Confocal measurement system and measurement method based on weight allocation

Abstract

The present invention provides a confocal measurement system and a measurement method based on weight distribution. The confocal measurement system measures the position distance through the differential confocal measurement component in the position measurement unit. By adding an angle measurement unit on the basis of the differential confocal optical path and then constructing an angle measurement optical path, the tilt angle can be measured while measuring the position. The technical solution provided by the present invention solves the problem that the tilt angle cannot be measured while differential confocal microscopy distance measurement is used in the prior art. The optical path of the optical system is simple and easy to implement. The angle measurement component has a simple structure of spectroscopic angle measurement and low cost. It is achieved that the tilt angle information of the position to be measured is obtained while differential confocal distance measurement is performed, and the accuracy is higher in optical morphology measurement, especially in the identification of tiny surface defects.

Description

Technical Field

[0001] The invention belongs to the technical field of optical detection, and in particular relates to a confocal measurement system and a measurement method based on weight allocation. Background Art

[0002] In the field of ultra-precision manufacturing of optical components, in order to achieve high-precision detection of parameters such as the shape and surface of the processed free-form mirror, the measurement probe used by the measuring equipment is required to have not only high spatial resolution at the nanometer level, but also technical characteristics such as non-contact. Confocal microscopes and differential confocal microscopes are widely used in industry and are ideal optical probes for three-dimensional contour detection of free-form surfaces.

[0003] However, in the prior art, Aperture-coded confocal profilometry, published in Optics Letters, proposed an aperture-coded confocal microscope. By tilting the surface to be measured, the light beam reflected from the sample surface will be partially blocked by the designed aperture. Therefore, by analyzing the intensity of the reflected light beam, the surface height and the tilt angle can be measured simultaneously. However, this method is limited to measuring the tilt angle along one direction, and the tilt angle of the measurement point is often two-dimensional.

[0004] If laser differential confocal microscopy measurement is performed by separately acquiring the two-dimensional inclination angle and spatial position information of discrete points, there will be two aspects of cumulative errors, and it is impossible to provide accurate three-dimensional data of free-form surfaces. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and to propose a confocal measurement system and a measurement method based on weight allocation.

[0006] To achieve the above object, the present invention adopts the following specific technical solutions:

[0007] The present invention provides a confocal measurement system based on weight allocation, comprising a position measurement unit and an angle measurement unit; wherein:

[0008] The position measurement unit comprises a first beam splitter, a first focusing lens, a second beam splitter, and a differential confocal measurement component which are sequentially arranged along the optical path;

[0009] The angle measurement unit includes a polyhedron prism and an angle measurement component arranged in sequence along the optical path;

[0010] The laser beam is incident on the first beam splitter, transmitted to the first focusing lens through the first beam splitter for focusing, the focused beam is incident on the object to be measured, reflected by the surface of the object to be measured, passes through the first focusing lens, and is incident on the first beam splitter, reflected by the first beam splitter to the second beam splitter for splitting, a part of the beam is reflected as an angle measurement beam and is incident on the polygonal prism, the polygonal prism splits the incident angle measurement beam and then incident on the angle measurement component, the angle measurement component obtains the angle information of the surface of the object to be measured according to the weight distribution of the intensity of the incident beam, the other part is transmitted as a position measurement beam and is incident on the differential confocal measurement component for position measurement, the position information of the surface of the object to be measured is obtained through the differential confocal measurement component, and the surface shape information and surface inclination information of the object to be measured are simultaneously obtained in combination with the angle information.

[0011] Furthermore, the polyhedral prism is a tetrahedral prism, and three side surfaces of the tetrahedral prism are coated with a reflective film.

[0012] Furthermore, the angle measurement component is a focusing lens group and a photoelectric detector group arranged in sequence along the optical path;

[0013] The focusing lens group includes a second focusing lens, a third focusing lens, and a fourth focusing lens;

[0014] The photoelectric detector group includes a first photoelectric detector, a second photoelectric detector, and a third photoelectric detector;

[0015] The angle measurement beam reflected by each side surface of the tetrahedral prism is incident on the second focusing lens, the third focusing lens and the fourth focusing lens in sequence, and after being focused by the corresponding focusing lenses, is incident on the first photodetector, the second photodetector and the third photodetector in sequence.

