System and method for high precision interferometric measurement of parallel mirror group spacing

Abstract

The application relates to a system and method for high-precision interferometric measurement of the spacing of a parallel mirror group. The system comprises: a beam splitter for splitting parallel incident light into a transmitted light beam and a reflected light beam; a plane mirror group composed of first to third plane mirrors; a reference parallel mirror group for generating a first optical path based on the reflected light beam sequentially passing through the third, second and first plane mirrors; a to-be-measured parallel mirror group for generating a second optical path based on the transmitted light beam sequentially passing through the first, second and third plane mirrors; and an upper computer processing module for obtaining an optical path difference from a preset interference fringe group image based on the first optical path and the second optical path, and obtaining the spacing of the to-be-measured parallel mirror group based on the optical path difference. Thus, the system can realize high-precision interferometric measurement, and is especially suitable for measuring the small spacing between parallel mirror groups, and solves the problems of insufficient precision and limited measurement range of traditional interferometric measurement methods.

Description

Technical Field

[0001] This application relates to the field of interferometric measurement technology, and in particular to a system and method for high-precision interferometric measurement of the spacing between parallel reflector groups. Background Technology

[0002] Parallel mirror assemblies are widely used in optoelectronic instruments as optical path deflection mechanisms and optical path changing mechanisms. Non-contact methods for measuring the center thickness of lenses commonly employ physical measurement methods, including image methods, coplanar capacitance methods, axial dispersion methods, confocal methods, and interferometry. Each method has its advantages and disadvantages; therefore, high-precision measurement of the spacing between parallel mirror assemblies remains a technical challenge in the field of precision optical and mechanical measurement.

[0003] In related technologies, a Michelson interferometer system based on low-coherence light is proposed. At appropriate positions in the two optical paths, a wedge prism group with a small wedge angle, an optical parallel plate, and a multi-mirror lens group under test are placed respectively. By continuously moving the second wedge prism of the wedge prism group along the wedge angle facet, the optical path difference during the interference of the two optical paths is precisely adjusted to compensate for the interference. Interference fringes with equal optical path lengths are found between the reflected light from each mirror of the lens group under test and the reflected light from the outward-facing facet adjacent to the wedge angle of the second wedge prism of the wedge prism group with the small wedge angle. The position readings when interference fringes appear during the movement of the second wedge prism are recorded, and the mirror spacing of the multi-mirror lens group is calculated.

[0004] However, the method suffers from insufficient accuracy and limited measurement range, which urgently need to be addressed. Summary of the Invention

[0005] This application provides a system and method for high-precision interferometric measurement of the spacing between parallel reflector groups, which solves the problems of insufficient accuracy and limited measurement range of traditional interferometric measurement methods, and improves the measurement accuracy while expanding the measurement range.

[0006] To achieve the above objectives, the first aspect of this application proposes a system for high-precision interferometric measurement of the spacing between parallel mirror groups, comprising:

[0007] A beam splitter is used to split parallel incident light into a transmitted beam and a reflected beam.

[0008] A plane mirror assembly, comprising a first plane mirror, a second plane mirror, and a third plane mirror;

[0009] The reference parallel mirror group is used to generate a first optical path based on the reflected light beam that passes sequentially through the third plane mirror, the first plane mirror, and the third plane mirror;

[0010] The parallel mirror assembly under test is used to generate a second optical path based on the transmitted light beam that passes sequentially through the first plane mirror, the second plane mirror and the third plane mirror;

[0011] The host computer processing module is used to obtain the optical path difference based on the first optical path and the second optical path, according to a preset interference fringe group image, and to invert the spacing of the parallel mirror group under test based on the optical path difference.

[0012] According to one embodiment of this application, the above-described high-precision interferometric measurement system for the spacing between parallel mirror groups further includes:

[0013] The detection and acquisition module is used to acquire a preset interference fringe image generated by the reflected beam and the transmitted beam.

[0014] According to one embodiment of this application, the above-described high-precision interferometric measurement system for the spacing between parallel mirror groups further includes:

[0015] At least one converging lens is used to converge the interference fringe signals generated by the reflected beam and the transmitted beam onto the detector pixel of the detection and acquisition module to form the preset interference fringe group image.

