A laser scanning system for substance detection

Abstract

The present application relates to the field of detection, in particular to a kind of laser scanning system for substance detection, the system includes: laser, mirror, refrigeration device, raman detection probe, spectrometer, object table, rotating platform, wherein, the laser is used to emit probe laser;The object table is arranged in front of the laser, and the probe laser is irradiated into the substance to be measured from the incident surface;The raman detection probe is arranged on the rotating platform, the rotating platform can be rotated relative to the object table, and the raman detection probe is towards the exit surface of the substance to be measured;The rotating platform drives the raman detection probe to gradually change the receiving angle of raman light from the side of the normal of the exit surface of the substance to be measured, respectively determines the raman spectrum signal under several different angles, and based on the change gradient of raman spectrum signal under different angles, the substance to be measured is detected.

Description

Technical Field

[0001] This invention relates to the field of detection equipment, and more specifically to a laser scanning system for material detection. Background Technology

[0002] Non-destructive testing (NDT) is a method that examines and tests the surface and internal structure of various materials without damaging or affecting their performance. It utilizes the physical basis of abnormal or defective internal structures of materials and employs modern technology and equipment.

[0003] Non-destructive testing (NDT) preserves sample integrity: For items of historical, cultural, or economic value, such as artifacts, works of art, ancient books, and gemstones, any destructive testing is unacceptable. NDT can provide necessary information without altering or damaging the sample.

[0004] Compared to destructive testing, non-destructive testing is generally more economical. It not only saves the cost of repairing or replacing the object being tested, but also reduces downtime caused by testing.

[0005] Currently, the detection of gemstones and other substances is generally carried out by manual identification and spectral analysis. However, with the development of artificial technology, through the addition of doping and other methods, it has become increasingly difficult to distinguish artificial products in terms of material composition and other aspects using spectral analysis. Summary of the Invention

[0006] In view of the above-mentioned problems in the prior art, the present invention aims to provide a detection system or laser scanning system that can better perform non-destructive testing of materials.

[0007] Inventive Principles

[0008] Normally, because Raman spectroscopy is a scattering spectroscopy, the peak intensities of Raman spectra are generally isotropic, and the peak intensities measured from different angles are roughly similar. However, the inventors of this application discovered, while testing artificial and natural crystal materials, that artificial crystals, especially those mainly composed of carbon-carbon bonds, exhibit a large gradient change in their Raman spectra with angle at specific temperatures (low temperatures, below -10 degrees Celsius) (spectral gradient discontinuity), while natural crystals do not exhibit this discontinuity. Therefore, they considered applying this phenomenon to material detection, combining it with other detection methods to improve the accuracy of material detection.

[0009] Specifically, the present invention provides a laser scanning system for material detection, the system comprising:

[0010] Laser, mirror, cooling device, Raman detection probe, spectrometer, stage, rotating platform,

[0011] The laser is used to emit a detection laser; the stage is disposed in front of the laser and is used to place the substance to be tested, the substance to be tested including at least one incident surface and at least one exit surface, the detection laser irradiates the substance to be tested from the incident surface; the Raman detection probe is disposed on the rotating platform, the rotating platform is rotatable relative to the stage, and the Raman detection probe faces the exit surface of the substance to be tested;

[0012] The laser periodically emits a detection laser at a predetermined frequency; the cooling device is disposed below the substance to be tested and is used to cool it to a predetermined temperature.

[0013] The rotating platform drives the Raman detection probe to gradually change the receiving angle of the Raman light from one side of the normal to the emission surface of the substance to be tested, and measures the Raman spectral signals at several different angles. The substance to be tested is detected based on the gradient of the change of the Raman spectral signals at different angles.

[0014] In a preferred embodiment, a light-transmitting plate is further included, wherein a light-transmitting hole is provided on the light-transmitting plate, and the light-transmitting plate is positioned in front of the Raman detection probe, with the light-transmitting hole directly in front of the Raman detection probe.

[0015] In another preferred implementation, the laser scanning system performs the detection by placing the sample on a stage, adjusting the power and spot size of the laser, and aligning it with the incident surface of the sample to be tested.

[0016] Using a rotating platform, the Raman detection probe is driven to gradually change the receiving angle of the Raman light from one side of the normal to the emission surface of the substance to be tested. Raman spectral signals at several different angles are measured, and the gradient change of the Raman spectral signal is detected. It is determined whether there is a jump spectrum in the Raman spectral signal where the absolute value of the gradient exceeds a preset threshold. If a jump spectrum exists, the substance to be tested is determined to belong to the first category. If no jump spectrum exists, the substance to be tested is determined to belong to the second category. The preset threshold is 0.5, 0.72, or 0.86.

[0017] In another preferred embodiment, a signal processing device is also included, which is used to calculate the amplitude variation of the spectral peaks in the Raman spectral data.

[0018] In another preferred embodiment, the substance to be tested is a transparent or translucent crystalline substance having at least two flat surfaces.

[0019] In another preferred implementation, a focusing lens and a collimating lens are also included for focusing and collimating the laser.

