阅读说明：本技术 一种光学元件表面局部陡度面形误差干涉测量方法及装置 (Optical element surface local gradient surface shape error interferometry method and device ) 是由 郝群 胡摇 石峰 宋辞 谢凌波 于 2020-07-31 设计创作，主要内容包括：一种光学元件表面局部陡度面形误差干涉测量方法及装置,在不改变原干涉仪光路的前提下实现之前不可测量的局部陡度面形误差的测量。利用双光楔补偿器,放置在在局部陡度面形误差的区域,旋转双光楔补偿器的相对转角和整体绕光轴滚转角,产生方向可调的附加倾斜补偿相位,使局部测量光束与局部面形匹配,干涉条纹变稀疏,利用干涉仪测量局部相位；根据双光楔补偿器的旋转角度计算其引入的相位,输入虚拟干涉仪模型,计算得到局部面形误差；对被光学元件所有无法直接测量的局部依次进行上述测量过程,直到所有局部陡度面形误差均完成测量；将局部面形误差与光学元件全口径面形误差数据进行拼接,完成测量。(An interference measurement method and device for local gradient surface shape error of optical element surface realizes the previous unmeasurable measurement of local gradient surface shape error on the premise of not changing the original interferometer light path. The dual-optical wedge compensator is placed in a local gradient surface shape error area, the relative rotation angle of the dual-optical wedge compensator and the integral roll angle around the optical axis are rotated to generate an additional tilt compensation phase with adjustable direction, so that a local measuring light beam is matched with a local surface shape, interference fringes are sparse, and a local phase is measured by an interferometer; calculating the introduced phase according to the rotation angle of the double-optical-wedge compensator, inputting the phase into a virtual interferometer model, and calculating to obtain a local surface shape error; sequentially carrying out the measurement process on all parts which cannot be directly measured by the optical element until all the local gradient surface shape errors are measured; and splicing the local surface shape error and the full-aperture surface shape error data of the optical element to finish measurement.)

1. An optical element surface local gradient surface shape error interferometry method is characterized in that: which comprises the following steps:

(1) the method comprises the steps that the laser interferometer host and a compensating mirror are utilized to complete measurement of the full-aperture surface shape error of a measured mirror, and the full-aperture surface shape error distribution phi (x, y) is obtained, wherein effective measurement data cannot be obtained due to too dense interference fringes in a local steepness surface shape error area, and a measurement data missing area is marked to be sigma;

(2) inserting a double-optical-wedge compensator into the optical path corresponding to the region sigma, adjusting three-dimensional coordinates (x, y, z) including axial and two orthogonal transverse positions by using a double-optical-wedge compensator adjusting frame, so that the area of the double-optical-wedge compensator can just cover the whole data missing region, and adjusting the axial position of the measured mirror according to the thickness of the double optical wedge so that the additional phase introduced by the double optical wedge is compensated;

(3) relative rotation angle of rotary double-optical wedge compensator to alpha₁To maximize the deflection of the beam it produces; the rotating double-optical-wedge compensator integrally rolls an angle beta around an optical axis, and dense interference fringe change in a data missing region sigma is observed when a region sigma in the data missing region sigma₁When the middle interference fringe is sparse and can be measured, the integral roll angle beta of the double-optical-wedge compensator around the optical axis at the moment is recorded₁The area σ at this time is measured using an interferometer₁Phase distribution of

(4) Establishing a measurement system model consisting of a laser interferometer host, a compensating mirror and a measured mirror in optical simulation software, wherein the model is based on the position (x, y, z) and the relative rotation angle alpha of the double-optical-wedge compensator₁And an overall roll angle beta about the optical axis₁Model of inserted double optical wedge compensator, using inverse iterative optimization method to obtain phase distributionFinding the region σ₁Median shape error distribution E₁(x,y)；

(5) Rotating the relative rotation angle of the double-optical wedge compensator to alpha by a certain step length delta alpha₂And (4) repeating the step (3) and recording the sigma₂、β₂、Repeating the step (4), and recording the obtained surface shape error distribution E₂(x, y); then, the relative rotation angle of the double-optical wedge compensator is rotated to alpha by taking delta alpha as step length_n＝α₁+180 °, repeat steps (3), (4) and record a series of σ_n、β_n、

(6) For full aperture surface shape error distribution phi (x, y) and each sigma_nSurface shape error distribution E of region_nAnd (x, y) splicing to obtain the full-aperture surface shape error distribution with complete data.

