CN113091637B - Ultra-high precision plane mirror full-aperture medium-frequency surface shape measuring device and method - Google Patents
Ultra-high precision plane mirror full-aperture medium-frequency surface shape measuring device and method Download PDFInfo
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- CN113091637B CN113091637B CN202110301016.6A CN202110301016A CN113091637B CN 113091637 B CN113091637 B CN 113091637B CN 202110301016 A CN202110301016 A CN 202110301016A CN 113091637 B CN113091637 B CN 113091637B
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
Abstract
The invention provides a device and a method for measuring the full-aperture intermediate frequency surface shape of an ultra-high precision plane mirror, wherein the measuring device is used for measuring the full-aperture intermediate frequency surface shape of the ultra-high precision plane mirror and comprises the following components: the device comprises a white light interferometer, a microscope objective, an axial displacement platform, an inclination adjusting platform, a lifting device, two standard mirrors, an autocollimator, a computer system and a marble base. The white light interferometer is arranged on a lifting device on the marble beam; the measuring platform consisting of the axial displacement table and the inclined adjusting table is arranged on the marble base, and the spatial attitude of the ultra-high precision plane mirror to be measured in the measuring process is monitored in real time through two vertically arranged autocollimator angle measuring systems; the computer system is connected with the white light interferometer and used for collecting surface shape information of the ultrahigh-precision plane mirror aperture area; and finally, combining the detection data of the autocollimator with spliced data processing software to obtain the full-aperture surface shape error of the ultra-high precision plane mirror.
Description
Technical Field
The invention belongs to the technical field of advanced optical manufacturing and detection, and particularly relates to a device and a method for measuring the full-aperture medium-frequency surface shape of a plane mirror with ultrahigh precision.
Background
With the continuous development of modern optics, the application of ultra-high precision optical elements is more and more extensive. Especially, the application of the ultra-high precision plane mirror is more and more emphasized, and the detection precision and the detection frequency band are strictly required. Modern optics require the ultra-high precision plane mirror not only to have low frequency surface shape precision, but also to take certain consideration to medium frequency surface shape information.
The optical interference detection technology is widely applied to the field of surface shape detection as an effective high-precision optical surface shape detection technology. Common optical detection technologies such as Fizeau interferometers are biased towards low-frequency surface shape detection, and only partially cover medium-frequency surface shape detection capability. The measurement resolution and precision of the white light interferometer are both superior to those of the Fizeau interferometer, and the measurement frequency band of the white light interferometer is 1mm-1～1μm-1Meanwhile, the measurement result has richer information. However, the effective measurement field of view of the white light interferometer is very small, and when the low-power microscope objective is equipped, the effective field of view is only about 5mm to 5mm, and the full field cannot be realized And detecting the caliber surface shape. The splicing measurement technology greatly widens the measurement range of the white light interferometer, and the detection technology applying the splicing technology to the white light interferometer at present mainly comprises a relative angle splicing interferometer-based micro-splicing technology, a autocollimator angle auxiliary measurement system-based micro-splicing technology and a micro-splicing technology which only depends on the precision and the algorithm of a measurement table. The relative angle splicing technology device is too complex, and the measuring range is relatively limited; the current angle auxiliary measurement technology can only realize single-row sub-aperture surface shape detection; and the micro-splicing technology which only depends on the precision and the algorithm of the measuring table cannot meet the splicing detection of the plane mirror with ultrahigh precision.
Disclosure of Invention
The invention provides a device and a method for measuring the full-aperture medium-frequency surface shape of an ultra-high precision plane mirror, aiming at solving the problem of full-aperture medium-frequency detection of the ultra-high precision plane mirror.
