Ultra-precision optical measurement method

Abstract

To provide an ultra-precise optical measurement method. [Solution] The system comprises a mounting base 100, a laser system provided on the mounting base 100, a probe system, and a measurement table system. The probe system includes a probe 300 and a Z-direction movement mechanism for moving the probe 300 up and down. The measurement table system includes a stage and an XY movement mechanism for moving the stage along the X and Y directions. The laser system includes a laser transmitter, a set of reflective mirrors, multiple laser interferometers, and a deflection mirror. Inside the probe 300 is a floating rod that can levitate and a stylus sphere attached to the bottom end of the floating rod, and the stylus sphere contacts the workpiece to be measured during measurement. The steps of the roundness error correction algorithm are to place a reference sphere on the stage and measure it, remove the error parameter, solve the shape error of the reference sphere using an aspherical equation, and then correct the measurement data by the shape error in the subsequent measurement process.

Description

[Technical Field]

[0001] This invention relates to an optical measurement method, and more particularly to an ultra-precision optical measurement method. [Background technology]

[0002] In ultra-precision machining and manufacturing processes, measurement is a crucial step, and it is necessary to inspect whether the machined workpiece conforms to the requirements through measurement. However, for some workpieces with special shapes, the surface of the workpiece is an aspherical free-form surface, so when measuring manually using general measuring instruments (such as micrometers), not only is the measurement process time-consuming, but it is also difficult to meet the required measurement accuracy. Therefore, the applicant has designed an ultra-precision optical measuring machine that performs precise measurements using an advanced laser system, and has designed a measurement method based on the structural principles of the measuring machine.

[0003] However, in the measurement process of the above method, the stylus ball at the end of the floating rod comes into contact with the surface of the workpiece, and since the end of the floating rod is spherical, the roundness error of the sphere affects the final measurement result. Therefore, it is necessary to improve the measurement accuracy by measuring with a reference sphere with high dimensional accuracy before the test, calculating the roundness error of the stylus ball, and correcting it in the subsequent measurement of the workpiece. Accordingly, the applicant has proposed a probe roundness error correction algorithm for calculating the roundness error of the stylus ball. [Overview of the project] [Problems that the invention aims to solve]

[0004] This invention provides an ultra-precise optical measurement method to overcome the shortcomings of the prior art. [Means for solving the problem]

[0005] As a technical means employed by the present invention to solve the technical problems, an ultra-precision optical measurement method comprising a mounting base, a laser system provided on the mounting base, a probe system, and a measurement table system, wherein the probe system comprises a probe, a Z-direction movement mechanism for moving the probe up and down, and a first capacitance sensor and a second capacitance sensor for measuring the straightness when the probe moves in the vertical direction, the measurement table system comprises a stage, an XY movement mechanism for moving the stage along the X and Y directions, and a third capacitance sensor for measuring the Z-direction offset error when the stage moves along the X or Y direction, the laser system comprises a laser transmitter, a reflection mirror set, a plurality of laser interferometers, and a deflection mirror, wherein the reflection mirror set comprises a first reflection mirror mounted on the probe and a second reflection mirror mounted on a floating rod, The laser interferometer comprises a third and fourth reflecting mirror mounted on a stage, and laser light emitted from a laser transmitter passes through the deflecting mirrors to reach each of the laser interferometers. The first, second, third, and fourth reflecting mirrors each correspond to a laser interferometer, and laser light irradiated from the laser interferometer onto the first, second, third, and fourth reflecting mirrors can be reflected back to the corresponding laser interferometer. The probe contains a floating rod that can levitate and a stylus ball attached to the bottom end of the floating rod. During measurement, the stylus ball contacts the workpiece to be measured, and the laser interferometer corresponding to the first reflecting mirror can obtain the displacement parameter z of the probe moving along the Z direction, and the laser interferometer corresponding to the second reflecting mirror can obtain the displacement parameter Z of the floating rod moving along the Z direction. dThe laser interferometer corresponding to the third reflecting mirror can obtain the displacement parameter x of the stage moving along the X direction, the laser interferometer corresponding to the fourth reflecting mirror can obtain the displacement parameter y of the stage moving along the Y direction, the third capacitance sensor can obtain the straightness change parameter Z1 of the stage moving along the X or Y direction, and the first capacitance sensor can obtain the straightness change parameter Z of the probe when it is shifted in the X direction while moving along the Z direction. x The second capacitance sensor can obtain the parameter of change in the straightness of the probe when it is shifted in the Y direction while moving in the Z direction. y The following steps are taken in the algorithm for correcting the roundness error of the stylus sphere: S1: A reference sphere is placed on the stage and measurements are taken to obtain measurement data from each laser interferometer. At this time, the parameter Z, which is the change in the straightness of the probe when it shifts in the X direction while moving along the Z direction, is measured. x Alternatively, the parameter Z for the change in probe straightness when shifted in the Y direction. y By removing the Z-direction offset error parameter Z1 when the stage moves along the X or Y direction, the measured value (x1, y1) is obtained, and Equation 1 is as follows.

