JP4869656B2 - Interferometer - Google Patents

Interferometer Download PDF

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JP4869656B2
JP4869656B2 JP2005229312A JP2005229312A JP4869656B2 JP 4869656 B2 JP4869656 B2 JP 4869656B2 JP 2005229312 A JP2005229312 A JP 2005229312A JP 2005229312 A JP2005229312 A JP 2005229312A JP 4869656 B2 JP4869656 B2 JP 4869656B2
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light
combined
phase shift
reflected
polarization
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JP2007046938A (en
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義将 鈴木
和彦 川▼崎▲
慎一郎 谷中
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Mitutoyo Corp
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Description

本発明は、位相シフト法を用いた干渉計に関する。   The present invention relates to an interferometer using a phase shift method.

被測定物の表面形状を高精度に測定する装置として干渉計が知られている。干渉計は基準となる参照面からの反射光（参照光）と、測定対象物からの反射光（測定光）とを合成させて干渉縞を発生させ、この干渉縞を解析することにより参照面に対する被測定物の相対的な形状を測定するものである。干渉計には様々なタイプのものがあるが、中でもフィゾー型干渉計は構成が簡単で且つ参照光と測定光が共通光路を通るため高い測定精度が見込めるものとして知られている。   An interferometer is known as an apparatus for measuring the surface shape of an object to be measured with high accuracy. The interferometer generates interference fringes by combining the reflected light (reference light) from the reference surface as a reference and the reflected light (measurement light) from the object to be measured, and analyzes the interference fringes to generate a reference surface. Measure the relative shape of the object to be measured. There are various types of interferometers. Among them, the Fizeau interferometer is known to have a simple configuration and high measurement accuracy because the reference light and the measurement light pass through a common optical path.

また、干渉計により得られた干渉縞の解析方法として、位相シフト法が知られている。位相シフト法は、参照面を光軸方向に変位させるなどの手法により、干渉縞の位相をシフトさせつつ複数枚の干渉縞画像を取得して被測定物の形状を算出する方法である。高い精度が得られるため、現在では、多くの干渉計に適用されている。   A phase shift method is known as an analysis method of interference fringes obtained by an interferometer. The phase shift method is a method of calculating the shape of the object to be measured by acquiring a plurality of interference fringe images while shifting the phase of the interference fringes by a method such as displacing the reference surface in the optical axis direction. Since high accuracy is obtained, it is currently applied to many interferometers.

しかし、参照面を変位させながら干渉縞を取得する方法のため、測定に時間を要する。また、干渉縞を取得する間、被測定物を静定している必要があるため、振動などの揺らぎを排除した特別な環境下で測定を行う必要がある。   However, it takes time to measure because of the method of acquiring interference fringes while displacing the reference surface. In addition, since it is necessary to stabilize the object to be measured while acquiring the interference fringes, it is necessary to perform measurement in a special environment that eliminates fluctuations such as vibration.

これに対し、複数の撮像素子を用いて、光学的に位相をシフトさせた干渉縞を同時に撮像する方法が、例えば特許文献１、２により知られている。この方法によれば、位相シフト法で演算処理するのに必要な枚数の干渉縞画像を瞬時に取り込むことができるため測定の高速化が図れる。また、振動条件下での測定も可能になる。   On the other hand, for example, Patent Documents 1 and 2 disclose a method of simultaneously imaging interference fringes whose phases are optically shifted using a plurality of imaging elements. According to this method, the number of interference fringe images required for the arithmetic processing by the phase shift method can be instantaneously captured, so that the measurement speed can be increased. Also, measurement under vibration conditions is possible.