The technical scheme adopted by the invention is as follows: a full-aperture intermediate frequency surface shape measuring device for an ultra-high precision plane mirror comprises a marble base, a lifting device, an axial displacement table, an inclination adjusting table, a white light interferometer, a microscope objective, a short standard plane mirror, an ultra-high precision plane mirror, a long standard plane mirror, a computer system and an autocollimator; the white light interferometer is arranged on the lifting device and is fixed on the marble base together with the axial displacement table to isolate errors caused by environmental factors; the inclined adjusting platform is arranged on the axial displacement platform to realize the adjustment of the spatial position and the attitude of the ultra-high precision plane mirror; the long standard plane mirror and the short standard plane mirror are arranged on the inclined adjusting platform, are respectively parallel to the length direction and the width direction of the ultra-high precision plane mirror and are centered, and have constant relative positions and move together; the long standard plane mirror and the short standard plane mirror are respectively matched with the two autocollimators to form an angle measuring system. And the computer system is connected with the white light interferometer and the autocollimator and is used for acquiring, storing and processing the surface shape data acquired by the white light interferometer and the relative angle change of each sub-aperture acquired by autocollimation. And adjusting the translation stage, collecting the subapertures (adjacent subapertures have certain overlapping areas) of the region to be measured of the ultra-high precision plane mirror, and obtaining the surface shape error of the region to be measured of the ultra-high precision plane mirror according to a splicing algorithm.
The white light interferometer is connected with the lifting device and used for driving the white light interferometer to move in the vertical direction so as to realize focusing;
the white light interferometer is connected with the lifting device and arranged on the marble base gantry and used for collecting ultrahigh-precision plane mirror surface shape data;
the ultrahigh-precision plane mirror is arranged on the inclined adjusting table and is opposite to the microscope objective of the white light interferometer; the inclination adjusting platform is used for adjusting the inclination of the ultra-high precision plane mirror to realize zero fringe measurement;
the inclined adjusting platform is used as a measuring base and is arranged on the axial displacement platform and used for driving the ultra-high precision plane mirror to move in the length direction and the width direction.
The axial displacement table is fixed on the marble base and is vertical to the optical axis of the white light interferometer; and the device is used for driving the inclination adjusting platform to displace and adjusting the relative position of the ultra-high precision plane mirror and the microscope objective.
The long standard plane mirror is arranged on the inclined adjusting platform, is parallel to the length direction of the ultrahigh-precision plane mirror and is centered, and the long standard plane mirror and the ultrahigh-precision plane mirror have constant relative positions and move together;
The first autocollimator is opposite to the long standard plane mirror and is used for collecting the angle change of the long standard plane mirror in the measurement process of each sub-aperture and representing the relative position of each sub-aperture.
The short standard plane mirror is arranged on the inclined adjusting platform, is parallel to and centered with the ultrahigh-precision plane mirror in the width direction, has a constant relative position and moves together;
the second autocollimator is opposite to the short standard plane mirror and is used for collecting the angle change of the short standard plane mirror in the measurement process of each sub-aperture and representing the relative position of each sub-aperture.
The computer system is connected with the white light interferometer, the first autocollimator and the second autocollimator and is used for collecting, storing and processing the surface shape data collected by the white light interferometer and the relative angle change of each sub-aperture collected by autocollimation.
Furthermore, the measuring device is mainly used for measuring the full-aperture medium-frequency surface shape error of the ultra-high precision plane mirror; the device can also realize the measurement of the full-aperture low-frequency surface shape error of the ultra-high precision plane mirror.
Further, sub-aperture division is carried out on the ultra-high-precision plane mirrors according to the effective view field size of the microscope objective, and the white light interferometer is used for focusing the ultra-high-precision plane mirrors in each sub-aperture area; and the inclination adjustment table and the axial displacement table are utilized to realize the inclination and translation of the ultra-high precision plane mirror in each sub-aperture area, so that the zero fringe detection of each sub-aperture of the ultra-high precision plane mirror is realized, and finally, the full-aperture intermediate frequency surface shape error is obtained through data processing.
Furthermore, an auxiliary angle measuring device consisting of the autocollimator and the standard plane mirror monitors the change of the relative angle of each sub-aperture in the process that the inclined adjusting table and the axial displacement table drive the ultra-high precision plane mirror to realize the measurement of each sub-aperture in real time.
Furthermore, a certain overlapping area is formed between adjacent sub-aperture surface shape data sets acquired by the white light interferometer, and the high-precision surface shape error splicing processing of the ultra-high-precision plane mirror is realized by combining a sub-aperture overlapping area matching method based on a Zernike polynomial and an auxiliary angle measuring device consisting of the autocollimators.