[0006]

number

[0007] S2: If the radius of the stylus sphere is r and the tangent direction angle at the point of contact between the stylus sphere and the ideal curve on the spherical surface of the reference sphere is α, then the coordinates (x',y') of the contact point on the ideal surface can be obtained from the equation, and equation 2 is as follows.

[0008]

number

[0009] S3: Construct the following kinematic model, and equation 3 is as follows.

[0010]

Number

[0011] [In Formula 3, β is the rotational error of the reference sphere along the Y-axis during measurement, and t z is the offset error of the reference sphere along the Z-direction. A probe head is provided on the floating rod, the stylus sphere is located at the bottom end of the probe head, θ is the right-angle error between the X-axis or Y-axis when the probe head moves along the Z-axis, (x’, z’) is the actually measured value in Step S2, and (x2, z2) is the final measurement result.]

[0012] S4: Solve for the shape error of the reference sphere, and Formula 4 is as follows.

[0013]

Number

[0014] The probe includes an outer cylinder and an inner cylinder inside the outer cylinder. The floating rod is provided inside the inner cylinder. An air levitation structure is provided on the outer cylinder and the inner cylinder. The floating rod can levitate inside the inner hole of the inner cylinder through the air levitation structure. A limiting structure for restricting 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.

[0015] The air levitation structure includes an outer air intake hole provided on the outer cylinder, an annular air passage provided on the inner cylinder, and a plurality of inner air intake holes provided in the annular air passage. The outer air intake hole communicates with the annular air passage, and the inner air intake hole communicates with the inner hole.

[0016] The limiting structure includes limiting posts provided oppositely, and the end of the reference plate is located between two corresponding limiting posts.

[0017] Furthermore, it further includes a connection flange. At the bottom end of the connection flange, two elastic gripping rings and a clamp collar for clamping the two elastic gripping rings are provided. The end of the outer cylinder is located at the two elastic gripping rings and is fixed to the connection flange by the gripping of the elastic gripping rings. The connection flange includes a flange plate and a connection cylinder. Horizontal slits and vertical cutouts are made in the connection cylinder. One end of the vertical cutout communicates with the horizontal slit, and the other end of the vertical cutout communicates with the outside. The elastic gripping ring is formed by the division of the horizontal slit and the vertical cutout.

[0018] It further includes a probe lifting mechanism including a lifting moving plate, a lifting air floating guide rail, and a lifting motor. The lifting motor is connected to the lifting air floating guide rail. The lifting moving plate is attached to the lifting air floating guide rail. The connection flange is connected to the lifting moving plate.

[0019] A lens adjustment mechanism is provided between the connection flange and the lifting moving plate. The lens adjustment mechanism includes an adjustment spring, a plurality of adjustment bolt holes provided on the connection flange, and adjustment bolts that fit into the adjustment bolt holes. One end of the adjustment spring abuts against the connection flange, and the other end abuts against the lifting moving plate.

Advantages of the Invention

[0020] The advantageous effects of the present invention are as follows. The present invention proposes a probe roundness error correction algorithm for contour measurement equipment based on a reference sphere, calculates the shape error of the reference sphere, and corrects the measurement data by the shape error in the subsequent measurement process, so as to obtain accurate measurement values.

[0021] Hereinafter, the present invention will be specifically described while referring to the accompanying drawings and embodiments.

Brief Description of the Drawings

[0022] [Figure 1] It is an overall configuration diagram of the present invention. [Figure 2] It is a partial configuration diagram after omitting the metal frame. [Figure 3] This is a partial diagram showing the structure from a different angle, with the metal frame omitted. [Figure 4] This is a diagram showing the configuration when the metal frame, marble base, and marble plate are omitted. [Figure 5] This is a diagram of the probe configuration. [Figure 6] This is a cross-sectional diagram of the probe. [Figure 7] This is an internal diagram of the probe. [Figure 8] This is a diagram showing the configuration of the connecting flange. [Figure 9] This is a diagram of the stage layout. [Figure 10] This is a diagram showing the stage configuration from a different angle. [Figure 11] This is a three-dimensional exploded view of the lower and upper stage panels. [Figure 12] These are three-dimensional exploded views of the lower and upper stage panels as seen from different angles. [Figure 13] This is a schematic diagram illustrating the principle of the algorithm. [Modes for carrying out the invention]