しかし、この光学位相シフト干渉計では、参照光と測定光の偏光面を互いに直交させる必要があるため、１／４波長板が不可欠となる。しかし、１／４波長板を製造するには、合成石英などの複屈折性の光学材料を数μｍオーダーの高精度で加工する必要がある。このため、１／４波長板は一般的に高価であり、光学位相シフト干渉計の価格上昇の原因となっている。直径５０ｍｍ以上の大きな１／４波長板は特に入手が困難であり、また入手できても非常に高価なものとなる。このため、こうした干渉計の測定領域は、限られた小さな領域に限定されてしまい望ましくない。
特開平５−８７５４１号公報 特開２０００−３２９５３５号公報 However, in this optical phase shift interferometer, since the polarization planes of the reference light and the measurement light need to be orthogonal to each other, a quarter wavelength plate is indispensable. However, in order to manufacture a quarter-wave plate, it is necessary to process a birefringent optical material such as synthetic quartz with high accuracy on the order of several μm. For this reason, the quarter-wave plate is generally expensive and causes an increase in the price of the optical phase shift interferometer. Large quarter-wave plates having a diameter of 50 mm or more are particularly difficult to obtain, and even if available, they are very expensive. For this reason, the measurement area of such an interferometer is limited to a limited small area, which is not desirable.
Japanese Patent Laid-Open No. 5-87541 JP 2000-329535 A

本発明は、高価な波長板を必要とせず、また大口径で測定領域の広域化も可能な干渉計を提供することを目的とする。   It is an object of the present invention to provide an interferometer that does not require an expensive wave plate and that can have a large aperture and a wide measurement area.

上記目的を達成するため、本発明に係るフィゾー型干渉計は、光源と、前記光源が出射する出射光のうち第１方向の偏光成分を有する第１の光を透過させる一方前記第１方向と直交する第２方向の偏光成分を有する第２の光を反射させ、且つ前記第１の光又は前記第２の光のいずれか一方を被測定物で反射させて測定光とする一方他方を参照面で反射させて参照光として前記測定光と前記参照光を合成して合成光とする偏光部材と、前記合成光を位相シフトさせる位相シフト部と、前記位相シフト部により複数通りの異なる位相シフトを与えられた前記合成光による干渉縞画像を撮像する撮像部とを備え、前記偏光部材は、その反射面が前記出射光に対し垂直となるように設置されると共に前記反射面が前記参照面を兼用されるように構成され、前記第１の光は、前記被測定物で反射した後、前記偏光部材を通過して前記第２の光と合成されることにより前記合成光とされることを特徴とする。
In order to achieve the above object, a Fizeau interferometer according to the present invention transmits a first light having a polarization component in a first direction out of emitted light emitted from the light source and the first direction. Reference is made to the other light which reflects the second light having the polarization component in the second direction orthogonal to each other and reflects either the first light or the second light by the object to be measured to obtain the measurement light. A polarizing member that is reflected by a surface and combines the measurement light and the reference light as reference light to be combined light, a phase shift unit that shifts the phase of the combined light, and a plurality of different phase shifts by the phase shift unit And an imaging unit that captures an interference fringe image by the combined light, and the polarizing member is installed so that a reflection surface thereof is perpendicular to the emitted light, and the reflection surface is the reference surface Constructed to be combined Said first light, said after being reflected by the object to be measured, characterized in that it is with the synthesized light by the being through the polarization member combined with the second light.

この発明によれば、偏光部材により、測定光と参照光とが互いに直交する偏光成分を有する光とされる。このため、高価な波長板を必要とせず、また大口径で測定領域の広域化も可能な干渉計を提供することが可能となる。   According to the present invention, the polarizing member causes the measurement light and the reference light to be light having polarization components that are orthogonal to each other. For this reason, it becomes possible to provide an interferometer that does not require an expensive wave plate and that can have a large aperture and a wide measurement area.

次に、本発明の実施の形態を、図面を参照して詳細に説明する。   Next, embodiments of the present invention will be described in detail with reference to the drawings.

［第１の実施の形態］ 図１は、本発明の第１の実施の形態に係るフィゾー型干渉計の全体構成を示している。対比のため、図８に従来の干渉計の全体構成を示す。両者間で同一の構成部材については同一の符号を付して説明する。   First Embodiment FIG. 1 shows the overall configuration of a Fizeau interferometer according to a first embodiment of the present invention. For comparison, FIG. 8 shows the overall configuration of a conventional interferometer. The same constituent members will be described with the same reference numerals.

