CN115112045B - Interferometry method based on all-fiber orthogonal polarization optical path matching short-coherence light source - Google Patents
Interferometry method based on all-fiber orthogonal polarization optical path matching short-coherence light source Download PDFInfo
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- 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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- 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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- G01B9/02012—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal intensity variation
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Abstract
The invention discloses an interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source, which uses a short-coherence laser, a first polarization maintaining optical fiber, an optical fiber polarization beam splitter, a second polarization maintaining optical fiber, an optical fiber adjustable attenuator, a third polarization maintaining optical fiber, a fourth polarization maintaining optical fiber, an optical fiber delay line, a fifth polarization maintaining optical fiber, an optical fiber polarization beam combiner and a sixth polarization maintaining optical fiber to form the all-fiber orthogonal polarization optical path matching short-coherence light source; aiming at the interference characteristic of the short coherent light, compensating the optical path difference between reference light and test light in the interferometer by using an optical fiber delay line to realize optical path matching; and an optical fiber adjustable attenuator is used for adjusting the light intensity difference between two orthogonal polarized lights to realize light intensity matching so as to obtain clear and stable interference fringes and complete the short coherence interferometry. Compared with the prior art, the method provided by the invention improves the integration level, the simplicity and the anti-interference capability of the device for the short coherence interferometry while guaranteeing the stability of interference fringes, and is more suitable for industrialization.
Description
Technical Field
The invention belongs to the technical field of optical interferometry, and particularly relates to an interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source.
Background
With the advancement of society and technology, optics have been widely used in scientific research and production and manufacture, and optical elements have become more abundant and diversified as carriers for optical technology realization. The diversification of optical elements requires not only high-end manufacturing capability but also high-precision detection capability as a reference standard. The precision of the optical interferometry technique can reach the nanometer level and has the non-contact characteristic, the optical interferometry technique is widely accepted and used in the field of optical detection, and the precise surface type information of the element can be efficiently obtained by processing and resolving interference fringe images.
The coherence length of the short coherence light source is short, the time coherence is poor, the incoherent optical path difference between two light waves generated by the short coherence light source is extremely small, interference fringes can be observed basically only near the zero optical path difference position, and the fringes are few, by utilizing the characteristic, the short coherence interferometry can overcome the defect of single-color light fringe order blurring, the vertical axis detection range of interference detection is greatly expanded, and the problems in some single-color light interferometry are solved, for example: and detecting a piston error between the sub-mirrors of the large spliced telescope.
In the short coherence interferometry, aiming at the distance between an element to be measured and a standard element, particularly a large-sized light source element with a cavity length which is difficult to change by moving a mirror to be measured, the optical path matching is carried out in a certain mode at the position of the light source, so that a more rapid and effective mode is realized; aiming at the problem of stripe contrast difference caused by unmatched light intensities of a reference beam and a measuring beam, an effective adjusting mechanism is added at the position of a light source to adjust the light intensity of a coherent light beam; compared with the existing free space scheme, the all-fiber light source structure has stronger anti-interference capability, more flexible structure and maneuverability, no optical alignment is needed, and the all-fiber light source structure can be used immediately after connection on the premise of not losing stability and precision, is simpler to build and operate and is more suitable for industrialization. The invention provides an interference measurement method based on an all-fiber orthogonal polarization optical path matching short-coherence light source, which can be adapted to interferometers with different structures to finish short-coherence interference measurement, and adopts an optical fiber delay line and an optical fiber adjustable attenuator to respectively solve two key problems of optical path matching and light intensity matching in short-coherence interference.
Disclosure of Invention
The invention aims to provide an interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source, which has the advantages of high device integration, simple operation and strong anti-interference capability and is more suitable for industrialization.
The technical solution for realizing the purpose of the invention is as follows: an interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source comprises the following steps:
and step 1, connecting an all-fiber orthogonal polarization optical path matching short-coherence light source with an interferometer.
The all-fiber orthogonal polarization optical path matching short coherent light source comprises a short coherent laser, a first polarization maintaining optical fiber, an optical fiber polarization beam splitter, a second polarization maintaining optical fiber, an optical fiber adjustable attenuator, a third polarization maintaining optical fiber, a fourth polarization maintaining optical fiber, an optical fiber delay line, a fifth polarization maintaining optical fiber, an optical fiber polarization beam combiner and a sixth polarization maintaining optical fiber.
