Inclined wave surface infrared interference detection method of double-optical-fiber interference arm

Abstract

The invention discloses an inclined wave surface infrared interference detection method of double optical fiber interference arms, and relates to the field of optical precision measurement. Light emitted by the wavelength tunable laser is divided into two light beams through the coupler, one light beam is directly output by the polarization maintaining optical fiber to serve as reference light, the other light beam enters the optical fiber array to output a plurality of standard spherical waves with different inclination angles to serve as test light, the surface gradients of different areas of a measured surface are compensated, and therefore the interference fringe density is reduced. The reference arm and the test arm of the system both adopt optical fibers as ideal point source generators, control point source on-off can be controlled, and system errors caused by lens use are reduced. The light emitted by the optical fiber of the test arm is all used as test light, the utilization rate of a point source is improved, the aperture of a detected surface is increased, surface shape detection can be realized without moving an interference device, and errors caused by mechanical movement are reduced. The system adopts infrared light as a measurement light beam, so that the dynamic measurement range is enlarged, and the detection of large-aperture elements with more gradient changes can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical precision measurement, and particularly relates to an infrared interference detection method for an inclined wavefront with a double-fiber interference arm. Background Art

[0002] Aspherical optical elements have higher design freedom compared to spherical optical elements. They can significantly improve the performance of optical systems while meeting the requirements of compactness, miniaturization, and lightweight of modern optical systems. Therefore, they have received increasing attention in fields such as automotive and aerospace. However, high-precision aspherical processing relies on high-precision surface shape detection technology. Due to the large surface gradient change, high surface shape freedom, and non-rotation symmetry of aspherical surfaces, it increases the difficulty in high-precision processing and precision detection.

[0003] The inclined wavefront method introduces multiple off-axis interference sources to generate multiple spherical waves with different inclination angles to compensate for the gradients of each local area of the surface to be measured, avoiding the introduction of positioning errors and motion errors and achieving high-precision aspherical surface shape measurement. CN103759668B discloses an "Inclined Wavefront Interference System Based on a Fiber Array Type Spatial Point Source Array Generator". The system uses a fiber array instead of a lens array to emit spherical waves with better quality, and the divergence angle of the emitted spherical waves can be controlled. The emitted light of each fiber in the fiber array is introduced by the fiber one by one, and the light energy utilization efficiency is higher than that of the interference system using a lens array. At the same time, the on-off of each fiber can be controlled separately, and there is no need to use a mask plate to control the selection of point sources. However, to measure aspherical elements with a large aperture and gradient, it is necessary to design a collimating lens group and a spherical lens group with a larger aperture, which is difficult.

[0004] CN108362222B discloses a "Novel Non-Null Point Diffraction Interference Measurement System Based on Multi-Directional Inclined Carrier Frequency", which uses a fiber array to form a point diffraction array to generate a wavefront with multi-directional inclined carrier frequency to compensate for the surface gradient of the measured part and measure the surface shape of the aspherical element. However, since a part of the on-axis point source on its fiber array is used as the reference light, only a part of the point source enters the surface to be measured as the test light, resulting in a low light utilization rate of the point source for measurement, and the aperture and gradient of the surface to be measured are limited. Summary of the Invention

[0005] The present invention proposes an infrared interference detection method for an inclined wavefront with a double-fiber interference arm. By using a double-fiber interference arm, it can generate detection point sources for different surface shapes of the surface to be measured by controlling the on-off of the fiber array, improve the utilization rate of the point source, reduce the use of interference lenses, and reduce the introduced wave aberration.

[0006] The technical solution to realize the present invention is: an infrared interference detection method for an inclined wavefront with a double-fiber interference arm, and the steps are as follows:

[0007] Step 1, set up the detection optical path:

[0008] The measurement optical path includes a wavelength tunable laser, a coupler, a second beam splitting prism, a first lens, a second lens, a third lens, a CCD, a PC control terminal, a test arm, and a reference arm. The wavelength tunable laser and the coupler are arranged in sequence along the first optical axis. The wavelength tunable laser and the coupler are connected by a first polarization maintaining fiber. The output end of the coupler is respectively connected to the test arm and the reference arm through two first polarization maintaining fibers.

[0009] The test arm includes a first optical switch, an optical fiber array, a first beam splitting prism, and a surface to be measured arranged in sequence along the second optical axis. The coupler is connected to the first optical switch through a first polarization maintaining fiber, and the first optical switch and the optical fiber array are connected through a first polarization maintaining fiber.

