Teaching laser speckle interferometry experimental device for measuring material micro-topography
By combining laser speckle interferometry and piezoelectric phase-shifting mirrors, the problems of probe wear and systematic error in the detection of target plate materials in tokamak devices using traditional contact measurement methods have been solved, realizing non-contact, low-cost in-situ online morphology diagnosis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2025-04-22
- Publication Date
- 2026-07-10
AI Technical Summary
Traditional contact measurement methods suffer from problems such as easy wear of the detection probe, high cost, and introduction of systematic errors when detecting the morphology of the target plate material in a tokamak device, and it is difficult to achieve in-situ online diagnosis.
Using laser speckle interferometry, an experimental setup consisting of a laser, beam expander, collimating lens, beam splitter, piezoelectric phase shifter, imaging lens, and CCD camera is employed to perform non-contact detection of the surface morphology of the target material in a tokamak device. Combined with the piezoelectric phase shifter, four-step phase shift and subtraction operations are performed to obtain morphology information.
This technology enables non-contact detection of the surface morphology of target materials in tokamak devices, reducing system errors, lowering detection costs, and enabling in-situ online diagnosis.
Smart Images
Figure CN224480771U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to an experimental device for measuring the minute morphology of materials using laser speckle interferometry for teaching purposes, and belongs to the field of real-time diagnostic technology of material morphology of tokamak walls. Background Technology
[0002] Nuclear fusion is a crucial way to solve humanity's energy problems, and to achieve the rational utilization of fusion energy, the world is currently dedicated to the research of fusion devices. Tokamak-type magnetic confinement fusion is currently recognized globally as the most promising method for nuclear fusion power generation. Research on magnetic confinement fusion has revealed that the development of tokamak devices largely depends on the study of the plasma-facing materials (PFMs) interaction process and mechanism. Diagnosing the surface morphology of PFMs in fusion devices helps to understand the mechanisms and characteristics of impurity generation, transport, erosion, and redeposition processes during PFMs. Therefore, in-situ online diagnosis of the target plate material morphology and accurate measurement of changes in wall morphology in tokamak operation or linear plasma devices are of great significance for ensuring the safe operation of tokamaks and extending their operating life.
[0003] Traditional morphology detection methods are mostly contact measurements, using a probe as an intermediate medium to physically contact the surface of the object being measured to obtain its three-dimensional morphology information. However, due to its inherent characteristics, contact measurement technology has some inherent drawbacks: the probe needs to physically contact the object; a certain amount of contact pressure is unavoidable at the contact point, causing secondary deformation of the object and introducing systematic errors; the probe is prone to wear and is costly; and the probe itself has a certain volume, which negatively impacts the accurate location of deformation. Utility Model Content
[0004] To address the shortcomings of existing technologies, this invention provides an experimental device for measuring the minute morphology of materials using laser speckle interferometry, which detects the surface morphology of target plate materials in tokamak / linear plasma devices through laser speckle interferometry.
[0005] The technical solution adopted in this utility model is as follows: an experimental device for measuring the micro-morphology of materials using laser speckle interferometry for teaching purposes. This device consists of a laser, a beam expander, a collimating lens, a sample holder, a first beam splitter, a second beam splitter, a piezoelectric phase-shifting mirror, an imaging lens, and a CCD camera, all fixed on an optical platform. The laser emits a laser beam, which, after collimation and expansion by the beam expander and collimating lens, is split into two beams on the first beam splitter: an object beam and a reference beam. The object beam illuminates the sample on the sample holder and is scattered by the sample onto the second beam splitter. The reference beam illuminates the piezoelectric phase-shifting mirror, where a four-step phase shift is achieved by changing the voltage on the piezoelectric ceramic, and then reflected back onto the second beam splitter. The reference beam reflected by the piezoelectric phase-shifting mirror and the object beam scattered by the sample are combined into a single beam on the second beam splitter. This beam is then converged by the imaging lens and captured by the CCD camera to form an image.
