CN116793292A - Swing arm type profiler for surface shape measurement and measurement method thereof - Google Patents

Abstract

The invention relates to a swing arm type profiler for surface shape measurement and a measurement method thereof, comprising a support platform, wherein an adjusting assembly is arranged on the support platform, and a first upright post and a second upright post are arranged on the support platform; the measuring module comprises a rotating frame and an air floatation rotating table, wherein the air floatation rotating table is arranged on the rotating frame, a first bearing seat is arranged on a first upright, a first rotating shaft is arranged in the first bearing seat, a second bearing seat is arranged on a second upright, a second rotating shaft is arranged in the second bearing seat, one end of the second rotating shaft is provided with a first angle encoder, one end of the rotating frame is arranged on the first upright, the other end of the rotating frame is arranged on the second upright, the rotating frame is pitching in a space between the first upright and the second upright, the air floatation rotating table is hinged with a swing arm, and the swing arm is connected with a non-contact measuring head. The invention can meet the requirements of measuring the surface shape of the aspheric surface from milling, grinding to rough polishing, realize the surface shape measurement of the aspheric optical element with any curvature and small caliber, has high detection efficiency and single source of motion error, and improves the measurement precision.

Description

Swing arm type profiler for surface shape measurement and measurement method thereof

Technical Field

The invention relates to the technical field of surface shape measurement of optical elements, in particular to a swing arm type profilometer for surface shape measurement and a measurement method thereof.

Background

In recent years, the aspherical optical element plays an important role in military use and civil use due to its excellent optical performance, and the demand for high-precision aspherical measurement technology is increasing. The measuring methods of the aspheric optical element are various, any measuring method has respective characteristics and application ranges, and a single measuring means is difficult to meet the requirements of the measuring precision and the measuring efficiency of the aspheric surface shape in different types (surface shape, material and the like), different sizes (large, medium, small and miniature) and different manufacturing stages (milling, grinding, polishing, fine polishing and the like), and a plurality of measuring methods are generally required to be comprehensively used to ensure that the measuring precision grades of the aspheric surface shape in each manufacturing stage are effectively connected, so that the manufacturing process is ensured to be efficient and continuous.

In particular, the aspherical surface with small caliber and high steepness occupies a small specific gravity in the aspherical optical element, and plays an indispensable role in various fields, such as a fisheye lens on a camera, a conformal optical fairing on a missile, and the like. However, the high steepness characteristic makes the surface shape measurement of the aspherical surface difficult by one step.

In general, in the initial stage of milling and grinding, the surface shape of a machined mirror surface with small caliber and high steepness deviates greatly from the target surface shape, and a coordinate measuring method such as a three-Coordinate Measuring Machine (CMM) is generally adopted; in the stage of grinding to rough polishing, the surface shape error is still larger, interference fringes which cannot be measured or measured by an interferometer are too dense, and the surface shape error is generally measured by adopting a non-contact profilometer and a shack-Hartmann wavefront detection method; interferometry is the primary measure of the finish polishing and final stage of the aspheric surface.

However, when the contact type three-coordinate measuring instrument measures the high-gradient aspheric surface, the side surface of the measuring needle is contacted with the mirror surface, and the measuring head radius compensation must be carried out on the measured data, otherwise, larger measuring error can be caused; at the same time, the measuring accuracy is also affected by the lateral force of the stylus from the mirror. On the other hand, the height of the high-steepness aspheric surface varies drastically along the generatrix, and when the interferometer is used for measurement, dense interference fringes which are difficult to distinguish by a detector can be generated, and the measurement must be realized by means of a compensator or by adopting an annular sub-aperture splicing method. Three-coordinate measuring machines have many disadvantages in detecting high steepness aspheres, and interferometry can only be used as a means for fine polishing and final inspection stages.

Although the swing arm type profilometer can effectively connect the measurement precision of the three-coordinate measuring instrument and the interferometer, the swing arm type profilometer developed by domestic and overseas scientific research units at present is mostly used for detecting the surface shape of an aspheric mirror with large caliber and large curvature radius, and when the surface shape of the aspheric mirror with large caliber and large curvature radius is detected, in order to reduce the influence of the weight of the swing arm and the weight of a measuring head on the measurement result caused by the tiny bending deformation of the swing arm, a cylindrical arm with larger diameter is mostly adopted, and the swing arm type profilometer is very heavy; the measuring surface of the large-caliber aspheric optical element is a gentler aspheric surface, and the swing arm profiler is applied to the surface shape measurement of the small-caliber high-gradient aspheric mirror, has poor measuring precision and is not beneficial to further processing.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to overcome the defects that the three-coordinate measuring instrument in the prior art has a plurality of defects in detecting the high-gradient aspheric surface, the interferometry can only be used as a means of fine polishing and final inspection stage, the swing arm type profilometer adopts a cylindrical arm with larger diameter, is very heavy, and is applied to the surface shape measurement of the small-caliber and high-gradient aspheric mirror, and the defect of poor measurement precision is overcome.