[0010] The reference arm includes a second optical switch and a second polarization maintaining fiber arranged in sequence along the third optical axis. The input end of the second optical switch is connected to the coupler through a first polarization maintaining fiber, and the output end of the second optical switch is connected to the second beam splitting prism through a second polarization maintaining fiber.

[0011] A diaphragm, a second beam splitting prism, a first lens, a second lens, a third lens, and a CCD are distributed in sequence along the fourth optical axis. The reference arm and the test arm are combined by the second beam splitting prism. The diaphragm is located on the reflected light path of the beam splitting prism; the CCD is connected to the PC control terminal.

[0012] The linearly polarized light emitted by the wavelength tunable laser is output through the first polarization maintaining fiber and then divided into two beams by the coupler. One beam is used as the reference light and enters the reference arm, and the other beam enters the test arm; the beam entering the test arm forms a test light after passing through the first optical switch and the optical fiber array in sequence. The test light is transmitted through the first beam splitting prism and then incident on the surface to be measured. The test light carrying the surface profile information of the surface to be measured returns to the first beam splitting prism and is reflected by the first beam splitting prism and enters the fourth optical axis; the test light carrying the surface profile information of the surface to be measured passes through the diaphragm, the second beam splitting prism, the first lens, the second lens, and the third lens in sequence along the fourth optical axis and is received by the CCD; the reference light is output by the second optical switch and then exits to the second beam splitting prism along the second polarization maintaining fiber, is reflected by the second beam splitting prism and enters the fourth optical axis, and then passes through the first lens, the second lens, and the third lens in sequence and is received by the CCD; the CCD acquires the sub-region interference pattern carrying the surface profile information of the surface to be measured and transmits the above sub-region interference pattern to the PC control terminal.

[0013] Step 2, divide the surface to be measured into sub-regions according to the surface profile parameters of the surface to be measured, and determine the point source position parameters and the on-off sequence required for the optical fiber array during surface profile detection according to the parameters of the divided sub-regions.

[0014] Step 3: Turn on the first optical switch on the test arm and the second optical switch on the reference arm, replace the surface under test with a standard spherical mirror, adjust the attitude of the standard spherical mirror, and calibrate the systematic error of each point source on the fiber optic array required for the surface under test.

[0015] Step 4: Remove the standard spherical mirror and place the surface under test. Turn on the wavelength-tunable laser. According to the point source positions and on-off sequences required for the surface under test obtained in Step 2, perform interference detection on the surface profile information of the surface under test.

[0016] Step 5: Adjust the change Δλ of the central wavelength λ of the wavelength-tunable laser so that its phase continuously changes by π / 2, π, 3π / 2, and 2π within a complete cycle. The CCD continuously acquires four interference patterns of each point source corresponding to the sub-region of the surface under test.

[0017] Step 6: Perform phase unwrapping on the four interference patterns collected for each sub-region of the surface under test, and correspondingly solve the wrapped phase of each sub-region.

[0018] Step 7: Perform return error correction on the wrapped phase of each sub-region through the return error correction algorithm to obtain the surface profile information of each sub-region after correcting the return error.

[0019] Step 8: Stitch the surface profile information of each sub-region after correcting the return error according to the coordinate positions of each sub-region to obtain the full-aperture corrected surface profile information of the entire surface under test. Compare the full-aperture corrected surface profile information with the surface profile parameters of the surface under test to complete the detection of the surface profile error of the surface under test.

[0020] Compared with the prior art, the remarkable advantages of the present invention are as follows:

[0021] (1) In the present invention, both the reference arm and the test arm use optical fibers as ideal point source generators to generate nearly ideal point-diffraction spherical waves. In this way, there is no need to add a standard compensating spherical lens group in the optical path, avoiding a large number of wavefront aberrations introduced by the standard compensating spherical lens group. At the same time, the utilization rate of point sources is improved, the measurement aperture size of the interference system is increased, and surface shape detection can be achieved without moving the interference device, reducing the errors introduced by mechanical movement.

[0022] (2) The present invention uses infrared light as the measurement beam to improve the dynamic measurement range of the entire system and can meet the detection of large-aperture components with more gradient changes. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the infrared interference detection optical path of the tilted wavefront of the double-fiber interference arms described in the present invention.