[0006] Furthermore, the piezoelectric phase-shifting mirror includes a piezoelectric ceramic plate connected to a piezoelectric controller.
[0007] Furthermore, both the first and second beam splitters are semi-transparent and semi-reflective materials with a transmittance-to-reflection ratio of 5:5.
[0008] Furthermore, the sample holder is used to hold the sample that has been ablated by plasma.
[0009] Furthermore, the CCD camera is electrically connected to a computer.
[0010] Furthermore, the laser generates a laser wavelength of 532nm; the collimating lens has a focal length of 25mm, and the imaging lens has a focal length of 5mm.
[0011] The beneficial effects of this invention are as follows: The device has a simple structure, and its sensitivity can be dynamically expanded and selected according to actual detection conditions. Separating the object beam from the reference beam facilitates individual control of each beam. Speckle interference fringes are obtained by subtracting the intensity field distribution functions before and after displacement or deformation of the object's surface. Compared with traditional morphology detection methods, this reduces physical contact with the object, thereby avoiding secondary deformation and systematic errors. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of an experimental apparatus for measuring the minute morphology of materials using laser speckle interferometry in a teaching setting.
[0013] Figure 2 Optical path diagram of the device
[0014] Figure 3 This is a schematic diagram of a laser.
[0015] Figure 4 This is a schematic diagram of the beam expander.
[0016] Figure 5 This is a schematic diagram of the collimating lens.
[0017] Figure 6 This is a schematic diagram of the beam splitter structure.
[0018] Figure 7 This is a schematic diagram of the sample holder structure.
[0019] Figure 8 This is a schematic diagram of a piezoelectric phase-shifting mirror.
[0020] Figure 9 This is a schematic diagram of the imaging lens.
[0021] Figure 10 This is a schematic diagram of the structure of a CCD camera.
[0022] In the figure: 1. Laser, 2. Beam expander, 3. Collimating lens, 4. First beam splitter, 5. Sample holder, 6. Piezoelectric phase shifter, 7. Second beam splitter, 8. Imaging lens, 9. CCD camera, 10. Optical platform. Detailed Implementation
[0023] Figure 1 This illustrates an experimental setup for measuring the minute morphology of materials using laser speckle interferometry, intended for educational purposes. The setup includes a laser 1, a beam expander 2, a collimating lens 3, a first beam splitter 4, a sample holder 5, a piezoelectric phase-shifting mirror 6, a second beam splitter 7, an imaging lens 8, a CCD camera 9, and an optical platform 10 (e.g., ...). Figure 2-9 (As shown).
[0024] Laser 1 generates a laser with a wavelength of 532nm. This laser possesses advantages such as good monochromaticity and high interference, ensuring a clear speckle interference effect. Beam expander 2 diffuses the laser beam. Collimating lens 3 has a focal length of 25mm and collimates the laser beam. The first beam splitter 4 and the second beam splitter 7 are made of a semi-transparent, semi-reflective material with a transmittance-to-reflection ratio of 5:5. Sample holder 5 holds the plasma-ablated sample in place.
[0025] The piezoelectric phase-shifting mirror 6 contains a piezoelectric ceramic sheet connected to a piezoelectric controller. The output voltage of the piezoelectric controller causes the piezoelectric ceramic sheet to undergo nanometer-level deformation, thereby achieving precise displacement on the order of laser wavelength. The second beam splitter 7 is the same as the first beam splitter 4. The imaging lens 8 has a focal length of 5mm and can focus the light beam into the CCD camera 9. The CCD camera 9 is connected to a computer and can capture speckle interferograms.
