CN105300276A - Dual-wavelength single-exposure interference measuring method and system - Google Patents

Abstract

The present invention provides a dual-wavelength single-exposure interferometry method and system based on spatial carrier frequency phase shift. A monochrome black-and-white image sensor is used to record a dual-wavelength aliasing off-axis interferogram including spatial carrier frequency, and then the One of the interferograms is converted into multiple dual-wavelength phase-shifted sub-interferograms, and then the least squares phase extraction algorithm is used to simultaneously obtain two wrapped phases at a single wavelength, and then a simple subtraction operation can be used to obtain the composite wavelength lower phase. The feature of the present invention is that it proposes a large-scale single-exposure interferometry method. This measurement method has a simple device, but is stable and reliable, and has high precision. The most obvious advantage is that only one interferogram needs to be collected to realize two The phase shift under the wavelength expands the application field of the phase shift method, and it has a good application prospect in preventing environmental interference or dynamic phase measurement in phase measurement.

Description

A dual-wavelength single-exposure interferometry method and system

technical field

The invention relates to the field of optical interferometry or digital holography, in particular to a method and system for single-exposure dual-wavelength interferometry based on space carrier frequency phase shift technology.

Background technique

Optical interferometry technology uses the interference principle of light to record the phase information of the object to be measured in the form of interference fringes, and the phase of the object to be measured can be obtained by processing the interference fringes. Usually the use of single-wavelength measurement technology will encounter the problem of phase ambiguity caused by the fluctuation of the object to be measured beyond the measurement wavelength. The use of dual-wavelength measurement technology can generate a synthetic wavelength (equivalent wavelength) that is much larger than the original wavelength. , so as to avoid the problem of understanding the phase wrapping, and can realize the measurement of abrupt objects with large gradient changes, such as step grooves. Before obtaining the synthesized wavelength, it is necessary to extract the single-wavelength package phase distribution map. These extraction techniques usually fall into two categories: one is the time-domain phase shift method, and the other is the space-domain Fourier transform method. Generally speaking, the processing accuracy of the time-domain phase-shift method is higher than that of the Fourier transform method, but the time-domain phase-shift method needs to collect a set of phase-shifted interference fringe patterns at each single wavelength to extract the single-wavelength wrapped phase or Simultaneously collect a series of dual-wavelength simultaneous phase-shifting interferograms to extract the wrapped phase at a single wavelength. The measurement results are easily affected by external vibration and air disturbance, and this type of method is difficult to use for dynamic phase measurement. Off-axis dual-wavelength digital holography based on spatial Fourier transform only needs to collect a carrier-frequency interference fringe pattern that records two wavelength interference information at the same time, and then undergo operations such as Fourier transform, filtering, and Fourier inverse transform. The process can extract two single-wavelength package phases, and then obtain the synthetic wavelength phase distribution, but the spatial frequency of the object measured by this method is limited, and its measurement accuracy is greatly affected by the filtering window and noise, and the Fourier transform method There are also problems such as carrier frequency drift error, spectrum leakage, and boundary effects caused by Gibbs effect.

Contents of the invention

In order to overcome the technical problems of phase ambiguity, low precision, high requirements for environmental stability and complex and time-consuming measurement process in the prior art when measuring large mutation objects, the present invention provides a technology based on space carrier frequency phase shift The single-exposure dual-wavelength interferometry method only needs to collect a dual-wavelength aliasing off-axis interferogram from a single black-and-white image sensor to simultaneously extract the wrapped phase at two wavelengths, and then use the frequency difference of the two wavelengths to generate Synthetic wavelengths to achieve the measurement of larger jump objects, the invention combines the advantages of the time domain phase shift method and the Fourier transform method, while maintaining the measurement accuracy of the time domain phase shift method, it expands the measurement range and reduces the The environmental stability requirements are met, the acquisition time is reduced, and it is beneficial to realize dynamic phase measurement.