And 2, placing the measured piece in a test light path of the interferometer, and controlling the length of an interference cavity to be a free space equivalent light path of the length difference value of an S light path and a P light path in the all-fiber orthogonal polarization light path matched short-coherence light source.
And 3, turning on a short coherent laser, adjusting the optical path difference between the orthogonal polarized light beams through an optical fiber delay line, observing the contrast change of the gray level image received by the polarization camera of the interferometer, and further adjusting the position near the optimal optical path matching position when the interference fringes occur when the mutation occurs, wherein the optimal contrast is the optimal optical path matching position, namely the zero optical path position when the interference fringes are the clearest.
And 4, adjusting the light intensity difference between the orthogonal polarized light beams through the optical fiber adjustable attenuator until the interference fringe contrast is optimal.
And 5, acquiring a short-coherence interference fringe pattern by using an interferometer polarization camera, and resolving by using a four-step phase shifting algorithm.
Compared with the prior art, the invention has the remarkable advantages that:
(1) The light source device is of a highly integrated all-fiber structure, is combined with a dynamic interferometer, can resist environmental vibration and airflow interference, has low requirements on environment, has more flexible structure and maneuverability, is installed without tedious optical alignment, can realize instant use on the premise of not losing stability and precision, and is more suitable for industrialization compared with a free space scheme;
(2) The light source device can generate a pair of short coherent orthogonal linearly polarized light with adjustable optical path difference and matched light intensity, and clear interference fringes can be obtained without moving a measured piece to change the cavity length of the interferometer;
(3) The short coherent light source is adopted, so that the influence of stray stripes in the system on a measurement result can be avoided;
(4) The optical path difference is regulated and controlled by adopting an optical fiber delay line which is widely used and verified in the communication industry, so that the scheme has strong reliability;
(5) The testing process is simple and the adjustment is convenient.
Drawings
FIG. 1 is a flow chart of an interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source.
Fig. 2 is a schematic structural diagram of an all-fiber orthogonal polarization optical path matching short-coherence light source according to the present invention.
Fig. 3 is a schematic diagram of the optical path delay principle of the optical fiber delay line.
FIG. 4 is a schematic diagram showing the formation of interference wave packets during scanning of different height profiles of the surface of the object under test.
Fig. 5 is a schematic diagram of an optical fiber adjustable attenuator.
FIG. 6 is a schematic diagram of the optical path structure of the present invention applied to a Talman-Green dynamic interferometer.
Fig. 7 is a schematic diagram of an optical path structure of the present invention applied to a fizeau-type dynamic interferometer.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1 and 2, an interferometry method based on all-fiber orthogonal polarization optical path matching short-coherence light source includes the following steps:
and step 1, connecting an all-fiber orthogonal polarization optical path matching short-coherence light source with an interferometer 8 through an optical fiber connector 7.
The all-fiber orthogonal polarization optical path matching short coherent light source comprises: the optical fiber polarization beam splitter comprises a short coherent laser 1, a first polarization maintaining optical fiber 2-1, an optical fiber polarization beam splitter 3, a second polarization maintaining optical fiber 2-2, an optical fiber adjustable attenuator 4, a third polarization maintaining optical fiber 2-3, a fourth polarization maintaining optical fiber 2-4, an optical fiber delay line 5, a fifth polarization maintaining optical fiber 2-5, an optical fiber polarization beam combiner 6 and a sixth polarization maintaining optical fiber 2-6.
Further, the short coherent laser 1 is connected with the optical fiber polarization beam splitter 3 through the first polarization maintaining optical fiber 2-1, and the optical path is divided into two paths by the optical fiber polarization beam splitter 3, namely a P light path and an S light path; the P light path is sequentially provided with a second polarization maintaining optical fiber 2-2, an optical fiber adjustable attenuator 4 and a third polarization maintaining optical fiber 2-3; the S-light path is sequentially provided with a fourth polarization maintaining optical fiber 2-4, an optical fiber delay line 5 and a fifth polarization maintaining optical fiber 2-5; the optical fiber polarization beam combiner 6 combines the optical paths into one path again, and is connected with the optical fiber connector 7 through the sixth polarization maintaining optical fiber 2-6.
Further, the method comprises the steps of. The output light of the short coherent laser 1 is wide-spectrum linear polarized laser, and the laser frequency and the power stability meet the stability requirements of interference measurement stripes.
