CN109856943B - Phase shift interference fringe generation system and generation method thereof - Google Patents
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Abstract
The invention provides a phase shift interference fringe generating system and a generating method thereof, wherein the generating system comprises a light source capable of emitting linearly polarized light, a light splitting unit capable of splitting light emitted by the light source into two beams of reference light and object light, and a light combining unit capable of combining the reference light and the object light, wherein a reference light transmission light path and an object light transmission light path are formed between the light splitting unit and the light combining unit, and a polarization detector is arranged at a light output end of the light combining unit, so as to generate phase shift interference fringes by rotating the angle of the polarization detector. The generating method is based on the generating system. The invention realizes the generation of four high-speed and high-precision phase-shift interference fringes, solves the problems of low speed, high cost and poor precision of the traditional phase-shift interference fringe generation device to a great extent, and solves the malignant problems of inaccurate measurement and the like caused by the change of the measuring environment due to the high speed of the device to a certain extent.
Description
Technical Field
The invention belongs to the field of digital holography, and particularly relates to generation of interference fringes of digital holography.
Background
The digital holography is a method for reconstructing a digital light field by utilizing an optical coherence related to a diffraction principle, and takes the point in each three-dimensional space of the surface of an opaque object reflecting light or the internal structure of a transparent and semitransparent object transmitting light as a point light source, calculates the light wave phase when the point light sources emit light by utilizing a mathematical formula of optical interference and diffraction, and realizes nano ultra-precise three-dimensional measurement on the surface of the opaque object or the shape of the transparent and semitransparent object according to an interferometry.
When digital holographic ultra-precise three-dimensional measurement is carried out, two steps of interference fringe recording and object light reconstruction are needed. First, a laser beam having a long interference distance is used as a light source, and a beam splitter is used to split one laser beam into two laser beams, and the two split laser beams can be considered to have the same phase or a very small phase difference due to the physical optical characteristics of the beam splitter. Secondly, one of the laser beams does not penetrate any object or is not reflected by the object, and propagates in space, and is called reference light; and the other laser beam propagates in space after passing through the transparent object or being reflected by the opaque object, which is called object light; the reference light and the object light are propagated to another beam splitter and combined, and are irradiated to the same position of the digital camera sensor in the same propagation direction of the same optical axis. Since the reference light propagates in space without being blocked, the phase when irradiated to the digital camera sensor can be considered to be the same as the initial phase of the laser light emitted from the laser, and the reference light phase value can be considered to be 0; the object light undergoes a phase change due to reflection through the surface of the opaque object or transmission through the transparent object. According to the optical interference condition, two rows of light waves with the same propagation direction, the same path, the same wavelength, the same phase difference and the same polarization direction can form interference fringes with alternate brightness in space, so that the reference light and the object light form interference fringes on the surface of the sensor of the digital camera, the brightness amplitude of the interference fringes is cosine wave (cos), and the phase of the interference fringes depends on the phase difference of the object light and the reference light. Further, the digital camera sensor digitizes the interference fringes, and records the interference fringes of the object light and the reference light in the form of a digital image. Since the digital camera sensor can record only light intensity information, positive and negative of the phase difference between the object light and the reference light cannot be distinguished for interference fringes of cosine wave (cos) amplitude variation. In order to accurately calculate the positive and negative phase differences, it is necessary to mathematically calculate the interference fringes using digital fresnel diffraction transformation, and then obtain the correct signed phase difference by bandpass filtering in the fresnel transformation domain. Finally, the phase difference change 2pi (i.e., 360 °) represents a distance difference (optical path difference) of one optical wavelength from the reference plane, which is interferometry, and when the phase difference change exceeds 2pi, a phase connection method is required, so that three-dimensional reconstruction of the surface shape of the opaque object or the shape of the transparent object can be realized. Because the wavelength unit of visible light is nanometer, the digital holographic three-dimensional measurement can realize nanometer ultra-precise three-dimensional measurement.
