Two-dimensional shock wave velocity measurement system based on polarization interference and data processing method

Abstract

The invention provides a two-dimensional shock wave velocity measurement system based on polarization interference and a data processing method, based on the principle of polarization interference, circularly polarized light with opposite rotation directions is obtained through two groups of 1 / 4 wave plates and synthesized for interference, and four-phase images with the phase difference of 90 degrees can be synchronously obtained through single exposure by utilizing a polarization camera. And further solving to obtain two-dimensional velocity field information. The system breaks through the limitation of one-dimensional measurement, is simple in overall structure and convenient to adjust, can be realized by utilizing a simple polaroid and a simple wave plate, is accurate and efficient in data processing, and lays a good technical foundation for two-dimensional shock wave velocity diagnosis.

Description

Technical Field

[0001] The present invention relates to the technical field of laser interferometry velocimetry, and more specifically, to a two-dimensional shock wave velocity measurement system and data processing method based on polarization interference. Background Art

[0002] The diagnosis of shock wave velocity plays an important role in many high energy density physics research fields. In the research of inertial confinement fusion (ICF), by accurately diagnosing the ion velocity and shock wave velocity in the microsecond to nanosecond transient process, the research on indicators such as shock pressure and shock symmetry can be realized. At the same time, in order to achieve an ideal compression state in the ICF process, it is required that the shock wave has extremely high spherical symmetry. However, due to the existence of various non-ideal factors, large-scale hydrodynamic instability structures will be formed under the action of the shock wave, resulting in the destruction of spherical compression. Therefore, it is of great significance to realize the non-uniformity diagnosis of two-dimensional shock waves.

[0003] The imaging velocity interferometer system for any reflector (VISAR) is a widely used velocity diagnosis technology. It mainly utilizes the optical Doppler effect, interferes two beams of light with a time delay by an interferometer, records the change information of the reflected light frequency of the wavefront to be measured, and records the fringe image through a streak camera with high time resolution. The accurate diagnosis of the shock wave velocity is realized by solving the change information of the fringe phase. Currently, the most maturely developed is the one-dimensional line VISAR, which can obtain the evolution information of the shock wave velocity in one-dimensional space over time, but it cannot accurately diagnose the non-uniformity information of the two-dimensional velocity field spatial distribution. Summary of the Invention

[0004] In order to overcome the defect that the above-mentioned prior art cannot accurately diagnose the non-uniformity information of the two-dimensional velocity field spatial distribution, the present invention provides a two-dimensional shock wave velocity measurement system and data processing method based on polarization interference. Based on the principle of polarization interference, multi-step phase shift is adopted, and a polarization camera is used for recording, so that a two-dimensional interference image of the surface to be measured can be obtained. Combining the corresponding data processing method, the spatial distribution information of the two-dimensional velocity field can be obtained.

[0005] To solve the above technical problems, the technical solution of the present invention is as follows: A two-dimensional shock wave velocity measurement system based on polarization interference, comprising: a laser, a polarizer, a beam splitter BS1, a beam splitter BS2, a beam splitter BS3, a reflector M1, a reflector M2, a first quarter-wave plate, a second quarter-wave plate, a polarization camera and a data processing module; The detection light emitted by the laser sequentially passes through the polarizer and the beam splitter BS1 and then is incident on the surface to be measured, and returns to the beam splitter BS1 after being reflected by the surface to be measured; the beam splitter BS1 injects the reflected light into the beam splitter BS2; After the reflected light is split by the beam splitter BS2, a first split light and a second split light are obtained; the first split light sequentially passes through a first quarter-wave plate and a mirror M1 and then is injected into the beam splitter BS3; the second split light sequentially passes through a mirror M2 and a second quarter-wave plate and then is injected into the beam splitter BS3; The fast axis directions of the first quarter-wave plate and the second quarter-wave plate are perpendicular to each other, and the two beams of light injected into the beam splitter BS3 are two beams of circularly polarized light with opposite rotation directions; The two beams of light injected into the beam splitter BS3 are combined and interfere and then are injected into the polarization camera, and a two-dimensional interference image of the surface to be measured is obtained; the two-dimensional interference image of the surface to be measured includes four-phase images with phases differing by 90 ° in sequence; The data processing module is electrically connected to the polarization camera, and is configured to receive the two-dimensional interference image of the surface to be measured and perform data processing to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured.

