CN105928454B - A kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers - Google Patents
A kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers Download PDFInfo
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- CN105928454B CN105928454B CN201610237366.XA CN201610237366A CN105928454B CN 105928454 B CN105928454 B CN 105928454B CN 201610237366 A CN201610237366 A CN 201610237366A CN 105928454 B CN105928454 B CN 105928454B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
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Abstract
The invention discloses a kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers, use acousto-optic frequency shifters difference interference phase shift, effectively avoid interference with instrument there are movement parts, and measurement accuracy further increases, and anti-interference is good, and development difficulty can be reduced with cost；Particularly with the measurement of heavy caliber face shape, advantage same compared to Mechanical Driven is become apparent from；Meanwhile the measurable mirror surface relative aperture of optical fiber point-diffraction interferometer is increased with two beam spot diffraction lights respectively as reference light and measurement light using the scheme of double fiber stubs.
Description
Technical field
The present invention relates to optical technical field more particularly to a kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers.
Background technique
Using deep-UV lithography machine projection exposure system therefor as the advanced optical equipment of representative, processing, optics to optical element
The integrated of system proposes great challenge.Interferometer integrates indispensable as high-precision optical element processing and optical system
Core detection device, detection accuracy require to be continuously improved.
The surface characterization test method used in traditional optical processing includes Hartmann sensor method, knife-edge method and consistency profiles
Deng.These methods, which are respectively present non-digitalization, needs the different disadvantage of subjective interpretation or contact damage part to be measured etc., and is difficult to reach
It is simple method for measuring to higher measurement accuracy.
Interference detection method is just used before a century, belongs to non-contact measurement, and has wide range, highly sensitive
The features such as degree, high-precision, is widely used when high-precision detects, and principle is the reference planes conduct of light beam irradiation standard
Reference light, another Shu Guangzhao penetrates tested surface and returns with face shape information as measurement light, due to hot spot difference when two-beam is interfered
Position phase difference generates optical path difference to generate curved interference fringe, that is, can determine whether that the face shape of tested surface rises and falls.Until
Bruning in 1974 et al. proposes Phase-Shifting Interferometry, and locking phase Detection Techniques in Communication Theory are introduced into optical interference
In art, so that the precision of interference detection spherical surface shape greatly improves.
Traditional spherical interference detection method is all reference needed for being obtained using a reference spherical surface with higher surface figure accuracy
Corrugated, and then be compared with the detection corrugated containing tested surface shape information, thus obtain tested surface graphic data.Thus standard mirror
The surface figure accuracy of the upper plane of reference directly limits detection accuracy achieved by conventional interference system, and point-diffraction interferometer
The emergence and development of (Point Diffraction Interferometer, abbreviation PDI) have well solved the problem.Point spreads out
The basic thought for penetrating spherical interference detection technique is that ideal spherical wave is obtained using diffraction principle, and will be before diffracted wave
A part is used as reference wavefront, and another part can realize the high-precision detection of spherical surface shape as detection wavefront.Using point
Diffraction principle obtains ideal spherical face wavefront, avoids in conventional interference detection system and system is examined due to standard mirror surface-shaped error
The limitation of precision is surveyed, thus can achieve the resolution ratio of diffraction limit performance, and makes detection accuracy that there is preferable reproducibility.
It is different according to the acquisition modes before diffracted wave, a diffractive spherical interference detection method can be divided into optical fiber point-diffraction and done
Relate to detection method and pin hole point-diffraction interference detection method.
Current optical fiber point-diffraction interference detection method is due to using high-precision Mechanical Moving as phase-moving method, essence
Degree is still not high enough, at high cost, and it is big to develop difficulty.Especially to the measurement of heavy caliber face shape, precision machinery drives precision to reduce, measurement
Precision also decreases；In addition, using a part of a fiber exit light cone as measurement light, with another part as reference
The interference of light, therefore the cone angle very little of effectively light cone, so that measurable mirror surface range is by larger limitation.