In order to solve the technical problems, the invention provides a swing arm type profiler for surface shape measurement, which comprises

The support platform is provided with an adjusting component for placing the mirror to be measured, and is provided with a first upright post and a second upright post;

the measuring module comprises a rotating frame and an air floatation rotating table, the air floatation rotating table is rotatably arranged on the rotating frame, a first bearing seat is arranged on a first upright, a first rotating shaft is arranged in the first bearing seat, a second bearing seat is arranged on a second upright, a second rotating shaft is arranged in the second bearing seat, one end of the second rotating shaft is provided with a first angle encoder, one end of the rotating frame is arranged on the first upright through the first bearing seat, the other end of the rotating frame is arranged on the second upright through the second bearing seat, the rotating frame is pitching in a space between the first upright and the second upright, the air floatation rotating table is hinged with a swing arm through a switching assembly, the swing arm is connected with a non-contact measuring head, the swing arm and the non-contact measuring head are all positioned between the first upright and the second upright, the axes of a rotating shaft of the first rotating shaft, the second rotating shaft and the swing arm are in the same straight line, and the air floatation rotating table drives the non-contact measuring head scanning mirror through the swing arm to be measured.

In one embodiment of the invention, the switching assembly comprises an adapter plate and a fixed plate, wherein the fixed plate is arranged on the adapter plate, the adapter plate is arranged on one side of the air floatation turntable, a rotating arm shaft is rotatably arranged on the fixed plate, one end of the swing arm is sleeved on the rotating arm shaft, the other end of the swing arm is provided with the non-contact measuring head, and the non-contact measuring head is arranged vertically to the swing arm.

In one embodiment of the invention, the end of the swivel shaft is fitted with a second angle encoder.

In one embodiment of the invention, the other end of the swing arm is provided with a mounting hole for clamping the non-contact measuring head.

In one embodiment of the invention, the first rotating shaft is connected with a power source, the power source drives the rotating frame to rotate through the first rotating shaft, a bracket is arranged on the first upright post, and the power source is arranged on the bracket.

In one embodiment of the invention, the support platform is provided with a storage groove, a base plate and a connecting plate, the base plate is arranged on the storage groove, the adjusting component is arranged on the base plate, the adjusting component comprises a screw rod lifting table and a three-dimensional displacement table, an adjusting hole is formed in the base plate, the connecting plate is arranged in the adjusting hole in a penetrating mode, the screw rod lifting table is fixed to the connecting plate, the three-dimensional displacement table is arranged on the screw rod lifting table, a workpiece turntable is arranged on the three-dimensional displacement table, and the mirror to be measured is arranged on the workpiece turntable.

In one embodiment of the invention, when the non-contact measuring head is centered with the vertex of the mirror to be measured, the rotating shaft of the air-float turntable, the central shaft of the swing arm and the measuring axis of the non-contact measuring head are in the same plane.

A measurement method of a swing arm profiler for surface shape measurement using the swing arm profiler for surface shape measurement according to any one of the above embodiments, comprising the steps of:

s1, adjusting a swing arm of the swing arm type profiler to be in horizontal arrangement, wherein the non-contact measuring head and the swing arm are vertically arranged, the air floatation turntable is restored to an initial position, and a rotating shaft of the air floatation turntable, a central shaft of the swing arm and a measuring axis of the non-contact measuring head are coplanar and are positioned in the middle position of the first upright post and the second upright post;

s2: calculating a rotating frame inclination angle according to the initial surface shape parameter of the mirror to be measured, adjusting the pitch angle of the rotating frame to enable the indication value of the first angle encoder to be consistent with the rotating frame inclination angle, adjusting a swing arm which is horizontally arranged, and vertically arranging a non-contact measuring head and an adjusting component to enable the non-contact measuring head to be centered with the vertex of the mirror to be measured;

s3: and (2) in the adjusted state in the step (S2), driving the air-floating rotary table to enable the non-contact measuring head to rotate to the edge of one side of the mirror to be measured, driving the air-floating rotary table to rotate along the rotary shaft by a set angle, enabling the measuring point of the non-contact measuring head to sweep a contour line along the surface of the mirror to be measured, and stopping measuring when the measuring point scans to the edge of the other side of the mirror to be measured.

Compared with the prior art, the technical scheme of the invention has the following advantages:

