Spatial displacement laser spectrum detection method for wood identification

Abstract

The invention relates to a spatial displacement laser spectrum detection method for wood identification. The method comprises four steps of instrument initialization, surface layer laser spectrum detection, base layer spatial displacement spectrum detection and comprehensive spectrum analysis of a detection target. The beneficial effects are that the same infrared laser is used as a laser pumping source of the infrared photonic crystal fiber and an infrared laser source for spatial displacement spectrum detection. The infrared absorption spectrum of the target surface layer and the infrared laser Raman and fluorescence spectrum of the base layer in the same wave number section can be detected at the same time, so that the material identification of the surface layer and the base layer is realized at the same time. Meanwhile, the wave number resolution of the infrared spectrum Fourier transform spectrum module is high, so that the high-resolution infrared laser Raman and fluorescence spectrum of the base layer can be obtained, and fine spectrum data is provided for base layer material identification. And the requirement for on-site rapid detection of wood products is met.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detection, and in particular to a spatial displacement laser spectrum detection method for wood identification. Background Art

[0002] In the production and sale of wooden furniture, the cost and price of high-end rosewood are relatively high, making it difficult for ordinary consumers and market regulators to visually distinguish inferior wooden furniture from high-quality products. To meet the needs of on-site supervision, rapid and accurate identification equipment is needed to distinguish the solid wood types of furniture and other wooden products.

[0003] Solid wood contains moisture, sugars, resins, and other substances, specifically the polysaccharides cellulose and hemicellulose, the aromatic organic lignin, and some phenols and ash, including iron and silicon, resulting in a complex composition. Solid wood processing involves the following steps: first, sawing (cutting the log into pieces); then, stabilization processes such as drying and moisture content control; then, material preparation through selection and planing and splicing; then, machining; then, assembly, sanding, coloring, painting, and finally, the finished product.

[0004] Fourier transform infrared spectrometers (FTIR) are commonly used in laboratories. Their diffuse reflectance accessories use a drawer-style sampling system for testing small wood samples, which can provide good identification results. However, when inspecting furniture on-site, rapid testing equipment is needed for in-situ testing of large objects such as tabletops. Due to the extremely rich variety of high-value redwoods and the surface processing of solid wood processing mentioned above, in-situ non-destructive testing of solid wood on and below the surface is extremely difficult. How to quickly and non-destructively test solid wood products, provide information on the surface, base layer, and components of wood products, and identify the species, is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a spatial displacement laser spectrum detection method for wood identification in order to solve the problems in the prior art.

[0006] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions: A spatial displacement laser spectrum detection method for wood identification is provided, which uses a wood product spatial displacement laser spectrum detector for detection. The wood product spatial displacement laser spectrum detector includes: Surface infrared diffuse reflectance spectrum detection optical path: The infrared laser is transmitted through the optical fiber and passes through a 45-degree reflector into the interferometer. The modulated light beam irradiates the sample surface through the diffuse reflectance accessory, and its reflected light is finally received by the detector to realize surface composition analysis and obtain molecular vibration information of the surface of wood products; Substrate infrared laser spatial displacement scattering detection optical path: After beam expansion and collimation, the infrared laser forms a ring beam through an aconic lens. After being reflected by a 45-degree dichroic mirror, it irradiates the sample vertically, forming a focusing ring on the surface. The substrate scattered light returns from the center of the ring, transmits in the reverse direction through the same optical path, and is finally received by the detector to achieve deep structure detection. The deep scattering signal is excited by the ring laser to achieve sub-surface structure detection; The test involves the following steps: Step S1: Sample placement and optical path calibration, with the detector window closely fitting the sample surface; Step S2, detecting the light path by using the surface infrared diffuse reflectance spectrum to obtain the infrared broadband diffuse reflectance of the wood product surface; Step S3, obtaining high-resolution infrared laser Raman and fluorescence spectra of the wood product substrate through the substrate infrared laser spatial displacement scattering detection light path; Step S4, performing spectral analysis on the infrared broadband diffuse reflectance of the wood product surface layer and the high-resolution infrared laser Raman and fluorescence spectra of the wood product base layer obtained in step S3 to obtain the molecular composition and content of the surface layer and base layer.

[0007] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions: As a preferred technical solution of the present invention: in the surface infrared diffuse reflectance spectrum detection light path, The monochromatic infrared continuous laser emitted by the infrared laser along the main optical axis passes through the infrared photonic crystal fiber, passes through the infrared perforated reflector installed at a 45-degree angle to the main optical axis, enters the entrance hole, and then enters the Michelson interferometer assembly. It is output along the lower outlet while scanning, enters the diffuse reflection accessory through the lower left channel, and is reflected. It is emitted through the window to the surface of the wood product in close contact with the window. The infrared light diffusely reflected by the surface is reflected and received by the lower detector through the lower right channel. In the base layer infrared laser spatial displacement scattering detection optical path, the monochromatic infrared continuous laser emitted by the infrared laser along the secondary optical axis is expanded and collimated by the infrared beam expander collimator and then emitted to the upper infrared cone lens to form a ring-shaped infrared laser of a certain diameter. The ring-shaped infrared laser is then reflected by the infrared dichroic plate installed at a 45-degree angle to the secondary optical axis and turned to the vertical optical axis. The ring is then formed on the surface of the wood product by the lower infrared cone lens, and some scattered photons of the base layer are excited to pass through the center of the ring, enter the lower infrared cone lens in the opposite direction along the vertical optical axis, and then transmit through the infrared dichroic plate, and then pass through the infrared converging mirror. After reflection and convergence by the infrared perforated reflector, the laser enters the Fourier transform infrared spectroscopy module, first enters the entrance hole, and then enters the Michelson interferometer assembly. The laser is output along the upper outlet while scanning and is received by the upper detector through the upper channel.