It pushes tested mirror surface to carry out mechanical phase shift using piezoelectric ceramics in current pin hole point-diffraction interference detection method to measure,
But the mechanical phase shift of Piezoelectric Driving is not suitable for bigbore measured target mirror, the very big object of the difficult accurate driving quality of piezoelectric ceramics
Body；Meanwhile if the hot spot of tested mirror surface convergence is larger, the interference being easy by aperture edge diffraction is returned at aperture,
Change Wave-front phase distribution, reduces measurement accuracy；And small diffraction aperture complex manufacturing technology, it is at high cost.
Summary of the invention
The object of the present invention is to provide a kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers, it is noted that measurement essence
Degree reduces and develops difficulty and cost, and has preferable anti-interference.
The purpose of the present invention is what is be achieved through the following technical solutions：
A kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers, including：Laser, half-wave plate, polarization spectroscope, two
A acousto-optic frequency shifters, two fibre-coupled mirrors, two single-mode polarization maintaining fibers, double fiber stubs, measured lens, light splitting piece, imaging lens
Head and planar array detector；Wherein：
The laser of laser emitting injects polarization spectroscope after half-wave plate, and laser is divided into two bundles by polarization spectroscope；
Two beam laser are coupled in different single-mode polarization maintaining fibers after passing sequentially through different acousto-optic frequency shifters and fibre-coupled mirrors；
The exit end of two single-mode polarization maintaining fibers is inserted in double fiber stubs, and passes through double fiber stubs for two single modes
The laser vertical exit of polarization maintaining optical fibre output；Wherein beam of laser is as reference light directive spectroscope, and another beam of laser is as survey
Light emission is measured to measured lens；It measures and is overlapped interference with reference light through spectroscope after light is reflected by measured lens, then imaged camera lens is penetrated
Enter planar array detector.
Further, it is orthogonal by half-wave plate with polarization spectroscope to be divided into polarization direction for the laser of laser emitting
Two beam laser, the half-wave plate are used to adjust the splitting ratio of two beam laser.
Further, the shift frequency amount of two acousto-optic frequency shifters is different, is the low of several hertz or tens hertz magnitudes after difference frequency
Difference frequency.
Further, there are two the channel of connection lower end surface and upper surface, two single mode polarization-maintainings in double fiber stubs
Optical fiber is inserted into from the feeder connection of double fiber stub lower end surfaces respectively, until the channel exit of upper surface；Described two channels
Opposite upper face normal i at the same angle respectively, and the spacing of two channel outlets is less than predetermined value.
Further, further include：Monitor camera lens and supervision camera；
When the measurement light and reference light are through spectroscope, a part of light emission is to imaging lens, and another part light is by monitoring
Camera lens injects supervision camera.
As seen from the above technical solution provided by the invention, it using acousto-optic frequency shifters difference interference phase shift, effectively keeps away
Exempt from interferometer there are movement parts, measurement accuracy further increases, and anti-interference is good, and development difficulty can be reduced with cost；Especially
Its measurement for heavy caliber face shape, advantage same compared to Mechanical Driven become apparent from；Meanwhile using the side of double fiber stubs
Case increases the measurable mirror surface phase of optical fiber point-diffraction interferometer with two beam spot diffraction lights respectively as reference light and measurement light
To aperture.
Detailed description of the invention
In order to illustrate the technical solution of the embodiments of the present invention more clearly, required use in being described below to embodiment
Attached drawing be briefly described, it should be apparent that, drawings in the following description are only some embodiments of the invention, for this
For the those of ordinary skill in field, without creative efforts, it can also be obtained according to these attached drawings other
Attached drawing.
Fig. 1 is a kind of optical path signal of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers provided in an embodiment of the present invention
Figure；
Fig. 2 is the structural schematic diagram of double fiber stubs provided in an embodiment of the present invention；
Fig. 3 is the signal form schematic diagram of acquisition provided in an embodiment of the present invention.
Specific embodiment
With reference to the attached drawing in the embodiment of the present invention, technical solution in the embodiment of the present invention carries out clear, complete
Ground description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.Based on this
The embodiment of invention, every other implementation obtained by those of ordinary skill in the art without making creative efforts
Example, belongs to protection scope of the present invention.
