axis direction of the DUT 5 are obtained. This is called the parallel Nicol rotation method.
その検出光強度変化は（１）式で表され、図１０のようになる。
ここで、Ｉoは被測定物５への入射光の強度、θは偏光子・検光子の回転角、ζは振幅透過率比、φは被測定物５の光学主軸の方位、Ｒは被測定物５の位相差、λは測定波長である。
The change in the detected light intensity is expressed by equation (1) as shown in FIG.
Here, Io is the intensity of incident light on the object 5 to be measured, θ is the rotation angle of the polarizer / analyzer, ζ is the amplitude transmittance ratio, φ is the orientation of the optical principal axis of the object 5 to be measured, and R is the object to be measured. The phase difference λ of the object 5 is the measurement wavelength.
（１）式に含まれる未知数は、Ｉo、ζ、Ｃ0およびφの４つであるが、φは検出光強度図形の最大直径の方位として最初に求まるので、残りの未知数は３つである。それらは、検出光強度のθ＝φ、φ＋４５°、φ＋９０°の値から連立方程式を解いて容易に求めることができる。Ｃ0が求まれば、（２）式よりその測定波長における位相差Ｒは（３）式で計算できる。
ここで、ｍは次数で１，２，３，…の値をとり、Ｒの絶対値を得るにはｍの値を定める必要がある。
There are four unknowns included in the equation (1), Io, ζ, C 0 and φ. However, since φ is first obtained as the direction of the maximum diameter of the detected light intensity diagram, the remaining unknowns are three. . They can be easily obtained by solving simultaneous equations from the detected light intensity values of θ = φ, φ + 45 °, φ + 90 °. If C 0 is obtained, the phase difference R at the measurement wavelength can be calculated by the equation (3) from the equation (2).
Here, m takes the value of 1, 2, 3,..., And it is necessary to determine the value of m in order to obtain the absolute value of R.
一般的に位相差Ｒは波長依存性があり、それをＲ（λ）とすると（４）式のセルマイヤーの近似式で表すことができる。
Ａ，Ｂ，Ｃは定数である。
In general, the phase difference R is wavelength-dependent, and if it is R (λ), it can be expressed by a Cellmeier approximate expression (4).
A, B, and C are constants.
基準波長λoに対する位相差の分散比率Ｒ（λ）／Ｒ（λo）を考えると、分散比率の波長依存性は材料ごとにほぼ１つになる。このことを、例えばＰＥＴフィルムについて示すと、種々の厚さのＰＥＴフィルムの位相差Ｒ（λ）は図７（Ａ）のように位相差の絶対値が異なっているが、基準波長λo（たとえば５９０ｎｍ）に対する分散比率Ｒ（λ）／Ｒ（λo）の波長依存性は図７（Ｂ）のようにほぼ１つに重なる。
従来法で１０００ｎｍ以上の高位相差を測定する場合は、この特性を利用して、図９に示されるようにバンドパスフィルタ７を切り換えて、例えば６つの異なる測定波長で平行ニコル回転法によって測定し、（３）式から得られる波長ごとの位相差候補Ｒim(ただし、ｉは波長、ｍは次数)を並べ、それらの数値の中から分散比率の波長依存性がその材料特有のものに最も近くなるＲimの組を見つけ出す。この演算は演算処理部１１により実行される。この方法により、市販されている王子計測機器製の位相差測定装置ＫＯＢＲＡ−ＷＲでは、位相差が５０００ｎｍ程度以下であれば正確に求めることができる。
Considering the dispersion ratio R (λ) / R (λo) of the phase difference with respect to the reference wavelength λo, the wavelength dependence of the dispersion ratio is almost one for each material. For example, the PET film having various thicknesses has a phase difference R (λ) having different absolute values as shown in FIG. 7A, but the reference wavelength λo (for example, The wavelength dependence of the dispersion ratio R (λ) / R (λo) with respect to 590 nm substantially overlaps one as shown in FIG.
When a high phase difference of 1000 nm or more is measured by the conventional method, the bandpass filter 7 is switched as shown in FIG. 9 using this characteristic, and the measurement is performed, for example, by the parallel Nicol rotation method at six different measurement wavelengths. , (3) The phase difference candidates Rim (where i is the wavelength and m is the order) for each wavelength obtained from the equation (3) are arranged, and the wavelength dependence of the dispersion ratio is the closest to that specific to the material among these numerical values. Find a set of Rim. This calculation is executed by the calculation processing unit 11. According to this method, in the commercially available phase difference measuring device KOBRA-WR manufactured by Oji Scientific Instruments, it can be accurately obtained if the phase difference is about 5000 nm or less.
本発明は、広範囲の位相差のフィルムに適用でき、平行ニコル回転法とは異なる方法により位相差と光学主軸方位を測定する方法と装置を提供することを目的とするものである。 An object of the present invention is to provide a method and an apparatus which can be applied to a film having a wide range of retardation, and which measure the retardation and optical principal axis orientation by a method different from the parallel Nicol rotation method.
本発明の位相差測定方法は、被測定物を挟んで偏光子と検光子を配置して偏光子の透過軸と検光子の透過軸のうち一方を固定し他方を回転させ、偏光子を通して被測定物に測定光を照射し、被測定物を透過した測定光を検光子を通して光検出器で検出する測定装置を用い、以下のステップＳ０からＳ３により被測定物の位相差を求める。
（Ｓ０）前記測定装置から互いに異なる複数の波長での検出信号を取り込む。
（Ｓ１）取り込んだ複数の波長λiごとの検出光強度に基づき、基準方向に対する被測定物の透過光の楕円率（α／β）iと楕円方位角Ψiを算出し、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘi、Ｙi）を求める。
（Ｓ２）シミュレーションにより、基準波長λoでの位相差Ｒoを変化させながら複数の測定波長λiごとの透過光の楕円率（α／β）isと楕円方位角Ψisを求め、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘiｓ、Ｙiｓ）を求める。
（Ｓ３）ポアンカレ球赤道面の計算で求めた複数の点の座標（Ｘiｓ、Ｙiｓ）について、同じ波長の実測点の座標（Ｘi、Ｙi）に最も近くなるときの基準波長λoでの位相差Ｒoを被測定物の位相差とする。
In the phase difference measurement method of the present invention, a polarizer and an analyzer are arranged with an object to be measured interposed therebetween, one of the transmission axis of the polarizer and the transmission axis of the analyzer is fixed, the other is rotated, and the object is passed through the polarizer. Using a measurement device that irradiates the measurement object with measurement light and detects the measurement light transmitted through the measurement object with an optical detector through an analyzer, the phase difference of the measurement object is obtained by the following steps S0 to S3.
(S0) Capture detection signals at a plurality of different wavelengths from the measuring device.
(S1) Calculate the ellipticity (α / β) i and the elliptical azimuth angle ψi of the transmitted light of the measured object with respect to the reference direction based on the detected light intensities for each of the plurality of wavelengths λi, and based on these values The coordinates (Xi, Yi) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength are obtained.
(S2) By simulation, the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light for each of the plurality of measurement wavelengths λi are obtained while changing the phase difference Ro at the reference wavelength λo, and based on these values The coordinates (Xis, Yis) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength are obtained.
(S3) With respect to the coordinates (Xis, Yis) of a plurality of points obtained by calculation of the Poincare sphere equatorial plane, the phase difference Ro at the reference wavelength λo when closest to the coordinates (Xi, Yi) of the measured point of the same wavelength Is the phase difference of the object to be measured.
ここで、基準方向とは偏光子又は検光子の回転のスタート位置になるように任意に設定した方向である。オンライン測定装置の場合には被測定部が移動する方向を装置の基準方向とすると、基準方向の一例は装置の基準方向であり、図１１では０°方向である。基準方向としては装置の基準方向から４５°の方向のように他の方向を用いることもできる。 Here, the reference direction is a direction arbitrarily set so as to be the starting position of rotation of the polarizer or analyzer. In the case of an on-line measuring apparatus, if the direction in which the measured part moves is the reference direction of the apparatus, an example of the reference direction is the reference direction of the apparatus, which is the 0 ° direction in FIG. As the reference direction, other directions such as a direction of 45 ° from the reference direction of the apparatus can be used.
基準波長λoは複数の測定波長λiに対して任意に設定した波長である。基準波長λoは分散比率Ｒ（λ）／Ｒ（λo）を算出するときの基準になる波長であり、任意に設定することができるが、品質管理で光学的な測定を行う波長領域の波長に設定するのが好ましい。その一例は、例えば５９０ｎｍである。 The reference wavelength λo is a wavelength arbitrarily set for a plurality of measurement wavelengths λi. The reference wavelength λo is a wavelength that serves as a reference when calculating the dispersion ratio R (λ) / R (λo), and can be set arbitrarily. It is preferable to set. One example is 590 nm, for example.