[0016] Further, the differential confocal measurement assembly includes an interferometer, a transmission assembly, a third beam splitter, a pre-focus focusing lens, a pre-focus pinhole, a pre-focus photodetector, a post-focus focusing lens, a post-focus pinhole, and a post-focus photodetector; wherein,

[0017] The transmission assembly is fixedly connected to the first focusing lens, and the transmission assembly controls the first focusing lens to move back and forth along the direction of the laser beam to control the imaging position of the surface to be measured, and the interferometer is used to measure the displacement value of the first focusing lens; the object plane of the pre-focus focusing lens is located before the focus, and the pre-focus photoelectric detector is arranged on its image plane; the object plane of the post-focus focusing lens is located after the focus, and the post-focus photoelectric detector is arranged on its image plane;

[0018] The position measurement beam is incident on the third beam splitter for splitting, and a part of the beam is reflected as a pre-focus measurement beam, which passes through the pre-focus focusing lens and the pre-focus pinhole in sequence and then is incident on the pre-focus photodetector; the other part of the beam is transmitted as a post-focus measurement beam, which passes through the post-focus focusing lens and the post-focus pinhole in sequence and then is incident on the post-focus photodetector.

[0019] The present invention also provides a measurement method of a confocal measurement system based on weight allocation, and the confocal measurement system based on weight allocation implements measurement, comprising the following steps:

[0020] S1. Build a confocal measurement system based on weight allocation;

[0021] The laser beam is transmitted to the object to be measured through the first beam splitter and the first focusing lens in sequence, and after being reflected by the point to be measured on the surface of the object to be measured, it returns to the first beam splitter along the original optical path, and after being reflected by the first beam splitter to the second beam splitter, the angle measurement beam reflected by the second beam splitter is incident on the angle measurement unit for measurement; the position measurement beam transmitted by the second beam splitter is incident on the differential confocal measurement component for position measurement;

[0022] S2,

[0023] The angle measurement method of the angle measurement unit is:

[0024] The angle measurement beam is incident on the polygonal prism, and the polygonal prism splits the incident angle measurement beam, and then the beam is incident on the focusing lens group, and then the beam is focused by the corresponding focusing lens and incident on the photoelectric detector group, and the light intensity data on the corresponding detector is obtained, and the corresponding relationship between the weight distribution of the beam intensity and the tilt angle is obtained, so as to complete the tilt angle measurement of the object to be measured;

[0025] The position measurement method of the position measurement unit is:

[0026] The differential confocal measurement component obtains a differential confocal response signal curve, and determines the distance position information of the object to be measured through the zero-crossing point of the differential confocal response curve;

[0027] The angle measurement method and the position measurement method are combined to simultaneously obtain the surface shape information and the surface inclination information of the object to be measured.

[0028] Furthermore, the angle measurement method in step S2 is specifically as follows:

[0029] S2-01a, the angle measurement beam is incident on the polygonal prism, the polygonal prism splits the incident angle measurement beam, and the beams are respectively incident on the second focusing lens, the third focusing lens and the fourth focusing lens, and are respectively incident on the first photodetector, the second photodetector and the third photodetector after being focused by the corresponding focusing lenses, and light intensity data I1, I2 and I3 of the first photodetector, the second photodetector and the third photodetector are collected;

[0030] S2-02a, replacing the object to be tested with a plane reflector, changing the tilt angle of the plane reflector, respectively collecting light intensity data of the first photodetector, the second photodetector, and the third photodetector for each change, and fitting a fitting function model of the weighted distribution of the tilt angle and the intensity using the least squares method according to the light intensity data;

[0031] S2-03a, substituting the light intensity data I1, I2, and I3 of the first photodetector, the second photodetector, and the third photodetector into the fitting function model to obtain the angle information of the point to be measured on the surface of the object to be measured.

[0032] Furthermore, the step S2-02a is specifically as follows:

[0033] The object to be tested is replaced by a plane reflector, the tilt angle of the plane reflector is (θ1, θ2), the tilt angle of the plane reflector is changed and sampling is performed, i groups of samples are collected, and the tilt angle of each group of samples is recorded as (θ 1_i ,θ 2_i ), collecting light intensity data I of the first photodetector, the second photodetector, and the third photodetector 1_i ,I 2_i ,I 3_i ;

[0034] make but

[0035] Wherein, i is a positive integer greater than 1, P1 and P2 are weights of the energy received by the first photodetector and the second photodetector respectively; P 1_i , P 2_i the energy weights of the i-th group of data received by the first photodetector and the second photodetector respectively;