according to the swing arm type profiler for surface shape measurement and the measurement method thereof, a first stand column and a second stand column are arranged on a supporting platform, one end of a rotating frame is arranged on the first stand column through a first bearing seat and a first rotating shaft, the second stand column is arranged on the other end of the rotating frame through a second bearing seat and a second rotating shaft, the rotating frame is arranged on the first stand column and the second stand column in a crossing mode, the rotating frame can be driven to rotate through rotating the first rotating shaft or the second rotating shaft, a first angle encoder can monitor the rotating angle of the rotating frame in real time, an air-float turntable is arranged on the rotating frame and is hinged with a swing arm through a switching assembly, a non-contact measuring head of the swing arm is used for measuring the distance between the top point of the mirror to be measured and the non-contact measuring head, and the axes of the first rotating shaft, the second rotating shaft and a rotating arm shaft of the swing arm in the swing arm type profiler are on the same straight line, and the air-float turntable drives the non-contact measuring head to scan the mirror to be measured, so that measurement is achieved. Specifically, during measurement, the rotating frame is rotated to a corresponding angle according to the mirror to be measured, and then the air-float turntable on the rotating frame is rotated, so that the integral pitching angle of the air-float turntable and the rotating frame can be freely adjusted, the surface shape measurement of the high, medium and low gradient optical elements can be covered, the non-contact measuring head with different measuring ranges and precision can be matched, the swing arm profiler can meet the requirements of the surface shape measurement of the aspheric surfaces in the stage from milling and grinding to rough polishing, the length of the swing arm is shorter, namely the influence of the deformation error of the swing arm on the measurement result is extremely small, the length is fixed, the adjustment is not needed, and the surface shape measurement of the middle and small caliber aspheric optical element with any curvature can be realized by only adjusting the inclination angle of the rotating frame once when measuring the different aspheric optical elements; in the measuring and calculating process, only one motion mechanism of the air floatation turntable is adopted, so that high-speed continuous measurement is easy to realize, the detection efficiency is high, the source of motion errors is single, and the measuring precision is improved.

Drawings

In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings.

FIG. 1 is a schematic diagram of a swing arm profiler for profile measurement according to the present invention;

FIG. 2 is a schematic view of a portion of a swing arm profiler according to the present invention;

FIG. 3 is a schematic view of the structure of an adjustment assembly in a swing arm profiler for profile measurement according to the present invention;

FIG. 4 is a schematic illustration of a convex aspherical mirror being measured in a swing arm profiler for profile measurement in accordance with the present invention;

FIG. 5 is a schematic illustration of a concave aspherical mirror being measured in a swing arm profiler for profile measurement in accordance with the present invention;

FIG. 6 is a schematic diagram of measurement parameters in the measurement method of the present invention;

FIG. 7 is a schematic illustration of calculating a maximum pivot angle in the measurement method of the present invention;

description of the specification reference numerals: 1. a support platform; 11. an adjustment assembly; 111. a connecting plate; 112. a backing plate; 1121. an adjustment aperture; 113. a first mounting plate; 114. a support plate; 115. a second mounting plate; 116. a screw rod; 117. a sliding seat; 118. a three-dimensional displacement table; 119. a workpiece turntable; 12. a mirror to be measured; 2. a measurement module; 21. a rotating frame; 22. an air-floating rotary table; 23. a first upright; 231. a first bearing seat; 232. a first rotating shaft; 24. a second upright; 241. a second bearing seat; 242. a second rotating shaft; 243. a first angle encoder; 25. a switching component; 251. an adapter plate; 252. a fixing plate; 253. a swivel arm shaft; 2531. a second angle encoder; 2532. a differentiating head; 26. swing arms; 261. a notch; 27. a non-contact probe; 3. a power source; 31. and (3) a bracket.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.

Referring to fig. 1-3, the present invention provides a swing arm profiler for surface shape measurement, which comprises a support platform 1 and a measurement module 2, wherein an adjusting component 11 for placing a mirror 12 to be measured is arranged on the support platform 1, and a first upright 23 and a second upright 24 are arranged on the support platform 1; the measuring module 2 comprises a rotating frame 21 and an air floatation rotating table 22, the air floatation rotating table 22 is rotatably arranged on the rotating frame 21, a first bearing seat 231 is arranged on a first upright post 23, a first rotating shaft 232 is arranged in the first bearing seat 231, a second bearing seat 241 is arranged on a second upright post 24, a second rotating shaft 242 is arranged in the second bearing seat 241, a first angle encoder 243 is arranged at one end of the second rotating shaft 242, one end of the rotating frame 21 is arranged on the first upright post 23 through the first bearing seat 231, the other end of the rotating frame 21 is arranged on the second upright post 24 through the second bearing seat 241, the rotating frame 21 is pitching in a space between the first upright post 23 and the second upright post 24, the air floatation rotating table 22 is hinged with a swinging arm 26 through a switching assembly 25, the swinging arm 26 is connected with a non-contact measuring head 27, the swinging arm 26 and the non-contact measuring head 27 are all located between the first upright post 23 and the second upright post 24, the axes of the first rotating shaft 232, the second rotating shaft 242 and the swinging arm 253 of the swinging arm 26 are on the same straight line, and the air floatation rotating table 22 drives the non-contact measuring head 27 to scan mirror 12 to be measured through the swinging arm 26.