The quality of the recorded interference fringes directly determines the error of the measurement and the signal-to-noise ratio. In practice, on the one hand, optical devices made of glass, mica or crystal are extremely prone to multiple reflections on their surface, and these reflected light rays can produce interference fringes on the digital camera sensor and are recorded as noise together with the object light interference fringes reflecting the deformation of the object, which has a great adverse effect on the measurement. On the other hand, there is a method called phase shift digital holographic measurement in which interference fringe images of four different reference light paths are recorded by changing the reference light path (3 times, 1/4 path each time, that is, 0.5pi phase value), the phase difference between correct reference light with a symbol and object light is directly calculated by using a phase shift method, and substituted into digital fresnel diffraction conversion, without bandpass filtering after conversion, loss of interference information is avoided, and measurement accuracy is greatly improved.
However, the method has two disadvantages that firstly, the piezoelectric micro-deformation reflector is needed to be used for changing the optical path of the reference light, and the reflector is expensive; secondly, the digital holographic three-dimensional measurement requires that the piezoelectric micro-deformation reflector deforms to tens to hundreds of nanometers at a time, and for such requirement, the deformation precision of the piezoelectric micro-deformation reflector is low, and the phase difference of the formed interference fringes cannot be kept to be accurate by 0.5pi, so that the high-precision three-dimensional measurement cannot be realized; finally, the four phase-shift interference fringe images are not shot at the same moment, and the shooting is slow due to the low deformation speed of the piezoelectric micro-deformation reflecting mirror, and the influence of external factors such as air flow, environmental vibration, temperature change and the like is easily received in the process, for example, the air flow can bring interference fringe change, so that the phase shift difference of the four interference fringes can not be kept accurate by 0.5p i, and the measurement result and the measurement precision are greatly influenced.
Disclosure of Invention
In order to solve the problems, the invention provides an interference fringe generating system and an interference fringe generating method, which can finish the generation of four phase-shift interference fringes in a very short time, ensure the high precision of phase differences among the interference fringes, solve the problems of high price, low precision and low generation speed existing in the conventional interference fringe generating device to a great extent, and solve the malignant problems of inaccurate measurement and the like caused by the change of a measurement environment to a certain extent due to the high speed of the invention.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the phase shift interference fringe generating system comprises a light source capable of emitting linearly polarized light, a light splitting unit capable of splitting light emitted by the light source into two beams of reference light and object light, and a light combining unit capable of combining the reference light and the object light, wherein a reference light transmission light path and an object light transmission light path are formed between the light splitting unit and the light combining unit, a polarization detector capable of enabling the reference light and the object light with different polarization directions to interfere to form interference fringes is arranged at a light output end of the light combining unit, and the phase shift interference fringes are generated by rotating the angle of the polarization detector.
As a further optimization of the present invention, the polarization detector includes a light modulation unit capable of mutually converting circularly polarized light and linearly polarized light, and a polarization plate capable of transmitting polarized light of a single direction, the light modulation unit and the polarization plate being sequentially spaced apart.
As a further optimization of the invention, the object light transmission light path comprises a first unpolarized light splitter, a transparent target object and a second unpolarized light splitter which are sequentially arranged, wherein the first unpolarized light splitter and the second unpolarized light splitter are symmetrically arranged at two sides of the target object, and the first unpolarized light splitter and the light combining unit are respectively arranged at two vertical light emergent ends of the light splitting unit.
As a further optimization of the invention, the object light transmission light path comprises an opaque target object, and the object light is reflected after passing through the opaque target object.
As a further optimization of the invention, a plane reflector is arranged on the light emitting path of the light source, the plane reflector is arranged on one side of the light splitting unit, the side is separated from the light source, and the light passing through the plane reflector is reflected to the light splitting unit.
As a further optimization of the invention, the light splitting unit and the light combining unit are both polarization light splitters.
As a further optimization of the invention, the dimming unit is a 1/4 wavelength plate.
As a further optimization of the invention, a 1/2 wavelength plate is arranged between the light source and the light splitting unit so as to emit linearly polarized light with a certain polarization angle.