本発明の位相差測定装置は、実施例を示す図１を参照して示すと、光源からの測定光が偏光子から検光子を経て光検出器に入射するように、かつ互いに異なる複数の波長λiで測定を行うように構成された光学系を有し、偏光子の透過軸と検光子の透過軸のうち一方が固定され他方が回転されるように構成され、偏光子と検光子の間に被測定物が配置される測定部（１００）、及び測定部（１００）からの複数波長λiでの検出信号を取り込んで被測定物の位相差を求める演算処理部（１１）を備えている。 The phase difference measuring apparatus of the present invention is shown in FIG. 1 showing the embodiment. When the measuring light from the light source enters the photodetector through the polarizer through the analyzer, the phase difference measuring apparatus has a plurality of different wavelengths. It has an optical system configured to perform measurement at λi, and is configured such that one of the transmission axis of the polarizer and the transmission axis of the analyzer is fixed and the other is rotated, and between the polarizer and the analyzer. A measurement unit (100) in which the measurement object is arranged, and an arithmetic processing unit (11) for obtaining the phase difference of the measurement object by taking in detection signals at a plurality of wavelengths λi from the measurement unit (100). .
演算処理部（１１）は、偏光解析部（１１０）、位相差補正部（１１３）、偏光特性算出部（１１１）及びマッチング部（１１２）を備えている． The arithmetic processing unit (11) includes a polarization analysis unit (110), a phase difference correction unit (113), a polarization characteristic calculation unit (111), and a matching unit (112).
偏光解析部（１１０）は、波長λiごとの検出光強度から回転検光子法又は回転偏光子法の原理に基づいて楕円偏光の楕円率（α／β）i及び楕円方位角Ψiを算出し、さらにそれらの楕円率と楕円方位角に対応する偏光状態をポアンカレ球赤道面に図示したときの点の座標（Ｘi、Ｙi）を求める。 The ellipsometer (110) calculates ellipticity (α / β) i and elliptic azimuth angle ψi of elliptically polarized light based on the principle of the rotational analyzer method or the rotational polarizer method from the detected light intensity for each wavelength λi, Further, the coordinates (Xi, Yi) of the points when the polarization states corresponding to the ellipticity and the elliptical azimuth are illustrated on the Poincare sphere equatorial plane are obtained.
位相差補正部（１１３）は、被測定物の位相差の波長分散特性を保持して、その波長分散特性に基づいて基準波長λoでの位相差Ｒoを前記複数の各波長λiでの位相差Ｒiに補正する。 The phase difference correction unit (113) holds the wavelength dispersion characteristic of the phase difference of the object to be measured, and calculates the phase difference Ro at the reference wavelength λo based on the wavelength dispersion characteristic as the phase difference at each of the plurality of wavelengths λi. Correct to Ri.
偏光特性算出部（１１１）は、シミュレーションにより、基準波長λoでの位相差Ｒoを変化させながら複数の測定波長λiごとの透過光の楕円率（α／β）isと楕円方位角Ψisを求め、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘis、Ｙis）を算出する。 The polarization characteristic calculator (111) obtains the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light for each of the plurality of measurement wavelengths λi by changing the phase difference Ro at the reference wavelength λo by simulation, The coordinates (Xis, Yis) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength based on those values are calculated.
マッチング部（１１２）は、偏光特性算出部（１１１）による計算結果の点の座標（Ｘis、Ｙis）の中から実測で得られた波長λiごとの点の座標（Ｘi、Ｙi）に最も近くなるときの基準波長λoでの位相差Ｒoを求めてそれを被測定物の位相差とする。 The matching unit (112) is closest to the point coordinates (Xi, Yi) for each wavelength λi obtained by actual measurement from the coordinates (Xis, Yis) of points calculated by the polarization characteristic calculation unit (111). The phase difference Ro at the reference wavelength λo is obtained and used as the phase difference of the object to be measured.
本発明によれば、広範囲の位相差のフィルムについて、平行ニコル回転法とは異なる方法により位相差と光学主軸（遅相軸又は進相軸）方位を測定することができる。 According to the present invention, it is possible to measure a phase difference and an optical principal axis (slow axis or fast axis) direction by a method different from the parallel Nicol rotation method for a film having a wide range of retardation.
一実施形態では、ステップＳ２でのシミュレーションは、ＯＰＴＩＭＡ法により偏光板に位相差板１枚が貼合された状態での透過光の楕円率と楕円方位角を求める計算手法である。その際の計算条件として被測定物に対して基準方向の直線偏光が照射されるものとし、さらに被測定物の位相差値を波長λiごとに補正された変数Ｒiとし、光学主軸方位を変数φとして、基準波長λoでの位相差Ｒoを所定の範囲にわたって、所定の刻みで変化させながら波長λiごとの楕円率（α／β）isと楕円方位角Ψisとを求める。光学主軸方位は基準方向からの値である。光学主軸は遅相軸と進相軸の２つがあるので、いずれを光学主軸としてもよい。 In one embodiment, the simulation in step S2 is a calculation method for obtaining the ellipticity and elliptical azimuth of transmitted light in a state where one retardation plate is bonded to a polarizing plate by the OPTIMA method. As a calculation condition at that time, the linearly polarized light in the reference direction is irradiated to the object to be measured, and the phase difference value of the object to be measured is a variable Ri corrected for each wavelength λi, and the optical principal axis direction is a variable φ. As described above, the ellipticity (α / β) is and the elliptical azimuth angle ψis for each wavelength λi are obtained while changing the phase difference Ro at the reference wavelength λo over a predetermined range in predetermined increments. The optical principal axis direction is a value from the reference direction. Since there are two optical main axes, a slow axis and a fast axis, either one may be used as the optical main axis.
一実施形態では、ステップＳ０は複数の波長での検出信号を取り込むためにバンドパスフィルタを使用して波長を選択するものである。そして、ステップＳ２でのシミュレーションではステップＳ０でのバンドパスフィルタの分光スペクトルを考慮して波長λiごとの検出光強度を算出し、その算出された検出光強度に基づいて被測定物の楕円率及び楕円方位角を算出する。バンドパスフィルタの分光スペクトルを考慮する具体的な一方法は後で述べる。 In one embodiment, step S0 selects a wavelength using a bandpass filter to capture detection signals at multiple wavelengths. In the simulation in step S2, the detection light intensity for each wavelength λi is calculated in consideration of the spectrum of the bandpass filter in step S0, and the ellipticity of the object to be measured and the measured object light intensity are calculated based on the calculated detection light intensity. The ellipse azimuth is calculated. A specific method for considering the spectrum of the bandpass filter will be described later.
他の実施形態は被測定物の旋光性を考慮したものである。この実施形態では、ステップＳ１で求めたポアンカレ球赤道面上の複数の実測点からなる近似直線を求め、その近似直線がポアンカレ球赤道面の円と交わる点とポアンカレ球赤道面の円上の入射直線偏光に対応する点とのなす角に基づいて被測定物の旋光角を求める。 Other embodiments consider the optical rotation of the object to be measured. In this embodiment, an approximate straight line composed of a plurality of measurement points on the Poincare sphere equatorial plane obtained in step S1 is obtained, and the point where the approximate straight line intersects with the circle on the Poincare sphere equatorial plane and the incidence on the circle on the Poincare sphere equatorial plane. The optical rotation angle of the object to be measured is obtained based on the angle formed with the point corresponding to the linearly polarized light.
被測定物の旋光角を求めるこの方法は、一実施形態としては被測定物の位相差と光学主軸の方位を求め、さらに旋光角を求めるように実施することである。 This method of obtaining the optical rotation angle of the object to be measured is, as one embodiment, obtained by obtaining the phase difference of the object to be measured and the orientation of the optical principal axis, and further obtaining the optical rotation angle.
被測定物の旋光角を求めるこの方法は、また、被測定物の位相差と光学主軸の方位を求めることなく、被測定物の旋光角を求める方法としても実施することができる。 This method for obtaining the optical rotation angle of the object to be measured can also be implemented as a method for obtaining the optical rotation angle of the object to be measured without obtaining the phase difference of the object to be measured and the orientation of the optical principal axis.
さらに他の実施形態は被測定物の旋光性を考慮した真の光学主軸方位を求めるものである。この実施形態では、ステップＳ１で求めたポアンカレ球赤道面上の複数の実測点からなる近似直線を求め、ポアンカレ球赤道面の円の中心からその近似直線に下ろした垂線と、ポアンカレ球赤道面の円上で入射直線偏光に対応した点と該円の中心を結ぶ直線とのなす角を求め、その角と旋光角とに基づいて被測定物の真の光学主軸方位を求める。 In yet another embodiment, the true optical principal axis orientation in consideration of the optical rotation of the object to be measured is obtained. In this embodiment, an approximate straight line composed of a plurality of measurement points on the Poincare sphere equatorial plane obtained in step S1 is obtained, and a perpendicular drawn from the center of the circle of the Poincare sphere equatorial plane to the approximate straight line and the Poincare sphere equatorial plane An angle formed by a point corresponding to the incident linearly polarized light on the circle and a straight line connecting the center of the circle is obtained, and the true optical principal axis direction of the object to be measured is obtained based on the angle and the optical rotation angle.
被測定物の真の光学主軸方位を求めるこの方法は、一実施形態としては被測定物の位相差と光学主軸の方位を求め、さらに旋光角とともに真の光学主軸方位を求めるように実施することである。 This method for determining the true optical principal axis orientation of the object to be measured is, as one embodiment, obtained by obtaining the phase difference of the object to be measured and the optical principal axis direction, and further obtaining the true optical principal axis direction together with the optical rotation angle. It is.
被測定物の旋光角と真の光学主軸方位を求めるこの方法は、また、被測定物の位相差と光学主軸の方位を求めることなく、被測定物の旋光角と真の光学主軸方位を求める方法としても実施することができる。 This method of obtaining the optical rotation angle and true optical principal axis orientation of the object to be measured also obtains the optical rotation angle and true optical principal axis orientation of the object to be measured without obtaining the phase difference and optical principal axis orientation of the object to be measured. It can also be implemented as a method.