The swing arm type profiler is provided with a first upright 23 and a second upright 24 on a supporting platform 1, the first upright 23 is provided with one end of a rotating frame 21 through a first bearing seat 231 and a first rotating shaft 232, the second upright 24 is provided with the other end of the rotating frame 21 through a second bearing seat 241 and a second rotating shaft 242, the rotating frame 21 is spanned on the first upright 23 and the second upright 24, the rotating frame 21 can be driven to rotate through rotating the first rotating shaft 232 or the second rotating shaft 242, a rotating angle of the rotating frame 21 can be monitored in real time by a first angle encoder 243, an air-float turntable 22 is arranged on the rotating frame 21, the air-float turntable 22 is hinged with a swing arm 26 through a switching assembly 25, a non-contact measuring head 27 of the swing arm 26 is used for measuring the distance between the vertex of a mirror 12 to be measured and the non-contact measuring head 27, according to the mirror 12 to be measured, the rotating frame 21 rotates to a corresponding angle, and then the air-floating rotary table 22 on the rotating frame 21 is rotated, because the air-floating rotary table 22 and the rotating frame 21 are positioned between the first upright 23 and the second upright 24, the integral pitching angle of the air-floating rotary table can be freely adjusted, the surface shape measurement of optical elements with high, medium and low steepness can be covered, the non-contact measuring head 27 with different measuring ranges and precision can be matched, the swing arm profiler can meet the requirements of the surface shape measurement of the aspherical surface in the stage from milling and grinding to rough polishing, the length of the swing arm 26 is shorter, namely the influence of the deformation error of the swing arm 26 on the measurement result is extremely small, the length is fixed, the adjustment is not needed, and the surface shape measurement of the medium and small caliber aspherical optical element with any curvature can be realized by adjusting the dip angle of the rotating frame 21 only once when measuring different aspherical optical elements; in the measuring and calculating process, only one motion mechanism of the air-float turntable 22 is adopted, so that high-speed continuous measurement is easy to realize, the detection efficiency is high, the source of motion errors is single, and the measuring precision is improved.

Wherein, supporting platform 1, first stand 23 and second stand 24 all adopt marble material, can reduce environmental vibration and temperature variation's influence to the device effectively through this setting. The first upright 23 and the second upright 24 play a role in supporting the rotating frame 21 and the air-float turntable 22, and when in installation, the rotating shaft of the air-float turntable 22 is required to be ensured to be always positioned on the middle plane between the first upright 23 and the second upright 24.

Further, the adapting assembly 25 includes an adapting plate 251 and a fixing plate 252, the fixing plate 252 is mounted on the adapting plate 251, the adapting plate 251 is disposed on one side of the air-floating turntable 22, a rotating arm shaft 253 is rotatably disposed on the fixing plate 252, one end of the swing arm 26 is sleeved on the rotating arm shaft 253, a non-contact measuring head 27 is mounted on the other end of the swing arm 26, and the non-contact measuring head 27 and the swing arm 26 are vertically arranged. In the process of rotating the air-float turntable 22, the adapter plate 251 fixedly connected with the air-float turntable 22 can drive the swing arm 26 and the non-contact measuring head 27 to rotate along with the swing arm, so that scanning can be realized, and a curve corresponding to the mirror 12 to be measured at the moment can be obtained. When the non-contact measuring head 27 is required to be centered with the vertex of the mirror 12 to be measured, the position of the non-contact measuring head 27 can be adjusted through the rotation of the rotating arm shaft 253, so that the measuring process is realized, and convenience and rapidness are realized.

Specifically, a second angle encoder 2531 and a differential head 2532 are mounted at the end of the swivel arm shaft 253, the second angle encoder 2531 is used for accurately detecting adjustment of the pitching angle of the swing arm 26, and the differential head 2532 is used for accurately detecting horizontal adjustment of the swing arm 26. The non-contact measuring head 27 is a non-contact displacement sensor measuring head, and the measuring axis of the displacement sensor measuring head is always perpendicular to the central axis of the swing arm 26, so as to avoid deviation of a measuring result caused by assembly errors, and a certain interval is reserved between the non-contact measuring head 27 and the mirror 12 to be measured, so that scratch risk of the measuring head to the mirror 12 to be measured in the measuring process is avoided.

Further, a mounting hole for clamping the non-contact measuring head 27 is formed in the other end of the swing arm 26, a notch 261 for adjustment is formed in one side of the mounting hole, the mounting hole is communicated with the notch 261, the non-contact measuring head 27 is mounted in the mounting hole, an adjusting bolt is arranged on the notch 261, and the adjusting bolt penetrates through the notch 261 to fix the non-contact measuring head 27 on the swing arm 26. According to the requirements of measuring the mirror 12 to be measured, the non-contact measuring head 27 with different measuring ranges and precision is matched, and the non-contact measuring head 27 in the swing arm profiler, namely the swing arm profiler, is replaced through the matching relation between the adjusting bolt and the notch 261, so that the requirements of measuring the aspheric surface shape from milling and grinding to rough polishing can be met.

