Apparatus for measuring thermal expansion coefficient of vacuum optical path based on non-coaxial interference and measuring method thereof

Abstract

This invention discloses a device and method for measuring the coefficient of thermal expansion in a vacuum optical path based on non-coaxial interference, belonging to the field of precision optical measurement technology. The device includes: a laser interferometer encapsulated in a first sealed cavity, used to generate a reference laser beam, a transmitted laser beam, and a reflected laser beam; extracting the phase change caused by the thermal expansion of the sample under test; a beam vacuum transmission unit encapsulated in a second sealed cavity, used to acquire the first and second lateral displacement beams of the thermally controlled regions without and with the sample under test, respectively, and return them parallel to their corresponding laser beam directions to the laser interferometer; a sample temperature control unit for controlling the temperature of the sample under test and recording temperature changes; and a data processing unit for calculating the coefficient of thermal expansion of the sample under test. This invention enables highly stable and sensitive measurements of materials with ultra-low coefficients of thermal expansion.

Description

Technical Field

[0001] This invention belongs to the field of precision optical measurement technology, and particularly relates to a device and method for measuring the thermal expansion coefficient of a vacuum optical path based on non-coaxial interference. Background Technology

[0002] The coefficient of thermal expansion (CTE) is an important physical parameter characterizing the degree to which a material's dimensions change with temperature. It is a key indicator in precision structural design and material performance evaluation, and is widely used in the selection, design, and quality control of highly stable structural materials in fields such as optical systems, precision machinery, semiconductor manufacturing, aerospace, and high-end equipment. With the widespread use of ultra-low CTE materials (such as quartz glass, microcrystalline glass, Invar alloys, advanced ceramics, and ceramic matrix composites) in high-end applications, higher requirements are placed on the measurement accuracy and environmental adaptability of their thermal response behavior. Therefore, a high-precision CTE measurement technology capable of achieving sub-nanometer displacement resolution and applicable to a wide temperature range is urgently needed.

[0003] Existing methods for measuring thermal expansion mainly include the mechanical push rod method and interferometry. Among these, the mechanical push rod method is limited by the measurement principle and transmission mechanism errors, resulting in limited measurement resolution and stability. Furthermore, its measurement uncertainty is insufficient to meet the requirements for ultra-low thermal expansion coefficient materials within 10-1. -8 Testing requirements at the / K level and below. In contrast, interferometry has advantages such as non-contact and high resolution, making it an important technical route for achieving high-precision thermal expansion measurement. However, it still has many limitations in practical engineering applications.

[0004] On the one hand, traditional interferometry requires the end face of the sample to have high reflectivity, necessitating the deposition of a high-reflectivity film on the sample surface. This coating process not only demands high surface quality and flatness but also the thermal expansion characteristics of the film itself may be superimposed on the measurement results, thus interfering with the actual thermal expansion behavior of the sample. On the other hand, interferometric measurement systems are extremely sensitive to environmental conditions; changes in air refractive index with temperature and airflow directly introduce optical path fluctuations, affecting measurement accuracy. To mitigate this effect, the entire interferometric optical path is typically placed in a vacuum environment.

[0005] However, in practical applications, the actual service condition of some materials, especially functional ceramics, composite materials, and high-temperature structural materials, often depends on specific atmospheric conditions (such as inert gas, oxygen, or a controlled atmosphere). If the sample is only placed in a vacuum environment for measurement, it may not accurately reflect the thermal response characteristics of the material under actual working conditions, thus limiting the engineering reference value of the measurement results.

[0006] Furthermore, although dual-frequency heterodyne interferometry offers high displacement resolution and good noise immunity, traditional Michelson and other coaxial interferometric structures commonly suffer from backlight feedback. The returned light can easily interfere with the frequency stability of the laser source, and may even trigger feedback phenomena. To suppress the effects of backlight, the system typically requires the introduction of optical isolators, frequency shifters, or complex optical path structures, which not only increases system complexity but also hinders long-term stable operation and compact integration.

[0007] In summary, while existing thermal expansion interferometry methods have improved measurement accuracy, they still face challenges such as high requirements for sample surface condition, insufficient environmental adaptability, and complex backlight interference in coaxial interference structures. Therefore, it is necessary to propose a thermal expansion coefficient interferometry method that maintains the advantages of non-contact, high-sensitivity measurement while also considering adaptability to complex atmospheres, system stability, and engineering feasibility. Summary of the Invention

[0008] One of the objectives of this invention is to provide a thermal expansion coefficient measurement device based on a non-coaxial interference vacuum optical path. This thermal expansion coefficient measurement device can achieve high stability and high sensitivity measurement of materials with ultra-low thermal expansion coefficients while taking into account adaptability to complex atmospheres, system stability and engineering feasibility. Moreover, it does not need to consider the surface condition of the sample and is suitable for quantitative characterization of the thermal response characteristics of materials under various complex service atmospheres and extreme temperature conditions.

[0009] The second objective of this invention is to provide a method for measuring the thermal expansion coefficient of a vacuum optical path based on non-coaxial interference.