[0016] According to one embodiment of this application, the above-described high-precision interferometric measurement system for the spacing between parallel mirror groups further includes:

[0017] A front optical module is used to convert incident light into parallel incident light.

[0018] According to one embodiment of this application, the front optical module includes at least one of a converging lens, an aperture stop, a collimating lens, a beam expander, and a filter.

[0019] According to one embodiment of this application, the first planar reflector, the second planar reflector, and the third planar reflector form a quadrilateral asymmetric common optical path architecture.

[0020] According to one embodiment of this application, the beam splitter is a cube-shaped beam splitter, a flat beam splitter, or a prism coated with a semi-transparent, semi-reflective beam splitting film.

[0021] According to one embodiment of this application, the pose adjustment method of the reference parallel mirror group is mechanical adjustment.

[0022] According to one embodiment of this application, the pose adjustment method of the reference parallel reflector group is motor adjustment.

[0023] The system for high-precision interferometric measurement of the spacing between parallel mirror groups proposed in this application splits parallel incident light into a transmitted beam and a reflected beam using a beam splitter. A first optical path is generated based on the reflected beam passing through the third, second, and first plane mirrors sequentially, using a reference parallel mirror group. A second optical path is generated based on the transmitted beam passing through the first, second, and third plane mirrors sequentially, using the parallel mirror group under test. A host computer processing module obtains the optical path difference based on the first and second optical paths and a preset interference fringe image, and then inverts the spacing of the parallel mirror group under test based on the optical path difference. Therefore, this system enables high-precision interferometric measurement, particularly suitable for measuring minute spacing between parallel mirror groups. It solves the problems of insufficient accuracy and limited measurement range in traditional interferometric methods, improving measurement accuracy while expanding the measurement range.

[0024] To achieve the above objectives, a second aspect of this application proposes a method for high-precision interferometric measurement of the spacing between parallel mirror groups, employing the high-precision interferometric measurement system for parallel mirror group spacing described in the first aspect embodiment, wherein the method includes the following steps:

[0025] The first incident parallel light converted by the front optical module is controlled to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the first preset optical path, and the spacing of the reference parallel mirror group is adjusted to meet the preset conditions to generate interference fringes.

[0026] And / or, control the second incident parallel light converted by the front optical module to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the second preset optical path to obtain an interference fringe group image, and adjust the spacing of the reference parallel mirror group based on the interference fringe group image so that the difference between the two sets of interference fringes in the interference fringe group image is within one period;

[0027] The displacement of the interference fringe image is extracted, and the spacing of the parallel mirror group under test is obtained based on the displacement of the interference fringe image.

[0028] The method for high-precision interferometric measurement of the spacing between parallel mirror groups proposed in the embodiments of this application solves the problems of insufficient accuracy and limited measurement range of traditional interferometric measurement methods by using a system for high-precision interferometric measurement of the spacing between parallel mirror groups, thereby improving measurement accuracy while expanding the measurement range.

[0029] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0030] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram of the architecture of a system for high-precision interferometric measurement of the spacing between parallel reflector groups according to an embodiment of this application;

[0032] Figure 2 This is a schematic diagram of an application system for high-precision interferometric measurement of the spacing between parallel reflecting mirror groups using white light as the incident light, according to an embodiment of this application.

[0033] Figure 3 This is a schematic diagram of an application system for high-precision interferometric measurement of parallel reflector group spacing technology using laser as incident light, according to another embodiment of this application;

[0034] Figure 4 This is a flowchart of a method for high-precision interferometric measurement of the spacing between parallel reflector groups according to an embodiment of this application. Detailed Implementation

[0035] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0036] The system and method for high-precision interferometric measurement of the spacing between parallel mirror groups according to embodiments of this application will now be described with reference to the accompanying drawings. First, the system for high-precision interferometric measurement of the spacing between parallel mirror groups according to embodiments of this application will be described with reference to the accompanying drawings.

[0037] Figure 1 This is a block diagram of a system for high-precision interferometric measurement of the spacing between parallel reflector groups according to an embodiment of this application.

[0038] For example, such as Figure 1 As shown, the high-precision interferometric measurement system 10 for the spacing of parallel mirror groups includes: a beam splitter 100, a plane mirror group 200, a reference parallel mirror group 300, a parallel mirror group under test 400, and a host computer processing module 500.