真の光学主軸方位に対し、被測定物の旋光性を考慮することなく求めた光学主軸方位は、いわば見掛け上の光学主軸方位というべきものである。被測定物が旋光性をもっている場合は、見掛け上の光学主軸方位は旋光角の分だけ真の光学主軸方位から異なったものとなる。一方、被測定物が旋光性をもっていない場合は、見掛け上の光学主軸方位と真の光学主軸方位は一致する。この明細書では真の光学主軸方位については逐一「真の」という形容詞をつけるが、見掛け上の光学主軸方位については逐一「見掛け上」のという形容詞はつけない。 The optical principal axis orientation obtained without considering the optical rotation of the object to be measured with respect to the true optical principal axis orientation is, in other words, an apparent optical principal axis orientation. When the object to be measured has optical rotation, the apparent optical principal axis orientation differs from the true optical principal axis orientation by the angle of optical rotation. On the other hand, when the object to be measured does not have optical rotation, the apparent optical principal axis orientation matches the true optical principal axis orientation. In this specification, the adjective “true” is given for the true optical principal axis direction, but the adjective “apparent” is not given for the apparent optical principal axis direction.
位相差測定装置の好ましい実施形態では、測定部の光学系は、互いに異なる複数の波長λiごとのバンドパスフィルタを備え、光検出器はバンドパスフィルタごとに設けられ、それらのバンドパスフィルタを透過した測定光がそれぞれの光検出器で同時に検出されるように構成されている。 In a preferred embodiment of the phase difference measuring apparatus, the optical system of the measuring unit includes a bandpass filter for each of a plurality of different wavelengths λi, and a photodetector is provided for each bandpass filter, and transmits through these bandpass filters. The measured light is simultaneously detected by the respective photodetectors.
バンドパスフィルタを切り替えて、異なる波長ごとの位相差を測定する場合には装置も大きくなり測定時間も長くなるが、この実施形態のように複数の波長での検出信号を同時に得るようにすれば、測定系の駆動機構は検光子又は偏光子の回転１つのみでよいので検出光強度は短時間で取り込むことができ、演算処理時間を含めても短時間、例えば３秒以内、で被測定物の1点の測定を終えることができる。したがって、この実施形態によれば、例えば高位相差フィルムの加工工程において大量の検査を効率よく行うことができるようになる。 When the phase difference for each different wavelength is measured by switching the bandpass filter, the apparatus becomes larger and the measurement time becomes longer, but if detection signals at a plurality of wavelengths are obtained simultaneously as in this embodiment, Since the measurement system only needs one rotation of the analyzer or polarizer, the detection light intensity can be captured in a short time, and the measurement can be performed in a short time, for example, within 3 seconds, including the processing time. You can finish measuring one point of an object. Therefore, according to this embodiment, for example, a large amount of inspection can be efficiently performed in the processing step of the high retardation film.
しかし、本発明は、偏光子回転法又は検光子回転法を用いポアンカレ球を利用する方法に特徴があるので、光学系としては図９のようにバンドパスフィルタを順次切り替えて複数波長での検出信号を得るものも含む。 However, since the present invention is characterized by a method using a Poincare sphere using a polarizer rotation method or an analyzer rotation method, the optical system can detect a plurality of wavelengths by sequentially switching bandpass filters as shown in FIG. Includes those that obtain signals.
以下に本発明の位相差測定方法と装置を具体的に説明する。 The phase difference measuring method and apparatus of the present invention will be specifically described below.
測定部（１００）の検出法は、回転検光子法によるものと回転偏光子法によるものの２種類がある。 There are two types of detection methods of the measurement unit (100), one based on the rotational analyzer method and the other based on the rotational polarizer method.
回転検光子法をとる測定部（１００）では、図８（Ａ）において光源装置１からの測定光はライトガイド２を経て集光レンズ３で平行光になる。その測定光は固定された偏光子４を通して直線偏光となり、被測定物５に照射され、被測定物５を透過した測定光が検光子６を経て、光検出器８に入射して透過光強度が測定される。光検出器８は複数個設けられ、それぞれの光検出器８は可視域で互いに異なる波長λiの測定光が入射するようにバンドパスフィルタ７を備えている。検光子６はその偏光方位θが０°から３６０°まで１回転するように回転機構を備えている。 In the measurement unit (100) employing the rotation analyzer method, the measurement light from the light source device 1 is converted into parallel light by the condenser lens 3 via the light guide 2 in FIG. The measurement light becomes linearly polarized light through the fixed polarizer 4, is irradiated onto the object to be measured 5, and the measurement light transmitted through the object to be measured 5 is incident on the photodetector 8 through the analyzer 6 and transmitted light intensity. Is measured. A plurality of photodetectors 8 are provided, and each photodetector 8 includes a band-pass filter 7 so that measurement light having different wavelengths λi in the visible region is incident. The analyzer 6 includes a rotation mechanism so that the polarization direction θ rotates once from 0 ° to 360 °.
一方、回転偏光子法では図８（Ｂ）のように偏光子と検光子の役割が入れ替わり、検光子６が固定され、偏光子４はその偏光方位θが０°から３６０°まで１回転するように回転機構を備えているが、得られる検出光強度変化は回転検光子法と同じである。 On the other hand, in the rotating polarizer method, as shown in FIG. 8B, the roles of the polarizer and the analyzer are interchanged, the analyzer 6 is fixed, and the polarizer 4 rotates once from 0 ° to 360 ° in the polarization direction θ. However, the detected light intensity change obtained is the same as that of the rotational analyzer method.
図１に示されるように、演算処理部（１１）は、波長λiごとの検出光強度から回転検光子法の原理に基づいて楕円偏光の楕円率（α／β）i及び楕円方位角Ψiを算出し、さらにそれらの楕円率と楕円方位角に対応した偏光状態をポアンカレ球赤道面に図示したときの点の座標（Ｘi、Ｙi）を求める偏光解析部（１１０）と、被測定物の位相差の波長分散特性を予め保持して、その波長分散特性に基づいて基準波長での位相差Ｒoを各波長での位相差Ｒiに補正する位相差補正部（１１３）と、後述のＯＰＴＩＭＡ法により偏光板に位相差板１枚が貼合された状態での透過光の楕円率と楕円方位角を求める計算手法を用い、その際の計算条件として被測定物に対して基準方向（装置基準方向又は装置基準方向に対して４５°方向）の直線偏光が照射され、さらに被測定物の位相差値を位相差補正部（１１３）により波長λiごとに補正された変数Ｒi、光学主軸方位を変数φ(ただし、φは基準方向からの値)とし、位相差Ｒoを所定の範囲にわたって、所定の刻みで変化させながら波長λiごとの楕円率（α／β）isと楕円方位角Ψisとを求め、さらにそれらの偏光状態のポアンカレ球赤道面の点の座標（Ｘis、Ｙis）を算出する偏光特性算出部（１１１）と、偏光特性算出部（１１１）による計算結果の点の座標（Ｘis、Ｙis）の中から実測で得られた波長λiごとの点の座標（Ｘi、Ｙi）とが最も近くなるときのＲoを求めるマッチング部（１１２）と、を備えている。 As shown in FIG. 1, the arithmetic processing unit (11) calculates the ellipticity (α / β) i and elliptical azimuth angle ψi of elliptically polarized light based on the principle of the rotational analyzer method from the detected light intensity for each wavelength λi. A polarization analyzer (110) for calculating and further calculating the coordinates (Xi, Yi) of the point when the polarization state corresponding to the ellipticity and the elliptical azimuth is illustrated on the Poincare sphere equatorial plane, and the position of the object to be measured A phase difference correction unit (113) that holds the wavelength dispersion characteristic of the phase difference in advance and corrects the phase difference Ro at the reference wavelength to the phase difference Ri at each wavelength based on the wavelength dispersion characteristic, and an OPTIMA method to be described later A calculation method for obtaining the ellipticity and elliptical azimuth angle of transmitted light in a state where one retardation plate is bonded to a polarizing plate, and the calculation condition at that time is the reference direction (device reference direction) with respect to the object to be measured. (Or 45 ° direction relative to the device reference direction) Further, the phase difference value of the object to be measured is defined as a variable Ri corrected for each wavelength λi by the phase difference correction unit (113), the optical principal axis direction is a variable φ (where φ is a value from the reference direction), and the phase difference Ro The ellipticity (α / β) is and the elliptical azimuth angle ψis for each wavelength λi are obtained over a predetermined range while changing in predetermined increments, and the coordinates (Xis) of the Poincare sphere equatorial plane of those polarization states are obtained. , Yis), and the coordinates (Xis, Yis) of points calculated by the polarization characteristics calculation unit (111) for each wavelength λi obtained by measurement from the coordinates (Xis, Yis). And a matching unit (112) for obtaining Ro when Xi, Yi) are closest to each other.
ここで、「所定の範囲」は次のように定める。検査しようとしている被測定物の位相差がどの程度の範囲の値をとるものであるか分かっており、その値を含むような範囲、例えばＲoは１０００ｎｍから３０００ｎｍの範囲という具合に定める。 Here, the “predetermined range” is determined as follows. It is known how much the phase difference of the object to be inspected takes a value, and a range including the value, for example, Ro is set to a range of 1000 nm to 3000 nm.
