An ultra-precision optical measurement method

Abstract

The application discloses an ultra-precision optical measurement method, which comprises a rack, a laser system arranged on the rack, a probe system and a measurement platform system, the probe system comprises a probe and a Z-direction moving mechanism for moving the probe up and down, the measurement platform system comprises a measurement seat, an XY moving mechanism for moving the measurement seat along an X direction and a Y direction, the laser system comprises a laser emitter, a mirror group, a plurality of laser interferometers and a turning mirror, a floating rod capable of floating is arranged in the probe, a measurement ball is arranged at the bottom end of the floating rod, the measurement ball is in contact with a measured workpiece during measurement, and the roundness error compensation algorithm steps are as follows: S1, placing a standard ball on the measurement seat for measurement; S2, removing error parameters; S3, constructing a kinematics model; and S4, solving the surface form error of the standard ball through a non-spherical surface equation, so that the data obtained in the subsequent measurement process can be compensated through the surface form error, and thus accurate measurement values are obtained.

Description

Technical Field

[0001] The present invention relates to an optical measurement method, in particular to an ultra-precision optical measurement method. Background Art

[0002] In the ultra-precision machining production process, measurement is an important process. Whether the machined workpiece meets the requirements needs to be checked by measurement. However, for some workpieces with special shapes, the surface of the workpiece is an aspherical free-form surface. If ordinary measuring equipment (such as micrometer measurement, etc.) is used for manual measurement, not only is the measurement process time-consuming but the measurement accuracy is also difficult to meet the requirements. Therefore, the applicant uses the currently advanced laser system to design an ultra-precision optical measuring machine for precision measurement, and designs a corresponding measurement method based on the structural principle of the measuring machine.

[0003] However, during the measurement process of the above method, the stylus ball at the end of the floating rod contacts the surface of the workpiece being measured. Since the end of the floating rod is spherical, the roundness error of the spherical shape will affect the final measurement result. Therefore, before the test, it is necessary to use a standard ball with very high dimensional accuracy to perform the measurement, calculate the roundness error of the stylus ball, and then compensate for it in the subsequent measurement of the workpiece, thereby improving the measurement accuracy. Therefore, the applicant has proposed a stylus roundness error compensation algorithm to calculate the roundness error of the stylus ball. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides an ultra-precision optical measurement method.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] 1. An ultra-precision optical measurement method, comprising a frame, a laser system mounted on the frame, a probe system, and a measuring platform system. The probe system comprises a probe, a Z-direction movement mechanism for moving the probe up and down, and two capacitive sensors for measuring the straightness of the probe during vertical up and down movement. The measuring platform system comprises a measuring base, an XY movement mechanism for moving the measuring base in the X and Y directions, and a three-capacitive sensor for measuring the offset error in the Z direction when the measuring base moves in the X or Y direction. The laser system comprises a laser emitter, a reflector assembly, several laser interferometers, and a deflection mirror. The reflector assembly comprises a first reflector mounted on the probe and a second reflector mounted on a floating rod. , reflector three and reflector four on the measuring seat, the laser emitted by the laser transmitter reaches each of the laser interferometers after passing through the deflection mirror, reflector one, reflector two, reflector three and reflector four each correspond to a matching laser interferometer, and the laser interferometer irradiates the reflector one, reflector two, reflector three and reflector four and can reflect the laser back to the corresponding laser interferometer, the probe is provided with a floating rod that can float and a measuring ball installed at the bottom end of the floating rod, and the measuring ball is in contact with the workpiece to be measured during measurement, the laser interferometer corresponding to reflector one can obtain the displacement parameter z of the probe moving along the Z direction; the laser interferometer corresponding to reflector two can obtain the displacement parameter Z of the floating rod moving along the Z direction d The laser interferometer corresponding to the third reflector can obtain the displacement parameter x of the measuring base moving along the X direction; the laser interferometer corresponding to the fourth reflector can obtain the displacement parameter y of the measuring base moving along the Y direction; the third capacitive sensor can obtain the straightness change parameter Z1 of the measuring base moving along the X direction or the Y direction, and the first capacitive sensor can obtain the straightness change parameter Z when the probe moves in the Z direction. x The second capacitive sensor can obtain the straightness change parameter Z when the probe moves in the Z direction and deviates in the Y direction. y , the steps of the roundness error compensation algorithm of the measuring ball are as follows:

[0007] S1: Place the standard ball on the measuring seat for measurement, obtain the measurement data of each laser interferometer, and remove the straightness change parameter Z when the probe moves in the Z direction and deviates in the X direction. x Or the straightness change parameter Z offset in the Y direction y , eliminate the offset error parameter Z1 in the Z direction when the measuring base moves along the X direction or Y direction, so as to obtain the actual measurement value (x1, z1). Formula 1 is as follows:

[0008] x1=xZ x

[0009] z1=z-Z1+Z d

[0010] S2: Assuming the radius of the stylus ball is r, and the tangent angle between the stylus ball and the ideal curve on the spherical surface of the standard sphere is α, the coordinates (x′, z′) of the contact point on the ideal surface can be obtained from the formula. Formula 2 is as follows:

[0011]

[0012] S3: Construct the following kinematic model. Formula 3 is as follows:

[0013]

[0014] β in formula 3 is the rotation error of the standard ball along the Y axis during measurement, t z is the offset error of the standard ball along the Z direction. The floating rod is provided with a probe, and the measuring ball is located at the bottom end of the probe. θ is the perpendicularity error between the probe and the X or Y axis when the probe moves along the Z axis. (x′, z′) is the actual measurement value in step S2, and (x2, z2) is the final measurement result.

[0015] S4: Solve the surface error of the standard sphere. Formula 4 is as follows:

[0016] e(θ,β,t z )=z2-Z(x2).

[0017] The probe includes an outer cylinder and an inner cylinder located in the outer cylinder, the floating rod is provided in the inner cylinder, and an air flotation structure is provided on the outer cylinder and the inner cylinder. The floating rod can float in the inner hole of the inner cylinder through the air flotation structure, and a restriction structure for limiting the rotation of the floating rod and a positioning structure for supporting the floating rod are provided between the floating rod and the inner cylinder.

[0018] The air flotation structure includes an outer air inlet hole provided on the outer cylinder, an annular air channel provided on the inner cylinder, and a plurality of inner air inlet holes provided in the annular air channel. The outer air inlet hole is communicated with the annular air channel, and the inner air inlet hole is communicated with the inner hole.

[0019] The limiting structure includes limiting posts that are arranged opposite to each other, and the end of the reference plate is located between two corresponding limiting posts.

[0020] It also includes a connecting flange, the bottom end of which is provided with two elastic rings and a clamp for locking the two elastic rings, the end of the outer tube is located in the two elastic rings and is fixed to the connecting flange by the elastic rings, the connecting flange includes a flange plate and a connecting tube, a horizontal slit and a vertical slit are cut on the connecting tube, one end of the vertical slit is connected to the horizontal slit, and the other end of the vertical slit is connected to the outside world, and the elastic ring is formed by dividing the horizontal slit and the vertical slit.

[0021] It also includes a probe lifting mechanism, which includes a lifting movable plate, a lifting air flotation guide rail and a lifting motor. The lifting motor is connected to the lifting air flotation guide rail, the lifting movable plate is installed on the lifting air flotation guide rail, and the connecting flange is connected to the lifting movable plate.

[0022] A lens adjustment mechanism is provided between the connecting flange and the lifting movable plate. The lens adjustment mechanism includes an adjustment spring, a plurality of adjustment screw holes provided on the connecting flange, and an adjustment screw matched with the adjustment screw holes. One end of the adjustment spring is against the connecting flange and the other end is against the lifting movable plate.

[0023] The beneficial effect of the present invention is that: based on the standard sphere, the present invention proposes a probe roundness error compensation algorithm for a contour measuring device to calculate the surface error of the standard sphere, so that in the subsequent measurement process, the measured data can be compensated by the surface error to obtain an accurate measurement value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] Figure 1 It is an overall structural view of the present invention;

[0026] Figure 2 This is a structural view of the part behind the hidden metal frame;

[0027] Figure 3 This is a structural view of the part in the other direction behind the hidden metal frame;

[0028] Figure 4 It is a structural view that hides the metal rack, marble table, and marble slabs.

[0029] Figure 5 It is the structural view of the probe;

[0030] Figure 6 It is a cross-sectional structural view of the probe;

[0031] Figure 7 This is a view of the internal structure of the probe;

[0032] Figure 8 Structural view of the connecting flange;

[0033] Figure 9 This is a structural view of the measuring seat;

[0034] Figure 10 This is the structural view of the measuring seat from another direction;

[0035] Figure 11 This is the exploded structural view of the lower seat plate and the upper seat plate;

[0036] Figure 12 This is a structural view of the lower seat plate and the upper seat plate exploded from another direction.

[0037] Figure 13 It is a schematic view of the algorithm principle. DETAILED DESCRIPTION

[0038] The advantages and features of the present disclosure and its implementation methods will be illustrated by the following embodiments described with reference to the accompanying drawings. However, the present disclosure can be embodied in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be comprehensive and complete and will fully convey the scope of the present disclosure to those skilled in the art. Furthermore, the present disclosure is limited only by the scope of the claims.