In this embodiment, the first rotating shaft 232 is connected with the power source 3, the power source 3 drives the rotating frame 21 to rotate through the first rotating shaft 232, the first upright 23 is provided with the bracket 31, and the power source 3 is installed on the bracket 31. Preferably, the power source 3 is a worm gear reducer, and the worm gear reducer is suitable for the rotation requirement of the device, and can drive the first rotating shaft 232 to rotate so as to provide power for pitching of the air floatation turntable 22, so that the pitching angle of the air floatation turntable 22 is adjusted. In addition, the worm gear reducer has a self-locking function, and can stabilize the pitching state of the air floating turntable 22 by locking the rotation of the first rotating shaft 232, and prevent the air floating turntable 22 from falling down, wherein the central axes of the first rotating shaft 232 and the second rotating shaft 242 and the pitching angle adjusting axis of the air floating turntable 22 are ensured to coincide. Because the middle parts of the first upright post 23 and the second upright post 24 are not blocked, the air floatation turntable 22 can realize the free adjustment of the pitching angle around the central axes of the first rotating shaft 232 and the second rotating shaft 242 between the first upright post 23 and the second upright post 24, and can cover the surface shape measurement of the optical element with high, medium and low steepness.

The first angle encoder 243 is disposed at one end of the second rotating shaft 242, and the first angle encoder 243 can be used for accurately recording the rotation angles of the second rotating shaft 242 and the first rotating shaft 232, so as to accurately detect the pitching angle adjustment of the air-float turntable 22, specifically, the first angle encoder 243 is a high-resolution absolute angle encoder, and accurate monitoring can be realized.

Further, the initial position of the non-contact probe 27 is that the non-contact probe 27 is centered with the vertex of the mirror 12 to be measured, when the air-float turntable 22 rotates to the initial position, the rotation axis of the air-float turntable 22, the central axis of the swing arm 26 and the measuring axis of the non-contact probe 27 are in the same plane, the central lines of the first bearing seat 231, the second bearing seat 241, the driving shaft of the power source 3, the first rotating shaft 232 and the shaft or the hole of the second rotating shaft 242 are ensured to be concentric and horizontal, and the non-concentricity between the central axes or the holes of the parts not only can bring measuring errors to measurement, but also can make the rotation of the axes difficult and accelerate the abrasion of the installed contact surface.

In addition, be provided with on the supporting platform 1 and put thing groove, connecting plate 111 and backing plate 112, adjustment assembly 11 includes lead screw elevating platform and three-dimensional displacement platform 118, and backing plate 112 installs on putting the thing groove, and installs on supporting platform 1, has seted up regulation hole 1121 on the backing plate 112, and connecting plate 111 wears to establish with in the regulation hole 1121, and connecting plate 111 is fixed with the lead screw elevating platform, installs three-dimensional displacement platform 118 on the lead screw elevating platform, installs work piece revolving stage 119 on the three-dimensional displacement platform 118, and the mirror 12 that awaits measuring is installed on work piece revolving stage 119. Specifically, a first mounting plate 113 is mounted on one side of the backing plate 112 far away from the rotating frame 21, a supporting plate 114 is arranged on one side of the first mounting plate 113, one end of the supporting plate 114 is mounted on the backing plate 112, a second mounting plate 115 is arranged on the backing plate 112, a screw rod 116 is arranged between the first mounting plate 113 and the second mounting plate 115, a sliding seat 117 is sleeved on the screw rod 116, the sliding seat 117 is mounted on the connecting plate 111, a workpiece turntable 119 is mounted on the connecting plate 111 through a three-dimensional displacement table 118, and the mirror 12 to be measured is mounted on the workpiece turntable 119. After measuring a curve, the position of the screw 116 on the sliding seat 117 and the three-dimensional displacement table 118 can be adjusted to realize the position relationship between the mirror 12 to be measured and the non-contact measuring head 27.

Further, as shown in fig. 4 and 5, the swing arm profiler can measure concave aspherical mirrors, convex aspherical mirrors, and plane mirrors. The application range of the swing arm profiler covers the mirror surface with any curvature radius including the high-steepness (small curvature radius) aspheric surface.

The swing arm profiler can also be directly installed on one side of the mirror 12 to be measured, and the device of the machine tool for machining the mirror 12 to be measured is utilized to realize in-situ measurement. The length of the swing arm 26 is short, the influence of the deformation error of the swing arm 26 on the measurement result is very small, and the length of the swing arm 26 is fixed, so that the adjustment and calculation are easy; the air-float turntable 22 has wide pitching angle coverage range and can cover high, medium and low gradient optical mirror surface measurement; only one motion mechanism of the air-float turntable 22 is adopted, so that high-speed continuous measurement is easy to realize, the detection efficiency is high, and the motion error source is single; the measurement range can be conveniently expanded by replacing the swing arms 26 with different lengths, the surface shape measurement of the large-caliber aspheric surface can be realized, and the surface shape measurement of the large, medium and small-caliber aspheric surfaces can be measured, so that the universality is strong and the efficiency is high; through adjusting and matching the measuring heads with different measuring ranges and precision, the swing arm profiler can meet the aspheric surface shape measurement requirements from milling, grinding to rough polishing.

