Detection method and system for separation of inclination error and eccentric error of optical mirror surface

Abstract

The invention provides a method and a system for detecting inclination and eccentricity error separation of an optical mirror surface, and belongs to the technical field of optical detection. According to the method, a non-contact range finder is used for measuring height data of a mirror surface to be measured when the mirror surface rotates for a circle at two different calibers, a relational expression of height data change and inclination and eccentricity is established through a least square method, and accurate measurement and separation of inclination and eccentricity errors are achieved. The system comprises an air floating rotary table, a non-contact measuring head and test software, the rotary table rotates during measurement, the measuring head collects data, and the software processes and outputs a result. The method solves the problem of mutual conversion between inclination and eccentricity when a traditional method is used for measuring the aspherical mirror, improves the measurement precision and the adjustment efficiency, and is suitable for detection and adjustment of the high-precision aspherical mirror.

Description

Technical Field

[0001] This invention relates to the field of optics, and specifically to a detection method and system for separating optical mirror tilt and eccentricity errors. Background Technology

[0002] Aspherical lenses are increasingly used in the design, manufacturing and assembly of optical systems, and their unique curved surface design can significantly improve the imaging quality and performance of optical systems.

[0003] However, the tilt and decenter errors of aspherical lenses are key factors affecting the imaging quality of the system and have a crucial impact on the overall performance of the optical system.

[0004] Traditionally, the measurement of tilt and eccentricity errors of aspherical lenses has mainly relied on optical center deviation measuring instruments, including reflective optical center deviation measuring instruments and transmissive optical center deviation measuring instruments.

[0005] Among them, the dual-path reflective optical center deviation measuring instrument is widely used in actual production due to its high measurement accuracy and efficiency.

[0006] The instrument uses autocollimators set on the upper and lower sides of the mirror under test. Parallel light is used to illuminate the mirror surface and converge to the crosshair image at the focal point. The center deviation is calculated by evaluating the runout of the crosshair image.

[0007] However, traditional methods have significant limitations.

[0008] Because the lens aperture of the center deviation measuring instrument is usually small, the light can only illuminate a small area of ​​the center of the mirror to be measured. Therefore, it is mainly suitable for measuring spherical mirrors and plane mirrors.

[0009] For aspherical lenses, due to the difference in the radius of curvature at different apertures, traditional methods are prone to the conversion between tilt and eccentricity during measurement, resulting in inaccurate measurement results and affecting the efficiency of subsequent assembly and adjustment.

[0010] Specifically, when using a traditional center offset measuring instrument to measure aspherical lenses, due to the limitation of the measuring aperture, the instrument can often only capture data in the central area of ​​the lens. The curvature change of the aspherical lens at different apertures will cause the light propagation path to change, which will cause tilt and eccentricity errors to be converted into each other during the measurement process, affecting the measurement accuracy and having a great impact on the subsequent assembly and adjustment of the optical system.

[0011] Furthermore, when dealing with complex curved surfaces or specially designed aspherical lenses, traditional measurement methods often require the use of other tools to monitor edge runout, which not only increases measurement costs and time but may also introduce additional errors.

[0012] To address the aforementioned issues, the applicant proposes a detection method and system for separating optical mirror tilt and eccentricity errors. Summary of the Invention

[0013] The purpose of this invention is to provide a detection method and system for separating optical mirror tilt and eccentricity errors, so as to solve the problems in the prior art.

[0014] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting the separation of optical mirror tilt and eccentricity errors, the method comprising the following steps:

[0015] Using a non-contact probe based on the confocal ranging principle, the height data of the lens during one revolution is measured at two different preset apertures of the lens under test.

[0016] By fitting the measured height data changes using the least squares method, mathematical relationships between the height data changes and the tilt and eccentricity were established.

[0017] Based on the established mathematical relationship, the tilt and eccentricity of the lens under test are calculated, thus achieving accurate measurement and separation of tilt and eccentricity errors.

