JP2807965B2 - Small angle cross beam orthogonal two-frequency light source for heterodyne interferometer - Google Patents
Small angle cross beam orthogonal two-frequency light source for heterodyne interferometerInfo
- Publication number
- JP2807965B2 JP2807965B2 JP6108922A JP10892294A JP2807965B2 JP 2807965 B2 JP2807965 B2 JP 2807965B2 JP 6108922 A JP6108922 A JP 6108922A JP 10892294 A JP10892294 A JP 10892294A JP 2807965 B2 JP2807965 B2 JP 2807965B2
- Authority
- JP
- Japan
- Prior art keywords
- light source
- frequency light
- component
- orthogonal
- heterodyne interferometer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Instruments For Measurement Of Length By Optical Means (AREA)
Description
【発明の詳細な説明】これまでの直交２周波数光源で
は，直交２周波数ビームが同一軸上にあるため，この光
源を用いて微小位相計測を行うため，ヘテロダイン干渉
計を構成する場合，ウオラストンプリズムを用いて２点
差動方式の光学系を構成していた。その場合使用された
直交２周波数光源では最終の合波に用いた偏光ビームス
プリッタの反射面に楕円偏光を入射すると反射光の主成
分は垂直成分であるが，平行成分が若干漏れてくるた
め，出射ビームの消光比が悪くなり干渉ビートに余分な
成分が現れてくる。このため，位相計出力の測定位相と
実際の測定対象の位相との関係が非線形になり誤差を生
じる問題があった。本発明は，このような非線型誤差が
生じないように偏光漏れ成分の影響を受けない，微小角
交差ビーム型の直交２周波数光源に関するものである。
本特許の光学系略図を図１に示す。レーザ光源ＬＳ，１
／２波長板ＨＷをとおったビームは電気ベクトルが偏光
ビームスプリッタＰＢＳ１の偏光軸に４５度に入射し，
２ビームに分割される。音響光学素子ＡＯ１，ＡＯ２で
それぞれ周波数偏移をうける。各ビームは偏光ビームス
プリッタＰＢＳ１の不完全性および音響光学素子中の歪
みなどにより楕円偏光になる。偏光ビームスプリッタＰ
ＢＳ２での偏光漏れ成分の影響を除くため，従来の光源
と異なり，これらの出射ビームを空間的に微小な交差角
で交わらせた直交２周波数光源に関する装置である。こ
の装置を用いた差動型ヘテロダイン干渉計変位センサに
おいては，各々２ビームの偏光漏れ成分は，測定位相物
体に独立に照射され，反射されてくるので，同一周波数
成分のビームに独立に存在する。したがって，偏光漏れ
成分の除去は光学的に可能であるが，除去しないで合波
した時にも，非線形性の原因となる漏れ成分の位相差を
含 まない項は直流成分となり，非線形性の原因とならな
い漏れ成分の測定位相差を含む項は交流成分であるビー
ト信号に含まれ，鮮鋭度は悪くなるが，前者の直流成分
と後者の交流成分とは電気フイルタで分離できる。本発
明の装置を用いて，原子間力顕微鏡のカンチレバーの変
位を検出するため，構成した差動型ヘテロダイン干渉計
を図２に示す。直交２周波数光源ＣＬＳから出射したビ
ームは，ビームスプリッタＢＳで分割する。反射ビーム
は円筒レンズＬ１でＣＬＳ内のビーム交差点をウオラス
トンプリズムＷＰ１上に結像する。交差ビームは互いに
平行になる。おのおの直交２周波数ビームを検光子Ａ１
を通して光検知器ＰＤ１上で干渉させ参照ビート信号を
える。なおウオラストンプリズムＷＰ１を通過後，漏れ
成分は，方向が偏向しこの平行ビームからずれるため光
検知器に入射しない。したがって，偏光漏れ成分のビー
ト信号への混合をのぞき信号の鮮鋭度があげることがで
きる。ビームスプリッタＢＳで分割されたビームはレン
ズでＬ２をとおして原子間力顕微鏡のカンチレバー上の
２点に集光される。カンチレバーからの反射光がビーム
スプリッタＢＳで反射されウオラストンプリズムＷＰ２
上で交差し，平行ビームになり，検光子Ａ２をとおして
ＰＤ２上で干渉させ測定ビート信号をえる。なおウオラ
ストンプリズムＷＰ２を通過後，漏れ成分は，方向が偏
向し，平行ビームからずれるため光検知器に入射しな
い。したがって，偏光漏れ成分のビート信号への混合を
のぞき信号の鮮鋭度があげることができる。測定ビート
信号にはカンチレバーの原子間力によるたわみによる２
点での位相差が含まれる。ＰＤ１からの参照ビート信
号，ＰＤ２からの測定ビート信号は位相計に入力され，
たわみによる位相差が検出される。偏光漏れ成分は，ウ
オラストンプリズムで除かれているので，偏光漏れ成分
がビート信号に含まれないから，この測定位相差には，
非線形誤差はない。DETAILED DESCRIPTION OF THE INVENTION In a conventional orthogonal two-frequency light source, since orthogonal two-frequency beams are on the same axis, a minute phase measurement is performed using this light source. An optical system of a two-point differential system is configured using a prism. In this case, when the elliptically polarized light is incident on the reflection surface of the polarization beam splitter used for the final multiplexing in the orthogonal two-frequency light source used, the main component of the reflected light is a vertical component, but the parallel component slightly leaks. As a result, the extinction ratio of the output beam deteriorates, and an extra component appears in the interference beat. For this reason, the measurement phase of the phase meter output and
The relationship with the phase of the actual measurement target becomes non-linear, causing an error.