最初に図８の従来の干渉計について説明する。この干渉計において、光源１０１から出射された出射光は、集光レンズ１０２により集光されピンホール１０３に照射される。ここでは、ビームスプリッタ１０４の入射面に対しｐ偏光の光が光源１０１から出射されているものとする。ピンホール１０３の点光源からの光がビームスプリッタ１０４を通過してコリメータレンズ１０５により平行光とされる。この平行光の一部は、参照面１０６、１／４波長板１０７を通過して被測定物Ｗに至る。残りは参照面１０６で反射されて参照光（ｐ偏光）とされる。１／４波長板１０７は、通過するｐ偏光の光を円偏光に変換する。この円偏光の光は被測定物Ｗで反射されて測定光とされる。この測定光は、１／４波長板１０７を通過することにより、ｓ偏光に変換される。参照面１０６を通過したｓ偏光の測定光は、ｐ偏光の参照光と合成されてｐ偏光成分とｓ偏光成分とを含む合成光とされるが、両者の偏光方向が垂直であるため合成されても光の干渉は生じない。   First, the conventional interferometer of FIG. 8 will be described. In this interferometer, the emitted light emitted from the light source 101 is condensed by the condenser lens 102 and irradiated to the pinhole 103. Here, it is assumed that p-polarized light is emitted from the light source 101 to the incident surface of the beam splitter 104. Light from the point light source of the pinhole 103 passes through the beam splitter 104 and is collimated by the collimator lens 105. Part of this parallel light passes through the reference surface 106 and the quarter-wave plate 107 and reaches the object W to be measured. The rest is reflected by the reference surface 106 to become reference light (p-polarized light). The quarter wavelength plate 107 converts the p-polarized light passing therethrough into circularly polarized light. This circularly polarized light is reflected by the object W to be measured and used as measurement light. This measurement light passes through the quarter-wave plate 107 and is converted into s-polarized light. The s-polarized measurement light that has passed through the reference surface 106 is combined with the p-polarized reference light to be a combined light including a p-polarized component and an s-polarized component, but is synthesized because the polarization directions of both are perpendicular. However, no light interference occurs.

合成光はビームスプリッタ１０４で反射された後、１／４波長板１０８を通過し、左回り円偏光成分と右回り円偏光成分とを含む光に変換される。この変換後の合成光が、無偏光ビームスプリッタ１１３Ａ、１１３Ｂ及びミラー１１３Ｃにより３つの光に分割され、偏光板１１４Ａ、１１４Ｂ及び１１４Ｃにより異なる位相シフト量を与えられる。偏光板１１４Ａ−Ｃは、図９に示すように、透過軸方向０°、４５°、９０°と４５度ずつ異なっており、これらを通過した３つの分割光の位相を９０度ずつ異ならせる（０°、９０°、１８０°）ようにするものである。この異なる位相シフト量を与えられた複数の干渉縞画像をそれぞれＣＣＤ撮像素子１０９Ａ、１０９Ｂ及び１０９Ｃにより撮像する。   The combined light is reflected by the beam splitter 104, passes through the quarter-wave plate 108, and is converted into light including a counterclockwise circularly polarized component and a clockwise circularly polarized component. The converted combined light is divided into three lights by the non-polarizing beam splitters 113A and 113B and the mirror 113C, and different phase shift amounts are given by the polarizing plates 114A, 114B and 114C. As shown in FIG. 9, the polarizing plates 114A-C are different from each other by 45 degrees in the transmission axis directions 0 °, 45 °, and 90 °, and the phases of the three divided lights that have passed through these are varied by 90 degrees ( 0 °, 90 °, 180 °). A plurality of interference fringe images given different phase shift amounts are picked up by the CCD image pickup devices 109A, 109B and 109C, respectively.

この図８の干渉計では、１／４波長板１０７が測定光と参照光の偏光方向を直交させるために必要であるが、この１／４波長板１０７は高価格であり大型のものが入手困難のため測定領域の広域化が困難であった。   In the interferometer of FIG. 8, the quarter wavelength plate 107 is necessary to make the polarization directions of the measurement light and the reference light orthogonal, but this quarter wavelength plate 107 is expensive and has a large size. Due to the difficulty, it was difficult to widen the measurement area.