[0018] A detection system for measuring and separating optical mirror tilt and eccentricity errors, the system comprising:

[0019] An air-bearing turntable is used to support and rotate the lens under test, ensuring stability and accuracy during the rotation process;

[0020] Non-contact probe and related mounting equipment, with at least one set of non-contact probe, capable of being mounted and measured at different preset apertures of the lens to be tested;

[0021] Measurement and data processing software is used to control the probe to collect data, process and display measurement results, and obtain the relationship between the mirror height change and tilt and eccentricity by fitting the least squares method, and calculate the tilt and eccentricity.

[0022] Optionally, during measurement, the non-contact probe rotates the lens under test at least once at two different preset apertures, collecting height data during the lens rotation process for subsequent data processing and analysis.

[0023] Optionally, the measurement and data processing software further includes:

[0024] The data processing module is used to receive and process the height data collected by the non-contact probe, and obtain the relationship between the mirror height change and tilt and eccentricity by fitting the data using the least squares method.

[0025] The result output and display module is used to output the calculated tilt and eccentricity in numerical form and display them in real time on the detection software interface;

[0026] Optionally, when processing data, the measurement and data processing software needs to use at least one set of non-contact probes to collect height data at two different preset diameters for a single measurement surface in order to establish an accurate calculation model for tilt and eccentricity.

[0027] Optionally, the system is suitable for tilt and eccentricity detection of various aspherical lenses, which can significantly improve detection accuracy and assembly efficiency. It also has a large measurement aperture, avoiding the problem of tilt and eccentricity conversion caused by aperture limitations in traditional methods.

[0028] Beneficial effects: Improves measurement accuracy and increases measurement efficiency.

[0029] This invention introduces a non-contact rangefinder to measure the tilt and eccentricity errors of aspherical lenses within a large aperture range, effectively avoiding the problem of tilt and eccentricity conversion caused by the small measurement aperture of traditional center offset measuring instruments.

[0030] Achieve independent solutions for tilt and eccentricity errors:

[0031] This invention utilizes a confocal distance measuring probe to measure the height data of a lens rotating one revolution at two different apertures. By using the least squares method, a mathematical relationship is established between the change in height data and the tilt and eccentricity, thus achieving independent solution for tilt and eccentricity errors.

[0032] This innovation effectively solves the problem of inaccurate separation between tilt and eccentricity in the measurement of center offset of aspherical lenses in traditional methods, thus improving the accuracy of error measurement.

[0033] Improve assembly and adjustment efficiency and reduce manual calculation workload:

[0034] The present invention can obtain complete tilt and eccentricity information in a single measurement, without the need for multiple adjustments and remeasurements, which significantly reduces measurement time and cost.

[0035] The detection method and system of this invention are applicable to the tilt and eccentricity detection of various aspherical lenses. Furthermore, this method can be used in conjunction with surface shape detection equipment to monitor center offset and surface shape changes in real time during lens assembly and adjustment, providing strong support for the assembly and adjustment of optical systems. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0037] Figure 2 This is a side view of an embodiment of the present invention.

[0038] In the diagram: 1. Air-bearing turntable; 2. Mirror under test; 3. Confocal distance measuring probe. Detailed Implementation

[0039] The preferred embodiments of the present invention are described below with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0040] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0041] Detection Method and System Implementation for Separating Optical Mirror Tilt and Eccentricity Errors

[0042] In the field of optics, the processing precision and quality of optical mirrors play a crucial role in the performance of optical systems. Among these, the tilt and eccentricity errors of the mirror are key factors affecting the imaging quality of optical systems. Traditional detection techniques suffer from problems such as the conversion between tilt and eccentricity errors due to small-aperture measurements when measuring the center offset of aspherical mirrors, affecting measurement accuracy. To address these issues, this invention proposes an innovative detection method and system for separating the tilt and eccentricity errors of optical mirrors. The following will provide a comprehensive and detailed description of the specific implementation of this method and system, covering several key aspects such as system architecture design, measurement process, data processing methods, and error compensation strategies.