A dual-wavelength single-exposure interferometry method, using a monochromatic black-and-white image sensor camera to collect a dual-wavelength aliasing off-axis interferogram containing a spatial carrier frequency; moving the interception area on the dual-wavelength aliasing off-axis interferogram , convert a dual-wavelength aliasing off-axis interferogram containing a space carrier frequency into an N-width sub-phase-shift interferogram; use the least squares phase extraction algorithm on the N-width sub-interferogram to calculate the object to be measured at two The package phase distribution under two wavelengths; use the package phase distribution under the two wavelengths to directly subtract to obtain the phase distribution of the object to be measured at the synthesized wavelength.

Specifically, the formation process of the dual-wavelength aliasing off-axis interferogram including the spatial carrier frequency is as follows: the light waves of the two wavelengths are respectively divided into reference light and object light, and their object light propagates in the same path, and after passing through the object to be measured, Then interfere with the reference light of their respective wavelengths, and converge on the target surface of the monochrome black-and-white image sensor camera to form a dual-wavelength aliasing off-axis interferogram; further, the object light that passes through the object to be measured passes through the first microscope After the objective lens, it interferes with the reference light of their respective wavelengths; further, the reference light under the two wavelengths respectively passes through the second microscopic objective lens and the third microscopic objective lens, and then respectively communicates with the The object light interferes; wherein, the parameters of the first, second and third microscopic objective lenses are the same.

Specifically, set the pixel in the upper left corner of the monochrome black-and-white image sensor camera as the origin, the X-axis is parallel to the pixel horizontal direction of the monochrome black-and-white image sensor camera, and the Y-axis is parallel to the pixel vertical direction of the monochrome black-and-white image sensor camera direction, when the object to be measured is not placed in the optical path, the dual-wavelength aliasing off-axis interferogram is formed by the aliasing of two straight fringes formed by two wavelengths respectively, and the directions of the straight fringes are orthogonal to each other, and are respectively Into plus or minus 45 degrees angle.

Specifically, the process of converting the dual-wavelength aliasing off-axis interferogram containing the spatial carrier frequency into N sub-interferograms is as follows: in the original collected dual-wavelength aliasing off-axis interferogram, along the X-axis or the Y-axis The intercepted area is moved with a step length of one pixel in the direction to obtain N sub-interferograms equivalent to the phase-shifted interferograms in the time domain, wherein N≥3.

Specifically, the sub-interferogram uses the least squares phase extraction algorithm to obtain phase distribution diagrams of the object to be measured corresponding to two wavelengths at the same time.

The present invention also provides a dual-wavelength single-exposure interferometry system, including: two lasers with different wavelengths; a monochrome black-and-white image sensor camera for collecting interferograms; An interferogram device, wherein the light waves of the two wavelengths are respectively divided into reference light and object light, and the object light at the two wavelengths propagates in the same path, and after passing through the sample to be measured, off-axis interference occurs successively with the reference light of the corresponding wavelength , converging on the target surface of the monochrome black-and-white image sensor camera to form a dual-wavelength aliasing off-axis interferogram containing the spatial carrier frequency; the computer is used to control and receive the monochrome black-and-white image sensor camera to collect the interferogram, from which the carrier frequency phase shift is obtained N sub-interferograms, using the least squares phase extraction algorithm, calculate the final phase distribution at the two wavelengths, and then subtract the two to obtain the phase distribution at the synthetic wavelength.

As a preferred version, the method provided by the invention comprises the following steps:

In the first step, a monochromatic black-and-white image sensor is used to collect a dual-wavelength aliasing off-axis interference fringe containing a spatial carrier frequency, and then a sub-interferogram is obtained by intercepting the area where the phase needs to be calculated on a collected interferogram, and then Move the intercepted area one pixel to the right or down along the X direction or Y direction to obtain another sub-interferogram. In the same way, move one pixel at intervals to intercept an area of the same size, and move N-1 times in this way, that is N sub-interferograms can be obtained. Since the original interferogram contains the spatial carrier frequency, the interference signal at the same pixel position in the N sub-interferograms is obtained from the N pixels adjacent to the corresponding pixel position on the original interferogram , so the interference intensity at the fixed pixel position among the N sub-interferograms has a cosine distribution. Through such an operation, the original one space carrier frequency interferogram can be transformed into N interferograms with time domain phase shift.