Example 2

The invention also provides a measuring method of the swing arm type profiler for measuring the surface shape, which uses the swing arm type profiler for measuring the surface shape, and comprises the following steps:

s1: the swing arm 26 of the swing arm type profiler is adjusted to be horizontally arranged, the non-contact measuring head 27 and the swing arm 26 are vertically arranged, the air floatation turntable 22 is restored to the initial position, the rotating shaft of the air floatation turntable 22, the central shaft of the swing arm 26 and the measuring axis of the non-contact measuring head 27 are coplanar, and the swing arm type profiler is positioned in the middle of the first upright 23 and the second upright 24;

s2: according to the initial surface shape parameters of the to-be-measured mirror 12, calculating a rotating inclination angle of the rotating frame 21, adjusting a pitch angle of the rotating frame 21 to enable an indication value of the first angle encoder 243 to be consistent with the calculated rotating inclination angle of the rotating frame 21, and adjusting the swing arm 26, wherein the swing arm 26 is horizontally arranged, the measuring axis of the non-contact measuring head 27 can be ensured to be perpendicular to the workpiece turntable 119 after the swing arm 26 is horizontally adjusted, the swing arm 26 and the non-contact measuring head 27 are always vertically arranged, and the adjusting assembly 11 is adjusted to enable the non-contact measuring head 27 to be centered with the vertex of the to-be-measured mirror 12;

s3: in the adjusted state in step S2, the air-floating turntable 22 is driven to rotate the non-contact measuring head 27 to the edge of one side of the mirror 12 to be measured, the air-floating turntable 22 is driven to rotate along the rotation axis by a set angle, the measuring point of the non-contact measuring head 27 is made to sweep a contour line along the surface of the mirror 12 to be measured, and the measurement is stopped when the measuring point is scanned to the edge of the other side of the mirror 12 to be measured.

Specifically, in step S2, the specific step of calculating the inclination angle of the turret 21 according to the initial surface shape parameter of the mirror 12 to be measured is as follows:

s21: calculating the closest spherical radius R of the mirror 12 to be measured _bfs ：

Wherein, the distance between the zero point of the non-contact measuring head 27 and the closest spherical surface of the lens to be measured cannot exceed the measuring range of the non-contact measuring head 27, if the measured distance exceeds the measuring range of the non-contact measuring head 27, the measurement cannot be realized, and the non-contact measuring head 27 with a larger measuring range needs to be replaced

The coordinates of any point on the aspherical surface of the mirror 12 to be measured are set as (r _i ,z _i ) The center coordinates closest to the sphere are (0, R) _bfs ) The amount of deviation of the aspherical surface from the closest spherical surface is:

wherein i=1, 2, 3 … …;

based on the least squares concept, calculateR is the minimum time _bfs To determine the closest aspheric surface, R is obtained by substituting the coordinates of the point on the aspheric surface, and solving the following equation _bfs ：

S22: as shown in fig. 6, according to the closest spherical radius R of the mirror under test 12 _bfs The distance a from the closest spherical vertex to the center line of the swing arm 26 and the effective length b of the swing arm 26 are calculated, and the inclination angle theta of the rotating frame 21 and the measuring arm length L are calculated, wherein the measuring arm length L is the distance from the vertex of the mirror 12 to be measured to the rotating shaft of the air-float turntable 22:

according to the closest spherical radius R of the mirror 12 to be measured _bfs Calculating the inclination angle theta of the rotating frame 21 and the arm length L:

L＝|a·sinθ-b·cosθ|

wherein a is the distance from the closest spherical vertex to the center line of the swing arm 26, and b is the effective length of the swing arm 26;

according to the calculated tilt angle θ of the rotating frame 21, the power source 3 is used to drive and adjust the tilt angle of the swing arm type profiler rotating frame 21, after the measured value of the first angle encoder 243 is consistent with the tilt angle θ of the rotating frame 21, the angle of the swing arm 26 is finely adjusted by the differential head to be horizontal, and the second angle encoder can accurately detect whether the adjustment is horizontal, and then the components in the adjusting component 11 of the supporting platform 1 are adjusted, so that the non-contact measuring head 27 is centered with the vertex of the mirror surface of the calibration mirror.

In this embodiment, after the adjustment of the swing arm profiler is completed, before measuring the mirror 12 to be measured, error calibration is performed on the system parameters of the swing arm profiler, which specifically includes the following steps:

selecting a proper calibration mirror corresponding to the vertex curvature radius according to the system parameters of the swing arm type profiler, placing the selected calibration mirror on a workpiece turntable 119 of the swing arm type profiler, and adjusting to center the non-contact measuring head 27 and the vertex of the calibration mirror, wherein the mirror surface height of the calibration mirror is positioned at the midpoint of the measuring range of the non-contact measuring head 27 as much as possible;

the calibration mirror is a mirror indicating the information of the surface shape parameters of the calibration mirror to be known, when the calibration mirror is selected, the curvature radius of the calibration mirror is as close as possible to the curvature radius of the vertex of the mirror 12 to be measured, the calibration mirror is used for measuring the known surface shape parameters of the calibration mirror, so that the structural parameter error is solved, the accurate and real structural parameters are obtained, the process is calibration (the structural parameters of the device are calibrated), and after the real structural parameters are obtained, the structural parameters are used for guiding the measuring process of the subsequent mirror 12 to be measured;

further, the maximum swing angle alpha required for measuring the calibration mirror is calculated