A phase shift interference fringe generation method based on the phase shift interference fringe generation system of any of the above embodiments includes the following steps:
starting a phase-shift interference fringe generation system;
rotating the polarizing plate for multiple times to form different angles of the phase difference between the reference light and the object light so as to obtain a phase-shift interference fringe image;
from the obtained phase-shifted interference fringe image, a phase value is calculated.
As a further optimization of the present invention, in the step of rotating the polarizing plate, the polarizing plate is rotated four times, the rotation angle is sequentially 0 degrees, 45 degrees, 90 degrees and 135 degrees with respect to the initial angle, and the corresponding interference fringe phase change is 0 degrees, 90 degrees, 180 degrees and 270 degrees with respect to the interference fringe of the initial phase. .
Compared with the prior art, the invention has the advantages and positive effects that:
1. according to the interference fringe generating system, four phase-shift interference fringe images can be obtained through the arrangement of the polarization detector, and the phase-shift interference fringe can be obtained in real time through rotating the polarization plate at a high speed, so that the problems of high price, low precision and low generating speed existing in the conventional interference fringe generating device are solved to a great extent, and meanwhile, the malignant problems of inaccurate measurement and the like caused by the change of the measuring environment are solved to a certain extent due to the high speed of the interference fringe generating system.
2. The interference fringe generating system of the invention has low price of the polarization detector consisting of the 1/4 wavelength plate and the polarization plate, and has lower cost compared with the expensive piezoelectric micro-deformation plane mirror, thereby realizing extremely high cost performance.
Drawings
FIG. 1 is a block diagram illustration of a phase-shifting interference fringe generation system of the present invention;
FIG. 2 is a schematic diagram of a phase-shifting interference fringe generating system according to a first embodiment of the present invention;
FIG. 3 is a schematic diagram of a phase-shifting interference fringe generation system according to a second embodiment of the present invention;
FIG. 4 is a schematic diagram of a polarizing plate rotated by 0 degrees with respect to an initial angle in the phase-shift interference fringe generation method of the present invention;
FIG. 5 is a schematic diagram of a polarizing plate rotated 45 degrees relative to an initial angle in the phase-shift interference fringe generation method of the present invention;
FIG. 6 is a schematic diagram of a polarizing plate rotated 90 degrees relative to an initial angle in the phase-shift interference fringe generation method of the present invention;
FIG. 7 is a schematic diagram showing a polarizing plate rotated 135 degrees with respect to an initial angle in the phase-shift interference fringe generation method of the present invention;
FIG. 8 is a schematic diagram of a phase-shifted interference fringe generated by the present invention.
In the above figures: 1. a light source; 11. a 1/2 wavelength plate; 12. a planar mirror; 2. a light splitting unit; 3. reference light transmission path; 4. an object light transmission path; 41. a first unpolarized beam splitter; 42. a transparent target; 43. a second non-polarizing beam splitter; 44. a non-transparent target; 5. a light combining unit; 6. a polarization detector; 61. a dimming unit; 62. a polarizing plate; 63. a digital camera sensor; 7. 1/4 wavelength plate.
Detailed Description
The present invention will be specifically described below by way of exemplary embodiments. It is to be understood that elements, structures, and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
In the description of the present invention, it should be noted that the positional or positional relationship indicated by the terms such as "inner", "outer", "upper", "lower", "front", "rear", etc. are based on the positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In addition, in order to distinguish the overlapping light rays from the partial light rays in the drawing of the present invention, the overlapping light rays are offset in the drawing, but in practice, the light rays are all transmitted in a straight line and do not incline.