[0023] The advantages, features, and methods of carrying out the present disclosure will be described through the following embodiments shown in the accompanying drawings. However, the present disclosure may be carried out in different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so that the present disclosure may be thorough and complete and so that the scope of the present disclosure may be fully conveyed to those skilled in the art. Furthermore, the present disclosure is limited only by the claims. The shapes, dimensions, proportions, angles, and numbers in the drawings illustrating embodiments of this disclosure are for illustrative purposes only, and therefore this disclosure is not limited to the details shown. The same reference numerals throughout this specification indicate the same elements. In the following descriptions, detailed descriptions of known features or configurations relating to the disclosure are omitted where such descriptions would unnecessarily obscure the essence of this disclosure. As used herein, the terms “equip,” “have,” and “include” may include other components unless “only” is used. Singular terms may also be intended to include plural forms unless the context clearly indicates otherwise. When describing components, it is understood that those components include a margin of error, even if not explicitly stated. When describing spatial relationships, for example, "on top of," "above," "below," and "adjacent," one or more parts can be placed between other parts, as long as the words "close" or "direct" are not used. When describing temporal relationships, for example, when describing a time order such as "after," "then," "next," and "before," discontinuous situations may be included unless "exactly" or "directly" is used. In this specification, terms such as “first,” “second,” etc., may be used to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be called a second element, and similarly, a second element may be called a first element. As those skilled in the art will readily understand, the features of the different embodiments of this disclosure can be combined or combined in part or in whole, and can be technically driven by working together in various ways. The embodiments of this disclosure may be performed independently of each other or together in an interdependent manner.

[0024] Referring to Figures 1 to 4, the present invention discloses an ultra-precise optical measurement method. The equipment based on this method comprises a mounting base 100, a laser system 200 provided on the mounting base 100, a probe system, and a measurement table system. The probe system comprises a probe 300 and a Z-direction movement mechanism for moving the probe up and down. The measurement table system comprises a stage 400 and an XY movement mechanism for moving the stage 400 in the X and Y directions. The mounting base 100 of this application consists of three parts: a metal frame 101 at the bottom, a marble base 102 provided on the metal frame 101, and a marble plate 103 positioned vertically on the marble base 2. This structure minimizes the influence of deformation of the mounting base 100 on measurements. The workpiece to be measured (not shown) is placed on the stage 400, and the stage 400 moves the workpiece to be measured left, right, forward, and backward so that different positions on the workpiece surface come into contact with the stylus sphere 700 in the probe 300. The stylus sphere 700 moves up and down in accordance with the change in height of the different positions on the workpiece surface.

[0025] The laser system comprises a laser transmitter, a set of reflective mirrors, a plurality of laser interferometers, and a deflection mirror. The set of reflective mirrors includes a first reflective mirror 500 mounted on the probe 300, a second reflective mirror mounted on the floating rod 501, and a third and fourth reflective mirror mounted on the stage. The first reflecting mirror 500 of this application is preferably mounted on a slider of a lifting air levitation guide rail which is integrally fixed with the probe 300 via a bracket, the probe 300 is mounted on a mounting base 100 via the lifting air levitation guide rail, laser light emitted from a laser transmitter passes through deflection mirrors to reach each of the laser interferometers, the first reflecting mirror 500, the second reflecting mirror 501, the third reflecting mirror 502 and the fourth reflecting mirror 503 each correspond to a laser interferometer, and laser light irradiated from the laser interferometer to the first reflecting mirror 500, the second reflecting mirror 501, the third reflecting mirror 502 and the fourth reflecting mirror 503 can be reflected back to the corresponding laser interferometer. The laser emitted from the laser transmitter passes through each deflection mirror before reaching each laser interferometer. Each laser interferometer calculates the beam reflected back by its own reflection mirror, feeding the displacement changes back to the laser system 200 via the laser beam. This provides the displacement changes for each displacement axis and probe measurements, ultimately allowing for the calculation of accurate dimensional data of the workpiece surface. Of course, since the laser system 200 in this application is a prior art externally purchased product, its specific structure and principle are omitted.