[0039] The shapes, sizes, proportions, angles and numbers disclosed in the drawings for describing the embodiments of the present disclosure are merely examples, and therefore the present disclosure is not limited to the details shown. Throughout this specification, the same reference numerals refer to the same elements. In the following description, when a detailed description of a related known function or configuration is determined to be unnecessary to obscure the focus of the present disclosure, the detailed description will be omitted. Where “including”, “having” and “comprising” described in this specification are used, other components may be added unless “only” is used. Unless otherwise indicated, terms in the singular may include plural forms.

[0040] When explaining an element, although not explicitly described, the element is understood to include a range of error.

[0041] When describing a positional relationship, for example, when the positional relationship is described as "on," "above," "below," and "adjacent to," one or more parts may be arranged between two other parts, unless "immediately" or "directly" is used.

[0042] When describing a temporal relationship, for example, when a temporal order is described as “after,” “subsequently,” “next,” and “before,” discontinuous cases may be included unless “just” or “directly” is used.

[0043] It should be understood that although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from other elements. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of this disclosure.

[0044] As will be fully appreciated by those skilled in the art, the features of the different embodiments of the present disclosure may be coupled or combined with each other in part or in whole, and may cooperate with each other in various ways and be driven technically. The embodiments of the present disclosure may be performed independently of each other, or may be performed together in a mutually dependent relationship.

[0045] Reference Figures 1 to 4 The present invention discloses an ultra-precision optical measurement method. The structure of the equipment relied on by this method includes: a frame 100, a laser system 200 arranged on the frame 100, a probe system and a measuring platform system. The probe system includes a probe 300 and a Z-direction moving mechanism that drives the probe to move up and down. The measuring platform system includes a measuring base 400 and an XY moving mechanism that drives the measuring base to move in the X and Y directions. The frame 100 of the present application includes three parts: a metal frame 101 at the bottom, a marble table 102 arranged on the metal frame 101, and a marble plate 103 vertically arranged on the marble table 102. Such a structure can minimize the impact of deformation of the frame 100 on measurement. A workpiece to be measured (not shown in the figure) is placed on the measuring base 400. The measuring base 400 drives the workpiece to be measured to move left and right and forward and backward so that different positions on the workpiece surface contact the stylus 700 in the probe 300. The stylus 700 moves up and down as the height of different positions on the workpiece surface changes.

[0046] The laser system includes a laser emitter, a reflector group, several laser interferometers and a deflection mirror. The reflector group includes a reflector 1 500 mounted on the probe 300. The reflector 1 500 of the present application is preferably mounted on a slider of a lifting air-floating guide rail fixed as a whole with the probe 300 through a bracket. The probe 300 is mounted on the frame 100 through the lifting air-floating guide rail. The reflector 2 501 on the floating rod, the reflector 3 502 and the reflector 4 503 on the measuring seat, the laser emitted by the laser emitter reaches each of the laser interferometers after passing through the deflection mirror, the reflector 1 500, the reflector 2 501, Reflector three 502 and reflector four 503 each correspond to a matching laser interferometer, and the laser irradiated by the laser interferometer onto reflector one 500, reflector two 501, reflector three 502 and reflector four 503 can be reflected back to the corresponding laser interferometer. The laser is emitted by the laser transmitter and reaches each laser interferometer after passing through each turning mirror. Each laser interferometer calculates the light beam reflected back by its own reflector, so the displacement change can be fed back to the laser system 200 through the laser beam to obtain the displacement change of each displacement axis and the measurement value of the probe, and finally the precise size data of the workpiece surface is calculated. Of course, the laser system 200 in this application is a product of the existing technology purchased from outside, so its specific structure and principle are not described in detail.

[0047] like Figures 5 to 8As shown, the probe 300 includes an outer cylinder 1 and an inner cylinder 2 located in the outer cylinder 1. The outer cylinder 1 and the inner cylinder 2 are both cylindrical cylinders. There is a mounting hole in the outer cylinder 1, and the inner cylinder 2 is located in the mounting hole. The outer cylinder 1 and the inner cylinder 2 can be fixed as a whole by pins. A floating rod 3 is provided in the inner cylinder 2. The floating rod 3 is a cylindrical rod and is made of a lightweight magnesium alloy, so as to minimize the contact pressure during measurement. Of course, a probe 701 is provided on the floating rod 3. The end face of the probe 701 contacts the workpiece to be measured. The bottom end of the probe 701 is provided with the stylus 700. When the measuring seat 400 moves, the floating rod has a slight rise and fall change with the height change of the workpiece surface. A second reflector 501 is installed on the floating rod 3. The second reflector 501 is generally installed on the floating rod 3 by gluing. When the laser of the laser system 200 irradiates the second reflector 501, the second reflector 501 will reflect the laser beam back Laser system 200, laser system 200 calculates through the reflected laser beam data, and can know the precise size data of the workpiece surface. Of course, laser system 200 and reflector 2 501 are purchased equipment, and are not components of this structure. Therefore, their specific structure and principle are not described in detail. The probe 300 structure adopts a combination of air flotation structure and laser detection for precise measurement. The floating rod of the probe 300 structure can float in the inner hole of the inner cylinder through the air flotation structure, thereby greatly avoiding the interference of friction resistance. The outer cylinder 1 and the inner cylinder 2 are provided with an air flotation structure. The floating rod 3 can float in the inner hole of the inner cylinder 2 through the air flotation structure, and a limiting structure for limiting the rotation of the floating rod 3 and a positioning structure for supporting the floating rod 3 are provided between the floating rod 3 and the inner cylinder 2. Of course, in this application, the position of the floating rod 3 when it contacts the positioning structure is the reference position for measurement, which is convenient for subsequent calculations.