[0010] To achieve one of the above objectives, the present invention employs the following technical solution: A device for measuring the coefficient of thermal expansion in a vacuum optical path based on non-coaxial interference, the device comprising a beam vacuum transmission unit 1, a laser interference unit 2, a sample temperature control unit 3, and a data processing unit 4; The laser interference unit 2 is encapsulated within the first sealed cavity 2-13 and is used to generate a reference laser beam, a transmitted laser beam, and a reflected laser beam; and to incident the transmitted laser beam and the reflected laser beam onto the beam vacuum transmission unit 1; and to perform interference superposition of the received first lateral displacement beam and the second lateral displacement beam along the same polarization direction to extract the phase change caused by the thermal expansion of the sample under test; and to transmit the reference laser beam and the phase change to the data processing unit 4. The beam vacuum transmission unit 1 is encapsulated in a second sealed cavity 1-1 for generating different atmospheric environments. It is used to perform vacuum transmission on the received transmitted laser beam and reflected laser beam respectively, so as to obtain a first lateral displacement beam without the thermal control area of ​​the sample to be tested 5 and a second lateral displacement beam with the thermal control area of ​​the sample to be tested 5 respectively; and return the first lateral displacement beam and the second lateral displacement beam to the laser interference unit 2 in parallel directions opposite to the direction of the transmitted laser beam and the direction of the reflected laser beam respectively. The sample temperature control unit 3 is used to control the temperature of the sample 5 to be tested in the heat control area, record the temperature change value, and transmit it to the data processing unit 4. The data processing unit 4 is used to calculate the coefficient of thermal expansion of the sample under test using the reference laser beam, phase change, and temperature change values.

[0011] Furthermore, the beam vacuum transmission unit 1 includes a first vacuum quartz tube 1-2 and a second vacuum quartz tube 1-3 located within the second sealed cavity 1-1; The top end of the first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3 are respectively provided with a first pyramidal reflector 1-4 and a second pyramidal reflector 1-6; The top end of the first vacuum quartz tube 1-2 is fixedly disposed at the top end of the second sealing cavity 1-1; an elastic component is disposed between the bottom end of the second vacuum quartz tube 1-3 and the second sealing cavity 1-1. During the measurement of the coefficient of thermal expansion, the sample to be tested 5 is placed on top of the second vacuum quartz tube 1-3; the sample to be tested 5 is axially clamped between the top ends of the second vacuum quartz tube 1-3 and the second sealed cavity 1-1 by the elastic component. The first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3 are symmetrically distributed along the axial direction of the second sealing cavity 1-1 to form a unified axial positioning reference. The transmitted laser beam and the reflected laser beam are incident on the first pyramidal reflector 1-4 and the second pyramidal reflector 1-6 respectively through the bottom of the second sealed cavity 1-1, and after being reflected back at their respective pyramidal reflectors, they return to the laser interference unit 2 along their respective optical path transmission paths.

[0012] Furthermore, a quartz component 1-5 for the passage of a laser beam is provided at the bottom of the second sealed cavity 1-1.

[0013] Furthermore, the quartz component 1-5 includes a first quartz window 1-7 and a second quartz window 1-8; The lower ends of the first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3 correspond to the first quartz window 1-7 and the second quartz window 1-8, respectively.

[0014] Furthermore, the quartz components 1-5 are fused silica glass plates.

[0015] Furthermore, the laser interferometer unit 2 includes a laser beam generation module, a reference laser beam polarization detection module, a measurement beam transmission module, and a differential interference signal forming module; The laser beam generation module, the reference laser beam polarization detection module, the measurement beam transmission module, and the differential interference signal forming module are all located below the beam vacuum transmission unit 1; The laser beam generation module includes a laser emitter 2-1, a depolarizing beam splitter 2-2, and a collimator 2-3; the reference laser beam polarization detection module includes a first polarizer 2-4 and a first detector 2-7; the differential interference signal forming module includes a polarizing beam splitter 2-6, a first folding mirror 2-9, a first quarter-wave plate 2-10, and a second quarter-wave plate 2-11; the measurement beam transmission module includes a second polarizer 2-5 and a second detector 2-8. The depolarization beam splitter 2-2 splits the frequency-stabilized dual-frequency orthogonally polarized laser beam emitted by the laser emitter 2-1 into a reference signal beam and a measurement signal beam. The first detector 2-7 receives the reference signal beam through the first polarizer 2-4; the measurement signal beam is split into reflected light and transmitted light after passing through the polarizing beam splitter 2-6. The transmitted light passes through the first quarter-wave plate 2-10 and then enters the first pyramidal reflector 1-4 to obtain the first lateral displacement beam; the reflected light passes through the first folding mirror 2-9 and the second quarter-wave plate 2-11 in sequence and then enters the second pyramidal reflector 1-6 to obtain the second lateral displacement beam; the first lateral displacement beam and the second lateral displacement beam are reflected back to the polarizing beam splitter 2-6 according to their respective paths. The polarizing beam splitter 2-6 transmits the first lateral displacement beam and the second lateral displacement beam to the second polarizer 2-5; The second polarizer 2-5 uses the first lateral displacement beam and the second lateral displacement beam to perform interference superposition to form a differential interference signal; The second detector 2-8 uses the differential interference signal to extract the phase change caused by thermal expansion.