[0024] Figure 2 It is a flowchart of a method for infrared interference detection of the tilted wavefront of a double-fiber interference arm described in the present invention.

[0025] In the figure: wavelength tunable laser 1, first polarization maintaining optical fiber 2, coupler 3, first optical switch 4, fiber array 5, first beam splitting prism 6, surface to be measured 7, diaphragm 8, second optical switch 9, second polarization maintaining optical fiber 10, second beam splitting prism 11, first lens 12, second lens 13, third lens 14, CCD 15, PC control terminal 16. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0028] In addition, in the present invention, the descriptions such as "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0029] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. shall be understood in a broad sense. For example, "fixation" may be a fixed connection, a detachable connection, or integrated; "connection" may be a mechanical connection or an electrical connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0030] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0031] Next, the detailed implementation manners, as well as the technical difficulties and inventive points of the present invention, will be further introduced in combination with this design example.

[0032] Combined with Figure 2 , for the infrared interference detection method with an inclined wavefront of a double-fiber interference arm described in the present invention, the steps are as follows:

[0033] Step 1: Combine Figure 1 to set up a measurement optical path:

[0034] The measurement optical path includes a wavelength tunable laser 1, a coupler 3, a second beam splitting prism 11, a first lens 12, a second lens 13, a third lens 14, a CCD 15, a PC control terminal 16, a test arm, and a reference arm. Along the first optical axis, the wavelength tunable laser 1 and the coupler 3 are arranged in sequence. The wavelength tunable laser 1 and the coupler 3 are connected by a first polarization maintaining fiber 2. The output end of the coupler 3 is respectively connected to the test arm and the reference arm through two first polarization maintaining fibers 2. There is also a second optical axis parallel to the first optical axis, along which a first optical switch 4, an optical fiber array 5, a first beam splitting prism 6, and a surface to be measured 7 are distributed in sequence. The coupler 3 and the first optical switch 4 are connected by a first polarization maintaining fiber 2, and the first optical switch 4 and the optical fiber array 5 are connected by a first polarization maintaining fiber 2. There is also a third optical axis parallel to the second optical axis, along which a second optical switch 9 and a second polarization maintaining fiber 10 are distributed in sequence. The input end of the second optical switch 9 is connected to the coupler 3 by a first polarization maintaining fiber 2, and the output end of the second optical switch 9 is connected to the second beam splitting prism 11 by a second polarization maintaining fiber 10. There is also a fourth optical axis perpendicular to the third optical axis, along which a diaphragm 8, the second beam splitting prism 11, the first lens 12, the second lens 13, the third lens 14, and the CCD 15 are distributed in sequence. The reference arm and the test arm are combined by the second beam splitting prism 11, and the diaphragm 8 is located on the reflection optical path of the beam splitting prism 6. The CCD 15 is connected to the PC control terminal 16.

[0035] The outgoing direction of the wavelength tunable laser 1 is the first optical axis; the polarization direction of the linearly polarized light emitted by the wavelength tunable laser 1 is consistent with the working optical axes of the first polarization maintaining fiber 2, the coupler 3, the first optical switch 4, the optical fiber array 5, the second optical switch 9, and the second polarization maintaining fiber 10. The linearly polarized light output by the wavelength tunable laser 1 is output to the coupler 3 by the first polarization maintaining fiber 2 and is divided into two beams of light. One beam is used as the reference light and enters the reference arm, and the other beam enters the test arm. The beam entering the test arm is transmitted by the first polarization maintaining fiber 2 to the optical switch 4 and the optical fiber array 5, and a standard spherical wave with different tilts parallel to the first optical axis is emitted from the optical fiber array 5 to form a test light.

[0036] The test beam of the test arm exits from the fiber optic array 5 on the second optical axis and enters the first beam splitter prism 6. After passing through the first beam splitter prism 6, it is incident on the surface to be measured 7 to detect the surface profile of different regions of the surface to be measured. After carrying the surface profile information of the surface to be measured 7, it returns to the first beam splitter prism 6. The position of the fiber optic array 5 is based on the center point source of the end face of the fiber optic array 5, and its light output direction is consistent with the second optical axis. Moreover, the position of the first beam splitter prism 6 and the fiber optic array 5 satisfies that the light emitted from the outermost point source of the fiber optic array can completely pass through the beam splitter prism. The test beam carrying the surface profile information of the surface to be measured 7 returns to the first beam splitter prism 6. After being reflected by the first beam splitter prism 6, it enters the fourth optical axis. After the stray light is filtered by the aperture 8 on the fourth optical axis, it passes through the second beam splitter prism 11. The spatial position of the center of the aperture 8 and the center of the end face of the fiber optic array 5 is symmetric about the first beam splitter prism 6. The beam transmitted through the second beam splitter prism 11 passes through the first lens 12, the second lens 13, and the third lens 14 in sequence and is received by the CCD 15.