[0036] The relationship functions f and g between the two-dimensional tilt angle (θ1, θ2) of the plane reflector and I1, I2, I3 are obtained by using the least squares fitting method of binary quadratic polynomials, which is expressed as formula (1):

[0037]

[0038] Among them, a0, a1, a2, a3, a4, a5, b0, b1, b2, b3, b4, b5 are constants to be determined;

[0039] The purpose of fitting is to find constants a0, a1, a2, a3, a4, a5 so that the error function Minimize, find constants b0, b1, b2, b3, b4, b5 so that the error function Minimum;

[0040] To minimize the error function E1, Where j = 0, 1, ..., 5, we can get formula (2):

[0041]

[0042] Solving the equation system of formula (2) can obtain a0, a1, a2, a3, a4, a5;

[0043] To minimize the error function E2, Where j = 0, 1, ..., 5, we can get formula (3)

[0044]

[0045] Solve the equation group of formula (3) to obtain b0, b1, b2, b3, b4, b5;

[0046] Substitute the above solution into formula (1) to obtain the fitting function models f and g of the weight distribution of the tilt angle and the light intensity.

[0047] Furthermore, the position measurement method in step S2 is specifically as follows:

[0048] S2-01b, driving the first focusing lens to move by the transmission component, and respectively collecting the light signal intensities of the pre-focus photodetector and the post-focus photodetector;

[0049] S2-02b, when the light intensity of the pre-focus photodetector is equal to the light signal intensity of the post-focus photodetector, obtaining a differential confocal signal curve;

[0050] S2-03b. Measure the displacement value of the first focusing lens corresponding to the zero-crossing position of the differential confocal signal curve through the interferometer, and then obtain the position information of the point to be measured on the surface of the object to be measured.

[0051] The present invention can achieve the following technical effects:

[0052] 1. The confocal measurement system and measurement method based on weight allocation provided by the present invention can simultaneously obtain the surface shape information and surface inclination information of the object to be measured;

[0053] 2. The confocal measurement system and method based on weight allocation provided by the present invention proposes that angle measurement can be performed on the basis of a differential confocal optical path through an angle measurement unit;

[0054] 3. The confocal measurement system and measurement method based on weight allocation provided by the present invention can achieve measurement over a large angle range;

[0055] 4. The confocal measurement system based on weight allocation provided by the present invention has a simple structure and is easy to implement, and the measurement method is easy to operate, while taking into account both accuracy and speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a structural schematic diagram of a confocal measurement system based on weight allocation according to an embodiment of the present invention;

[0057] Figure 2 is a schematic structural diagram of an angle measurement unit of a confocal measurement system based on weight allocation according to an embodiment of the present invention;

[0058] Figure 3 Schematic diagram of the principle of an angle measurement unit of a confocal measurement system based on weight allocation according to an embodiment of the present invention

[0059] Figure 4 is a flow chart of a confocal measurement method based on weight allocation according to an embodiment of the present invention;

[0060] Figure 5 is a schematic diagram of the principle of two-dimensional tilt angle measurement in a confocal measurement method according to an embodiment of the present invention;

[0061] Figure 6 Schematic diagram of a differential confocal curve in a confocal measurement method according to an embodiment of the present invention.

[0062] Reference numerals include:

[0063] 1 laser beam, 2 first beam splitter, 3 first focusing lens, 4 object to be measured, 5 second beam splitter, 6 third beam splitter, 7 post-focus focusing lens, 8 post-focus pinhole, 9 post-focus photodetector, 10 pre-focus focusing lens, 11 pre-focus pinhole, 12 pre-focus photodetector, 13 angle measurement unit, 14 tetrahedral prism, 15-1 second focusing lens, 15-2 third focusing lens, 15-3 fourth focusing lens, 16-1 first pinhole, 16-2 second pinhole, 16-3 third pinhole, 17-1 first photodetector, 17-2 second photodetector, 17-3 third photodetector. DETAILED DESCRIPTION

[0064] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0065] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0066] Combine the following Figure 1-Figure 6 The specific working mode of the confocal measurement system and the measurement method based on weight allocation according to the embodiment of the present invention is described in detail:

[0067] Figure 1 A schematic structural diagram of a confocal measurement system based on weight allocation according to an embodiment of the present invention is shown.