[0016] Furthermore, the laser interferometer unit 2 includes a laser beam generation module, a reference laser beam polarization detection module, a measurement beam transmission module, and a differential interference signal forming module; The laser beam generation module and the reference laser beam polarization detection module are located on the same side of the beam vacuum transmission unit 1; the measurement beam transmission module and the differential interference signal forming module are located below the beam vacuum transmission unit 1. A second folding mirror 2-12 is provided between the laser beam generation module and the measurement beam transmission module; The laser beam generation module includes a laser emitter 2-1, a depolarizing beam splitter 2-2, and a collimator 2-3; the reference laser beam polarization detection module includes a first polarizer 2-4 and a first detector 2-7; the differential interference signal forming module includes a polarizing beam splitter 2-6, a first folding mirror 2-9, a first quarter-wave plate 2-10, and a second quarter-wave plate 2-11; the measurement beam transmission module includes a second polarizer 2-5 and a second detector 2-8. The depolarization beam splitter 2-2 splits the frequency-stabilized dual-frequency orthogonally polarized laser beam emitted by the laser emitter 2-1 into a reference signal beam and a measurement signal beam. The first detector 2-7 receives the reference signal beam through the first polarizer 2-4; the measurement signal beam is split into reflected light and transmitted light after passing through the second folding mirror 2-12 and the polarizing beam splitter 2-6 in sequence. The transmitted light passes through the first quarter-wave plate 2-10 and then enters the first pyramidal reflector 1-4 to obtain the first lateral displacement beam; the reflected light passes through the first folding mirror 2-9 and the second quarter-wave plate 2-11 in sequence and then enters the second pyramidal reflector 1-6 to obtain the second lateral displacement beam; the first lateral displacement beam and the second lateral displacement beam are reflected back to the polarizing beam splitter 2-6 according to their respective paths. The polarizing beam splitter 2-6 transmits the first lateral displacement beam and the second lateral displacement beam to the second polarizer 2-5; The second polarizer 2-5 uses the first lateral displacement beam and the second lateral displacement beam to perform interference superposition to form a differential interference signal; The second detector 2-8 uses the differential interference signal to extract the phase change caused by the thermal expansion of the sample under test.

[0017] Furthermore, the coefficient of thermal expansion of the sample to be tested is: ; in, The coefficient of thermal expansion of the sample to be tested; The effective length of the sample under the initial temperature conditions; and The sample to be tested was at the first measurement temperature. Second measured temperature The corresponding equivalent length.

[0018] To achieve the second objective mentioned above, the present invention employs the following technical solution: A method for measuring the coefficient of thermal expansion in a vacuum optical path based on non-coaxial interference, wherein the coefficient of thermal expansion is measured using the aforementioned vacuum optical path coefficient of thermal expansion measuring device.

[0019] In summary, the solution proposed in this invention has the following technical effects: This invention, through a laser interferometer unit and a beam vacuum transmission unit, ensures that the entire laser optical path, from emission to interferometric detection, is in a vacuum or constant-pressure sealed environment, while the sample under test can be in an independent complex atmosphere. This effectively decouples the contradiction between atmospheric interference and optical measurement accuracy, and minimizes the influence of air refractive index fluctuations with temperature changes on the measurement signal (i.e., the measurement optical path). The invention also improves the flexibility of independent temperature control of the sample under different atmospheres through a sample temperature control unit and a beam vacuum transmission unit. Furthermore, this invention achieves highly stable and sensitive measurement of materials with ultra-low thermal expansion coefficients while considering adaptability to complex atmospheres, system stability, and engineering feasibility. It is suitable for quantitative characterization of material thermal response characteristics under various complex service atmospheres and extreme temperature conditions, meeting the application requirements for high-precision evaluation of key material thermophysical properties in fields such as precision optics and aerospace. Finally, this invention eliminates the need for sample surface coating, enabling highly sensitive and low-noise detection of minute displacements caused by thermal expansion of the sample. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the thermal expansion coefficient measuring device based on non-coaxial interference in a vacuum optical path according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the beam vacuum transmission unit structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the first laser interference unit structure and its distribution according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the second laser interference unit structure and its distribution according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the third laser interference unit structure and its distribution according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a vacuum quartz tube structure according to an embodiment of the present invention; In the figure: 1, Vacuum beam transmission unit; 1-1, Second sealed cavity; 1-2, First vacuum quartz tube; 1-3, Second vacuum quartz tube; 1-4, First pyramidal reflector; 1-5, Quartz component; 1-6, Second pyramidal reflector; 2, Laser interference unit; 2-1, Laser emitter; 2-2, Depolarizing beam splitter; 2-3, Collimator; 2-4, First polarizer; 2-7, First detector; 2-6, Polarizing beam splitter; 2-9, First folding mirror; 2-10, First quarter-wave plate; 2-11, Second quarter-wave plate; 2-5, Second polarizer; 2-8, Second detector; 2-12, Second folding mirror; 2-13, First sealed cavity; 3, Sample temperature control unit; 4-Data processing unit 4; 5, Sample to be tested; 131, Upper end face of vacuum quartz tube; 132, Lower end face of vacuum quartz tube; 133, Side wall of vacuum quartz tube. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This embodiment presents a device for measuring the thermal expansion coefficient of a vacuum optical path based on non-coaxial interference, referencing... Figure 1 The thermal expansion coefficient measuring device includes a beam vacuum transmission unit 1, a laser interferometry unit 2, a sample temperature control unit 3, and a data processing unit 4. The data processing unit 4 is electrically connected to the laser interferometry unit 2 and the sample temperature control unit 3, respectively.