[0037] The reference beam of the reference arm is output from the second optical switch 9 and then exits to the second beam splitter prism 11 along the second polarization-maintaining fiber 10. After being reflected by the second beam splitter prism 11, it enters the fourth optical axis. The spatial position of the center of the end face of the second polarization-maintaining fiber 10 and the center of the aperture 8 is symmetric about the second beam splitter prism 11. After the reference beam is reflected by the second beam splitter prism 11, it passes through the first lens 12, the second lens 13, and the third lens 14 in sequence and is received by the CCD 15.

[0038] The 4f system composed of the second lens 13 and the third lens 14 converges the beam collimated by the first lens 12 and simultaneously images the interference pattern onto the CCD 15.

[0039] The wavelength tunable laser 1 can achieve continuous phase changes of π / 2, π, 3π / 2, and 2π within a complete cycle by controlling the tunable amount of the center wavelength λ.

[0040] Step 2: According to the surface profile parameters of the surface to be measured 7, divide the surface to be measured 7 into sub-regions, and determine the required point source position parameters and on-off sequence of the fiber optic array 5 during surface profile detection based on the parameters of the divided sub-regions.

[0041] Calculate the point source parameters required for detecting the surface profile of the surface to be measured 7 through the point source array generation calculation model:

[0042] Calculate the range O r of the radius r where the test light is allowed to deviate from the reference light according to the CCD pixel size p and the focal length f of the first lens 12:

[0043]

[0044] According to the calculated O rCalculate the measurable point source range Q corresponding to each point on the surface to be measured based on the range, the position (x, y, z) of each point on the surface to be measured, and the normal direction corresponding to each point, and calculate its centroid. Calculate the point source position through the point source screening method: r , and calculate its centroid. Calculate the point source position through the point source screening method:

[0045] ① Count the number of data points on the measured part that can be measured by all point sources, and mark the one with the most measured data points as H1;

[0046] ② Remove the point source H1 and its measurable data points;

[0047] ③ Repeat steps ① to ② for the unmarked point sources until all data points are marked.

[0048] Finally, determine the on-off sequence of the point sources by calculating the position of the interference pattern of each point source measurement area on the CCD through ray tracing.

[0049] Step 3: Turn on the first optical switch 4 on the test arm and the second optical switch 10 on the reference arm, replace the surface to be measured 7 with a standard spherical mirror, adjust the attitude of the standard spherical mirror, and calibrate the systematic error of each point source on the fiber optic array 5 required for the surface to be measured 7.

[0050] Step 4: Remove the standard spherical mirror, place the surface to be measured 7, turn on the wavelength tunable laser 1, and perform interference detection on the surface shape information of the surface to be measured 7 according to the point source positions and on-off orders required for measuring the surface to be measured 7 calculated in step 2.

[0051] Step 5: Adjust the wavelength λ (central wavelength) of the wavelength tunable laser 1 to change by Δλ, so that its phase continuously changes by π / 2, π, 3π / 2, 2π within a complete cycle, and the CCD 15 continuously acquires four interference patterns of each sub-region of the surface to be measured 7 corresponding to each point source.

[0052] Step 6: Unwrap the four interference patterns collected for each sub-region of the surface to be measured 7, and correspondingly solve the wrapped phase of each sub-region.

[0053] Step 7: Perform return error correction on the wrapped phase of each sub-region through the return error correction algorithm to obtain the surface shape information of each sub-region after correcting the return error.