[0026] As shown in Figures 5 to 8, the probe 300 comprises an outer cylinder 1 and an inner cylinder 2 located inside the outer cylinder 1, both of which are cylindrical bodies. The outer cylinder 1 has a mounting hole 302, and the inner cylinder 2 is located inside the mounting hole. The outer cylinder 1 and inner cylinder 2 can be integrally fixed together by a pin. A floating rod 3 is provided in the inner cylinder 2, and since the floating rod 3 is made of a lightweight magnesium alloy, the contact pressure during measurement can be minimized. Of course, a probe head 701 is provided on the floating rod 3, the end face of the probe head 701 contacts the workpiece to be measured, the stylus sphere 700 is provided on the bottom end of the probe head 701, when the stage 400 moves, a slight vertical change occurs in the floating rod in accordance with the change in the height of the workpiece surface, a second reflective mirror 501 is attached to the floating rod 3, the second reflective mirror 501 is generally attached to the floating rod 3 by adhesive method, when the laser from the laser system 200 is shone on the second reflective mirror 501, the second reflective mirror 501 reflects the laser beam back to the laser system 200, and the laser system 200 can calculate the laser beam data that is reflected back to obtain accurate dimensional data of the workpiece surface. Of course, the laser system 200 and the second reflective mirror 501 are externally purchased items and are not components of this structure, so their specific structure and principles are omitted here. The structure of this probe 300 performs precise measurements by combining an air levitation structure and laser detection. The floating rod of the probe 300 structure can float within the inner bore of the inner cylinder via the air levitation structure, thus significantly avoiding interference from frictional resistance. The outer cylinder 1 and inner cylinder 2 are provided with an air levitation structure, and the floating rod 3 can float within the inner bore of the inner cylinder 2 via the air levitation structure. A limiting structure that restricts the rotation of the floating rod 3 and a positioning structure that supports the floating rod 3 are provided between the floating rod 3 and the inner cylinder 2. Of course, in this application, the position when the floating rod 3 contacts the positioning structure becomes the reference position for measurement, which is convenient for subsequent calculations.

[0027] As shown in the figure, the aforementioned air levitation structure comprises an outer air intake hole (not shown) provided in the outer cylinder 1, an annular air passage 4 provided in the inner cylinder 2, and a plurality of inner air intake holes 5 provided within the annular air passage 4. The inner air intake holes 5 are evenly distributed surrounding the inner bore of the inner cylinder 2, the outer air intake hole communicates with the annular air passage 4, and the inner air intake holes 5 communicate with the inner bore. The outer air intake holes 5 are connected to an external compressed air source via an air joint and an air hose. High-pressure gas enters the annular air passage 4 from the outer air intake hole, and then enters the inner air intake holes 5. In this way, a multi-point air intake structure can be formed within the inner bore of the inner cylinder 2. There are two annular air passages, one above the other. Of course, the outer cylinder 1 is provided with an outside air passage that communicates with the annular air passage 4. By having the outer air intake holes communicate with the outside air passage, a relatively uniform high-pressure air film is formed within the inner bore, preventing eccentricity and micro-movement of the floating rod 3 and improving measurement accuracy. A more preferable structure is one in which the inner air intake hole 5 is a tapered hole, and the diameter of the hole gradually decreases from the intake end to the exhaust end of the inner air intake hole 5. This method of diameter reduction allows the pressure of the gas entering the inner hole of the inner cylinder 2 to gradually increase, so that a larger air film is formed, which helps to prevent eccentricity and micro-movement of the floating rod 3 and improves the accuracy of the measurement.

[0028] As shown in the figure, the positioning structure comprises a reference plate 6 fixed to the floating rod 3 and a reference sphere 7 provided on the inner cylinder 2. The reference plate 6 is also a magnesium alloy plate, relatively thin, and both ends of the reference plate 6 are in contact with the reference sphere 7 to support the floating rod 3. The reference sphere 7 is made of steel, and the position where the reference plate 6 contacts the steel sphere becomes the reference point position. The limiting structure comprises opposing limiting posts 8, with the ends of the reference plate 6 positioned between the corresponding two limiting posts 8. The limiting posts 8 are made of ceramic and have a very smooth surface. The reference plate 6 can prevent the floating rod 3 from rotating due to the action of the limiting posts 8 and affecting accuracy. The smooth ceramic surface does not affect the vertical movement of the floating rod 3. The limiting posts 8 cooperate with the reference sphere 7 to allow the reference plate 6 to contact the reference sphere 7 horizontally.

[0029] As shown in the figure, a screw hole is provided inside the floating rod 3, and a connecting screw portion that fits into the screw hole is provided at the end of the probe head 701, making it easy to attach and detach the probe head 701 and convenient for subsequent replacement. Furthermore, a weight-reducing hole communicating with the screw hole is provided in the floating rod 3, and designing the floating rod 3 to be lightweight is advantageous for improving measurement accuracy.

[0030] In a preferred structure, an end plate 9 is provided at the end of the floating rod 3, a 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 hole, the weight reduction hole is in communication with the hole, the reference plate 6 is fixed by adhesive, and because the contact surface between the reference plate 6 and the end face of the floating rod 3 is small, the reference plate 6 and the end plate 9 are joined integrally, and of course the end plate 9 is also made of magnesium alloy and is joined integrally with the floating rod 3.