[0048] As shown in the figure, the air flotation structure includes an external air inlet hole (not shown in the figure) arranged on the outer tube 1, an annular air channel 4 arranged on the inner tube 2, and a plurality of internal air inlet holes 5 arranged in the annular air channel 4. The internal air inlet holes 5 are evenly arranged around the inner hole of the inner tube 2. The external air inlet hole is connected to the annular air channel 4, and the internal air inlet hole 5 is connected to the inner hole. The external air inlet hole is connected to the external compressed air source through an air joint and an air pipe. The high-pressure gas enters the annular air channel 4 from the external air inlet hole, and then enters the internal air inlet hole 5. In this way, a multi-point air intake structure can be formed in the inner hole of the inner tube 2, and the annular air channel 4 is provided with two upper and lower ones. Of course, an external air channel connected to the annular air channel 4 is provided on the outer tube 1, and the external air inlet hole is connected to the external air channel, so that a relatively uniform high-pressure air film is formed in the inner hole, which helps to prevent eccentric micro-movement of the floating rod 3, thereby improving the measurement accuracy. As a further preferred structure, the inner air inlet hole 5 is a tapered hole, and the aperture gradually decreases from the air inlet end hole of the inner air inlet hole 5 to the air outlet end hole of the inner air inlet hole 5. By reducing the aperture, we can gradually increase the pressure of the gas entering the inner hole of the inner tube 2, thereby forming an air film with higher pressure, which helps to prevent eccentric micro-movement of the floating rod 3, thereby improving the measurement accuracy.

[0049] As shown in the figure, the positioning structure includes a reference plate 6 fixed on the floating rod 3 and a reference ball 7 arranged on the inner tube 2. The reference plate 6 is also a magnesium alloy plate and is relatively thin. Both ends of the reference plate 6 can contact with the reference ball 7 to support the floating rod 3. The reference ball 7 is a steel ball. The position where the reference plate 6 contacts the steel ball is the reference point position. The limiting structure includes relatively arranged limit columns 8. The end of the reference plate 6 is located between the two corresponding limit columns 8. The limit columns 8 are made of ceramic and have a very smooth surface. The reference plate 6 can prevent the floating rod 3 from rotating and affecting the accuracy through the action of the limit columns 8, and the smooth surface of the ceramic can avoid affecting the lifting and lowering of the floating rod 3. Moreover, the limit columns 8 cooperate with the reference ball 7 to make the reference plate 6 contact with the reference ball 7 horizontally.

[0050] As shown in the figure, a connecting screw hole is provided in the floating rod 3, and a connecting thread that cooperates with the connecting screw hole is provided at the end of the probe 701. In this way, the probe 701 is convenient to install and disassemble, and is convenient for later replacement. Furthermore, a weight-reducing hole that passes through the connecting screw hole is provided on the floating rod 3. The floating rod 3 requires a lightweight design, which is conducive to improving measurement accuracy.

[0051] As a preferred structure, an end plate 9 is provided at the end of the floating rod 3, and a plate hole is provided between the end plate 9 and the floating rod 3. The reference plate 6 is fixed to the end plate 9 through the plate hole. Because the weight-reducing hole just passes through the plate hole, and the reference plate 6 is also fixed by bonding. In this way, the contact area between the reference plate 6 and the end face of the floating rod 3 is small, so the reference plate 6 and the end plate 9 are bonded as one. Of course, the end plate 9 is also made of magnesium alloy and is bonded as one with the floating rod 3.