[0054] Use ZEMAX to build an ideal detection optical path, simulate an ideal detection surface with a surface shape error, set its surface shape parameter as W s ′, as the ideal detection input, generate four interference patterns of each sub-region, and perform unwrapping to obtain the wrapped phase of the sub-region as W t ′; Set the surface shape parameter of the surface to be measured 7 in the measurement optical path as W s , perform unwrapping processing on the four interference patterns of each sub-region of the surface to be measured 7, and obtain the wrapped phase of the sub-region as Wt , which is expressed by the following formula:

[0055]

[0056] where A j 、A j ′, B j 、B j ′ are all polynomial coefficients for representing W s 、W s ′, W t 、W t ′ using Zernike polynomials, Z j is a polynomial matrix, and N is the number of polynomial terms. Taking the Zernike coefficient B t of the actual reconstructed wavefront W j of the detection system as the optimization objective, setting the coefficient A s ′ of the ideal surface shape error W j ′ of the surface to be measured as the optimization variable, and performing iterative optimization on A ′ according to the objective function j until the difference between W t and W t ′ is less than the threshold ε (ε is taken as λ / 20), then the optimal solution A j ′ of the aspherical surface shape coefficient can be obtained.

[0057] The objective function is defined as:

[0058]

[0059] where, is the optimization weight.

[0060] Step 8: Stitch and correct the surface shape information of each sub-region after the return error according to the coordinate positions of each sub-region to obtain the full-aperture corrected surface shape information of the entire surface to be measured 7. Compare the full-aperture corrected surface shape information with the surface shape parameters of the surface to be measured 7 to complete the detection of the surface shape error of the surface to be measured.

Claims

1. An infrared interference detection method with an inclined wavefront for a double-fiber interference arm, characterized in that, The steps are as follows: Step 1: Set up the detection optical path: The measurement optical path includes a wavelength tunable laser (1), a coupler (3), a second beam splitting prism (11), a first lens (12), a second lens (13), a third lens (14), a CCD (15), a PC control terminal (16), a test arm, and a reference arm. The wavelength tunable laser (1) and the coupler (3) are sequentially arranged along the first optical axis. The wavelength tunable laser (1) and the coupler (3) are connected by a first polarization maintaining fiber (2). The output end of the coupler (3) is respectively connected to the test arm and the reference arm through two first polarization maintaining fibers (2); The test arm includes a first optical switch (4), an optical fiber array (5), a first beam splitting prism (6), and a surface to be measured (7) sequentially arranged along the second optical axis. The coupler (3) and the first optical switch (4) are connected by a first polarization maintaining fiber (2). The first optical switch (4) and the optical fiber array (5) are connected by a first polarization maintaining fiber (2); The reference arm includes a second optical switch (9) and a second polarization maintaining fiber (10) sequentially arranged along the third optical axis. The input end of the second optical switch (9) is connected to the coupler (3) by a first polarization maintaining fiber (2). The output end of the second optical switch (9) is connected to the second beam splitting prism (11) by a second polarization maintaining fiber (10); A diaphragm (8), a second beam splitting prism (11), a first lens (12), a second lens (13), a third lens (14), and a CCD (15) are sequentially distributed along the fourth optical axis. The reference arm and the test arm are combined by the second beam splitting prism (11). The diaphragm (8) is located on the reflected light path of the beam splitting prism (6); The CCD (15) is connected to the PC control terminal (16); The linearly polarized light emitted by the wavelength tunable laser (1) is output through the first polarization maintaining fiber (2) and then split into two beams by the coupler (3). One beam is used as the reference light and enters the reference arm, and the other beam enters the test arm; The beam entering the test arm forms a test light after passing through the first optical switch (4) and the optical fiber array (5) in sequence. The test light is transmitted through the first beam splitting prism (6) and then incident on the surface to be measured (7). The test light carrying the surface shape information of the surface to be measured (7) returns to the first beam splitting prism (6), is reflected by the first beam splitting prism (6) and enters the fourth optical axis; The test light carrying the surface shape information of the surface to be measured (7) sequentially passes through the diaphragm (8), the second beam splitting prism (11), the first lens (12), the second lens (13), and the third lens (14) along the fourth optical axis and is received by the CCD (15); The reference light is output by the second optical switch (9) and then exits to the second beam splitting prism (11) along the second polarization maintaining fiber (10), is reflected by the second beam splitting prism (11) and enters the fourth optical axis, and then sequentially passes through the first lens (12), the second lens (13), and the third lens (14) and is received by the CCD (15); The CCD (15) acquires the sub-region interference pattern carrying the surface shape information of the surface to be measured (7) and transmits the above sub-region interference pattern to the PC control terminal (16); Step 2: According to the surface parameters of the surface to be measured (7), divide the surface to be measured (7) into sub-regions, and determine the point source position parameters and on-off sequence required for the fiber optic array (5) during surface shape detection based on the parameters of the divided sub-regions; Step 3: Open the first optical switch (4) on the test arm and the second optical switch (10) on the reference arm, replace the surface to be measured (7) with a standard spherical mirror, adjust the attitude of the standard spherical mirror, and calibrate the systematic error of each point source on the fiber optic array (5) required for the surface to be measured; Step 4: Remove the standard spherical mirror and place the surface to be measured (7) in. Turn on the wavelength tunable laser (1), and perform interference detection on the surface shape information of the surface to be measured (7) according to the point source positions and on-off sequence required for the surface to be measured (7) obtained in Step 2; Step 5: Adjust the change Δλ of the central wavelength λ of the wavelength tunable laser (1) so that its phase continuously changes by π / 2, π, 3π / 2, 2π within a complete cycle, and the CCD (15) continuously collects four interference patterns of each sub-region of the surface to be measured (7) corresponding to each point source; Step 6: Perform phase unwrapping on the four interference patterns collected for each sub-region of the surface to be measured (7), and correspondingly solve the wrapped phase of each sub-region; Step 7: Perform return error correction on the wrapped phase of each sub-region through the return error correction algorithm to obtain the surface shape information of each sub-region after correcting the return error; Step 8: Stitch the surface shape information of each sub-region after correcting the return error according to the coordinate positions of each sub-region to obtain the full-aperture corrected surface shape information of the entire surface to be measured (7), and compare the full-aperture corrected surface shape information with the surface parameters of the surface to be measured (7) to complete the detection of the surface shape error of the surface to be measured.