[0039] The beam splitter 100 is used to split parallel incident light into a transmitted beam and a reflected beam; the plane mirror group 200 includes a first plane mirror 201, a second plane mirror 202 and a third plane mirror 203; the reference parallel mirror group 300 is used to generate a first optical path based on the reflected beam that passes through the third plane mirror 203, the second plane mirror 202 and the first plane mirror 201 in sequence; the parallel mirror group 400 under test is used to generate a second optical path based on the transmitted beam that passes through the first plane mirror 201, the second plane mirror 202 and the third plane mirror 203 in sequence; the host computer processing module 500 is used to obtain the optical path difference based on the first optical path and the second optical path, according to a preset interference fringe group image, and to obtain the spacing of the parallel mirror group 400 under test based on the optical path difference.

[0040] It is understandable that when two or more coherent light waves meet, they will reinforce or weaken each other in certain regions of space, forming alternating bright and dark fringes, known as interference fringes. Optical path difference refers to the difference in path length traversed by two beams of light as they propagate in the same or different media.

[0041] Specifically, such as Figure 1 As shown, the high-precision interferometric measurement system 10 for parallel mirror group spacing proposed in this application consists of a quadrilateral common-path interferometer, a reference parallel mirror group 300, a parallel mirror group under test 400, and a host computer processing module 500. The quadrilateral common-path interferometer includes a beam splitter 100 and a plane mirror group 200. The reference parallel mirror group 300 and the parallel mirror group under test 400 are respectively placed in the two arms of the quadrilateral common-path interferometer (these two arms are separate optical paths, which will converge at a certain point). When two beams of light (i.e., the transmitted beam and the reflected beam) propagate in the two arms of the quadrilateral common-path interferometer, the two arms can generate their own optical paths, namely, the first optical path and the second optical path. The difference between these two optical paths (i.e., the optical path difference) can be measured by the preset interference fringe image generated by the quadrilateral common-path interferometer. The host computer processing module 500 can calculate the distance difference between the reference parallel mirror group 300 and the parallel mirror group 400 under test by processing (such as preprocessing, error correction and other restoration processes) and analyzing the optical path difference, and thus obtain the distance information of the parallel mirror group 400 under test.

[0042] Furthermore, depending on the accuracy requirements, the incident beam 1 can be selected from either a broad-spectrum light source such as white light or a halogen lamp, or a narrow-spectrum light source such as a laser. A quadrilateral common-path interferometer is positioned on the optical path of the incident beam 1, and the incident position of the incident beam 1 must be within the effective range of the beam splitter 100 and close to one side of the overall optical path of the quadrilateral common-path interferometer. The incident beam 1 is split into two beams (a transmitted beam and a reflected beam) by the beam splitter 100, and after reflection by the plane mirror group 200, the reference parallel mirror group 300, and the parallel mirror group under test 400, the target interference beam 2 is finally obtained. The plane mirror group 200 is used to change the spatial path of the beam. It is designed as an asymmetrical structure, that is, the first plane mirror 201, the second plane mirror 202 and the third plane mirror 203 are not strictly symmetrical about the beam splitting plane axis, but have a certain translation (the amount of translation depends on the diameter of the beam and the spatial size of the structure required by the design, which is not specifically limited here). This allows the transmitted beam and the reflected beam after beam splitting to pass through different paths of the first plane mirror 201, the second plane mirror 202 and the third plane mirror 203. However, apart from the plane mirror group 200, the other components are the same, thus forming a common-path interferometer.

[0043] In addition, when adjusting the translation of the mirrors in the plane mirror group 200, the reflected beam should ultimately be able to pass smoothly through the reference parallel mirror group 300 after passing through the plane mirror group 200, and the transmitted beam should be able to pass smoothly through the parallel mirror group 400 under test after passing through the plane mirror group 200. Furthermore, the optical path of the reflected beam passing through the third plane mirror 203, the second plane mirror 202, and the first plane mirror 201 in sequence should be spatially separated from the optical path of the transmitted beam passing through the first plane mirror 201, the second plane mirror 202, and the third plane mirror 203 in sequence before returning to the beam splitter 100. After the two optical paths return to the beam splitter 100, the beams rejoin to obtain the target interference beam 2.