[0052] As shown in the figure, it also includes a connecting flange, and the outer cylinder 1 is connected to the Z-direction moving mechanism through the connecting flange. Two elastic rings 11 are provided at the bottom end of the connecting flange. The end of the outer cylinder 1 is located in the two elastic rings 11 and is fixed to the connecting flange by the elastic rings 11, and the elastic ring 11 is locked by the clamp 12. The clamp 12 is a purchased part. The above structure is simple and easy to assemble and disassemble, so that it is easy to realize the maintenance and replacement of the probe 701 structure in the later stage. The specific structure of the connecting flange of the present application is: it includes a flange plate 14 and a connecting cylinder 15, and an annular transverse slit 16 and a vertical slit 13 are cut on the connecting cylinder 15. One end of the vertical slit 13 is connected to the transverse slit 16, and the other end of the vertical slit 13 is connected to the outside world. The elastic ring 11 is formed by the division of the transverse slit 16 and the vertical slit 13. The above structure is simple to process and has low cost.

[0053] As shown in the figure, as a further structure, a Z-axis movement mechanism is also included. The Z-axis movement mechanism is mounted on the marble slab 103 on the frame 100. The Z-axis movement mechanism includes a lifting plate 19, a lifting air-floating guide rail, and a lifting motor. The lifting motor is connected to the lifting air-floating guide rail. The lifting plate 19 is mounted on the lifting air-floating guide rail. The connecting flange is connected to the lifting plate 19. Through the above structure, the inner cylinder 2 and the outer cylinder 1 can make compensatory corresponding movements with the movement of the floating rod 3. Because the pressure of the air film formed around the floating rod 3 in the inner cylinder 2 is not absolutely uniform, when the floating rod 3 moves and rises during the measurement process, the pressure of the air film on the floating rod 3 will vary, affecting the measurement accuracy. Therefore, to ensure that the pressure of the air film on the floating rod 3 is consistent during the measurement process, the Z-axis movement mechanism will follow the data changes of the probe 701 in real time and make compensatory corresponding movements with the movement of the probe 701. This ensures that the position of the probe 701 and the floating rod 3 relative to the inner cylinder 2 and the outer cylinder 1 remains unchanged, thereby ensuring that the measurement position and the contact pressure during the measurement remain unchanged. Thereby improving the measurement accuracy, the above-mentioned lifting motor can be a linear servo motor. Of course, the lifting motor and the lifting air-floating guide rail are existing technology products, so the specific structure and connection relationship are not described in detail.

[0054] As shown in the figure, the connecting flange and the lifting moving plate 19 are provided with a lens adjusting mechanism, which is used for adjusting the angle of the reflecting mirror two 501. The lens adjusting mechanism comprises adjusting springs (not shown in the figure), a plurality of adjusting screw holes provided on the connecting flange, and adjusting screw rods 20 matched with the adjusting screw holes. In the application, there are three adjusting screw holes and three adjusting screw rods 20, which are uniformly arranged around the inner cylinder 2. The adjusting screw rod 20 can be in contact with the lifting moving plate 19, so as to control the relative angle between the connecting flange and the lifting moving plate 19. After adjustment, the connecting flange and the lifting moving plate 19 are locked by screws to keep the angle. In order to facilitate adjustment, the adjusting spring is in contact with the connecting flange at one end and in contact with the lifting moving plate 19 at the other end, so that the adjustment is more convenient and accurate.

[0055] As shown in the figure, as shown in 9 to Figure 12 As shown in the figure, the measuring seat 400 comprises a measuring seat driving mechanism 21, a lower seat plate 22 and an upper seat plate 23. The lower seat plate 22 and the upper seat plate 23 are driven to move by the measuring seat driving mechanism 21, so that the measured workpiece placed on the upper seat plate 23 can realize forward and backward movement. The measuring seat driving mechanism 21 is a product of the prior art, which mainly comprises two sets of servo motors and two sets of precision air floating guide rails, and can realize one-way movement in the X direction or the Y direction, or planar movement in the X direction and the Y direction. The servo motor and the air floating guide rail are both prior art, and thus their specific structures and mounting modes are not described in detail.

[0056] As shown in the figure, the reflecting mirror three 502 and the reflecting mirror four 503 are located on the upper seat plate 23. In order to facilitate installation, the upper seat plate 23 is provided with mirror seats 25, and the reflecting mirror three 502 and the reflecting mirror four 503 are installed on the corresponding mirror seats 25. The upper seat plate 23 and the lower seat plate 22 are provided with adjusting structures, and the reflecting mirror three 502 and the reflecting mirror four 503 can be perpendicular to the laser beam irradiated by the laser system 200 on the reflecting mirror through the adjustment of the corresponding adjusting structures. In the above structure, the precision driving mechanism comprises two servo motors and two sets of precision air floating guide rails, which can realize one-way movement in the X direction or the Y direction, or planar movement in the X direction and the Y direction. The servo motor and the air floating guide rail are both prior art, and thus their specific structures and mounting modes are not described in detail. Of course, the laser system 200 is also a purchased equipment, and thus the specific structure and mounting mode of the laser system 200 are not described in detail.