[0024] In this embodiment, the laser interference unit 2 is encapsulated in the first sealed cavity 2-13 (i.e., the first sealed cavity is a vacuum cavity, which is independent of the second sealed cavity, and the structure of the vacuum cavity can be an integral structure, such as...). Figure 3 and Figure 4 As shown, it can also be two independent sealed cavities, such as... Figure 5As shown, the laser interferometer unit 2 in this embodiment is used to generate a reference laser beam, a transmitted laser beam, and a reflected laser beam; and to incident the transmitted laser beam and the reflected laser beam onto the beam vacuum transmission unit 1; and to perform interference superposition of the received first lateral displacement beam and the second lateral displacement beam along the same polarization direction to extract the phase change caused by the thermal expansion of the sample under test; and to transmit the reference laser beam and the phase change to the data processing unit 4. The laser interferometer unit 2 in this embodiment includes a laser beam generation module, a reference laser beam polarization detection module, a measurement beam transmission module, and a differential interference signal forming module.

[0025] When the laser beam generation module, the reference laser beam polarization detection module, the measurement beam transmission module, and the differential interference signal forming module are all located below the beam vacuum transmission unit 1, as follows: Figure 3 As shown, the laser beam generation module in this embodiment includes a laser emitter 2-1, a depolarizing beam splitter 2-2, and a collimator 2-3. The reference laser beam polarization detection module includes a first polarizer 2-4 and a first detector 2-7. The differential interference signal forming module includes a polarizing beam splitter 2-6, a first folding mirror 2-9, a first quarter-wave plate 2-10, and a second quarter-wave plate 2-11. The measurement beam transmission module includes a second polarizer 2-5 and a second detector 2-8.

[0026] In this embodiment, the laser emitter 2-1 emits a dual-frequency laser beam (i.e., a dual-frequency orthogonally polarized laser beam with a certain frequency difference). The dual-frequency laser beam can be generated intrinsically by a frequency-stabilized laser or obtained through acousto-optic modulation difference frequency method. The resulting low-frequency heterodyne signal is beneficial for achieving high-resolution phase demodulation and reducing the system's signal processing bandwidth requirements. The depolarization beam splitter 2-2 splits the frequency-stabilized dual-frequency laser beam emitted by the laser emitter 2-1 into a reference signal beam and a measurement signal beam. The first detector 2-7 receives the reference signal beam through the first polarizer 2-4. The measurement signal beam is split into reflected light and transmitted light after passing through the polarization beam splitter 2-6.

[0027] The transmitted light passes through the first quarter-wave plate 2-10 and then enters the first pyramidal reflector 1-4 to obtain a first laterally shifted beam. The reflected light passes sequentially through the first folding mirror 2-9 and the second quarter-wave plate 2-11 and then enters the second pyramidal reflector 1-6 to obtain a second laterally shifted beam. The first and second laterally shifted beams are reflected back to the polarizing beam splitter 2-6 along their respective paths. The polarizing beam splitter 2-6 transmits the first and second laterally shifted beams to the second polarizer 2-5. The second polarizer 2-5 uses the first and second laterally shifted beams to perform interference superposition to form a differential interference signal. The second detector 2-8 uses the differential interference signal to extract the phase change caused by thermal expansion.

[0028] When the laser beam generation module and the reference laser beam polarization detection module are located on the same side of the beam vacuum transmission unit 1, and the measurement beam transmission module and the differential interference signal forming module are located below the beam vacuum transmission unit 1, as follows: Figure 4 and Figure 5 As shown, a second folding mirror 2-12 is disposed between the laser beam generation module and the measurement beam transmission module. The laser beam generation module includes a laser emitter 2-1, a depolarizing beam splitter 2-2, and a collimator 2-3. The reference laser beam polarization detection module includes a first polarizer 2-4 and a first detector 2-7. The differential interference signal forming module includes a polarizing beam splitter 2-6, a first folding mirror 2-9, a first quarter-wave plate 2-10, and a second quarter-wave plate 2-11. The measurement beam transmission module includes a second polarizer 2-5 and a second detector 2-8.