Further, the ultrahigh-precision plane mirror adjusts the position of the self-inclined state through the inclination adjusting platform.
Furthermore, the multiplying power of the microscope objective can be selected according to the requirement.
In order to achieve the purpose, the invention also provides a method for measuring the full-aperture medium-frequency surface shape of the ultra-high precision plane mirror, which comprises the following steps:
step a: planning an ultrahigh-precision plane mirror measurement area, determining the size of a sub-aperture area and parameters of an overlapping area, generating a sub-aperture division model, and adjusting a displacement table to move the sub-aperture area at the edge of the ultrahigh-precision plane mirror to the effective measurement field of view of a white light interferometer.
Step b: adjusting the inclination state of the ultra-high precision plane mirror by an inclination adjusting platform to enable the interference pattern of the sub-aperture area to be measured to be in a zero stripe state, driving the white light interferometer to move up and down for focusing by the lifting device, and collecting the surface shape data T of the sub-aperture at the initial position0(x, y) and recording the tilt angles around the y-axis measured by the first autocollimator 8, respectively
And the angle of inclination about the x-axis measured by the second autocollimator
As the initial angular position of the reference sub-aperture.
Step c: adjusting the axial displacement table, and moving the ultra-high precision plane mirror by delta along the x and y directions according to the sub-aperture division model x、ΔyTo the next sub-aperture, the sub-aperture and the previous sub-aperture generally have an overlap area of 35-50%; adjusting the inclined adjusting platform to enable the interference pattern of the sub-aperture area to be measured to be in a zero-stripe state, and recording the angles measured by the first autocollimator 8 and the second autocollimator at the moment
Meanwhile, a white light interferometer collects the surface shape data T of the sub-aperture1(x，y)。
Step d: and e, adjusting the axial displacement table to translate the ultrahigh-precision plane mirror to the next sub-aperture, and repeating the step c until the white light interferometer sweeps the area to be measured of the ultrahigh-precision plane mirror. The collected surface shape data meet the following conditions:
in the formula, Wi(x, y) is the overlapping area profile of the ith sub-aperture and the (i-1) th sub-aperture; w is a group ofi(x, y) is the surface shape of the overlapping area of the ith sub-aperture and the ith sub-aperture on the (i-1) th sub-aperture;
respectively representing the angle change of the ith sub-aperture relative to the (i-1) th sub-aperture around the x and y axes obtained by the autocollimator; c. Ci，i-1The difference of the ith sub-aperture relative to the vertical direction of the (i-1) th sub-aperture;
dividing the ith theoretical subaperture surface shape error of the reference subaperture; t isiThe data of the ith sub-aperture surface shape collected by using a white light interferometer; a isi，bi，CiThe amounts of inclination in x, y and the difference in height in the vertical direction introduced with respect to the theoretical surface shape are respectively expressed as follows:
Step e: the computer system processes the acquired sub-aperture data set and the angle information set: firstly, extracting surface shape data of each sub-aperture, and realizing matching alignment of each sub-aperture through point-to-point matching of overlapping areas of each sub-aperture. For any two adjacent sub-apertures, the overlapping area of the two sub-apertures satisfies the following Zernike polynomial:
in the formula (I), the compound is shown in the specification,
a j-th term Zernike polynomial which is an i-th sub-aperture overlapping region;
the j-th Zernike polynomial coefficient of the i-th sub-aperture overlap region.
Because only tilt around x and y axes and translation aberration along the vertical direction are induced in the sub-aperture displacement process, the difference of the overlapping areas of two adjacent sub-apertures is only the three aberrations. Therefore, when the overlapping area of two adjacent sub-apertures is expressed by using the zernike coefficient, the difference is only in the first 3 terms, and then:
in the formula, ZjIs an ith Zernike polynomial.