[0043] The detection system of the present invention mainly consists of three parts: an air-bearing turntable, a non-contact probe and its mounting device, and measurement and data processing software. Each part works together to achieve high-precision detection of optical mirror tilt and eccentricity errors.

[0044] air flotation turntable

[0045] The air-bearing turntable, as the rotating platform of the system, is not necessarily a dedicated component. When used in conjunction with a surface shape detection system, the turntable of a surface shape detection device can also be utilized. The turntable is equipped with a high-precision motor drive, which allows it to rotate at a uniform speed to obtain uniform data. The turntable is also equipped with an angle encoder, which can provide real-time and accurate feedback on the turntable's rotation angle and speed information.

[0046] Non-contact probe

[0047] The non-contact probe employs a design based on the confocal ranging principle. Confocal ranging is a distance measurement method based on optical focusing characteristics, offering advantages such as high precision, high speed, and non-contact measurement. This probe can accurately capture minute height changes on the lens surface, achieving measurement accuracy at the micrometer or even nanometer level, meeting the requirements for high-precision optical mirror inspection. Furthermore, its non-contact measurement method avoids potential damage and transformation to the lens surface caused by traditional contact measurements, ensuring the accuracy and reliability of the measurement results.

[0048] probe mounting device

[0049] The probe mounting device consists of three main parts: a support, an adjustment mechanism, and a fixing device. The support provides a stable mechanical structure for the entire probe system. The adjustment mechanism features multi-degree-of-freedom adjustment, allowing for precise adjustment of the probe's position and angle in space via a sophisticated mechanical transmission system. This enables the probe to accurately aim at the measurement point of the lens under test, ensuring the accuracy of the measurement data. The fixing device securely fixes the probe to the support after it has been adjusted, preventing it from shaking or shifting during measurement, thus ensuring the stability and repeatability of the measurement process.

[0050] The measurement and data processing software is the intelligent core of the entire detection system. It is responsible for controlling the probe to collect data, processing and displaying the measurement results, and calculating the tilt and eccentricity through advanced algorithms.

[0051] First, adjust the parallelism of the plane reference of the air flotation platform to near zero, and carefully place the lens to be tested on the air flotation turntable. During the placement process, try to avoid collisions and damage to the lens, and adjust the center of the lens to coincide with the rotation axis of the air flotation platform.

[0052] Single probe configuration

[0053] For a single-probe configuration, depending on the measurement requirements, the probe is slowly moved to the first measurement point, such as the large-diameter section, using the adjustment mechanism. At this point, the lens is rotated one full turn while simultaneously measuring the mirror height during that rotation. The probe is then moved to another measurement point, such as the small-diameter section, and the above operation is repeated to obtain two sets of data.

[0054] Multi-probe configuration

[0055] When using a multi-probe configuration, the main requirement is to ensure that each probe collects data equivalent to at least one full rotation of the mirror.

[0056] Start the air-bearing turntable and allow it to rotate at a set, uniform speed. Simultaneously, activate the non-contact probe to begin data acquisition. During one rotation of the turntable, the probe continuously collects height data from the lens surface and transmits this data in real-time to the measurement and data processing software for storage. For a single-probe configuration, data acquisition stops after one rotation, and the probe is moved to the next measurement point, such as a small-diameter area, before restarting the turntable and probe for data acquisition. For a multi-probe configuration, height data can be collected simultaneously from multiple diameters, significantly improving measurement efficiency and reducing measurement time.

