High-precision vortex grating interference displacement sensor and working method thereof

Abstract

The invention discloses a high-precision vortex grating interference displacement sensor and a working method thereof, the high-precision vortex grating interference displacement sensor comprises an edge emission laser chip, a micro-nano spiral phase plate, a Dove prism, a reflector, a cover plate, a photoelectric detector, a packaging substrate and the like, and the high-precision vortex grating interference displacement sensor is designed by adopting an optical-mechanical-electrical integrated structure. Micro-nano spiral phase plates are arranged at the two ends of the laser emitting chip, left-side laser becomes a vortex light beam after passing through the micro-nano spiral phase plates, right-side laser becomes a vortex light beam conjugated with the left-side laser after passing through the micro-nano spiral phase plates and Dove prisms, and the conjugated vortex light beams on the left side and the right side enter a grating after passing through a reflector and a lens. After grating diffraction, diffraction beams of the conjugate vortex beams on the left side and the right side are converged and coherent, a vortex interference light field is received by a photoelectric detector, and then grating displacement is analyzed from a coherent light field. Miniaturization of the vortex light interference displacement sensor is achieved, and the vortex light interference displacement sensor is suitable for high-precision displacement measurement in limited space scenes in the fields of precision motion modules, precision instruments and the like.

Description

Technical Field

[0001] The present invention relates to the field of intelligent sensing technology for high-end equipment, and in particular to a high-precision vortex optical interferometer displacement sensor for use in confined spaces. Background Art

[0002] Precision grating interferometry technology, due to its high resolution and stability, can achieve sub-micron and even nanometer precision displacement measurement. It is one of the main supporting technologies for quality control and performance optimization in semiconductor manufacturing, precision machine tools, aerospace and other fields.

[0003] The assembly of optical components in a grating readhead requires both high precision and the challenge of optical alignment. To ensure optical path stability and measurement accuracy, the assembly of optical components requires extremely high precision. The readhead assembly process requires precise geometric relationships between the relative positions and angles of optical components, such as the light source, reflectors, wave plates, lenses, and prisms, requiring precise adjustment and calibration. As the number of optical components in the readhead increases, the complexity and difficulty of assembly increase significantly.

[0004] The patent applicant proposed a vortex beam-excited precision grating displacement measurement device and method in invention patent ZL202210494629.0, which has been granted. This method fundamentally improves the resolution and accuracy of precision grating measurements. However, the measurement device described in this patent also faces issues such as the large number of optical components in the readhead, difficulty in assembly, and large device size.

[0005] In addition, with the demand for high-precision displacement measurement in confined space scenarios in high-end equipment precision motion modules, precision instruments and other fields, traditional large-volume grating readheads are difficult to install and integrate. There is an urgent need to integrate the numerous optical components in the readhead to achieve miniaturization of the grating readhead to adapt to high-precision displacement measurement in confined and narrow spaces. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention discloses a high-precision vortex optical interferometer displacement sensor for use in confined spaces. The optomechanical integrated structure is designed by integrating an edge-emitting laser chip (EEL), a micro-nano spiral phase plate, a Dove prism, a reflector, an integrated dual-lens cover, a photodetector, a packaging substrate, etc., and the optomechanical integrated structure is manufactured using coating and micro-nano etching processes. This greatly reduces the difficulty of assembling the optical elements of the reading head and realizes the miniaturization of the reading head, making it suitable for high-precision displacement measurement in confined and narrow spaces.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A high-precision vortex optical interferometer displacement sensor for use in confined spaces adopts an optomechanical integrated structure design and includes a packaging substrate and a cover plate. A working cavity is processed inside the packaging substrate, and a laser emitting chip and a Dove prism are installed at the bottom of the working cavity. The Dove prism is located on the right side of the laser emitting chip. A first micro-nano spiral phase plate is fixedly installed at the left end of the laser emitting chip, and a second micro-nano spiral phase plate is fixedly installed at the right end of the laser emitting chip. A first reflecting surface and a second reflecting surface are respectively provided on the inclined surface of the working cavity. A first lens and a second lens are provided on the cover plate, and a photodetector is fixedly installed between the first lens and the second lens.

[0009] Preferably, the first lens and the second lens are convex lenses, and the two lenses are coplanar.

[0010] Preferably, the first reflective surface and the second reflective surface are highly reflective aluminum films or gold films, which are processed on the inclined surface of the working cavity by a coating process; the film thickness is 100-1000nm.

[0011] Preferably, the laser emitting chip is an edge-emitting laser chip, and the emitted laser wavelength is 450-950nm.