これに対し、図１に示す本発明の第１の実施の形態のフィゾー型干渉計は、１／４波長板１０７に代えて偏光板１１８を設け、これにより参照光と測定光の偏光方向を直交させている。また、この偏光板１１８の反射面を参照面として機能させ、偏光板１１８と被測定物Ｗを同一光路上に配置するフィゾー型干渉計としているため、別途参照面を用意する必要を無くしている。この偏光板１１８は、透過する光を測定光とし、反射する光を参照光として両者を合成する合成部材としても機能している。   In contrast, the Fizeau interferometer according to the first embodiment of the present invention shown in FIG. 1 is provided with a polarizing plate 118 in place of the quarter-wave plate 107, thereby changing the polarization directions of the reference light and the measuring light. It is orthogonal. Further, since the reflection surface of the polarizing plate 118 functions as a reference surface and a Fizeau interferometer in which the polarizing plate 118 and the object to be measured W are arranged on the same optical path, it is not necessary to prepare a separate reference surface. . The polarizing plate 118 also functions as a combining member that combines the transmitted light as measurement light and the reflected light as reference light.

偏光板１１８は、例えば図２に示すように、透明ガラス基板１８Ａと、この透明ガラス基板１８Ａの上に等間隔で形成されたワイヤグリッド（金属線格子）１８Ｂとを備えている。ワイヤグリッド１８Ｂは、例えばアルミニウムにより形成され、例えば線幅６５ｎｍ、厚さ１００〜２００ｎｍ、ピッチ１４４ｎｍで形成することができる。ワイヤグリッド１８Ｂは、半導体製造工程において用いられるフォトリソグラフィとエッチングにより生成することができ、１／４波長板に比べ安価に製造することができる。また、この方法の場合、直径数百ｍｍの偏光板も容易に作成することが可能であり、測定領域の広域化への対応も容易である。なお、このように構成されたワイヤグリッド型の偏光板１１８は、ワイヤグリッド１８Ｂの長手方向と平行方向の偏光成分を反射し、垂直方向の偏光成分を透過する性質を有する。この点、一般に使用される、基材フィルムにヨウ素等を吸着させ延伸・配向させることで生成される一般的な偏光板とは異なっている。   For example, as shown in FIG. 2, the polarizing plate 118 includes a transparent glass substrate 18A and wire grids (metal wire lattices) 18B formed on the transparent glass substrate 18A at equal intervals. The wire grid 18B is made of, for example, aluminum, and can be formed with, for example, a line width of 65 nm, a thickness of 100 to 200 nm, and a pitch of 144 nm. The wire grid 18B can be generated by photolithography and etching used in the semiconductor manufacturing process, and can be manufactured at a lower cost than a quarter-wave plate. In the case of this method, a polarizing plate having a diameter of several hundreds of millimeters can be easily produced, and it is easy to cope with widening the measurement region. The wire grid type polarizing plate 118 configured as described above has a property of reflecting a polarization component in a direction parallel to the longitudinal direction of the wire grid 18B and transmitting a polarization component in a vertical direction. In this respect, it is different from a generally used polarizing plate produced by adsorbing iodine or the like on a base film and stretching and orienting it.