また、「所定の刻み」とは、測定者が必要とする位相差の分解能の意味であり、例えば５ｎｍの刻みで計算する。 The “predetermined increment” means the resolution of the phase difference required by the measurer, and is calculated in increments of 5 nm, for example.
一実施例の位相差測定装置の動作を、図３を参照して説明する。波長λiの測定光が偏光子を通して直線偏光となって被測定物に照射され、被測定物を透過した光が検光子を経て光検出器に入射して透過光強度が検出される。検光子は０°から３６０°まで回転可能な機構になっており、検光子１回転中の検出光強度変化から楕円偏光状態、すなわち楕円率（α／β）iと基準方向に対する楕円方位角Ψiとを算出する（ステップＳ１）。例えば、図１１のような検出光強度変化が得られたとき、楕円率は（Ｉｍｉｎ／Ｉｍａｘ）1/2、楕円方位角は長軸方向となるので、比較的容易に実測することができる。ここでは検光子回転法を例にして説明しているが、偏光子回転法の場合も同じである。 The operation of the phase difference measuring apparatus according to one embodiment will be described with reference to FIG. The measurement light having the wavelength λi is converted into linearly polarized light through the polarizer and applied to the object to be measured. The light transmitted through the object to be measured is incident on the photodetector through the analyzer, and the transmitted light intensity is detected. The analyzer has a mechanism capable of rotating from 0 ° to 360 °, and the elliptical polarization state, that is, the ellipticity (α / β) i and the elliptical azimuth angle ψi with respect to the reference direction, from the change in detected light intensity during one rotation of the analyzer. Are calculated (step S1). For example, when a change in detected light intensity as shown in FIG. 11 is obtained, the ellipticity is (Imin / Imax) 1/2 and the elliptical azimuth is in the major axis direction, so that it can be measured relatively easily. Here, the analyzer rotation method is described as an example, but the same applies to the polarizer rotation method.
一方、計算によって被測定物に直線偏光が入射したときの、透過光の偏光状態（楕円率と楕円方位角）を求める（ステップＳ２）。例えば、王子計測機器製のシミュレーションソフトＬＣＤ−ＯＰＴＩＭＡは任意の偏光が位相差板に入射したときの透過光の偏光状態を計算でき、位相差板の位相差及び遅相軸方位を任意に設定できる。本発明はＬＣＤ−ＯＰＴＩＭＡで用いている計算方法を用いる。その計算方法をＯＰＴＩＭＡ法と呼ぶ。 On the other hand, the polarization state (ellipticity and elliptical azimuth angle) of transmitted light when linearly polarized light enters the object to be measured is calculated (step S2). For example, the simulation software LCD-OPTIMA manufactured by Oji Scientific Instruments can calculate the polarization state of transmitted light when any polarized light enters the phase difference plate, and can arbitrarily set the phase difference and slow axis direction of the phase difference plate. . The present invention uses the calculation method used in LCD-OPTIMA. This calculation method is called the OPTIMA method.
ＯＰＴＩＭＡ法を説明する前に、偏光状態を表現する方法の一つであるポアンカレ球について説明する。ポアンカレ球は地球儀のような球体上に配置した点の位置によって偏光状態を表すが、基本的な特徴は次のようになる。（１）赤道上はすべて楕円率０の直線偏光を表し、北極と南極は楕円率１の円偏光、その他の点はすべて楕円偏光を表す。（２）経度が同じ点はすべて方位の同じ偏光を表し、基準となる位置から読み取った経度の半分の角度だけ偏光方位が変わる。（３）北半球と南半球では回転方向が逆の楕円偏光を表す。 Before explaining the OPTIMA method, the Poincare sphere, which is one of the methods for expressing the polarization state, will be explained. The Poincare sphere expresses the polarization state by the position of a point placed on a sphere like a globe. The basic features are as follows. (1) All on the equator represent linearly polarized light with an ellipticity of 0, the north and south poles represent circularly polarized light with an ellipticity of 1, and all other points represent elliptically polarized light. (2) All points with the same longitude represent polarized light having the same azimuth, and the polarization azimuth changes by an angle that is half the longitude read from the reference position. (3) The northern hemisphere and the southern hemisphere represent elliptically polarized light having opposite rotation directions.
位相差板を偏光変換素子と考えると、その変換の様子はポアンカレ球を用いて表すことができる。図５は、図６のように位相差板に直線偏光が入射したときのポアンカレ球上での点の移動を説明した図である。位相差板の位相差をＲ、入射直線偏光の透過軸を基準にした位相差板の遅相軸方位をφとして、ポアンカレ球上では入射直線偏光を表す点をＰとし、まず点Ｐから経度２φの方向に球の中心を通る回転軸を描く。次に点Ｐを通り回転軸と直角に交わる直線を含みかつ赤道面に垂直な面を考え、これを回転断面と呼ぶことにする。この回転断面によって定まる球上の円弧に沿ってＲと波長λによって決まる回転角δだけ点Ｐを移動した点Ｍが位相差板によって変換された偏光状態になる。 When the retardation plate is considered as a polarization conversion element, the state of the conversion can be expressed using a Poincare sphere. FIG. 5 is a diagram for explaining the movement of a point on the Poincare sphere when linearly polarized light is incident on the phase difference plate as shown in FIG. The phase difference of the retardation plate is R, the slow axis direction of the retardation plate relative to the transmission axis of the incident linearly polarized light is φ, and the point representing the incident linearly polarized light on the Poincare sphere is P. Draw a rotation axis passing through the center of the sphere in the direction of 2φ. Next, a plane including a straight line passing through the point P and perpendicular to the rotation axis and perpendicular to the equator plane is considered, and this is referred to as a rotation section. A point M obtained by moving the point P by a rotation angle δ determined by R and the wavelength λ along an arc on a sphere determined by the rotation cross section becomes a polarization state converted by the phase difference plate.
点Ｍを赤道面へ投影した点をＭ’とし、点Ｐから見た点Ｍ’の経度を２Ψとしたとき、点Ｍの楕円方位は点Ｐの直線偏光の透過軸に対してΨだけ方位が異なる。また、点Ｍの楕円率は∠ＭＯＭ’を２χとしたとき、ｔａｎχとなる。 When the point M projected onto the equator plane is M ′ and the longitude of the point M ′ viewed from the point P is 2Ψ, the elliptical direction of the point M is the direction of Ψ relative to the transmission axis of the linearly polarized light at the point P. Is different. The ellipticity of the point M is tan χ when ∠MOM ′ is 2χ.
ＯＰＴＩＭＡ法は、上記のようにポアンカレ球上で移動する点を幾何学的に処理することにより、直線偏光が任意の位相差板に入射したときの透過光の楕円偏光状態を求めるものである。 The OPTIMA method obtains the elliptical polarization state of transmitted light when linearly polarized light is incident on an arbitrary phase difference plate by geometrically processing the points moving on the Poincare sphere as described above.
計算の中で、被測定物の基準波長での位相差Ｒoは所定の範囲を所定の刻みで変化させるが、位相差は波長依存性をもっている。そこで、演算処理部（１１）は位相差補正部（１１３）を備えている。位相差補正部（１１３）は、被測定物の位相差の波長分散特性を予め保持しており、偏光特性算出部（１１１）で使用する変数Ｒiをその波長分散特性に基づいて各波長の位相差に補正する。 In the calculation, the phase difference Ro at the reference wavelength of the object to be measured is changed in a predetermined range in a predetermined unit, but the phase difference has wavelength dependency. Therefore, the arithmetic processing unit (11) includes a phase difference correction unit (113). The phase difference correction unit (113) holds the wavelength dispersion characteristic of the phase difference of the object to be measured in advance, and the variable Ri used in the polarization characteristic calculation unit (111) is set based on the wavelength dispersion characteristic. Correct for phase difference.
位相差補正部（１１３）は波長λiごとの位相差を次のように求める。まず、被測定物の位相差の波長分散特性を（４）式で表し、予め式中の係数Ａ、Ｂ、Ｃを登録しておく。計算の中では基準波長λoにおける位相差を変数Ｒoとして変化させ、波長λiでの位相差Ｒiを（５）式によって算出する。そして、ＯＰＴＩＭＡ法の計算により波長ごとの楕円率（α／β）isと楕円方位角Ψisを計算により求める（図３のステップＳ２）。
The phase difference correction unit (113) obtains the phase difference for each wavelength λi as follows. First, the wavelength dispersion characteristic of the phase difference of the object to be measured is expressed by the equation (4), and the coefficients A, B, and C in the equation are registered in advance. In the calculation, the phase difference at the reference wavelength λo is changed as a variable Ro, and the phase difference Ri at the wavelength λi is calculated by equation (5). Then, the ellipticity (α / β) is and the elliptical azimuth angle ψis for each wavelength are obtained by calculation by the OPTIMA method (step S2 in FIG. 3).