According to the sub-aperture division model, respectively roughly determining a central coordinate P on the overlapping region of the i-1 th sub-aperture and the i-th sub-aperture adjacent to the i-th sub-aperturei-1(x0，y0)、Pi(x0，y0) At the overlapping area of two sub-apertures, respectively, by a point Pi-1And point PiAt origin, in (x-x)0)2+(y-y0)2＜R2(R is less than the minimum length of the overlapping region) on the region 
To be provided with
As a reference region, a point P is formed on the i-th sub-aperture overlapping regioniSelecting an iteration region (x-x) for the center0)2+(y-y0)2< delta, i.e. point Pi∈{(x-x0)2+(y-y0)2< delta >, point PiIterate a loop over the region until a point is found
Satisfies the following conditions:
at this time, a point within the i-th sub-aperture overlapping region is considered
And point P on the i-1 st sub-aperturei-1And (4) coinciding, and then determining a coincident point pair 1. Similarly, after the central point is determined, another two points are respectively searched by taking the central point as a reference, and the iterative process is repeated to find the coincident point pair 2 and the coincident point pair 3. And realizing point-to-point matching of the ith sub-aperture and the (i-1) th sub-aperture according to the 3 pairs of coincident point pairs. And finally, processing the sub-aperture set according to the process to realize point-to-point matching of each sub-aperture and establish a matched sub-aperture data set.
Secondly, the matched sub-aperture data sets need to be spliced together: and according to the obtained consistency of the overlapping areas between the adjacent sub-apertures, minimizing the root mean square error of the overlapping areas of the adjacent sub-apertures to realize sub-aperture splicing:
wherein: wi-1(x，y)，Wi(x, y) are respectively the surface shape data of the overlapping area of the ith sub-aperture and the (i-1) th sub-aperture; a isi，biCorresponding to the angle of inclination, C, of longitudinally and transversely adjacent sub-apertures, respectively iIndicating the difference in the vertical direction. The above-mentioned tilt parameters are generally fit by using least square methodHowever, the accuracy of the tilt parameters fitted by the algorithm cannot meet the accuracy of the medium-frequency plane shape inspection of the ultra-high-accuracy plane mirror. The angular position of the sub-aperture thus recorded by the first autocollimator and the second autocollimator
The specific operation process is that the sum of the angle changes recorded before is used as the inclination parameter a of the ith sub-aperturei，bi：
Sequential stitching is then achieved by minimizing the equation, where the difference in vertical direction CiThe method can be obtained through simple calculation, and has small influence on the final splicing precision. And finally, obtaining the medium-frequency surface shape error of the ultra-high precision plane mirror in a sequential splicing mode.
Compared with the prior art, the invention has the advantages that:
(1) the full-aperture medium-frequency surface shape measuring device for the ultra-high precision plane mirror is characterized in that an angle measurement auxiliary system based on a double-autocollimator is organically combined with a sub-aperture splicing technology, the angle measurement auxiliary system of the double-autocollimator is utilized to monitor the angles of each sub-aperture in two directions in the measuring process, the angle measurement result is directly used in the splicing process, and the splicing precision of the ultra-high precision plane mirror is greatly improved.
(2) In the detection process of the full-aperture intermediate frequency surface shape measuring device for the ultra-high precision plane mirror, the angle measurement auxiliary system based on the double autocollimators is introduced, so that the tilt adjusting table can be measured in real time, the splicing precision is ensured without introducing the ultra-high precision tilt adjusting table, and the measurement cost is greatly reduced.
(3) The full-aperture intermediate-frequency surface shape measuring method for the ultra-high-precision plane mirror, provided by the invention, uses a multi-region feature matching algorithm based on Zernike polynomials, can accurately realize point-to-point matching of sub-aperture overlapping regions, and can eliminate position errors introduced by an axial displacement table in the sub-aperture moving process, thereby improving the splicing measurement precision.
(4) The device for measuring the full-aperture intermediate frequency surface shape of the ultra-high precision plane mirror is simple in required equipment and easy to operate, and provides an effective device for measuring the full-aperture intermediate frequency surface shape of the ultra-high precision plane mirror.