[0026] When the above technical solution is used, the laser emitted by the laser 1 is collimated and expanded by the beam expander 2 and collimating lens 3 in the collimation and beam expansion system, and then shines on the first beam splitter 4, splitting into two beams: an object beam and a reference beam. The object beam shines on the sample in the sample holder 5 and is scattered by the sample to be tested onto the second beam splitter 7. The reference beam shines on the piezoelectric phase shifter 6, and a four-step phase shift is achieved by changing the voltage on the piezoelectric ceramic. Then it is reflected onto the second beam splitter 7. The reference beam reflected back by the piezoelectric phase shifter 6 and the object beam reflected back by the sample are combined into one beam on the second beam splitter 7. After being converged by the imaging lens 8, it is captured by the CCD camera 9 to form an image, which is then stored on the computer.
[0027] To obtain speckle interference fringes, the intensity field distribution functions of the object's surface before and after displacement or deformation are subtracted. Assume the speckle interference fringe intensities before and after displacement along the z-direction of the object are respectively... and Then their expressions are as follows:
[0028]
[0029] in and These are the light intensities of the light to be measured and the reference light, respectively. and Each corresponds to its phase. This represents the phase change caused by the displacement of the object under test. Subtracting the two equations, we get:
[0030]
[0031] The above equation is the functional expression for the speckle field correlation fringes. This is a low-frequency term, dependent on the phase change caused by the deformation of the object. This is the high-frequency carrier term, which can be averaged through filtering. Here... , For the test object along The change in displacement in the direction. From the above formula, we can see that when... hour, , is a dark stripe; when hour, , At this point, the light intensity reaches its maximum, resulting in bright stripes.
[0032] The basic principle of phase extraction from speckle interference patterns is to change the voltage of the piezoelectric ceramic, causing a minute displacement of the reference object, altering the optical path difference, and thus changing the interference fringes. Since the optical path difference contains information about the surface morphology, the phase information is extracted by analyzing the changes in the interference fringes (phase). Through data processing and image reconstruction techniques, a 3D topographic image of the surface can be reconstructed. The displacement or deformation of the surface of the object under test can be expressed as…
[0033]
[0034] In the above formula, Indicates the surface of the object being tested. The deformation or displacement generated in the axial direction, or the height difference between the measured surface and the reference surface. It is the optical path difference between the two beams. This phase difference is introduced by height difference or displacement. By changing... In other words, the displacement of the piezoelectric phase shifter can cause a phase change between the reference light and the light to be measured.
Claims
1. An experimental apparatus for measuring the minute morphology of materials using laser speckle interferometry, characterized in that: The device consists of a laser (1), a beam expander (2), a collimating lens (3), a first beam splitter (4), a second beam splitter (7), a sample holder (5), a piezoelectric phase shifter (6), an imaging lens (8), and a CCD camera (9) fixed on an optical platform (10). A laser (1) is used to emit laser light, a beam expander (2) and a collimating lens (3) are used to make the laser light shine on the first beam splitter (4) after passing through it, the first beam splitter (4) is used to split the laser light into object light and reference light, and a sample is placed on the sample holder (5); a piezoelectric phase shifter (6) is used to perform four-step phase shift of the reference light by changing the voltage on the piezoelectric ceramic. The second beam splitter (7) is used to receive the reference light reflected by the piezoelectric phase shift mirror (6) and the object light scattered by the sample on the sample holder (5) and combine them into a single beam. The imaging lens (8) is used to converge the light, and the CCD camera (9) is used to form an image.
2. The experimental apparatus according to claim 1, characterized in that: The piezoelectric phase-shifting mirror (6) includes a piezoelectric ceramic plate connected to a piezoelectric controller.
3. The experimental apparatus according to claim 1, characterized in that: The first beam splitter (4) and the second beam splitter (7) are both semi-transparent and semi-reflective materials with a transmittance-to-reflection ratio of 5:
5.
4. The experimental apparatus according to claim 1, characterized in that: The sample holder (5) is used to fix the sample that has been ablated by plasma.
5. The experimental apparatus according to claim 1, characterized in that: The CCD camera (9) is electrically connected to the computer.
6. The experimental apparatus according to claim 1, characterized in that: The laser (1) generates a laser wavelength of 532nm; the collimating lens (3) has a focal length of 25mm; and the imaging lens (8) has a focal length of 5mm.