Ultrafast laser pulse interference thermal expansion coefficient measuring device and method

Abstract

The invention discloses an ultrafast laser pulse interference thermal expansion coefficient measuring device and method, and the device comprises a pulse laser, a polarization beam splitting module, a first polarization beam splitting prism, a first cavity mirror structure, a second cavity mirror structure, a four-step phase shift detection module, an oscilloscope, and an upper computer. The polarization light splitting module divides the laser into a plurality of parallel light beams; the first polarization splitting prism divides the plurality of parallel light beams into first reflection polarized light and first transmission polarized light; the first cavity mirror structure receives the first reflected polarized light and outputs first multi-stage reflected light to the first polarization splitting prism; the second cavity mirror structure receives the first transmission polarized light and outputs second multi-stage reflected light to the first polarization splitting prism; the four-step phase shift detection module outputs four paths of interference signals; the oscilloscope receives the four paths of interference signals and presents interference measurement sine wave information; and the upper computer obtains thermal expansion coefficient measurement information. According to the invention, the high thermal expansion measurement precision of various optical mirror materials can be improved.

Description

Technical Field

[0001] This application belongs to the technical field of optical measurement, and particularly relates to an ultrafast laser pulse interference thermal expansion coefficient measurement device and method. Background Technique

[0002] With the development of semiconductor lithography technology towards sub-nanometer accuracy, the thermal stability of optical components has become the core factor restricting the performance of equipment. The demand for high-precision measurement of the coefficient of thermal expansion (CTE) is becoming increasingly urgent. Existing technologies mainly rely on laser interferometers developed by institutions such as PTB in Germany and Advance in Japan. For example, PTB in Germany uses multi-wavelength interference and CCD phase compensation technology, with a thermal expansion uncertainty of 2×10 -10 / K; The LIX series in Japan utilizes double-path Michelson interference and zero-friction translation mirrors, with a resolution of 2 nm.

[0003] However, existing technologies still have significant limitations: First, continuous laser interference only relies on spatial domain signals and cannot utilize time domain pulse superposition to improve the signal-to-noise ratio; Second, the Michelson structure is limited by the single-pass optical path and it is difficult to break through the accuracy level of 1 ppb / K; Third, there is a lack of vacuum insulation and absolute positioning design inside the cavity mirror, resulting in insufficient measurement stability due to environmental disturbances. In addition, traditional phase resolution methods have limited ability to handle multi-level reflection phase jumps, leading to accuracy attenuation under high-order harmonic interference.

[0004] Therefore, there is an urgent need for a measurement scheme that combines the time-space characteristics of ultrafast lasers and a multi-reflection resonant structure to solve the bottlenecks in accuracy, stability, and anti-interference of existing technologies. Summary of the Invention

[0005] The purpose of the embodiments of this application is to provide an ultrafast laser pulse interference thermal expansion coefficient measurement device, which is used to solve the technical problems such as the inability to perform absolute spatial position positioning, insufficient interference subdivision accuracy, and the influence of environmental vibration in thermal expansion measurement proposed in the above background technique.

[0006] To achieve the above purpose, this application adopts the following technical solutions:

[0007] An ultrafast laser pulse interference thermal expansion coefficient measurement device includes a pulsed laser, a polarization beam splitting module, a first polarization beam splitting prism, a first cavity mirror structure, a second cavity mirror structure, a four-step phase shift detection module, an oscilloscope, and a host computer;

[0008] The pulsed laser is used to emit pulsed laser light;

[0009] The polarization beam splitting module is used to split the incident pulsed laser into multiple parallel light beams and change its polarization state to adjust the energy contrast of the first mirror structure (4) and the second mirror structure (5);

[0010] The first polarization beam splitting prism is used to split the incident multiple parallel light beams into a first reflected polarized light and a first transmitted polarized light;

[0011] The first mirror structure is used to receive the first reflected polarized light and output a first multi-stage reflected light to the first polarization beam splitting prism through multiple reflections;

[0012] The second mirror structure is used to receive the first transmitted polarized light and output a second multi-stage reflected light to the first polarization beam splitting prism through multiple reflections;

[0013] The four-step phase shift detection module is used to receive the multi-stage reflected interference light of the first multi-stage reflected light and the second multi-stage reflected light and output four interference signals;

[0014] The oscilloscope is used to receive the four interference signals and present the interference measurement sine wave information of the four-step phase shift;

[0015] The upper computer is used to perform data processing on the interference signals transmitted by the oscilloscope to obtain the thermal expansion coefficient measurement information.

[0016] In a possible implementation manner, the polarization beam splitting module includes a linear polarizer, a half-wave plate, an expanding part, and a beam splitter group;

[0017] The linear polarizer is used to adjust the polarization angle of the ultrafast laser to linear polarization at 45°;

[0018] The half-wave plate is used to adjust the output light energy of the ultrafast laser;

[0019] The expanding part is used to expand the beam of the ultrafast laser into a parallel light beam;

[0020] The beam splitter group is used to split the incident parallel light beam into five parallel light beams.

[0021] In a possible implementation manner, the first mirror structure includes a first quarter-wave plate, a first partially transmissive mirror, a measuring rod, and a first highly reflective mirror;

[0022] The first quarter-wave plate is used to convert the first reflected polarized light from a vertically polarized light into a first circularly polarized light, and in the reverse incident direction, convert the first multi-stage reflected light from the first circularly polarized light into a horizontally polarized light;

[0023] The first partially transmissive mirror is used to perform energy splitting on the incident first circularly polarized light and output a first reflected light and a first transmitted light;

[0024] The first reflected light returns along the original path to the first polarization beam splitter prism;

[0025] The first transmitted light passes through the measuring rod, carries the length change information of the measuring rod, and is incident on the first highly reflective cavity mirror;

[0026] The first highly reflective cavity mirror is used to reflect the first transmitted light, so that the first transmitted light passes through the measuring rod again and returns to the first partially transmissive cavity mirror;

[0027] The first partially transmissive cavity mirror is used to perform energy splitting on the incident first transmitted light, and outputs the first order-1 reflected light and the first order-1 transmitted light;

[0028] The first order-1 reflected light passes through the measuring rod, carries the length change information of the measuring rod, and is incident on the first highly reflective cavity mirror;

[0029] The first order-1 transmitted light returns along the original path to the first polarization beam splitter prism;

[0030] The first highly reflective cavity mirror is used to reflect the first order-1 reflected light, so that the first order-1 reflected light passes through the measuring rod again and returns to the first partially transmissive cavity mirror;

[0031] The first partially transmissive cavity mirror is used to perform energy splitting on the incident first order-1 reflected light, and outputs the first order-2 reflected light and the first order-2 transmitted light;

[0032] After multiple reciprocating reflections, the first multi-order reflected light is formed.