2. The interferometry method for surface shape error of local steepness of optical element surface according to claim 1, wherein: in the step (3), if no interference fringe is clear in Σ during one rotation of β from 0 to 360, the process jumps to the step (5).

3. The interferometry method for surface shape error of local steepness of optical element surface according to claim 2, wherein: the specific method of the reverse iterative optimization method in the step (4) is as follows: for region sigma₁Taking the minimum circumcircle as the normalized radius to phase distribution phi₁(x, y) performing Zernike fitting to obtain a fitting coefficient Z_i1The Zernike coefficient Z of the image plane phase is measured in a measurement system model_i1Set as optimization target, measured surface area σ₁Zernike coefficient Z 'of surface shape error of (1)'_1iSetting the variable as an optimized variable, and optimizing by using a damping least square method to obtain Z'_1iIntroducing Zernike polynomials to obtain surface shape error E₁(x,y)。

4. Optical element according to claim 3 having a locally steep surfaceThe interference measurement method for the surface shape error is characterized by comprising the following steps: in the step (6), firstly, the full-aperture surface shape error phi (x, y) is taken as a reference, the square sum of the difference values of the surface shape errors in the overlapped parts of all pairwise adjacent regions is taken as an optimization target, and each sigma is taken as_nSurface shape error distribution E of region_nUsing the transformation coefficient of (x, y) as an optimization variable, obtaining the transformation coefficient by utilizing least square optimization, and then using the transformation coefficient to convert phi (x, y) and E_nAnd (x, y) unifying the data in the overlapped parts under a coordinate system, and finally carrying out homogenization fusion or weighted fusion on the data in the overlapped parts to obtain complete full-aperture surface-shaped error distribution.

5. An optical element surface local gradient surface shape error interference measuring device is characterized in that: it includes: the device comprises a laser interferometer host (1), a compensating mirror (2), a double-optical-wedge compensator (3), a double-optical-wedge compensator adjusting frame (4) and a measured mirror (5);

the wavefront of a measuring beam emitted by the laser interferometer host (1) is modulated by the compensating mirror (2) and then becomes a wavefront matched with the nominal surface shape of the measured mirror (5), the wavefront enters the measured mirror (5), is reflected on the measured mirror (5), returns to the laser interferometer host (1) through the compensating mirror (2) again, and interferes with internal reference light to form interference fringes;

inserting a double-optical-wedge compensator (3) into a data missing area caused by the intensive interference fringes between the compensating mirror (2) and the measured mirror (5), and adjusting the transverse and axial positions of the double-optical-wedge compensator (3) by using a double-optical-wedge compensator adjusting frame (4) to ensure that the area of the double-optical-wedge compensator just can cover the whole data missing area; and then, the relative rotation angle adjustment and the integral roll angle around the optical axis are carried out on the double-optical-wedge compensator (3) to finish the measurement.

6. The interferometry device for measuring local steepness profile error of an optical element surface according to claim 5, wherein: the measured mirror (5) is a concave spherical reflector, the semi-aperture is 290mm, and the radius is 1100 mm.

7. The interferometry device for measuring local steepness profile error of an optical element surface according to claim 6, wherein: the laser interferometer main machine (1) emits collimated helium-neon laser with the wavelength of 632.8nm and the caliber of 50 mm; the imaging resolution of the interference pattern detector is 1200 × 1200 pixels.

8. The interferometry device for measuring local steepness profile error of an optical element surface according to claim 7, wherein: the compensating mirror (2) is a standard spherical lens, and the focal length is 100 mm.

9. The interferometry device for measuring local steepness profile error of an optical element surface according to claim 8, wherein: the diameter of the double-optical-wedge compensator (3) is 25.4mm, the wedge angle is +/-2 degrees, and the clear apertureThe center is 25mm thick.

10. The interferometry device for measuring local steepness profile error of an optical element surface according to claim 9, wherein: the double-optical-wedge compensator adjusting frame (4) is a three-dimensional translation table, optical wedges can be moved along the axial direction and two vertical axis directions, and the moving range is 20 mm.