[0012] Preferably, the topological charge number of the vortex beams generated by the first micro-nano spiral phase plate and the second micro-nano spiral phase plate is 1-8.

[0013] A method for operating a high-precision vortex optical interferometry displacement sensor for use in confined spaces comprises the following steps:

[0014] S1. Install the grating on the object to be measured;

[0015] S2. The laser on the left side of the laser emitting chip passes through the first micro-nano spiral phase plate and becomes a vortex beam incident on the first reflective surface. The laser on the right side is emitted from the second micro-nano spiral phase plate and passes through the Dove prism to become a vortex beam conjugated with the laser on the left side, and then is incident on the second reflective surface.

[0016] S3. The left and right vortex beams are respectively refracted by the first lens and the second lens and incident on the grating. After diffraction by the grating, the two vortex diffracted beams merge and become coherent.

[0017] S4. The coherent light field is received by a photodetector and converted into an image signal.

[0018] S5. When the object to be measured moves, the grating moves with it, causing the symmetrical order diffracted light to undergo a frequency shift, resulting in a phase difference Δφ. The phase difference Δφ caused by the measured displacement x is linearly related to the rotation angle of the coherence pattern of the equal conjugate vortex diffraction light, and the direction of rotation corresponds to the direction of the measured displacement.

[0019] S6. The photodetector receives the coherent image of the conjugate vortex diffraction light and analyzes it to obtain the displacement of the object to be measured.

[0020] Furthermore, the grating is a reflective phase grating with a grating pitch of 0.4-10 μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention further develops the precision grating interferometry technology of vortex light excitation. By integrating the edge-emitting laser chip (EEL), micro-nano spiral phase plate, Dove prism, reflector, integrated dual-lens cover, photodetector, packaging substrate, etc. into an optomechanical and electrical integrated structure design, the difficulty of assembling the optical elements of the sensor is greatly reduced, and the miniaturization of the vortex light interferometry sensor is realized, thus solving the problem of high-precision displacement measurement in confined space. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of light path propagation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0026] Reference Figure 1 : A high-precision vortex optical interferometer displacement sensor used in confined spaces includes a packaging substrate 11 and a cover plate 12. A working cavity is processed inside the packaging substrate 11 through a MEMS process. Specifically, the bottom of the working cavity is first processed through two photolithography processes, and then ion beam etching is used to obtain a cavity slope with high inclination accuracy. Finally, an electron beam polishing process is used to precisely polish the cavity bottom and slope to prepare for the subsequent installation of related components and coating of the reflective surface.

[0027] A laser emitting chip 1 and a Dove prism 4 are installed at the bottom of the working cavity. The laser emitting chip 1 and the Dove prism 4 are glued to the bottom of the working cavity. The laser emitting chip 1 is used to emit laser light, and the Dove prism 4 makes the light beam conjugate. The Dove prism 4 is located on the right side of the laser emitting chip 1. The first micro-nano spiral phase plate 2 is fixedly installed on the left end of the laser emitting chip 1.

[0028] A second micro-nano spiral phase plate 3 is fixedly mounted on the right end of the laser emission chip 1. These two micro-nano spiral phase plates are used to generate vortex beams. A first reflective surface 6 and a second reflective surface 5 are respectively provided on the inclined surface of the working cavity. These first and second reflective surfaces 6 and 5 are machined onto the inclined surface of the working cavity through a coating process. A first lens 7 and a second lens 8 are provided on the cover plate 12. A photodetector 10 is fixedly mounted between the first and second lenses 7 and 8. The first and second reflective surfaces 6 and 5 are used to reflect the light beam, causing it to be incident on the first and second lenses 7 and 8, respectively. The first and second lenses 7 and 8 are used to change the transmission direction of the light beam so that it is incident on the grating 9 at a specific angle. The photodetector 10 is used to receive the coherent light field and is glued to the center of the cover plate 12.

[0029] The first lens 7 and the second lens 8 are convex lenses, and the two lenses are coplanar. The cover plate 12 is made of quartz.

[0030] The first reflecting surface 6 and the second reflecting surface 5 are highly reflective aluminum films or gold films with a thickness of 100-1000 nm.

[0031] The laser emitting chip 1 is an edge emitting laser chip (EEL), and the wavelength of the emitted laser is 450-950nm.

[0032] The topological charge number of the vortex beams generated by the first micro-nano spiral phase plate 2 and the second micro-nano spiral phase plate 3 is 1-8.