Step 2: Randomly set the initial phase shift of N sub-interferograms at two wavelengths, and use the least squares iterative phase extraction algorithm combined with the initially set phase shift to calculate the wrapping phase at two wavelengths at the same time and

Step 3: Since the initial phase shift is randomly set, it is usually inaccurate, and the resulting phase distribution and Not accurate either. the above inaccurate and Substituting the least squares iterative phase extraction process to obtain a new set of phase shifts at two wavelengths and

The fourth step, the above new phase shift amount and As the new initial phase shift amount, repeat the second step and the third step until the difference between the two calculated phase shift amounts is smaller than the preset ideal threshold value, and then the loop is exited. The exact amount of phase shift thus obtained and

The fifth step, the final calculated phase shift amount and Substituting the least squares iterative process to calculate the accurate wrapping phase at two wavelengths and

The sixth step is to combine the wrapped phases under the two wavelengths and Subtract and compensate at the jump position ("Directshapemeasurementbydigitalwavefrontreconstru-ctionandmultiwavelengthcontouring"OpticalEngineering39,79-85(2000)), you can get the phase distribution at the synthesized wavelength Since the effective measurement range of the synthesized wavelength is much larger than that of a single wavelength, the phase under the synthesized wavelength does not need to go through the process of unwrapping, and the real height distribution information of the object can be obtained directly through conversion.

As another preferred solution, the present invention also includes replacing the above-mentioned steps 2, 3 and 4 with direct use of the Fourier transform method ("Fourier-transformmethodofphase-shiftdetermination" ApplOpt40, 2886-2894 (2001)) to simultaneously extract the N The Accurate Phase Shift at Two Wavelengths in the Amplitude and Phase Shift Interferogram and Then it is substituted into the least squares phase extraction algorithm to obtain the wrapped phase at two wavelengths at the same time and The wrapped phase at the two wavelengths and Direct subtraction can obtain the package phase distribution of the object to be measured.

Compared with prior art, the present invention has following advantage:

(1) Compared with the single-wavelength measurement method, the method provided by the present invention can realize the measurement of objects with large gradient changes, greatly increases the measurement range, and expands the application field of interferometry.

(2) Compared with the complex and time-consuming measurement process of other dual-wavelength phase-shift interferometry methods, the method of the present invention only needs to collect one interferogram, the measurement process is simple and reliable, and it also has the advantage of not being disturbed by the environment, and can be applied to vibration Phase measurements in the environment can also be used for dynamic phase monitoring.

(3) The device used in the method of the present invention is simple, does not require precise phase shifting devices and complicated collection processes, and only needs to collect an interference pattern with a monochrome black-and-white image sensor, which is simple and convenient.

(4) The method of the present invention converts an interferogram comprising a space carrier frequency into several sub-phase shift interferograms, transforms the phase shift technology from the time domain to the space domain application, inherits the high precision of the phase shift method, and avoids It eliminates the disadvantage of using multiple phase shifts of the phase shifting device in the traditional phase shift method measurement.

(5) Compared with the dual-wavelength space-domain carrier frequency Fourier transform method, the method of the present invention can avoid the influence of the filtering window and noise on the measurement accuracy.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work. The above and other objects, features and advantages of the present invention will be more clearly illustrated by the accompanying drawings. Like reference numerals designate like parts throughout the drawings. The drawings are not intentionally scaled according to the actual size, and the emphasis is on illustrating the gist of the present invention.

FIG. 1 is a schematic diagram of a dual-wavelength single-exposure interferometry system based on spatial carrier frequency phase shift technology adopted in the method of the present invention.

Fig. 2 is a schematic diagram of converting an interferogram including space carrier frequency into four sub-interferograms with phase shift in time domain by the method of the present invention.

Fig. 3 is a dual-wavelength carrier-frequency interferogram collected by the method of the present invention using the system shown in Fig. 1 .

Fig. 4 is a diagram of the wrapped phase distribution at two wavelengths simultaneously extracted from a dual-wavelength aliasing off-axis interferogram by using the method of the present invention.