[0057] As shown in the figure, the adjustment structure includes at least three adjusting screws (not shown in the figure), and three are preferred in this application. The adjusting screws are threadedly connected to the upper seat plate 23. Of course, there are adjusting screw holes 26 on the upper seat plate that cooperate with the adjusting screws. The adjusting screws can be abutted against the lower seat plate 22 to achieve position angle adjustment of the upper seat plate 23. The three adjusting screws are evenly arranged around the center of the upper seat plate 23. By screwing in the adjusting screws, they abut against the lower seat plate 22, thereby lifting the corresponding side of the upper seat plate 23 to achieve adjustment of the angular position of the upper seat plate 23, so that the reflector is perpendicular to the laser beam to ensure accurate measurement. After the adjustment is completed, the upper seat plate 23 and the lower seat plate 22 are locked by a locking member, which is also a screw.

[0058] As shown in the figure, the upper seat plate 23 is provided with a positioning groove 27, and the lower seat plate 22 is provided with a positioning platform 28 that can be located in the positioning groove 27. The adjusting screw can be offset against the positioning platform 28. Through the cooperation of the positioning platform 28 and the positioning groove 27, we can achieve preliminary positioning during assembly. In this application, the positioning groove 27 is preferably a cylindrical groove, and the positioning platform 28 is a cylindrical platform, and the diameter of the positioning groove 27 is slightly larger than the positioning platform 28. The two can be loosely fitted, and the height value of the cylindrical platform is also larger than the depth value of the positioning groove 27. In this way, there is a gap between the upper seat plate 23 and the lower seat plate 22, so that there is adjustment space. As a preferred structure, three positioning holes are provided on the positioning platform 28 (not shown in the figure), and the end of the adjusting screw is located in the positioning hole, so that the adjusting screw will not shift during adjustment and after the adjustment is completed, thereby ensuring the adjustment accuracy.

[0059] As shown in the figure, a number of steel balls 29 are arranged between the upper seat plate 23 and the lower seat plate 22. The steel balls 29 are arranged around the positioning platform 28, and the steel balls 29 are fixed by clamping the upper seat plate 23 and the lower seat plate 22. With the support of the steel balls 29, we can more easily adjust the angle of the upper seat plate 23, and the contact between the steel balls 29 and the upper seat plate 23 and the lower seat plate 22 is always point contact, so it does not affect the adjustment of the upper seat plate 23, and after the upper seat plate 23 and the lower seat plate 22 are locked, the suspended area of ​​the upper seat plate 23 is supported and is not easy to bend and deform.

[0060] As a further structure, the lower seat plate 22 is provided with a plurality of lower pads 30, and the lower pads 30 are provided with positioning grooves 27. The upper seat plate 23 is provided with a plurality of upper pads 31. The steel balls 29 are located in the corresponding positioning grooves 27 and are fixed by clamping the upper pads 31 and the lower pads 30. The positioning grooves 27 not only facilitate the installation and positioning of the steel balls 29 during assembly, but also facilitate processing through the setting of the pads.

[0061] As a further structure, an upper groove 32 is provided on the upper seat plate 23 , and the pad and the steel ball 29 are located in the corresponding upper groove 32 , which can reduce the thickness of the measuring seat 400 as a whole.

[0062] In summary, the probe 300 and the measuring base 400 are specially designed for precision measurement. The floating rod of the probe 300 structure can float in the inner hole of the inner cylinder through the air flotation structure, thereby greatly avoiding the interference of friction resistance. A reflector is installed on the floating rod, and the reflector is used in conjunction with the laser system 200, so that the slightest lifting and lowering changes of the floating rod can be detected and calculated by the laser system 200, thereby achieving precise measurement; the measuring base 400 includes a lower seat plate and an upper seat plate, and the upper seat plate is provided with a reflector. An adjustment structure is provided between the upper seat plate and the lower seat plate, and the reflector can be precisely matched with the laser system 200 through adjustment of the adjustment structure, so that the measuring base 400 is well adapted to the laser system 200, thereby achieving precise measurement of the workpiece.