And 2, placing the measured piece 9 in a test light path of the interferometer 8, and controlling the length of an interference cavity to be a free space equivalent light path of the length difference value of an S light path and a P light path in the all-fiber orthogonal polarization light path matching short-coherence light source.
Step 3, turning on the short coherent laser 1, at this time, the broad spectrum linear polarized light output by the short coherent laser 1 is delayed by a first polarization maintaining optical fiber 2-1, the slow axis direction of the first polarization maintaining optical fiber 2-1 is aligned with the light splitting direction of the optical fiber polarization beam splitter 3 by 45 degrees, so that the broad spectrum linear polarized light output by the short coherent laser 1 is divided into two beams of linear polarized light with orthogonal polarization directions according to the light intensity ratio of 1:1, namely P light vibrating along the paper surface and S light vibrating perpendicular to the paper surface, and the two beams of linear polarized light are output by a first output port (port 1), namely a P light output port and a second output port (port 2), namely an S light output port, and are propagated along a P light path and an S light path; in the P-ray path, the P-ray is input to the optical fiber adjustable attenuator 4 along the second polarization maintaining optical fiber 2-2, and then is input to the second input port (port 1) of the optical fiber polarization beam combiner 6 through the third polarization maintaining optical fiber 2-3, namely the P-ray input port, so that the slow axis direction of the third polarization maintaining optical fiber 2-3 is the same as that of the second polarization maintaining optical fiber 2-2, and the P-ray polarization state is ensured not to change. In the S light path, the S light is input to an optical fiber delay line 5 by an S light delay fourth polarization maintaining optical fiber 2-4, and then the S light is input to a third input port (port 2) of an optical fiber polarization beam combiner 6, namely an S light input port, by the fifth polarization maintaining optical fiber 2-5, and is combined with P light, and the slow axis direction of the fifth polarization maintaining optical fiber 2-5 is the same as that of the fourth polarization maintaining optical fiber 2-4 so as to ensure that the polarization state of the S light is not changed; in the optical fiber polarization beam combiner 6, two beams of light finally form a pair of orthogonal linear polarized light with a certain optical path difference, and the pair of orthogonal linear polarized light enters the sixth polarization maintaining optical fiber 2-6 through the third output port (port 3) and is transmitted to the optical fiber connector 7, and is output to the measuring light path of the interferometer 8 through the optical fiber connector 7. The slow axis direction of the sixth polarization maintaining optical fiber 2-6 is the same as the slow axis direction of the third polarization maintaining optical fiber 2-3, and the fast axis direction of the sixth polarization maintaining optical fiber is the same as the slow axis direction of the fifth polarization maintaining optical fiber 2-5, so that the P light and the S light respectively transmit along the slow axis and the fast axis of the P light and the S light.
Referring to fig. 3, the optical fiber delay line 5 includes an optical fiber coupling input port 10, an optical fiber coupling output port 11, a corner cube 12, a screw 13, and an adjusting nut 14.S light is transmitted to an optical fiber coupling input port 10 by a fourth polarization maintaining optical fiber 2-4, then is transmitted to a pyramid prism 12 in a free space in a collimated beam form, is reflected back to the free space in parallel due to the parallel nature of incident light and emergent light of the pyramid prism 12, generates a certain radial offset, is finally received by an optical fiber coupling output port 11 which is spaced from the optical fiber coupling input port 11 by an amount equal to the radial offset of the incident and reflected light beams of the pyramid prism 12, and is output by a fifth polarization maintaining optical fiber 2-5; the adjusting nut 14 is rotated to drive the screw 13 to translate the pyramid prism 12 so as to adjust the S-light optical path delay.
With reference to fig. 4, the optical fiber delay line 5 is adjusted to scan the surface height profile of the measured piece 9, interference wave packets are formed by contours of different heights on the surface of the measured piece 9 in the scanning process, the pixel points on different horizontal positions on the polarization camera of the interferometer 8 can obtain the brightness change of the corresponding interference wave packets in the adjusting process, the contrast change of gray images received by the polarization camera of the interferometer 8 is observed, when the interference fringes occur suddenly, the position is near the optimal position of optical path matching, further adjustment is performed, when the interference fringes are the clearest, and the contrast is the optimal position of optical path matching, namely the peak position of the interference wave packets.
Furthermore, the adjustment precision of the optical fiber delay line 5 is far smaller than the coherence length of the wide-spectrum linear polarization laser output by the short coherence laser 1, and the adjustment range is far larger than the maximum value of the surface topography height difference of the measured piece 9.