[0033] In a possible implementation manner, the second cavity mirror structure includes a second quarter-wave plate, a second partially transmissive cavity mirror, a reference rod, and a second highly reflective cavity mirror;

[0034] The second quarter-wave plate is used to convert the first transmitted polarized light from horizontally polarized light into second circularly polarized light, and in the reverse incidence, convert the second multi-order reflected light from second circularly polarized light into vertically polarized light;

[0035] The second partially transmissive cavity mirror is used to perform energy splitting on the incident second circularly polarized light, and outputs the second reflected light and the second transmitted light;

[0036] The second reflected light returns along the original path to the first polarization beam splitter prism;

[0037] The second transmitted light passes through the reference rod, carries the length change information of the reference rod, and is incident on the second highly reflective cavity mirror;

[0038] The second highly reflective mirror is used to reflect the second transmitted light, so that the second transmitted light passes through the standard rod again and returns to the second partially transmissive mirror.

[0039] The second partially transmissive mirror is used to perform energy splitting on the incident second transmitted light, and output a second first-order reflected light and a second first-order transmitted light.

[0040] The second first-order reflected light passes through the standard rod, carries the length change information of the standard rod, and is incident on the second highly reflective mirror.

[0041] The second first-order transmitted light returns along the original path to the first polarization beam splitter prism.

[0042] The second highly reflective mirror is used to reflect the second first-order reflected light, so that the second first-order reflected light passes through the standard rod again and returns to the second partially transmissive mirror.

[0043] The second partially transmissive mirror is used to perform energy splitting on the incident second first-order reflected light, and output a second second-order reflected light and a second second-order transmitted light.

[0044] After multiple reciprocating reflections, a second multi-order reflected light is formed.

[0045] In a possible implementation manner, the four-step phase shift detection module includes a first beam splitter prism, a third quarter-wave plate, a second polarization beam splitter prism, a first high-speed photodetector, a fourth quarter-wave plate, a third polarization beam splitter prism, a second high-speed photodetector, a third high-speed photodetector, and a fourth high-speed photodetector.

[0046] The first beam splitter prism is used to perform energy splitting on the incident first multi-order reflected light and second multi-order reflected light, and divide them into a third transmitted light and a third reflected light.

[0047] The third quarter-wave plate is used to change the polarization state of the third transmitted light into two counter-rotating third circularly polarized lights.

[0048] The second polarization beam splitter prism is used to divide the two third circularly polarized lights into a P polarization component and an S polarization component, where:

[0049] The P polarization component is transmitted to form a 0° polarization interference beam, which is incident on the first high-speed photodetector for reception.

[0050] The S polarization component is reflected to form a 90° polarization interference beam, which is incident on the third high-speed photodetector for reception.

[0051] The fourth quarter-wave plate is used to change the polarization state of the third reflected light into two counter-rotating fourth circularly polarized lights.

[0052] The third polarization beam splitting prism is used to split the two beams of the fourth circularly polarized light into P-polarized components and S-polarized components, where:

[0053] The P-polarized component is transmitted to form a 180° polarized interference beam, which is incident on the second high-speed photodetector for reception;

[0054] The S-polarized component is reflected to form a 270° polarized interference beam, which is incident on the fourth high-speed photodetector for reception;

[0055] The first high-speed photodetector, the second high-speed photodetector, the third high-speed photodetector, and the fourth high-speed photodetector are respectively used to convert the four interference beams into electrical signals, and output them to an oscilloscope after pre-amplification, photoelectric conversion, and energy filtering.

[0056] In a possible implementation manner, a vacuum window and a heat insulation window are respectively provided on the first mirror structure and the second mirror structure for controlling the vacuum environment and the heating rate inside the mirror.

[0057] In a possible implementation manner, a reflecting mirror structure is further provided between the first polarization beam splitting prism and the first mirror structure and the second mirror structure;

[0058] The reflecting mirror structure includes a main reflecting prism, a first reflecting prism, and a second reflecting prism;

[0059] The main reflecting prism is used to reflect the first reflected polarized light and the first transmitted polarized light;

[0060] The first reflecting prism is used to reflect the first reflected polarized light to the first mirror structure;

[0061] The second reflecting prism is used to reflect the first transmitted polarized light to the second mirror structure.

[0062] In a second aspect, a method for a thermal expansion coefficient measuring device based on an ultrafast laser pulse configuration interferometer includes the following steps:

[0063] S1: Emitting an ultrashort pulse laser through a pulsed laser, and adjusting the polarization state and energy through a linear polarizer and a half-wave plate;

[0064] S2: Using a beam expanding part to expand the laser beam into a parallel beam, and dividing the laser into multiple parallel beams through a beam splitter group;

[0065] S3: Dividing the laser into a first reflected polarized light and a first transmitted polarized light through the first polarization beam splitting prism, and respectively incident on the first mirror structure and the second mirror structure;

[0066] S4: In the first endoscope structure and the second endoscope structure, multi-stage reflected light is formed through multiple reflections, and a four-step phase-shift detection module is used to receive the multi-stage reflected interference signal;

[0067] S5: Through phase unwrapping and reordering calculations, the thermal expansion coefficient value that varies with temperature is obtained.

[0068] In a possible implementation manner, the length changes of the first endoscope structure and the second endoscope structure are calculated by the following formula:

[0069]

[0070] where λ is the wavelength of the incident laser, is the phase change amount.

[0071] In a possible implementation manner, the thermal expansion coefficient is calculated by the following formula:

[0072]

[0073] where L is the initial length of the measuring rod, and dl(t) / dt is the length change rate caused by temperature change.