[0006] Preferably, the detection light emitted by the laser is polarized into 0 ° linear polarized light after passing through the polarizer; The first split light becomes left-handed circularly polarized light after passing through the first quarter-wave plate; The second split light becomes right-handed circularly polarized light after passing through the second quarter-wave plate.

[0007] Preferably, a polarization plate array is arranged in front of the photosensitive surface of the polarization camera, the polarization plate array is composed of repeated 2×2 grid units, and each grid unit includes four micro-polarization plates with polarization directions of 0 ° 、45 ° 、90 ° and 135 ° in sequence; each micro-polarization plate corresponds to a pixel on the photosensitive surface, and each pixel records an interference image of a single polarization direction.

[0008] Preferably, the system further includes a light receiving module, the detection light emitted by the laser sequentially passes through the polarizer and the beam splitter BS1 and then is incident on the light receiving module, and then is focused on the surface to be measured; The light receiving module includes at least one lens.

[0009] The present invention also provides a data processing method, which is based on the above two-dimensional shock wave velocity measurement system based on polarization interference and is applied to the data processing module, and includes the following steps: Obtain the two-dimensional interference image of the surface to be measured and the light intensity of each pixel from the polarization camera, and construct the light intensity expression of the four-phase image using the four-step phase-shifting method I 1、 I 2、 I 3 and I 4, where I 1、 I 2、 I 3 and I The phase offsets of 4 are 0, π / 2, π, and 3π / 2 respectively; According to the light intensity expression of the four-phase image I 1、 I 2、 I 3 and I 4, solve the truncated phase of each pixel ; According to the truncated phase Further solve to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured.

[0010] Preferably, solve the truncated phase according to the following formula : .

[0011] Preferably, perform an unwrapping operation on the truncated phase of each pixel to obtain a continuous phase distribution , where is the horizontal and vertical coordinates of the pixel; Solve the two-dimensional velocity field spatial distribution information of the surface to be measured according to the following formula:

[0012] where represents the velocity at position ; is the laser wavelength; is the delay time caused by interference.

[0013] Preferably, the light intensity expression of the four-phase image I 1、 I 2、 I 3 and I 4 is expressed as:

[0014]

[0015]

[0016]

[0017] Among them, is the background light intensity; is the modulation depth.

[0018] Preferably, the background light intensity is calculated according to the following formula :

[0019] The modulation depth is calculated according to the following formula :

[0020] According to the background light intensity noise information is extracted, and according to the modulation depth the intensity distribution information of the surface to be measured itself is obtained.

[0021] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: The present invention provides a two-dimensional shock wave velocity measurement system and data processing method based on polarization interference. Based on the principle of polarization interference, multi-step phase shift is adopted, and a polarization camera is used for recording, so that a two-dimensional interference image of the surface to be measured can be obtained. Combining the corresponding data processing method, the spatial distribution information of the two-dimensional velocity field can be obtained; Compared with the prior art, the present invention has the following advantages: 1) Breaking through the limitation of one-dimensional measurement: By setting two sets of quarter-wave plates with orthogonal fast axes, the linearly polarized light is respectively converted into left-handed / right-handed circularly polarized light with opposite rotation directions. After beam combination interference, an interference field carrying two-dimensional phase information is formed, fundamentally solving the problem that the traditional linear VISAR cannot obtain the spatial distribution of the two-dimensional velocity field; 2) High-efficiency acquisition by single exposure: The present invention can synchronously capture four interference images with a phase difference of exactly π / 2 by single exposure, completely avoiding the timing error caused by multiple exposures in the time-division phase shift method, and significantly improving the time resolution and spatial synchronization of transient shock wave measurement; 3) Simplified and reliable system structure: The present invention only needs conventional polarizers, wave plates and beam splitters to form the core optical path, without complex mechanical phase shifters or multiple laser pulse triggers, greatly reducing the complexity of optical path debugging and system cost, while improving the anti-interference ability.

[0022] 4) Precise and efficient data processing: The present invention is based on the four-step phase shift algorithm. By solving the truncated phase of each pixel and combining the unwrapping operation, the continuous phase distribution can be quickly reconstructed and finally converted into a two-dimensional velocity field, with high calculation accuracy.