[0068] The confocal measurement system based on weight distribution in the embodiment of the present invention includes a position measurement unit and an angle measurement unit 13. In the embodiment of the present invention, the position measurement unit includes a first beam splitter 2, a first focusing lens 3, a second beam splitter 5, and a differential confocal measurement assembly arranged in sequence along the optical path. In the embodiment of the present invention, the angle measurement unit 13 includes a polyhedron prism and an angle measurement assembly arranged in sequence along the optical path. In the embodiment of the present invention, the differential confocal measurement assembly includes an interferometer, a transmission assembly, a third beam splitter 6, a pre-focus focusing lens 10, a pre-focus pinhole 11, a pre-focus photodetector 12, a post-focus focusing lens, a post-focus pinhole 8, and a post-focus photodetector 9. The transmission assembly is fixedly connected to the first focusing lens 3, and the transmission assembly controls the first focusing lens 3 to move back and forth along the direction of the laser beam 1 to control the imaging position of the surface to be measured. The interferometer is used to measure the displacement value of the first focusing lens 3; the object plane of the pre-focus focusing lens 10 is located before the focus, and the pre-focus photodetector 12 is arranged on its image plane; the object plane of the post-focus focusing lens 7 is located after the focus, and the post-focus photodetector 9 is arranged on its image plane. The angle measurement assembly in the embodiment of the present invention is a focusing lens group, a pinhole group and a photodetector group arranged in sequence along the optical path. The focusing lens group includes a first focusing lens 3, a second focusing lens 15-1, and a third focusing lens 15-2. The pinhole group includes a first pinhole 16-1, a second pinhole 16-2, and a third pinhole 16-3. The photodetector group includes a first photodetector 17-1, a second photodetector 17-2, and a third photodetector 17-3.

[0069] like Figure 1As shown, after the beam expansion, the collimated laser beam 1 with a diameter of d and a wavelength of λ is incident on the first beam splitter 2, and is transmitted to the first focusing lens 3 through the first beam splitter 2 for focusing, and the focused beam is incident on the object to be measured 4. The first focusing lens 3 is fixedly connected to the transmission component, and the transmission component can drive the first focusing lens 3 to move vertically in the direction of the incident light, and the displacement of the first focusing lens 3 can be accurately measured at the nanometer level by the interferometer rangefinder. The transmission component in the embodiment of the present invention can use the piezoelectric objective lens positioner in the prior art, which can be selected according to the actual situation, and the present invention does not limit this. After being reflected by the surface of the object to be measured 4, the focused light beam passes through the first focusing lens 3 and enters the first beam splitter 2. After being reflected by the first beam splitter 2, it enters the second beam splitter 5 for splitting. A part of the light beam is reflected as an angle measurement beam and enters the polygonal prism. The polygonal prism splits the incident angle measurement beam. The angle measurement beam reflected by each side of the polygonal prism is sequentially incident on the second focusing lens 15-1, the third focusing lens 15-2 and the fourth focusing lens 15-3. After being focused by the corresponding focusing lens, it is sequentially incident on the first photodetector 17-1, the second photodetector 17-2 and the third photodetector 17-3. Another part is transmitted as a position measurement beam and enters the third beam splitter 6 for splitting. The reflected light beam is used as a pre-focus measurement beam. The pre-focus measurement beam passes through the pre-focus focusing lens 10 and the pre-focus pinhole 11 in sequence and enters the pre-focus photodetector 12. The transmitted light beam is used as the post-focus measurement beam, and the post-focus measurement beam passes through the post-focus focusing lens 7 and the post-focus pinhole 8 in sequence and then enters the post-focus photodetector 9. The first focusing lens 3 moves under the control of the transmission device, and its position is recorded by the interferometer rangefinder, so that the measurement position on the object to be measured 4 moves from the pre-focus position of the first focusing lens 3 to the post-focus position, and the pre-focus photodetector 12 and the post-focus photodetector 9 record the light intensity change.

[0070] The present invention also provides a preferred embodiment, as Figure 2 As shown, the polyhedral prism is a tetrahedral prism 14, and the three sides of the tetrahedral prism 14 are coated with a reflective film. The angle measurement light beam reflected by each side of the tetrahedral prism 14 is incident on the second focusing lens 15-1, the third focusing lens 15-2 and the fourth focusing lens 15-3 respectively, and is incident on the first photodetector 17-1, the second photodetector 17-2 and the third photodetector 17-3 in sequence after being focused by the corresponding focusing lenses. Since the light beam is incident on different measurement positions of the object to be measured 4, the inclination angles of different measurement positions are different, and then the position of the angle measurement light beam after being reflected by the object to be measured 4 is also different when it is incident on the tetrahedral prism 14, resulting in different energy combinations of the three beams after the splitting. In the embodiment of the present invention, a weight distribution strategy of light intensity is performed according to different angles of the object to be measured 4, and different light intensity values ​​based on weight distribution are collected and analyzed to obtain the angle information of the surface of the object to be measured 4.

