A white light interferometry system

Abstract

The application provides a white light interferometry system, comprising a probe module, wherein the probe module is provided with a first probe and a second probe; the number of the second probes is multiple, and the multiple second probes are distributed on the circumferential side of the first probe; the first probe is used for emitting first detection light along the axial direction of the first probe and receiving reflected first detection light; the second probe is used for emitting second detection light outward along the radial direction of the second probe and receiving reflected second detection light; the probe module is used for acquiring the brightest peak of interference of the first detection light and the second detection light in one micro scanning process; the first probe is used for acquiring the measuring point information of the side surface of the object or the bottom of the groove; and the second probe is used for acquiring the measuring point information of the side wall of the object or the groove wall. The first probe and the second probe can be used to simultaneously or sequentially measure the top surface, the bottom surface and the 360-degree side wall of the workpiece in one clamping, the measuring efficiency is improved by several times, and the probe, the inclined measuring seat or the workpiece need not be frequently replaced or turned over for multiple times.

Description

Technical Field

[0001] This invention relates to the field of non-contact measurement technology, and in particular to a white light interferometry system. Background Technology

[0002] Traditional non-contact measurement sensors (such as laser triangulation or confocal sensors) typically employ a uniaxial design, making it difficult to effectively measure vertical sidewalls, deep grooves, or internal cavities of workpieces. When multi-angle features need to be measured, it is necessary to frequently change the probe, tilt the probe holder, or repeatedly flip the workpiece, resulting in low measurement efficiency, significant accuracy loss, and complex operation.

[0003] How to more conveniently and quickly measure objects with deep grooves on their surfaces is one of the important problems that urgently need to be solved in this field. Summary of the Invention

[0004] The purpose of this application is to provide a white light interferometric measurement system to overcome the shortcomings of the prior art. It can solve the problems of single-angle measurement limitations and low efficiency in measuring complex features in existing non-contact measurement technologies.

[0005] This invention provides a white light interferometry system, including a probe module, wherein the probe module is provided with a first probe and a second probe; There are multiple second probes, which are distributed around the periphery of the first probe; The first probe is used to emit a first detection light along the axial direction of the first probe and receive the reflected first detection light; the second probe is used to emit a second detection light outward along the radial direction of the second probe and receive the reflected second detection light. The probe module is used to obtain the brightest interference peak of the first detection light and the second detection light during a single micro-scan; to obtain measurement point information of the surface of the object being measured or the bottom of the groove through the first probe, and to obtain measurement point information of the sidewall or groove wall of the object being measured through the second probe.

[0006] Optionally, the number of the second probes is 4 to 8, and the multiple second probes are arranged in a circular array around the center line of the first probe.

[0007] Optionally, the second probe is positioned in the same direction as the first probe along its axis, and the second probe and the first probe share the same mounting reference surface and the same coordinate system.

[0008] Optionally, it also includes a high-rigidity base, on which the probe module is fixedly mounted, and the positions of the first probe and the second probe relative to the high-rigidity base are fixed.

[0009] Optionally, the high-rigidity base includes a connector, a connecting rod, and a mounting frame; the mounting frame is a rectangular frame. The two ends of the connecting rod are respectively fixedly installed at the midpoints of two parallel sides of the mounting frame, and the connector is fixedly installed at the center of the connecting rod, so that the high-rigidity base dissipates heat to the left and right sides with the connector as the center.

[0010] Optionally, the zero optical path difference positions of the first probe and the second probe are the same.

[0011] Optionally, the high-rigidity base has a coefficient of thermal expansion of less than 1 ppm / ℃ and an elastic modulus of greater than 150 GPa.

[0012] Optionally, the probe module is fixedly mounted on the connector.

[0013] Optionally, a positioning pin is fixedly provided on the connecting rod; the positioning pin is perpendicular to the position of the mounting frame; the connecting piece is connected to the connecting rod by bolts, and the connecting piece is provided with a positioning hole that matches the positioning pin.

[0014] Optionally, the mounting frame is fixedly mounted on a coordinate measuring machine.