[0063] In order to obtain deviation data, the device is also equipped with a capacitive sensor 1 600 and a capacitive sensor 2 601 for measuring the straightness of the probe when it moves vertically up and down, and a capacitive sensor 3 602 for measuring the offset error in the Z direction when the measuring base moves along the X direction or the Y direction. During measurement, the measuring ball 700 is in contact with the workpiece being measured. The laser interferometer corresponding to the reflector 1 500 can obtain the displacement parameter z of the probe moving along the Z direction; the laser interferometer corresponding to the reflector 2 501 can obtain the displacement parameter Z of the floating rod moving along the Z direction. d The laser interferometer corresponding to the third reflector 502 can obtain the displacement parameter x of the measuring base moving along the X direction; the laser interferometer corresponding to the fourth reflector 503 can obtain the displacement parameter y of the measuring base moving along the Y direction; the third capacitive sensor 602 can obtain the straightness change parameter Z1 of the measuring base moving along the X direction or the Y direction, and the first capacitive sensor 600 can obtain the straightness change parameter Z when the probe moves in the Z direction. x The second capacitive sensor 601 can obtain the straightness change parameter Z when the probe moves in the Z direction and deviates in the Y direction. y , the steps of the roundness error compensation algorithm of the measuring ball are as follows:

[0064] like Figure 13 As shown,

[0065] S1: Place the standard ball 800 on the measuring seat for measurement. First, a busbar of the standard ball 800 needs to be measured. During the busbar measurement process, the stylus ball 700 moves in contact with the surface of the standard ball 800. The measurement data is obtained through various laser interferometers and capacitive sensors. At this time, the straightness change parameter Z that is offset in the X direction when the stylus moves in the Z direction is eliminated. xOr the straightness change parameter Z offset in the Y direction y , eliminate the offset error parameter Z1 in the Z direction when the measuring base moves along the X direction or Y direction, so as to obtain the actual measurement value (x1, z1). Formula 1 is as follows:

[0066] x1=xZ x

[0067] z1=z-Z1+Z d

[0068] S2: In step S1, the actual motion trajectory L of the stylus ball 700 is the trajectory change of the center of the stylus ball 700. Therefore, the radius error of the stylus ball 700 needs to be eliminated from the measured data. Assuming that the radius of the stylus ball 700 is r, and the tangent angle of the contact point between the stylus ball 700 and the ideal curve on the spherical surface of the standard sphere 800 is α, the coordinates (x′, z′) of the contact point on the ideal curve can be obtained from the formula. Formula 2 is as follows:

[0069]

[0070] S3: The measured value of step S2 couples the verticality error during the measurement process, the posture error of the object being measured, the contour error of the standard sphere 800, and the roundness error of the probe. Since the contour accuracy of the standard sphere 800 is very high, the effect on the measurement result is very small and can be ignored. When there is a verticality error between the probe and the XY reference plane, the measurement point will deviate from the theoretical point, causing a fundamental error in the measurement. For the one-dimensional standard sphere 800, the curvature of the entire surface is equal everywhere, so the displacement along the XY direction can be ignored when solving the posture error. As long as the tilt error and the offset error along the Z direction are included, the following kinematic model is constructed. Formula 3 is as follows:

[0071]

[0072] β in formula 3 is the rotation error of the standard ball 800 along the Y axis during measurement, t z is the offset error of the standard ball 800 along the Z direction, θ is the perpendicularity error between the probe and the X or Y axis when the probe moves along the Z axis, (x′, z′) is the actual measurement value in step S2, and (x2, z2) is the final measurement result.

[0073] S4: Solve the surface error of the standard sphere 800, formula 4 is as follows:

[0074] e(θ,β,t z )=z2-Z(x2)

[0075] Z(x2) is the aspheric surface equation. In order to minimize the measurement error, the least square method can be used to optimize the above equation to solve the surface error e(θ, β, tz ), since the error of the standard sphere 800 mentioned above has been ignored, the error at this time is the roundness error of the stylus 700. In the subsequent measurement process, the measured data will be compensated by the surface error to obtain accurate measurement values.