And 4, adjusting the light intensity difference between the orthogonal polarized light beams through the optical fiber adjustable attenuator 4 until the interference fringe contrast is optimal.
Referring to fig. 5, the optical fiber adjustable attenuator 4 is composed of an input optical fiber 2-2, a collimating lens 15, a focusing lens 16, a blocking device 17 and an output optical fiber 2-3; the input optical fiber 2-2 and the output optical fiber 2-3 are the second polarization maintaining optical fiber 2-2 and the third polarization maintaining optical fiber 2-3. The collimating lens 15 expands the P-light from the fiber space into free space, rotates the adjusting screw, moves the blocking device 17 into the beam path, blocks part of the free space beam, and then the focusing lens 16 couples light into the output fiber 2-3 to manually change the coupling efficiency until the desired attenuation, i.e. the interference fringe contrast, is optimal, at which time the P-light passing through the fiber adjustable attenuator 4 matches the intensity of the S-light passing through the fiber delay line 5.
And 5, acquiring a short-coherence interference fringe pattern by using an interferometer 8 polarization camera, and resolving by using a four-step phase shifting algorithm.
Example 1
Referring to FIG. 6, a schematic diagram of the optical path structure of the Tasmann-based dynamic interferometer 8-1 is shown, which is an interferometric method based on an all-fiber orthogonal polarization optical path matching short-coherence light source.
And step 1, connecting an all-fiber orthogonal polarization optical path matching short-coherence light source with the Tasman-Grignard dynamic interferometer 8-1 through an optical fiber connector 7.
And 2, placing the measured piece 9 in a detection light path, and controlling the distance between the measured piece 9 and the polarizing beam splitter 19 and the distance between the standard piece 21 and the polarizing beam splitter 19 to be the free space equivalent value of the distance difference between the S light path and the P light path in the all-fiber orthogonal polarizing light path matching short-coherence light source.
Step 3, turning on the short coherent laser 1, wherein the all-fiber orthogonal polarized light is matched with a pair of orthogonal linear polarized lights with a certain optical path difference and with a matched light intensity, which are output by a short coherent light source, are subjected to beam expansion and collimation by a beam expander 18 and then are subjected to beam splitting by a polarization beam splitter 19, wherein the S light with a longer optical path is used as a reference light beam to be reflected to a standard component 21 by the polarization beam splitter 19 and then reflected back to the polarization beam splitter 19, and the polarization direction is rotated by 90 degrees to become P light after passing through a first lambda/4 wave plate 20-1 back and forth in the process, and the P light is incident to an imaging light path through the polarization beam splitter 19; the P light with a shorter optical path is taken as a test light beam to be transmitted through the polarization beam splitter 19 and is incident to the tested piece 9, then reflected back to the polarization beam splitter 19, and similarly, the P light is changed into S light after passing through the second lambda/4 wave plate 20-2 twice in the process, and is reflected to an imaging light path by the polarization beam splitter 19; in the imaging light path, the orthogonal polarized light beam carrying the surface morphology information of the measured piece 9 is changed into circular polarized light with opposite rotation directions through the third lambda/4 wave plate 20-3, and then the polarization camera 22 performs polarization phase shift to form an interference pattern with 4 pairs of equal phase difference intervals.
The optical fiber delay line 5 is used for adjusting the optical path difference between the S light and the P light in the all-fiber orthogonal polarization optical path matching short-coherence light source, and when the optical path difference of the two light beams is equal to the length of the interference cavity, namely, the position of zero optical path difference, the polarization camera 22 receives interference fringes.
And 4, adjusting the optical fiber adjustable attenuator 4, and performing light intensity matching on the two coherent light beams to improve the fringe contrast ratio, so as to finally obtain clear short coherent interference fringes with optimal contrast ratio.
And 5, recording positions of corresponding interference fringe peak value optical path differences generated at different points on the surface to be measured, and resolving a phase-shifting interference pattern generated by the polarization camera 22 through a four-step phase-shifting algorithm to obtain the surface height morphology of the measured piece 9.
Example 2
Referring to fig. 7, the interferometry method based on the all-fiber orthogonal polarization optical path matching short-coherence light source is applied to the optical path structure schematic diagram of the fizeau dynamic interferometer 8-2.
And step 1, connecting an all-fiber orthogonal polarization optical path matching short-coherence light source with a Fizeau type dynamic interferometer 8-2 through an optical fiber connector 7.