[0023] 5) Outstanding application value: The present invention is particularly applicable to the diagnosis of shock wave symmetry in laser inertial confinement fusion (ICF). By analyzing the non-uniformity of the two-dimensional velocity field, the hydrodynamic instability can be quantified, providing irreplaceable technical support for high energy density physics research. Description of the Drawings

[0024] Figure 1 It is a structural diagram of a two-dimensional shock wave velocity measurement system based on polarization interference provided in Embodiment 1.

[0025] Figure 2 It is a flowchart of a data processing method provided in Embodiment 2. Detailed Embodiments

[0026] The drawings are only for illustrative purposes and should not be construed as limitations on this application; To better illustrate this embodiment, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0027] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0028] Embodiment 1 As Figure 1 shown, this embodiment provides a two-dimensional shock wave velocity measurement system based on polarization interference, including: a laser, a polarizer, a beam splitter BS1, a light receiving module, a beam splitter BS2, a beam splitter BS3, a reflector M1, a reflector M2, a first quarter-wave plate, a second quarter-wave plate, a polarization camera and a data processing module; The detection light emitted by the laser sequentially passes through the polarizer and the beam splitter BS1 and then enters the light receiving module, and then converges on the surface to be measured and returns to the beam splitter BS1 after being reflected by the surface to be measured; the beam splitter BS1 injects the reflected light into the beam splitter BS2; After the reflected light is split by the beam splitter BS2, a first split light and a second split light are obtained; the first split light sequentially passes through the first quarter-wave plate and the reflector M1 and then enters the beam splitter BS3; the second split light sequentially passes through the reflector M2 and the second quarter-wave plate and then enters the beam splitter BS3; The fast axis directions of the first quarter-wave plate and the second quarter-wave plate are perpendicular to each other, and the two beams of light entering the beam splitter BS3 are two beams of circularly polarized light with opposite rotation directions; The two beams of light entering the beam splitter BS3 are combined and interfere and then enter the polarization camera to obtain a two-dimensional interference image of the surface to be measured; the two-dimensional interference image of the surface to be measured includes phases that differ by 90 in sequence° Four-phase image; The data processing module is electrically connected to the polarization camera, and is configured to receive the two-dimensional interference image of the surface to be measured and perform data processing to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured; The detection light emitted by the laser is polarized into 0 ° linear polarized light after passing through the polarizer; The first split light becomes left-handed circularly polarized light after passing through the first quarter-wave plate; The second split light becomes right-handed circularly polarized light after passing through the second quarter-wave plate; A polarizer array is arranged in front of the photosensitive surface of the polarization camera. The polarizer array is composed of repeated 2×2 grid units. Each grid unit contains polarizing directions of 0 ° 、45 ° 、90 ° and 135 ° Four micro-polarizers; each micro-polarizer corresponds to a pixel on the photosensitive surface, and each pixel records an interference image of a single polarization direction; The light receiving module includes at least one lens. In this embodiment, the light receiving module includes lenses L1 and L2 arranged in sequence.

[0029] In the specific implementation process, the detection light emitted from the laser is polarized into 0 ° linear polarized light after passing through the polarizer, then enters the light receiving module after passing through the beam splitter BS1 and is focused on the surface to be measured. The detection light is reflected by the surface to be measured and returns along the original optical path, and enters the interferometer after being reflected by BS1; In this embodiment, the interferometer is composed of beam splitters BS2, BS3 and mirrors M1, M2. The reflected light enters the two arms of the interferometer through the beam splitter BS2. A first quarter-wave plate is arranged in one arm, and the polarized light in this branch is made into left-handed (or right-handed) circularly polarized light by precisely adjusting the optical axis; at the same time, a second quarter-wave plate is arranged in the other arm, and the polarized light in this branch is made into right-handed (or left-handed) circularly polarized light by precise adjustment. The core here is to make the rotation directions of the circularly polarized lights in the two arms opposite; The light in the two arms is combined after passing through the beam splitter BS3 and interferes, and then enters the final polarization camera for recording; A polarizer array (as Figure 1 shown) is arranged in front of the photosensitive surface of the polarization camera. Every 4 micro-polarizers form a grid unit, which is distributed in a 2×2 pattern, and the polarization angles are 0°, 45°, 90° and 135° in sequence. Each micro-polarizer corresponds to a pixel on the photosensitive surface; After the interference light formed by left-handed (or right-handed) circularly polarized light and right-handed (or left-handed) circularly polarized light passes through a polarization camera, a four-phase image with a phase difference of 90° in sequence can be obtained through a single exposure. The specific mathematical derivation and theoretical verification process are as follows: Assume the original linearly polarized light is x Directional polarization:

[0030] Among them, represents the light field of the reflected light incident on the interferometer; represents the light field of the probe light; represents the unit vector in the x direction (horizontal direction); In this embodiment, taking the two beams of light separated by the beam splitter BS2 as left-handed circularly polarized light and right-handed circularly polarized light respectively as an example for illustration: The first split light passes through the first quarter-wave plate with the fast axis in the y direction to obtain LCP; The second split light passes through the second quarter-wave plate with the fast axis in the x direction to obtain RCP; If the circularly polarized light is expressed in the form of a complex vector, the light field of the left-handed circularly polarized light (LCP) is expressed as:

[0031] Among them, represents the light field of the left-handed circularly polarized light; represents the unit vector in the y direction (vertical direction); i is the imaginary unit; k is the wave number, representing the number of wave cycles per unit distance; z is the propagation direction coordinate (the light propagates along the z direction); is the angular frequency, representing the number of wave cycles per unit time; t represents time; The light field of the right-handed circularly polarized light (RCP) is expressed as:

[0032] Among them, is the light field of the right-handed circularly polarized light; is the initial phase difference between the two beams of light; Considering the interference and adding a linear polarizer with an angle of θ after the interference, the derivation of the light field after interference is as follows: Superpose the two beams of light:

[0033] Among them, is the superposed light field; Expand the second term:

[0034] So the total field is:

[0035] After passing through a linear polarizer with an angle of θ, assuming the transmission axis direction of the linear polarizer is , its effect on the electric field can be represented by a projection operator: Let the polarization of the total electric field in the x-y plane be:

[0036] where represents the component of the total electric field in the x direction (complex amplitude); represents the component of the total electric field in the y direction (complex amplitude); Then the light field after passing through the polarizer is the projection of the original electric field in this direction: Let:

[0037] So:

[0038] where represents the output electric field after passing through the polarizer (i.e., the projected electric field); This embodiment focuses on the interference intensity, that is:

[0039] where represents the interference light intensity finally captured by the polarization camera, which is a function of the angle and the phase difference ; Next, calculate the light intensity: Let:

[0040] where is a custom parameter. For the convenience of simplifying the formula, this formula refers to the projection expression of the total electric field in the direction of the polarizer; Calculate the modulus square :

[0041] where represents 's conjugate; First write the conjugate:

[0042] Get:

[0043] Simplify each term:

[0044]

[0045] The cross term is zero (because it is the multiplication of the imaginary part and the real part, and the imaginary part cancels out after multiplication); So:

[0046] After arrangement, we get:

[0047] Using the identity , and noting that , then:

[0048] Therefore, when the rotation angle of the polarizer is θ, the phase of the interference fringes will shift by 2θ. So, using a polarization camera, four-phase images with a phase difference of 90° in sequence can be obtained at one time; Finally, the two-dimensional interference image of the surface to be measured obtained by the polarization camera is input into the data processing module for data processing to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured; This system obtains left-handed polarized light and right-handed polarized light by respectively setting quarter-wave plates in two arms of the interferometer and synthesizes the interference. Using a polarization camera, four-phase images with a phase difference of 90 ° can be obtained through a single exposure, and the velocity field information can be further solved; the overall structure of this system is simple and easy to adjust, and it can be realized by using simple polarizers and wave plates, laying a good technical foundation for the two-dimensional shock wave velocity diagnosis.