[0031] As shown in the figure, the outer cylinder 1 is further equipped with a connecting flange and is connected to the Z-direction movement mechanism via the connecting flange. Two elastic gripping rings 11 are provided at the bottom end of the connecting flange, and the end of the outer cylinder 1 is inside the two elastic gripping rings 11. The elastic gripping rings 11 are fixed to the connecting flange by gripping, and the elastic gripping rings 11 are tightened by clamp collars 12. The clamp collars 12 are purchased separately. Because the above structure is simple and easy to attach and detach, maintenance and replacement of the probe head 701 structure will be easier thereafter. The specific structure of the connecting flange of this application comprises a flange plate 14 and a connecting cylinder 15, wherein an annular transverse slit 16 and a vertical notch 13 are cut into the connecting cylinder 15, one end of the vertical notch 13 is in communication with the transverse slit 16 and the other end of the vertical notch 13 is in communication with the outside, and the elastic gripping ring 11 is formed by the division of the transverse slit 16 and the vertical notch 13. The above structure is easy to manufacture and low cost.

[0032] As shown in the figure, the structure further includes a Z-direction movement mechanism mounted on a marble plate 3 on the mounting base 100. The Z-direction movement mechanism comprises a lifting / lowering plate 19, a lifting / lowering air levitation guide rail, and a lifting / lowering motor. The lifting / lowering motor is connected to the lifting / lowering air levitation guide rail, the lifting / lowering plate 19 is attached to the lifting / lowering air levitation guide rail, and the connecting flange is connected to the lifting / lowering plate 19. With this structure, the inner cylinder 2 and the outer cylinder 1 can move compensatory movements in accordance with the movement of the floating rod 3. However, since the pressure of the air film formed around the floating rod 3 inside the inner cylinder 2 is not absolutely uniform, when the floating rod 3 moves up and down during the measurement process, the pressure of the air film changes, affecting the accuracy of the measurement. To ensure that the pressure of the air film acting on the floating rod 3 remains constant during the measurement process, the Z-direction movement mechanism tracks the data from the probe head 701 in real time, making corrective movements in accordance with the movement of the probe head 701. This ensures that the positions of the probe head 701 and the floating rod 3 relative to the inner cylinder 2 and outer cylinder 1 do not change, the measurement position does not change, and the contact pressure during measurement does not change, thereby improving measurement accuracy. The above lifting motor can be replaced with a linear servo motor, and of course, the lifting motor and the lifting air levitation guide rail are conventional products, so the specific structure and connection relationships are omitted here.

[0033] As shown in the figure, a lens adjustment mechanism for adjusting the angle of the second reflective mirror 501 is provided between the connecting flange and the lifting / moving plate 19. The lens adjustment mechanism comprises an adjustment spring (not shown), a plurality of adjustment bolt holes provided in the connecting flange, and adjustment bolts 20 that fit into the adjustment bolt holes. In this application, there are three adjustment bolt holes and three adjustment bolts 20 that fit into the adjustment bolt holes, evenly arranged around the inner cylinder 2. The adjustment bolts 20 abut against the lifting / moving plate 19 to control the relative angle between the connecting flange and the lifting / moving plate 19. After adjustment, the angle is maintained by tightening the connecting flange and the lifting / moving plate 19 with screws. To facilitate adjustment, the connecting flange and the adjustment bolts 20 are always kept in close contact, with one end of the adjustment spring in contact with the connecting flange and the other end in contact with the lifting / moving plate 19, making adjustment more convenient and accurate.

[0034] As shown in Figures 9 to 12, in this application, the stage 400 comprises a stage drive mechanism 21, a lower stage plate 22, and an upper stage plate 23. The lower stage plate 22 and the upper stage plate 23 are movable by the stage drive mechanism 21, allowing the workpiece to be measured placed on the upper stage plate 23 to be moved forward, backward, left, and right. The stage drive mechanism 21 is a conventional product and mainly consists of components such as two sets of servo motors and two sets of precision air levitation guide rails, and can achieve unidirectional movement in the X or Y direction, or planar movement in the X and Y directions. Since both the servo motors and air levitation guide rails are conventional technology, their specific structure and mounting method are omitted here.

[0035] As shown in the figure, the third reflective mirror 502 and the fourth reflective mirror 503 are located on the upper stage plate 23. Of course, for ease of mounting, a mirror holder 25 is provided on the upper stage plate 23, and the third reflective mirror 502 and the fourth reflective mirror 503 are mounted on the corresponding mirror holder 25. An adjustment structure is provided between the upper stage plate 23 and the lower stage plate 22, and the third reflective mirror 502 and the fourth reflective mirror 503 can be adjusted perpendicular to the laser beam irradiated from the laser system 200 onto the reflective mirrors by the corresponding adjustment structure. In the above structure, the precision drive mechanism 1 consists of two servo motors and two sets of precision air levitation guide rails, and can achieve unidirectional movement in the X or Y direction, or planar movement in the X and Y directions. Since both the servo motors and air levitation guide rails are conventional technology, their specific structure and mounting method are omitted here. Of course, the laser system 200 is also an externally purchased item, so its specific structure and mounting method are also omitted here.