And 2, placing the measured piece 9 in a detection light path, and controlling the distance between the measured piece 9 and the standard piece 26, namely the interference cavity length to be a free space equivalent value of the difference value between the lengths of the S light path and the P light path in the all-fiber orthogonal polarization optical path matching short-coherence light source.
And 3, turning on the short coherent laser 1, wherein all-fiber orthogonal polarized light is matched with a pair of orthogonal linear polarized lights with matched light intensity with a certain optical path difference, which are output by a short coherent light source, are transmitted by a beam splitting prism 24 in a half way after being expanded by a negative lens 23, and are reflected in a half way, wherein the transmitted lights are collimated by a collimating lens 25, are respectively reflected back to one beam of light by the rear surface of a standard component 26 and the front surface of a measured component 9, and are transmitted in a half way again after being transmitted by the beam splitting prism 24, and are reflected in a half way, wherein the reflected lights are imaged on the target surface of a polarization camera 29 after passing through an imaging lens 27 and a lambda/4 wave plate 28, the optical path difference between S light and P light is changed by a regulating optical fiber delay line 5, and when the S light reflected back by the rear surface of the standard component 26 and the P light reflected back by the front surface of the measured component 9 meet the condition of zero optical path difference, the polarization camera 29 receives interference fringes.
And 4, adjusting the optical fiber adjustable attenuator 4 to enable the light intensity of the S light and the light intensity of the P light to be matched, and enabling the interference fringe contrast to be optimal.
And 5, recording positions of corresponding interference fringe peak value optical path differences generated at different points on the surface to be measured, and resolving a phase-shifting interference pattern generated by the polarization camera 29 through a four-step phase-shifting algorithm to obtain the surface height morphology of the measured piece 9.
In summary, the invention can be applied to interferometers with different structures, clear short coherence interferometry can be obtained without changing the cavity length of the interferometer, the stability of the interference fringe is ensured, and meanwhile, the integration level, the simplicity and the anti-interference capability of the device for short coherence interferometry are improved, so that the invention is more suitable for industrialization.
Claims (7)
1. An interferometry method based on an all-fiber orthogonal polarization optical path matching short-coherence light source is characterized by comprising the following steps:
step 1, connecting an all-fiber orthogonal polarization optical path matching short-coherence light source with an interferometer (8) through an optical fiber connector (7);
the all-fiber orthogonal polarization optical path matching short coherent light source comprises a short coherent laser (1), a first polarization maintaining optical fiber (2-1), an optical fiber polarization beam splitter (3), a second polarization maintaining optical fiber (2-2), an optical fiber adjustable attenuator (4), a third polarization maintaining optical fiber (2-3), a fourth polarization maintaining optical fiber (2-4), an optical fiber delay line (5), a fifth polarization maintaining optical fiber (2-5), an optical fiber polarization beam combiner (6) and a sixth polarization maintaining optical fiber (2-6);
step 2, placing a tested piece (9) in a test light path of an interferometer (8), and controlling the length of an interference cavity to be a free space equivalent light path of an all-fiber orthogonal polarization light path matching S light path and P light path length difference value in a short coherent light source;
step 3, turning on a short coherent laser (1), adjusting the optical path difference between the orthogonal polarized light beams through an optical fiber delay line (5), observing the contrast change of a gray image received by a polarization camera of an interferometer (8), and when mutation occurs, the interference fringes are near the optical path matching optimal position, further adjusting, and when the interference fringes are the clearest, the contrast is the optical path matching optimal position, namely the zero optical path position;
step 4, adjusting the light intensity difference between the orthogonal polarized light beams through an optical fiber adjustable attenuator (4) until the interference fringe contrast is optimal;
and 5, acquiring a short coherence interference fringe pattern by using an interferometer (8) polarization camera, and resolving by using a four-step phase shifting algorithm.