[0049] Embodiment 2 As Figure 2 shown, this embodiment provides a data processing method, which is applied to the data processing module based on the two-dimensional shock wave velocity measurement system based on polarization interference described in Embodiment 1, and includes the following steps: S1: Obtain the two-dimensional interference image of the surface to be measured and the light intensity of each pixel from the polarization camera, and construct the light intensity expression of the four-phase image by using the four-step phase-shifting method I 1. I 2. I 3 and I 4, where I 1. I 2. I 3 and I 4 have phase offsets of 0, π / 2, π, and 3π / 2 respectively; S2: According to the light intensity expression of the four-phase image I 1.I 2、 I 3 and I 4 to solve the truncated phase of each pixel ; S3: Further solve to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured according to the truncated phase ; Specifically, solve the truncated phase according to the following formula :

[0050] Perform an unwrapping operation on the truncated phase of each pixel to obtain a continuous phase distribution , where are the horizontal and vertical coordinates of the pixel; Solve the two-dimensional velocity field spatial distribution information of the surface to be measured according to the following formula:

[0051] where represents the velocity at the position ; is the laser wavelength; is the delay time caused by interference; In this embodiment, the light intensity expression of the four-phase image I 1、 I 2、 I 3 and I 4 is expressed as:

[0052]

[0053]

[0054]

[0055] where is the background light intensity; is the modulation degree; Calculate the background light intensity according to the following formula :

[0056] Calculate the modulation degree according to the following formula :

[0057] Extract the noise information according to the background light intensity , and extract the noise information according to the modulation degree ​Obtain the intensity distribution information of the surface to be measured itself.

[0058] In the specific implementation process, after obtaining the four-phase interference image using a polarization camera, it is necessary to further process the image data. In this embodiment, the four-step phase-shifting method is adopted, and the process is as follows: A certain point on the fringe image The corresponding fringe light intensity can be written as the following formula:

[0059] Where: I(x, y, t) is the light intensity of the fringe image at the at the t-th step of phase shift; A(x, y) represents the background light intensity (i.e., the average light intensity) at the ; B(x, y) represents the modulation degree (i.e., the fringe contrast) at the ; is the unknown truncated phase at the

[0060] Therefore, the expressions of the four images are as follows:

[0061] Use trigonometric function formulas for substitution:

[0062] Substitute into the above formula to get:

[0063] Next, use I 1, I 2, I 3 and I 4 to solve for the background light intensity , the modulation degree and the truncated phase : 1) Solve for the background light intensity : Add the four equations:

[0064] All terms containing cancel each other out, leaving:

[0065] Solve for the background light intensity :

[0066] 2) Solve the modulation degree : Construct two difference terms:

[0067] Then there is:

[0068] Square and add these two expressions:

[0069] So the modulation degree can be obtained :

[0070] 3) Solve the truncated phase : From it can be known that:

[0071] Use the arctangent function to represent the phase:

[0072] Therefore,

[0073] The noise information can be extracted from the background light intensity, the intensity distribution information of the target surface itself can be obtained from the modulation degree, and the distribution information of the two-dimensional velocity field can be obtained from the truncated phase; Specifically, for the truncated phase of each pixel perform the unwrapping operation to obtain the continuous phase distribution , where are the horizontal and vertical coordinates of the pixel; Solve the spatial distribution information of the two-dimensional velocity field of the surface to be measured according to the following formula:

[0074] where represents the velocity at the position ; is the laser wavelength; is the delay time caused by interference; This embodiment is based on the four-step phase-shifting algorithm. By solving the truncated phase of each pixel and combining the unwrapping operation, the continuous phase distribution can be quickly reconstructed and finally converted into a two-dimensional velocity field, with high calculation accuracy; In addition, based on the extracted noise information, denoising can be further performed to improve the signal-to-noise ratio of the image; based on the extracted intensity distribution information of the surface to be measured itself, the uneven intensity distribution of the two-dimensional surface to be measured at different spatial positions can be obtained; since the surface to be measured is not an ideal smooth plane, there will be other traces such as scratches and defects during the processing, or marks deliberately set on the surface to be measured in experimental studies. These information can be obtained by calculating the modulation degree B.