Wherein, as shown in FIG. 7, a coordinate (r, z) of the mirror edge point is calibrated;

driving the air-float turntable 22 to move so that the non-contact measuring head 27 moves to the edge of one side of the calibration mirror;

when the air-float turntable 22 rotates by a set angle, the measurement is automatically finished, the set angle is within the range of the maximum swing angle alpha, and the whole circle of rotation is not needed, so that the displacement value T measured by the non-contact measuring head 27 is obtained _i And the angle value alpha rotated by the air-floating rotary table 22 corresponding to the angle value alpha _i ；

Wherein, the non-contact measuring head 27 is moved to one side edge of the calibration mirror, and the air-float turntable 22 is controlled to scan and measure along the truncated line passing through the top point of the calibration mirror. The scanning result of the non-contact measuring head 27 is the difference between the closest spherical radius and the distance from the mirror surface measuring point of the mirror 12 to be measured to the closest spherical center.

Further, in the swing arm profiler adjusted as described above, that is, in the measurement result including the error, the displacement value T measured by the noncontact probe 27 is measured _i The deviation of the theoretical displacement value of the calibration mirror is the measurement deviation caused by the structural error, a system error parameter is obtained from the measurement deviation by utilizing an error separation algorithm, the system error parameter is compensated for the real structural parameter, and the measurement result of the aspherical mirror based on the real structural parameter is subjected to error compensation;

further, the distance a from the nearest spherical surface vertex of the calibration mirror to the center line of the swing arm 26, the effective length b of the swing arm 26, the inclination angle theta of the rotating frame 21 and the rotated angle value alpha of the air-bearing turntable 22 are utilized _i Constructing an offset function expression as T _i ＝f(a,b,θ,α _i )；

After the primary measurement is carried out on the calibration mirror, the deviation T of the result measured by the non-contact measuring head 27 is obtained _i And the angle value alpha rotated by the air-floating rotary table 22 corresponding to the angle value alpha _i Carry-in function expression T _i ＝f(a,b,θ,α _i ) The structural parameters a ', b', theta 'are obtained by nonlinear least square fitting calculation, and then the real mechanism parameters of the swing arm type profiler with the inclination angle of the rotating frame 21 adjusted at the moment are a', b ', theta';

the method belongs to relative position measurement, namely absolute accuracy of the inclination angle of the rotating frame 21 with the air flotation turntable 22 is not required, absolute level adjustment of the swing arm 26 is not required to be guaranteed, calibration of real parameters of a system is realized by using a measurement result in the calibration measurement process, error compensation is carried out on the measurement result by using a calibrated system structural parameter, errors such as the effective length of the swing arm 26, the inclination angle of the rotating frame 21 with the air flotation turntable 22 and the like are eliminated, measurement accuracy is improved, meanwhile, a related measuring instrument with extremely high accuracy is not required to be purchased, and measurement cost is reduced.

In step S3, in combination with the error calibration of the system parameters of the swing arm profiler, the specific steps for measuring the surface shape structure of the mirror 12 to be measured are as follows:

placing the mirror 12 to be measured on a workpiece turntable 119, and adjusting a screw lifting table and a three-dimensional displacement table 118 to center the non-contact measuring head 27 with the vertex of the mirror 12 to be measured;

driving the air-float turntable 22 to move so that the non-contact measuring head 27 moves to the edge of one side of the mirror 12 to be measured; when the air floatation turntable 22 rotates by a set angle, the measurement of the non-contact measuring head 27 is automatically ended, and a displacement value measured by the non-contact measuring head 27 and a rotating angle value of the turntable corresponding to the displacement value are obtained; the actual structural parameters in the process are a ', b ', theta ';

based on the structural parameters a ', b ', theta ', obtaining the surface shape curve of the mirror 12 to be measured relative to the nearest spherical surface by utilizing the angle value obtained by the non-contact measuring head 27 and the displacement value rotated by the rotary table corresponding to the angle value;

and (3) rotating the mirror 12 to be measured around the adjusting assembly 11 by a preset angle, returning to the step S21, adjusting the adjusting assembly 11 to center the non-contact measuring head 27 and the vertex of the mirror 12 to be measured until the mirror 12 to be measured rotates around the adjusting assembly 11 for one circle, and splicing the surface shape structures of the mirror 12 to be measured with a plurality of surface shape curves.

In the error calibration, the radius of curvature of the calibration mirror is selected to be as similar or identical to the radius of curvature of the vertex of the mirror 12 to be measured as possible, so that when the linear structure and the surface-shaped structure of the mirror 12 to be measured are measured, the closest spherical radius of the mirror 12 to be measured and the inclination angle of the rotating frame 21 with the air-floating turntable 22 are not required to be calculated again, the real and more accurate linear structure and the surface-shaped structure of the mirror 12 to be measured can be obtained, and the adjustment flow before measurement is effectively simplified. The ultra-precise components are not needed to be selected for selecting the angle encoder and the differential divider, the device cost is greatly reduced, and the obtained result is more precise.