[0074] Compared with the prior art, the present application has the following beneficial effects:

[0075] An ultrafast laser pulse interference thermal expansion coefficient measuring device provided by the present application utilizes the pulse characteristics of ultrafast lasers to achieve high-precision and high-efficiency measurement of the thermal expansion coefficients of various optical mirror materials in high-end devices. Through multiple reflection interferences of the first endoscope structure and the second endoscope structure, the measurement accuracy is improved. At the same time, the four-step phase-shift detection technology ensures the accurate acquisition of phase information, providing a guarantee for accurately calculating the thermal expansion coefficient.

[0076] In a possible implementation manner, by finely adjusting the polarization state and energy of the laser, and expanding the laser beam into a parallel beam, a high-quality laser source is provided for subsequent interference measurement. The beam splitter group 204 divides the laser into multiple beams, increasing the flexibility and accuracy of the measurement system.

[0077] In one possible implementation, the first cavity mirror structure uses the polarization state conversion of light and the principle of multiple reflection interference to carry the length change information through the measuring rod, and amplify the information after multiple reflections. This design significantly improves the detection sensitivity for measuring tiny length changes and effectively solves the problem of insufficient interference subdivision accuracy. At the same time, stable optical components ensure the stability of the optical path and reduce the impact of environmental vibration on the optical path, providing a guarantee for the realization of high-precision thermal expansion coefficient measurement. In addition, during the measurement process, the length change of the measuring rod can be compared with the standard to achieve relative positioning of the spatial position to a certain extent, which is conducive to the subsequent absolute positioning.

[0078] In one possible implementation, the first cavity mirror structure uses the polarization state conversion of light and the principle of multiple reflection interference to carry the length change information through the measuring rod, and amplify the information after multiple reflections. This design significantly improves the detection sensitivity for measuring tiny length changes and effectively solves the problem of insufficient interference subdivision accuracy. At the same time, stable optical components ensure the stability of the optical path and reduce the impact of environmental vibration on the optical path, providing a guarantee for the realization of high-precision thermal expansion coefficient measurement. In addition, during the measurement process, the length change of the measuring rod can be compared with the standard to achieve relative positioning of the spatial position to a certain extent, which is conducive to the subsequent absolute positioning.

[0079] In one possible implementation, the four-step phase shift detection module accurately obtains the phase information of the interference signal through precise splitting, polarization state conversion, and the coordinated work of high-performance photoelectric detection elements. The four-step phase shift technology effectively eliminates noise and interference in interference measurement, greatly improves the phase measurement accuracy, and thus improves the accuracy of thermal expansion coefficient measurement. By converting the interference light beam into an electrical signal and processing and outputting it to the oscilloscope, an accurate data basis is provided for subsequent data analysis, solving the problem of insufficient interference subdivision accuracy. In addition, during the signal processing process, the interference light in different polarization directions is processed separately, which helps to identify and eliminate the interference of optical path offset caused by factors such as environmental vibration, and improves the stability and reliability of the measurement.

[0080] In one possible implementation, the overlapping interference of ultrafast lasers in the time domain and space domain and the multiple reflection interference of dual-cavity mirrors can be used to accurately measure the thermal expansion coefficient of materials. Compared with traditional measurement methods, this method can obtain the thermal expansion coefficient value more quickly and accurately, and can effectively solve technical problems existing in the prior art, such as the inability to perform absolute spatial positioning of thermal expansion measurement, insufficient interference subdivision accuracy, and the influence of environmental vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 A schematic diagram of the overall structure of an ultrafast laser pulse interferometer thermal expansion coefficient measurement device provided in this application;

[0082] Figure 2 Schematic diagram of the beam splitter group provided for this application;

[0083] Figure 3 Internal schematic diagram of the first partial transmission cavity mirror provided for this application;

[0084] Figure 4 Another overall structural schematic diagram of an ultrafast laser pulse interference thermal expansion coefficient measuring device provided for this application.

[0085] Reference numerals in the figure: 1, pulsed laser; 2, polarization beam splitting module; 201, linear polarizer; 202, half-wave plate; 203, beam expansion part; 204, beam splitter group; 205, planar plate; 206, double reflector; 3, first polarization beam splitting prism; 4, first cavity mirror structure; 401, first quarter-wave plate; 402, first partial transmission cavity mirror; 403, measuring rod; 404, first high-reflection cavity mirror; 405, vacuum window; 406, heat insulation window; 5, second cavity mirror structure; 501, second quarter-wave plate; 502, second partial transmission cavity mirror; 503, standard rod; 504, second high-reflection cavity mirror; 6, four-step phase shift detection module; 601, beam splitting prism; 602, third quarter-wave plate; 603, second polarization beam splitting prism; 604, first high-speed photodetector; 605, fourth quarter-wave plate; 606, third polarization beam splitting prism; 607, second high-speed photodetector; 608, third high-speed photodetector; 609, fourth high-speed photodetector; 7, oscilloscope; 8, upper computer; 9, main reflection prism 10, first reflection prism; 11, second reflection prism. Detailed implementation manners

[0086] The following further elaborates on the detailed implementation manners of this application with reference to the accompanying drawings.

[0087] As Figure 1 、 Figure 2 and Figure 3 shown, an ultrafast laser pulse interference thermal expansion coefficient measuring device of this application includes a pulsed laser 1, a polarization beam splitting module 2, a first polarization beam splitting prism 3, a first cavity mirror structure 4, a second cavity mirror structure 5, a four-step phase shift detection module 6, an oscilloscope 7, and an upper computer 8.

[0088] The pulsed laser 1 emits a beam of ultrafast laser, which has extremely high time resolution and spatial resolution, can achieve high-precision interference measurement, and at the same time reduces the influence of thermal effects on the measurement results.

[0089] Optionally, the pulse width range of the ultrafast laser can be 50 - 500 ps, and preferably an ultrafast laser with a pulse width of 300 ps and a laser wavelength of 532 nm.

[0090] The polarization beam splitting module 2 is used to divide the incident ultrafast laser into five parallel light beams and change their polarization states to adjust the energy contrast of the first mirror structure 4 and the second mirror structure 5.

[0091] Specifically, the beam distribution of the ultrafast laser is as follows: one beam in the middle and four beams around it, and they are evenly distributed.

[0092] The first polarization beam splitting prism 3 divides the incident five parallel light beams into a first reflected polarized light and a first transmitted polarized light, and makes them enter the first mirror structure 4 and the second mirror structure 5 respectively.