好ましい実施形態での特徴は２つあり、１つは偏光特性算出部（１１１）での計算において波長λiは測定波長に対応した複数の波長であるが、装置に使用されるバンドパスフィルタは理想的な単一波長ではなく分光スペクトルの分布を持つフィルタである。その特性は中心波長と半値幅で示され、例えば半値幅は１０ｎｍ前後のものを使用する場合が多い。 In the preferred embodiment, there are two features. One is a wavelength characteristic in the calculation by the polarization characteristic calculation unit (111). The wavelength λi is a plurality of wavelengths corresponding to the measurement wavelength, but the bandpass filter used in the apparatus is ideal. It is a filter having a spectral spectrum distribution instead of a typical single wavelength. The characteristic is indicated by the center wavelength and the half-value width. For example, a half-value width of around 10 nm is often used.
このときλiは図１２（Ａ）のように中心波長に相当し、分光スペクトルで光が透過する範囲の各波長をλijとすると、図１２（Ｂ）のようにλijに対応した被測定物の位相差Ｒjすべてが測定に関わり、回転検光子法で観測される検出光強度は透過する光λijすべてを合算したものになる。それは、中心波長を単一波長として観測したものとは異なる。
例えば、位相差Ｒoが２８００ｎｍのＰＥＴフィルムを仮定し、入射直線偏光方位に対してその遅相軸が４０°になるように置いたときの透過光の偏光状態をＯＰＴＩＭＡ法を用いて計算し、測定光が単一波長のとき及びバンドパスフィルタの半値幅が１０ｎｍのとき、それぞれの計算結果をポアンカレ球赤道面に表示すると、図１３のようになり両者の点の位置がずれる。
At this time, λi corresponds to the center wavelength as shown in FIG. 12A. If each wavelength in the spectral transmission range of light is λij, the object to be measured corresponding to λij as shown in FIG. All the phase differences Rj are involved in the measurement, and the detected light intensity observed by the rotating analyzer method is the sum of all the transmitted light λij. It is different from that observed with the central wavelength as a single wavelength.
For example, assuming a PET film having a phase difference Ro of 2800 nm and calculating the polarization state of transmitted light using the OPTIMA method when the slow axis is 40 ° with respect to the incident linear polarization direction, When the measurement light has a single wavelength and the half-width of the band-pass filter is 10 nm, the respective calculation results are displayed on the Poincare sphere equatorial plane as shown in FIG.
ただし、被測定物の位相差が１０００ｎｍ以下の場合は、中心波長の単一波長で計算した結果と観測される結果は殆ど一致しズレは無視できる。バンドパスフィルタの半値幅の大小で観測される偏光状態が変わるのは、被測定物の位相差が１０００ｎｍを超える高位相差の場合で、このことは実際に半値幅の異なるバンドパスフィルタを用いて実測した結果でも確認できた。 However, when the phase difference of the object to be measured is 1000 nm or less, the result calculated with the single wavelength of the central wavelength and the observed result are almost the same, and the deviation can be ignored. The polarization state observed depending on the half-width of the band-pass filter changes when the phase difference of the object to be measured is a high phase difference exceeding 1000 nm. This is actually achieved by using band-pass filters with different half-widths. It was also confirmed by actual measurement results.
好ましい実施形態では、バンドパスフィルタの分光スペクトルを次式で近似し、ＯＰＴＩＭＡ法の計算の際に分光スペクトルの波長分の透過光強度を集計して１つの楕円率と楕円方位角を算出する（図３のステップＳ２）。
ここで、λiは中心波長、Δλは半値幅である。
In a preferred embodiment, the spectral spectrum of the bandpass filter is approximated by the following equation, and the transmitted light intensity corresponding to the wavelength of the spectral spectrum is totaled when calculating the OPTIMA method to calculate one ellipticity and elliptic azimuth angle ( Step S2 in FIG.
Here, λi is the center wavelength, and Δλ is the half width.
バンドパスフィルタの分光スペクトルを考慮した実施形態の位相差測定装置では、偏光特性算出部（１１１）は、シミュレーションでは測定部の光学系のバンドパスフィルタの分光スペクトルを考慮して波長λiごとの検出光強度を算出し、その算出された検出光強度に基づいて被測定物の楕円率（α／β）is及び楕円方位角Ψisを算出するように構成されている。 In the phase difference measuring apparatus of the embodiment that takes into account the spectral spectrum of the bandpass filter, the polarization characteristic calculation unit (111) detects each wavelength λi in consideration of the spectral spectrum of the bandpass filter of the optical system of the measuring unit in the simulation. The light intensity is calculated, and the ellipticity (α / β) is and the elliptic azimuth angle Ψis of the object to be measured are calculated based on the calculated detected light intensity.
好ましい実施形態のもう１つの特徴は、偏光特性算出部（１１１）での計算において旋光性を考慮することである。旋光とは入射直線偏光がその物質を透過したときに偏光方位が回転する現象であり、糖などの溶液や水晶などの結晶で起こる。 Another feature of the preferred embodiment is that optical rotation is taken into account in the calculation by the polarization characteristic calculator (111). Optical rotation is a phenomenon in which the polarization orientation rotates when incident linearly polarized light passes through the substance, and occurs in solutions such as sugar and crystals such as quartz.
図１４は、位相差が３７７０ｎｍのＰＥＴフィルム及び位相差が４７９０ｎｍのＰＣフィルムを、図６におけるφを４５°にして、回転検光子法によって４５０ｎｍ〜７５０ｎｍ範囲の６つの異なる波長で透過光の偏光状態を測定し、その結果をポアンカレ球赤道面に表示したものである。点ＰＯＬは入射直線偏光に対応する点を表し、本来、旋光性をもたないフィルム１枚に直線偏光が入射した場合はＰＣフィルムの測定結果のように、点ＰＯＬと円の中心を結ぶ線（縦軸）上に各波長の点が並ぶ。しかし、旋光性をもつフィルムの場合は、図１４のＰＥＴフィルムの測定結果のように、点ＰＯＬを通らない、即ち前述のポアンカレ球の特徴説明の回転断面が点ＰＯＬを通らないことになる。 FIG. 14 shows the polarization of transmitted light at six different wavelengths ranging from 450 nm to 750 nm by a rotating analyzer method using a PET film having a phase difference of 3770 nm and a PC film having a phase difference of 4790 nm with φ of 45 ° in FIG. The state is measured and the result is displayed on the Poincare sphere equatorial plane. The point POL represents a point corresponding to the incident linearly polarized light. When the linearly polarized light is incident on one film that does not have optical rotation, a line connecting the point POL and the center of the circle as in the measurement result of the PC film. The points of each wavelength are arranged on the (vertical axis). However, in the case of a film having optical rotation, as shown in the measurement result of the PET film in FIG. 14, the point POL does not pass, that is, the rotation cross section of the characteristic explanation of the Poincare sphere does not pass the point POL.
同じく位相差３７７０ｎｍのＰＥＴフィルムを、図６におけるφを２０°、３０°及び４５°にした状態の透過光の偏光状態をポアンカレ球赤道面に表示すると、図１５のようになり、すべての回転断面は点Ｐ'を通ることが分かる。そこで、ＰＥＴフィルムは旋光性と複屈折性を併せ持つと解釈し、図１５のような図から被測定物の旋光角と真の光学主軸方位を求める。 Similarly, when a PET film with a phase difference of 3770 nm is displayed on the Poincare sphere equatorial plane with the polarization state of transmitted light in the state where φ is 20 °, 30 ° and 45 ° in FIG. 6, it becomes as shown in FIG. It can be seen that the cross section passes through the point P ′. Therefore, the PET film is interpreted as having both optical rotation and birefringence, and the optical rotation angle and the true optical principal axis direction of the object to be measured are obtained from a diagram as shown in FIG.
旋光性を考慮したこの実施形態を図２と図４を参照して説明する。図１、図３と同じ部分には同じ符号を付し、説明を省略する。図１６のように６つの測定点の座標（Ｘi，Ｙi）を、楕円率（α／β）iと楕円方位角Ψiから次式によって求める。
This embodiment considering optical rotation will be described with reference to FIGS. The same parts as those in FIGS. 1 and 3 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 16, the coordinates (Xi, Yi) of the six measurement points are obtained from the ellipticity (α / β) i and the elliptical azimuth angle ψi by the following equation.
６つの測定点を直線近似して、図１６における点ＰＯＬと線分ＯＰ'のなす角２ε及び回転軸の方位２γを求める（図４のステップＳ５）。ポアンカレ球では角度はすべて２倍で表されるので、旋光角はε、また被測定物の真の光学主軸方位は（γ−ε）となる。実際に、図１５のφ＝２０°、３０°及び４５°の条件で実測した数値を上記の方法で解析すると、ε＝２．２°となり、かつφ（＝γ−ε）は十分な精度で元の値と一致した。ＰＥＴフィルムであれば旋光角が一定値になるというものではなく、被測定物ごとに異なるのでステップＳ５の処理は常に行う。 Six measurement points are linearly approximated to obtain an angle 2ε and a rotation axis azimuth 2γ formed by the point POL and the line segment OP ′ in FIG. 16 (step S5 in FIG. 4). In the Poincare sphere, the angles are all expressed by a factor of 2, so the optical rotation angle is ε, and the true optical principal axis orientation of the object to be measured is (γ−ε). Actually, when the numerical values actually measured under the conditions of φ = 20 °, 30 ° and 45 ° in FIG. 15 are analyzed by the above method, ε = 2.2 ° and φ (= γ−ε) has sufficient accuracy. Matched the original value. In the case of a PET film, the optical rotation angle does not become a constant value, and varies depending on the object to be measured, so the process of step S5 is always performed.
