Laser scanning system for substance detection

Abstract

The invention relates to the field of detection, in particular to a laser scanning system for substance detection, the system comprises a laser, a reflector, a refrigeration device, a Raman detection probe, a spectrometer, an objective table and a rotating platform, the laser is used for emitting detection laser; the objective table is arranged in front of the laser, and the detection laser irradiates and enters the to-be-detected substance from the incident plane; the Raman detection probe is arranged on the rotating platform, the rotating platform can rotate relative to the objective table, and the Raman detection probe faces the emergent surface of the substance to be detected; and the rotating platform drives the Raman detection probe to gradually change the receiving angle of Raman light from one side of the normal of the emergent surface of the to-be-detected substance, a plurality of Raman spectrum signals at different angles are respectively measured, and the to-be-detected substance is detected based on the change gradient of the Raman spectrum signals at different angles.

Description

Technical Field

[0001] The invention relates to the field of detection equipment, and in particular to a laser scanning system for material detection. Background Art

[0002] Nondestructive testing is a method of inspecting and testing the surface and internal structure of various substances by using the physical basis of abnormalities or defects in the internal structure of the material without damaging or affecting the performance of the object being tested, with the help of modern technology and equipment.

[0003] Non-destructive testing can maintain sample integrity: For some items with historical value, cultural significance or economic value, such as cultural relics, artworks, ancient books, gems, etc., any destructive testing is unacceptable. Non-destructive testing can provide necessary information without changing or damaging the sample.

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

[0005] At present, the detection of gemstones and other materials 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 through spectral spectra. Summary of the invention

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

[0007] Principle of the Invention

[0008] Normally, since Raman spectra are scattering spectra, the peak intensities of Raman spectra are often basically isotropic, and the peak intensities of Raman spectra measured from different angles are generally similar. However, when the inventors of the present application tested artificial crystals and natural crystal materials, they found that artificial crystals, especially crystals mainly composed of carbon-carbon bonds, have a certain large gradient change (spectral gradient fault) with the change of angle at a specific temperature (low temperature, below -10 degrees Celsius), while natural crystals do not have this fault. It is then considered that this phenomenon can be applied to material detection, and in combination with other detection methods, the accuracy of material detection can be improved.

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

[0010] Laser, reflector, refrigeration device, Raman detection probe, spectrometer, stage, rotating platform,

[0011] Wherein, the laser is used to emit a detection laser;

[0012] The stage is arranged in front of the laser and is used to place the substance to be tested. The substance to be tested includes at least one incident surface and at least one exit surface. The detection laser is irradiated from the incident surface to enter the substance to be tested.

[0013] The Raman detection probe is arranged on the rotating platform, the rotating platform can rotate relative to the stage, and the Raman detection probe faces the exit surface of the substance to be detected;

[0014] The laser periodically emits a detection laser at a predetermined frequency;

[0015] The refrigeration device is arranged below the substance to be tested and is used to cool it down to a predetermined temperature;

[0016] The rotating platform drives the Raman detection probe to gradually change the receiving angle of Raman light from one side of the normal line of the emission surface of the substance to be detected, respectively measure the Raman spectrum signals at several different angles, and detect the substance to be detected based on the change gradient of the Raman spectrum signals at different angles.

[0017] In a preferred implementation, it further comprises a light-transmitting plate, on which a light-transmitting hole is arranged, and the light-transmitting plate is arranged in front of the Raman detection probe, and the front of the Raman detection probe is opposite to the light-transmitting hole.

[0018] In another preferred implementation, the laser scanning system performs detection in the following manner: placing the sample on the stage, adjusting the power and spot size of the laser, and aligning it with the incident surface of the sample to be tested;

[0019] The Raman detection probe is driven by a rotating platform to gradually change the receiving angle of the Raman light from one side of the normal line of the emission surface of the substance to be tested, and the Raman spectrum signals at several different angles are measured respectively. The gradient change of the Raman spectrum signal is detected, and it is determined whether the Raman spectrum signal has a jump spectrum whose absolute value of the gradient exceeds a preset threshold. If the jump spectrum exists, the substance to be tested is determined to belong to the first category. If the jump spectrum does not exist, the substance to be tested is determined to belong to the second category. The preset threshold is 0.5, 0.72 or 0.86.

[0020] In another preferred implementation, it further comprises a signal processing device, wherein the signal processing device is used to calculate the amplitude change of the spectral peak of the Raman spectral data.

[0021] In another preferred implementation, the substance to be tested is a transparent or translucent crystalline substance having at least two flat surfaces.

[0022] In another preferred implementation, a focusing lens and a collimating lens are further included to focus and collimate the laser.

[0023] In another preferred implementation, the refrigeration device is used to reduce the temperature of the substance to be tested to below -10 degrees Celsius. More preferably, below -20 degrees Celsius.