[0044] Optionally, in some embodiments, the first planar reflector 201, the second planar reflector 202, and the third planar reflector 203 form a quadrilateral asymmetric common optical path architecture.

[0045] Understandably, a common-path architecture refers to an optical system where light rays share the same path as a series of optical elements (such as mirrors and lenses). This design reduces the complexity of the optical system and improves its stability and accuracy. Quadrilateral asymmetry refers to a quadrilateral structure composed of plane mirrors that is not symmetrical. Asymmetry means that the side lengths, angles, or arrangement of the mirrors are not exactly the same.

[0046] Therefore, by spatially separating the optical path, the asymmetric structure avoids systematic errors that may be caused by device symmetry deviations in the symmetric common optical path (such as the effect of beam splitter splitting ratio error on the difference between the two arms), thereby improving measurement accuracy.

[0047] Optionally, in some embodiments, the beam splitter 100 is a cube-shaped beam splitter, a planar beam splitter, or a prism coated with a semi-transparent, semi-reflective beam splitting film.

[0048] As is understood, a beam splitter is an optical element used to divide an incident light beam into two or more parts, which may have different intensity ratios. Beam splitters are widely used in optical experiments and optical systems, such as interferometers, lasers, and optical measurement equipment. In the embodiments of this application, the beam splitter 100 has a splitting ratio of 1:1. It can be a cubic beam splitter or a planar beam splitter. If the interferometer is a solid structure, it can also be achieved by coating the prisms that make up the interferometer with a semi-transparent, semi-reflective beam-splitting film.

[0049] Cube-type beam splitters consist of a cubic structure formed by bonding two right-angled prisms together. A semi-transparent, semi-reflective coating is deposited on the bonding surface of the two prisms. When light is incident on this cube, part of the light is reflected, and the rest is transmitted. The advantage of this structure is its good stability and insensitivity to the polarization state of the incident light. Planar-type beam splitters typically consist of a single glass plate with a semi-transparent, semi-reflective coating deposited on one side. When light is incident on this coated surface, part of the light is reflected, and the rest is transmitted. The advantages of planar beam splitters are their simple structure and low cost. Prism beam splitters, using prisms with semi-transparent, semi-reflective coatings, utilize the principles of refraction and reflection of prisms, combined with a semi-transparent, semi-reflective coating, to achieve beam splitting. These beam splitters typically consist of one or more prisms, one of which has a semi-transparent, semi-reflective coating on its surface. Prism beam splitters can be designed in different shapes and structures to adapt to different optical systems and application requirements.

[0050] Optionally, in some embodiments, the pose adjustment of the reference parallel mirror assembly 300 is mechanically adjusted.

[0051] Alternatively, in some other embodiments, the pose adjustment method of the reference parallel reflector group 300 is motor adjustment.

[0052] In other words, the pose (spacing) of the reference parallel reflector group 300 is adjustable. Adjustment methods include manual mechanical adjustment and motor adjustment, with the motor controlled by the host computer processing module 500. Each of these adjustment methods has its advantages: mechanical adjustment is suitable for applications requiring less frequent adjustments, while motor adjustment is suitable for applications requiring rapid response and automated control.

[0053] Optionally, in some embodiments, the system 10 for high-precision interferometric measurement of the spacing between parallel reflector groups further includes: a detection and acquisition module 600 for acquiring a preset image of the interference fringe group generated by the reflected beam and the transmitted beam.

[0054] Specifically, such as Figure 2 and Figure 3 As shown, the system 10 for high-precision interferometric measurement of the spacing between parallel mirror groups is also equipped with a detection and acquisition module 600 (such as a CCD (Charge Coupled Device) camera). The main function of the detection and acquisition module 600 is to capture images of a preset set of interference fringes generated by the interaction of the reflected and transmitted beams. By accurately acquiring these images, the system can further analyze and calculate the precise spacing of the parallel mirror group 400 under test, thereby ensuring the high precision and reliability of the entire measurement process.

[0055] Optionally, in some embodiments, the system 10 for high-precision interferometric measurement of the spacing between parallel reflector groups further includes: at least one converging mirror 700 for converging the interference fringe signals generated by the reflected beam and the transmitted beam onto the detector pixel of the detection and acquisition module 600 to form a preset interference fringe group image.