[0020] In another preferred embodiment, the cooling device is used to lower the temperature of the substance to be tested to below -10 degrees Celsius. More preferably, below -20 degrees Celsius.

[0021] The present invention also provides a method for material detection using the laser scanning system described above.

[0022] The method of the present invention can be used for non-destructive testing of test substances, improving the accuracy of detection between man-made test substances and natural test substances. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the optical path of the laser scanning system of the present invention;

[0024] Figure 2 The Raman spectrum detected by the laser scanning system of the present invention is a curve showing the change of Raman spectrum with angle at -15 degrees Celsius.

[0025] Figure 3 The curve showing the change of Raman spectrum with angle at room temperature, as detected by the laser scanning system of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0027] like Figure 1 As shown, this embodiment provides a laser scanning system for material detection, including: a laser 101, a mirror 102, a Raman detection probe 103, a spectrometer 104, a stage 105, a rotating platform 106, and a cooling device 107. Preferably, it also includes a temperature sensor 108. The laser scanning system is used to detect various substances that cannot be detected by destructive testing methods. The substance to be tested is a transparent or translucent crystalline material with at least two relatively flat surfaces.

[0028] Laser 101 is used to emit Raman laser light with a wavelength of 532 or 785 nm. In this embodiment, the incident laser wavelength is 532 nm.

[0029] The stage 105 is positioned in front of the laser 101 and is used to place the substance to be tested. The substance to be tested includes, but is not limited to, diamond, crystal, etc. The substance to be tested can also be amber, glass, or other transparent or semi-permeable materials. In this embodiment, the testing of diamond is used as an example for description.

[0030] The cooling device 107 is used to pre-cool the substance to be tested. Pre-cooling can be achieved through direct or indirect cooling. Direct cooling refers to placing a TEC semiconductor cooling pad on the upper surface of the stage, with the cooling surface facing upwards. That is, the cooling device 107 takes the form of a cooling pad on the stage, which cools the substance to be tested. A temperature sensor, which can be an electronic temperature sensor or an infrared temperature sensor, is used to measure the temperature of the substance. Once the temperature reaches the measurement temperature, a Raman laser is emitted for incident light irradiation, and the Raman spectrum is detected using a Raman spectrometer. For diamond, the test temperature is set below 0 degrees Celsius, preferably below -10 degrees Celsius. After cooling, the Raman spectral gradient becomes more pronounced.

[0031] In a preferred embodiment, the light-incident surface and the light-exit surface can also be polished to make their surfaces smoother.

[0032] In another implementation, the substance to be tested is placed in a transparent container (the material of the transparent container is different from that of the substance to be tested), and cold air is introduced from the outside to cool the substance to be tested. During the measurement, the temperature of the substance to be tested is monitored in real time. If the temperature does not meet the measurement requirements, the measurement is stopped, and the cooling temperature is controlled until the measurement conditions are met, and then the measurement is resumed.

[0033] The test material 109 includes at least one relatively flat incident surface and at least one relatively flat exit surface. Raman laser light enters the test material from the incident surface. A Raman detection probe is mounted on a rotating platform 106, which is rotatable relative to the stage. The Raman detection probe faces the exit surface of the test material. For large-sized test materials, the laser can be directly incident. For small-sized test materials, a focusing lens and a light-blocking aperture are further provided in front of the test material to prevent a large amount of incident laser light from irradiating the non-incident surface.

[0034] The laser 101 periodically emits a detection laser at a predetermined frequency; the rotating platform 106 drives the Raman detection probe 103 to continuously or gradually change the receiving angle of the Raman light from one side of the normal of the emission surface of the substance to be tested 109, and measures the Raman spectral signals at several different angles respectively, and detects the substance to be tested based on the gradient of the change of the Raman spectral signals at different angles.

[0035] Based on Raman spectral signals measured at different angles, angle-spectral intensity curves are plotted, and the gradient changes at various points on the curves are calculated to determine whether there are any gradient changes in the angle-spectral intensity curves that significantly exceed reasonable fluctuations. Preferably, the spectral signals are filtered and smoothed to avoid detection errors.

[0036] The system can be equipped with a signal processing device to calculate the gradient changes of spectral peaks with angle in Raman spectral data.

[0037] In a preferred embodiment, in order to reduce unnecessary stray light entering the spectrometer and interfering with the measurement, a light-transmitting plate is further included. The light-transmitting plate is provided with a light-transmitting hole, and the light-transmitting plate is positioned in front of the Raman detection probe, directly opposite the light-transmitting hole.

[0038] The present invention also provides a method for detecting substances. The method of the present invention utilizes the above-described laser scanning system for detecting substances. The method includes: placing a sample on a stage 105, adjusting the power and spot size of the laser 101, and aligning it with the incident surface of the sample to be tested.

[0039] A refrigeration device is used to cool the substance to be tested, so that its temperature is below 0 degrees Celsius, preferably below -10 degrees Celsius. The refrigeration device is then turned off, and the temperature of the substance to be tested is monitored in real time and detected.