[0071] like Figure 3 As shown in FIG. 1 , the three side surfaces of the tetrahedral prism 14: surface DAB, surface DBC, and surface DAC are all coated with a reflective film. The angle between each side surface and the bottom surface of the tetrahedral prism 14 in the embodiment of the present invention is 45°, that is, ∠DFO = ∠DGO = ∠DHO = 45°. With the side edges DA, DB, and DC between the side surfaces, the reflection along the side can be realized. The angle measurement beam is split along the incident direction. The angle measurement beam incident from the direction is split into three beams: Direction of the beam, along Direction of the beam, along The three light beams are focused by the second focusing lens 15-1, the third focusing lens 15-2 and the fourth focusing lens 15-3, and then pass through the first pinhole 16-1, the second pinhole 16-2 and the third pinhole 16-3 to filter out the ambient stray light, and finally are collected by the first photodetector 17-1, the second photodetector 17-2 and the third photodetector 17-3, and the light intensity data are recorded respectively.

[0072] The present invention also provides a preferred embodiment, in which the differential confocal measurement component includes an interferometer, a transmission component, a third beam splitter 6, a pre-focus focusing lens 10, a pre-focus pinhole 11, a pre-focus photodetector 12, a post-focus focusing lens, a post-focus pinhole 8, and a post-focus photodetector 9.

[0073] The embodiment of the present invention also provides a measurement method of a confocal measurement system based on weight allocation, such as Figure 4 As shown, the following steps are included:

[0074] S1. Build a confocal measurement system based on weight allocation.

[0075] The laser beam 1 is transmitted to the object to be measured 4 through the first beam splitter 2 and the first focusing lens 3 in sequence, and after being reflected by the point to be measured on the surface of the object to be measured 4, it returns to the first beam splitter 2 along the original optical path, and after being reflected by the first beam splitter 2 to the second beam splitter 5, the angle measurement beam reflected by the second beam splitter 5 is incident on the angle measurement unit 13 for measurement; the position measurement beam transmitted through the second beam splitter 5 is incident on the differential confocal measurement component for position measurement.

[0076] S2,

[0077] The angle measurement method of the angle measurement unit 13 is:

[0078] S2-01a, the angle measurement beam is incident on the tetrahedral prism 14, and the tetrahedral prism 14 is The angle measurement beam incident from the direction is split into three beams: Direction of the beam, along Direction of the beam, along The three light beams are focused by the second focusing lens 15-1, the third focusing lens 15-2 and the fourth focusing lens 15-3 respectively, and then pass through the first pinhole 16-1, the second pinhole 16-2 and the third pinhole 16-3 respectively to filter out the ambient stray light, and finally are collected by the first photodetector 17-1, the second photodetector 17-2 and the third photodetector 17-3 respectively, and the light intensity data I1, I2 and I3 on ​​the corresponding photodetectors are recorded and collected respectively.

[0079] S2-02a, replace the object 4 to be tested with a plane reflector, where the plane reflector is a standard part. Figure 5 As shown, the inclination angle of the plane reflector is (θ1, θ2). An I-XYZ coordinate system is established with the position I on the object 4 to be measured as the origin. is the normal vector of the position to be measured, for The projection on the surface YIZ, for Projected on the surface XIZ, the angle ∠KIM is denoted as θ1, and the angle ∠LIM is denoted as θ2.

[0080] The tilt angle of the plane mirror is changed i times, and a total of i groups of samples are collected. The tilt angle of each group of samples is recorded as (θ 1_i ,θ 2_i ). Collect the light intensity data of the first photodetector 17-1, the second photodetector 17-2, and the third photodetector 17-3 for each change. 1_i ,I 2_i ,I 3_i .

[0081] make but

[0082] Wherein, i is a positive integer greater than 1, P1 and P2 are the weights of the energy received by the first photodetector and the second photodetector respectively; P 1_i , P 2_i The energy weights of the i-th group of data received by the first photodetector and the second photodetector respectively.