[0036] As shown in the figure, the adjustment structure comprises at least three adjustment screws (not shown), and in this application, it is preferable to have three adjustment screws. The adjustment screws are screwed into the upper stage plate 23, and of course, the upper stage plate is provided with adjustment screw holes 26 that fit the adjustment screws. The adjustment screws contact the lower stage plate 22 to adjust the position and angle of the upper stage plate 23. The three adjustment screws are evenly arranged around the center of the upper stage plate 23, and by screwing in the adjustment screws, they contact the lower stage plate 22, lifting the corresponding side of the upper stage plate 23, thereby adjusting the angle position of the upper stage plate 23. The reflective mirror becomes perpendicular to the laser beam, ensuring measurement accuracy. After the adjustment is complete, the upper stage plate 23 and the lower stage plate 22 are fastened together with fasteners, which are also screws.

[0037] As shown in the figure, the upper stage plate 23 is provided with a positioning groove 27, and the lower stage plate 22 is provided with a positioning base 28 that can be placed in the positioning groove 27. The adjustment screw contacts the positioning base 28, and the fitting of the positioning base 28 and the positioning groove 27 enables temporary positioning during assembly. In this application, the positioning groove 27 is preferably a cylindrical groove, the positioning base 28 is a cylindrical base, the diameter of the positioning groove 27 is slightly larger than the positioning base 28, and both may be movement fits. Since the height of the cylindrical base is greater than the depth of the positioning groove 27, there is a gap between the upper stage plate 23 and the lower stage plate 22, providing an adjustment space. In a preferred structure, the positioning base 28 is provided with three positioning holes (not shown), and the ends of the adjustment screws are located inside the positioning holes, so that the adjustment screws do not shift during or after adjustment, and adjustment accuracy is ensured.

[0038] As shown in the figure, a plurality of steel balls 29 are provided between the upper stage plate 23 and the lower stage plate 22. The steel balls 29 are mounted around the positioning base 28 and are fixed by being sandwiched between the upper stage plate 23 and the lower stage plate 22. The support of the steel balls 29 makes it easier to adjust the angle of the upper stage plate 23. Since the contact between the steel balls 29, the upper stage plate 23 and the lower stage plate 22 is always point contact, it does not affect the adjustment of the upper stage plate 23. After the upper stage plate 23 and the lower stage plate 22 are fastened together, the suspension area of ​​the upper stage plate 23 is supported, making it less prone to bending or deformation.

[0039] As a further structural feature, the lower stage plate 22 is provided with a plurality of lower pads 30, the lower pads 30 are provided with positioning grooves 27, and the upper stage plate 23 is provided with a plurality of upper pads 31. The steel balls 29 are positioned in the corresponding positioning grooves 27 and are fixed by being sandwiched between the upper pads 31 and the lower pads 30. The positioning grooves 27 not only facilitate the mounting and positioning of the steel balls 29 during assembly, but the pads also make processing easier.

[0040] As a further structural feature, the upper stage plate 23 is provided with an upper recessed groove 32, and the pad and steel ball 29 are located within the corresponding upper recessed groove 32, thereby reducing the overall thickness of the stage 400.

[0041] In short, the probe 300 and stage 400 are specialized for precision measurement. The floating rod of the probe 300 structure can float in the inner bore of the inner cylinder via an air levitation structure, significantly avoiding interference from frictional resistance. A reflective mirror is provided on the floating rod, and through the cooperation of the reflective mirror and the laser system 200, even slight changes in the vertical movement of the floating rod are detected and calculated by the laser system 200, enabling precision measurement. The stage 400 comprises a lower stage plate and an upper stage plate. A reflective mirror is provided on the upper stage plate, and an adjustment structure is provided between the upper and lower stage plates. By adjusting the adjustment structure, the reflective mirror and the laser system 200 can cooperate precisely, allowing the stage 400 to be well-suited to the laser system 200 and enabling precision measurement of the workpiece.

[0042] To obtain deviation data, the apparatus is equipped with a first capacitance sensor 600 and a second capacitance sensor 601 for measuring the straightness of the probe as it moves vertically, and a third capacitance sensor 602 for measuring the Z-direction offset error when the stage moves along the X or Y direction. During measurement, the stylus sphere 700 contacts the workpiece being measured, and the laser interferometer corresponding to the first reflecting mirror 500 can obtain the displacement parameter z of the probe moving along the Z direction, and the laser interferometer corresponding to the second reflecting mirror 501 can obtain the displacement parameter Z of the floating rod moving along the Z direction. dcan be obtained. The laser interferometer corresponding to the third reflection mirror 502 can obtain the displacement parameter x of the stage moving along the X direction. The laser interferometer corresponding to the fourth reflection mirror 503 can obtain the displacement parameter y of the stage moving along the Y direction. The third capacitance sensor 602 can obtain the straightness change parameter Z1 of the stage moving along the X or Y direction. The first capacitance sensor 600 can obtain the straightness change parameter Z of the probe when it is displaced in the X direction when moving along the Z direction. x can be obtained. The second capacitance sensor 601 can obtain the straightness change parameter Z of the probe when it is displaced in the Y direction when moving in the Z direction. y can be obtained. The steps of the roundness error correction algorithm of the stylus ball are as follows.