There was a problem . The present invention relates to a small-angle cross-beam orthogonal two-frequency light source that is not affected by a polarization leakage component so that such a non-linear error does not occur.
A schematic diagram of the optical system of this patent is shown in FIG. Laser light source LS, 1
The electric vector of the beam passing through the half-wave plate HW is incident on the polarization axis of the polarization beam splitter PBS1 at 45 degrees,
It is split into two beams. Each of the acousto-optic devices AO1 and AO2 undergoes frequency shift. Each beam becomes elliptically polarized light due to imperfections of the polarizing beam splitter PBS1 and distortion in the acousto-optic device. Polarizing beam splitter P
In order to eliminate the influence of the polarization leakage component in BS2, unlike a conventional light source, this is an apparatus relating to an orthogonal two-frequency light source in which these emitted beams are spatially crossed at a small intersection angle. This
Type heterodyne interferometer displacement sensor using the same device
In each case, the polarization leakage component of each of the two beams is
Since the body is independently irradiated and reflected, the same frequency
Exists independently in the component beam. Therefore, polarization leakage
Removal of components is possible optically, but multiplexing without removal
The phase difference of the leakage component that causes the nonlinearity
That does not contain terms becomes a DC component, it if the cause of non-linearity
The term containing the measured phase difference of the leakage component is the
Signal, and the sharpness deteriorates, but the former DC component
The latter AC component can be separated from the latter by an electric filter . FIG. 2 shows a differential heterodyne interferometer configured to detect the displacement of a cantilever of an atomic force microscope using the apparatus of the present invention. The beam emitted from the orthogonal two-frequency light source CLS is split by the beam splitter BS. The reflected beam forms an image of the beam intersection in the CLS on the Wollaston prism WP1 by the cylindrical lens L1. The cross beams are parallel to each other. Each orthogonal two-frequency beam is analyzed by the analyzer A1.
Through the light detector PD1 to obtain a reference beat signal. After passing through the Wollaston prism WP1, the leak component does not enter the photodetector because its direction is deflected and deviates from this parallel beam. Therefore, that the sharpness of each Ki signal of the mixing of the beat signal polarized light leakage component mentioned
Wear. The beam split by the beam splitter BS is condensed at two points on the cantilever of the atomic force microscope through L2 by a lens. The reflected light from the cantilever is reflected by the beam splitter BS and the Wollaston prism WP2
The beams cross each other to form a parallel beam, and interfere with the PD2 through the analyzer A2 to obtain a measurement beat signal. After passing through the Wollaston prism WP2, the leakage component is deflected in direction and deviated from the parallel beam, and does not enter the photodetector. Therefore, the mixing of the polarization leakage component into the beat signal
The sharpness of the peep signal can be increased . The measured beat signal contains 2 due to the bending due to the atomic force of the cantilever.
Includes phase differences at points. The reference beat signal from PD1 and the measured beat signal from PD2 are input to the phase meter.
A phase difference due to deflection is detected. The polarization leakage component is
Since the polarization leak component is not included in the beat signal because it has been removed by the Oraston prism , this measured phase difference includes
There are no non-linear errors.
【図１】微小角交差ビーム型直交２周波数光源の略図FIG. 1 is a schematic diagram of a small-angle cross beam orthogonal two-frequency light source.
【図２】図１の光源を利用したヘテロダイン干渉計によ
る原子間力顕微鏡カンチレバー変位検出系の略図2 is a schematic diagram of an atomic force microscope cantilever displacement detection system using a heterodyne interferometer using the light source of FIG.