Drawings
FIG. 1 is a schematic diagram of a full-aperture medium-frequency surface shape measuring device for an ultra-high precision plane mirror according to the present invention;
FIG. 2 is a schematic diagram of the data acquisition distribution of the full-aperture sub-aperture of the square ultra-high precision plane mirror;
FIG. 3 is a schematic diagram of the data acquisition distribution of the full aperture sub-aperture of the circular ultra-high precision plane mirror;
FIG. 4 is a flow chart of data processing in the computer system of the present invention;
the reference numbers in the figures mean: the device comprises a marble base 1, a lifting device 2, an axial displacement table 3, an inclination adjusting table 301, a white light interferometer 4, a microscope objective 401, a short standard plane mirror 5, an ultrahigh precision plane mirror 6, a long standard plane mirror 7, a first autocollimator 8, a computer system 9 and a second autocollimator 10.
Detailed Description
To further illustrate the features of the present invention, reference is made to the following description, taken in conjunction with the accompanying drawings, which is a more detailed description of the invention.
FIG. 1 shows a device for measuring the full aperture intermediate frequency surface shape of an ultra-high precision plane mirror, which comprises: the device comprises a marble base 1, a lifting device 2, an axial displacement table 3, an inclination adjusting table 301, a white light interferometer 4, a microscope objective 401, a short standard plane mirror 5, an ultrahigh precision plane mirror 6, a long standard plane mirror 7, a first autocollimator 8, a computer system 9 and a second autocollimator 10; wherein, the white light interferometer 4 is arranged on the lifting device 2 and is fixed on the marble base 1 together with the axial displacement table 3 to isolate the error caused by environmental factors; the inclined adjusting platform 301 is arranged on the axial displacement platform 3 to realize the adjustment of the spatial position and the attitude of the ultra-high precision plane mirror 6; the long standard plane mirror 7 and the short standard plane mirror 5 are arranged on the inclined adjusting platform 301, are respectively parallel to and centered with the length direction and the width direction of the ultra-high precision plane mirror 6, and the short standard plane mirror 5, the long standard plane mirror 7 and the ultra-high precision plane mirror 6 have constant relative positions and move together; the long standard plane mirror 7 and the short standard plane mirror 5 are respectively matched with the first autocollimator 8 and the second autocollimator 10 to form an angle measuring system. The computer system 10 is connected with the white light interferometer 4, the first autocollimator 8 and the second autocollimator 10, and is used for collecting, storing and processing the surface shape data collected by the white light interferometer and the relative angle change of each sub-aperture collected by autocollimation. And adjusting the axial displacement table 3, collecting the sub-apertures (adjacent sub-apertures have certain overlapping areas) of the area to be measured of the ultra-high precision plane mirror 6, and obtaining the surface shape error of the area to be measured of the ultra-high precision plane mirror according to a splicing algorithm.
The method for measuring the full-aperture medium-frequency surface shape of the ultra-high precision plane mirror comprises the following steps:
a, step a: planning an ultra-high precision plane mirror region to be measured, for example, dividing a large effective measurement region into a plurality of sub-apertures and overlapping regions as shown in fig. 2 (a shadow region is an actual measurement region) aiming at the plane mirror surface shape detection of a square mirror; the sub-aperture planning area of the circular plane mirror is shown in figure 3 (the shaded area is the actual measurement area); and adjusting the axial displacement table to move the sub-aperture at the edge of the ultra-high precision plane mirror to the position of the O-aperture in the field of view of the white light interferometer in the figure 2.
Step b: adjusting the inclination state of the ultra-high precision plane mirror by an inclination adjusting platform to enable the interference pattern of the sub-aperture area to be measured to be in a zero stripe state, driving the white light interferometer to move up and down for focusing by the lifting device, and collecting the surface shape data T of the sub-aperture at the initial position0(x, y) and recording the tilt angles around the y-axis measured by the first autocollimator 8, respectively
And the angle of inclination about the x-axis measured by the second autocollimator 10
As the initial angular position of the reference sub-aperture.
Step c: adjusting the axial displacement table to make the ultra-high precision plane mirror move delta along the x direction according to the sub-aperture division directionxTo the next subaperture, as shown in FIG. 2; the sub-aperture and the previous sub-aperture generally have an overlapping area of 35-50%; adjusting the inclined adjusting platform to make the interference pattern of the sub-aperture area to be measured in a zero-stripe state, and recording the angle measured by the first autocollimator 8 and the second autocollimator 10 at the moment 
Meanwhile, a white light interferometer collects the surface shape data T of the sub-aperture1(x，y)。
Step d: and c, adjusting an axial displacement table according to the sub-aperture dividing direction as shown in the arrow direction in fig. 2 to translate the ultra-high precision plane mirror to the next sub-aperture, repeating the step c until the scanning of the first sub-aperture is completed, and scanning along the route planned in fig. 2 until the area to be measured of the ultra-high precision plane mirror is completed.
