Heterodyne laser interferometer based on integrated secondary beam splitter

Abstract

The heterodyne laser interferometer based on the integrated secondary beam splitting component belongs to the field of laser application technology; the invention inputs two spatially separated beams with different frequencies to the heterodyne laser interferometer based on the integrated secondary beam splitting component, wherein the integrated two The sub-beam splitting assembly includes two beam-splitting surfaces perpendicular to each other in space, the two beam-splitting surfaces are coated with polarizing or non-polarizing beam-splitting film, and the travel path lengths of the measuring beam and the reference beam in the integrated secondary beam-splitting assembly are equal. The heterodyne laser interferometer described in the present invention significantly reduces the periodic nonlinear error. Compared with other existing space-separated heterodyne laser interferometers, it also has the advantages of simple structure, good thermal stability, large tolerance angle and easy integration and assembly. Advantages, it meets the high-precision and high-resolution requirements of high-end equipment for laser interferometry.

Description

technical field [0001] The invention belongs to the technical field of laser applications, and mainly relates to a heterodyne laser interferometer based on an integrated secondary light splitting component. Background technique [0002] Heterodyne laser interferometers are widely used in high-end equipment such as ultra-precision CNC machine tools, photolithography machines, and three-coordinate measuring machines because of their strong anti-interference ability, high signal-to-noise ratio, and high precision. With the continuous development of high-end equipment engineering, the existing equipment puts forward higher and higher requirements for the measurement accuracy and resolution of heterodyne laser interferometry. [0003] In heterodyne laser interferometry, nanoscale periodic nonlinear errors seriously limit the further improvement of measurement accuracy and resolution. Researches at home and abroad have shown that periodic nonlinear errors originate from optical a...

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Problems solved by technology

[0003] In heterodyne laser interferometry, nanoscale periodic nonlinear errors severely limit the further improvement of measurement accuracy and resolution

Researches at home and abroad have shown that periodic nonlinear errors originate from optical aliasing in the interference optical path, and traditional heterodyne laser interferometers cannot avoid optical aliasing. Therefore, scholars from various countries have changed their research ideas and proposed a heterodyne laser interferometry based on spatially separated optical paths. Technology, which reduces or eliminates optical aliasing by spatially separated beam delivery to reduce or even eliminate periodic nonlinear errors

[0004] Based on the design concept of spatially separated optical paths, domestic and foreign scholars have successively developed different types of heterodyne laser interferometers, whose periodic nonlinear errors are significantly reduced, but there are certain limitations.

[0005] The heterodyne laser interferometer (Michelson Interferometry with 10pm Accuracy. Rev. Sci. Instrum., 2000, 71(7): 2669-2676) developed by foreign scholars such as John Lawall is complex and complicated in composition, and the measuring beam is only reflected by the target plane Reflecting the mirror once will make the interference signal contrast easily affected by the angular swing of the target plane mirror, that is, the tolerance angle is small, and the optical path imbalance between the measuring beam and the reference beam causes the thermal stability of the heterodyne laser interferometer to be relatively poor. Poor and therefore not widely available

[0006] The heterodyne laser interferometer (Heterodyne Interferometer with Subatomic Periodic Nonlinearity.Appl.Opt., 1999,38(19):4089-4094) designed by Wu Chien-ming, a scholar in Taiwan, China, is extremely complex in composition, difficult to integrate and assemble, and the measurement beam It is only reflected once by the target plane mirror so that the contrast of the interference signal is easily affected by the angular swing of the target plane mirror, that is, the tolerance angle is small, and there is also the problem of poor thermal stability caused by the unbalanced optical path

[0007] Although the heterodyne laser interferometer (A Heterodyne Interferometer with Periodic Nonlinearities Smaller than ± 10pm. Meas. Sci. Technol., 2012, 23 (9): 094005-094011) designed by German scholar Christoph Weichert has good thermal stability, but Its structure is complex, component customization and integrated assembly are difficult, and the measurement beam is only reflected once by the target plane mirror, which makes the interference signal contrast easily affected by the angular swing of the target plane mirror, that is, the tolerance angle is small, and it is not easy promotional use

[0008] Another foreign scholar, Steven R. Gillmer, developed a heterodyne laser interferometer (Development of a Novel Fiber-Coupled Three Degree-of-Freedom Displacement Interferometer. University of Rochester Master Thesis, 2013), although the structure is simple and symmetrical and has good thermal stability. However, the measurement beam is only reflected once by the target plane mirror, which also makes the interference signal contrast easily affected by the angular swing of the target plane mirror, that is, the tolerance angle is small, so it is not easy to popularize and use

[0009] In addition, Korean scholar Ki-Nam Joo et al. developed a new space-separated heterodyne laser interferometer in the patent WO2010030179A1, but the heterodyne laser interferometer only has thermal The characteristics of good stability and large tolerance angle; Jonathan D.Ellis later changed the target corner cube prism into a target plane reflector (Fiber-coupled displacement interferometry without periodic nonlinearity. Optics Letters, 2011, 36(18): 3584-3586 .), but its complex structure and unbalanced optical paths of measuring light and reference light lead to poor thermal stability, and it is not easy to popularize and use

Hu Pengcheng of Harbin Institute of Technology and others proposed an improvement (Highly stable heterodyne interferometer without periodic nonlinearity. Technisches Messen: Sensoren, Gerate, Systeme, 2014.) to balance the total optical path of the measurement light output and the reference beam in multiple beam-splitting prisms. The thermal stability is improved, but the structure of the improved heterodyne laser interferometer is more complicated, the integration and assembly are more difficult, and it is not easy to promote

[0010] In summary, the existing space-separated heterodyne laser interferometers are difficult to meet the requirements of good thermal stability and large tolerance angle at the same time, which seriously limits the improvement of the measurement capability of heterodyne laser interferometers.

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