ステップＳ５の処理を行うために、この実施形態の位相差測定装置は、図２に示されるように旋光角（ε）算出部（１１５）と真の光学主軸方位（γ−ε）算出部（１１６）をさらに備えている。 In order to perform the processing of step S5, the phase difference measurement apparatus of this embodiment includes an optical rotation angle (ε) calculation unit (115) and a true optical principal axis orientation (γ-ε) calculation unit (as shown in FIG. 116).
旋光角算出部（１１５）は、偏光解析部（１１０）で求められたポアンカレ球赤道面上の複数の実測点（Ｘi、Ｙi）からなる近似直線を求め、その近似直線がポアンカレ球赤道面の円と交わる点とポアンカレ球赤道面の円上で入射直線偏光に対応する点とのなす角に基づいて被測定物の旋光角εを求めるものである。 The optical rotation angle calculation unit (115) obtains an approximate line composed of a plurality of actually measured points (Xi, Yi) on the Poincare sphere equatorial plane obtained by the polarization analysis unit (110), and the approximate line is the Poincare sphere equatorial plane. The optical rotation angle ε of the object to be measured is obtained based on the angle formed between the point intersecting the circle and the point corresponding to the incident linearly polarized light on the Poincare sphere equatorial plane.
光学主軸方位算出部（１１６）は、偏光解析部（１１０）で求められたポアンカレ球赤道面上の複数の実測点（Ｘi、Ｙi）からなる近似直線を求め、ポアンカレ球赤道面の円の中心からその近似直線に下ろした垂線と、ポアンカレ球赤道面の円上で入射直線偏光に対応する点とポアンカレ球赤道面の円の中心を結ぶ直線とのなす角を求め、その角と旋光角εとに基づいて被測定物の真の光学主軸方位（γ−ε）を求めるものである。 The optical principal axis azimuth calculating unit (116) obtains an approximate straight line composed of a plurality of measured points (Xi, Yi) on the Poincare sphere equator obtained by the ellipsometer (110), and the center of the circle of the Poincare sphere equatorial plane is obtained. To the approximate straight line, and the angle between the point corresponding to the incident linearly polarized light on the Poincare sphere's equatorial plane and the straight line connecting the center of the Poincare sphere's equatorial plane, and the angle of rotation ε Based on the above, the true optical principal axis orientation (γ−ε) of the object to be measured is obtained.
実測値から得られたεおよび（γ−ε）の値はＯＰＴＩＭＡ法の計算時に条件として持ち込まれ、Ｒoのみを変数として変化させながら計算を行う（図４のステップＳ２）。 The values of ε and (γ−ε) obtained from the actually measured values are brought in as conditions during the calculation of the OPTIMA method, and calculation is performed while changing only Ro as a variable (step S2 in FIG. 4).
図１５のようなポアンカレ球赤道面の図において、実測値の点が点ＰＯＬの周辺に集まる場合は、計算結果とのマッチング処理で誤差が出やすくなる。そこで、検光子回転法の場合は、偏光子として透過軸が装置基準軸（検光子透過軸方位）に対して例えば０°のものと４５°のものを用意しておく。一方の偏光子を使用して測定をしてポアンカレ球赤道面の図において実測値の点を求めた場合、それらの点が点ＰＯＬの周辺に集まったときは、もう１つの偏光子に入れ替えて測定し直すことにより、測定精度がよくなる。偏光子方位の０°と４５°のいずれを採用するかは、測定結果の被測定物の真の光学主軸方位（γ−ε）の算出時に設定することができる。偏光子回転法の場合は、同様にして検光子の透過軸を設定することができる。 In the Poincare sphere equatorial plane as shown in FIG. 15, when measured points gather around the point POL, an error is likely to occur in the matching process with the calculation result. Therefore, in the case of the analyzer rotation method, a polarizer having a transmission axis of, for example, 0 ° and 45 ° with respect to the apparatus reference axis (analyzer transmission axis orientation) is prepared. When measurement is performed using one polarizer and the points of the measured values are obtained in the Poincare sphere equatorial plane, when these points gather around the point POL, they are replaced with another polarizer. By re-measuring, the measurement accuracy is improved. Which of 0 ° and 45 ° of the polarizer orientation can be used can be set when calculating the true optical principal axis orientation (γ−ε) of the measured object. In the case of the polarizer rotation method, the transmission axis of the analyzer can be set similarly.
図８（Ａ）は、一実施例の概略構成図であり、回転検光子法を採用したものである。６つの異なる波長に対する透過光強度を検出する部分と、実測の波長ごとに被測定物に直線偏光が入射したときの透過光の楕円率と楕円方位角とを算出する演算処理部１１を備えている。 FIG. 8A is a schematic configuration diagram of one embodiment, which employs a rotating analyzer method. A portion for detecting transmitted light intensity for six different wavelengths, and an arithmetic processing unit 11 for calculating the ellipticity and the elliptical azimuth of the transmitted light when linearly polarized light is incident on the object to be measured for each actually measured wavelength are provided. Yes.
透過光強度検出部において、光源装置１は例えばハロゲンランプを発光源とした可視域の多波長成分を含む測定光を供給するもので、測定光はライトガイド２と集光レンズ３を通って被測定物へ照射される。 In the transmitted light intensity detection unit, the light source device 1 supplies measurement light containing a multi-wavelength component in the visible range using, for example, a halogen lamp as a light source, and the measurement light passes through the light guide 2 and the condensing lens 3. Irradiates the measurement object.
被測定物５を透過した光は回転可能な検光子６を透過して、バンドパスフィルタ７を通り光検出器８に入る。光検出器８は６個配置され、バンドパスフィルタ７は各光検出器８に入射する測定光の光路上にそれぞれ異なる波長を選択するように配置されている。 The light that has passed through the DUT 5 passes through the rotatable analyzer 6, passes through the bandpass filter 7, and enters the photodetector 8. Six photodetectors 8 are arranged, and the band-pass filter 7 is arranged so as to select different wavelengths on the optical path of the measurement light incident on each photodetector 8.
図８（Ｂ）のように、被測定物と検光子の順序が逆になった測定系でも光学的には同じであるので、図８（Ａ）の測定系を用いた場合と同様の結果が得られる。このとき、検光子６に替わる偏光素子４は被測定物に対して入射側に位置するために偏光子と呼ばれ、測定法は回転偏光子法となる。 As shown in FIG. 8B, the measurement system in which the order of the object to be measured and the analyzer is reversed is optically the same, and therefore the same result as in the case of using the measurement system of FIG. Is obtained. At this time, the polarizing element 4 instead of the analyzer 6 is called a polarizer because it is positioned on the incident side with respect to the object to be measured, and the measuring method is a rotating polarizer method.
検光子６又は偏光子４の１回転中に光検出器８で検出された透過光強度の変化は、増幅器とＡ／Ｄ変換器を含む電気回路１０で増幅とＡ／Ｄ変換されて演算処理部１１に取り込まれる。演算処理部１１は、上述のように波長λiごとの透過光の楕円率（α／β）iと楕円方位角Ψiを算出するとともに、それらの楕円率と楕円方位角に対応した偏光状態をポアンカレ球赤道面に図示したときの点の座標（Ｘi、Ｙi）を求め、別途演算処理法によって被測定物の位相差Ｒoを変化させながら求めた楕円率と楕円方位角からポアンカレ球赤道面での点の座標（Ｘis、Ｙis）を計算し、それら計算結果の中から実測で得られた波長λiごとの点の座標（Ｘi、Ｙi）に最も近くなるときのＲoを求める。演算処理部１１は専用のコンピュータ又は汎用のパーソナルコンピュータにより実現される。 A change in transmitted light intensity detected by the photodetector 8 during one rotation of the analyzer 6 or the polarizer 4 is amplified and A / D converted by an electric circuit 10 including an amplifier and an A / D converter, and is processed. Part 11 is taken in. The arithmetic processing unit 11 calculates the ellipticity (α / β) i and elliptical azimuth angle ψi of the transmitted light for each wavelength λi as described above, and the polarization state corresponding to the ellipticity and elliptical azimuth angle is Poincare. The coordinates (Xi, Yi) of the point when shown on the spherical equator plane are obtained, and the Poincare sphere equatorial plane is calculated from the ellipticity and the elliptical azimuth obtained while changing the phase difference Ro of the object to be measured by a separate arithmetic processing method. The point coordinates (Xis, Yis) are calculated, and Ro is calculated from the calculated results when the point is closest to the point coordinates (Xi, Yi) for each wavelength λi obtained by actual measurement. The arithmetic processing unit 11 is realized by a dedicated computer or a general-purpose personal computer.