Step e: the computer system processes the acquired sub-aperture profile dataset and the angle dataset as shown in fig. 4: firstly, reading acquired sub-aperture surface shape data; respectively reading the (i-1) th and ith sub-aperture data, matching three coincident points in the overlapping area of the (i-1) th and ith sub-apertures by utilizing a multi-feature region coincidence algorithm based on a Zernike polynomial, realizing point-to-point matching of adjacent sub-apertures according to the coincident points and recording the position of the ith sub-aperture; secondly, sequentially reading the matched i-1 th sub-aperture data and i-th sub-aperture data, and utilizing the angle data a recorded by the autocollimatori，biCorrecting the ith sub-aperture data, and minimizing the surface shape difference of the overlapping area of adjacent sub-apertures to realize splicing operation; finally, the full-aperture surface profile of the ultra-high precision plane mirror is obtained.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any modifications or substitutions that can be understood by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (8)
1. The utility model provides an ultra high accuracy level crossing full bore intermediate frequency profile of face measuring device which characterized in that: the device comprises a marble base (1), a lifting device (2), an axial displacement table (3), an inclined adjusting table (301), a white light interferometer (4), a microscope objective (401), a short standard plane mirror (5), an ultrahigh precision plane mirror (6), a long standard plane mirror (7), a first autocollimator (8), a computer system (9) and a second autocollimator (10);
the white light interferometer (4) is connected with the lifting device (2) and is used for driving the white light interferometer (4) to move in the vertical direction to realize focusing;
the white light interferometer (4) is connected with the lifting device (2) and is arranged on the gantry of the marble base (1) and used for collecting ultrahigh-precision plane mirror surface shape data;
the ultrahigh-precision plane mirror (6) is arranged on the inclined adjusting table (301) and is opposite to the microscope objective of the white light interferometer (4); the inclination adjusting platform (301) is used for adjusting the inclination of the ultra-high precision plane mirror (6) to realize zero fringe measurement;
The inclined adjusting platform (301) is used as a measuring base and is arranged on the axial displacement platform (3) and used for driving the ultrahigh-precision plane mirror (6) to move in the length and width directions;
the axial displacement table (3) is fixed on the marble base (1) and is vertical to the optical axis of the white light interferometer (4); the device is used for driving the inclination adjusting platform (301) to displace and adjusting the relative position of the ultrahigh-precision plane mirror (6) and the microscope objective (401);
the long standard plane mirror (7) is arranged on the inclined adjusting platform (301) and is parallel to and centered with the length direction of the ultra-high precision plane mirror (6), and the long standard plane mirror (7) and the ultra-high precision plane mirror (6) have constant relative positions and move together;
the first autocollimator (8) is opposite to the long standard plane mirror (7) and is used for collecting the angle change of the long standard plane mirror (7) in the measurement process of each sub-aperture to represent the relative position of each sub-aperture;
the short standard plane mirror (5) is arranged on the inclined adjusting platform (301) and is parallel to and centered with the ultra-high precision plane mirror (6) in the width direction, and the short standard plane mirror (5) and the ultra-high precision plane mirror (6) have constant relative positions and move together;
The second autocollimator (10) is opposite to the short standard plane mirror (5) and is used for collecting the angle change of the short standard plane mirror (5) in the measurement process of each sub-aperture to represent the relative position of each sub-aperture;
the computer system (9) is connected with the white light interferometer (4), the first autocollimator (8) and the second autocollimator (10) and is used for collecting, storing and processing the surface shape data collected by the white light interferometer (4) and the relative angle change of each sub-aperture collected by the first autocollimator and the second autocollimator.
