A high-precision vortex optical interferometry displacement sensor for confined space

Abstract

The present invention discloses a high-precision vortex optical interference displacement sensor for use in confined spaces, including an edge-emitting laser chip, a micro-nano spiral phase plate, a Dove prism, a reflector, a cover plate, a photodetector, a packaging substrate, etc., and adopts an optomechanical integrated structure design. There are micro-nano spiral phase plates at both ends of the emitting laser chip. The left laser becomes a vortex beam after passing through the micro-nano spiral phase plate, and the right laser becomes a vortex beam conjugated with the left laser after passing through the micro-nano spiral phase plate and the Dove prism. The conjugated vortex beams on the left and right sides are incident on the grating after passing through the reflector and the lens. After the grating is diffracted, the diffracted beams of the conjugated vortex beams on the left and right sides converge and become coherent, and the vortex interference light field is received by the photodetector, and then the grating displacement is parsed from the coherent light field. The present invention realizes the miniaturization of the vortex optical interference displacement sensor, which is suitable for high-precision displacement measurement in confined space scenes in the fields of precision motion modules, precision instruments, etc.

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 interferometry 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] During the assembly of optical components of the grating readhead, it is necessary to simultaneously meet the challenges of high precision requirements and optical path alignment. In order to ensure the stability of the optical path and the measurement accuracy, the assembly of optical components needs to be extremely precise. The assembly process of the readhead requires that the relative positions and angles between optical components such as light sources, reflectors, wave plates, lenses, and prisms maintain precise geometric relationships, which requires precise adjustment and calibration. As the number of optical components in the readhead increases, the complexity and difficulty of assembly also increase significantly.

[0004] The patent applicant proposed a vortex beam-excited precision grating displacement measurement device and measurement method in the invention patent ZL202210494629.0, which has been authorized. This method improves the resolution and accuracy of precision grating measurement in principle. However, the measurement device described in the patent also faces problems such as a large number of optical components in the reading head, 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 design and manufacture of the many 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 interferometry displacement sensor for use in confined spaces. The optomechanical and electrical 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 plate, a photodetector, a packaging substrate, etc., and the optomechanical and electrical integrated structure is manufactured by utilizing 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, so that the sensor is 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 comprises a packaging substrate and a cover plate. A working cavity is processed inside the packaging substrate, a laser emitting chip and a dove prism are installed at the bottom of the working cavity, a second micro-nano spiral phase plate is fixedly installed at the right end of the laser emitting chip, the dove prism is located on the right side of the second micro-nano spiral phase plate, a first micro-nano spiral phase plate is fixedly installed at the left end of the laser emitting chip, a first reflecting surface and a second reflecting surface are respectively arranged on the inclined surface of the working cavity, a first lens and a second lens are opened 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 reflection surface and the second reflection surface are highly reflective aluminum films or gold films, and the first reflection surface and the second reflection surface are processed on the inclined surface of the working cavity by a coating process; the film thickness is 100-1000 nm.

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

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

[0013] A working method of a high-precision vortex optical interferometry displacement sensor applied to a confined space 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 emission chip passes through the first micro-nano spiral phase plate and becomes a vortex beam incident on the first reflection 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 reflection surface.

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

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

[0018] S5. When the object to be measured moves, the grating moves accordingly, and the symmetrical order diffracted light undergoes 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;

[0019] S6. The photoelectric detector 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, and its grating pitch is 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 achieved, thus solving the problem of high-precision displacement measurement in confined space. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0024] Figure 2 FIG. 4 is a 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 for use in confined spaces comprises a packaging substrate 11 and a cover plate 12. A working cavity is machined inside the packaging substrate 11 by MEMS technology. Specifically, the bottom of the working cavity is first machined by 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 the 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, and the Dove prism 4 makes the light beam conjugate. The Dove prism 4 is located on the right side of the second micro-nano spiral phase plate 3. The first micro-nano spiral phase plate 2 is fixedly installed on the left end of the laser emitting chip 1.

[0028] The second micro-nano spiral phase plate 3 is fixedly installed at the right end of the laser emission chip 1. The two micro-nano spiral phase plates are used to generate vortex beams. The first reflection surface 6 and the second reflection surface 5 are respectively arranged on the inclined surface of the working cavity. The first reflection surface 6 and the second reflection surface 5 are processed on the inclined surface of the working cavity through a coating process. The cover plate 12 is provided with a first lens 7 and a second lens 8. The photodetector 10 is fixedly installed between the first lens 7 and the second lens 8. The first reflection surface 6 and the second reflection surface 5 are used to reflect the light beam, so that the reflected light beam is incident on the first lens 7 and the second lens 8 respectively. The first lens 7 and the second lens 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 middle position 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 film 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 450-950 nm.

[0032] The topological charge number of the vortex light 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 mounted on the object to be measured;

[0035] S2. The laser on the left side of the laser emission chip 1 passes through the first micro-nano spiral phase plate 2 and becomes 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 and 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.

[0036] 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;

[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 frequency shifts and generates 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 conjugate vortex diffraction light coherence image and analyzes it to obtain the displacement of the object to be measured.

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

[0041] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A working method of a high-precision vortex optical interferometer displacement sensor for use in a confined space, the high-precision vortex optical interferometer displacement sensor for use in a confined space comprising a packaging substrate (11) and a cover plate (12), the packaging substrate (11) being processed with a working cavity inside, a laser emission chip (1) and a Dove prism (4) being mounted at the bottom of the working cavity, a second micro-nano spiral phase plate (3) being fixedly mounted at the right end of the laser emission chip (1), the Dove prism (4) being located on the right side of the second micro-nano spiral phase plate (3), a first micro-nano spiral phase plate (2) being fixedly mounted at the left end of the laser emission chip (1), a first reflection surface (6) and a second reflection surface (5) being respectively arranged on the inclined surface of the working cavity, a first lens (7) and a second lens (8) being provided on the cover plate (12), and a photodetector (10) being fixedly mounted between the first lens (7) and the second lens (8); It is characterized in that The steps include: S1. The grating (9) is mounted on the object to be measured; S2. The left laser 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 right laser 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 left laser, and then is incident on the second reflection surface (5); S3. The first reflection surface (6) and the second reflection surface (5) are used to reflect the light beam, so that the reflected light beam is incident on the first lens (7) and the second lens (8) respectively, and the left and right vortex light beams are respectively refracted by the first lens (7) and the second lens (8) and then incident on the grating (9), and after being diffracted by the grating (9), the two vortex diffracted light beams converge 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 frequency shift and generates 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 conjugate vortex diffraction light coherence image and analyzes it to obtain the displacement of the object to be measured.

2. The working method 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 working method according to claim 1, characterized in that: The first reflection surface (6) and the second reflection surface (5) are highly reflective aluminum films or gold films. The first reflection surface (6) and the second reflection surface (5) are processed on the inclined surface of the working cavity by a coating process, and the film thickness is 100-1000 nm.

4. The working method according to claim 1, characterized in that: The laser emission chip (1) is an edge-emitting laser chip, and the wavelength of the emitted laser is 450-950 nm.

5. The working method according to claim 1, characterized in that: The topological charge number of the vortex light beams generated by the first micro-nano spiral phase plate (2) and the second micro-nano spiral phase plate (3) is 1-8.

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