The embodiment of the present invention provides a kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers, light channel structure such as Fig. 1
It is shown, mainly include：Laser, half-wave plate, polarization spectroscope, two acousto-optic frequency shifters, two fibre-coupled mirrors, two single modes
Polarization maintaining optical fibre, double fiber stubs, measured lens, light splitting piece, imaging lens and planar array detector；Wherein：
The laser of laser emitting injects polarization spectroscope after half-wave plate, and laser is divided into two bundles by polarization spectroscope；
Two beam laser are coupled in different single-mode polarization maintaining fibers after passing sequentially through different acousto-optic frequency shifters and fibre-coupled mirrors；Such as figure
In 1, beam of laser is coupled in single-mode polarization maintaining fiber 1 after acousto-optic frequency shifters 1 and fibre-coupled mirrors 1；Another beam of laser warp
It is coupled in single-mode polarization maintaining fiber 2 after crossing acousto-optic frequency shifters 2 and fibre-coupled mirrors 2；
The exit end of two single-mode polarization maintaining fibers is inserted in double fiber stubs, and passes through double fiber stubs for two single modes
The laser vertical exit of polarization maintaining optical fibre output；Wherein beam of laser is as reference light directive spectroscope, and another beam of laser is as survey
Light emission is measured to measured lens；It measures and is overlapped interference with reference light through spectroscope after light is reflected by measured lens, then imaged camera lens is penetrated
Enter planar array detector.
It will be understood by those skilled in the art that the reference light and measurement light are for the device of laser directive；
The laser that can be the outgoing of single-mode polarization maintaining fiber 1 as the spectroscopical laser of reference light directive, is also possible to single mode polarization-maintaining light
The laser of 2 outgoing of fibre；Similarly, it can be the laser that single-mode polarization maintaining fiber 1 is emitted to the laser of measured lens as measurement light emission,
It can be the laser of the outgoing of single-mode polarization maintaining fiber 2.
In the embodiment of the present invention, it is mutual that the laser of laser emitting by half-wave plate is divided into polarization direction with polarization spectroscope
Two vertical beam laser, the half-wave plate are used to adjust the splitting ratio of two beam laser.
In the embodiment of the present invention, the shift frequency amount of two acousto-optic frequency shifters is different, is several hertz or tens hertz amounts after difference frequency
The low difference frequency of grade.
As shown in Fig. 2, there are two the channel of connection lower end surface and upper surface, two single mode polarization-maintainings in double fiber stubs
Optical fiber is inserted into from the feeder connection of double fiber stub lower end surfaces respectively, until the channel exit of upper surface；Described two channels
Opposite upper face normal i at the same angle respectively, and the spacing of two channel outlets is less than predetermined value.In addition, upper surface into
Row high-precision grinding and polishing makes its surface have preferable surface roughness and reflectivity, technique and conventional fiber stub
End surface grinding is identical.According to the reflectivity of measured piece, the end face after polishing can plate semi-transparent semi-reflecting film.
The size of the angle i determines by the refractive index n of light splitting piece material therefor, in order to guarantee the beam direction of outgoing with
Spectroscope is at 45 °, then：
It will be understood by those skilled in the art that two beam laser of double fiber stub outgoing are in light splitting piece in normal two sides
45 ° of angles, the angle of this two beams laser are then 90 °.
On the other hand, double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers further include：Monitor camera lens and monitoring phase
Machine；When the measurement light and reference light are through spectroscope, a part of light emission is penetrated to imaging lens, another part light by monitoring camera lens
Enter supervision camera；Adjustment for auxiliary optical path and interference pattern.
In the embodiment of the present invention, by planar array detector obtain interference pattern after, can by solve interference pattern can be obtained to
Survey the face type of mirror.
Resolution principle is as follows：
If the frequency of two-beam is respectively ν after shift frequency1And ν2, frequency difference ν1-ν2For hertz or tens hertz of magnitudes, high speed phase
Machine uses hundreds of hertz of magnitudes, therefore can accurately detect the beat signal of heterodyne.If the light intensity of two-beam is all E, then face battle array
The interference signal S (t) of the variation of t at any time of some acquisition on detector is expressed as：
Wherein, L be measuring beam back and forth surface to be measured when relative to the reference light more light path walked, R is that measured lens surface is thick
Rough relief volume, c are the light velocity.A point on a little corresponding tested surface of planar array detector, one group of face battle array of camera continuous acquisition
The value of photo, as one group of data cube, corresponding identical every bit extracts as a cosine periodic signal, the as shape of S (t)
Formula, as shown in Figure 3.Difference is caused on planar array detector due to the R value difference of coarse fluctuating it can be seen from signal form
The signal phase of corresponding points detection is different.The phase for often pointing out signal can be resolved using Fourier analysis or other data processing methods
Position, combine denoised, phase unwrapping solution, face type restore etc. calculate after the relief volume on surface to be measured can be obtained.It is i.e. real
The measurement of full filed heterodyne opposite type is showed.