Referring to FIG. 1, a block diagram of a phase-shifting interference fringe generation system of the present invention is shown. As shown in the figure, the phase-shift interference fringe generating system of the present invention comprises a light source 1 capable of emitting linearly polarized light, the light source 1 is preferably a laser light source having a fixed wavelength; the light source 1 can be divided into a light splitting unit 2 for forming two beams of reference light and object light and a light combining unit 5 for combining the reference light and the object light, a reference light transmission light path 3 and an object light transmission light path 4 are formed between the light splitting unit 2 and the light combining unit 5, a polarization detector 6 capable of enabling the reference light and the object light with different polarization directions to interfere to form interference fringes is arranged at the light output end of the light combining unit 5, and the phase shift interference fringes are generated by rotating the angle of the polarization detector 6.
In the above, four phase shift interference fringe images are obtained through the arrangement of the polarization detector, and the phase shift interference fringe can be obtained in real time by rotating the polarization plate at a high speed, so that the problems of high price, low precision and low generation speed existing in the conventional interference fringe generation device are solved to a great extent, meanwhile, the malignant problems of inaccurate measurement and the like caused by the change of the measurement environment are solved to a certain extent due to the high speed, and stable and reliable ultra-precise digital holographic three-dimensional measurement is formed.
As further shown in fig. 2, the polarization detector 6 includes a light modulation unit 61 for mutually converting circularly polarized light and linearly polarized light, and a polarizing plate 62 for transmitting polarized light in a single direction, and the light modulation unit 61 and the polarizing plate 62 are sequentially spaced apart. Among the above, the light control unit 61 is preferably a 1/4 wavelength plate, and since the 1/4 wavelength plate can change linearly polarized light into circularly polarized light that rotates and vibrates in space, the polarization direction of circularly polarized light changes with the propagation in a circular shape, and the initial polarization direction is determined by the rotation direction of the 1/4 wavelength plate. Meanwhile, the polarization detector 6 of the present invention further includes a digital camera sensor 63 that can collect the phase-shifted interference fringes.
With further reference to FIG. 2, a first embodiment of the phase-shifting interference fringe generation system of the present invention is shown. As shown in fig. 2, in this embodiment, the observation target is a transparent object, the optical path of the object light transmission includes a first unpolarized beam splitter 41, a transparent object 42, and a second unpolarized beam splitter 43 that are sequentially disposed, the first unpolarized beam splitter 41 and the second unpolarized beam splitter 42 are symmetrically disposed on two sides of the transparent object 42, and the first unpolarized beam splitter 41 and the light combining unit 5 are respectively disposed on two perpendicular light emitting ends of the light splitting unit 2. Meanwhile, it is preferable that a 1/2 wavelength plate 11 is provided between the light source 1 and the spectroscopic unit 2 to emit linearly polarized light having a certain polarization angle.
To further illustrate this embodiment, the following is a specific description in connection with the optical path:
the linearly polarized light emitted from the light source 1 is transmitted through the 1/2 wavelength plate 11, and the rotation angle of the 1/2 wavelength plate 11 is adjusted to output linearly polarized light having a certain polarization angle. The linearly polarized light is split into two beams after passing through the beam splitting unit 2, one beam is an object light transmission light path 3, the initial beam is horizontally polarized light, the other beam is a reference light transmission light path 4, the initial beam is vertically polarized reference light, the light intensity of the two beams is determined according to the rotation angle of the 1/2 wavelength plate, and the 1/2 wavelength plate is preferably adjusted to enable the light intensity of the two beams to be the same. The horizontally polarized light is reflected by the first unpolarized beam splitter 41, changes phase when passing through a transparent target 42 such as a cell, and becomes horizontally polarized object light, which is reflected by the second unpolarized beam splitter 43. And the vertically polarized reference light is directly transmitted and irradiated to the light combining unit 5 for combining the reference light and the object light, and is overlapped with the horizontally polarized object light. The light combining means 5 reflects the vertically polarized light and transmits the horizontally polarized light, and therefore, the vertically polarized reference light and the horizontally polarized object light are superimposed without attenuation and enter the polarization detector 6, and at this time, since the polarization directions of the vertically polarized reference light and the horizontally polarized object light are different, an interference phenomenon does not occur between the two before entering the polarization detector 6. The polarization detector 6 is composed of a light adjusting unit 61 and a polarizing plate 62, and the vertical polarization reference light and the horizontal polarization object light first pass through the light adjusting unit 61, and are changed from linear polarization light