Fig. 5 is a phase distribution diagram of a helical phase plate at a synthesized wavelength recovered by the method of the present invention.

Among them, the marks in the accompanying drawings are specifically:

1 is a semiconductor-pumped solid-state laser; 2 is a He-Ne laser; 3-4 is a variable center density attenuation sheet; 5-9 is a beam splitter; 10-12 is a plane mirror; 13 is a first microscope objective; 14 is the second microscopic objective lens; 15 is the third microscopic objective lens; 16 is a monochromatic black and white image sensor; 17 is a sample; 18 is a computer.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

first embodiment

This embodiment will further illustrate the single-exposure dual-wavelength interferometry system based on the spatial carrier frequency phase shift technology described in the present invention with reference to the drawings and embodiments, but this should not limit the protection scope of the present invention.

As shown in Figure 1, the system includes: a semiconductor-pumped solid-state laser 1 with a wavelength of 532nm and a He-Ne laser 2 with a wavelength of 632.8nm; the two laser beams pass through a beam splitter 5 and a beam splitter 6 respectively After that, each is divided into two beams of light, one beam of reference light and one beam of object light. After the adjustment of the plane reflector 12 and the beam splitter 7, the object light at the two wavelengths propagates in the same path, and then passes through the measured sample 17 and the reference light of the two wavelengths reflected by the plane reflectors 10 and 11 respectively. Interference occurs between the beam splitter 9 and the beam splitter 8, and the plane mirrors 10 and 11 are adjusted so that the respective interference fringe patterns of the two wavelengths form an angle of plus or minus 45 degrees with the horizontal pixel direction of the image sensor 16 target surface; in the sample 17 The first microscope objective lens 13 is added between the beam splitter 8 to enlarge and image the object, and the second and third microscopes are respectively added between the plane mirror 11 and the beam splitter 8 and the plane mirror 10 and the beam splitter 9. Objective lenses 14, 15, in order to eliminate the secondary phase distortion brought by the first microscopic objective lens, form straight stripes. By tilting the plane mirrors 10 and 11, spatial carrier frequencies are respectively introduced into the interference patterns of the two wavelengths, and adjusting them can also adjust the directions of the interference fringes at the two wavelengths. The light beams at the two wavelengths interfere with each other and then are superimposed by light intensity, and then converge orthogonally on the target surface of the monochrome black-and-white image sensor 16 to form a dual-wavelength aliasing off-axis interferogram. Among them, the beam splitters 5-9 in the system are five beam splitters with the same parameters; the magnification of the three microscopes is 10, and the numerical aperture is 0.4. Sample 17 in this embodiment uses a VPP-1c spiral phase plate produced by RPCphotonics.

second embodiment

This embodiment will further illustrate the single-exposure dual-wavelength interferometry method based on the spatial carrier frequency phase shift technology described in the present invention with reference to the drawings and embodiments, but this should not limit the protection scope of the present invention.

Step 1. Collect the dual-wavelength aliasing off-axis interferogram including the spatial carrier frequency:

After the optical path system is built, use a computer to drive a monochrome black-and-white image sensor to collect a dual-wavelength aliasing off-axis interferogram, as shown in Figure 3, where the pixel (x, y) carries the interference signal intensity of the linear carrier frequency information It can be expressed as:

Among them, (x, y) represents the position of the pixel on the target surface, and the value ranges are 1≤x≤X and 1≤y≤Y respectively, and X and Y are the number of rows and columns of the dual-wavelength carrier frequency interference fringe pattern respectively number; l=1,2 represents the order of wavelengths; A(x,y) represents the sum of the interference background items of two wavelengths, Represents the modulation amplitude term of the interference fringe under the wavelength λ _l ; and Respectively represent the spatial carrier frequency quantities in the x and y directions under the wavelength λ _l , Indicates the phase value of the object at the wavelength λ _l .