[0015] Compared with the prior art, this application has the following beneficial effects: This invention utilizes a probe module comprising a first probe and a second probe, with the measuring axes of the first and second probes at a 90-degree angle. A single clamping operation allows for simultaneous or sequential measurement of the top surface, bottom surface, and 360-degree sidewalls of a workpiece using both probes, significantly increasing measurement efficiency. This eliminates the need for frequent probe changes, tilting of the probe holder, or multiple workpiece rotations, thus avoiding installation errors caused by repeated probe replacements and improving measurement accuracy. Furthermore, this invention eliminates contact with the workpiece during measurement, removing contact force and the risk of contact damage and deformation. The invention also employs a high-rigidity base to provide rigid support for the probe module, ensuring geometric stability during high-speed scanning and long-term operation. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the probe module of the white light interferometry system provided by the present invention; Figure 2 A bottom view of the probe module of the white light interferometry system provided by the present invention; Figure 3 This is a schematic diagram of the installation structure of the probe module and the high-rigidity base provided by the present invention.

[0018] Explanation of reference numerals in the attached figures: 1-Probe module, 2-First probe, 3-Second probe, 4-High rigidity base, 5-Connector, 6-Connecting rod, 7-Mounting frame, 8-Positioning pin, 9-Positioning hole. Detailed Implementation

[0019] To better understand the technical solutions in this specification, the present invention will be described in detail below with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments in this specification. All other embodiments obtained by those skilled in the art based on the embodiments in this specification without inventive effort are within the scope of protection of this specification.

[0021] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of this specification. The singular forms “a,” “the,” and “the” as used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0022] The main reason for the problems mentioned in the background art is that the probe can only provide measurement in one direction. When facing a workpiece with deep grooves or holes on the surface, it cannot measure the sidewalls of the deep grooves or holes. On the other hand, directly increasing the number of probes will lead to a significant increase in heat. The temperature rise caused by the increased heat will further deform the part in contact with the probe, thus reducing the accuracy of the detection.

[0023] The technical solution protected by this invention will now be described in detail with reference to the accompanying drawings. Example

[0024] Please see Figures 1-2 As shown, a white light interferometric measurement system provided by the present invention includes a probe module 1; the probe module 1 is provided with a first probe 2 and a second probe 3. The first probe 2 is used to measure surfaces perpendicular to the axis of the first probe 2; the second probe is used to measure surfaces parallel to the first probe 2, such as the sidewalls of deep pits, grooves, and deep holes on an object.

[0025] Multiple second probes 3 are distributed around the periphery of the first probe 2. The first probe 2 emits a first detection light along its axial direction and receives the reflected first detection light. The second probes 3 emit a second detection light outward along their radial direction and receive the reflected second detection light. The second probes 3 are at a 90-degree angle to the measurement axis of the first probe 2. The zero optical path difference positions of the first probe 2 and the second probes 3 are the same. For deep holes or deep trenches, their inner walls typically require 360-degree measurement. Therefore, multiple second probes 3 can be evenly distributed around the circumference of the first probe 2, such as in a circular array around the first probe 2. In some preferred implementations, the number of second probes 3 is 4 to 8, arranged in a circular array around the centerline of the first probe 2. Having 8 second probes improves the coverage of complex structures. The number of second probes 2 is preferably 3, 4, 5, 6, 7 or 8. If the number of second probes 2 is too small, it will easily lead to a decrease in the coverage of the inner wall detection surface of the deep hole. If the number of second probes 2 is too large, it will easily lead to an overheating of the probe module 1.

[0026] The probe module 1 is used to acquire the brightest interference peak of the first detection light and the brightest interference peak of the second detection light during a single micro-scan. The first detection light is emitted by the first probe 2, reflected by the surface of the object under test, received by the second probe 2, and output to the probe module 1. It should be noted that the second detection light is split into two beams; one beam is reflected after illuminating a reference mirror. The first ray reflected by the reference mirror interferes with the ray reflected from the workpiece surface, resulting in the brightest interference peak. This is prior art for those skilled in the art and will not be elaborated further. Both the first and second detection lights are white light. The mechanism by which the brightest interference peak of the second detection light is generated is the same as that of the first detection light and will not be elaborated further.

[0027] In this embodiment, the first probe 2 acquires measurement point information on the surface of the object being measured or the bottom of the groove, and the second probe 3 acquires measurement point information on the sidewall or groove wall of the object being measured. Therefore, during a single measurement, by synchronously moving the first probe 2 and the second probe 3, suitable measurement point information can be found. Here, the measurement point information is the measurement point position information corresponding to the brightest interference peak.

