CN105698702A - Diplopore heterodyne ineterferometer based on acousto-optic low-frequency difference phase shift - Google Patents
Diplopore heterodyne ineterferometer based on acousto-optic low-frequency difference phase shift Download PDFInfo
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- CN105698702A CN105698702A CN201610236674.0A CN201610236674A CN105698702A CN 105698702 A CN105698702 A CN 105698702A CN 201610236674 A CN201610236674 A CN 201610236674A CN 105698702 A CN105698702 A CN 105698702A
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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
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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Abstract
The invention discloses a diplopore heterodyne ineterferometer based on acousto-optic low-frequency difference phase shift. The diplopore heterodyne ineterferometer employs acousto-optic frequency shifter heterodyne interference phase shift, a detector continuously acquires an interferogram of a same optical path, and no aligning of multiple interferograms is required. The measuring precision is further improved. Low frequency difference heterodyne interference and high speed camera continuous acquisition are employed to obtain more abundant information, thereby facilitating accurate phase calculation and noises suppression.
Description
Technical field
The present invention relates to optical technical field, particularly relate to a kind of diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift。
Background technology
The advanced optical equipment being representative with deep-UV lithography machine projection exposure system therefor, proposes great challenge to the processing of optical element, the integrated of optical system。Interferometer is as the integrated indispensable core detection equipment of high-precision optical element processing and optical system, and accuracy of detection requires to improve constantly。
The surface characterization test method adopted in traditional optical processing includes Hartmann sensor method, knife-edge method and consistency profiles etc.。These methods are respectively present non-digitalization and need the subjective different shortcoming such as interpretation or contact damage part to be measured, and are extremely difficult to higher certainty of measurement, are simple method for measuring。
Detection method is interfered just to be used before a century, belong to non-contact measurement, and there is the features such as wide range, high sensitivity, high accuracy, it is widely used when high precision test, its principle is that light beam irradiates the reference plane of standard as reference light, another bundle light irradiates tested surface and returns with face shape information as measuring light, owing to hot spot diverse location phase place difference produces optical path difference thus producing the interference fringe of bending when two-beam is interfered, namely can determine whether that the face shape of tested surface rises and falls。
Current interferometer adopts polarization phase shift system mostly, and two restraint mutually perpendicular light through its phase shift block, it is achieved four steps or multistep phase shift simultaneously, solves the face type of measured piece。But, though polarization phase-moving method meeting antivibration, several phase shifts figure simultaneously shot wants registration solution phase place, will certainly bring matching error；Additionally, gather the interferogram that can only obtain Finite Amplitude, the precision of its phase extraction is restricted, and the phase shifting accuracy of a few amplitude shift phasor is subject to the restriction of phase shift block, directly influences face type inversion accuracy。
Summary of the invention
It is an object of the invention to provide a kind of diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift, can greatly improve certainty of measurement。
It is an object of the invention to be achieved through the following technical solutions:
A kind of diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift, including: laser instrument, two blocks of half-wave plates, polarization spectroscope PBS, two acousto-optic frequency shifters, two fiber couplers, two polarization maintaining optical fibres, two spectroscopes, collimating mirror, standard mirror, mirror to be measured, filtering hole, two imaging lens and two detectors；Wherein:
Laser emitting laser injects PBS after half-wave plate 1, PBS incident laser is divided into two bundle laser；Wherein beam of laser is coupled into polarization maintaining optical fibre 1 by fiber coupler 1 after acousto-optic frequency shifters 1；Another beam of laser is coupled into polarization maintaining optical fibre 2 by fiber coupler 2 after sequentially passing through half-wave plate 2 and acousto-optic frequency shifters 2；
By adjusting the inclination of standard mirror and mirror to be measured, the laser of polarization maintaining optical fibre 2 outgoing is made to inject mirror to be measured after passing sequentially through light splitting 1, collimating mirror and standard mirror, backtracking after mirror to be measured reflects, and the mirror 1 that is split reflexes to and filters hole；The laser making polarization maintaining optical fibre 1 outgoing injects standard mirror each through after passing sequentially through light splitting 1 and collimating mirror, backtracking after standard mirror reflects, and the mirror 1 that is split reflexes to filtering hole；
The two bundle laser injecting filtering hole are divided into two-way after spectroscope 2；Wherein a road monitors light path as adjusting, and injects in detector 1 through imaging lens 1；Another road is injected in detector 2 through imaging lens 2 as gathering interferogram light path。