to circular polarization light, at this time, since the polarization directions of both light entering the light adjusting unit are different, the initial rotation directions of the circular polarization light when passing through the light adjusting unit 61 are opposite, and therefore, the polarization rotation directions of the circular polarization reference light and the circular polarization object light are opposite when propagating in space, at this time, since the polarization directions of both light are opposite, no interference phenomenon occurs. The circularly polarized reference light and the circularly polarized object light pass through the polarizing plate 62 to become linearly polarized reference light and linearly polarized object light, and propagate in the same polarization direction on the plane of the digital camera sensor 63, and at this time, since the two polarization directions are the same, the phase difference is constant, the wavelength is the same, and the propagation direction is the same, an interference phenomenon occurs. Because the polarization direction of optical noise such as multiple reflections on the surface of the optical device is not the same as that of the incident reference light and object light, interference phenomenon together with the reference light and object light cannot occur on the digital camera sensor 63, so that clear interference fringes with small noise and high precision can be obtained by an optical method, the problem of small signal to noise ratio in common optical interference is solved, and a high-quality basis is provided for accurate digital holographic three-dimensional measurement.
On the other hand, the polarizing plate 62 in the polarization detector has the capability of locking the phase difference between the circularly polarized reference light and the circularly polarized object light, and adds an additional set phase difference to the phase difference between the object light generated by the object itself and the reference light, thereby realizing the generation of phase-shift interference fringes.
Referring to fig. 3, fig. 3 is a schematic structural view of a second embodiment of the present invention. As shown in fig. 3, in this embodiment, the observation target is an opaque target, and in this embodiment, the object light transmission optical path 4 includes an opaque target 44, and the object light is reflected after passing through the opaque target. The light source 1 is provided with a plane mirror 12 on its light emitting path, and the plane mirror 12 is disposed on one side of the light splitting unit 2, and the side is separated from the light source on both sides. Thus, the light passing through the plane mirror 12 is reflected to the spectroscopic unit 2. Meanwhile, in this embodiment, it is preferable that a 1/4 wavelength plate is provided between the spectroscopic unit 2 and the plane mirror 12, and between the opaque target 44 and the spectroscopic unit 2, so as to convert circularly polarized light into linearly polarized light and linearly polarized light into circularly polarized light. In this embodiment, the spectroscopic unit 2 and the light combining unit 5 are the same member.
To further illustrate this embodiment, the following is a specific description in connection with the optical path:
the light source 1 emits linearly polarized light, and the linearly polarized light passes through the 1/2 wavelength plate and irradiates the light splitting unit 3 after the polarization angle is adjusted. The linear polarization laser is split into two beams by the light splitting unit 3, one beam is an object light transmission light path 3, which is initially horizontal polarization light, the other beam is a reference light transmission light path 4, which is initially vertical polarization reference light, and the light intensities of the two beams are determined according to the rotation angle of the 1/2 wavelength plate, and the 1/2 wavelength plate is preferably adjusted so that the light intensities of the two beams are the same. The horizontal polarized light of the object light transmission path is changed into circularly polarized light through the 1/4 wavelength plate, reflected by the plane mirror into circularly polarized reference light, and is changed into vertically polarized reference light through the 1/4 wavelength plate again. The other beam of light output by the light splitting unit 2 is vertically polarized light, is changed into circularly polarized light by a 1/4 wavelength plate on the reference light transmission path, irradiates an opaque object to emit, becomes circularly polarized object light, and is changed into horizontally polarized object light again by the 1/4 wavelength plate. The vertical polarization reference light is reflected by the light combining unit 5, the horizontal polarization object light directly passes through the light combining unit 5, and the two light beams are combined by the light combining unit to form a beam of light, and at the moment, the polarization directions of the two light beams are orthogonal, so that interference fringes cannot be generated. After passing through the light adjusting unit 61, the vertically polarized reference light becomes circularly polarized reference light, the horizontally polarized object light becomes circularly polarized object light, and the circularly polarized reference light and the circularly polarized object light have opposite circular polarization rotation directions. The two are modulated into linear polarization reference light and linear polarization object light having the same polarization direction after passing through the polarizing plate 62, and the two have constant phase difference, the same polarization direction, the same propagation direction, and the same wavelength, so that interference is formed on the surface of the digital camera sensor 63.