［第２の実施の形態］
次に、本発明の第２の実施の形態に係る干渉計を図３を参照して説明する。第１の実施の形態の干渉計と同一の構成部材については同一の符号を付しその詳細な説明は省略する。この実施の形態の干渉計は、偏光板１１８'が設けられ１／４波長板１０７（図８）を不要としている点で第１の実施の形態と共通している。しかし、偏光板１１８'は、光源１０１からの光の入射光軸に対して斜めに設置され、透過側に被測定物Ｗが、反射側に参照面１２０が設置されるものである点で、第１の実施の形態と異なっている。この構成において、偏光板１１８'で反射したｐ偏光の光は参照面１２０で反射して偏光板１１８'で再び反射される。一方、偏光板１１８'を透過したｓ偏光の光は被測定物Ｗで反射して偏光板１１８'を再び透過する。このｐ偏光の光とｓ偏光の光とが、合成部材としても機能する偏光板１１８'により合成され、ビームスプリッタ１０４で反射され集光レンズ１２１で集光された後偏光板１１４Ａ〜Ｃで位相シフトを与えられる。これにより、位相シフト法による干渉計測が、第１の実施の形態と同様に実施可能となる。 [Second Embodiment]
Next, an interferometer according to a second embodiment of the present invention will be described with reference to FIG. The same components as those of the interferometer of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The interferometer of this embodiment is common to the first embodiment in that a polarizing plate 118 ′ is provided and the quarter-wave plate 107 (FIG. 8) is unnecessary. However, the polarizing plate 118 ′ is installed obliquely with respect to the incident optical axis of the light from the light source 101, and the object to be measured W is installed on the transmission side, and the reference surface 120 is installed on the reflection side. This is different from the first embodiment. In this configuration, the p-polarized light reflected by the polarizing plate 118 ′ is reflected by the reference surface 120 and is reflected again by the polarizing plate 118 ′. On the other hand, the s-polarized light transmitted through the polarizing plate 118 ′ is reflected by the object to be measured W and is transmitted again through the polarizing plate 118 ′. The p-polarized light and s-polarized light are combined by the polarizing plate 118 ′ that also functions as a combining member, reflected by the beam splitter 104, collected by the condensing lens 121, and then phase-shifted by the polarizing plates 114 </ b> A to 114 </ b> C. Given a shift. Thereby, the interference measurement by the phase shift method can be performed in the same manner as in the first embodiment.

［第３の実施の形態］ 次に、本発明の第３の実施の形態の干渉計を図４を参照して説明する。この実施の形態の干渉計は、第１の実施の形態と同様に、偏光板１１８を入射光の光軸に垂直に配置して偏光板１１８の反射面を参照面として機能させ別個の参照面を不要にしている。ただしこの実施の形態では、ビームスプリッタ１０４以降の位相シフトのための１／４波長板及び偏光板の構成が第１の実施の形態と異なっている。すなわち、この実施の形態では、ビームスプリッタ１０４とビームスプリッタ１１３Ａの間の１／４波長板１０８を省略し、ｐ偏光とｓ偏光の合成光をそのままビームスプリッタ１１３Ａ、１１３Ｂ及びミラー１１３Ｃにより分割すると共に、ビームスプリッタ１１３Ａ〜Ｃによる分岐後の偏光部材等を、図５に示すように構成している。偏光板１１４Ａ、１１４Ｂ、１１４Ｃの透過軸方向は、それぞれ角度α、α、α＋９０°としている。すなわち、偏光板１１４Ａと１１４Ｂの透過軸方向は等しくされている。しかし、偏光板１１４Ｂの前には、更に１／４波長板１２２が配置されている。１／４波長板１２２の進相軸方位及び遅相軸方位は、参照光及び測定光の偏光方向に一致させている。
これにより、ＣＣＤ撮像素子１０９Ｂで撮像される干渉縞の位相は、ＣＣＤ撮像素子１０９Ａで撮像される干渉縞の位相とは９０°異なったものとすることができる。一方、偏光板１１４Ｃの透過軸方向はα＋９０°とされているため、ＣＣＤ撮像素子１０９Ａで撮像される干渉縞と、ＣＣＤ撮像素子１０９Ｃで撮像される干渉縞との間には、１８０°の位相シフトが生じる。このため、第１の実施の形態と同様に、複数通りの位相シフトを与えられた干渉縞を得ることが出来る。 [Third Embodiment] Next, an interferometer according to a third embodiment of the present invention will be described with reference to FIG. In the interferometer of this embodiment, as in the first embodiment, the polarizing plate 118 is arranged perpendicular to the optical axis of the incident light, and the reflecting surface of the polarizing plate 118 functions as a reference surface. Is unnecessary. However, in this embodiment, the configuration of a quarter-wave plate and a polarizing plate for phase shift after the beam splitter 104 is different from that of the first embodiment. That is, in this embodiment, the quarter wavelength plate 108 between the beam splitter 104 and the beam splitter 113A is omitted, and the combined light of p-polarized light and s-polarized light is split as it is by the beam splitters 113A and 113B and the mirror 113C. The polarization members after branching by the beam splitters 113A to 113C are configured as shown in FIG. The transmission axis directions of the polarizing plates 114A, 114B, and 114C are set to angles α, α, and α + 90 °, respectively. That is, the transmission axis directions of the polarizing plates 114A and 114B are equal. However, a quarter-wave plate 122 is further disposed in front of the polarizing plate 114B. The fast axis direction and slow axis direction of the quarter-wave plate 122 are matched with the polarization directions of the reference light and the measurement light.
Thereby, the phase of the interference fringe imaged by the CCD image sensor 109B can be 90 ° different from the phase of the interference fringe imaged by the CCD image sensor 109A. On the other hand, since the transmission axis direction of the polarizing plate 114C is α + 90 °, a phase of 180 ° is formed between the interference fringe imaged by the CCD image sensor 109A and the interference fringe imaged by the CCD image sensor 109C. A shift occurs. For this reason, as in the first embodiment, it is possible to obtain interference fringes given a plurality of types of phase shifts.