[0093] The first mirror structure 4 is used to receive the first reflected polarized light and output a first multi-reflected light to the first polarization beam splitting prism 3 through multiple reflections.

[0094] The second mirror structure 5 can receive the first transmitted polarized light and output a second multi-reflected light to the first polarization beam splitting prism 3 through multiple reflections.

[0095] The four-step phase shift detection module 6 can receive the multi-reflected interference light of the first multi-reflected light and the second multi-reflected light and output four interference signals.

[0096] The oscilloscope 7 receives the four interference signals and presents the interference measurement sine wave information of the four-step phase shift.

[0097] The host computer 8 can perform data processing on the interference signals transmitted by the oscilloscope 7 to obtain the thermal expansion coefficient measurement information.

[0098] In the embodiment of the present application, by utilizing the pulse characteristics of the ultrafast laser, high-precision and high-efficiency measurement of the thermal expansion coefficient of various optical mirror materials in high-end devices is realized. Through multiple reflection interference, the measurement accuracy is improved. At the same time, the four-step phase shift detection technology ensures the accurate acquisition of phase information, providing a guarantee for accurately calculating the thermal expansion coefficient.

[0099] In a possible embodiment, the polarization beam splitting module 2 may include a linear polarizer 201, a half-wave plate 202, a beam expansion part 203, and a beam splitting mirror group 204.

[0100] The linear polarizer 201 adjusts the polarization angle of the laser to linear polarization of 45°. The half-wave plate 202 adjusts the laser energy. The beam expansion part 203 expands the beam of the ultrafast laser into a parallel beam, realizing several times expansion of the beam of the ultrafast laser, and presenting a parallel beam with a diameter of about 12 mm in space.

[0101] The beam splitting mirror group 204 divides the parallel beam into five parallel beams and emits the five parallel beams to the first polarization beam splitting prism 3.

[0102] Specifically, an ultrafast laser beam with a diameter of 6 mm and a linearly polarized state of 45° is incident on the beam splitter group 204.

[0103] The beam splitter group 204 can be composed of a plane plate 205 and four double mirrors 206.

[0104] After the ultrafast laser passes through the plane plate 205 and undergoes two internal reflections inside the double mirror 206, five parallel light beams are formed on the rear surface. These light beams have the same polarization direction, all being linearly polarized light at 45°, and the energy of the middle light beam is high, while the energies of the light beams on both sides are the same.

[0105] In the embodiment of the present application, by finely adjusting the polarization state and energy of the laser, and expanding the laser beam into parallel light beams, a high-quality laser source is provided for subsequent interference measurement. The beam splitter group 204 divides the laser into multiple beams, increasing the flexibility and accuracy of the measurement system.

[0106] In a possible embodiment, the first cavity mirror structure 4 may include a first quarter-wave plate 401, a first partially transmissive cavity mirror 402, a measuring rod 403, and a first highly reflective cavity mirror 404.

[0107] The first quarter-wave plate 401 converts the first reflected polarized light from vertically polarized light into first circularly polarized light.

[0108] The first partially transmissive cavity mirror 402 performs energy splitting on the incident first circularly polarized light, outputting a first reflected light and a first transmitted light. In the reverse incident case, it converts the first multi-stage reflected light from first circularly polarized light into horizontally polarized light.

[0109] The first reflected light returns along the original path to the first polarization beam splitter 3. The first transmitted light passes through the measuring rod 403, carries the length change information of the measuring rod 403, and is incident on the first highly reflective cavity mirror 404.

[0110] The first highly reflective cavity mirror 404 reflects the first transmitted light, causing the first transmitted light to pass through the measuring rod 403 again and return to the first partially transmissive cavity mirror 402.

[0111] The first partially transmissive cavity mirror 402 is used to perform energy splitting on the incident first transmitted light, outputting a first level-1 reflected light and a first level-1 transmitted light.

[0112] The first level-1 reflected light passes through the measuring rod 403, carries the length change information of the measuring rod 403, and is incident on the first highly reflective cavity mirror 404.

[0113] The first level-1 transmitted light returns along the original path to the first polarization beam splitter 3.

[0114] The first high-reflection cavity mirror 404 is used to reflect the first-order reflected light, so that the first-order reflected light passes through the measuring rod 403 again and returns to the first partially transmitting cavity mirror 402;

[0115] The first partially transmissive cavity mirror 402 is used to perform energy splitting on the incident first-order reflected light, outputting first-order reflected light and first-order transmitted light, and forming first multi-order reflected light after multiple reciprocating reflections.

[0116] In the embodiment of the present application, the first cavity mirror structure 4 uses the polarization state conversion and multiple reflection interference principle of light to carry the length change information through the measuring rod 403, and amplifies the information through multiple reflections. This design significantly improves the detection sensitivity of the slight length change of the measuring rod 403, and effectively solves the problem of insufficient interference subdivision accuracy. At the same time, the stable optical element ensures the stability of the optical path, reduces the impact of environmental vibration on the optical path, and provides a guarantee for the realization of high-precision thermal expansion coefficient measurement. In addition, during the measurement process, the length change of the measuring rod 403 can be compared with the standard, and the relative positioning of the spatial position can be achieved to a certain extent, which is helpful for the subsequent absolute positioning.

[0117] In a possible embodiment, the second cavity mirror structure 5 may include a second quarter wave plate 501 , a second partially transmitting cavity mirror 502 , a standard rod 503 , and a second high-reflection cavity mirror 504 .

[0118] The second quarter wave plate 501 converts the first transmitted polarized light from horizontal linear polarized light to second circular polarized light, and converts the second multi-level reflected light from second circular polarized light to vertical linear polarized light under reverse incidence.

[0119] The second partially transmissive cavity mirror 502 performs energy splitting on the incident second circularly polarized light, and outputs a second reflected light and a second transmitted light.

[0120] The second reflected light returns to the first polarization beam splitting prism 3 along the original path.

[0121] The second projection light passes through the standard rod 503 , carries the length change information of the standard rod 503 , and is incident on the second high-reflection cavity mirror 504 .

[0122] The second high-reflection cavity mirror 504 reflects the second projection light, so that the second projection light passes through the standard rod 503 again and returns to the second partial transmission cavity mirror 502 .

