An interference generation module and an integrated laser interferometer

Abstract

The application belongs to the technical field of micro-distance measurement, and particularly relates to an interference generation module and an integrated laser interferometer, which specifically comprises a laser generator, a collimating lens and a depolarization light splitting prism arranged along the light propagation direction. The interior of the depolarization light splitting prism has a light splitting surface, and the exterior of the depolarization light splitting prism has an incident side, a reflection side, a first emission side and a second emission side in sequence along the circumference. The incident side and the first emission side are oppositely arranged, the reflection side and the second emission side are oppositely arranged, and the plane where the incident side is located is perpendicular to the plane where the reflection side is located. The collimating lens is attached to and fixedly bonded with the incident side. Through the high integration of the physical space, the internal optimization of the light path and the direct processing of the photoelectric signal, the laser interferometer is successfully converted into a modular measurement assembly with compact structure, stable and reliable performance and convenient use, and the requirements of low cost and high integration are met.

Description

Technical Field

[0001] This application belongs to the field of micro-measurement technology, and more specifically, relates to an interference generation module and an integrated laser interferometer. Background Technology

[0002] High-precision displacement measurement is a key technology for improving process accuracy in modern industry and scientific research. Laser interferometry is widely used in precision machining due to its high precision and non-contact characteristics.

[0003] Displacement measurement using zero-difference interferometry utilizes the interference signal formed by the spatial superposition of a reference beam (generated by a single-beam laser) and a measurement beam to obtain the displacement or angular change of the object under test. However, most laser interferometer systems on the market are large and expensive, making them difficult to apply for micro-displacement measurement in confined spaces. Therefore, developing a miniaturized, low-cost, and highly integrated laser interferometer is an urgent problem to be solved. Utility Model Content

[0004] In response to the deficiencies or improvement needs of existing technologies, this application provides an interference generation module and an integrated laser interferometer, aiming to solve the technical problems of existing laser interferometers being large in size, high in cost, and unable to perform minute displacement measurements in a limited space.

[0005] This application provides an interference generation module, which specifically includes a laser generator, a collimating lens, and a depolarizing beam splitter arranged sequentially along the light propagation direction. The depolarizing beam splitter has a beam splitting surface inside and has an incident side, a reflecting side, a first exiting side and a second exiting side in sequence along the circumference outside. The incident side and the first exiting side are arranged opposite to each other, the reflecting side and the second exiting side are arranged opposite to each other, and the plane of the incident side is perpendicular to the plane of the reflecting side. The collimating lens is attached and fixed to the incident side. The laser emitted from the laser generator is collimated by the collimating lens. The collimated light enters from the incident side and is split into mutually perpendicular reflected light and transmitted light by the beam splitting surface. The reflected light is reflected by the reflection side to form a reference light path emitted from the second exit side. The transmitted light is emitted from the first exit side, reflected by the test object, and then passes through the beam splitting surface again to form a measurement light path emitted from the second exit side. The reference light path and the measurement light path are superimposed to produce interference.

[0006] As a further preferred embodiment, the reflective side is coated with an anti-reflection film, which is configured to cause total internal reflection of normally incident laser light on its surface.

[0007] As a further preferred embodiment, the antireflective film is a dielectric film or a metal film.

[0008] As a further preferred embodiment, the laser generator is a laser diode.

[0009] This application also provides an integrated laser interferometer, which includes a housing, a detection signal processing module, and an interference generation module as described in any of the preceding claims; The outer shell has an internal cavity and an outlet hole communicating with the cavity on one side. The detection signal processing module and the interference generation module are located inside the accommodating cavity; the first emission side is arranged opposite to the emission hole; The detection signal processing module includes a photodetector and a circuit board. The photodetector is attached and bonded to the second emission side. The photodetector is used to convert the interference light signal generated by the reference beam and the measurement beam into an electrical signal. The circuit board is electrically connected to the photodetector and is used to perform waveform processing and data calculation on the electrical signal.

[0010] As a further preferred embodiment, the photodetector is a four-quadrant photodetector.

[0011] As a further preferred embodiment, the outer casing is made of metal and is formed by combining a bottom shell and a cover.

[0012] As a further preferred embodiment, the accommodating cavity includes a cylindrical hole and a square groove, the laser generator is fixed in the cylindrical hole, the depolarizing beam splitter, the photodetector and the circuit board are disposed in the square groove, and the emission port is located on the side of the square groove opposite to the cylindrical hole and communicates with the square groove.