［第４の実施の形態］ 次に、本発明の第４の実施の形態の干渉計を図６を参照して説明する。この実施の形態の干渉計は、干渉縞の位相シフトを光学的に行うのではなく、図６に示すように、参照面として機能する偏光板１１８を光軸方向に移動させることにより位相シフトを生じさせる。このため、ビームスプリッタ１１３Ａ、１１３Ｂ、及びミラー１１３Ｃは省略され、ＣＣＤ撮像素子１０９は１台のみ用意すればよく、構成は上記実施の形態に比べ簡略化することができる。   [Fourth Embodiment] Next, an interferometer according to a fourth embodiment of the present invention will be described with reference to FIG. The interferometer of this embodiment does not optically shift the phase of the interference fringes, but shifts the phase shift by moving the polarizing plate 118 functioning as a reference surface in the optical axis direction as shown in FIG. Cause it to occur. For this reason, the beam splitters 113A and 113B and the mirror 113C are omitted, and only one CCD image sensor 109 needs to be prepared, and the configuration can be simplified compared to the above embodiment.

また、この実施の形態の干渉計は、参照光と測定光の強度比を調整するため、偏光板１３１と偏光板１３２とを備えている。偏光板１３１は回転可能に保持されてその透過軸方位を変更することができるようにされている。   In addition, the interferometer of this embodiment includes a polarizing plate 131 and a polarizing plate 132 in order to adjust the intensity ratio between the reference light and the measuring light. The polarizing plate 131 is rotatably held so that its transmission axis direction can be changed.

被測定物Ｗの材質は、ガラス、金属など様々であり、それぞれ反射率が異なる。
反射率が小さいと測定光の強度が参照光の強度に比べ小さくなる。この強度の差が大きくなると、干渉計測の精度が低下してしまう。そこで本実施の形態では、被測定物Ｗの反射率に応じて偏光板１３１の透過軸方位を変更し、これにより偏光板１１８に入射する光の偏光方向を変え、これにより参照光と測定光の強度比を調整している。このようにすることにより、参照光と測定光の強度の差を少なくすることができ、Ｓ／Ｎ比の高い干渉計測を行うことができる。なお、このような偏光板１３１は、上記第１、第２の実施の形態のような光学的位相シフトを用いた干渉計においても採用することが可能である。また、図７に示すように、偏光板１３１を省略すると共に、偏光板１３２を被測定物Ｗの反射率に応じて回転させるようにしても同様の効果を得ることができる。 The material of the object to be measured W is various, such as glass and metal, and has different reflectivities.
When the reflectance is small, the intensity of the measurement light is smaller than the intensity of the reference light. When this difference in intensity increases, the accuracy of interference measurement decreases. Therefore, in the present embodiment, the transmission axis direction of the polarizing plate 131 is changed in accordance with the reflectance of the object to be measured W, thereby changing the polarization direction of the light incident on the polarizing plate 118, thereby the reference light and the measuring light. The intensity ratio is adjusted. By doing so, the difference in intensity between the reference light and the measurement light can be reduced, and interference measurement with a high S / N ratio can be performed. Such a polarizing plate 131 can also be employed in an interferometer using an optical phase shift as in the first and second embodiments. Further, as shown in FIG. 7, the same effect can be obtained by omitting the polarizing plate 131 and rotating the polarizing plate 132 in accordance with the reflectance of the object W to be measured.