[0056] Specifically, such as Figure 2 and Figure 3 As shown, the system 10 for high-precision interferometric measurement of the spacing between parallel reflecting mirror groups also includes at least one converging mirror 700 (a single converging mirror or a group of converging mirrors, the latter facilitating aberration elimination), which can be either refractive or reflective. It is responsible for effectively converging and imaging the interference fringe signals generated by the interaction of the reflected and transmitted beams onto the detector pixels of the detection and acquisition module 600. This ensures the formation of a clear, pre-defined interference fringe image, thereby improving measurement accuracy and reliability.

[0057] Optionally, in some embodiments, the system 10 for high-precision interferometric measurement of the spacing between parallel mirror groups further includes a front optical module 800 for converting incident light into parallel incident light.

[0058] Specifically, such as Figure 2 and Figure 3As shown, the system 10 for high-precision interferometric measurement of the spacing between parallel mirror groups is also equipped with a front optical module 800, which is positioned in front of the quadrilateral common-path interferometer. This module receives incident light from the light source and, through a series of precise optical processes, converts the incident light into a parallel beam. This conversion is essential for ensuring measurement accuracy and reliability, because only when the incident beam achieves sufficient parallelism can the accurate determination of the spacing between the parallel mirror groups be guaranteed during the measurement process, providing a solid foundation for achieving high-precision interferometric measurement.

[0059] It should be noted that, depending on the incident light source, a suitable front optical module 800 can be selected so that the beam entering the beam splitter 100 is a collimated beam with appropriate spot size and intensity.

[0060] In some embodiments, the front optical module 800 includes at least one of a converging lens 801, an aperture 802, a collimating lens 803, a beam expander 804, and a filter 805.

[0061] In other words, such as Figure 2 and Figure 3 As shown, the front optical system 800 consists of a series of optical elements, each with its specific function and position. Specifically, the front optical system 800 includes, in sequence, a converging lens 801, an aperture stop 802, a collimating lens 803, a beam expander 804, and a filter 805. The parameters of these elements can be dynamically adjusted according to the incident light source. Specifically, the converging lens 801 focuses the light; the aperture stop 802 limits the area through which the light passes, controlling the size of the beam; the collimating lens 803 parallelizes the light rays, maintaining a consistent direction; the beam expander 804 further enlarges the diameter of the beam; and the filter 805 selects light of a specific wavelength, filtering out unwanted light. The entire system adapts to different incident light sources by adjusting the parameters of these elements to achieve optimal optical performance.

[0062] Specifically, after the incident beam 1 enters the front optical module 800, it passes sequentially through the converging lens 801, the aperture 802, the collimating lens 803, the beam expander 804, and the filter 805. First, the converging lens 801 converges the light, the aperture 802 filters and limits the shape of the image plane of the converging lens 801 and prevents stray light, and then the collimating lens 803 collimates the light, making the light passing through the front optical module 800 parallel light. The filter 805 can reduce the light intensity, reduce stray light and prevent overexposure, and the beam expander 804 can enlarge the incident beam 1 to obtain clearer interference fringes.

[0063] The front optical module 800 can employ various forms such as refraction, catadioptric reflection, and total internal reflection, with the aim of converting the incident light from the target into parallel rays. Depending on the different stages of the measurement process, the optical elements within the front optical module 800 can be added or removed based on the light source used. For example, when the light source is fiber optic, a suitable collimating lens 803 should be used; when the light source is a point source, a suitable beam expander 804 should be used.

[0064] To facilitate a better understanding by those skilled in the art of the high-precision interferometric measurement system 10 for parallel reflector group spacing proposed in the embodiments of this application, the following is in conjunction with... Figure 2 and Figure 3 To elaborate further.