[0083] Using the least squares fitting method of binary quadratic polynomial, the relationship functions f and g between the two-dimensional tilt angle (θ1, θ2) of the plane reflector and I1, I2, I3 are obtained, which is expressed as formula (1):

[0084]

[0085] Among them, a0, a1, a2, a3, a4, a5, b0, b1, b2, b3, b4, b5 are constants to be determined;

[0086] The purpose of fitting is to find constants a0, a1, a2, a3, a4, a5 so that the error function Minimize, find constants b0, b1, b2, b3, b4, b5 so that the error function Minimum;

[0087] To minimize the error function E1, Where j = 0, 1, ..., 5, we can get formula (2):

[0088]

[0089] Solving the equation system of formula (2) can obtain a0, a1, a2, a3, a4, a5;

[0090] To minimize the error function E2, Where j = 0, 1, ..., 5, we can get formula (3)

[0091]

[0092] Solve the equation group of formula (3) to obtain b0, b1, b2, b3, b4, b5;

[0093] Substitute the above solution into formula (1) to obtain the fitting function models f and g of the weight distribution of the tilt angle and the light intensity.

[0094] S2-03a, substitute the light intensity data I1, I2, I3 of the first photodetector 17-1, the second photodetector 17-2, and the third photodetector 17-3 into the fitting function models f and g to obtain the angle information of the surface of the object 4 to be measured.

[0095] The specific position measurement method is:

[0096] S2-01b, drive the first focusing lens 3 to move through the transmission assembly to collect the light signal intensities of the pre-focus photodetector 12 and the post-focus photodetector 9 respectively.

[0097] After the pre-focus measuring beam passes through the pre-focus focusing lens 10, it is incident on the f -u m A pre-focus pinhole 11 with a diameter of D is placed at the position of the pre-focus pinhole 11, and a pre-focus photodetector 12 is placed behind the pre-focus pinhole 11. f is the focal length of the focusing lens 10 before focusing, u m is the defocus amount. After the post-focus measuring beam passes through the post-focus focusing lens 7, it is incident on the b +um A post-focus pinhole 8 with a diameter of D is placed at the position of the post-focus pinhole 8, and a post-focus photodetector 9 is placed behind the post-focus pinhole 8. Among them, f b is the focal length of the post-focus lens 7, u m The first focusing lens 3 moves under the drive of the transmission assembly, and the position of the first focusing lens 3 is recorded as u by the interferometer, so that the measurement position on the object to be measured 4 moves from the pre-focus position of the first focusing lens 3 to the post-focus position, and the pre-focus photoelectric detector 12 and the post-focus photoelectric detector 9 record the light intensity changes, which are recorded as I(u, -u m ) and I(u, +u m ).

[0098] S2-02b. When the light intensity of the pre-focus photodetector 12 is equal to the light signal intensity of the post-focus photodetector 9, a differential confocal signal curve is obtained.

[0099] The first focusing lens 3 moves under the drive of the transmission assembly. When the position measurement beam is just focused on the point to be measured on the surface of the object 4, the light intensity at the pre-focus pinhole 11 and the post-focus pinhole 8 is exactly equal. At this time, the light intensity signals received by the pre-focus photodetector 12 and the post-focus photodetector 9 are also equal, that is, I(u, -u m )=I(u,+u m ). Will I(u,-u m ) and I(u, +u m ) is subtracted to obtain the differential confocal signal curve FES, FES = I (u, -u m )-I(u,+u m ),like Figure 6 shown.

[0100] S2-03b, measuring the displacement value of the first focusing lens 3 corresponding to the zero-crossing position of the differential confocal signal curve by an interferometer, and then obtaining the position information of the test point on the surface of the object 4 to be tested.

[0101] By using the principle that the absolute zero point of the axial light intensity response of the differential confocal signal curve accurately corresponds to the focus of the test point, the zero point of the FES curve corresponds to the displacement reading value of the first focusing lens 3 measured by the interferometer, thereby obtaining the distance information of the test point on the surface of the object 4 to be tested.

[0102] The angle measurement method and the position measurement method are combined to simultaneously obtain the surface shape information and the surface inclination information of the object 4 to be measured, that is, the object 4 to be measured is measured once, and the distance measurement position information and the inclination angle information are obtained at the same time.