[0033] Reference Figure 2 :A working method of a high-precision vortex optical interferometry displacement sensor applied to a confined space, comprising the following steps:

[0034] S1. The grating 9 is installed on the object to be measured;

[0035] S2. The laser beam on the left side of the laser emitting chip 1 passes through the first micro-nano spiral phase plate 2 and becomes a vortex beam incident on the first reflective surface 6. The laser beam on the right side, after being emitted from the second micro-nano spiral phase plate 3, passes through the Dove prism 4 and becomes a vortex beam conjugated with the laser beam on the left side, and then is incident on the second reflective surface 5.

[0036] S3. The left and right vortex beams are respectively refracted by the first lens 7 and the second lens 8 and incident on the grating 9. After diffraction by the grating 9, the two vortex diffracted beams merge and become coherent.

[0037] S4. The coherent light field is received by the photodetector 10 and converted into an image signal;

[0038] S5. When the object to be measured moves, the grating 9 moves accordingly, and the symmetrical order diffracted light undergoes a frequency shift, thereby generating a phase difference Δφ. The phase difference Δφ caused by the measured displacement x is linearly related to the rotation angle of the equal conjugate vortex diffraction light coherence pattern, and the rotation direction corresponds to the measured displacement direction;

[0039] S6. The photoelectric detector 10 receives the coherent image of the conjugate vortex diffraction light and analyzes it to obtain the displacement of the object to be measured.

[0040] Furthermore, the grating is a reflective phase grating with a grating pitch of 0.4-10 μm.

[0041] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should be considered within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A high-precision vortex optical interferometry displacement sensor for use in confined spaces, characterized in that: The invention comprises a packaging substrate (11) and a cover plate (12); a working cavity is processed inside the packaging substrate (11); a laser emitting chip (1) and a Dove prism (4) are installed at the bottom of the working cavity; the Dove prism (4) is located on the right side of the laser emitting chip (1); a first micro-nano spiral phase plate (2) is fixedly installed at the left end of the laser emitting chip (1); a second micro-nano spiral phase plate (3) is fixedly installed at the right end of the laser emitting chip (1); a first reflecting surface (6) and a second reflecting surface (5) are respectively provided on the inclined surface of the working cavity; a first lens (7) and a second lens (8) are provided on the cover plate (12); and a photodetector (10) is fixedly installed between the first lens (7) and the second lens (8).

2. A high-precision vortex optical interferometry displacement sensor for use in confined spaces according to claim 1, characterized in that: The first lens (7) and the second lens (8) are convex lenses, and the two lenses are coplanar.

3. The high-precision vortex optical interferometry displacement sensor for use in confined spaces according to claim 1, characterized in that: The first reflecting surface (6) and the second reflecting surface (5) are highly reflective aluminum films or gold films, and are processed on the inclined surface of the working cavity through a coating process, with a film thickness of 100-1000 nm.

4. A high-precision vortex optical interferometry displacement sensor for use in confined spaces according to claim 1, characterized in that: The laser emitting chip (1) is an edge-emitting laser chip, and the wavelength of the emitted laser is 450-950 nm.

5. The high-precision vortex optical interferometry displacement sensor for use in confined spaces according to claim 1, characterized in that: The topological charge number of the vortex beam generated by the first micro-nano spiral phase plate (2) and the second micro-nano spiral phase plate (3) is 1-8.

6. A method for operating a high-precision vortex optical interferometry displacement sensor for use in a confined space according to any one of claims 1 to 5, characterized in that: The steps include: S1. The grating (9) is mounted on the object to be measured; S2. The laser on the left side of the laser emission chip (1) passes through the first micro-nano spiral phase plate (2) to become a vortex beam incident on the first reflection surface (6). The laser on the right side is emitted from the second micro-nano spiral phase plate (3), passes through the Dove prism (4) to become a vortex beam conjugated with the laser on the left side, and then is incident on the second reflection surface (5); S3. The left and right vortex beams are respectively refracted by the first lens (7) and the second lens (8) and then incident on the grating (9). After diffraction by the grating (9), the two vortex diffracted beams merge and become coherent. S4. The coherent light field is received by the photodetector (10) and converted into an image signal; S5. When the object to be measured moves, the grating (9) moves accordingly, and the symmetrical order diffracted light undergoes a frequency shift, thereby generating a phase difference Δφ. The phase difference Δφ caused by the measured displacement x is linearly related to the rotation angle of the coherent pattern of the equal conjugate vortex diffraction light, and the rotation direction corresponds to the measured displacement direction; S6. The photoelectric detector (10) receives the coherent image of the conjugate vortex diffraction light and analyzes it to obtain the displacement of the object to be measured.

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