The above scheme of the embodiment of the present invention effectively avoids interference with instrument presence using acousto-optic frequency shifters difference interference phase shift
Movement parts, measurement accuracy further increase, and anti-interference is good, and development difficulty can be reduced with cost；Particularly with heavy caliber
The measurement of face shape, advantage same compared to Mechanical Driven become apparent from；Meanwhile using the scheme of double fiber stubs, with two beam spots
Diffraction light increases the measurable mirror surface relative aperture of optical fiber point-diffraction interferometer respectively as reference light and measurement light.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Within the technical scope of the present disclosure, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claims
Subject to enclosing.
Claims (4)
1. a kind of double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers, which is characterized in that including：Laser, half-wave plate, polarization
Spectroscope, two acousto-optic frequency shifters, two fibre-coupled mirrors, two single-mode polarization maintaining fibers, double fiber stubs, measured lens, light splitting
Piece, imaging lens and planar array detector；Wherein：
The laser of laser emitting injects polarization spectroscope after half-wave plate, and laser is divided into two bundles by polarization spectroscope；Two beams
Laser is coupled in different single-mode polarization maintaining fibers after passing sequentially through different acousto-optic frequency shifters and fibre-coupled mirrors；
The exit end of two single-mode polarization maintaining fibers is inserted in double fiber stubs, and passes through double fiber stubs for two single mode polarization-maintainings
The laser vertical exit of optical fiber output；Wherein beam of laser is as reference light directive spectroscope, and another beam of laser is as measurement light
Directive measured lens；It measures and is overlapped interference with reference light through spectroscope after light is reflected by measured lens, then imaged camera lens injects face
Array detector；
There are two the channel of connection lower end surface and upper surface in double fiber stubs, two single-mode polarization maintaining fibers are respectively from double light
The feeder connection of fine lock pin lower end surface is inserted into, until the channel exit of upper surface；Distinguish opposite upper face in described two channels
Normal i at the same angle, and the spacing of two channel outlets is less than predetermined value.
2. double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers according to claim 1, which is characterized in that
The laser of laser emitting is divided into the orthogonal two beams laser in polarization direction by half-wave plate and polarization spectroscope, described
Half-wave plate is used to adjust the splitting ratio of two beam laser.
3. double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers according to claim 1, which is characterized in that two acousto-optics
The shift frequency amount of frequency shifter is different, is the low difference frequency of several hertz or tens hertz magnitudes after difference frequency.
4. double optical fiber point-diffraction full filed low frequency heterodyne ineterferometers according to claim 1, which is characterized in that further include：
Monitor camera lens and supervision camera；
When the measurement light and reference light are through spectroscope, a part of light emission is to imaging lens, and another part light is by monitoring camera lens
Inject supervision camera.
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| 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 |
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| DE3175395D1 (en) * | 1981-02-20 | 1986-11-06 | Kaptron Inc | Fiber optics communications modules |
| CN1431477A (en) * | 2003-02-14 | 2003-07-23 | 中国科学院上海光学精密机械研究所 | Spot diffraction interferometer for measuring surface shape |
| CN102288105A (en) * | 2011-07-22 | 2011-12-21 | 大连民族学院 | Structure and detection method of optical fiber point-diffraction interferometer |
| CN203025420U (en) * | 2013-01-05 | 2013-06-26 | 山东建筑大学 | Optical fiber beam combiner |
| CN104296678B (en) * | 2014-09-29 | 2017-02-22 | 中国科学院光电研究院 | Heterodyne interferometer based on phase shift of low-frequency-difference acousto-optic frequency shifter |
| CN104296676B (en) * | 2014-09-29 | 2017-04-26 | 中国科学院光电研究院 | Heterodyne point diffraction interferometer based on phase shift of low-frequency-difference acousto-optic frequency shifter |
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