[0043] As shown in FIG. 13, S1: Place the reference sphere 800 on the stage for measurement. First, measure one generatrix of the reference sphere 800. During the generatrix measurement process, the stylus ball 700 moves while contacting the surface of the reference sphere 800, and measurement data is obtained through each laser interferometer and capacitance sensor. At this time, the straightness change parameter Z of the probe when it is displaced in the X direction when moving along the Z direction x or the straightness change parameter Z of the probe when it is displaced in the Y direction is removed. By removing the Z-direction offset error parameter Z1 when the stage moves along the X or Y direction, the measured values (x1, y1) are obtained. Equation 1 is as follows. y

[0044]

Equation

[0045] ​S2: In measurement step S1, the actual motion trajectory L of the stylus sphere 700 is the change in the central trajectory of the stylus sphere 700. Therefore, it is necessary to remove the radius error of the stylus sphere 700 from the measurement data. If the radius of the stylus sphere is r and the tangent direction angle of the contact point of the ideal curve on the spherical surface of the stylus sphere 700 and the reference sphere 800 is α, then the coordinates (x',z') of the contact point on the ideal curved surface can be obtained from the equation, and equation 2 is as follows.

[0046]

number

[0047] S3: The measurements in step S2 include perpendicularity errors during the measurement process, attitude errors of the object being measured, contour errors of the reference sphere 800, and roundness errors of the probe. Since the contour accuracy of the reference sphere 800 is very high, its impact on the measurement results is very small and can be ignored. If there is a perpendicularity error between the probe and the XY reference plane, the measurement point deviates from the theoretical point, and a fundamental error occurs in the measurement. In the case of a one-dimensional reference sphere 800, the curvature of the entire surface is equal, so when solving the attitude error, the displacement along the XY direction can be ignored, and only the tilt error and offset error along the Z direction are included, and the following kinematic model is constructed, and Equation 3 is as follows.

[0048]

number

[0049] [In Equation 3, β is the rotational error of the reference sphere 800 along the Y axis during measurement, t z (x',z') is the offset error of the reference sphere 800 along the Z direction, θ is the perpendicularity error between the X-axis and Y-axis when the probe head moves along the Z-axis, (x',z') is the measured value at step S2, and (x2,z2) is the final measurement result.

[0050] S4: The shape error of the reference sphere 800 is determined, and Equation 4 is as follows.

[0051]

number

[0052] Z(x²) is an aspherical equation, and in order to minimize the measurement error, the least squares method is used to optimize the above equation, and the shape error e(θ,β,t) of the reference sphere 800 being measured is calculated. z The equation can be solved, and since the error of the reference sphere 800 is ignored, this error is the roundness error of the stylus sphere 700. In the subsequent measurement process, the measurement data is corrected by the shape error, thereby obtaining accurate measurements.

[0053] The above describes in detail the ultra-precise optical measurement method provided by embodiments of the present invention. This specification describes the principles and implementations of the present invention with specific examples. The above description of embodiments is for the sole purpose of aiding understanding of the methods and core technical ideas of the present invention, and at the same time, for those skilled in the art, the specific implementations and application scope will vary based on the technical ideas of the present invention. In short, the contents of this specification are not limiting to the present invention.