【符号の説明】 ＬＳ レーザ光源 ＨＷ １／２波長板 ＰＢＳ１，ＰＢＳ２ 偏光ビームスプリッタ Ｍ１，Ｍ２ ミラー用プリズム ＡＯ１，ＡＯ２ 音響光学素子 破線Ｂ１，実線Ｂ２ ビームを示し，各々の電気ベクト
ルの方向が直交 ＣＬＳ 微小角交差ビーム型直交２周波数光源 Ｌ１ 円筒レンズ Ｌ２ 球面レンズ ＢＳ ビームスプリッタ ＷＰ１，ＷＰ２ ウオラストンプリズム Ａ１，Ａ２ 検光子 ＰＤ１，ＰＤ２ 光検知器 ＣＬ カンチレバー ＨＣＬ カンチレバー・ホルダー ＳＰＳ 試料走査部 Ｃ コントローラー[Description of Signs] LS Laser Light Source HW 1/2 Wavelength Plate PBS1, PBS2 Polarizing Beam Splitter M1, M2 Mirror Prism AO1, AO2 Acoustooptic Device Broken Line B1, Solid Line B2 Beams are shown, and the direction of each electric vector is orthogonal CLS Small angle cross beam orthogonal two-frequency light source L1 Cylindrical lens L2 Spherical lens BS Beam splitter WP1, WP2 Wollaston prism A1, A2 Analyzer PD1, PD2 Optical detector CL Cantilever HCL Cantilever holder SPS Sample scanning unit C controller
Claims (1)
素子を用いた直交２周波数光源において，偏光漏れ成分
の影響で発生する位相出力の非線形誤差を除去するた
め，電気ベクトル平行成分のビームと垂直成分のビーム
の出射ビームを水平面上，または垂直面上で空間的に微
小角交差させた装置。1. An orthogonal two-frequency light source using an acousto-optic device used in a heterodyne interferometer to remove a nonlinear error of a phase output generated by the influence of a polarization leakage component. The output beam of the component beam is spatially fine on the horizontal or vertical plane.
A small-angle crossed device .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6108922A JP2807965B2 (en) | 1994-04-11 | 1994-04-11 | Small angle cross beam orthogonal two-frequency light source for heterodyne interferometer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6108922A JP2807965B2 (en) | 1994-04-11 | 1994-04-11 | Small angle cross beam orthogonal two-frequency light source for heterodyne interferometer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07280658A JPH07280658A (en) | 1995-10-27 |
| JP2807965B2 true JP2807965B2 (en) | 1998-10-08 |
Family
ID=14497058
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6108922A Expired - Fee Related JP2807965B2 (en) | 1994-04-11 | 1994-04-11 | Small angle cross beam orthogonal two-frequency light source for heterodyne interferometer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2807965B2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1751491B1 (en) * | 2004-05-11 | 2014-11-05 | Renishaw plc | Polarising interferometer with removal or separation of error beam caused by leakage of polarised light |
| GB0617945D0 (en) * | 2006-09-12 | 2006-10-18 | Ucl Business Plc | Imaging apparatus and methods |
| CN102928076B (en) * | 2012-11-26 | 2014-08-20 | 核工业理化工程研究院 | Laser real-time power monitoring device and monitoring method free from influence of polarization degree |
| CN104990619B (en) * | 2015-06-12 | 2016-06-29 | 哈尔滨工业大学 | Michelson heterodyne laser vialog based on dual-acousto-optic modulation and depolarization light splitting |
| CN104880244B (en) * | 2015-06-12 | 2017-11-10 | 哈尔滨工业大学 | The Michelson heterodyne laser vialog being divided based on monophone light modulation and depolarization |
| CN105571516A (en) * | 2016-01-05 | 2016-05-11 | 中国科学院光电研究院 | Full field of view low frequency heterodyne interferometer |
| RU2645005C1 (en) * | 2016-11-18 | 2018-02-15 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный технологический университет "СТАНКИН" (ФГБОУ ВО "МГТУ "СТАНКИН") | Laser interferometer |
| CN110926360B (en) * | 2019-11-18 | 2021-09-21 | 中国科学院光电研究院 | Device for measuring free-form surface by full-field external differential phase shift |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05302810A (en) * | 1992-04-28 | 1993-11-16 | Nikon Corp | Heterodyne two wave lengths displacement interference meter |
-
1994
- 1994-04-11 JP JP6108922A patent/JP2807965B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07280658A (en) | 1995-10-27 |
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