[0103] The present invention provides an embodiment that solves the problem in the prior art that the inclination angle cannot be measured while differential confocal microscopy distance measurement is performed through a confocal measurement system and a measurement method based on weight distribution. By adding a tetrahedron prism 14 beam splitting angle measurement optical path on the basis of the differential confocal optical path, the measurement of the inclination angle of the measurement position is achieved, and the optical path of the optical system is simple and easy to implement. The tetrahedron prism 14 beam splitting angle measurement optical path has a simple structure and low cost. It is achieved that the inclination angle information of the position to be measured is obtained while differential confocal distance measurement is performed, and the optical shape measurement, especially the recognition of tiny surface defects, has higher accuracy.

[0104] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0105] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0106] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A confocal measurement system based on weight allocation, characterized in that: It includes a position measurement unit and an angle measurement unit; wherein, The position measurement unit comprises a first beam splitter, a first focusing lens, a second beam splitter, and a differential confocal measurement component which are sequentially arranged along the optical path; The angle measurement unit includes a polyhedron prism and an angle measurement component arranged in sequence along the optical path; The laser beam is incident on the first beam splitter, transmitted to the first focusing lens through the first beam splitter for focusing, the focused beam is incident on the object to be measured, reflected by the surface of the object to be measured, passes through the first focusing lens, and then is incident on the first beam splitter, reflected by the first beam splitter to the second beam splitter for splitting, a part of the beam is reflected as an angle measurement beam and is incident on the polygonal prism, the polygonal prism splits the incident angle measurement beam and then incident on the angle measurement component, the angle measurement component obtains the angle information of the surface of the object to be measured according to the weight distribution of the intensity of the incident beam, the other part is transmitted as a position measurement beam and is incident on the differential confocal measurement component for position measurement, the position information of the surface of the object to be measured is obtained through the differential confocal measurement component, and the surface shape information and surface inclination information of the object to be measured are simultaneously obtained in combination with the angle information; The polyhedral prism is a tetrahedral prism, and three side surfaces of the tetrahedral prism are coated with a reflective film; The angle measurement assembly is a focusing lens group, a pinhole group, and a photoelectric detector group arranged in sequence along the optical path; The focusing lens group includes a second focusing lens, a third focusing lens, and a fourth focusing lens; The pinhole group includes a first pinhole, a second pinhole, and a third pinhole; The photoelectric detector group includes a first photoelectric detector, a second photoelectric detector, and a third photoelectric detector; The angle measurement light beams reflected by the side surfaces of the tetrahedral prism are respectively incident on the second focusing lens, the third focusing lens and the fourth focusing lens, and after being focused by the corresponding focusing lenses, they pass through the first pinhole, the second pinhole and the third pinhole, and are respectively incident on the first photodetector, the second photodetector and the third photodetector.

2. The confocal measurement system based on weight allocation according to claim 1, characterized in that: The differential confocal measurement assembly includes an interferometer, a transmission assembly, a third beam splitter, a front-focus focusing lens, a front-focus pinhole, a front-focus photoelectric detector, a back-focus focusing lens, a back-focus pinhole, and a back-focus photoelectric detector; wherein, The transmission assembly is fixedly connected to the first focusing lens, and the transmission assembly controls the first focusing lens to move back and forth along the direction of the laser beam to control the imaging position of the surface to be measured, and the interferometer is used to measure the displacement value of the first focusing lens; the object plane of the pre-focus focusing lens is located before the focus, and the pre-focus photoelectric detector is arranged on its image plane; the object plane of the post-focus focusing lens is located after the focus, and the post-focus photoelectric detector is arranged on its image plane; The position measurement beam is incident on the third beam splitter for splitting, and a part of the beam is reflected as a pre-focus measurement beam, which passes through the pre-focus focusing lens and the pre-focus pinhole in sequence and then is incident on the pre-focus photodetector; the other part of the beam is transmitted as a post-focus measurement beam, which passes through the post-focus focusing lens and the post-focus pinhole in sequence and then is incident on the post-focus photodetector.