[0075] The same or similar reference numerals correspond to the same or similar components; The terms used to describe the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to this application; Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A two-dimensional shock wave velocity measurement system based on polarization interference, characterized in that, Including: A laser, a polarizer, a beam splitter BS1, a beam splitter BS2, a beam splitter BS3, a reflector M1, a reflector M2, a first quarter-wave plate, a second quarter-wave plate, a polarization camera, and a data processing module; The detection light emitted by the laser sequentially passes through the polarizer and the beam splitter BS1 and then is incident on the surface to be measured, and after being reflected by the surface to be measured, returns to the beam splitter BS1; the beam splitter BS1 injects the reflected light into the beam splitter BS2; After the reflected light is split by the beam splitter BS2, a first split light and a second split light are obtained; the first split light sequentially passes through the first quarter-wave plate and the reflector M1 and then is injected into the beam splitter BS3; the second split light sequentially passes through the reflector M2 and the second quarter-wave plate and then is injected into the beam splitter BS3; The fast axis directions of the first quarter-wave plate and the second quarter-wave plate are perpendicular to each other, and the two beams of light injected into the beam splitter BS3 are two beams of circularly polarized light with opposite rotation directions; The two light beams incident on the beam splitter BS3 are combined and interfere, and then are incident on the polarization camera to obtain a two-dimensional interference image of the surface to be measured; the two-dimensional interference image of the surface to be measured includes four-phase images with phases differing by 90 ° in sequence; The data processing module is electrically connected to the polarization camera and is used for receiving the two-dimensional interference image of the surface to be measured and performing data processing to obtain the two-dimensional velocity field spatial distribution information of the surface to be measured.

2. The two-dimensional shock wave velocity measurement system based on polarization interference according to claim 1, wherein The detection light emitted by the laser is polarized to 0 after passing through the polarizer ° linear polarized light; The first split light becomes left-handed circularly polarized light after passing through the first quarter-wave plate; The second split light becomes right-handed circularly polarized light after passing through the second quarter-wave plate.

3. A two-dimensional shock wave velocity measurement system based on polarization interference according to claim 1, characterized in that, A polarizer array is provided in front of the photosensitive surface of the polarization camera. The polarizer array is composed of repeated 2×2 square grid units, and each ° square grid unit contains four micropolarizers with polarization directions of 0 ° , 45 ° , 90 ° and 135 in sequence; each micropolarizer corresponds to a pixel on the photosensitive surface, and each pixel records an interference image with a single polarization direction.

4. A two-dimensional shock wave velocity measurement system based on polarization interference according to any one of claims 1 to 3, characterized in that The system further includes a light receiving module, and the detection light emitted by the laser sequentially passes through the polarizer and the beam splitter BS1 and then is incident on the light receiving module and then converges on the surface to be measured; The light receiving module includes at least one lens.

5. A data processing method, which is applied to the data processing module based on the two-dimensional shock wave velocity measurement system based on polarization interference described in any one of claims 1 to 4, and is characterized in that, Including the following steps: Obtain the two-dimensional interference image of the surface to be measured and the light intensity of each pixel from the polarization camera, and construct the light intensity expression of the four-phase image by using the four-step phase-shifting method I 1、 I 2、 I 3 and I 4, where I 1、 I 2、 I 3 and I the phase offsets of 1, 2, 3, and 4 are 0, π / 2, π, and 3π / 2 respectively; According to the light intensity expression of the four-phase image I 1、 I 2、 I 3 and I 4, solve the truncated phase of each pixel ; According to the truncated phase The spatial distribution information of the two-dimensional velocity field of the surface to be measured is further obtained by solving.

6. A data processing method according to claim 5, characterized in that, Solve the truncated phase according to the following formula :[[-END]] 。 7. A data processing method according to claim 5, characterized in that Truncated phase of each pixel Perform an unwrapping operation to obtain a continuous phase distribution , where are the horizontal and vertical coordinates of the pixel; Solving the two-dimensional velocity field spatial distribution information of the surface to be measured according to the following formula: Among them, represents the velocity at the position ; is the laser wavelength; is the delay time caused by interference.

8. A data processing method according to claim 5, wherein The light intensity expression of the four-phase image I 1、 I 2、 I 3 and I 4 are expressed as: Among them, is the background light intensity; is the modulation depth.

9. A data processing method according to claim 8, characterized in that Calculate the background light intensity according to the following formula : Calculate the modulation degree according to the following formula :[[]]END]] According to the background light intensity Extract noise information, and according to the modulation degree Obtain the intensity distribution information of the surface to be measured itself.

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