以上、発明の実施の形態を説明したが、本発明はこれらに限定されるものではなく、発明の趣旨を逸脱しない範囲内において、種々の変更、追加等が可能である。例えば、ＣＣＤカメラ２０９Ａ−Ｃを複数台準備する例を説明したが、これに限らず、光路切替部材による切替を行うこと等により、１台のＣＣＤカメラのみで撮像を行うことも可能である。また、上記の実施の形態では、参照面と被測定物が同一光路上に存在するフィゾー干渉計を説明したが、本発明は、これに限らず、両者が別光路に存在するマイケルソン型干渉計等にも適用可能である。フィゾー型干渉計に適用する場合、偏光板１１８は参照光と測定光を合成する合成部材として機能させることができるが、マイケルソン型の干渉計の場合には、別途光分割・合成部材を用意することにより、参照光と測定光を合成することができる。   Although the embodiments of the invention have been described above, the present invention is not limited to these embodiments, and various modifications and additions can be made without departing from the spirit of the invention. For example, an example in which a plurality of CCD cameras 209A-C are prepared has been described. However, the present invention is not limited to this, and it is also possible to perform imaging with only one CCD camera by switching with an optical path switching member. In the above embodiment, the Fizeau interferometer has been described in which the reference surface and the object to be measured are on the same optical path. However, the present invention is not limited to this, and the Michelson type interference in which both exist in different optical paths. It is also applicable to totals. When applied to a Fizeau interferometer, the polarizing plate 118 can function as a combining member that combines reference light and measurement light. However, in the case of a Michelson interferometer, a separate light splitting and combining member is prepared. By doing so, the reference light and the measurement light can be synthesized.

本発明の第１の実施の形態に係る干渉計の構成を示している。1 shows a configuration of an interferometer according to a first embodiment of the present invention. 図１の偏光板１１８の構造を示す。The structure of the polarizing plate 118 of FIG. 1 is shown. 本発明の第２の実施の形態に係る干渉計の構成を示している。The structure of the interferometer which concerns on the 2nd Embodiment of this invention is shown. 本発明の第３の実施の形態に係る干渉計の構成を示している。3 shows a configuration of an interferometer according to a third embodiment of the present invention. 図４に示す１／４波長板１２２及び偏光板１１４Ａ〜Ｃを示している。The quarter wave plate 122 and polarizing plates 114A to 114C shown in FIG. 4 are shown. 本発明の第４の実施の形態に係る干渉計の構成を示している。The structure of the interferometer which concerns on the 4th Embodiment of this invention is shown. 第４の実施の形態の変形例に係る干渉計の構成を示している。The structure of the interferometer which concerns on the modification of 4th Embodiment is shown. 従来の干渉計の構成を示している。The structure of the conventional interferometer is shown. 図８の従来の干渉計の偏光板１１４Ａの構成を説明している。The configuration of the polarizing plate 114A of the conventional interferometer of FIG. 8 will be described.

符号の説明Explanation of symbols

１０１・・・光源、 １０２・・・集光レンズ、 １０３・・・ピンホール、 １０４・・・ビームスプリッタ、 １０５・・・コリメータレンズ、 １０６・・・参照面、 １０７・・・１／４波長板、 Ｗ・・・被測定物、 １０８・・・１／４波長板、 １１３Ａ、１１３Ｂ・・・無偏光ビームスプリッタ、 １１３・・・ミラー、 １１４Ａ、１１４Ｂ、１１４Ｃ・・・偏光板、 １０９Ａ、１０９Ｂ、１０９・・・ＣＣＤ撮像素子、 １１８、１１８'・・・偏光板、 １２１・・・レンズ、 １８Ａ・・・透明ガラス基板、 １８Ｂ・・・ワイヤグリッド（金属線格子）、 １３１、１３２・・・偏光板。
DESCRIPTION OF SYMBOLS 101 ... Light source, 102 ... Condensing lens, 103 ... Pinhole, 104 ... Beam splitter, 105 ... Collimator lens, 106 ... Reference surface, 107 ... 1/4 wavelength Plate, W ... object to be measured, 108 ... quarter wave plate, 113A, 113B ... non-polarizing beam splitter, 113 ... mirror, 114A, 114B, 114C ... polarizing plate, 109A, 109B, 109 ... CCD image sensor, 118, 118 '... polarizing plate, 121 ... lens, 18A ... transparent glass substrate, 18B ... wire grid (metal wire grid), 131, 132 ··Polarizer.