[0024] The present invention also provides a method for material detection using the laser scanning system described in the claims.

[0025] The method of the present invention can be used to perform nondestructive testing on the substance to be tested, thereby improving the accuracy of testing between artificial and natural substances to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the optical path of the laser scanning system of the present invention;

[0027] Figure 2 The Raman spectrum detected by the laser scanning system of the present invention is a curve of the Raman spectrum changing with angle at -15 degrees Celsius;

[0028] Figure 3 The Raman spectrum detected by the laser scanning system of the present invention is a curve showing the variation of the Raman spectrum with angle at room temperature. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0030] like Figure 1 As shown, this embodiment provides a laser scanning system for material detection, including: a laser 101, a reflector 102, a Raman detection probe 103, a spectrometer 104, a stage 105, a rotating platform 106, and a refrigeration device 107. Preferably, a temperature sensor 108 is also included. The laser scanning system is used to detect various substances to be tested that cannot be detected by destructive testing methods. The substance to be tested is a transparent or translucent crystalline substance with at least two relatively flat surfaces.

[0031] The laser 101 is used to emit Raman laser light, and the wavelength of the Raman laser light is 532 nm or 785 nm. In this embodiment, the wavelength of the incident laser light is 532 nm.

[0032] The stage 105 is arranged 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, etc. transparent or semi-permeable membrane materials. This embodiment is described by taking the detection of diamond as an example.

[0033] The refrigeration device 107 is used to pre-cool the substance to be tested. The pre-cooling can be done by direct refrigeration or indirect refrigeration. Direct refrigeration refers to setting a TEC semiconductor refrigeration sheet on the upper surface of the stage, with the refrigeration surface facing upward. That is, the refrigeration device 107 takes the form of a refrigeration pad on the stage, and refrigerates the substance to be tested through the refrigeration pad. The temperature of the substance to be tested is measured by a temperature sensor, which can be an electronic temperature sensor or an infrared temperature sensor. When the temperature reaches the measurement temperature, a Raman laser is emitted for incident light irradiation, and a Raman spectrometer is used to detect the Raman spectrum. For diamond, the temperature to be tested is set below 0 degrees Celsius, preferably below -10 degrees Celsius. After cooling, the Raman spectrum gradient is relatively more obvious.

[0034] In a preferred implementation, the light incident surface and the light emitting surface may be polished to make their surfaces smoother.

[0035] 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 the substance to be tested is cooled by cold air input from the outside. When measuring, the temperature of the substance to be tested is detected in real time. Once the temperature does not meet the measurement temperature, the detection is stopped, and the cooling temperature is controlled until the measurement conditions are met, and then the detection is continued.

[0036] The substance to be tested 109 includes at least one relatively flat incident surface and at least one relatively flat exit surface, and the Raman laser is irradiated from the incident surface to the substance to be tested; the Raman detection probe is arranged on a rotating platform, and the rotating platform 106 can rotate relative to the stage, and the Raman detection probe faces the exit surface of the substance to be tested. For large-sized substances to be tested, the laser can be directly incident, and for small-sized substances to be tested, a focusing lens and a light-shielding aperture are further arranged in front of the substance to be tested to prevent a large amount of incident laser from irradiating on the non-incident surface.

[0037] 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 line of the emission surface of the substance to be detected 109, and respectively measures the Raman spectrum signals at several different angles, and detects the substance to be detected based on the change gradient of the Raman spectrum signals at different angles.

[0038] Based on the Raman spectral signals measured at different angles, an angle-spectral intensity curve is drawn, the gradient changes at each point of the curve are calculated, and it is determined whether there is a gradient change in the angle-spectral intensity curve that obviously exceeds the reasonable fluctuation. Preferably, the spectral signal is filtered and smoothed to avoid detection errors.

[0039] A signal processing device may be provided in the system, and the signal processing device is used to calculate the gradient change of the spectral peak of the Raman spectral data with the angle.

[0040] In a preferred implementation, in order to reduce unnecessary stray light from entering the spectrometer and interfering with the measurement, a light-transmitting plate is further included, on which a light-transmitting hole is arranged. The light-transmitting plate is arranged in front of the Raman detection probe, and the front of the Raman detection probe is directly opposite to the light-transmitting hole.

[0041] The present invention also provides a method for detecting a substance. The method of the present invention uses the above-mentioned laser scanning system to detect a substance. The method comprises:

[0042] Place the sample on the stage 105, adjust the power and spot size of the laser 101, and align it with the incident surface of the sample to be tested;

[0043] 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. The refrigeration device is turned off, the temperature of the substance to be tested is detected in real time, and the test is performed.