図１７は図８（Ａ）と同じ位相差測定装置を表わしたものである。偏光子４はその透過軸の方向を０°又は４５°に設定できるように選択可能になっている。偏光子４の透過軸の方向は一方の偏光子を使用してポアンカレ球赤道面の実測点を求めた結果に基づいて選択することができる。光検出器８の検出信号を取り込んで増幅とＡ／Ｄ変換を行う増幅及びＡ／Ｄ変換回路１０ａは電気回路１０に相当するものであり、測定用ＣＰＵ１１ａは専用のコンピュータ又は汎用のパーソナルコンピュータにより実現されるものであり、演算処理部１１を含む。回転検光子法による検光子６を回転させるために、検光子を回転させるモータを駆動するモータドライバ１２と、モータドライバ１２を制御するモータ制御回路１３が設けられ、モータ制御回路１３は測定用ＣＰＵ１１ａに接続されている。測定用ＣＰＵ１１ａからの指示によりモータ制御回路１３からモータドライバ１２を介して検光子６が回転させられる。 FIG. 17 shows the same phase difference measuring apparatus as FIG. The polarizer 4 is selectable so that the direction of its transmission axis can be set to 0 ° or 45 °. The direction of the transmission axis of the polarizer 4 can be selected based on the result of obtaining the measured point of the Poincare sphere equatorial plane using one polarizer. The amplification and A / D conversion circuit 10a that takes in the detection signal of the photodetector 8 and performs amplification and A / D conversion corresponds to the electric circuit 10, and the measurement CPU 11a is a dedicated computer or a general-purpose personal computer. This is realized and includes the arithmetic processing unit 11. In order to rotate the analyzer 6 by the rotation analyzer method, a motor driver 12 that drives a motor that rotates the analyzer and a motor control circuit 13 that controls the motor driver 12 are provided. The motor control circuit 13 is a measurement CPU 11a. It is connected to the. The analyzer 6 is rotated from the motor control circuit 13 via the motor driver 12 according to an instruction from the measurement CPU 11a.
この実施例において、位相差を求める過程を図１８から図２１に改めて示す。 In this embodiment, the process of obtaining the phase difference is shown again in FIGS.
基準波長λoに対する位相差の分散比率Ｒ（λ）／Ｒ（λo）を表わす分散曲線を選択する。分散曲線は材質ごとに決まっているので、予め測定用ＣＰＵ１１ａに保持しておくことにより、被測定物の材質が決まればそれに対応したものを選択することができる。 A dispersion curve representing the dispersion ratio R (λ) / R (λo) of the phase difference with respect to the reference wavelength λo is selected. Since the dispersion curve is determined for each material, if the material of the object to be measured is determined, it can be selected by holding it in advance in the measurement CPU 11a.
偏光子はその透過軸の方向が装置の基準方向に対して０°のものと４５°のものを用意しておき、その何れかで測定を行う。測定用ＣＰＵ１１ａはモータ制御回路１３からモータドライバ１２を介して検光子を１回転させ、その間に得られた６波長での検出信号をそれぞれの光検出器８から増幅及びＡ／Ｄ変換回路１０ａを介して取り込む。それらの波長ごとの検出光強度に基づき、基準方向に対する被測定物の透過光の楕円率（α／β）isと楕円方位角Ψisを算出し、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の点の座標を求める。それらの座標をポアンカレ球赤道面上に表示すると図１９のようになる。 Polarizers having a transmission axis direction of 0 ° and 45 ° with respect to the reference direction of the apparatus are prepared, and measurement is performed with either of them. The measurement CPU 11a makes one rotation of the analyzer from the motor control circuit 13 via the motor driver 12, and the detection signal at 6 wavelengths obtained during that time is sent from each photodetector 8 to the amplification and A / D conversion circuit 10a. Through. Based on the detected light intensity for each wavelength, the ellipticity (α / β) is and elliptical azimuth angle Ψis of the transmitted light of the measured object with respect to the reference direction are calculated, and the polarization at each wavelength based on those values Find the coordinates of a point on the Poincare sphere equatorial plane that corresponds to the state. When these coordinates are displayed on the Poincare sphere equatorial plane, it is as shown in FIG.
このとき、ポアンカレ球赤道面上の各点による近似直線が破線で示されるようにポアンカレ球赤道面の円の直径から離れてその各点が狭い範囲に集まった場合は、後の計算値との比較の精度が悪くなるので、他方の偏光子に交換をして測定をしなおす。 At this time, if each point gathers in a narrow range away from the diameter of the circle on the Poincare sphere equatorial plane as shown by the broken line, the approximate straight line by each point on the Poincare sphere equatorial plane is Since the accuracy of the comparison is deteriorated, the measurement is performed again by exchanging the other polarizer.
選択した分散曲線分散比率Ｒ（λ）／Ｒ（λo）から測定波長λiごとの分散比率Ｒ（λ）／Ｒ（λo）を求める（図２０）。測定波長λiごとの分散比率Ｒ（λ）／Ｒ（λo）をＲ／Ｒ（λｉ）と表示する。 From the selected dispersion curve dispersion ratio R (λ) / R (λo), the dispersion ratio R (λ) / R (λo) for each measurement wavelength λi is obtained (FIG. 20). The dispersion ratio R (λ) / R (λo) for each measurement wavelength λi is expressed as R / R (λi).
次に、基準波長λoでの位相差Ｒ（λo）を変化させながら複数の測定波長λiごとの透過光の楕円率（α／β）isと楕円方位角Ψisを求める。この操作は具体的には例えば次のように行う。基準波長λoでの位相差Ｒoを変化させる範囲をＲｘ（最小値）〜Ｒｙ（最大値）とし、位相差Ｒoを変化させる幅を計算ステップΔＲとする。まず、位相差Ｒoの最小値Ｒｘに各波長λiで分散比率Ｒ／Ｒ（λｉ）を乗算して
Ｒ'（λi）＝Ｒｘ×Ｒ／Ｒ（λi）
を求める。それらのＲ'（λi）を基にした各波長での透過光の楕円率（α／β）isと楕円方位角Ψisを求める。このとき、波長λiとしてはバンドパスフィルタの分光スペクトルを考慮して、具体的には（６）、（７）式に基づいて楕円率（α／β）isと楕円方位角Ψisを求める。それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上での点の座標を求め、波長ごとに実測点の座標との距離を求める。位相差Ｒoを計算ステップΔＲずつ増加させながら、同じ操作を位相差Ｒoの最大値Ｒｙまで繰り返す。
Next, the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light for each of the plurality of measurement wavelengths λi are obtained while changing the phase difference R (λo) at the reference wavelength λo. Specifically, this operation is performed as follows, for example. A range in which the phase difference Ro at the reference wavelength λo is changed is Rx (minimum value) to Ry (maximum value), and a width for changing the phase difference Ro is a calculation step ΔR. First, the minimum value Rx of the phase difference Ro is multiplied by the dispersion ratio R / R (λi) at each wavelength λi to obtain R ′ (λi) = Rx × R / R (λi)
Ask for. The ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light at each wavelength based on those R ′ (λi) are obtained. At this time, considering the spectral spectrum of the bandpass filter as the wavelength λi, specifically, the ellipticity (α / β) is and the elliptical azimuth angle ψis are obtained based on the equations (6) and (7). The coordinates of the point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength based on these values are obtained, and the distance from the coordinates of the actual measurement point is obtained for each wavelength. The same operation is repeated up to the maximum value Ry of the phase difference Ro while increasing the phase difference Ro by each calculation step ΔR.
その後、計算上の点の座標と実測点との距離が最も小さかった位相差Ｒ（λo）をその被測定物の位相差とする。計算上の点の座標と実測点との距離は、例えば波長ごとに求めた計算上の点の座標と実測点との距離の総和として求めることができる。 Thereafter, the phase difference R (λo) in which the distance between the calculated point coordinates and the actual measurement point is the smallest is taken as the phase difference of the object to be measured. The distance between the coordinates of the calculated point and the actual measurement point can be obtained, for example, as the sum of the distances between the coordinates of the calculated point and the actual measurement point obtained for each wavelength.
１ 光源装置
２ ライトガイド
３ 集光レンズ
４ 偏光子
５ 被測定物
６ 検光子
７ バンドパスフィルタ
８ 光検出器
１０ 電気回路
１１ 演算処理部
１００ 測定部
１１０ 偏光解析部
１１１ 偏光特性算出部
１１２ マッチング部
１１３ 位相差補正部
１１５ 旋光角算出部
１１６ 真の光学主軸方位算出部
DESCRIPTION OF SYMBOLS 1 Light source device 2 Light guide 3 Condensing lens 4 Polarizer 5 Measured object 6 Analyzer 7 Band pass filter 8 Photo detector 10 Electric circuit 11 Arithmetic processing part 100 Measurement part 110 Polarization analysis part 111 Polarization characteristic calculation part 112 Matching part 113 phase difference correction unit 115 optical rotation angle calculation unit 116 true optical principal axis direction calculation unit
Claims (11)
（Ｓ０）前記測定装置から互いに異なる複数の波長での検出信号を取り込む。
（Ｓ１）取り込んだ複数の波長λiごとの検出光強度に基づき、基準方向に対する被測定物の透過光の楕円率（α／β）isと楕円方位角Ψisを算出し、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘi、Ｙi）を求める。
（Ｓ２）シミュレーションにより、基準波長λoでの位相差Ｒoを変化させながら複数の測定波長λiごとの透過光の楕円率（α／β）isと楕円方位角Ψisを求め、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘis、Ｙis）を求める。
（Ｓ３）ポアンカレ球赤道面の計算で求めた複数の点の座標（Ｘiｓ、Ｙiｓ）について、ポアンカレ球赤道面上において同じ波長の実測点の座標（Ｘi、Ｙi）との距離を求め、その距離が最も小さくなるときの基準波長λoでの位相差Ｒoを求めてそれを被測定物の位相差とする。 Place the polarizer and analyzer across the object to be measured, fix one of the transmission axis of the polarizer and the transmission axis of the analyzer, rotate the other, and irradiate the object to be measured through the polarizer, A phase difference measurement method for obtaining a phase difference of an object to be measured by the following steps (S0) to (S3) using a measuring device that detects the measurement light transmitted through the object to be measured by a photodetector through an analyzer.