[0029] In this embodiment, the depolarization beam splitter 2-2 splits the frequency-stabilized dual-frequency laser beam emitted by the laser emitter 2-1 into a reference signal beam and a measurement signal beam. The first detector 2-7 receives the reference signal beam through the first polarizer 2-4. The measurement signal beam passes sequentially through the second folding mirror 2-12 and the polarization beam splitter 2-6, splitting into reflected and transmitted light. The transmitted light passes through the first quarter-wave plate 2-10 and then enters the first pyramidal reflector 1-4 to obtain a first lateral displacement beam. The reflected light passes sequentially through the first folding mirror 2-9 and the second quarter-wave plate 2-11 and then enters the second pyramidal reflector 1-6 to obtain a second lateral displacement beam. The first and second lateral displacement beams are reflected back to the polarization beam splitter 2-6 along their respective paths. The polarization beam splitter 2-6 transmits the first and second lateral displacement beams to the second polarizer 2-5. The second polarizer 2-5 uses the first and second lateral displacement beams to perform interference superposition to form a differential interference signal. The second detector 2-8 uses the differential interference signal to extract the phase change caused by the thermal expansion of the sample under test.

[0030] In this embodiment, the polarizing beam splitter, the first quarter-wave plate, the second quarter-wave plate, and the first and / or second folding mirrors together constitute a non-coaxial differential heterodyne interference structure, forming a differential interference path. This embodiment employs a non-coaxial differential heterodyne interference structure, ensuring structural symmetry between the measurement arm (i.e., the measurement signal beam) and the reference arm (reference signal beam). It extracts minute displacement changes caused by sample thermal expansion through interference phase difference, possessing strong common-mode interference suppression capabilities, thereby significantly improving the system's long-term stability and environmental adaptability. Compared to the traditional Michelson coaxial interference structure, this non-coaxial layout effectively avoids the impact of backlight feedback on the stability of the heterodyne laser, further ensuring the continuity of the measurement signal and the stability of system operation. In this embodiment, the measurement signal and reference signal employ a partially co-path differential design, possessing strong common-mode interference suppression capabilities.

[0031] In this embodiment, the beam vacuum transmission unit 1 is encapsulated in a second sealed cavity 1-1 for generating different atmospheric environments (such as inert gas atmosphere, oxidation / reduction atmosphere, or vacuum atmosphere by filling with inert gas, oxidizing / reducing gas, or evacuating to simulate the actual service conditions of the sample). It is used to perform vacuum transmission on the received transmitted laser beam and reflected laser beam respectively, so as to obtain a first lateral displacement beam without the thermal control area of ​​the sample 5 to be tested and a second lateral displacement beam with the thermal control area of ​​the sample 5 to be tested; and return the first lateral displacement beam and the second lateral displacement beam to the laser interference unit 2 in parallel directions opposite to the directions of the transmitted laser beam and the reflected laser beam, respectively.

[0032] In this embodiment, the vacuum beam transmission unit 1 includes a first vacuum quartz tube 1-2 and a second vacuum quartz tube 1-3 located within the second sealed cavity 1-1. (Refer to...) Figure 2 A first pyramidal reflector 1-4 and a second pyramidal reflector 1-6 are respectively disposed inside the top end of the first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3. The top end of the first vacuum quartz tube 1-2 is fixedly disposed at the top end of the second sealed cavity 1-1. An elastic component (not shown in the figure) is disposed between the bottom end of the second vacuum quartz tube 1-3 and the second sealed cavity 1-1. During the measurement of the coefficient of thermal expansion (i.e., thermal expansion or contraction), the sample 5 to be tested is placed on the top of the second vacuum quartz tube 1-3. The sample 5 to be tested is axially clamped between the top ends of the second vacuum quartz tube 1-3 and the second sealed cavity 1-1 by the elastic component. The first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3 are symmetrically distributed along the axial direction of the second sealed cavity 1-1 to form a unified axial positioning reference. The atmosphere environment in this embodiment includes an inert gas atmosphere environment, a redox oxygen atmosphere environment, or a vacuum atmosphere environment.

[0033] In this embodiment, the transmitted laser beam and the reflected laser beam are incident on the first pyramidal reflector 1-4 and the second pyramidal reflector 1-6 respectively through the bottom of the second sealed cavity 1-1, and after being reflected back at their respective pyramidal reflectors, they return to the laser interference unit 2 along their respective optical path transmission paths.

[0034] In this embodiment, a quartz component 1-5 is disposed at the bottom of the second sealed cavity 1-1. The quartz component 1-5 in this embodiment is used to maintain the sealed state of the atmospheric environment of the beam vacuum transmission unit while realizing the transmission path of the laser beam's incident and reflected light in the vacuum optical path. One structure of the quartz component 1-5 in this embodiment includes a first quartz window 1-7 and a second quartz window 1-8. The lower ends of the first vacuum quartz tube 1-2 and the second vacuum quartz tube 1-3 correspond to the first quartz window 1-7 and the second quartz window 1-8, respectively. Another structure of the quartz component 1-5 can be a fused silica glass plate.