[0123] The second partially transmissive cavity mirror 502 is used to perform energy splitting on the incident second transmitted light, and output a second first-order reflected light and a second first-order transmitted light.

[0124] The second first-order reflected light passes through the standard rod 503 , carries the length change information of the standard rod 503 , and is incident on the second high-reflection cavity mirror 504 .

[0125] The second first-order transmitted light returns to the first polarization beam splitting prism 3 along the original path.

[0126] The second high-reflection cavity mirror 504 is used to reflect the second first-order reflected light, so that the second first-order reflected light passes through the standard rod 503 again and returns to the second partial transmission cavity mirror 502 .

[0127] The second partially transmissive cavity mirror 502 is used to perform energy splitting on the incident second first-order reflected light and output second second-order reflected light. The second second-order transmitted light forms second multi-order reflected light after multiple reciprocating reflections.

[0128] In the embodiment of the present application, the second cavity mirror structure 5 cooperates with the first cavity mirror structure 4 to provide a stable reference length through the standard rod 503, and compares the length change of the measuring rod 403 for interference measurement. The influence of environmental factors on the measurement results is effectively eliminated, the accuracy of the measurement is greatly improved, and the problem of environmental vibration affecting the measurement accuracy is solved. Multiple reflection interference further enhances the detection capability of tiny length changes and improves the interference subdivision accuracy. At the same time, the relative stable relationship between the two cavity mirror structures helps to achieve absolute positioning of the spatial position. By comparing the relationship between the optical path changes in the two cavity mirrors and the standard, a data basis is provided for absolute positioning of the spatial position.

[0129] Specifically, when the thermal expansion material to be measured is BK7 glass, the measuring rod 403 and the standard rod 503 are both made of BK7 glass, and the measuring rod 403 can be used as a standard part. The materials of the first partially transmitting cavity mirror 402, the first high-reflecting cavity mirror 404, the second partially transmitting cavity mirror 502 and the second high-reflecting cavity mirror 504 are all made of fused quartz or microcrystals, and zero expansion glass is usually used.

[0130] When the thermal expansion material to be measured is fused quartz glass, the measuring rod 403 and the standard rod 503 are both made of fused quartz glass, and the measuring rod 403 is a fused quartz standard part, and the materials of the first partially transmitting cavity mirror 402, the first high-reflecting cavity mirror 404, the second partially transmitting cavity mirror 502 and the second high-reflecting cavity mirror 504 are all microcrystalline or zero-expansion glass.

[0131] When the thermal expansion material to be measured is microcrystalline, all materials used are microcrystalline glass or materials whose thermal expansion coefficient is closer to 0.

[0132] In a possible embodiment, the four-step phase-shift detection module 6 includes a first beam splitter prism 601, a third quarter-wave plate 602, a second polarization beam splitter prism 603, a first high-speed photodetector 604, a fourth quarter-wave plate 605, a third polarization beam splitter prism 606, a second high-speed photodetector 607, a third high-speed photodetector 608 and a fourth high-speed photodetector 609.

[0133] The first beam splitting prism 601 is used to perform energy splitting on the incident first multi-stage reflected light and second multi-stage reflected light, and split them into a third transmitted light and a third reflected light.

[0134] The third quarter-wave plate 602 is used to change the polarization state of the third transmitted light into two third circularly polarized lights rotating in opposite directions.

[0135] The second polarization beam splitting prism 603 is used to split the two third circularly polarized lights into a P polarization component and an S polarization component, where:

[0136] The P polarization component is transmitted to form a 0° polarization interference beam, which is incident on the first high-speed photodetector 604 for reception.

[0137] The S polarization component is reflected to form a 90° polarization interference beam, which is incident on the third high-speed photodetector 608 for reception.

[0138] The fourth quarter-wave plate 605 is used to change the polarization state of the third reflected light into two fourth circularly polarized lights rotating in opposite directions.

[0139] The third polarization beam splitting prism 606 is used to split the two fourth circularly polarized lights into a P polarization component and an S polarization component, where:

[0140] The P polarization component is transmitted to form a 180° polarization interference beam, which is incident on the second high-speed photodetector 607 for reception.

[0141] The S polarization component is reflected to form a 270° polarization interference beam, which is incident on the fourth high-speed photodetector 609 for reception.

[0142] The first high-speed photodetector 604, the second high-speed photodetector 607, the third high-speed photodetector 608, and the fourth high-speed photodetector 609 are respectively used to convert the four interference beams into electrical signals, and after pre-amplification, photoelectric conversion, and energy filtering, output them to the oscilloscope 7 to present the interference measurement sine wave information with four-phase shifts, and input them to the host computer 8 for data processing to obtain the thermal expansion coefficient measurement information.

[0143] In the embodiments of the present application, the four-step phase-shift detection module 6 accurately obtains the phase information of the interference signal through the coordinated work of precise beam splitting, polarization state conversion, and high-performance optoelectronic detection elements. The four-step phase-shift technology effectively eliminates noise and interference in interference measurement, greatly improves the phase measurement accuracy, and thus improves the accuracy of thermal expansion coefficient measurement. By converting the interference beam into an electrical signal and processing it for output to an oscilloscope, an accurate data basis is provided for subsequent data analysis, solving the problem of insufficient interference subdivision accuracy. And during the signal processing process, the interference light in different polarization directions is processed separately, which helps to identify and eliminate the optical path offset interference caused by factors such as environmental vibration, improving the stability and reliability of the measurement.

[0144] In a possible embodiment, a vacuum window 405 and a heat insulation window 406 are respectively installed on the first mirror structure 4 and the second mirror structure 5.

[0145] The ultrafast laser passes through the vacuum window 405 and is incident on the first mirror structure 4 through the heat insulation window 406.

[0146] Similarly, the ultrafast laser passes through the vacuum window 405 and is incident on the second mirror structure 5 through the heat insulation window 406.

[0147] The vacuum window 405 uses an optical window material with high vacuum sealing performance, which can effectively maintain the vacuum environment inside the mirror and reduce the interference of media such as air on the optical path.

[0148] The heat insulation window 406 uses a material with good heat insulation performance, such as multi-layer heat insulation glass, etc., to control the heating rate inside the mirror and make the temperature change uniform.