In this embodiment, as in the case of the interference of a transparent object, noise due to multiple reflections on the surface of the optical device is eliminated by a polarization detector composed of a light adjusting unit and a polarizing plate, and the polarizing plate in the polarization detector is rotated to calculate a phase shift interference fringe of a signed and correct phase difference between the reference light and the object light.
Of the above, preferred embodiments are: the light splitting unit and the light combining unit are both polarization light splitters. The dimming unit is a 1/4 wavelength plate.
Referring to fig. 4-8, the present invention further provides a method for generating phase-shift interference fringes, which is based on the phase-shift interference fringe generating system according to any one of the above embodiments, and includes the following steps:
starting a phase-shift interference fringe generation system;
rotating the polarizing plate for multiple times to form different angles of the phase difference between the reference light and the object light so as to obtain a phase-shift interference fringe image;
from the obtained phase-shifted interference fringe image, a phase value is calculated.
Specifically, in the step of rotating the polarizing plate, the polarizing plate is rotated four times, the rotation angle is 0 degrees, 45 degrees, 90 degrees, and 135 degrees with respect to the initial angle in order, and the corresponding interference fringe phase change is 0 degrees, 90 degrees, 180 degrees, and 270 degrees with respect to the interference fringe of the initial angle.
As shown in fig. 4 to 8, the noise in the interference fringe image is small, the phase shift interference fringe with the phase difference of 90 degrees can be obtained by rotating the polarizing plate, and the correct phase distribution can be obtained by calculating the phase shift method.
The concrete explanation is as follows:
as shown in fig. 4, when the polarization angle of the polarizing plate is the same as the polarization direction of the circularly polarized reference light at a specific time (assuming 0 degree), the reference light directly passes through the polarizing plate to become linearly polarized light, and the object light needs to be rotated by-90 degrees to become linearly polarized light having the same polarization direction as the reference light through the polarizing plate, and interfere with the reference light. The object light has a delay of 1/4 wavelength before the object light interferes with the reference light, that is, the reference light has an optical path difference of 1/4 wavelength relative to the object light, and the phase difference of the two is-90 degrees.
As shown in fig. 5, when the polarizing plate is rotated 45 degrees, the reference light is rotated 45 degrees, and the object light is interfered by the polarizing plate after being rotated-45 degrees, and both are rotated in opposite directions by 45 degrees, so that the optical path difference is the same, and the phase difference is 0 degrees.
As shown in fig. 6, when the polarizing plate is rotated by 90 degrees, it is assumed that the object light orthogonal to the polarization direction of the reference light at this time has the same polarization direction as the grating direction of the polarizing plate, and directly transmits the polarizing plate, whereas the reference light is rotated by 90 degrees to be emitted through the polarizing plate and the object light. At this time, the reference light has an optical path difference of 1/4 wavelength with respect to the object light, and the two are 90 degrees out of phase.
As shown in fig. 7, when the polarizing plate is rotated 135 degrees, the reference light is rotated 135 degrees, the object light is rotated-315 degrees, and interference occurs through the polarizing plate, and at this time, the object light is rotated-315 degrees in the same phase as when rotated 45 degrees, so that there is an optical path difference of 1/2 wavelength between the reference light and the object light, and the phases are different by 180 degrees.
Through the above, the polarizing plate rotates 0 degrees, 45 degrees, 90 degrees and 135 degrees, and the corresponding additional phase differences between the reference light and the object light are-90 degrees, 0 degrees, 90 degrees and 180 degrees, namely 0 degrees, 90 degrees, 180 degrees and 270 degrees, and the additional phase differences are the phase shifts of the interference fringes. The mathematical formula is shown in table 1.