[0035] In this embodiment, the quartz vacuum tubes (including the first quartz vacuum tube and the second quartz vacuum tube) are an integral sealed structure, as shown in the reference. Figure 6 The system includes an axially oriented upper end face 131, a lower end face 132, and a side wall 133 of a quartz vacuum tube, all opposite each other. These three surfaces connect to form a hollow cavity that serves as a vacuum transmission channel for the laser measurement beam. The laser beam remains in a vacuum environment throughout its propagation, reflection, and return within the quartz vacuum tube. The upper end face 131 and the lower end face 132 constitute the optical working surface. These surfaces are precision-machined to ensure optical shape and surface finish, suppressing wavefront distortion during transmission and reflection of the laser beam, and serving as the reference interface for the interferometric measurement optical path. The lower end face 132 of the quartz vacuum tube is configured as a non-parallel structure relative to the upper end face 131, thereby forming a predetermined wedge angle to reduce or eliminate multiple reflections and backlight interference generated by the laser beam inside the quartz vacuum tube. A vacuum evacuation structure is provided in the side wall 133 region of the quartz vacuum tube. After the vacuum evacuation is completed, the vacuum evacuation structure is sealed to maintain a stable vacuum state inside the quartz vacuum tube.

[0036] In this embodiment, a continuous vacuum optical path is formed inside the quartz vacuum tube, constituting part of the vacuum optical path of the interferometric measurement system. This ensures that the interferometric beam remains in a closed vacuum environment throughout its entry, reflection, and return, thereby avoiding the influence of gas refractive index changes on the accuracy of optical path measurement. The cornerstone reflectors (including a first cornerstone reflector and a second cornerstone reflector) in this embodiment are disposed inside the quartz vacuum tube and aligned with the optical axis of the quartz vacuum tube (i.e., the upper end face 131 and / or the lower end face 132 of the quartz vacuum tube), used for retroreflection of the incident laser beam. The parallel retroreflection of the incident laser beam after lateral displacement by the cornerstone reflectors causes the returned beam to propagate non-coaxially with the incident beam in space, thus forming a stable reflection reference for interferometric measurement. After assembly, the quartz vacuum tube and cornerstone reflectors undergo stress relief treatment to reduce the impact of residual stress within the materials on optical stability and long-term measurement consistency.

[0037] This embodiment achieves full-link vacuum transmission of the laser beam through a first vacuum quartz tube, a second vacuum quartz tube, and a first sealed cavity, effectively suppressing the influence of changes in air refractive index on the measured optical path. In this embodiment, the sample under test is physically isolated from the laser optical path, allowing the laser beam to propagate along the quartz vacuum tube in a vacuum environment, while the sample under test is in a controllable, independent, and complex atmosphere. This embodiment uses a second sealed cavity and the coaxial arrangement of the first and second vacuum quartz tubes to provide a unified installation and positioning reference. This ensures that the first and second vacuum quartz tubes can abut or be positioned on the same reference plane during assembly, thereby establishing a consistent axial zero position and coaxial reference. This guarantees a stable and consistent relative positional relationship between the two quartz vacuum tubes (i.e., the first and second vacuum quartz tubes) and their internal optical reference components (including vacuum tube assemblies combined with the sample, such as the first pyramidal reflector, the second pyramidal reflector, and quartz components) within the system, improving optical path alignment consistency and repeatability. In this embodiment, the first and second pyramidal reflectors are respectively positioned within their respective quartz vacuum tubes and located at one end of the quartz tube, thus forming a symmetrical, common-reference reflected optical path structure in a vacuum environment.

[0038] In this embodiment, the sample temperature control unit 3 is used to control the temperature of the sample 5 to be tested in the thermal control area, record the temperature change value, and transmit it to the data processing unit 4.

[0039] The sample temperature control unit 3 in this embodiment has a temperature control range of -180℃ to 1000℃, which is suitable for thermal response testing in a wide temperature range of -180℃ to 1000℃. It has high stability, high sensitivity and environmental adaptability, and can realize accurate measurement of materials with ultra-low thermal expansion coefficient. It is suitable for precision optics, aerospace and other fields.

[0040] In this embodiment, the data processing unit 4 is used to calculate the thermal expansion coefficient of the sample under test using the reference laser beam, phase change, and temperature change values.

[0041] The coefficient of thermal expansion of the sample to be tested in this embodiment is: ; in, The coefficient of thermal expansion of the sample to be tested; The effective length of the sample under the initial temperature conditions; and The sample to be tested was at the first measurement temperature. Second measured temperature The corresponding equivalent length.

[0042] This embodiment, through a laser interferometry unit and a beam vacuum transmission unit, ensures that the entire laser optical path, from emission to interferometric detection, is in a vacuum or constant-pressure sealed environment, while the sample under test can be in an independent complex atmosphere. This effectively decouples the contradiction between atmospheric interference and optical measurement accuracy, and minimizes the influence of air refractive index fluctuations with temperature changes on the measurement signal (i.e., the measurement optical path). This embodiment, through a sample temperature control unit and a beam vacuum transmission unit, improves the flexibility of independent temperature control of the sample under different atmospheres. This embodiment achieves high-sensitivity, non-contact measurement accuracy while considering adaptability to complex atmospheres, system stability, and engineering feasibility. It enables highly stable and sensitive measurement of materials with ultra-low thermal expansion coefficients, suitable for quantitative characterization of material thermal response characteristics under various complex service atmospheres and extreme temperature conditions. It can meet the application requirements of high-precision evaluation of key material thermophysical properties in fields such as precision optics and aerospace. This embodiment eliminates the need for sample surface coating treatment, enabling highly sensitive and low-noise detection of minute displacements caused by sample thermal expansion.