[0013] As a further preferred embodiment, the photodetector and the second emitting side, and the collimating lens and the incident side are all fixed by adhesive, and the adhesive used for bonding is transparent ultraviolet adhesive.

[0014] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages: 1. This interference generation module reduces the size of the optical system by integrating the collimating lens with the incident side of the depolarizing beam splitter. It uses the beam splitter to split the beam into reflected and transmitted light. The reflected light is reflected by the reflecting side to form a reference light path emitted from the second exit side. The transmitted light is emitted from the first exit side, reflected by the object under test, and then passes through the beam splitter again to form a measurement light path emitted from the second exit side. The propagation and synthesis of the reference light path and the measurement light path are cleverly integrated into the same depolarizing beam splitter, reducing the number of parts and saving manufacturing costs and assembly difficulty. Based on this interference module, the miniaturized packaging of the interferometer can be realized, which is suitable for the precise measurement of small displacements in a limited space.

[0015] 2. Depositing an anti-reflection film on the reflective side can reduce the energy loss of the laser when it is reflected at the interface, ensure that the reflected light incident on the reflective side does not pass through the reflective side surface and achieves total internal reflection, ensure that the reference optical path has sufficient light intensity, and improve the intensity and signal-to-noise ratio of the interference signal.

[0016] 3. By highly integrating all optical and electronic components, such as the interference generation module and the detection signal processing module, into a single housing cavity, a complete integrated instrument is formed. This design greatly improves the instrument's structural stability, enhances its resistance to environmental interference, facilitates portability and installation, and achieves the goal of usability within limited spaces.

[0017] 4. By physically isolating the main heat source (laser generator) from the core optical and electronic components through partitioning design, the influence of heat on interference signals can be effectively reduced, the internal layout can be optimized, and the thermal stability and long-term measurement stability of the system can be improved. This is an important design for achieving high precision. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an integrated laser interferometer provided in an embodiment of this application; Figure 2 This is a schematic diagram of the optical path structure of an interference generation module provided in an embodiment of this application; Figure 3 This is a schematic diagram of the disassembled structure of an integrated laser interferometer provided in an embodiment of this application.

[0019] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 11. Outer shell; 11a. Receiving cavity; 11b. Exit hole; 11c. Cylindrical hole; 11d. Square groove; 111. Bottom shell; 112. Shell cover; 12. Detection signal processing module; 121. Photodetector; 122. Circuit board; 13. Interference generation module; 131. Laser generator; 132. Collimating lens; 133. Depolarizing beam splitter; 133a. Beam splitting surface; 133b. Incident side; 133c. Reflection side; 133d. First exit side; 133e. Second exit side; 14. Object under test. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] like Figure 1 and Figure 2As shown, this application embodiment provides an interference generation module 13, which specifically includes a laser generator 131, a collimating lens 132, and a depolarizing beam splitter 133 arranged along the light propagation direction.

[0022] The depolarizing beam splitter 133 has a beam splitting surface 133a inside and an incident side 133b, a reflecting side 133c, a first exiting side 133d, and a second exiting side 133e arranged sequentially along its circumference outside. The incident side 133b and the first exiting side 133d are arranged opposite to each other, the reflecting side 133c and the second exiting side 133e are arranged opposite to each other, and the plane where the incident side 133b is located is perpendicular to the plane where the reflecting side 133c is located.

[0023] The collimating lens 132 is attached and fixed to the incident side 133b. The laser emitted from the laser generator 131 is collimated by the collimating lens 132. The collimated light enters from the incident side 133b and is split into mutually perpendicular reflected light and transmitted light by the beam splitting surface 133a. The reflected light is reflected by the reflecting side 133c to form a reference light path emitted from the second exit side 133e. The transmitted light is emitted from the first exit side 133d, reflected by the test object 14, and then passes through the beam splitting surface 133a again to form a measurement light path emitted from the second exit side 133e. The reference light path and the measurement light path are superimposed to produce interference.

[0024] Based on the above description and knowledge related to the propagation of light, it can be known that one end of the beam splitter 133a is located at the intersection of the incident side 133b and the second exiting side 133e, and the other end is located at the intersection of the first exiting side 133d and the reflecting side 133c. The collimated light incident from the incident side 133b is evenly divided at the beam splitter 133a into reflected light that is directly incident on the reflecting side 133c and transmitted light that directly penetrates the beam splitter 133a and propagates to the first exiting side 133d.