[0065] In practical applications, both white light and laser light sources can be used simultaneously. For example... Figure 2 As shown, when the incident beam 1 is emitted from the white light source 3, passes through the pre-optical module 800, and is incident on the quadrilateral common-path interferometer, the beam splitter 100 of the quadrilateral common-path interferometer can split the parallel incident light into a first transmitted beam and a first reflected beam. The first reflected beam can pass through the third plane mirror 203, the second plane mirror 202, and the first plane mirror 201 in the plane mirror group 200 in sequence, and then reach the reference parallel mirror group 300. It is reflected back to the beam splitter 100 by the reference parallel mirror group 300, thereby generating the first optical path. The first transmitted beam can pass through the first plane mirror 201, the second plane mirror 202, and the third plane mirror 203 in the plane mirror group 200 in sequence, and then reach the parallel mirror group 400 under test. After being reflected twice by the two parallel mirrors in the parallel mirror group 400 under test, it returns to the beam splitter 100 within the effective range of the beam splitter 100, thereby generating the second optical path.

[0066] Understandably, the first transmitted beam travels in a certain direction before entering the parallel mirror assembly 400 under test. After entering the assembly, it undergoes two reflections, altering its path (i.e., it no longer coincides spatially with its original path). Since the two mirrors within the assembly 400 are parallel, the two reflections cause a lateral displacement of the first transmitted beam. This displacement is determined by the distance between the two mirrors. For example, a larger distance results in a larger displacement, and vice versa.

[0067] Furthermore, the two beams of light reflected back to the beam splitter 100 by the reference parallel mirror group 300 and the parallel mirror group 400 under test can be split again by the beam splitter 100 to form four beams. That is, the first transmitted beam is split into a second transmitted beam and a second reflected beam by the beam splitter 100, and the first reflected beam is split into a third transmitted beam and a third reflected beam by the beam splitter 100. Among them, the second reflected beam and the third transmitted beam can generate one interference beam, which propagates along the parallel light incident direction, and the second transmitted beam and the third reflected beam can generate another interference beam, which propagates along a direction perpendicular to the parallel light incident direction. At this time, the reference parallel mirror group 300 and the parallel mirror group under test 400 are both at an angle of 45 degrees to the horizontal direction. By adjusting the spacing of the reference parallel mirror group 300, the spacing difference between the reference parallel mirror group 300 and the parallel mirror group under test 400 is within the coherence length of the corresponding parallel incident light, thus forming a target interference beam 2 that propagates perpendicular to the incident direction of the parallel light. After passing through at least one converging mirror 700, the target interference beam 2 reaches the detector pixel of the detection and acquisition module 600, and the host computer processing module 500 observes and collects the interference image (i.e., the preset interference fringe group image) of the interference light propagating perpendicular to the incident direction of the parallel light.

[0068] Next, as Figure 3 As shown, the white light source is replaced with a laser source, and the corresponding front optical module 800 is replaced accordingly. The incident beam 1 emitted by the laser source 4 is also split into a first transmitted beam and a first reflected beam by the beam splitter 100 of the quadrilateral common-path interferometer. By adjusting the positions of the reference parallel mirror group 300 and the parallel mirror group under test 400, that is, by translating the reference parallel mirror group 300 and the parallel mirror group under test 400 towards the quadrilateral common-path interferometer, a designated portion of the first transmitted beam reaches the beam splitter 100 through the parallel mirror group under test 400, while the remaining portion of the first transmitted beam reaches the beam splitter 100 without passing through the parallel mirror group under test 400. Similarly, a designated portion of the first reflected beam reaches the beam splitter 100 through the reference parallel mirror group 300, while the remaining portion of the first reflected beam reaches the beam splitter 100 without passing through the reference parallel mirror group 300.

[0069] Furthermore, a designated portion of the first transmitted beam, after passing through the parallel mirror group 400 under test and reaching the beam splitter 100, is split into a second transmitted beam and a second reflected beam. A designated portion of the first reflected beam, after passing through the reference parallel mirror group 300 and reaching the beam splitter 100, is split into a third transmitted beam and a third reflected beam. The remaining portion of the first transmitted beam, without passing through the parallel mirror group 400 under test, reaches the beam splitter 100 and is split into a fourth transmitted beam and a fourth reflected beam. The remaining portion of the first reflected beam, without passing through the reference parallel mirror group 300, reaches the beam splitter 100 and is split into a fifth transmitted beam and a fifth reflected beam. Ideally, the designated portion and the remaining portion of the same beam should be in a 1:1 ratio.