[0043] Another embodiment provides a method for measuring the thermal expansion coefficient of a vacuum optical path based on non-coaxial interference. This method uses the vacuum optical path thermal expansion coefficient measuring device described in the above embodiment and includes the following steps: The laser interference unit 2, encapsulated within the first sealed cavity 2-13, generates a reference laser beam, a transmitted laser beam, and a reflected laser beam; and directs the transmitted laser beam and the reflected laser beam onto the beam vacuum transmission unit 1. The beam vacuum transmission unit 1, encapsulated in the second sealed cavity 1-1 for generating different atmospheric environments, performs vacuum transmission on the received transmitted laser beam and reflected laser beam respectively, so as to obtain the first lateral displacement beam without the thermal control area of ​​the sample to be tested 5 and the second lateral displacement beam with the thermal control area of ​​the sample to be tested 5 respectively; and returns the first lateral displacement beam and the second lateral displacement beam to the laser interference unit 2 in parallel directions opposite to the direction of the transmitted laser beam and the direction of the reflected laser beam respectively. The laser interferometer unit 2 performs interference superposition on the received first and second transverse displacement beams along the same polarization direction to extract the phase change caused by the thermal expansion of the sample under test; and transmits the reference laser beam and the phase change to the data processing unit 4. The sample temperature control unit 3 controls the temperature of the sample 5 to be tested within the thermal control area, records the temperature change value, and transmits it to the data processing unit 4. Data processing unit 4 calculates the coefficient of thermal expansion of the sample under test using the reference laser beam, phase change, and temperature change values.

[0044] The principles, formulas, and parameter definitions involved in the above embodiments are all applicable and will not be repeated here.

[0045] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A non-coaxial interference based vacuum optical path thermal expansion coefficient measuring device, characterized by, The thermal expansion coefficient measuring device includes a beam vacuum transmission unit (1), a laser interference unit (2), a sample temperature control unit (3), and a data processing unit (4). The laser interference unit (2) is encapsulated in the first sealed cavity (2-13) and is used to generate a reference laser beam, a transmitted laser beam, and a reflected laser beam; and to incident the transmitted laser beam and the reflected laser beam onto the beam vacuum transmission unit (1); and to perform interference superposition of the received first lateral displacement beam and the second lateral displacement beam along the same polarization direction to extract the phase change caused by the thermal expansion of the sample under test; and to transmit the reference laser beam and the phase change to the data processing unit (4). The beam vacuum transmission unit (1) is encapsulated in a second sealed cavity (1-1) for generating different atmospheric environments. It is used to perform vacuum transmission on the received transmitted laser beam and reflected laser beam respectively, so as to obtain the first lateral displacement beam without the thermal control area of ​​the sample to be tested (5) and the second lateral displacement beam with the thermal control area of ​​the sample to be tested (5) respectively; and return the first lateral displacement beam and the second lateral displacement beam to the laser interference unit (2) in parallel directions opposite to the direction of the transmitted laser beam and the direction of the reflected laser beam respectively. The sample temperature control unit (3) is used to control the temperature of the sample (5) to be tested in the heat control area, record the temperature change value, and transmit it to the data processing unit (4). The data processing unit (4) is used to calculate the coefficient of thermal expansion of the sample (5) under test using the reference laser beam, phase change and temperature change values.

2. The thermal expansion coefficient measuring device according to claim 1, characterized in that, The beam vacuum transmission unit (1) includes a first vacuum quartz tube (1-2) and a second vacuum quartz tube (1-3) located in the second sealed cavity (1-1). The top ends of the first vacuum quartz tube (1-2) and the second vacuum quartz tube (1-3) are respectively provided with a first pyramidal reflector (1-4) and a second pyramidal reflector (1-6). The top end of the first vacuum quartz tube (1-2) is fixedly disposed at the top end of the second sealing cavity (1-1); an elastic component is disposed between the bottom end of the second vacuum quartz tube (1-3) and the second sealing cavity (1-1); During the measurement of the coefficient of thermal expansion, the sample to be tested (5) is placed on top of the second vacuum quartz tube (1-3); the sample to be tested (5) is axially clamped between the top of the second vacuum quartz tube (1-3) and the second sealed cavity (1-1) by the elastic component; The first vacuum quartz tube (1-2) and the second vacuum quartz tube (1-3) are symmetrically distributed along the axial direction of the second sealed cavity (1-1) to form a unified axial positioning reference. The transmitted laser beam and the reflected laser beam are incident on the first pyramidal reflector (1-4) and the second pyramidal reflector (1-6) respectively through the bottom of the second sealed cavity (1-1), and after being reflected back at their respective pyramidal reflectors, they return to the laser interference unit (2) along their respective optical path transmission paths.

3. The thermal expansion coefficient measuring device according to claim 2, characterized in that, A quartz component (1-5) is provided at the bottom of the second sealing cavity (1-1).

4. The thermal expansion coefficient measuring device according to claim 3, characterized in that, The quartz component (1-5) includes a first quartz window (1-7) and a second quartz window (1-8); The lower ends of the first vacuum quartz tube (1-2) and the second vacuum quartz tube (1-3) correspond to the first quartz window (1-7) and the second quartz window (1-8), respectively.