Step 2, converting a dual-wavelength aliasing off-axis interferogram containing a spatial carrier frequency into an N-width sub-phase-shifted interferogram:

By moving the intercepted area horizontally or vertically with a step of one pixel, obtain N pieces of dual-wavelength space-domain carrier interference with phase shift with the number of pixels (X-R)×(Y-C) from the original interferogram In the figure, R and C are the number of rows and columns cut out from the original interferogram when intercepting each phase-shifted sub-interferogram, respectively. The schematic diagram of the operation process is shown in Figure 2: In Figure 2, assuming that the size of the original interferogram is 5×5 pixels, the intercepted area I ₂₂ I ₂₃ I ₃₂ I ₃₃ is the sub-interferogram I ₁ , as shown in the solid line in Figure 2 As shown in the box, then move the intercepted area to the right by one pixel along the X direction, and intercept I ₂₃ I ₂₄ I ₃₃ I ₃₄ as the sub-interferogram I ₂ , as shown in the solid line in Figure 2, as shown in the dotted line box in the figure, and then Move one pixel along the Y direction, intercept the area I ₃₂ I ₃₃ I ₄₂ I ₄₃ as the sub-interferogram I ₃ , and intercept the area I ₃₃ I ₃₄ I ₄₃ I ₄₄ as the sub-interferogram I ₄ . By analogy, the original off-axis dual-wavelength interferogram containing the space carrier frequency can be transformed into N phase-shifted interferograms, where the nth phase-shifted sub-interferogram is expressed as

where (x′, y′) is the pixel position in the sub-phase-shift interferogram, and the relationship between the n-th sub-phase-shift interferogram and the pixel position in the original dual-wavelength space-domain carrier-frequency interferogram is x′=xr and y'=yc, the value ranges are 1≤x'≤XR and 1≤y'≤YC respectively; c and r are the intercepted areas from the original interferogram starting position to Move c pixels and r pixels in the x direction and y direction, and the value ranges are 0≤r≤R and 0≤c≤C respectively; is a simplified representation including the phase to be measured and the phase of the carrier frequency; is the phase shift of the nth phase-shifted interferogram corresponding to the wavelength λ _l , which can be expressed as

${\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&pi;\&alpha;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&pi;\&beta;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Where n=(c+1)+r(C+1) is a sequence of phase-shifted interferograms; the total number of intercepted sub-phase-shifted interferograms is N=(r+1)(c+1). Since there will be no confusion in the following derivation, the pixel position of the phase-shifted sub-interferogram is still represented by (x, y).

Step 3. Randomly set the phase shift amount to determine the random initial wrapping phase:

Like the traditional time-domain phase shift algorithm ("Advanced iterative algorithm for phase extraction of random phase-shifted interferograms" Optics Letters.29, 1671-1673 (2004)), set the initial random phase shift amount under the two wavelengths respectively and They need to satisfy the relationship Expand formula (2) to write:

where a(x,y)=A(x,y),

In order to calculate the phase distribution, it is necessary to minimize the sum of squares of light intensity errors at the same pixel position of all interferograms, and the sum of squares of errors can be expressed as

Among them, I ^e (x, y) is the intensity of the interferogram measured by the experiment, and N represents the number of the interferogram. According to the principle of least squares, to make the formula (5) reach the minimum, there are:

Expand formula (5) and write it in the form of a matrix (the space coordinates (x, y) are omitted to make the expression concise):

DH=G(7)

in

In the formula T represents the transpose of the matrix. The random initial wrapping phase with carrier frequency information at two wavelengths can be solved by equation (7):

Step 4. Determine the quasi-accurate phase shift according to the random initial wrapping phase:

In the traditional phase shift algorithm, if the phase shift is known, the phase distribution can also be calculated, and vice versa, we further calculate the precise phase shift through the random initial wrapping phase obtained in the above steps. It is assumed that the background and modulation on the same interferogram are approximately equal at each pixel, and then define the following series of new variables: a'(x, y)=A(x, y), Then formula (2) can be expanded as:

In order to find the phase shift It is necessary to minimize the sum of the squares of the error of the light intensity of all pixels in the nth interferogram, and the sum of the squares of the error is expressed as:

where M represents the sum of pixels in each interferogram. To minimize the value of formula (13), the following formula requirements must be met:

According to the least squares method similar to Step 3, formula (13) can be written in the form of a matrix (space coordinates (x, y) are omitted):

D'H'=G'(15)

in

In the formula T represents the transpose of the matrix. Then the phase shift at two wavelengths can be determined by the following formula:

Step five, will get Substituting the above step 2 and step 3 to enter the next iterative cycle until the accurate package phase of the object under test with carrier frequency information is obtained and Then subtract the linear carrier frequency phase and The phase distribution of the object at two wavelengths can be obtained: and As shown in Figure 4.