[0070] At this point, the second transmitted beam and the third reflected beam generate a first interference image, which is received and observed by the host computer processing module 500. The fourth transmitted beam and the fifth reflected beam generate a second interference image, which is also received and observed by the host computer processing module 500. Observation reveals that the first and second interference images present as staggered semi-circular interference images, with the upper part of the image showing the fringes of the first interference image and the lower part showing the fringes of the second interference image. By comparing the periods of these first and second interference images, the distance difference between the parallel mirror group 400 under test and the reference parallel mirror group 300 can be accurately measured. The distance can then be adjusted accordingly to achieve a final measurement accuracy within one interference fringe period. Thus, the distance information of the parallel mirror group 400 under test can be accurately obtained.

[0071] Furthermore, the high-precision interferometric measurement system 10 for the spacing between parallel mirror groups proposed in this application embodiment can also be used for the fine-tuning process of comparing two sets of parallel mirror groups. This can be achieved by replacing the reference parallel mirror group 300 with the standard parallel mirror group and replacing the parallel mirror group 400 to be measured with the mirror group that needs fine-tuning.

[0072] Therefore, the high-precision interferometric measurement system 10 for the spacing of parallel reflector groups proposed in this application has the following advantages:

[0073] (1) High precision. Compared to the traditional method of adjusting the spacing of parallel mirror groups in white-light Michelson interferometry, the embodiments of this application omit the step of pre-adjusting the two arms of the interferometer, effectively reducing errors. In the embodiments of this application, the optical path lengths of the two arms of the interferometer are already consistent before the introduction of the parallel mirror group, thereby directly achieving a stable zero optical path difference. In addition, the embodiments of this application also allow simultaneous observation of the interference fringes processed by the parallel mirror group and the interference fringes of the original optical path with zero optical path difference, controlling the error within a specific interference period, thereby improving the precision of adjustment.

[0074] (2) High stability. The embodiments of this application employ a common-path interferometry system, which significantly improves stability. Compared to the non-common-path interferometry system used in traditional Michelson interferometry, the latter is susceptible to external thermodynamic factors, leading to changes in optical path difference and instability in the displacement and phase of interference fringes, resulting in significant instrument errors and affecting the accuracy of high-precision measurements. By applying common-path beam splitting technology, external thermodynamic changes act simultaneously on both arms of the interferometer, causing the resulting optical path difference to cancel each other out, resulting in more stable interference fringes. Consequently, the stability of the interferometer is also improved.

[0075] (3) High operability. The original asymmetric common optical path system can be fixed after adjustment, and no further redundant adjustments are required. During the measurement process, it is only necessary to place the mirror group under test into the optical path and make preliminary adjustments to the reference parallel mirror so that the distance between it and the mirror under test is significantly greater than or less than the expected value before fixing it in the optical path. Subsequently, fine-tuning is performed on the distance between the mirrors under test until the desired result is observed.

[0076] The system for high-precision interferometric measurement of the spacing between parallel mirror groups proposed in this application splits parallel incident light into transmitted and reflected beams using a beam splitter. A first optical path is generated based on the reflected beams passing sequentially through the first, second, and third plane mirrors of a reference parallel mirror group. A second optical path is generated based on the transmitted beams passing sequentially through the third, second, and first plane mirrors of the parallel mirror group under test. A host computer processing module calculates the optical path difference based on the first and second optical path differences and a preset interference fringe image, and then inverts the spacing of the parallel mirror group under test based on this optical path difference. Therefore, this system enables high-precision interferometric measurement, particularly suitable for measuring minute spacing between parallel mirror groups. It solves the problems of insufficient accuracy and limited measurement range in traditional interferometric methods, improving measurement accuracy while expanding the measurement range.

[0077] Next, referring to the accompanying drawings, a method for high-precision interferometric measurement of the spacing between parallel reflector groups according to an embodiment of this application is described.

[0078] Figure 4 This is a flowchart of a method for high-precision interferometric measurement of the spacing between parallel reflector groups according to an embodiment of this application.

[0079] like Figure 4 As shown, this high-precision interferometric measurement method for the spacing of parallel mirror groups employs... Figure 1 The system for high-precision interferometric measurement of the spacing between parallel mirror groups, as described in this embodiment, includes the following steps:

[0080] In step S401, the first incident parallel light converted by the front optical module is controlled to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the first preset optical path, and the spacing of the reference parallel mirror group is adjusted to meet the preset conditions to generate interference fringes.

