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CN-121994166-A - Aspherical interferometry system based on spatial light modulator

CN121994166ACN 121994166 ACN121994166 ACN 121994166ACN-121994166-A

Abstract

The invention discloses an aspheric surface interferometry system based on a spatial light modulator. The invention comprises a laser light source, a filtering beam expanding collimation module, a core interference light path, a 4f relay imaging module and an image sensor, wherein the filtering beam expanding collimation module is used for generating high-quality collimated parallel light beams, the core interference light path is used for dividing incident light beams into a reference light path and a measuring light path and carrying out programmable wave front phase modulation on the measuring light beams, and the 4f relay imaging module is used for transmitting interference patterns to a detection plane without distortion. The invention realizes the rapid adaptation measurement of different aspheric surface shapes through the flexible wavefront modulation capability of the spatial light modulator without replacing the traditional physical compensator, has the advantages of high measurement precision, strong universality and low cost, is suitable for the surface shape detection of various spherical and aspheric optical elements, and solves the problems of poor system universality and low measurement efficiency caused by relying on a special compensator in the prior art.

Inventors

  • SHI YAN
  • HU YINGYING
  • YIN LIN
  • CHEN YI
  • ZHAN CHUNLIAN
  • YE YUXUAN

Assignees

  • 中国计量大学

Dates

Publication Date
20260508
Application Date
20260410

Claims (7)

  1. 1. The aspheric surface interferometry system based on the spatial light modulator is characterized by comprising a laser light source (1), a filtering beam expanding collimation module, a core interference light path, a 4f relay imaging module and an image sensor (12); the laser light source (1) is used for emitting laser; The filtering beam expanding collimation module comprises a light filter (2), a micro objective lens (3), a spatial filtering pinhole (4) and a collimation objective lens (5) which are sequentially arranged along a light path, wherein light emitted by a laser light source (1) sequentially passes through the light filter (2) and the micro objective lens (3), the micro objective lens (3) converges light beams at the spatial filtering pinhole (4) at a focal plane of the micro objective lens, and the light beams passing through the spatial filtering pinhole (4) are collimated into parallel light by the collimation objective lens (5) and enter a core interference light path; The core interference light path comprises a first light splitting cube (6), a second light splitting cube (7), a third light splitting cube (8), a fourth light splitting cube (9), a plane reflecting mirror (13), a spatial light modulator (14) and a measured aspheric mirror (15) which are arranged along the light path, wherein parallel light emitted from the collimating objective lens (5) is split into two beams by the second light splitting cube (7) after passing through the first light splitting cube (6), one beam is reference light and is transmitted to the plane reflecting mirror (13) through the second light splitting cube (7), is reflected back by the plane reflecting mirror (13) in an original way, is reflected to the first light splitting cube (6) after passing through the second light splitting cube (7) again, is finally transmitted through the fourth light splitting cube (9), is used as measuring light, is transmitted to the other beam, is transmitted to the third light splitting cube (7), is transmitted to the spatial light modulating cube (14) and then passes through the spatial light modulating cube (15) and is transmitted to the measured aspheric mirror (8) after passing through the second light splitting cube (7) in an original path, and reflected at this cube to the fourth light splitting cube (9), and finally at the fourth light splitting cube (9); The 4f relay imaging module comprises a first relay lens (10) and a second relay lens (11) which are sequentially arranged along a light path, reference light and measuring light emitted from the fourth light splitting cube (9) are combined into one path, and sequentially pass through the first relay lens (10) and the second relay lens (11) to be finally converged on the target surface of the image sensor (12).
  2. 2. The spatial light modulator-based aspheric interferometry system of claim 1, wherein the spatial filtering pinhole (4) in the filtering, beam expanding and collimating module is located at an image-side focal plane of the microscope objective (3) and at an object-side focal plane of the collimating objective (5).
  3. 3. The system of claim 1, wherein the spatial light modulator (14) is a reflective phase liquid crystal spatial light modulator with a pixel array programmable loaded with an aspheric compensating phase profile.
  4. 4. The spatial light modulator-based aspheric interferometry system of claim 1, wherein the 4f relay imaging module comprises a first relay lens (10) and a second relay lens (11) with different focal lengths, the distance between the two lenses is the sum of the focal lengths of the two lenses to form a beam shrinking light path, and the size of the interference light beam is reduced proportionally to match the target surface of the image sensor (12).
  5. 5. The spatial light modulator-based aspheric interferometry system of claim 1 wherein the aspheric mirror (15) under test is mounted on a multi-dimensional adjustment frame for adjusting its position and attitude to achieve precise alignment and focusing of the light beam.
  6. 6. The spatial light modulator-based aspheric interferometry system of claim 1, wherein the planar mirror (13) is mounted on a precision displacement stage that changes the optical path length of the reference optical path by adjusting the precision displacement stage.
  7. 7. The spatial light modulator-based aspheric interferometry system of claim 4, wherein a front focal plane of a first relay lens (10) of the 4f relay imaging module coincides with a beam combining plane of the fourth light splitting cube (9), and a back focal plane of a second relay lens (11) coincides with a target plane of the image sensor (12).