[0025] In terms of structure, the interference generation module 13 integrates the collimating lens 132 with the incident side 133b of the depolarizing beam splitter 133, eliminating the gap between the collimating optics and the depolarizing beam splitter 133 and reducing the size of the optical system. Regarding interference signal generation, the propagation and synthesis of the reference and measurement optical paths are integrated within the same depolarizing beam splitter 133, reducing the number of parts, saving manufacturing costs and assembly difficulty. Based on this interference module 13, miniaturized packaging of the interferometer can be achieved, making it suitable for precise measurement of minute displacements within a limited space.

[0026] The reflective side 133c is coated with an anti-reflection film, which is configured to cause total internal reflection of normally incident laser light on its surface. Coating the anti-reflection film on the reflective side 133c can reduce the energy loss of the laser when it is reflected at the interface, ensure that the reflected light normally incident on the reflective side 133c does not pass through the surface of the reflective side 133c and achieves total internal reflection, ensure that the reference optical path has sufficient light intensity, and improve the intensity and signal-to-noise ratio of the interference signal.

[0027] In the embodiments of this application, the antireflective film is a dielectric film or a metal film. A dielectric film is a transparent optical thin film composed of multiple layers of non-metallic compounds. By controlling the optical thickness and refractive index of different dielectric layers, selective transmission or reflection of light of a specific wavelength can be achieved, resulting in extremely high reflectivity and low loss, thus optimizing performance. However, dielectric films have high production costs. Metal films, on the other hand, are simple to prepare and have lower costs. In practical applications, a balance between performance and cost can be struck depending on the application scenario.

[0028] In a preferred embodiment of this application, the laser generator 131 is a laser diode. By using a laser diode as a light source, its advantages of small size, low power consumption, high efficiency and low cost are utilized to effectively achieve the miniaturization of the module design.

[0029] It is understood that in this application, the power supply of the laser generator 131 can be achieved by an external power supply or by an internal power supply. The power supply can be a rechargeable battery or a power module for processing mains power into usable power, and there is no limitation on this.

[0030] The interference generation module 13 provided in this application embodiment is mainly used to measure the deflection angle or displacement of the object under test 14. Therefore, the object under test 14 needs to be able to reflect light. In practical applications, the object under test 14 can be a reflector or other objects under test coated with a reflective film. In this embodiment, the object under test 14 is used as a reflector for illustration.

[0031] Based on the aforementioned interference generation module 13, this application provides an integrated laser interferometer, which includes a housing 11, a detection signal processing module 12, and the interference generation module 13 as described in any of the preceding claims.

[0032] Among them, combined Figure 3 As shown, the outer shell 11 has a receiving cavity 11a inside and an outlet hole 11b communicating with the receiving cavity 11a on one side of the outer shell 11. The detection signal processing module 12 and the interference generation module 13 are located in the accommodating cavity 11a; the first emission side 133d is arranged opposite to the emission port 11b, and the laser generator 131 is fixed to the collimating lens 132 on the side away from the depolarizing beam splitter 133; the object under test 14 is movably arranged on the side of the emission port 11b away from the depolarizing beam splitter 133; The detection signal processing module 12 includes a photodetector 121 and a circuit board 122. The photodetector 121 is attached and fixed to the second emission side 133e. The photodetector 121 is used to convert the interference light signal generated by the reference beam and the measurement beam into an electrical signal. The circuit board 122 is electrically connected to the photodetector 121 and is used to perform waveform processing and data calculation on the electrical signal.

[0033] In terms of structural design, the integrated laser interferometer 10 fixes all core optical components, such as the laser generator 131, collimating lens 132, depolarizing beam splitter 133, and photodetector 121, within the same accommodating cavity 11a. The photodetector 121 is directly attached and bonded to the second emission side 133e. This design solidifies the complex optical path system into a compact and robust unit, achieving an integrated structure. This avoids the cumbersome assembly and adjustment process of traditional discrete component interferometers, greatly enhancing the instrument's mechanical stability and resistance to environmental interference, and ensuring the repeatability and reliability of long-term measurements.

[0034] In terms of optical path design, the laser generator 131 is fixed to one side of the collimating lens 132, and the beam enters the beam splitter 133 directly after collimation. The first exit side 133d is positioned opposite to the exit hole 11b on the housing 11, ensuring that the measurement optical path can exit unimpeded and reach the object under test 14. The reference optical path is directly received by the photodetector 121 attached to the second exit side 133e after reflection inside the depolarizing beam splitter 133. This compact and precise internal optical path design greatly shortens the optical path and reduces unnecessary reflection interfaces, thereby reducing light energy loss and errors, and facilitating the acquisition of clearer interference signals.