Claims (6)

光源と、
前記光源が出射する出射光のうち第１方向の偏光成分を有する第１の光を透過させる一方前記第１方向と直交する第２方向の偏光成分を有する第２の光を反射させ、且つ前記第１の光又は前記第２の光のいずれか一方を被測定物で反射させて測定光とする一方他方を参照面で反射させて参照光として前記測定光と前記参照光を合成して合成光とする偏光部材と、
前記合成光を位相シフトさせる位相シフト部と、
前記位相シフト部により複数通りの異なる位相シフトを与えられた前記合成光による干渉縞画像を撮像する撮像部と
を備え、
前記偏光部材は、その反射面が前記出射光に対し垂直となるように設置されると共に前記反射面が前記参照面を兼用されるように構成され、
前記第１の光は、前記被測定物で反射した後、前記偏光部材を通過して前記第２の光と合成されることにより前記合成光とされる
ことを特徴とするフィゾー型干渉計。 A light source;
Of the outgoing light emitted from the light source, the first light having the polarization component in the first direction is transmitted, while the second light having the polarization component in the second direction orthogonal to the first direction is reflected, and the Either the first light or the second light is reflected by the object to be measured to be measured light, and the other is reflected by the reference surface, and the measurement light and the reference light are combined as reference light and combined. A polarizing member for light;
A phase shift unit for phase shifting the combined light;
An imaging unit that captures an interference fringe image with the combined light that has been given a plurality of different phase shifts by the phase shift unit, and
The polarizing member is configured so that a reflection surface thereof is perpendicular to the emitted light, and the reflection surface is also used as the reference surface,
The Fizeau interferometer, wherein the first light is reflected by the object to be measured, passes through the polarizing member, and is combined with the second light to be the combined light. 前記偏光部材は、透明基板と、この透明基板の上に等間隔で形成された金属線格子とを備えたものであることを特徴とする請求項１記載のフィゾー型干渉計。 2. The Fizeau interferometer according to claim 1, wherein the polarizing member comprises a transparent substrate and a metal wire grating formed on the transparent substrate at equal intervals. 前記金属線格子は、前記透明基板上にフォトリソグラフィとエッチングにより形成されるものである請求項２記載のフィゾー型干渉計。 3. The Fizeau interferometer according to claim 2, wherein the metal line grating is formed on the transparent substrate by photolithography and etching. 前記合成光を複数の光に分割する光分割手段を更に備え、
前記位相シフト部は、光学部材を用いて分割された前記複数の光に異なる位相シフトを与えるものである請求項１記載のフィゾー型干渉計。 A light splitting means for splitting the combined light into a plurality of lights;
2. The Fizeau interferometer according to claim 1, wherein the phase shift unit gives different phase shifts to the plurality of lights divided by using an optical member. 前記位相シフト部は、前記参照面を移動させることにより前記合成光に位相シフトを与えるものである請求項１記載のフィゾー型干渉計。 The Fizeau interferometer according to claim 1, wherein the phase shift unit gives a phase shift to the combined light by moving the reference surface. 前記出射光の偏光方向を変更して前記参照光と前記測定光との強度比を調整するため、前記偏光部材と前記光源との間に別の偏光部材を備えたことを特徴とする請求項１記載のフィゾー型干渉計。 The polarization member of the present invention is provided with another polarization member between the polarization member and the light source in order to adjust the intensity ratio between the reference light and the measurement light by changing the polarization direction of the emitted light. 1. The Fizeau interferometer according to 1.
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