Claims

1. An ultra-precise optical measurement method, The system comprises a mounting base, a laser system provided on the mounting base, a probe system, and a measurement table system, wherein the probe system comprises a probe, a Z-direction movement mechanism for moving the probe up and down, and a first capacitance sensor and a second capacitance sensor for measuring the straightness of the probe when it moves vertically, the measurement table system comprises a stage, an XY movement mechanism for moving the stage along the X and Y directions, and a third capacitance sensor for measuring the Z-direction offset error when the stage moves along the X or Y direction, the laser system comprises a laser transmitter, a set of reflective mirrors, a plurality of laser interferometers, and a deflection mirror, wherein the set of reflective mirrors comprises a first reflective mirror mounted on the probe, a second reflective mirror mounted on a floating rod, and a third and fourth reflective mirrors mounted on the stage, The laser light emitted from the laser transmitter passes through the deflection mirrors and reaches each of the laser interferometers, the first reflective mirror, the second reflective mirror, the third reflective mirror, and the fourth reflective mirror each correspond to the laser interferometers, and the laser light irradiated from the laser interferometers onto the first reflective mirror, the second reflective mirror, the third reflective mirror, and the fourth reflective mirror can be reflected back to the corresponding laser interferometer, the probe has a floating rod that can levitate and a stylus ball attached to the bottom end of the floating rod, the stylus ball contacts the workpiece to be measured during measurement, the laser interferometer corresponding to the first reflective mirror can obtain the displacement parameter z of the probe moving along the Z direction, and the laser interferometer corresponding to the second reflective mirror can obtain the displacement parameter Z of the floating rod moving along the Z direction. ｄ The laser interferometer corresponding to the third reflective mirror can obtain the displacement parameter x of the stage moving along the X direction, the laser interferometer corresponding to the fourth reflective mirror can obtain the displacement parameter y of the stage moving along the Y direction, and the third capacitance sensor can obtain the straightness change parameter Z of the stage moving along the X or Y direction. １ The first capacitance sensor can obtain the parameter of change in the straightness of the probe when it is shifted in the X direction while moving along the Z direction, and the parameter of change in the straightness of the probe Z ｘ The second capacitance sensor can obtain the parameter of change in the straightness of the probe when it is shifted in the Y direction while moving in the Z direction. ｙ You can obtain The steps of the algorithm for correcting the roundness error of the stylus sphere are as follows: S1: Place a reference sphere on the stage for measurement to obtain the measurement data of each laser interferometer. At this time, when moving along the Z direction, if there is a deviation in the X direction, the straightness change parameter Z of the probe ｘ or when there is a deviation in the Y direction, the straightness change parameter Z of the probe ｙ is removed. When the stage moves along the X direction or the Y direction, the Z-direction offset error parameter Z １ is removed to obtain the measured value (x １ , y １ ), and Equation 1: [Math 1] S2: If the radius of the stylus sphere is r and the tangent direction angle of the contact point between the stylus sphere and the ideal curve on the spherical surface of the reference sphere is α, then the coordinates (x', z') of the contact point on the ideal surface can be obtained from the equation, and equation 2: [Math 2] S3: Construct the following kinematic model, Equation 3: [Math 3] [In Equation 3, β is the rotation error of the reference sphere along the Y axis during measurement, t ｚ is the offset error of the reference sphere along the Z direction, a probe head is provided on the floating rod, the stylus sphere is located at the bottom end of the probe head, θ is the perpendicularity error between the X axis or Y axis when the probe head moves along the Z axis, (x', z') is the measured value in step S2, (x ２ , z ２ This is the final measurement result. S4: Solve the shape error of the reference sphere, and Equation 4: [Math 4] That is A highly precise optical measurement method characterized by its features.

2. The probe comprises an outer cylinder and an inner cylinder located inside the outer cylinder, the floating rod is provided inside the inner cylinder, an air levitation structure is provided in the outer cylinder and the inner cylinder, the floating rod can float in the inner bore of the inner cylinder via the air levitation structure, and a limiting structure that restricts the rotation of the floating rod and a positioning structure that supports the floating rod are provided between the floating rod and the inner cylinder. The ultra-precision optical measurement method according to claim 1.

3. The air levitation structure comprises an outer air intake hole provided in the outer cylinder, an annular air passage provided in the inner cylinder, and a plurality of inner air intake holes provided within the annular air passage, wherein the outer air intake hole communicates with the annular air passage, and the inner air intake holes communicate with the inner holes. The ultra-precision optical measurement method according to claim 2.

4. The restriction structure comprises opposing restriction posts, and the end of the reference plate is located between the two corresponding restriction posts. The ultra-precision optical measurement method according to claim 2.

5. The device further comprises a connecting flange, the bottom end of which is provided with two elastic gripping rings and a clamp collar for tightening the two elastic gripping rings, the end of the outer cylinder is positioned between the two elastic gripping rings and fixed to the connecting flange by the gripping of the elastic gripping rings, the connecting flange comprises a flange plate and a connecting cylinder, the connecting cylinder has a horizontal slit and a vertical notch cut into it, one end of the vertical notch communicates with the horizontal slit and the other end of the vertical notch communicates with the outside, and the elastic gripping rings are formed by the division of the horizontal slit and the vertical notch. The ultra-precision optical measurement method according to claim 2.

6. The probe lifting mechanism further includes a lifting plate, a lifting air levitation guide rail, and a lifting motor, wherein the lifting motor is connected to the lifting air levitation guide rail, the lifting plate is attached to the lifting air levitation guide rail, and the connecting flange is connected to the lifting plate. The ultra-precision optical measurement method according to claim 5.

7. A lens adjustment mechanism is provided between the connecting flange and the lifting / lowering plate, and the lens adjustment mechanism comprises an adjustment spring, a plurality of adjustment bolt holes provided in the connecting flange, and an adjustment bolt that fits into the adjustment bolt hole, with one end of the adjustment spring in contact with the connecting flange and the other end in contact with the lifting / lowering plate. The ultra-precision optical measurement method according to claim 6.

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