[0035] The photodetector 121 is a four-quadrant photodetector. By using a four-quadrant photodetector, its function is no longer limited to detecting changes in light intensity, but can also accurately sense the positional shift of the light spot. This expands the instrument's measurement capability from one-dimensional displacement to two-dimensional micro-displacement or micro-angle measurement, significantly enhancing the performance indicators and application range of the interferometer.

[0036] Specifically, waveform processing and data calculation of the electrical signal include calculating the displacement or angle change based on the differentially processed electrical signal, the laser wavelength, and the changes in interference fringes. In the field of laser interferometry, calculating displacement and angle changes through changes in laser wavelength and interference fringes is a mature technology.

[0037] To provide a clearer understanding of the structure and function of the interferometer, the operating principle of this embodiment is explained below. This application does not modify the principle and algorithm; the improvements and innovations of this application are mainly reflected in the structure of the interference module and the interferometer.

[0038] Based on the fundamental definition of zero-difference interferometry, zero-difference laser interferometry uses a single-frequency laser as the light source. After beam splitting, the measurement beam illuminates the object under test, and after reflection, it directly interferes with the reference beam. The phase change of the interference signal is linearly related to the displacement of the object under test. By accurately extracting the phase change information and combining it with the known laser wavelength, high-precision measurement can be achieved. It is evident that the integrated laser interferometer of this application employs zero-difference interferometry, and its measurement involves the translational displacement of the mirror under test. and rotational displacement It can be represented as follows: …………………………(1) …………………………(2) in, The distance between two adjacent bright (dark) fringes in the interference pattern is denoted as . For the laser wavelength, This represents the distance the overall position of the interference fringes shifts due to translation. The change in the spacing of the interference fringes is caused by rotation.

[0039] In a preferred embodiment of this application, the outer shell 11 is a metal structure and is formed by combining and encapsulating a bottom shell 111 and a cover 112.

[0040] Preferably, the accommodating cavity 11a includes a cylindrical hole 11c and a square groove 11d, the laser generator 131 is fixed to the cylindrical hole 11c, the depolarizing beam splitter 133, the photodetector 121 and the circuit board 122 are disposed in the square groove 11d, and the emission port 11b is located on the side of the square groove 11d away from the cylindrical hole 11c and communicates with the square groove 11d.

[0041] The partitioned design of the columnar hole 11c and the square groove 11d physically isolates the main heat source (laser generator 131) from the core optical and electronic components, which can effectively reduce the interference of heat and vibration on the measurement optical path, optimize the internal layout, and thus improve the thermal stability and long-term measurement stability of the system.

[0042] In the embodiments of this application, the photodetector 121 and the second emitting side 133e, and the collimating lens 132 and the incident side 133b are preferably bonded together, and the adhesive used for bonding is a transparent ultraviolet adhesive. Using transparent ultraviolet adhesive for bonding simplifies the assembly process and improves production efficiency by utilizing its rapid curing characteristics. At the same time, the adhesive bonding method avoids mechanical stress and further reduces the volume, achieving stress-free, high-precision compact integration, which helps to maintain the long-term stability of the optical path.

[0043] The packaging process of the integrated laser interferometer 10 in this application embodiment can be implemented according to the following steps: Step 1: Preparation of materials, components, and apparatus. Prepare all optical components (collimating lens 132 and depolarizing beam splitter 133), metal parts (casing 11), multi-axis adjustment frame, UV adhesive, etc.

[0044] Step 2: Bonding of optical components; Apply a reflective film to the reflective side 133c of the depolarizing beam splitter 133, and bond the collimating lens 132 and photodetector 121 to the incident side 133b and the second exit side 133e of the depolarizing beam splitter 133 with ultraviolet adhesive. After the ultraviolet adhesive solidifies, a combined optical component is formed.

[0045] Step 3: Gluing and mounting of optical components and housing 11. The combined optical components from Step 2 are glued to the center of the groove 11d above the bottom housing 111 with epoxy resin, and then the circuit board 122 is glued to the center of the groove 11d above the housing cover 112.