[0149] The vacuum window 405 is used to form a vacuum environment, and the heat insulation window 406 is used to control the heating rate and temperature uniformity of the first mirror structure 4 and the second mirror structure 5. The thermal expansion coefficients of the materials of the first partial transmission mirror 402 and the first high-reflection mirror 404 in the first mirror structure 4 are the same, and the thermal expansion deformation amount is much lower than that of the measuring rod 403.

[0150] In the embodiments of the present application, by controlling the vacuum environment in the first endoscope structure 4 and the second endoscope structure 5, the scattering and absorption effects of air molecules on the laser propagation can be reduced, the optical path stability and the clarity of interference fringes can be improved, and the problem of environmental vibration affecting measurement can be solved. By precisely controlling the heating rate and temperature uniformity, the situation of inaccurate measurement of material thermal expansion caused by abnormal temperature changes can be avoided, and the accuracy and reliability of the measurement are improved. The stable internal environment of the endoscope provides a guarantee for realizing high-precision measurement of the coefficient of thermal expansion. At the same time, the stable control of the vacuum and heat insulation environment helps to maintain the relative stability of the double-endoscope structure, creates favorable conditions for realizing absolute positioning of the spatial position, and reduces the changes in the position of the endoscope and the optical path caused by environmental factors.

[0151] In another possible embodiment, as Figure 4 shown, a reflecting endoscope structure may also be provided between the first polarization beam splitter prism 3 and the first endoscope structure 4 and the second endoscope structure 5.

[0152] The reflecting endoscope structure includes a main reflecting prism 9, a first reflecting prism 10, and a second reflecting prism 11;

[0153] The main reflecting prism 9 is used to reflect the first reflected polarized light and the first transmitted polarized light.

[0154] The first reflecting prism 10 is used to reflect the first reflected polarized light to the first endoscope structure 4.

[0155] The second reflecting prism 11 is used to reflect the first transmitted polarized light to the second endoscope structure 5.

[0156] In the embodiments of the present application, by arranging a reflecting endoscope structure between the first polarization beam splitter prism 3 and the first endoscope structure 4 and the second endoscope structure 5, the optical path layout has high flexibility, can cleverly adjust the optical path direction according to the actual space and equipment layout, and avoid obstacles; it plays an isolation and buffering role, effectively weakens the interference of environmental vibration on the interference measurement of the endoscope structure, and enhances the measurement stability; it can also optimize the parallelism and alignment of the two beams of light before entering the endoscope, significantly improve the interference effect, improve the interference subdivision accuracy, and help to measure the coefficient of thermal expansion of the material more accurately.

[0157] In a possible embodiment, converging lenses are respectively installed at the front ends of the first high-speed photodetector 604, the second high-speed photodetector, the third high-speed photodetector 608, and the fourth high-speed photodetector 609. The focal length and size of the converging lens are selected according to the spot sizes and propagation distances of the measurement beam and the reference beam, and can accurately converge the measurement beam and the reference beam on the photosensitive surface of the detector.

[0158] Specifically, a convex lens with a focal length of 10 cm can be selected as the converging lens, and the best converging effect can be achieved by precisely adjusting its position.

[0159] In the embodiments of the present application, the converging lens improves the reception efficiency of the detector for the measurement beam and the reference beam, and enhances the intensity of the photoelectric conversion signal. The beam is accurately converged on the photosensitive surface of the detector, avoiding signal loss and measurement errors caused by beam divergence or deviation, improving the detection accuracy of the four-step phase shift detection module 6, and further enhancing the measurement accuracy and stability of the entire coefficient of thermal expansion measurement device. In a complex measurement environment, the use of the converging lens helps to reduce the influence of factors such as environmental vibration on the beam propagation, ensuring that the detector receives stable and accurate signals, and providing a more reliable signal basis for achieving high-precision coefficient of thermal expansion measurement and absolute positioning of spatial positions.

[0160] A method for a coefficient of thermal expansion measurement device based on an ultrafast laser pulse configuration interferometer includes the following steps:

[0161] S1: Emitting an ultrashort pulse laser through the pulsed laser 1, and adjusting the polarization state and energy through the linear polarizer 201 and the half-wave plate 202.

[0162] First, turn on the pulsed laser 1 to emit an ultrashort pulse laser. The laser passes through the linear polarizer 201, and its polarization angle is adjusted to linear polarization at 45°. Then, it passes through the half-wave plate 202 to adjust the energy of the outgoing light according to the actual measurement requirements.

[0163] S2: Using the beam expansion part 203 to expand the laser beam into a parallel beam, and dividing the laser into multiple parallel beams through the beam splitter group 204.

[0164] Using the beam expansion part 203, such as a Galilean telescope beam expander, to expand the laser beam into a parallel beam, and then through the beam splitter group 204, dividing the laser into five parallel beams

[0165] S3: Dividing the laser into a first reflected polarized light and a first transmitted polarized light through the first polarization beam splitter prism 3, and respectively incident on the first mirror structure 4 and the second mirror structure 5.

[0166] The parallel beam is incident on the first polarization beam splitter prism 3, and is divided into a first reflected polarized light and a first transmitted polarized light, which are respectively incident on the first mirror structure 4 and the second mirror structure 5.

[0167] S4: In the first mirror structure 4 and the second mirror structure 5, forming multi-stage reflected light through multiple reflections, and using the four-step phase shift detection module 6 to receive the multi-stage reflected interference signal

[0168] In the first mirror structure 4 and the second mirror structure 5, the light forms multi-stage reflected light through multiple reflections, and the four-step phase shift detection module 6 receives the multi-stage reflected interference signal according to its working principle.

[0169] S5: Obtain the thermal expansion coefficient value varying with temperature through phase unwrapping and reordering calculations.

[0170] Finally, the host computer 8 performs phase unwrapping and reordering calculations on the interference signal through a specific algorithm to obtain the thermal expansion coefficient value varying with temperature.

[0171] Exemplarily, during the measurement process, slowly increase the temperature inside the first mirror structure 4 while keeping the second mirror structure 5 at room temperature, and monitor the change of the interference signal in real time and perform calculations.

[0172] In the embodiment of the present application, by using the overlapping interference of the ultrafast laser in the time domain and the spatial domain and the multiple reflection interference of the double mirrors, the accurate measurement of the thermal expansion coefficient of the material can be realized. Compared with the traditional measurement method, this method can obtain the thermal expansion coefficient value more quickly and accurately, and can effectively solve the technical problems existing in the prior art, such as the inability to perform absolute spatial position positioning in thermal expansion measurement, insufficient interference subdivision accuracy, and the influence of environmental vibration.