5. The thermal expansion coefficient measuring device according to claim 3, characterized in that, The quartz components (1-5) are fused silica glass plates.

6. The thermal expansion coefficient measuring device according to claim 5, characterized in that, The laser interferometer unit (2) includes a laser beam generation module, a reference laser beam polarization detection module, a measurement beam transmission module, and a differential interference signal forming module; The laser beam generation module, the reference laser beam polarization detection module, the measurement beam transmission module, and the differential interference signal forming module are all located below the beam vacuum transmission unit (1); The laser beam generation module includes a laser emitter (2-1), a depolarizing beam splitter (2-2), and a collimator (2-3); the reference laser beam polarization detection module includes a first polarizer (2-4) and a first detector (2-7); the differential interference signal forming module includes a polarizing beam splitter (2-6), a first folding mirror (2-9), a first quarter-wave plate (2-10), and a second quarter-wave plate (2-11); the measurement beam transmission module includes a second polarizer (2-5) and a second detector (2-8). The depolarization beam splitter (2-2) splits the frequency-stabilized dual-frequency orthogonally polarized laser beam emitted by the laser emitter (2-1) into a reference signal beam and a measurement signal beam; The first detector (2-7) receives the reference signal beam through the first polarizer (2-4); the measurement signal beam is split into reflected light and transmitted light after passing through the polarizing beam splitter (2-6); The transmitted light passes through the first quarter-wave plate (2-10) and then enters the first pyramidal reflector (1-4) to obtain the first lateral displacement beam; the reflected light passes through the first folding mirror (2-9) and the second quarter-wave plate (2-11) in sequence and then enters the second pyramidal reflector (1-6) to obtain the second lateral displacement beam; the first lateral displacement beam and the second lateral displacement beam are reflected back to the polarizing beam splitter (2-6) according to their respective paths. The polarizing beam splitter (2-6) transmits the first lateral displacement beam and the second lateral displacement beam to the second polarizer (2-5). The second polarizer (2-5) uses the first lateral displacement beam and the second lateral displacement beam to perform interference superposition to form a differential interference signal; The second detector (2-8) uses the differential interference signal to extract the phase change caused by thermal expansion.

7. The thermal expansion coefficient measuring device according to claim 5, characterized in that, The laser interferometer unit (2) includes a laser beam generation module, a reference laser beam polarization detection module, a measurement beam transmission module, and a differential interference signal forming module; The laser beam generation module and the reference laser beam polarization detection module are located on the same side of the beam vacuum transmission unit (1); the measurement beam transmission module and the differential interference signal forming module are located below the beam vacuum transmission unit (1); A second folding mirror (2-12) is provided between the laser beam generating module and the measurement beam transmission module. The laser beam generation module includes a laser emitter (2-1), a depolarizing beam splitter (2-2), and a collimator (2-3). The reference laser beam polarization detection module includes a first polarizer (2-4) and a first detector (2-7); the differential interference signal forming module includes a polarizing beam splitter (2-6), a first folding mirror (2-9), a first quarter-wave plate (2-10), and a second quarter-wave plate (2-11); the measurement beam transmission module includes a second polarizer (2-5) and a second detector (2-8). The depolarization beam splitter (2-2) splits the frequency-stabilized dual-frequency orthogonally polarized laser beam emitted by the laser emitter (2-1) into a reference signal beam and a measurement signal beam; The first detector (2-7) receives the reference signal beam through the first polarizer (2-4); the measurement signal beam is split into reflected light and transmitted light after passing through the second folding mirror (2-12) and the polarizing beam splitter (2-6) in sequence; The transmitted light S2 passes through the first quarter-wave plate (2-10) and then enters the first pyramidal reflector (1-4) to obtain the first lateral displacement beam; the reflected light passes through the first folding mirror (2-9) and the second quarter-wave plate (2-11) in sequence and then enters the second pyramidal reflector (1-6) to obtain the second lateral displacement beam; the first lateral displacement beam and the second lateral displacement beam are reflected back to the polarizing beam splitter (2-6) according to their respective paths. The polarizing beam splitter (2-6) transmits the first lateral displacement beam and the second lateral displacement beam to the second polarizer (2-5). The second polarizer (2-5) uses the first lateral displacement beam and the second lateral displacement beam to perform interference superposition to form a differential interference signal; The second detector (2-8) uses the differential interference signal to extract the phase change caused by the thermal expansion of the sample under test.

8. The thermal expansion coefficient measuring device according to any one of claims 1 to 7, characterized in that, The coefficient of thermal expansion of the sample to be tested is: ； in, The coefficient of thermal expansion of the sample to be tested; The effective length of the sample under the initial temperature conditions; and The sample to be tested was at the first measurement temperature. Second measured temperature The corresponding equivalent length.

9. A method for measuring the coefficient of thermal expansion of a vacuum optical path based on non-coaxial interference, characterized in that, The method for measuring the coefficient of thermal expansion is performed using the vacuum optical path coefficient of thermal expansion measuring device described in any one of claims 1 to 8.

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