TABLE 1 relationship between rotation angle of polarizing plate and interference fringe phase shift
Each interference fringe in the table 1 accords with a formula of a phase shift method, the polarizing plate is rotated for 4 times at a difference angle of 45 degrees, four phase shift interference fringe images can be obtained, the phase shift interference fringe can be obtained in real time by rotating the polarizing plate at a high speed (at a speed of more than 100 revolutions per second), adverse effects on measurement due to environmental factors are greatly reduced, and stable and reliable ultra-precise digital holographic three-dimensional measurement is formed.
Meanwhile, the polarization detector consisting of the dimming unit and the polarization plate is low in price, and extremely high cost performance can be realized compared with an expensive piezoelectric micro-deformation plane mirror. To fully illustrate the cost performance of the present application, a price comparison is specifically given in table 2, where the price is 28 days at 2017, 8, selected from the guided offers by the matter price office:
table 2 comparison of the phase-shifted interference fringe systems of the present application with existing devices
Through the above comparison of table 2, it can be further seen that the technical scheme of this application not only control the precision higher, and the technical scheme of this application is because of adopting polarizing plate and 1/4 wavelength board to replace the piezoelectric micro-deformation speculum in the current, and the price is far lower than current equipment, has abundant price advantage.
Claims (5)
1. The phase shift interference fringe generating system comprises a light source capable of emitting linearly polarized light, a light splitting unit capable of splitting light emitted by the light source into two beams of reference light and object light, and a light combining unit capable of combining the reference light and the object light, and is characterized in that: a reference light transmission light path and an object light transmission light path are formed between the light splitting unit and the light combining unit, a polarization detector capable of enabling reference light and object light with different polarization directions to interfere to form interference fringes is arranged at the light output end of the light combining unit, and phase shift interference fringes are generated by rotating the angle of the polarization detector;
the polarization detector comprises a dimming unit capable of mutually converting circularly polarized light and linearly polarized light and a polarizing plate capable of transmitting polarized light in a single direction, wherein the dimming unit and the polarizing plate are sequentially arranged at intervals; the light splitting unit and the light combining unit are both polarization light splitters; the dimming unit is a 1/4 wavelength plate; a 1/2 wavelength plate is arranged between the light source and the light splitting unit so as to emit linearly polarized light with a certain polarization angle.
2. The phase-shifting interference fringe generation system of claim 1, wherein: the object light transmission light path comprises a first unpolarized light splitter, a transparent target object and a second unpolarized light splitter which are sequentially arranged, wherein the first unpolarized light splitter and the second unpolarized light splitter are symmetrically arranged on two sides of the target object, and the first unpolarized light splitter and the light combining unit are respectively arranged at two vertical light emergent ends of the light splitting unit.
3. The phase-shifting interference fringe generation system of claim 1, wherein: the object light transmission light path comprises an opaque object, and the object light is reflected after passing through the opaque object.
4. A phase-shifting interference fringe generating system as recited in claim 3, wherein: the plane reflector is arranged on the light emitting path of the light source, the plane reflector is arranged on one side of the light splitting unit, the side is separated from the light source at two sides, and the light passing through the plane reflector is reflected to the light splitting unit.
5. A phase-shifting interference fringe generation method based on the phase-shifting interference fringe generation system of any one of claims 1-4, characterized by: the method comprises the following steps:
starting a phase-shift interference fringe generation system;
rotating the polarizing plate for four times, wherein the rotation angle is 0 degree, 45 degrees, 90 degrees and 135 degrees relative to the initial angle in sequence, and the corresponding interference fringe phase change is 0 degree, 90 degrees, 180 degrees and 270 degrees relative to the interference fringe of the initial angle, so that the phase difference of the reference light and the object light forms different angles to obtain a phase-shift interference fringe image;
from the obtained phase-shifted interference fringe image, a phase value is calculated.
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