[0173] In a possible embodiment, the length changes of the first mirror structure 4 and the second mirror structure 5 are calculated by the following formula:

[0174]

[0175] where λ is the wavelength of the incident laser, is the phase change amount.

[0176] In actual measurement, when the light in the first mirror structure 4 and the second mirror structure 5 interferes, the phase change amount is obtained through a high-precision phase detection instrument. Given the known wavelength λ of the incident laser, substituting it into the formula can calculate the length changes of the first mirror structure 4 and the second mirror structure 5.

[0177] Exemplarily, in one measurement, the wavelength λ of the incident laser is 532 nm, and the phase change amount measured by the phase detection instrument is 0.1 rad. Substituting it into the formula can calculate the length change amount.

[0178] In this embodiment, this formula provides an accurate mathematical basis for calculating the length changes of the first mirror structure 4 and the second mirror structure 5. By accurately measuring the phase change amount and the known wavelength of the incident laser, the length change can be accurately calculated, which is crucial for the subsequent calculation of the thermal expansion coefficient of the material. Compared with other methods for indirectly measuring length changes, calculating the length change based on the interference principle using this formula has higher accuracy and reliability, and can effectively improve the accuracy of the thermal expansion coefficient measurement.

[0179] In a possible implementation, the coefficient of thermal expansion is calculated by the following formula:

[0180]

[0181] where L is the initial length of the measuring rod 403, and dl(t) / dt is the rate of change of length caused by the temperature change.

[0182] During the measurement process, first measure the length L of the measuring rod 403 in the initial state, and then calculate the rate of change of length dl(t) / dt caused by the temperature change by monitoring the change in the length of the measuring rod 403 during the temperature change. Substitute L and dl(t) / dt into the formula to calculate the coefficient of thermal expansion of the material.

[0183] Exemplarily, the initial length L of the measuring rod 403 is 10 cm. During the process of the temperature rising from 20°C to 30°C, the change in the length of the measuring rod 403 is accurately measured by the measuring device, and the rate of change of length dl(t) / dt is calculated to be 1×10 -5 cm / °C. Substitute it into the formula to calculate the coefficient of thermal expansion.

[0184] In this embodiment, the formula clarifies the relationship between the coefficient of thermal expansion, the initial length of the measuring rod 403, and the rate of change of length caused by the temperature change. By accurately measuring the relevant parameters and substituting them into the formula for calculation, the coefficient of thermal expansion of the material can be directly obtained. This calculation method is based on actual measurement data, has a clear physical meaning and high accuracy, and provides a reliable method for the measurement and analysis of the coefficient of thermal expansion of materials.

[0185] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: modifying the technical solutions described in the foregoing embodiments, or equivalently replacing some or all of the technical features therein, does not deviate from the essence of the corresponding technical solutions of the technical solutions of the present application.

Claims

1. An ultrafast laser pulse interference thermal expansion coefficient measurement device, comprising a pulse laser (1), a polarization beam splitting module (2), a first polarization beam splitting prism (3), a first cavity mirror structure (4), a second cavity mirror structure (5), a four-step phase shift detection module (6), an oscilloscope (7) and a host computer (8), characterized in that: The pulse laser (1) is used to emit ultrafast laser; The polarization beam splitting module (2) is used to split the incident ultrafast laser into multiple parallel beams, and change the polarization state thereof to adjust the energy contrast between the first cavity mirror structure (4) and the second cavity mirror structure (5); The first polarization beam splitter prism (3) is used to split the incident multiple parallel light beams into first reflected polarized light and first transmitted polarized light; The first cavity mirror structure (4) is used to receive the first reflected polarized light, and output the first multi-level reflected light to the first polarization beam splitting prism (3) through multiple reflections; The second cavity mirror structure (5) is used to receive the first transmitted polarized light, and output the second multi-level reflected light to the first polarization beam splitting prism (3) through multiple reflections; The four-step phase shift detection module (6) is used to receive the multi-level reflected interference light of the first multi-level reflected light and the second multi-level reflected light, and output four-channel interference signals; The oscilloscope (7) is used to receive four-way interference signals and present interference measurement sine wave information with four-step phase shift; The host computer (8) is used to perform data processing on the interference signal transmitted by the oscilloscope (7) to obtain thermal expansion coefficient measurement information.

2. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: The polarization beam splitting module (2) comprises a linear polarizer (201), a half-wave plate (202), a beam expansion part (203) and a beam splitter group (204); The linear polarizer (201) is used to adjust the polarization angle of the ultrafast laser to a linear polarization angle of 45°; The half wave plate (202) is used to adjust the output light energy of the ultrafast laser; The beam expansion part (203) is used to expand the beam of the ultrafast laser into a parallel beam; The beam splitter group (204) is used to split the incident parallel light beam into five parallel light beams.

3. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: The first cavity mirror structure (4) comprises a first quarter wave plate (401), a first partially transmitting cavity mirror (402), a measuring rod (403) and a first high-reflection cavity mirror (404); The first quarter wave plate (401) is used to convert the first reflected polarized light from vertical linear polarized light into first circularly polarized light, and to convert the first multi-level reflected light from first circularly polarized light into horizontal linear polarized light under reverse incidence; The first partially transmissive cavity mirror (402) is used to perform energy splitting on the incident first circularly polarized light, and output a first reflected light and a first transmitted light; The first reflected light returns to the first polarization beam splitting prism (3) along the original path; The first transmitted light passes through the measuring rod (403), carries the length change information of the measuring rod (403), and is incident on the first high-reflection cavity mirror (404); The first high-reflection cavity mirror (404) is used to reflect the first transmitted light, so that the first transmitted light passes through the measuring rod (403) again and returns to the first partial transmission cavity mirror (402); The first partially transmissive cavity mirror (402) is used to perform energy splitting on the incident first transmitted light, and output first first-order reflected light and first first-order transmitted light; The first-order reflected light passes through the measuring rod (403), carries the length change information of the measuring rod (403), and is incident on the first high-reflection cavity mirror (404); The first-stage transmitted light returns to the first polarization beam splitting prism (3) along the original path; The first high-reflection cavity mirror (404) is used to reflect the first first-order reflected light, so that the first first-order reflected light passes through the measuring rod (403) again and returns to the first partially transmitting cavity mirror (402); The first partially transmissive cavity mirror (402) is used to perform energy splitting on the incident first-order reflected light and output first-order reflected light. The first-order reflected light is reciprocated for multiple times to form first multi-order reflected light.

4. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: The second cavity mirror structure (5) comprises a second quarter wave plate (501), a second partially transmitting cavity mirror (502), a standard rod (503) and a second high-reflection cavity mirror (504); The second quarter wave plate (501) is used to convert the first transmitted polarized light from horizontal linear polarized light to second circularly polarized light; and under reverse incidence, convert the second multi-level reflected light from the second circularly polarized light to vertical linear polarized light; The second partially transmissive cavity mirror (502) is used for performing energy splitting on the incident second circularly polarized light, and outputting second reflected light and second transmitted light; The second reflected light returns to the first polarization beam splitting prism (3) along the original path; The second transmitted light passes through the standard rod (503), carries the length change information of the standard rod (503), and is incident on the second high-reflection cavity mirror (504); The second high-reflection cavity mirror (504) is used to reflect the second transmitted light, so that the second transmitted light passes through the standard rod (503) again and returns to the second partial transmission cavity mirror (502); The second partially transmissive cavity mirror (502) is used to perform energy splitting on the incident second transmitted light, and output second first-order reflected light and second first-order transmitted light; The second first-order reflected light passes through the standard rod (503), carries the length change information of the standard rod (503), and is incident on the second high-reflection cavity mirror (504); The second first-order transmitted light returns to the first polarization beam splitting prism (3) along the original path; The second high-reflection cavity mirror (504) is used to reflect the second first-order reflected light, so that the second first-order reflected light passes through the standard rod (503) again and returns to the second partially transmissive cavity mirror (502); The second partially transmissive cavity mirror (502) is used to perform energy splitting on the incident second first-order reflected light and output second second-order reflected light, and the second second-order transmitted light forms second multi-order reflected light after multiple reciprocating reflections.

5. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: The four-step phase-shift detection module (6) comprises a first beam splitter prism (601), a third quarter-wave plate (602), a second polarization beam splitter prism (603), a first high-speed photodetector (604), a fourth quarter-wave plate (605), a third polarization beam splitter prism (606), a second high-speed photodetector (607), a third high-speed photodetector (608) and a fourth high-speed photodetector (609); The first beam splitter prism (601) is used to perform energy splitting on the incident first multi-level reflected light and the second multi-level reflected light to split the incident light into third transmitted light and third reflected light; The third quarter wave plate (602) is used to change the polarization state of the third transmitted light into two third circularly polarized lights that rotate forward and backward; The second polarization beam splitter (603) is used to split the two third circularly polarized light beams into a P polarization component and an S polarization component, wherein: The P polarization component is transmitted to form a 0° polarization interference beam, which is incident on a first high-speed photodetector (604) for reception; The S polarization component is reflected to form a 90° polarization interference beam, which is incident on a third high-speed photodetector (608) for reception; The fourth quarter wave plate (605) is used to change the polarization state of the third reflected light into two beams of fourth circularly polarized light that rotate forward and backward; The third polarization beam splitter (606) is used to split the two fourth circularly polarized lights into a P polarization component and an S polarization component, wherein: The P polarization component is transmitted to form a 180° polarization interference beam, which is incident on a second high-speed photodetector (607) for reception; The S polarization component is reflected to form a 270° polarization interference beam, which is incident on a fourth high-speed photodetector (609) for reception; The first high-speed photodetector (604), the second high-speed photodetector (607), the third high-speed photodetector (608) and the fourth high-speed photodetector (609) are respectively used to convert the four-path interference light beams into electrical signals, and output them to the oscilloscope (7) after pre-amplification, photoelectric conversion and energy filtering.

6. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: The first cavity mirror structure (4) and the second cavity mirror structure (5) are respectively provided with a vacuum window (405) and a heat insulation window (406) for controlling the vacuum environment and the heating rate inside the cavity mirror.

7. The ultrafast laser pulse interferometer thermal expansion coefficient measuring device according to claim 1, characterized in that: A reflective cavity mirror structure is also provided between the first polarization beam splitting prism (3), the first cavity mirror structure (4) and the second cavity mirror structure (5); The reflective cavity mirror structure comprises a main reflective prism (9), a first reflective prism (10) and a second reflective prism (11); The main reflecting prism (9) is used to reflect the first reflected polarized light and the first transmitted polarized light; The first reflecting prism (10) is used to reflect the first reflected polarized light to the first cavity mirror structure (4); The second reflecting prism (11) is used for reflecting the first transmitted polarized light to the second cavity mirror structure (5).

8. A method for measuring thermal expansion coefficient based on an ultrafast laser pulse configuration interferometer according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: emitting ultrashort pulse laser light through a pulse laser (1), and adjusting the polarization state and energy through a linear polarizer (201) and a half-wave plate (202); S2: using a beam expander (203) to expand the laser beam into a parallel beam, and using a beam splitter group (204) to split the laser beam into a plurality of parallel beams; S3: Splitting the laser light into a first reflected polarized light and a first transmitted polarized light through a first polarization splitting prism (3), and respectively incident on a first cavity mirror structure (4) and a second cavity mirror structure (5); S4: in the first cavity mirror structure (4) and the second cavity mirror structure (5), a multi-level reflected light is formed by multiple reflections, and a four-step phase shift detection module (6) is used to receive the multi-level reflected interference signal; S5: Obtain the temperature-dependent thermal expansion coefficient value through phase unwrapping and reordering calculation.

9. The method of the ultrafast laser pulse interferometer thermal expansion coefficient measurement device according to claim 8, characterized in that: The length changes of the first laparoscope structure (4) and the second laparoscope structure (5) are calculated by the following formula: Where λ is the incident laser wavelength, is the phase change.

10. The method of the ultrafast laser pulse interferometer thermal expansion coefficient measurement device according to claim 8, characterized in that: The thermal expansion coefficient is calculated by the following formula: Wherein, L is the initial length of the measuring rod (403), and dl(t) / dt is the length change rate caused by temperature change.

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