Technical Field

The invention relates to the technical field of photoelectric detection, in particular to an optical element surface local gradient surface shape error interferometry and a corresponding optical element surface local gradient surface shape error interferometry device.

Background

Scientific technology is continuously advanced, requirements on precision and imaging quality of an optical system are higher and higher, an optical system comprising an aspheric optical element can eliminate aberrations such as spherical aberration, coma aberration and field curvature, optical energy loss can be reduced, measurement of the aspheric element becomes a key point for designing and manufacturing the optical system, and the types of detection technologies are more and more. These methods can be broadly categorized into contact measurement and noncontact measurement. The contact detection method usually requires that a measuring head contacts the surface of an optical element to be detected, so that the optical element is easy to scratch, the full-aperture surface shape cannot be measured at one time, and the method is low in precision and speed. In view of many defects of contact measurement, researchers begin to apply non-contact detection means to the measurement of the surface shape of an optical element, and currently, widely applied non-contact measurement methods are mainly classified into structured light three-dimensional measurement methods, interferometry and the like.

The interference measurement is a high-precision optical element surface shape measurement method, and is suitable for the quality detection of the finished optical element in the fine grinding stage. With the continuous progress of the defense industry and the advanced optical technology, the requirements of various optical devices on elements are gradually strict.

At present, in the detection of finished optical elements of spherical surfaces and aspherical surfaces, a detection result with extremely high precision can be obtained by an interferometry. However, in the processing process, for a part of aspheric surfaces, due to the complexity of surface shapes, both in the forming stage and the final polishing stage, complicated track planning and removal amount matching are required, and surface shape errors of local gradients of concave and convex random degrees are easily remained at the edge of a blank. Therefore, the accuracy of the measurement feedback for the profile error will directly determine the efficiency and final accuracy of the compensation process. When the local surface shape error of the surface to be measured is large, the point missing situation that recording and resolving cannot be performed occurs due to the fact that the density of interference fringes is too high in the interference method. The size and direction of the surface shape error of the part of missing results determine the next machining amount, and if the next machining amount cannot be detected, the number of times and time of repeated machining can be greatly increased.

Disclosure of Invention

In order to overcome the defects of the prior art, the technical problem to be solved by the invention is to provide an interference measurement method for the surface shape error of the local steepness of the surface of an optical element, which solves the problem that the surface shape error of the local steepness cannot be measured when the surface shape of a spherical or aspheric optical element is detected in the process of processing by a laser interference measurement technology, realizes the measurement of the surface shape error of the local steepness which cannot be measured before on the premise of not changing the optical path of the original interferometer, has a simple structure, does not need a complicated full-caliber mechanical scanning structure, saves the cost while expanding the measurement range, retains the high precision of the interference measurement, is suitable for the distribution measurement of the surface shape error of the local steepness in the process of processing various optical surfaces such as planes, spheres, aspheric surfaces and the.

The technical scheme of the invention is as follows: the interference measurement method for the surface shape error of the local gradient of the surface of the optical element comprises the following steps:

(1) the method comprises the steps that the laser interferometer host and a compensating mirror are utilized to complete measurement of the full-aperture surface shape error of a measured mirror, and the full-aperture surface shape error distribution phi (x, y) is obtained, wherein effective measurement data cannot be obtained due to too dense interference fringes in a local steepness surface shape error area, and a measurement data missing area is marked to be sigma;

(2) inserting a double-optical-wedge compensator into the optical path corresponding to the region sigma, adjusting three-dimensional coordinates (x, y, z) including axial and two orthogonal transverse positions by using a double-optical-wedge compensator adjusting frame, so that the area of the double-optical-wedge compensator can just cover the whole data missing region, and adjusting the axial position of the measured mirror according to the thickness of the double optical wedge so that the additional phase introduced by the double optical wedge is compensated;

(3) relative rotation angle of rotary double-optical wedge compensator to alpha₁To maximize the deflection of the beam it produces; the rotating double-optical-wedge compensator integrally rolls an angle beta around an optical axis, and dense interference fringe change in a data missing region sigma is observed when a region sigma in the data missing region sigma₁When the middle interference fringe is sparse and can be measured, the integral roll angle beta of the double-optical-wedge compensator around the optical axis at the moment is recorded₁The area σ at this time is measured using an interferometer₁Phase distribution of