[0081] In step S402, and / or, the second incident parallel light converted by the front optical module is controlled to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the second preset optical path to obtain an interference fringe group image, and the spacing of the reference parallel mirror group is adjusted based on the interference fringe group image so that the difference between the two sets of interference fringes in the interference fringe group image is within one period.

[0082] In step S403, the displacement of the interference fringe group image is extracted, and the spacing of the parallel mirror group to be tested is obtained based on the displacement of the interference fringe group image.

[0083] It should be noted that the explanation of the system embodiment for high-precision interferometric measurement of the spacing between parallel mirror groups, as described above, also applies to the method for high-precision interferometric measurement of the spacing between parallel mirror groups in this embodiment, and will not be repeated here.

[0084] The method for high-precision interferometric measurement of the spacing between parallel mirror groups proposed in the embodiments of this application solves the problems of insufficient accuracy and limited measurement range of traditional interferometric measurement methods by using a system for high-precision interferometric measurement of the spacing between parallel mirror groups, thereby improving measurement accuracy while expanding the measurement range.

[0085] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0086] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0087] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A system for high-precision interferometric measurement of the spacing between parallel reflecting mirror groups, characterized in that, include: A beam splitter is used to split parallel incident light into a transmitted beam and a reflected beam. A plane mirror assembly, comprising a first plane mirror, a second plane mirror, and a third plane mirror; The reference parallel mirror group is used to generate a first optical path based on the reflected light beam that passes sequentially through the third plane mirror, the second plane mirror and the first plane mirror; The parallel mirror assembly under test is used to generate a second optical path based on the transmitted light beam that passes sequentially through the first plane mirror, the second plane mirror and the third plane mirror; The host computer processing module is used to obtain the optical path difference based on the first optical path and the second optical path, according to a preset interference fringe group image, and to invert the spacing of the parallel mirror group under test based on the optical path difference.

2. The system according to claim 1, characterized in that, Also includes: The detection and acquisition module is used to acquire a preset interference fringe image generated by the reflected beam and the transmitted beam.

3. The system according to claim 2, characterized in that, Also includes: At least one converging lens is used to converge the interference fringe signals generated by the reflected beam and the transmitted beam onto the detector pixel of the detection and acquisition module to form the preset interference fringe group image.

4. The system according to claim 1, characterized in that, Also includes: A front optical module is used to convert incident light into parallel incident light.

5. The system according to claim 4, characterized in that, The front optical module includes at least one of a converging lens, an aperture stop, a collimating lens, a beam expander, and a filter.

6. The system according to claim 1, characterized in that, The first planar reflector, the second planar reflector, and the third planar reflector form a quadrilateral asymmetric common optical path architecture.

7. The system according to claim 1, characterized in that, The beam splitter is a cube-shaped beam splitter, a flat beam splitter, or a prism coated with a semi-transparent, semi-reflective beam splitting film.

8. The system according to claim 1, characterized in that, The orientation adjustment method of the reference parallel reflector group is mechanical adjustment.

9. The system according to claim 8, characterized in that, The orientation adjustment method for the reference parallel reflector group is motor adjustment.

10. A method for high-precision interferometric measurement of the spacing between parallel reflecting mirror groups, characterized in that, A system for high-precision interferometric measurement of the spacing between parallel reflector groups as described in any one of claims 1-9, wherein the method comprises the following steps: The first incident parallel light converted by the front optical module is controlled to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the first preset optical path, and the spacing of the reference parallel mirror group is adjusted to meet the preset conditions to generate interference fringes. And / or, control the second incident parallel light converted by the front optical module to pass through the beam splitter, the plane mirror group, the reference parallel mirror group and the parallel mirror group under test according to the second preset optical path to obtain an interference fringe group image, and adjust the spacing of the reference parallel mirror group based on the interference fringe group image so that the difference between the two sets of interference fringes in the interference fringe group image is within one period; The displacement of the interference fringe image is extracted, and the spacing of the parallel mirror group under test is obtained based on the displacement of the interference fringe image.

Images