3. A measurement method using the confocal measurement system based on weight allocation according to any one of claims 1 or 2, characterized in that: The confocal measurement system based on weight allocation realizes measurement, including the following steps: S1. Build a confocal measurement system based on weight allocation; The laser beam is transmitted to the object to be measured through the first beam splitter and the first focusing lens in sequence, and after being reflected by the point to be measured on the surface of the object to be measured, it returns to the first beam splitter along the original optical path, and after being reflected by the first beam splitter to the second beam splitter, the angle measurement beam reflected by the second beam splitter is incident on the angle measurement unit for measurement; the position measurement beam transmitted by the second beam splitter is incident on the differential confocal measurement component for position measurement; S2、 The angle measurement method of the angle measurement unit is: The angle measurement beam is incident on the polygonal prism, and the polygonal prism splits the incident angle measurement beam, and then the beam is incident on the focusing lens group, and then the beam is focused by the corresponding focusing lens and incident on the photoelectric detector group, and the light intensity data on the corresponding detector is obtained, and the corresponding relationship between the weight distribution of the beam intensity and the tilt angle is obtained, so as to complete the tilt angle measurement of the object to be measured; The position measurement method of the position measurement unit is: The differential confocal measurement component obtains a differential confocal response signal curve, and determines the distance position information of the object to be measured through the zero-crossing point of the differential confocal response curve; The angle measurement method and the position measurement method are combined to simultaneously obtain the surface shape information and the surface inclination information of the object to be measured.

4. The measuring method according to claim 3, characterized in that: The angle measurement method in step S2 is specifically as follows: S2-01a, the angle measurement beam is incident on the polygonal prism, the polygonal prism splits the incident angle measurement beam, and after the beam splitting, the beam is incident on the second focusing lens, the third focusing lens and the fourth focusing lens respectively through the corresponding pinholes, and after being focused by the corresponding focusing lenses, the beam is incident on the first photodetector, the second photodetector and the third photodetector respectively, and the light intensity data I1, I2 and I3 of the first photodetector, the second photodetector and the third photodetector are collected; S2-02a, replacing the object to be measured with a plane reflector, changing the tilt angle of the plane reflector, respectively collecting light intensity data of the first photodetector, the second photodetector, and the third photodetector each time the light intensity data is changed, and fitting a fitting function model of the weight distribution of the tilt angle and the light intensity using the least squares method according to the light intensity data; S2-03a, substituting the light intensity data I1, I2, and I3 of the first photodetector, the second photodetector, and the third photodetector into the fitting function model to obtain the angle information of the point to be measured on the surface of the object to be measured.

5. The measuring method according to claim 4, characterized in that: The step S2-02a is specifically as follows: The object to be tested is replaced by a plane reflector, the tilt angle of the plane reflector is (θ1, θ2), the tilt angle of the plane reflector is changed and sampling is performed, i groups of samples are collected, and the tilt angle of each group of samples is recorded as (θ 1_i ,θ 2_i ), collecting light intensity data I of the first photodetector, the second photodetector, and the third photodetector 1_i ,I 2_i ,I 3_i ; make but Wherein, i is a positive integer greater than 1, P1 and P2 are weights of the energy received by the first photodetector and the second photodetector respectively; P 1_i , P 2_i the energy weights of the i-th group of data received by the first photodetector and the second photodetector respectively; The relationship functions f and g between the two-dimensional tilt angle (θ1, θ2) of the plane reflector and I1, I2, I3 are obtained by using the least squares fitting method of binary quadratic polynomials, which is expressed as formula (1): Among them, a0, a1, a2, a3, a4, a5, b0, b1, b2, b3, b4, b5 are constants to be determined; The purpose of fitting is to find constants a0, a1, a2, a3, a4, a5 so that the error function Minimize, find constants b0, b1, b2, b3, b4, b5 so that the error function Minimum; To minimize the error function E1, Where j = 0, 1, ..., 5, we can get formula (2): Solving the equation system of formula (2) can obtain a0, a1, a2, a3, a4, a5; To minimize the error function E2, Where j = 0, 1, ..., 5, we can get formula (3) Solve the equation group of formula (3) to obtain b0, b1, b2, b3, b4, b5; Substitute the solution result into formula (1) to obtain the fitting function models f and g of the weight distribution of the tilt angle and the light intensity.

6. The measuring method according to claim 5, characterized in that: The position measurement method in step S2 is specifically as follows: S2-01b, driving the first focusing lens to move through the transmission assembly, respectively collecting the light signal intensity of the pre-focus photoelectric detector and the post-focus photoelectric detector; S2-02b, when the light intensity of the pre-focus photodetector is equal to the light signal intensity of the post-focus photodetector, obtaining a differential confocal signal curve; S2-03b. Measure the displacement value of the first focusing lens corresponding to the zero-crossing position of the differential confocal signal curve by an interferometer, and then obtain the position information of the test point on the surface of the object to be tested.

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