(4) Establishing a measurement system model consisting of a laser interferometer host, a compensating mirror and a measured mirror in optical simulation software, wherein the model is based on the position (x, y, z) and the relative rotation angle alpha of the double-optical-wedge compensator₁And an overall roll angle beta about the optical axis₁Model of inserted double optical wedge compensator, using inverse iterative optimization method to obtain phase distributionFinding the region σ₁Median shape error distribution E₁(x,y)；

(5) Rotating the relative rotation angle of the double-optical wedge compensator to alpha by a certain step length delta alpha₂And (4) repeating the step (3) and recording the sigma₂、β₂、Repeating the step (4), and recording the obtained surface shape error distribution E₂(x, y); then, the relative rotation angle of the double-optical wedge compensator is rotated to alpha by taking delta alpha as step length_n＝α₁+180 °, repeat steps (3), (4) and record a series of σ_n、β_n、And E_n(x,y)；

(6) For full aperture surface shape error distribution phi (x, y) and each sigma_nSurface shape error distribution E of region_nAnd (x, y) splicing to obtain the full-aperture surface shape error distribution with complete data.

The invention utilizes the double optical wedge compensator to be placed in the area of the local gradient surface shape error, rotates the relative rotation angle of the double optical wedge compensator and the integral roll angle around the optical axis, and generates the additional tilt compensation phase with adjustable direction, thereby leading the local measuring beam to be matched with the local surface shape, leading the local interference fringes to be sparse at the moment, and utilizing the interferometer to measure the local phase; calculating the introduced phase according to the rotation angle of the double-optical-wedge compensator, inputting the phase into a virtual interferometer model, and calculating to obtain a local surface shape error; sequentially carrying out the measurement process on all parts which cannot be directly measured by the optical element until all the local gradient surface shape errors are measured; splicing the local surface shape error and the full-aperture surface shape error data of the optical element to finish measurement; therefore, the problem that the local gradient surface shape error cannot be measured when the laser interferometry is used for detecting the surface shape of a spherical or aspheric optical element in processing is solved, the previous unmeasurable measurement of the local gradient surface shape error is realized on the premise of not changing the light path of the original interferometer, the structure is simpler, a complex full-caliber mechanical scanning structure is not needed, the cost is saved while the measurement range is expanded, the high precision of interferometry is reserved, the method is suitable for the local gradient surface shape error distribution measurement in the processing process of various optical surfaces such as planes, spheres and aspheric surfaces, and the practicability is high.

Also provided is an optical element surface local gradient profile error interferometry device, comprising: the device comprises a laser interferometer host (1), a compensating mirror (2), a double-optical-wedge compensator (3), a double-optical-wedge compensator adjusting frame (4) and a measured mirror (5);

the wavefront of a measuring beam emitted by the laser interferometer host (1) is modulated by the compensating mirror (2) and then becomes a wavefront matched with the nominal surface shape of the measured mirror (5), the wavefront enters the measured mirror (5), is reflected on the measured mirror (5), returns to the laser interferometer host (1) through the compensating mirror (2) again, and interferes with internal reference light to form interference fringes;

inserting a double-optical-wedge compensator (3) into a data missing area caused by the intensive interference fringes between the compensating mirror (2) and the measured mirror (5), and adjusting the transverse and axial positions of the double-optical-wedge compensator (3) by using a double-optical-wedge compensator adjusting frame (4) to ensure that the area of the double-optical-wedge compensator just can cover the whole data missing area; and then, the relative rotation angle adjustment and the integral roll angle around the optical axis are carried out on the double-optical-wedge compensator (3) to finish the measurement.

Drawings

FIG. 1 is a flow chart of an interferometric method of local steepness profile errors of an optical element surface according to the present invention.

FIG. 2 is a schematic structural diagram of an optical element surface local steepness profile error interferometry device according to the present invention.

The resulting full aperture interferogram is shown in fig. 3.

FIG. 4 shows the region σ₁The local interferogram of (a).