Further, incident laser is divided into two bundle laser according to any power ratio by described PBS。
Further, described half-wave plate 2 is for changing the polarization direction of laser so that two bundles laser polarization direction after acousto-optic frequency shifters is consistent。
Further, the shift frequency amount of two acousto-optic frequency shifters is different, is the low difference frequency of several hertz or tens hertz magnitudes after difference frequency。
Further, described polarization maintaining optical fibre 1 is fixed by stuck-module with the end of polarization maintaining optical fibre 2, it is ensured that the exit direction of two bundle laser is consistent, and horizontal space has certain dislocation。
As seen from the above technical solution provided by the invention, adopting acousto-optic frequency shifters difference interference phase shift, the same light path interferogram of detector continuous acquisition, the problem being absent from multi-frame interferometry pattern registration, certainty of measurement improves further；Additionally, adopt low frequency differences difference interference and high speed camera continuous acquisition, it is thus achieved that quantity of information more rich, be more beneficial for accurately resolving phase place, be more beneficial for overcoming the factor impacts such as noise。
Accompanying drawing explanation
In order to be illustrated more clearly that the technical scheme of the embodiment of the present invention, below the accompanying drawing used required during embodiment is described is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the premise not paying creative work, it is also possible to obtain other accompanying drawings according to these accompanying drawings。
The light path schematic diagram of a kind of diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift that Fig. 1 provides for the embodiment of the present invention；
The signal form schematic diagram of the collection that Fig. 2 provides for the embodiment of the present invention。
Detailed description of the invention
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments。Based on embodiments of the invention, the every other embodiment that those of ordinary skill in the art obtain under not making creative work premise, broadly fall into protection scope of the present invention。
The embodiment of the present invention provides a kind of diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift, its light channel structure is as it is shown in figure 1, specifically include that laser instrument, two blocks of half-wave plates, polarization spectroscope PBS, two acousto-optic frequency shifters, two fiber couplers, two polarization maintaining optical fibres, two spectroscopes, collimating mirror, standard mirror, mirror to be measured, filtering hole, two imaging lens and two detectors；Wherein:
Laser emitting laser injects PBS after half-wave plate 1, PBS incident laser is divided into two bundle laser；Wherein beam of laser is coupled into polarization maintaining optical fibre 1 by fiber coupler 1 after acousto-optic frequency shifters 1；Another beam of laser is coupled into polarization maintaining optical fibre 2 by fiber coupler 2 after sequentially passing through half-wave plate 2 and acousto-optic frequency shifters 2；
By adjusting the inclination of standard mirror and mirror to be measured, the laser of polarization maintaining optical fibre 2 outgoing is made to inject mirror to be measured after passing sequentially through light splitting 1, collimating mirror and standard mirror, backtracking after mirror to be measured reflects, and the mirror 1 that is split reflexes to and filters hole；The laser making polarization maintaining optical fibre 1 outgoing injects standard mirror each through after passing sequentially through light splitting 1 and collimating mirror, backtracking after standard mirror reflects, and the mirror 1 that is split reflexes to filtering hole；
The two bundle laser injecting filtering hole are divided into two-way after spectroscope 2；Wherein a road monitors light path as adjusting, and injects in detector 1 through imaging lens 1；Another road is injected in detector 2 through imaging lens 2 as gathering interferogram light path。
In the embodiment of the present invention, incident laser is divided into two bundle laser according to any power ratio by described PBS。
In the embodiment of the present invention, described half-wave plate 2 is for changing the polarization direction of laser so that two bundles laser polarization direction after acousto-optic frequency shifters is consistent。
In the embodiment of the present invention, the shift frequency amount of two acousto-optic frequency shifters is different, is the low difference frequency of several hertz or tens hertz magnitudes after difference frequency。
In the embodiment of the present invention, the end of described polarization maintaining optical fibre 1 and polarization maintaining optical fibre 2 is fixed by stuck-module, it is ensured that the exit direction of two bundle laser is consistent, and horizontal space has certain dislocation。
In the embodiment of the present invention, gathering two bundle laser in interferogram light path through fiber exit, corrugated is it is believed that desirable corrugated, and the face type of respective carrier standard mirror and mirror to be measured is interfered, and can obtain the face type of mirror to be measured by solving interferogram。
Resolution principle is as follows:
If the frequency of two-beam respectively ν after shift frequency1And ν2, frequency difference ν1-ν2For hertz or tens hertz of magnitudes, high speed camera adopts 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 interference signal S (t) of the upper change of t in time a bit gathered of high speed camera (detector) is expressed as:
Wherein, L is the light path that the laser of polarization maintaining optical fibre 2 outgoing is walked relative to the laser of polarization maintaining optical fibre 1 outgoing when coming and going mirror surface to be measured more, and R is the shaggy relief volume of mirror to be measured, and c is the light velocity。A point on a bit corresponding tested surface of high speed camera, one group of face battle array photo of camera continuous acquisition, it is one group of data cube, it is a cosine periodic signal that the value of corresponding identical every bit extracts, and is the form of S (t), as shown in Figure 2。By signal form it can be seen that difference is different due to the R value of coarse fluctuating, cause the signal phase of corresponding point detection on camera different。Utilizing Fourier analysis or other data processing method can resolve the phase place often pointing out signal, can obtain the relief volume on mirror surface to be measured, the Fourier analysis for different frequency can obtain different interference information respectively。The difference calculating the R value of every consecutive points respectively just can restore the face shape of mirror to be measured。
In the such scheme of the embodiment of the present invention, adopting acousto-optic frequency shifters difference interference phase shift, the same light path interferogram of detector continuous acquisition, the problem being absent from multi-frame interferometry pattern registration, certainty of measurement improves further；Additionally, adopt low frequency differences difference interference and high speed camera continuous acquisition, it is thus achieved that quantity of information more rich, be more beneficial for accurately resolving phase place, be more beneficial for overcoming the factor impacts such as noise。
The above; being only the present invention preferably detailed description of the invention, but protection scope of the present invention is not limited thereto, any those familiar with the art is in the technical scope of present disclosure; the change that can readily occur in or replacement, all should be encompassed within protection scope of the present invention。Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims。
Claims (5)
1. the diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift, it is characterized in that, including: laser instrument, two blocks of half-wave plates, polarization spectroscope PBS, two acousto-optic frequency shifters, two fiber couplers, two polarization maintaining optical fibres, two spectroscopes, collimating mirror, standard mirror, mirror to be measured, filtering hole, two imaging lens and two detectors；Wherein:
Laser emitting laser injects PBS after half-wave plate 1, PBS incident laser is divided into two bundle laser；Wherein beam of laser is coupled into polarization maintaining optical fibre 1 by fiber coupler 1 after acousto-optic frequency shifters 1；Another beam of laser is coupled into polarization maintaining optical fibre 2 by fiber coupler 2 after sequentially passing through half-wave plate 2 and acousto-optic frequency shifters 2；
By adjusting the inclination of standard mirror and mirror to be measured, the laser of polarization maintaining optical fibre 2 outgoing is made to inject mirror to be measured after passing sequentially through light splitting 1, collimating mirror and standard mirror, backtracking after mirror to be measured reflects, and the mirror 1 that is split reflexes to and filters hole；The laser making polarization maintaining optical fibre 1 outgoing injects standard mirror each through after passing sequentially through light splitting 1 and collimating mirror, backtracking after standard mirror reflects, and the mirror 1 that is split reflexes to filtering hole；
The two bundle laser injecting filtering hole are divided into two-way after spectroscope 2；Wherein a road monitors light path as adjusting, and injects in detector 1 through imaging lens 1；Another road is injected in detector 2 through imaging lens 2 as gathering interferogram light path。
2. the diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift according to claim 1, it is characterised in that incident laser is divided into two bundle laser according to any power ratio by described PBS。
3. the diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift according to claim 1, it is characterised in that described half-wave plate 2 is for changing the polarization direction of laser so that two bundles laser polarization direction after acousto-optic frequency shifters is consistent。
4. the diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift according to claim 1, it is characterised in that the shift frequency amount of two acousto-optic frequency shifters is different, is the low difference frequency of several hertz or tens hertz magnitudes after difference frequency。
5. the diplopore heterodyne ineterferometer based on acousto-optic low frequency differences phase shift according to claim 1, it is characterized in that, the end of described polarization maintaining optical fibre 1 and polarization maintaining optical fibre 2 is fixed by stuck-module, it is ensured that the exit direction of two bundle laser is consistent, and horizontal space has certain dislocation。
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| CN109375379A (en) * | 2018-11-26 | 2019-02-22 | 北京科技大学 | A kind of laser interferencefringes transmitter |
| CN112255640A (en) * | 2020-09-11 | 2021-01-22 | 北京空间机电研究所 | Variable frequency difference laser interference distance measuring device capable of adaptively adjusting optical path |
| CN112484648A (en) * | 2020-11-18 | 2021-03-12 | 北京华卓精科科技股份有限公司 | Displacement measurement system and method for heterodyne optical fiber interferometer |
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