[0057] Data processing software

[0058] The core of the data processing software is to establish a mathematical relationship between height data changes and tilt and eccentricity, and then use the least squares method to allocate the weight of tilt and eccentricity. The relationship between height data changes and tilt is as follows: the maximum and minimum distances measured at aperture A are HA_MAX and HA_MIN, respectively, meaning the amplitude measured at aperture A is ZA = HA_MAX - HA_MIN. Similarly, the maximum and minimum distances measured at aperture B are HB_MAX and HB_MIN, respectively, meaning the amplitude measured at aperture B is ZB = HB_MAX - HB_MIN. The functional relationship between amplitude and tilt angle α is: 2 × Ф × tan(α), where Ф is half the aperture size. The functional relationship between amplitude and eccentricity Δ is: (2 × k × Δ), where k is the mirror slope corresponding to aperture Ф. By collecting data, the amplitudes corresponding to the heights at two different apertures are obtained. Then, the least squares method is used to allocate the weight of tilt and eccentricity to obtain the optimal tilt and eccentricity.

[0059] Taking a 60mm diameter germanium plano-convex lens as an example, the specific implementation process of this invention is described in detail. The germanium plano-convex lens to be tested is placed on an air-bearing turntable, and its position and orientation are adjusted according to the previously described method to ensure that the center of the lens coincides with the rotation center of the turntable. Simultaneously, the parallelism of the air-bearing platform's plane reference is adjusted to near zero. The air-bearing turntable is started, allowing it to rotate one full revolution at a set speed. Simultaneously, the non-contact probe is activated to begin data acquisition. During one revolution of the turntable, the probe continuously collects height data of the lens surface at two different aperture locations.

[0060] The collected height data is imported into measurement and data processing software for processing. The tilt and eccentricity of the germanium plano-convex lens under test at both the large and small apertures are calculated.

[0061] Through the comprehensive and detailed implementation methods described above, this invention successfully achieves accurate measurement and separation of optical mirror tilt and eccentricity errors. This method boasts significant advantages such as large measurement aperture, high precision, and high efficiency, and has broad application prospects in optical processing, inspection, and assembly. In practical applications, the system can be flexibly configured and optimized according to different measurement needs and the characteristics of optical lenses to further improve measurement accuracy and efficiency, providing strong support for the development of optical technology.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for separating tilt and decentration errors of an optical mirror, characterized in that, The method comprises the following steps: The height data of the lens during one rotation is measured at two different preset diameters of the lens to be measured by using a non-contact probe based on the confocal ranging principle; The mathematical relationship between the height data and the tilt and decentration is established by fitting the measured height data using the least square method; The tilt and decentration of the lens to be measured are calculated according to the established mathematical relationship, and the tilt and decentration errors are accurately measured and separated.

2. An optical mirror decentration error measurement and separation system, comprising: The system comprises: An air bearing turntable (1) for carrying and rotating the lens to be measured to ensure stability and accuracy during rotation; A non-contact probe and its related mounting equipment, at least one set of non-contact probes can be mounted and measured at different preset diameters of the lens to be measured; A measurement and data processing software for controlling the probe to collect data, processing and displaying the measurement results, and obtaining the relationship between the height change of the lens and the tilt and decentration by fitting using the least square method, and calculating the tilt and decentration.

3. The optical surface decentration error measurement and separation system of claim 2, wherein, When measuring, the non-contact probe rotates the lens to be measured at least one rotation at two different preset diameters to collect height data during rotation for subsequent data processing and analysis.

4. The testing system for measuring and separating the decentration and tilt errors of an optical surface according to claim 2 or 3, wherein, The measurement and data processing software further comprises: A data processing module for receiving and processing the height data collected by the non-contact probe, and obtaining the relationship between the height change of the lens and the tilt and decentration by fitting using the least square method; A result output and display module for outputting the calculated tilt and decentration in numerical form and displaying it in real time on the detection software interface.

5. The optical surface decentration and tilt error measurement and separation system of claim 4, wherein, When processing data, the measurement and data processing software needs to use at least one set of height data collected by the non-contact probe at two different preset diameters for one measurement surface to establish an accurate tilt and decentration calculation model.

6. The testing system of claim 2, wherein The system is suitable for tilt and decentration detection of various aspheric lenses, can significantly improve the detection accuracy and adjustment efficiency, and has a large measurement diameter, avoiding the problem of mutual conversion of tilt and decentration caused by the diameter limitation of traditional methods.

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