FIG. 5 shows the corresponding measured area σ of FIG. 4 using an interferometer₁The phase distribution of (2).

Fig. 6 shows that repeating step (3) results in another interference pattern of distinct areas.

Fig. 7 shows the phase distribution measured using an interferometer corresponding to fig. 6.

Wherein: the system comprises a laser interferometer host, a 2-compensating mirror, a 3-double-optical wedge compensator, a 4-double-optical wedge compensator adjusting frame and a 5-measured mirror.

Detailed Description

In order to solve the problem that the local gradient surface shape error can not be measured when the laser interferometry is used for detecting the surface shape of a spherical or aspheric optical element in processing, the invention discloses an interferometry method and a device using a double-optical-wedge compensator and sub-aperture splicing, which aim to solve the technical problems that: how to reduce the interference fringe density of a local gradient surface shape error area by using a double-optical wedge compensator, so that an interferometer can measure the surface shape error corresponding to the area, and how to complete the surface shape error data splicing of an irregular sub-aperture measurement area, thereby realizing the measurement of the local gradient surface shape error which cannot be measured before on the premise of not changing the light path of the original interferometer. The invention provides a local compensation splicing interference measurement method based on a double-optical-wedge compensator and a measurement device.

As shown in FIG. 1, the interferometric method for measuring the local steepness profile error of the surface of an optical element comprises the following steps:

(1) the method comprises the steps that the laser interferometer host and a compensating mirror are utilized to complete measurement of the full-aperture surface shape error of a measured mirror, and the full-aperture surface shape error distribution phi (x, y) is obtained, wherein effective measurement data cannot be obtained due to too dense interference fringes in a local steepness surface shape error area, and a measurement data missing area is marked to be sigma;

(2) inserting a double-optical-wedge compensator into the optical path corresponding to the region sigma, adjusting three-dimensional coordinates (x, y, z) including axial and two orthogonal transverse positions by using a double-optical-wedge compensator adjusting frame, so that the area of the double-optical-wedge compensator can just cover the whole data missing region, and adjusting the axial position of the measured mirror according to the thickness of the double optical wedge so that the additional phase introduced by the double optical wedge is compensated;

(3) relative rotation angle of rotary double-optical wedge compensator to alpha₁To maximize the deflection of the beam it produces; the rotating double-optical-wedge compensator integrally rolls an angle beta around an optical axis, and dense interference fringe change in a data missing region sigma is observed when a region sigma in the data missing region sigma₁When the middle interference fringe is sparse and can be measured, the integral roll angle beta of the double-optical-wedge compensator around the optical axis at the moment is recorded₁The area σ at this time is measured using an interferometer₁Phase distribution of

(4) Establishing a measurement system model consisting of a laser interferometer host, a compensating mirror and a measured mirror in optical simulation software, wherein the model is based on the position (x, y, z) and the relative rotation angle alpha of the double-optical-wedge compensator₁And an overall roll angle beta about the optical axis₁Model of inserted double optical wedge compensator, using inverse iterative optimization method to obtain phase distributionFinding the region σ₁Median shape error distribution E₁(x,y)；

(5) Rotating the relative rotation angle of the double-optical wedge compensator to alpha by a certain step length delta alpha₂And (4) repeating the step (3) and recording the sigma₂、β₂、Repeating the step (4), and recording the obtained surface shape error distribution E₂(x, y); then, the relative rotation angle of the double-optical wedge compensator is rotated to alpha by taking delta alpha as step length_n＝α₁+180 °, repeat steps (3), (4) and record a series of σ_n、β_n、And E_n(x,y)；

(6) For full aperture surface shape error distribution phi (x, y) and each sigma_nSurface shape error distribution E of region_nAnd (x, y) splicing to obtain the full-aperture surface shape error distribution with complete data.