[0028] The first probe 2 serves as the system height reference and is responsible for the overall axial measurement of the workpiece surface. The second probe 3 is arranged around the first probe 2 and is used for sidewall, deep cavity, and complex geometry measurements. That is, the first probe 2 is the main axial probe, and the second probe 3 is the radial probe.

[0029] The second probe 3 is positioned in the same direction as the first probe 2 along its axis, and the second probe 3 and the first probe 2 share the same mounting reference surface and the same coordinate system.

[0030] During use, the first probe 2 and the second probe 3 are fixed on the same base, ensuring no relative displacement or angular offset between them. Optical path matching and zero-path-difference calibration are performed on all first probes 2 and second probes 3. The entire set of probes is then fixed on the spindle of the coordinate measuring machine (CMM) and moved synchronously.

[0031] When measuring the top surface of the workpiece, the CMM spindle is controlled to drive the measuring head in a horizontal two-dimensional stepping translation, scanning field by field. After moving a small field of view, the horizontal movement is paused, and a Z-axis micro-scan is performed, simultaneously acquiring top surface data and data from the surrounding side walls. That is, top surface data is acquired through the first probe 2, and data from the surrounding side walls is acquired through the second probe 2. In this embodiment, the Z-axis micro-scan refers to a small movement in the axial direction of the first probe 2. When encountering steps, cavities, or vertical walls, the CMM moves the entire system vertically at a uniform speed; the horizontal optical path of the second probe 2 continuously conforms to the wall measurement range, sampling synchronously throughout, covering the entire side wall height.

[0032] After scanning, using the coordinate system of the first probe 2 as a reference, the point cloud data of multiple sets of second probe 3 are uniformly mapped to the same CMM reference coordinate system through a pre-calibrated rigid body algorithm. Quality weights are generated based on signal-to-noise ratio and interference contrast, and multi-source data are weighted and fused. Abnormal noise points and stray light interference points are automatically removed, and errors caused by thermal drift and minor vibrations are corrected. Local 3D topography, roughness, and contour dimension data are generated in real time. All local small field-of-view data are seamlessly stitched together using CMM precision motion coordinates to form a complete, blind-spot-free 3D global point cloud model of the workpiece, along with reports on measurement uncertainty and topography parameters.

[0033] This embodiment can simultaneously or sequentially measure the top surface, bottom surface, and 360-degree sidewall of a workpiece using the first probe 2 and the second probe 3 in a single clamping, improving measurement efficiency several times over. It eliminates the need for frequent probe replacements, tilting of the probe holder, or multiple workpiece flipping, thus avoiding errors caused by multiple probe replacements and improving measurement accuracy.

[0034] Both probe 2 (first probe) and probe 3 (second probe) are WLI (White Light Interferometry) probes with a resolution of 0.05 nm, repeatability of 2 nm, and dynamic measurement frequency of 40 kHz, enabling dynamic online measurement with a coverage of >98%. The multi-probe layout was optimized through Monte Carlo simulation to ensure a coverage of >98%.

[0035] During the measurement process, neither the first probe 2 nor the second probe 3 needs to contact the workpiece, which can avoid surface damage and improve efficiency.

[0036] The first probe 2 adopts the Mirau / Michelson architecture; the second probe 3 achieves 90° optical path deflection through a high-precision right-angle prism or reflector. The optical paths of the first probe 2 and the second probe 3 are matched to ensure that the zero optical path difference positions are consistent.

[0037] Specifically, the optical structure of the first probe 2 adopts a Mirau / Michelson interferometric architecture, suitable for high-resolution axial measurements. It features a high numerical aperture (NA=0.55) objective lens to ensure micron and sub-micron level optical resolution. The light source uses broadband LED light (450–700 nm) with a coherence length <10 μm. In this invention, the first and second probes acquire data synchronously and are calibrated in a unified coordinate system. Combined with a precise optical path matching design, time-division measurement and individual focusing are unnecessary, significantly improving measurement efficiency and avoiding data misalignment and splicing errors from multiple probes. This solves the problems of large blind zones and poor coordination among multiple probes in traditional single-probe measurements. Example

[0038] This embodiment is a further improvement on the first embodiment. The parts that are the same as those in the first embodiment will not be repeated. Only the differences will be described.