When the mirror to be measured 12 is a spherical surface, a residual error of the surface shape is obtained, and when the mirror to be measured 12 is an aspherical surface, the deviation of the aspherical surface with respect to the spherical surface is obtained, and further, a difference is made between the theoretical surface shape of the aspherical surface and the residual error of the surface shape of the aspherical surface is obtained.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.

Claims (8)

1. A swing arm type profiler for surface shape measurement is characterized in that: comprising

The support platform is provided with an adjusting component for placing the mirror to be measured, and is provided with a first upright post and a second upright post;

the measuring module comprises a rotating frame and an air floatation rotating table, the air floatation rotating table is rotatably arranged on the rotating frame, a first bearing seat is arranged on a first upright, a first rotating shaft is arranged in the first bearing seat, a second bearing seat is arranged on a second upright, a second rotating shaft is arranged in the second bearing seat, one end of the second rotating shaft is provided with a first angle encoder, one end of the rotating frame is arranged on the first upright through the first bearing seat, the other end of the rotating frame is arranged on the second upright through the second bearing seat, the rotating frame is pitching in a space between the first upright and the second upright, the air floatation rotating table is hinged with a swing arm through a switching assembly, the swing arm is connected with a non-contact measuring head, the swing arm and the non-contact measuring head are both positioned between the first upright and the second upright, and the axes of a rotating arm shaft of the first rotating shaft, the second rotating shaft and the swing arm are in the same straight line, and the air floatation rotating table drives the non-contact measuring head scanning mirror through a to be measured.

2. The swing arm profiler for profile measurement as set forth in claim 1, wherein: the switching assembly comprises an adapter plate and a fixed plate, wherein the fixed plate is arranged on the adapter plate, the adapter plate is arranged on one side of the air floatation turntable, a rotating arm shaft is rotatably arranged on the fixed plate, one end of a swing arm is sleeved on the rotating arm shaft, the other end of the swing arm is provided with a non-contact measuring head, and the non-contact measuring head and the swing arm are vertically arranged.

3. The swing arm profiler for profile measurement as set forth in claim 2, wherein: the end of the swivel arm shaft is provided with a second angle encoder.

4. The swing arm profiler for profile measurement as set forth in claim 1, wherein: the other end of the swing arm is provided with a mounting hole for clamping the non-contact measuring head.

5. The swing arm profiler for profile measurement as set forth in claim 1, wherein: the first rotating shaft is connected with a power source, the power source drives the rotating frame to rotate through the first rotating shaft, a support is arranged on the first upright post, and the power source is installed on the support.

6. The swing arm profiler for profile measurement as set forth in claim 1, wherein: the support platform is provided with a storage groove, a base plate and a connecting plate, the base plate is installed on the storage groove, the adjusting assembly is installed on the base plate and comprises a screw lifting table and a three-dimensional displacement table, an adjusting hole is formed in the base plate, the connecting plate penetrates through the adjusting hole, the connecting plate is fixed with the screw lifting table, the three-dimensional displacement table is installed on the screw lifting table, a workpiece turntable is installed on the three-dimensional displacement table, and a mirror to be measured is installed on the workpiece turntable.

7. The swing arm profiler for profile measurement as set forth in claim 1, wherein: when the non-contact measuring head is centered with the vertex of the mirror to be measured, the rotating shaft of the air floatation turntable, the central shaft of the swing arm and the measuring axis of the non-contact measuring head are positioned in the same plane.

8. A measuring method of a swing arm type profiler for surface shape measurement is characterized by comprising the following steps of: measurement using a swing arm profiler for surface shape measurement according to any one of claims 1 to 7, comprising the steps of:

s1, adjusting a swing arm of the swing arm type profiler to be in horizontal arrangement, wherein the non-contact measuring head and the swing arm are vertically arranged, the air floatation turntable is restored to an initial position, and a rotating shaft of the air floatation turntable, a central shaft of the swing arm and a measuring axis of the non-contact measuring head are coplanar and are positioned in the middle position of the first upright post and the second upright post;

s2: calculating a rotating frame inclination angle according to the initial surface shape parameter of the mirror to be measured, adjusting the pitch angle of the rotating frame to enable the indication value of the first angle encoder to be consistent with the rotating frame inclination angle, adjusting the swing arm to enable the swing arm to be in horizontal arrangement, enabling the swing arm and the non-contact measuring head to be in vertical arrangement, and adjusting the adjusting assembly to enable the non-contact measuring head to be centered with the vertex of the mirror to be measured;

s3: and (2) in the adjusted state in the step (S2), driving the air-floating rotary table to enable the non-contact measuring head to rotate to the edge of one side of the mirror to be measured, driving the air-floating rotary table to rotate along the rotary shaft by a set angle, enabling the measuring point of the non-contact measuring head to sweep a contour line along the surface of the mirror to be measured, and stopping measuring when the measuring point scans to the edge of the other side of the mirror to be measured.