In the above steps, the wrapping phase and the phase shift amount at two single wavelengths are simultaneously determined by using the least squares iterative process. Repeat step 3 and step 4 until the phase shift meets the convergence limit, and finally obtain the accurate wrapping phase at each single wavelength.

Phase shift The following convergence conditions need to be met:

Among them, k represents the number of iterations. ε is the preset ideal convergence threshold. if When formula (20) is satisfied, the iterative loop is terminated.

Step 6. Obtain the synthetic wavelength phase distribution

will get and By direct subtraction, the new phase distribution at the synthesized wavelength can be obtained:

In the formula Indicates the phase at the synthesized wavelength, h is the optical path difference after the light passes through the measured object, Λ=λ ₁ λ ₂ /|λ ₁ -λ ₂ | is the equivalent wavelength.

So far, through the method and system proposed by the present invention, the wrapped phase distribution at two wavelengths can be simultaneously extracted from a collected dual-wavelength carrier frequency interferogram, and then the phase distribution at the synthesized wavelength can be obtained as shown in FIG. 5 .

third embodiment

This embodiment will further illustrate the single-exposure dual-wavelength interferometry method based on the spatial carrier frequency phase shift technology described in the present invention with reference to the drawings and embodiments, but this should not limit the protection scope of the present invention.

In this embodiment, the system used is the same as that of Embodiment 1, and the implementation steps are to replace steps 2, 3, and 4 in Embodiment 2 with using the Fourier transform method to simultaneously extract the N-amplitude phase-shift sub-interference The exact phase shift at two wavelengths in the figure and The specific process is, after obtaining N phase-shift sub-interferograms in step 2, expand the n-th interferogram as:

in * means complex conjugate. Perform Fourier transform on formula (22) to get:

in and Respectively represent the spatial frequency coordinates obtained by Fourier transform with x and y as variables under the wavelength λ _l ; and hour, Get the maximum value:

Since the interference fringes of the two wavelengths are orthogonal, their spectra can be completely separated, so the phase shift at the two wavelengths can be obtained by the following formula:

in means from The spectrum value under the single wavelength λ _l separated in .

Get precise phase shifts at two wavelengths and Finally, by substituting the least squares phase extraction algorithm in Embodiment 2, the package phase of the object to be measured with carrier frequency information at two wavelengths can be calculated without an iterative process and Then subtract the linear carrier frequency phase and The phase distribution of the object at two wavelengths can be obtained: and All the other steps are the same as in the second embodiment.

The present invention is not limited to the above-mentioned specific implementation methods. According to the above-mentioned content, according to the common technical knowledge and conventional means in this field, without departing from the above-mentioned basic technical idea of the present invention, the present invention can also make other equivalent forms. Modifications, substitutions or alterations, such as the use of light sources of different wavelengths and interfering optical paths, all fall within the protection scope of the present invention.

Claims (10)