2. The tilt wavefront infrared interference detection method for a dual-fiber interference arm according to claim 1, characterized in that, In Step 1, the linearly polarized light emitted by the wavelength tunable laser (1) is split into two beams by the coupler (3). One beam enters the reference arm and is output by the second polarization-maintaining fiber (10), and the other beam enters the test arm and is output by the fiber optic array (5); the spatial position between the center of the end face of the fiber optic array (5) and the center of the aperture stop (8) is symmetric about the first beam splitter prism (6); the spatial position between the center of the fiber end face of the second polarization-maintaining fiber (10) and the center of the aperture stop (8) is symmetric about the second beam splitter prism (11).

3. A tilt wavefront infrared interference detection method for a dual-fiber interference arm as described in claim 1, characterized in that In Step 1, the first optical axis is parallel to the second optical axis, the second optical axis is parallel to the third optical axis, and the third optical axis is perpendicular to the fourth optical axis.

4. A tilt wavefront infrared interference detection method for a dual-fiber interference arm according to claim 1, characterized in that In Step 2, use the reverse ray tracing and point source screening algorithm to determine the point source position parameters and on-off sequence required for the fiber optic array (5) during surface shape detection based on the parameters of the sub-regions divided for the surface to be measured (7).

5. A tilt wavefront infrared interference detection method for a dual-fiber interference arm according to claim 1, characterized in that In Step 7, perform return error correction on the wrapped phase of each sub-region through the return error correction algorithm to obtain the surface shape information of each sub-region after correcting the return error, specifically as follows: The simulation gives an ideal detection surface with surface shape errors, and its surface shape parameter is set as W s ′. As the ideal detection input, four interference patterns of each sub-region are generated, and the wrapped phase of the sub-region is obtained by unwrapping, which is W t ′; Let the surface shape parameter of the surface under test (7) in the measurement optical path be W s . The four interference patterns of each sub-region of the surface under test (7) are unwrapped to obtain the wrapped phase of the sub-region, which is W t . Calculate the deviation between W t ′ and W t . By continuously iterating to change W s ′ until the deviation between W t ′ and W t is less than λ / 20, the surface shape information of each sub-region of the surface under test (7) after correcting the return error is finally obtained.

6. The tilt wavefront infrared interference detection method for a double-fiber interference arm according to claim 1, characterized in that In Step 8, stitch the surface shape information of each sub-region after correcting the return error according to the coordinate positions of each sub-region to obtain the full-aperture corrected surface shape information of the entire surface to be measured (7), specifically as follows: Calculate the coordinate positions of the surface shape information of each sub-region after correcting the return error in the full-aperture surface shape information, and stitch the surface shape information of each sub-region after correcting the return error according to the coordinate positions.

7. The tilt wavefront infrared interference detection method for a double fiber optic interference arm according to claim 1, characterized in that, In step 1, each point source on the point source array generated by the fiber optic array (5) can cover the entire area on the surface to be measured (7).

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