The invention utilizes the double optical wedge compensator to be placed in the area of the local gradient surface shape error, rotates the relative rotation angle of the double optical wedge compensator and the integral roll angle around the optical axis, and generates the additional tilt compensation phase with adjustable direction, thereby leading the local measuring beam to be matched with the local surface shape, leading the local interference fringes to be sparse at the moment, and utilizing the interferometer to measure the local phase; calculating the introduced phase according to the rotation angle of the double-optical-wedge compensator, inputting the phase into a virtual interferometer model, and calculating to obtain a local surface shape error; sequentially carrying out the measurement process on all parts which cannot be directly measured by the optical element until all the local gradient surface shape errors are measured; splicing the local surface shape error and the full-aperture surface shape error data of the optical element to finish measurement; therefore, the problem that the local gradient surface shape error cannot be measured when the laser interferometry is used for detecting the surface shape of a spherical or aspheric optical element in processing is solved, the previous unmeasurable measurement of the local gradient surface shape error is realized on the premise of not changing the light path of the original interferometer, the structure is simpler, a complex full-caliber mechanical scanning structure is not needed, the cost is saved while the measurement range is expanded, the high precision of interferometry is reserved, the method is suitable for the local gradient surface shape error distribution measurement in the processing process of various optical surfaces such as planes, spheres and aspheric surfaces, and the practicability is high.

Preferably, in step (3), if no interference fringe in Σ is clear during one rotation of β from 0 to 360, the step (5) is skipped.

Preferably, the specific method of the reverse iterative optimization method in the step (4) is as follows: for region sigma₁Taking the minimum circumcircle as the normalized radius to phase distribution phi₁(x, y) performing Zernike fitting to obtain a fitting coefficient Z_i1The Zernike coefficient Z of the image plane phase is measured in a measurement system model_i1Set as optimization target, measured surface area σ₁Zernike coefficient Z 'of surface shape error of (1)'_1iSetting the variable as an optimized variable, and optimizing by using a damping least square method to obtain Z'_1iIntroducing Zernike polynomials to obtain surface shape error E₁(x,y)。

Preferably, in the step (6), the total caliber surface shape error phi (x, y) is taken as a reference, the square sum of the difference values of the surface shape errors in the overlapped parts of all the pairwise adjacent regions is taken as an optimization target, and the square sum is taken as each sigma_nSurface shape error distribution E of region_nUsing the transformation coefficient of (x, y) as an optimization variable, obtaining the transformation coefficient by utilizing least square optimization, and then using the transformation coefficient to convert phi (x, y) and E_nAnd (x, y) unifying the data in the overlapped parts under a coordinate system, and finally carrying out homogenization fusion or weighted fusion on the data in the overlapped parts to obtain complete full-aperture surface-shaped error distribution.

As shown in fig. 2, there is also provided an optical element surface local steepness profile error interferometry device including: the system comprises a laser interferometer host 1, a compensating mirror 2, a double-optical-wedge compensator 3, a double-optical-wedge compensator adjusting frame 4 and a measured mirror 5;

the wavefront of a measuring beam emitted by the laser interferometer host 1 is modulated by the compensating mirror 2 and then becomes a wavefront matched with the nominal surface shape of the measured mirror 5, the wavefront enters the measured mirror 5, is reflected on the measured mirror 5 and then returns to the laser interferometer host 1 through the compensating mirror 2 again to interfere with internal reference light to form interference fringes;

inserting a double-optical-wedge compensator 3 into a data missing area caused by the intensive interference fringes between the compensating mirror 2 and the measured mirror 5, and adjusting the transverse and axial positions of the double-optical-wedge compensator 3 by using a double-optical-wedge compensator adjusting frame 4 to ensure that the area of the double-optical-wedge compensator just can cover the whole data missing area; and then, the relative rotation angle adjustment and the integral roll angle around the optical axis are carried out on the double-optical-wedge compensator 3, so that the measurement is completed.

Preferably, the measured mirror 5 is a concave spherical reflector, the semi-aperture is 290mm, and the radius is 1100 mm.

Preferably, the laser interferometer main unit 1 emits collimated He-Ne laser with a wavelength of 632.8nm and a caliber of 50 mm; the imaging resolution of the interference pattern detector is 1200 × 1200 pixels.

Preferably, the compensation mirror 2 is a standard spherical lens with a focal length of 100 mm.

Preferably, the diameter of the dual-optical-wedge compensator 3 is 25.4mm, the wedge angle is +/-2 degrees, and the clear aperture isThe center is 25mm thick.

Preferably, the double-optical-wedge compensator adjusting frame 4 is a three-dimensional translation table, and can move the optical wedge along the axial direction and two vertical axis directions, and the moving range is 20 mm.