1. A double-wavelength single-exposure interferometry method, characterized in that it comprises the following steps: Use a monochromatic black-and-white image sensor camera to collect a dual-wavelength aliasing off-axis interferogram containing a spatial carrier frequency; convert the dual-wavelength aliasing off-axis interferogram containing a spatial carrier frequency into N (N≥3) amplitude and phase moving subinterferogram; Using a least squares phase extraction algorithm for the N sub-interferograms to calculate the phase distribution of the object to be measured at two wavelengths; using the wrapped phase subtraction of the two wavelengths to obtain the phase distribution of the object to be measured at the synthesized wavelength; The phase distribution of the object to be measured at the synthesized wavelength is mapped to the height distribution of the object to be measured to complete the three-dimensional measurement of the object to be measured. 2. The dual-wavelength single-exposure interferometry method according to claim 1, characterized in that: the formation process of the dual-wavelength aliasing off-axis interferogram comprising the spatial carrier frequency is: the dual-wavelengths are respectively divided into reference light and Object light, the object light at two wavelengths propagates in the same path, after passing through the object to be measured, then interferes off-axis with the reference light of their respective wavelengths, and converges on the image sensor target surface of the monochrome black and white digital camera to form a space containing The two-wavelength aliased off-axis interferogram of the frequency. 3. The dual-wavelength single-exposure interferometry method according to claim 2, characterized in that: the object light under the two wavelengths propagates in the same path, after passing through the object to be measured, after passing through the first microscope objective lens, and then separately Interference with the reference light of their respective wavelengths; The reference light at the two wavelengths respectively passes through the second microscopic objective lens and the third microscopic objective lens, and then interferes with the object light propagating in the common path; The parameters of the first microscopic objective, the second microscopic objective and the third microscopic objective are the same. 4. The dual-wavelength single-exposure interferometry method according to any one of claims 1-3, characterized in that: the pixel at the upper left corner of the monochrome black-and-white image sensor camera is set as the origin, and the X-axis is parallel to the monochrome black-and-white The horizontal direction of the pixels of the image sensor camera, the Y axis parallel to the vertical direction of the pixels of the monochrome black-and-white image sensor camera, when the object to be measured is not placed in the optical path, the dual-wavelength aliasing off-axis interferogram is formed by two wavelengths respectively The two straight stripes are mixed together, the directions of the straight stripes are orthogonal to each other, and they form an angle of plus or minus 45 degrees with the X axis. 5. The dual-wavelength single-exposure interferometry method according to claim 4, characterized in that: the acquisition process of the N sub-interferograms is: in the dual-wavelength aliasing off-axis interferogram, along the X-axis direction or the Y The intercepted area is moved with a step size of one pixel in the axial direction to obtain N sub-interferograms equivalent to the phase-shifted interferograms in the time domain, wherein N≥3. 6. The dual-wavelength single-exposure interferometry method according to claim 5, characterized in that: the least squares phase extraction algorithm firstly presets the random phase shift amount to obtain a random initial wrapping phase, and then obtains the random initial wrapping phase The new phase shift value is calculated using the least squares phase extraction algorithm through loop iterations, and the phase shift value and wrapping phase are obtained at the same time. 7. The dual-wavelength single-exposure interferometry method according to claim 5, characterized in that: the least squares phase extraction algorithm first extracts the phase shift between the sub-interferograms by the Fourier transform method, and then substitutes The least squares algorithm obtains the wrapped phase at two wavelengths at a time. 8. A dual-wavelength single-exposure interferometry system, characterized in that it comprises: two lasers with different wavelengths; Monochrome black and white image sensor camera; A device for generating a dual-wavelength aliasing off-axis interferogram, wherein the dual-wavelengths are respectively divided into reference light and object light, and the object light of the two wavelengths is in the same path, and after passing through the sample to be measured, it is successively combined with Two wavelengths of reference light interfere and converge on the target surface of the monochromatic black and white image sensor camera to form a dual wavelength aliasing off-axis interferogram; The computer is used to control and receive the dual-wavelength aliasing off-axis interferogram collected by the monochromatic black-and-white image sensor camera, use the least squares phase extraction algorithm to calculate the phase distribution at the two wavelengths, and then subtract the two to obtain Phase distribution at the synthesized wavelength. 9. The dual-wavelength single-exposure interferometry system according to claim 8, characterized in that: the reference light of the two wavelengths and the object light are in an off-axis relationship, and the interference formed by the reference light and the object light at the two wavelengths The stripe orientations are orthogonal to each other. 10. The dual-wavelength single-exposure interferometry system according to claim 9, characterized in that: the object light passes through the first microscope objective lens after passing through the object to be measured; the reference light passes through the first microscopic objective lens before interfering with the object light 2. The third microscopic objective lens; wherein, the parameters of the three microscopic objective lenses are the same.