[0039] As the total number of first probes 2 and second probes 3 increases, the heat generated by probe module 1 during operation also increases exponentially. This temperature rise causes the corresponding components to expand due to heat, leading to significant measurement errors. Although errors caused by thermal drift can be reduced through correction, the effect is limited. How to fundamentally reduce errors caused by thermal expansion is one of the most important problems that urgently needs to be solved in this field.

[0040] To reduce the impact of heat on measurement accuracy, the following improvements were made in this embodiment. See also... Figures 1-3 As shown, it also includes a high-rigidity base 4, on which the probe module 1 is fixedly mounted. The positions of the first probe 2 and the second probe 3 relative to the high-rigidity base 4 are fixed. Preferably, the high-rigidity base 4 is made of Invar alloy. The high-rigidity base 4 may also be made of ceramic composite material.

[0041] The high-rigidity base 4 includes a connector 5, a connecting rod 6, and a mounting frame 7; the mounting frame 7 is a rectangular frame. Setting the mounting frame 7 as a rectangular frame with symmetrical distribution helps to ensure that the heat received on both sides is approximately equal, eliminating errors caused by different thermal drift amounts on the left and right sides. Specifically, the two ends of the connecting rod 6 are respectively fixedly installed at the midpoints of two parallel sides of the mounting frame 7, and the connector 5 is fixedly installed at the center of the connecting rod 6. The projection of the center of the connecting rod 6 onto the surface of the mounting frame 7 coincides with the center of the mounting frame 7, ensuring that the connector 5 is essentially at the center of the mounting frame 7. This allows the high-rigidity base 4 to dissipate heat to the left and right sides with the connector 5 as the center. The probe module 1 is fixedly installed on the connector 5. This left-right and top-bottom thermal symmetry structure ensures that the deformation is relatively equal when the temperature changes, reducing warping caused by temperature gradients.

[0042] The high-rigidity base 4 has a thermal expansion coefficient of less than 1 ppm / ℃ and an elastic modulus greater than 150 GPa. Furthermore, a positioning pin 8 is fixedly provided on the connecting rod 6; the positioning pin 8 is perpendicular to the mounting frame 7; the connecting piece 5 is bolted to the connecting rod 6, and the connecting piece 5 has a positioning hole 9 that matches the positioning pin 8. This facilitates installation while ensuring a repeatability accuracy of <1 μm. This invention, through an integrated high-rigidity base, combined with a symmetrical layout and a zero-relative-motion design, eliminates splicing errors and deformations in split structures, ensuring stable probe reference and solving the problems of reference confusion and easy deviation in traditional multi-probe systems. It also improves structural vibration resistance and avoids accuracy loss due to base deformation during measurement.

[0043] The mounting frame 7 is fixedly mounted on the coordinate measuring machine. This invention provides rigid support for the probe module 1 by setting a high-rigidity base, ensuring geometric stability during high-speed scanning and long-term operation.

[0044] In practical implementation, the mounting frame 7 should be designed as an integral structure. In this embodiment, the mounting base supporting the first probe 2 and the second probe 3 adopts an integrated structural design with high modulus and low coefficient of thermal expansion. The elastic modulus of the base is greater than 150 GPa, and the overall rigidity is excellent, which can effectively reduce elastic deformation and structural micro-deformation caused by temperature changes.

[0045] The high-rigidity base 4 is a one-piece machined structure without segmented splicing or scattered connecting parts. The overall material is homogeneous and uniform, and it will not experience local warping, torsion, or misalignment deformation due to differences in the thermal expansion coefficients of different components during heating. The first probe 2 and the second probe 3 are rigidly fixed to the preset mounting positions of the high-rigidity base 4. Throughout the measurement process, the relative geometric position and light emission posture between the first probe 2 and the second probe 3 and the high-rigidity base 4 remain constant, avoiding reference offset caused by assembly gaps and thermal deformation of connecting parts.

[0046] Meanwhile, the high-rigidity base 4 adopts a central axis symmetrical annular thermally symmetrical layout, with the first probe 2 centrally located and multiple second probes 3 evenly arranged circumferentially, resulting in a symmetrical arrangement of heat source distribution and heat dissipation conditions. When the light source or circuit generates heat or the ambient temperature fluctuates, the overall temperature field of the base is uniformly distributed, and thermal expansion and contraction exhibit a regular overall deformation in the same direction and synchronously, without problems such as unilateral skewness or local stress concentration, and will not disrupt the pre-calibrated optical path matching relationship of each probe and the unified reference of zero optical path difference.