[0040] A rotating platform is used to gradually change the receiving angle of the Raman light from one side of the normal to the emission surface of the analyte. Raman spectral signals are measured at several different angles, and the gradient changes in the Raman spectral signals are detected. It is determined whether there is a gradient jump exceeding a preset threshold. If a jump spectrum exists, the analyte is classified as belonging to Category I (man-made substances); if no jump spectrum exists, the analyte belongs to Category II (natural substances). To ensure accuracy, other detection methods can be used in conjunction to further determine the classification of the analyte.

[0041] In another implementation, the system further includes a focusing lens and a collimating lens for focusing and collimating the laser.

[0042] In a preferred embodiment, a focusing lens is disposed in front of the Raman probe to better collect the Raman spectral signal.

[0043] like Figure 2 The figure shows the detection results using diamond as an example, with the detected Raman peak at 1332 nm. The figure also shows the Raman spectrum variation with angle at -15 degrees Celsius, detected by the laser scanning system. It can be seen from the figure that the Raman spectrum of the artificial analyte exhibits at least two distinct gradient peaks, while the natural analyte does not have these gradient peaks (valleys).

[0044] like Figure 3 The figure shows the Raman spectrum of the test substance at room temperature as a function of angle. It can be seen from the figure that no obvious gradient peaks were found in the Raman spectra of either the artificial or natural test substance.

[0045] The reason for this may be that, during the formation of artificial test substances, due to the stable and uniform conditions, the regularity of their overall structure is stronger than that of natural test substances. This makes it easier to form certain anisotropic characteristics. The anisotropic characteristics lead to changes in Raman signals at different angles. However, at normal temperatures, atomic motion is relatively active, and the anisotropic characteristics are masked by the overall spectral peaks. Under low-temperature conditions, these anisotropic characteristics are revealed, leading to the appearance of local large gradient regions.

[0046] To verify the feasibility of the method, the inventors tested 20 synthetic diamonds and 20 natural diamonds respectively. At low temperature, within a measurement angle range of 45 degrees, the synthetic diamonds all showed at least one Raman peak change with a large gradient (greater than 0.72) with the angle, while no change in the Raman peak value with the angle was found in the natural test material, proving that the method of the present invention has statistical significance.

[0047] Although the principles of the present invention have been described in detail above with reference to preferred embodiments, those skilled in the art should understand that the above embodiments are merely illustrative explanations of the implementation of the present invention and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Any obvious changes, such as equivalent transformations or simple substitutions, based on the technical solutions of the present invention without departing from the spirit and scope of the present invention fall within the protection scope of the present invention.

Claims

1. A laser scanning system for material detection, characterized in that, The system includes: Laser, mirror, cooling device, Raman detection probe, spectrometer, stage, rotating platform, The laser is used to emit a detection laser; the stage is disposed in front of the laser and is used to place the substance to be tested, the substance to be tested including at least one incident surface and at least one exit surface, the detection laser irradiates the substance to be tested from the incident surface; the Raman detection probe is disposed on the rotating platform, the rotating platform is rotatable relative to the stage, and the Raman detection probe faces the exit surface of the substance to be tested; The laser periodically emits a detection laser at a predetermined frequency; the cooling device is disposed below the substance to be tested, and the cooling device is used to reduce the temperature of the substance to be tested to below -10 degrees Celsius, and the substance to be tested is diamond; The rotating platform drives the Raman detection probe to gradually change the receiving angle of the Raman light from one side of the normal to the emission surface of the substance to be tested, and measures the Raman spectral signals at several different angles. Based on the gradient of the Raman spectral signals at different angles, the substance to be tested is detected. The laser scanning system performs the detection in the following manner: the sample to be tested is placed on the stage, the power and spot size of the laser are adjusted, and the laser is aligned with the incident surface of the sample. Using a rotating platform, the Raman detection probe is driven to gradually change the receiving angle of the Raman light from one side of the normal to the emission surface of the substance to be tested. Raman spectral signals at several different angles are measured, and the gradient change of the Raman spectral signal is detected. It is determined whether there is a jump spectrum in the Raman spectral signal where the absolute value of the gradient exceeds a preset threshold. If a jump spectrum exists, the substance to be tested is determined to be a man-made substance; if no jump spectrum exists, the substance to be tested is determined to be a natural substance.

2. The laser scanning system for material detection as described in claim 1, characterized in that, It also includes a light-transmitting plate, on which a light-transmitting hole is provided, and the light-transmitting plate is positioned in front of the Raman detection probe, directly opposite the light-transmitting hole.

3. The laser scanning system for material detection as described in claim 1, characterized in that, The preset threshold is 0.5, 0.72, or 0.

86.

4. The laser scanning system for material detection as described in claim 1, characterized in that, It also includes a signal processing device for calculating the amplitude variation of spectral peaks in Raman spectroscopy data.

5. The laser scanning system for material detection as described in claim 1, characterized in that, It also includes focusing lenses and collimating lenses, used to focus and collimate the laser.

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