(S0) Capture detection signals at a plurality of different wavelengths from the measuring device.
(S1) Calculate the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light of the object to be measured with respect to the reference direction based on the detected light intensity for each of the plurality of wavelengths λi, and based on these values The coordinates (Xi, Yi) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength are obtained.
(S2) By simulation, the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light for each of the plurality of measurement wavelengths λi are obtained while changing the phase difference Ro at the reference wavelength λo, and based on these values The coordinates (Xis, Yis) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at each wavelength are obtained.
(S3) With respect to the coordinates (Xis, Yis) of a plurality of points obtained by the calculation of the Poincare sphere equatorial plane , the distances from the coordinates (Xi, Yi) of the measured points of the same wavelength on the Poincare sphere equatorial plane are obtained. The phase difference Ro at the reference wavelength λo when is the smallest is obtained and used as the phase difference of the object to be measured.
前記ステップＳ２でのシミュレーションでは前記ステップＳ０でのバンドパスフィルタの分光スペクトルを考慮してその中心波長λiごとの検出光強度を算出し、その算出された検出光強度に基づいて被測定物の楕円率及び楕円方位角を算出する請求項１又は２に記載の位相差測定方法。 The step S0 is to select a wavelength using a bandpass filter in order to capture detection signals at a plurality of wavelengths,
In the simulation in step S2, the detection light intensity for each central wavelength λ i is calculated in consideration of the spectrum of the bandpass filter in step S0, and the ellipse of the object to be measured is calculated based on the calculated detection light intensity. The phase difference measuring method according to claim 1, wherein the rate and the elliptical azimuth are calculated.
前記近似直線がポアンカレ球赤道面の円と交わる点とポアンカレ球赤道面の円上で入射直線偏光に対応する点とのなす角に基づいて被測定物の旋光角を求める請求項１から３のいずれか一項に記載の位相差測定方法。 Obtain an approximate straight line consisting of a plurality of actually measured points on the Poincare sphere equatorial plane obtained in step S1,
4. The optical rotation angle of the object to be measured is obtained based on an angle formed between a point where the approximate line intersects with the circle of the Poincare sphere equatorial plane and a point corresponding to incident linearly polarized light on the circle of the Poincare sphere equatorial plane. The phase difference measuring method according to any one of the above.
ポアンカレ球赤道面の円の中心から前記近似直線に下ろした垂線と、ポアンカレ球赤道面の円上で入射直線偏光に対応する点と該円の中心を結ぶ直線とのなす角を求め、その角と旋光角とに基づいて被測定物の真の光学主軸方位を求める請求項４に記載の位相差測定方法。 Obtain an approximate straight line consisting of a plurality of actually measured points on the Poincare sphere equatorial plane obtained in step S1,
Find the angle between the perpendicular line drawn from the center of the circle on the Poincare sphere equatorial plane to the approximate straight line and the line connecting the center of the circle and the point corresponding to the incident linear polarization on the circle on the Poincare sphere equatorial plane. The phase difference measurement method according to claim 4, wherein the true optical principal axis orientation of the object to be measured is obtained based on the rotation angle and the optical rotation angle.
前記近似直線がポアンカレ球赤道面の円と交わる点とポアンカレ球赤道面の円上で入射直線偏光に対応する点とのなす角に基づいて被測定物の旋光角を求め、
ポアンカレ球赤道面の円の中心から前記近似直線に下ろした垂線と、ポアンカレ球赤道面の円上で入射直線偏光に対応する点と該円の中心を結ぶ直線とのなす角を求め、その角と前記旋光角とに基づいて被測定物の真の光学主軸方位を求め、
得られた前記旋光角および前記被測定物の真の光学主軸方位の値をＯＰＴＩＭＡ法の計算時に条件として使用する請求項２に記載の位相差測定方法。 Obtain an approximate straight line consisting of a plurality of actually measured points on the Poincare sphere equatorial plane obtained in step S1,
Obtaining the optical rotation angle of the object to be measured based on the angle between the point where the approximate line intersects the circle of the Poincare sphere equatorial plane and the point corresponding to the incident linearly polarized light on the circle of the Poincare sphere equatorial plane,
Find the angle between the perpendicular line drawn from the center of the circle on the Poincare sphere equatorial plane to the approximate straight line and the line connecting the center of the circle and the point corresponding to the incident linear polarization on the circle on the Poincare sphere equatorial plane. And the true optical principal axis direction of the object to be measured based on the optical rotation angle and the optical rotation angle,
The phase difference measurement method according to claim 2, wherein the obtained optical rotation angle and the value of the true optical principal axis orientation of the object to be measured are used as conditions when calculating the OPTIMA method.
前記演算処理部（１１）は、波長λiごとの検出光強度から回転検光子法又は回転偏光子法の原理に基づいて楕円偏光の楕円率（α／β）i及び楕円方位角Ψiを算出し、さらにそれらの楕円率と楕円方位角に対応する偏光状態をポアンカレ球赤道面に図示したときの点の座標（Ｘi、Ｙi）を求める偏光解析部（１１０）と、
被測定物の位相差の波長分散特性を保持して、その波長分散特性に基づいて基準波長λoでの位相差Ｒoを前記複数の各波長λiでの位相差Ｒiに補正する位相差補正部（１１３）と、
シミュレーションにより、基準波長λoでの位相差Ｒoを変化させながら複数の測定波長λiごとの透過光の楕円率（α／β）isと楕円方位角Ψisを求め、それらの値を基にした各波長での偏光状態に対応する、ポアンカレ球赤道面上の各点の座標（Ｘis、Ｙis）を算出する偏光特性算出部（１１１）と、
偏光特性算出部（１１１）による計算結果の点の座標（Ｘis、Ｙis）について、ポアンカレ球赤道面上において波長λiごとの実測点の座標（Ｘi、Ｙi）との距離を求め、その距離が最も小さくなるときの基準波長λoでの位相差Ｒoを求めてそれを被測定物の位相差とするマッチング部（１１２）と、
を備えている位相差測定装置。 An optical system configured to perform measurement at a plurality of different wavelengths λi so that the measurement light from the light source enters the photodetector through the analyzer from the polarizer, and the transmission axis of the polarizer And a measuring unit (100) in which one of the transmission axes of the analyzer is fixed and the other is rotated, and the object to be measured is arranged between the polarizer and the analyzer, and the measuring unit An arithmetic processing unit (11) for acquiring detection signals at a plurality of wavelengths λi from and obtaining a phase difference of the object to be measured;
The arithmetic processing unit (11) calculates the ellipticity (α / β) i and the elliptical azimuth angle ψi of elliptically polarized light based on the principle of the rotational analyzer method or the rotational polarizer method from the detected light intensity for each wavelength λi. Further, a polarization analysis unit (110) for obtaining coordinates (Xi, Yi) of points when the polarization state corresponding to the ellipticity and the elliptical azimuth is illustrated on the Poincare sphere equatorial plane;
A phase difference correction unit that retains the wavelength dispersion characteristic of the phase difference of the object to be measured and corrects the phase difference Ro at the reference wavelength λo to the phase difference Ri at the plurality of wavelengths λi based on the wavelength dispersion characteristic ( 113)
Through simulation, the ellipticity (α / β) is and elliptical azimuth angle ψis of the transmitted light for each of the plurality of measurement wavelengths λi are obtained while changing the phase difference Ro at the reference wavelength λo, and each wavelength based on these values is obtained. A polarization characteristic calculation unit (111) for calculating coordinates (Xis, Yis) of each point on the Poincare sphere equatorial plane corresponding to the polarization state at
With respect to the coordinates (Xis, Yis) of the point of the calculation result by the polarization characteristic calculation unit (111) , the distance to the coordinates (Xi, Yi) of the actual measurement point for each wavelength λi on the Poincare sphere equatorial plane is obtained. A matching unit (112) that obtains the phase difference Ro at the reference wavelength λo when it becomes smaller and uses it as the phase difference of the object to be measured;
A phase difference measuring apparatus.
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| JP3159743B2 (en) * | 1991-07-11 | 2001-04-23 | 旭光学工業株式会社 | Polarization and birefringence measurement device |
| JPH06289382A (en) * | 1993-03-30 | 1994-10-18 | Hitachi Ltd | Liquid crystal display device |
| JP3539006B2 (en) * | 1994-09-30 | 2004-06-14 | 王子製紙株式会社 | Method and apparatus for measuring retardation of composite layer |
| JP2005091897A (en) * | 2003-09-18 | 2005-04-07 | Sharp Corp | Liquid crystal display |
| JP4926003B2 (en) * | 2007-11-12 | 2012-05-09 | 王子計測機器株式会社 | Polarization analysis method |
| JP5446644B2 (en) * | 2009-09-15 | 2014-03-19 | 王子ホールディングス株式会社 | Bonding angle measuring device for elliptical polarizing plate |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106526920A (en) * | 2016-12-29 | 2017-03-22 | 深圳市华星光电技术有限公司 | Method and device for measuring liquid crystal display compensation film in-plane phase difference values |
| CN106526920B (en) * | 2016-12-29 | 2019-08-20 | 深圳市华星光电技术有限公司 | Liquid crystal display compensates phase difference value measurement method and device in film surface |
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