One embodiment of the present invention is described in detail below.

In this embodiment, the measured mirror 5 is a concave spherical reflector, the semi-aperture is 290mm, and the radius is 1100 mm.

The laser interferometer main unit 1 emits collimated helium neon laser with the wavelength of 632.8nm and the caliber of 50 mm; the imaging resolution of the interference pattern detector is 1200 × 1200 pixels.

The compensating mirror 2 is a standard spherical lens with a focal length of 100 mm.

The diameter of the double-optical-wedge compensator 3 is 25.4mm, the wedge angle is +/-2 degrees, and the clear apertureThe center is 25mm thick.

The double-optical-wedge compensator adjusting frame 4 is a three-dimensional translation table, and can move optical wedges along the axial direction and two vertical axis directions, and the moving ranges are 20 mm.

The measurement steps are as follows:

the method comprises the following steps: the laser interferometer host and the compensating mirror are utilized to complete the measurement of the full-aperture surface shape error of the measured mirror, and the obtained full-aperture interferogram is shown in figure 3, so that the interferogram is too dense at the lower left corner due to local errors and exceeds the recording range of the detector. And measuring a full-aperture surface shape error distribution phi (x, y), wherein the local gradient surface shape error area cannot obtain effective measurement data because the interference fringes are too dense, and marking the measurement data missing area as sigma.

Step two: and inserting a double-optical-wedge compensator into the optical path corresponding to the area sigma, adjusting the axial position and the transverse position (x, y, z) by utilizing a double-optical-wedge compensator adjusting frame to enable the area of the double-optical-wedge compensator to just cover the whole data missing area, and adjusting the axial position of the tested mirror according to the thickness of the double optical wedge to enable the additional phase introduced by the double optical wedge to be compensated.

Step three: relative rotation angle of rotary double-optical wedge compensator to alpha₁To maximize the deflection of the beam it produces; the rotating double-optical-wedge compensator integrally rolls an angle beta around an optical axis, and dense interference fringe change in a data missing region sigma is observed when a region sigma in the data missing region sigma₁When the middle interference fringe is sparse and can be measured, the integral roll angle beta of the double-optical-wedge compensator around the optical axis at the moment is recorded₁Region σ at this time₁The local interferogram of (2) is shown in FIG. 4, and the area σ is measured at this time using an interferometer₁Phase distribution ofAs shown in fig. 5. If no interference fringe is clear in Σ during one rotation of β from 0 to 360, step four is skipped and step five is directly entered.

Step four: establishing a measurement system model consisting of a laser interferometer host, a compensating mirror and a measured mirror in optical simulation software, wherein the model is based on the position (x, y, z) and the relative rotation angle alpha of the double-optical-wedge compensator₁And an overall roll angle beta about the optical axis₁Model of inserted double optical wedge compensator, using inverse iterative optimization method to obtain phase distribution

Finding the region σ₁Median shape error distribution E₁(x,y)。

Step five: rotating the relative rotation angle of the double-optical wedge compensator to alpha by a certain step length delta alpha₂Repeating the third step to obtain another interference pattern with clear area as shown in FIG. 6, measuring the phase distribution as shown in FIG. 7, and recording σ₂、β₂、

Repeating the step four, and recording the obtained surface shape error distribution E₂(x, y). Then, the relative rotation angle of the double-optical wedge compensator is rotated to alpha by taking delta alpha as step length_n＝α₁+180 °, repeat steps three and four to record a series of σ_n、β_n、

And E_n(x,y)。

Step six: for full aperture surface shape error distribution phi (x, y) and each sigma_nSurface shape error distribution E of region_nAnd (x, y) splicing to obtain the full-aperture surface shape error distribution with complete data.

The invention has the following beneficial effects:

1. according to the method and the device, only the double-optical-wedge compensator is added in the traditional interference light path, the structure is simpler, a complex full-aperture mechanical scanning structure is not needed, the measurement range is expanded, the cost is saved, and the high precision of interference measurement is kept.

2. The method and the device are suitable for measuring the local gradient surface shape error distribution in the processing process of various optical surfaces such as planes, spherical surfaces, aspheric surfaces and the like, and have strong practicability.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.