Description

Aspherical interferometry system based on spatial light modulator Technical Field The invention relates to the technical field of optical measurement, in particular to an aspheric surface interferometry system based on a spatial light modulator. Background The aspheric optical element has become a core element of a modern high-end optical system due to unique advantages of correcting aberration, simplifying system structure, reducing weight, improving imaging performance and the like, and is widely applied to the fields of space remote sensing, photoetching equipment, astronomical observation, high-end imaging and the like. However, high precision manufacturing is severely dependent on high precision inspection. Precise and efficient detection of aspheric surface shapes has so far remained a key technical bottleneck limiting their development. Currently, the mainstream aspheric surface detection method is mainly divided into two main types of contact measurement and non-contact measurement. Contact measurement, such as a stylus profilometer, can directly acquire surface profile sagittal information, but the point-by-point scanning mode is low in efficiency, and the risk of scratching a precise polished surface exists, so that the requirement of mass production is difficult to meet. Non-contact measurement includes optical scanning methods and interferometry methods, which are inefficient and require prediction of surface shape, interferometry is expected due to its high sensitivity, zero-position high-precision measurement, but it still faces many challenges in practical applications. The following difficulties exist in aspheric interferometry: Traditional compensating interferometry (including zero compensation and partial compensation) relies on specially designed compensating optical elements (e.g., compensators, computational holograms) to convert an aspherical wavefront into an easily measurable spherical or planar wavefront. The method has high precision, but the characteristics of custom pairing of the compensator itself lead to poor universality, long design and processing period and high cost, and the assembly error and the surface shape error of the compensator can be directly introduced into a final measurement result, so that the reliability of measurement is reduced. Furthermore, interferometry, in the face of aspheres with large deviations (high asphericity), faces a core contradiction, dynamic range versus measurement accuracy tradeoff. For elements with high asphericity, the generated wavefront deviation is huge, so that fringes in an interference field are too dense and even exceed the spatial sampling limit of a detector, and the fringes cannot be resolved correctly, namely a fringe aliasing phenomenon occurs. While fringe density can be reduced by reducing sensitivity (e.g., using longer wavelengths), this directly compromises the measurement accuracy of the system. On the premise of not losing the precision, the measurement dynamic range of the interferometer is effectively enlarged, and the method becomes a great challenge for aspheric surface detection. In recent years, interferometric techniques based on spatial light modulators, SPATIAL LIGHT Modulator (SLM), have provided a promising solution to the above-mentioned problems. The spatial light modulator is used as a programmable optical element, and can flexibly modulate the wavefront of light wave in an electrically controlled manner, so that the spatial light modulator can replace a traditional fixed compensator in theory. How to construct an optical system which can fully exert the technical advantages of a spatial light modulator and has high precision, high stability and excellent anti-interference capability becomes an important research direction in the field. Disclosure of Invention Aiming at the defects of the prior art, the invention provides an aspheric surface interferometry system based on a spatial light modulator, which has the advantages of high universality, no need of a traditional compensator and the like, and solves the technical problems. In order to achieve the aim, the invention provides the technical scheme that the aspheric surface interferometry system based on the spatial light modulator comprises a laser light source (1), a filtering beam expanding collimation module, a core interference light path, a 4f relay imaging module and an image sensor (12); the laser light source (1) is used for emitting laser; The filtering beam expanding collimation module comprises a light filter (2), a micro objective lens (3), a spatial filtering pinhole (4) and a collimation objective lens (5) which are sequentially arranged along a light path, wherein light emitted by a laser light source (1) sequentially passes through the light filter (2) and the micro objective lens (3), the micro objective lens (3) converges light beams at the spatial filtering pinhole (4) at a focal plane of the micro objective lens, and the light bea