[0046] Step 4: Adjustment and installation of laser generator 131. Attach laser generator 131 to the cylindrical hole 11c of housing 11 using epoxy resin. Power on and emit laser light. Use a multi-axis adjustment frame to adjust the attitude and position until the reference light reflected from the reflecting side 133c returns along the original path.

[0047] Step 5: Adjustment and installation of the mirror under test 14. Place the mirror under test 14 outside the interferometer package and perform periodic movements to adjust its attitude so that it returns light along the original optical path and combines with the return light from the reference optical path. Observe the interference signal using the photodetector 121.

[0048] Step Six: Interference Signal Adjustment and Packaging. Adjust the attitude and position of the laser emitter 131 and the mirror under test 14 until the interference contrast is maximized. After the glue has solidified, cover the casing 112 and lock it in place to complete the overall packaging of the interferometer.

[0049] In short, this integrated laser interferometer 10, through high integration of physical space, internal optimization of optical path, and direct processing of photoelectric signals, successfully transforms the laser interferometer into a compact, stable, reliable, and easy-to-use modular measurement component, meeting the requirements of low cost and high integration.

[0050] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0051] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0053] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An interference generation module, characterized in that, It includes a laser generator (131), a collimating lens (132), and a depolarizing beam splitter (133) arranged sequentially along the direction of light propagation. The depolarizing beam splitter (133) has a beam splitting surface (133a) inside and an incident side (133b), a reflecting side (133c), a first exiting side (133d), and a second exiting side (133e) in sequence along the circumferential direction on its outside. The incident side (133b) and the first exiting side (133d) are arranged opposite to each other, the reflecting side (133c) and the second exiting side (133e) are arranged opposite to each other, and the plane of the incident side (133b) is perpendicular to the plane of the reflecting side (133c). The collimating lens (132) is attached and fixed to the incident side (133b). The laser emitted by the laser generator (131) is collimated by the collimating lens (132). The collimated light enters from the incident side (133b) and is split into mutually perpendicular reflected light and transmitted light by the beam splitting surface (133a). The reflected light is reflected by the reflecting side (133c) to form a reference light path emitted from the second exit side (133e). The transmitted light is emitted from the first exit side (133d), reflected by the test object (14), and then passes through the beam splitting surface (133a) again to form a measurement light path emitted from the second exit side (133e). The reference light path and the measurement light path are superimposed to produce interference.

2. The interference generation module according to claim 1, characterized in that, The reflective side (133c) is coated with an anti-reflection film, which is configured to cause total reflection of normally incident laser light on its surface.

3. The interference generation module according to claim 2, characterized in that, The antireflective coating is a dielectric film or a metal film.

4. The interference generation module according to claim 1, characterized in that, The laser generator is a laser diode.

5. An integrated laser interferometer, characterized in that, It includes a housing (11), a detection signal processing module (12), and an interference generation module as described in any one of claims 1 to 4; The outer shell (11) has a receiving cavity (11a) inside and an outlet hole (11b) communicating with the receiving cavity (11a) on one side of the outer shell (11). The detection signal processing module (12) and the interference generation module are located inside the accommodating cavity (11a); the first emission side (133d) is arranged opposite to the emission hole (11b); The detection signal processing module (12) includes a photodetector (121) and a circuit board (122). The photodetector (121) is attached and fixed to the second emission side (133e). The photodetector (121) is used to convert the interference light signal generated by the reference beam and the measurement beam into an electrical signal. The circuit board (122) is electrically connected to the photodetector (121) and is used to perform waveform processing and data calculation on the electrical signal.

6. The integrated laser interferometer according to claim 5, characterized in that, The photodetector (121) is a four-quadrant photodetector.

7. The integrated laser interferometer according to claim 5, characterized in that, The outer shell (11) is made of metal and is formed by combining and encapsulating a bottom shell (111) and a cover (112).

8. The integrated laser interferometer according to claim 5, characterized in that, The accommodating cavity (11a) includes a cylindrical hole (11c) and a square groove (11d). The laser generator (131) is fixed in the cylindrical hole (11c). The depolarizing beam splitter (133), photodetector (121) and circuit board (122) are disposed in the square groove (11d). The emission port (11b) is located on the side of the square groove (11d) away from the cylindrical hole (11c) and communicates with the square groove (11d).

9. The integrated laser interferometer according to claim 5, characterized in that, The photodetector (121) and the second emitting side (133e), and the collimating lens (132) and the incident side (133b) are all fixed by adhesive, and the adhesive used for adhesive is transparent ultraviolet adhesive.

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