[0047] In addition, the high-rigidity base 4 has a large overall heat capacity, which can evenly and slowly release the concentrated heat generated by local heat sources, weaken the local temperature difference gradient, and reduce the differential deformation caused by hot spots. The high-rigidity base 4 is equipped with a heat insulation transition structure at the connection position with the three-coordinate machine tool, which blocks the conductive heat source of the machine tool moving parts and further reduces the impact of external heat intrusion.

[0048] Multiple temperature acquisition points are arranged on the mounting frame 7 and the connecting rod 6 to detect the temperature value at each point on the mounting frame 7, so as to determine the temperature drift compensation amount based on the temperature value at each point. The compensation formula for the temperature drift compensation amount is as follows: ; in, For temperature drift compensation, The linear expansion coefficient of the material. Where L is the temperature change and L is the structural length.

[0049] Through temperature compensation, combined with the structural design of the high-rigidity base 4, nanoscale thermal drift can be suppressed, ensuring that the thermal drift of the first and second probes is less than 1 nm when the temperature changes by 1 °C. The distributed multi-point temperature acquisition and thermal drift compensation design, combined with the low thermal expansion characteristics of the high-rigidity base, can control the system's thermal drift to <1 nm / °C. Combined with the temperature compensation algorithm, it effectively offsets measurement errors caused by environmental temperature changes and equipment heat generation, solving the problem of poor thermal stability in traditional systems.

[0050] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

Claims

1. A white light interferometric measurement system, comprising a probe module (1); characterized in that, The probe module (1) is provided with a first probe (2) and a second probe (3); There are multiple second probes (3), and the multiple second probes (3) are distributed around the first probe (2); The first probe (2) is used to emit a first detection light along the axial direction of the first probe (2) and receive the reflected first detection light; the second probe (3) is used to emit a second detection light outward along the radial direction of the second probe (3) and receive the reflected second detection light; The probe module (1) is used to obtain the brightest interference peak of the first detection light and the brightest interference peak of the second detection light during a micro-scan; so as to obtain the measurement point information of the surface of the object being measured or the bottom of the groove through the first probe (2), and obtain the measurement point information of the side wall or groove wall of the object being measured through the second probe (3).

2. The white light interferometry system according to claim 1, characterized in that, The number of the second probes (3) is 4 to 8, and the multiple second probes (3) are arranged in a circular array around the center line of the first probe (2).

3. The white light interferometry system according to claim 2, characterized in that, The second probe (3) is in the same position as the first probe (2) along the axis, and the second probe (3) and the first probe (2) share the same mounting reference surface and the same coordinate system.

4. The white light interferometry system according to claim 1, characterized in that, It also includes a high-rigidity base (4), the probe module (1) is fixedly installed on the high-rigidity base (4), and the positions of the first probe (2) and the second probe (3) relative to the high-rigidity base (4) are fixed.

5. The white light interferometry system according to claim 4, characterized in that, The high-rigidity base (4) includes a connector (5), a connecting rod (6), and a mounting frame (7); the mounting frame (7) is a rectangular frame; The two ends of the connecting rod (6) are fixedly installed at the midpoints of the two parallel sides of the mounting frame (7), and the connector (5) is fixedly installed at the center of the connecting rod (6) so that the high rigidity base (4) dissipates heat to the left and right sides with the connector (5) as the center.

6. The white light interferometry system according to claim 4, characterized in that, The zero optical path difference positions of the first probe (2) and the second probe (3) are the same.

7. The white light interferometry system according to claim 5, characterized in that, The high-rigidity base (4) has a thermal expansion coefficient of less than 1 ppm / ℃ and an elastic modulus of greater than 150 GPa.

8. The white light interferometry system according to claim 5, characterized in that, The probe module (1) is fixedly installed on the connector (5).

9. The white light interferometry system according to claim 8, characterized in that, The connecting rod (6) is fixedly provided with a positioning pin (8); the positioning pin (8) is perpendicular to the mounting frame (7); the connecting piece (5) is connected to the connecting rod (6) by bolts, and the connecting piece (5) is provided with a positioning hole (9) that matches the positioning pin (8).

10. The white light interferometry system according to claim 9, characterized in that, The mounting frame (7) is fixedly mounted on the coordinate measuring machine.

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