2. The ultra-high precision plane mirror full aperture intermediate frequency surface shape measuring device of claim 1, characterized in that: the measuring device is mainly used for measuring the full-aperture medium-frequency surface shape error of the ultra-high precision plane mirror; the device can also realize the measurement of the full-aperture low-frequency surface shape error of the ultra-high precision plane mirror.
3. The ultra-high precision plane mirror full aperture intermediate frequency surface shape measuring device of claim 2, characterized in that: the ultrahigh-precision plane mirror full-aperture intermediate-frequency surface shape error measurement is carried out, sub-aperture division is carried out on the ultrahigh-precision plane mirror according to the effective view field size of the microscope objective, and the white light interferometer is used for realizing focusing of the ultrahigh-precision plane mirror in each sub-aperture area; and the inclination adjustment table and the axial displacement table are utilized to realize the inclination and translation of the ultra-high precision plane mirror in each sub-aperture area, so that the zero stripe detection of each sub-aperture of the ultra-high precision plane mirror is realized, and finally, the full-aperture intermediate frequency surface shape error is obtained through data processing.
4. The ultra-high precision plane mirror full aperture intermediate frequency surface shape measuring device of claim 1, characterized in that: and the autocollimator and the standard plane mirror form an auxiliary angle measuring device for monitoring the relative angle change of each sub-aperture in the process that the inclined adjusting table and the axial displacement table drive the ultrahigh-precision plane mirror to realize the measurement of each sub-aperture in real time.
5. The ultra-high precision plane mirror full aperture intermediate frequency surface shape measuring device of claim 1, characterized in that: and a certain overlapping area is formed between adjacent sub-aperture surface shape data sets acquired by the white light interferometer, and the high-precision surface shape error splicing processing of the ultrahigh-precision plane mirror is realized by combining a sub-aperture overlapping area matching method based on a Zernike polynomial and an auxiliary angle measuring device consisting of the autocollimators.
6. The ultra-high precision plane mirror full-aperture medium-frequency surface shape measuring device of claim 1, which is characterized in that: the ultrahigh-precision plane mirror adjusts the self-inclination state position through the inclination adjusting platform.
7. The ultra-high precision plane mirror full-aperture medium-frequency surface shape measuring device of claim 1, which is characterized in that: the multiplying power of the microscope objective is selected according to the requirement.
8. An ultra-high precision plane mirror full aperture intermediate frequency surface shape measurement method, which utilizes the ultra-high precision plane mirror full aperture intermediate frequency surface shape measurement device of claim 1, and is characterized in that: the measurement steps are as follows:
a, step a: planning a region to be measured of the ultrahigh-precision plane mirror, dividing each sub-aperture region and the size of the overlapping region, and adjusting a displacement table to move the sub-aperture region at the edge of the ultrahigh-precision plane mirror to the effective measurement field of a white light interferometer;
step b: adjusting the inclination state of the ultra-high precision plane mirror to enable the interference pattern of the sub-aperture area to be measured to be in a zero stripe state, driving the white light interferometer to move up and down for focusing by the lifting device, and collecting the surface shape data of the sub-aperture at the initial positionT0(x, y) recording the tilt angles around the y-axis measured by the first autocollimator (8) respectively
And the angle of inclination about the x-axis measured by the second autocollimator (10)
As a reference sub-aperture initial angular position;
step c: adjusting the axial displacement table to make the ultra-high precision plane mirror move delta along the x and y directionsx、ΔyTo the next sub-aperture, the sub-aperture having an overlap area of 35-50% with the previous sub-aperture; adjusting the inclined adjusting platform to enable the interference pattern of the sub-aperture area to be measured to be in a zero-stripe state, and recording the angle measured by the first autocollimator (8) and the second autocollimator (10) at the moment 
The white light interferometer collects the surface shape data T of the sub-aperture1(x，y)；
Step d: and c, adjusting the axial displacement table to translate the ultra-high-precision plane mirror to the next sub-aperture, and repeating the step b until the white light interferometer sweeps the area to be measured of the ultra-high-precision plane mirror, wherein the acquired surface shape data meet the following conditions:
in the formula, Wi(x, y) is the overlapping area profile of the ith sub-aperture and the (i-1) th sub-aperture; wi-1(x, y) is the surface shape of the overlapping area of the i-1 st sub-aperture and the i-2 nd sub-aperture;
display unitObtaining the angle change of the ith sub-aperture relative to the (i-1) th sub-aperture around the x axis through an autocollimator;
the angle change of the ith sub-aperture relative to the (i-1) th sub-aperture around the y axis is obtained through the autocollimator; c. Ci，i-1The difference of the ith sub-aperture relative to the vertical direction of the (i-1) th sub-aperture;
dividing the ith theoretical subaperture surface shape error of the reference subaperture; t isiThe data of the ith sub-aperture surface shape collected by using a white light interferometer; a isi，bi，CiThe amounts of inclination in x, y and the difference in height in the vertical direction introduced with respect to the theoretical surface shape are respectively expressed as follows:
step e: the computer system processes the acquired sub-aperture data set and the angle information set: firstly, extracting surface shape data of each sub-aperture, realizing matching alignment of each sub-aperture through point-to-point matching of overlapping areas of each sub-aperture, and meeting the overlapping areas of any two adjacent sub-apertures according to a Zernike polynomial:
In the formula (I), the compound is shown in the specification,
a j-th term Zernike polynomial which is an i-th sub-aperture overlapping region;
is the ith subThe j-th terms of the Zernike polynomial coefficients of the aperture overlapping area only cause the inclination around the x-axis and the y-axis and the translation aberration along the vertical direction in the sub-aperture displacement process, and the overlapping area difference of two adjacent sub-apertures has only three aberrations, so when the overlapping area of two adjacent sub-apertures is expressed by the Zernike coefficients, the difference is only the first 3 terms, and then:
in the formula, ZjIs a j-th Zernike polynomial;
according to the sub-aperture division model, respectively roughly determining a central coordinate P on the overlapping region of the i-1 th sub-aperture and the i-th sub-aperture adjacent to the i-th sub-aperturei-1(x0，y0)、Pi(x0，y0) At the overlapping area of two sub-apertures, respectively, by a point Pi-1And point PiAt origin, in (x-x)0)2+(y-y0)2＜R2R is smaller than the minimum length of the overlapping area, and an overlapping area matching area is constructed
To be provided with
As a reference region, a point P is formed on the i-th sub-aperture overlapping regioniSelecting an iteration region (x-x) for the center0)2+(y-y0)2< 6, i.e., point Pi∈{(x-x0)2+(y-y0)2< delta >, point PiIterate a loop over the region until a point is found
Satisfies the following conditions:
at this time, a point within the i-th sub-aperture overlapping region is considered
And point P on the i-1 st sub-aperturei-1Overlapping, and then determining an overlapping point pair 1; similarly, after the central point is determined, another two points are respectively searched by taking the central point as a reference, and the iterative process is repeated to find the coincident point pair 2 and the coincident point pair 3; point-to-point matching of the ith sub-aperture and the (i-1) th sub-aperture is realized according to the 3 pairs of coincident points; finally, processing the sub-aperture set according to the process to realize point-to-point matching of each sub-aperture and establish a matched sub-aperture data set;
Secondly, the matched sub-aperture data sets need to be spliced together: and according to the obtained consistency of the overlapping areas between the adjacent sub-apertures, minimizing the root mean square error of the overlapping areas of the adjacent sub-apertures to realize sub-aperture splicing:
min∑{Wi-1(x，y)-[Wi(x，y)+aix+biy+Ci]}2
wherein: the inclination quantity can be fitted by using a least square method, but the accuracy of the inclination parameter fitted by the algorithm cannot meet the accuracy of the medium-frequency surface shape inspection of the ultra-high-accuracy plane mirror; the angular position of the sub-aperture thus recorded by the first autocollimator (8) and the second autocollimator (10)
To realize the ultra-high precision plane mirror surface shape detectionThe specific operation process is to take the sum of the angle changes recorded before as the inclination amount a of the ith sub-aperturei，bi：
Sequential splicing is then achieved by minimizing the equation, where the height difference in the vertical direction CiThe method can be obtained through simple calculation, and has small influence on the final splicing precision; and finally, obtaining the medium-frequency surface shape error of the ultra-high precision plane mirror in a sequential splicing mode.
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