2. The interferometry method based on an all-fiber orthogonal polarization optical path matching short coherence light source of claim 1, wherein the interferometry method comprises the steps of: in the all-fiber orthogonal polarization optical path matching short-coherence light source, a short-coherence laser (1) is connected with an optical fiber polarization beam splitter (3) through a first polarization maintaining optical fiber (2-1), and the optical path is divided into two paths by the optical fiber polarization beam splitter (3), namely a P-light path and an S-light path; a second polarization maintaining optical fiber (2-2), an optical fiber adjustable attenuator (4) and a third polarization maintaining optical fiber (2-3) are sequentially arranged along a P light path; a fourth polarization maintaining optical fiber (2-4), an optical fiber delay line (5) and a fifth polarization maintaining optical fiber (2-5) are sequentially arranged along an S-light path; the output ends of the third polarization maintaining optical fiber (2-3) and the fifth polarization maintaining optical fiber (2-5) are connected with an optical fiber polarization beam combiner (6), and the optical fiber polarization beam combiner (6) combines the two light paths into one path again and is connected with an optical fiber connector (7) through the sixth polarization maintaining optical fiber (2-6);
the output light of the short coherent laser (1) enters an optical fiber polarization beam splitter (3) through a first polarization maintaining optical fiber (2-1), and the optical fiber polarization beam splitter (3) divides a light beam into two short coherent orthogonal linearly polarized lights, namely S light and P light; the P light is input into an optical fiber adjustable attenuator (4) through a second polarization-maintaining light beam (2-2), and then is input into an optical fiber polarization beam combiner (6) through a third polarization-maintaining light beam (2-3) after attenuation adjustment; s light is input into an optical fiber delay line (5) through a fourth polarization maintaining optical fiber (2-4), and is input into an optical fiber polarization beam combiner (6) through a fifth polarization maintaining optical fiber (2-5) after the optical path is adjusted through the optical fiber delay line (5); the processed P light and S light are combined by an optical fiber polarization beam combiner (6) to form short coherent orthogonal polarized light with adjustable optical path difference, and the short coherent orthogonal polarized light is connected with an optical fiber connector (7) through a sixth polarization maintaining fiber (2-6) to output a pair of linear polarized light with adjustable optical path difference and orthogonal polarization direction.
3. The interferometry method based on the all-fiber orthogonal polarization optical path matching short-coherence light source according to claim 2, wherein the interferometry method is characterized by: the output light of the short coherent laser (1) is wide-spectrum linear polarized laser, and the laser frequency and the power stability meet the stability requirements of interference measurement stripes.
4. An interferometry method based on an all-fiber orthogonal polarization optical path matching short coherence light source according to claim 3, wherein: the optical fiber polarization beam splitter (3) comprises a first input port, a first output port and a second output port, wherein the first output port is a P light output port, and the second output port is an S light output port; the first polarization maintaining optical fiber (2-1) is connected with the first input port, and the slow axis direction of the first polarization maintaining optical fiber is aligned with the light splitting direction of the optical fiber polarization beam splitter (3) at 45 degrees; the second polarization maintaining optical fiber (2-2) is connected with the first output port, and the slow axis direction of the second polarization maintaining optical fiber is parallel to the polarization direction of the P light; the fourth polarization maintaining optical fiber (2-4) is connected with the second output port, and the slow axis direction of the fourth polarization maintaining optical fiber is parallel to the polarization direction of S light.
5. The interferometry method based on the all-fiber orthogonal polarization optical path matching short-coherence light source according to claim 4, wherein the interferometry method comprises the following steps: the optical path delay of the optical fiber delay line (5) is adjusted by rotating the nut, the adjusting range is far larger than the vertical axis measuring range required by detecting the surface morphology of the measured piece 9, and the adjusting precision is far smaller than the coherence length of the wide-spectrum linear polarization laser output by the short coherence laser (1).
6. The interferometry method based on the all-fiber orthogonal polarization optical path matching short-coherence light source according to claim 5, wherein the interferometry method is characterized by: the optical fiber polarization beam combiner (6) comprises a second input port, a third input port and a third output port, wherein the second input port is a P light input port, and the third input port is an S light input port; the third polarization maintaining optical fiber (2-3) is connected with the second input port, and the slow axis direction of the third polarization maintaining optical fiber is the same as that of the second polarization maintaining optical fiber (2-2); the fifth polarization maintaining optical fiber (2-5) is connected with the third input port, and the slow axis direction of the fifth polarization maintaining optical fiber is the same as that of the fourth polarization maintaining optical fiber (2-4); the sixth polarization maintaining fiber (2-6) is connected with the third output port, and the slow axis direction of the sixth polarization maintaining fiber is the same as that of the third polarization maintaining fiber (2-3).
7. The interferometry method based on the all-fiber orthogonal polarization optical path matching short-coherence light source according to claim 1, wherein the interferometry method is characterized by: the interferometer (8) adopts a Thaman-Greennel type or Fizeau type dynamic interferometer.
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