[0076] The above is a detailed introduction to an ultra-precision optical measurement method provided by an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An ultra-precision optical measurement method, comprising a frame, a laser system mounted on the frame, a probe system, and a measuring platform system. The probe system comprises a probe, a Z-direction movement mechanism for moving the probe up and down, and two capacitive sensors for measuring the straightness of the probe during vertical up and down movement. The measuring platform system comprises a measuring base, an XY movement mechanism for moving the measuring base in the X and Y directions, and a three-capacitive sensor for measuring the offset error in the Z direction when the measuring base moves in the X or Y direction. The laser system comprises a laser emitter, a reflector assembly, several laser interferometers, and a deflection mirror. The reflector assembly comprises a first reflector mounted on the probe and a second reflector mounted on a floating rod. , reflector three and reflector four on the measuring seat, the laser emitted by the laser transmitter reaches each of the laser interferometers after passing through the deflection mirror, reflector one, reflector two, reflector three and reflector four each correspond to a matching laser interferometer, and the laser interferometer irradiates the reflector one, reflector two, reflector three and reflector four and can reflect the laser back to the corresponding laser interferometer, the probe is provided with a floating rod that can float and a measuring ball installed at the bottom end of the floating rod, and the measuring ball is in contact with the workpiece to be measured during measurement, the laser interferometer corresponding to reflector one can obtain the displacement parameter z of the probe moving along the Z direction; the laser interferometer corresponding to reflector two can obtain the displacement parameter Z of the floating rod moving along the Z direction d The laser interferometer corresponding to the third reflector can obtain the displacement parameter x of the measuring base moving along the X direction; the laser interferometer corresponding to the fourth reflector can obtain the displacement parameter y of the measuring base moving along the Y direction; the third capacitive sensor can obtain the straightness change parameter Z1 of the measuring base moving along the X direction or the Y direction, and the first capacitive sensor can obtain the straightness change parameter Z when the probe moves in the Z direction. x The second capacitive sensor can obtain the straightness change parameter Z when the probe moves in the Z direction and deviates in the Y direction. y , the steps of the roundness error compensation algorithm of the measuring ball are as follows: S1: Place the standard ball on the measuring seat for measurement, and obtain the measurement data of each laser interferometer. At this time, the straightness change parameter Z that is offset in the X direction when the probe moves in the Z direction is eliminated. x Or the straightness change parameter Z offset in the Y direction y , eliminate the offset error parameter Z1 in the Z direction when the measuring base moves along the X direction or Y direction, so as to obtain the actual measurement value (x1, z1). Formula 1 is as follows: x1=xZ x z1=z-Z1+Z d S2: Assuming the radius of the stylus ball is r, and the tangent angle between the stylus ball and the ideal curve on the spherical surface of the standard sphere is α, the coordinates of the contact point on the ideal surface (x′, z′) can be obtained from the formula. Formula 2 is as follows: S3: Construct the following kinematic model. Formula 3 is as follows: β in formula 3 is the rotation error of the standard ball along the Y axis during measurement, t z is the offset error of the standard ball along the Z direction. The floating rod is provided with a probe, and the measuring ball is located at the bottom end of the probe. θ is the perpendicularity error between the probe and the X or Y axis when the probe moves along the Z axis. (x′, z) is the actual measurement value in step S2, and (x2, z2) is the final measurement result. S4: Solve the surface error of the standard sphere. Formula 4 is as follows: e(θ,β,t z )=z2-Z(x2).

2. The ultra-precision optical measurement method according to claim 1, characterized in that: The probe includes an outer cylinder and an inner cylinder located in the outer cylinder, the floating rod is provided in the inner cylinder, and an air flotation structure is provided on the outer cylinder and the inner cylinder. The floating rod can float in the inner hole of the inner cylinder through the air flotation structure, and a restriction structure for limiting the rotation of the floating rod and a positioning structure for supporting the floating rod are provided between the floating rod and the inner cylinder.

3. The ultra-precision optical measurement method according to claim 2, wherein: The air flotation structure includes an outer air inlet hole provided on the outer cylinder, an annular air channel provided on the inner cylinder, and a plurality of inner air inlet holes provided in the annular air channel. The outer air inlet hole is communicated with the annular air channel, and the inner air inlet hole is communicated with the inner hole.

4. The ultra-precision optical measurement method according to claim 2, wherein: The limiting structure includes limiting posts that are arranged opposite to each other, and the end of the reference plate is located between two corresponding limiting posts.

5. The ultra-precision optical measurement method according to claim 2, wherein: It also includes a connecting flange, the bottom end of which is provided with two elastic rings and a clamp for locking the two elastic rings, the end of the outer tube is located in the two elastic rings and is fixed to the connecting flange by the elastic rings, the connecting flange includes a flange plate and a connecting tube, a horizontal slit and a vertical slit are cut on the connecting tube, one end of the vertical slit is connected to the horizontal slit, and the other end of the vertical slit is connected to the outside world, and the elastic ring is formed by dividing the horizontal slit and the vertical slit.

6. The ultra-precision optical measurement method according to claim 5, characterized in that: It also includes a probe lifting mechanism, which includes a lifting movable plate, a lifting air flotation guide rail and a lifting motor. The lifting motor is connected to the lifting air flotation guide rail, the lifting movable plate is installed on the lifting air flotation guide rail, and the connecting flange is connected to the lifting movable plate.

7. The ultra-precision optical measurement method according to claim 6, wherein: A lens adjustment mechanism is provided between the connecting flange and the lifting movable plate. The lens adjustment mechanism includes an adjustment spring, a plurality of adjustment screw holes provided on the connecting flange, and an adjustment screw matched with the adjustment screw holes. One end of the adjustment spring is against the connecting flange and the other end is against the lifting movable plate.

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