[0044] The rotating platform is used to drive the Raman detection probe to gradually change the receiving angle of the Raman light from one side of the normal line of the emission surface of the substance to be tested, and the Raman spectrum signals at several different angles are measured respectively. The gradient change of the Raman spectrum signal is detected, and it is determined whether the Raman spectrum signal has a jump spectrum whose gradient exceeds a preset threshold. If there is a jump spectrum, the substance to be tested is determined to belong to the first category (artificial substance), and if there is no jump spectrum, the substance to be tested is determined to belong to the second category (natural). In order to ensure the accuracy of the detection, other detection methods can also be used to jointly determine the classification of the substance to be tested.

[0045] In another implementation, the system further includes a focusing lens and a collimating lens for focusing and collimating the laser.

[0046] In a preferred implementation, a focusing lens is arranged in front of the Raman probe to better collect Raman spectrum signals.

[0047] like Figure 2 The test results are shown in the example of diamond, and the detected Raman spectrum peak is 1332nm. As shown in the figure, the Raman spectrum detected by the laser scanning system at -15 degrees Celsius changes with the angle. It can be seen from the figure that the Raman spectrum of the artificial test substance has at least two obvious gradient peaks, while the natural test substance has no such gradient peaks (valleys).

[0048] like Figure 3The figure shows the curve of the Raman spectrum variation with angle obtained by detecting the test substance at room temperature. It can be seen from the figure that no obvious gradient peak is found in the Raman spectra of the artificial test substance and the natural test substance.

[0049] The reason for the analysis may be that during the formation process of artificial test substances, due to stable and uniform conditions, the regularity of their overall structure is stronger than that of natural test substances, and it is easy to form certain anisotropic properties in them. The anisotropic properties lead to changes in Raman signals at different angles. However, at normal temperatures, atomic motion is relatively active, and its anisotropic properties are masked by the overall spectral peak. Under low temperature conditions, this anisotropic property is revealed, which in turn leads to the appearance of local large gradient areas.

[0050] In order to verify the feasibility of the scheme, the inventors tested 20 artificial diamonds and 20 natural diamonds respectively. Under low temperature and within a measuring angle range of 45 degrees, the artificial diamonds showed at least one Raman peak change with a large gradient (greater than 0.72) with the angle, while the natural test substances did not show a change in the Raman peak value with a large gradient with the angle, which proves that the method of the present invention is statistically significant.

[0051] Although the principles of the present invention are described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are merely explanations of the exemplary implementations of the present invention, and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute limitations on the scope of the present invention, and any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution 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 comprises: Laser, reflector, refrigeration device, Raman detection probe, spectrometer, stage, rotating platform, Wherein, the laser is used to emit a detection laser; The stage is arranged in front of the laser and is used to place the substance to be tested. The substance to be tested includes at least one incident surface and at least one exit surface. The detection laser is irradiated from the incident surface to enter the substance to be tested. The Raman detection probe is arranged on the rotating platform, the rotating platform can rotate relative to the stage, and the Raman detection probe faces the exit surface of the substance to be detected; The laser periodically emits a detection laser at a predetermined frequency; The refrigeration device is arranged below the substance to be tested and is used to cool it down to a predetermined temperature; The rotating platform drives the Raman detection probe to gradually change the receiving angle of Raman light from one side of the normal line of the emission surface of the substance to be detected, respectively measure the Raman spectrum signals at several different angles, and detect the substance to be detected based on the change gradient of the Raman spectrum signals at different angles.

2. The laser scanning system for material detection according to claim 1, characterized in that: It also includes a light-through plate, on which a light-through hole is arranged. The light-through plate is arranged in front of the Raman detection probe and faces the light-through hole.

3. The laser scanning system for material detection according to claim 1, characterized in that: The laser scanning system performs 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 it is aligned with the incident surface of the sample to be tested; The Raman detection probe is driven by a rotating platform to gradually change the receiving angle of the Raman light from one side of the normal line of the emission surface of the substance to be tested, and the Raman spectrum signals at several different angles are measured respectively. The gradient change of the Raman spectrum signal is detected, and it is determined whether the Raman spectrum signal has a jump spectrum whose absolute value of the gradient exceeds a preset threshold. If the jump spectrum exists, the substance to be tested is determined to belong to the first category. If the jump spectrum does not exist, the substance to be tested is determined to belong to the second category. The preset threshold is 0.5, 0.72 or 0.

86.

4. The laser scanning system for material detection according to claim 1, characterized in that: The system also includes a signal processing device for calculating the amplitude change of the spectrum peak of the Raman spectrum data.

5. The laser scanning system for material detection according to claim 1, characterized in that: The substance to be tested is a transparent or translucent crystalline substance having at least two flat surfaces.

6. The laser scanning system for material detection according to claim 1, characterized in that: It also includes a focusing lens and a collimating lens for focusing and collimating the laser.

7. The laser scanning system for material detection according to claim 1, characterized in that: The refrigeration 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.

8. A method for detecting a substance using the laser scanning system according to any one of claims 1 to 7.

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