[0008] As a preferred technical solution of the present invention: Step S2 specifically includes the following steps: Step S201: Broad-spectrum laser generation and optical path transmission: The infrared laser emits monochromatic continuous laser light, which is then broadened to a broad-spectrum infrared laser light through a high-order nonlinear effect after passing through an infrared photonic crystal fiber. The broad-spectrum laser light then passes through a 45° infrared perforated reflector and enters the Michelson interferometer assembly. The moving mirror scans the beam to generate a time-domain interference signal. The modulated beam is then output from the lower exit and enters the diffuse reflection accessory through the lower left channel. Step S202: Baseline spectrum acquisition: the excitation light illuminates the standard gold-plated plate, the diffusely reflected light returns through the lower right channel and is received by the lower detector, and the absolute reflectance spectrum data of the gold-plated plate is recorded as the baseline spectrum; Step S203, collecting the surface reflectance spectrum data of the wood product to be tested; Step S204 , spectral data processing and correction, divides the surface reflectance spectrum data of the wood product to be tested obtained in step S203 by the diffuse reflectance spectrum data of the standard gold-plated plate obtained in step S202 to obtain the infrared broadband diffuse reflectance distribution of the wood product surface.

[0009] As a preferred technical solution of the present invention: Step S3 specifically includes the following steps: Step S301, the infrared laser emits monochromatic continuous laser light; Step S302: An annular beam is generated and focused. The laser is adjusted to parallel light by an infrared beam expander collimator and then converted into an annular beam by an upper infrared axicon. The annular beam is reflected by a 45° infrared dichroic filter and turned perpendicular to the optical axis. The lower infrared axicon focuses the annular light on the surface of the wood product, forming an adjustable focusing ring. Step S303: The linear motor drives the upper axicon to translate along the secondary optical axis, dynamically adjusting the distance between the upper and lower axicon lenses, thereby changing the focus ring diameter; Step S304: base layer signal excitation and collection. The edge photons of the ring laser penetrate the surface layer and excite the base layer. The base layer scattered photons return pure from the ring center and transmit in the reverse direction along the vertical optical path for signal extraction. Step S305: interference modulation and spectrum analysis: the scattered light enters the Michelson interferometer, and the moving mirror scans to generate a time domain interference pattern, which is converted into high-resolution Raman spectrum data and fluorescence spectrum data through Fourier transform.

[0010] As a preferred technical solution of the present invention: Step S4 includes: performing spectral analysis on the infrared broadband diffuse reflectance of the wood product surface obtained in Step S2 and the high-resolution infrared laser Raman and fluorescence spectra of the wood product base obtained in Step S3, so as to obtain the molecular composition and content of the surface and base layers, and perform pattern recognition to determine the type of the surface coating and base layer material. Compared to existing technologies, the spatially shifted laser spectroscopy detection method for wood identification presented in this invention offers the following advantages: It utilizes a single infrared laser as both the laser pump source for the infrared photonic crystal fiber and the infrared laser source for spatially shifted spectroscopy detection. This method can simultaneously detect the infrared absorption spectrum of the target surface layer and the infrared laser Raman and fluorescence spectra of the base layer within the same wavenumber band, thereby enabling simultaneous material identification of both the surface and base layers. Furthermore, due to the high wavenumber resolution of the infrared Fourier transform spectroscopy module, high-resolution infrared laser Raman and fluorescence spectra of the base layer can be obtained, providing detailed spectral data for base material identification. This method meets the requirements for rapid on-site detection of wood products. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic structural diagram of a spatial displacement laser spectrum detector used in the spatial displacement laser spectrum detection method for wood identification of the present invention; In the accompanying drawings, there are a lower infrared axicon 1; a linear motor 2; a secondary optical axis 3; an infrared beam expander and collimator 4; an infrared laser 5; a primary optical axis 6; a lithium battery 7; a switch 8; a power manager 9; an infrared photonic crystal fiber 10; an upper infrared axicon 11; an infrared dichroic plate 12; an infrared perforated reflector 13; a vertical optical axis 14; an entrance hole 15; a Fourier transform infrared spectroscopy module 16; a controller 17; an upper outlet 18; a lower outlet 19; an upper channel 20; an upper detector 21; a receiving module 22; a lower detector 23; a lower right channel 24; a diffuse reflectance accessory 25; a lower left channel 26; a surface layer 27; a handle 28; a focusing ring 29; a base layer 30; an instrument body 31; a power supply line 32; a power supply module 33; a Michelson interferometer assembly 34; an infrared converging mirror 35; and a window 36. DETAILED DESCRIPTION

[0012] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0013] like Figure 1 As shown in FIG, a spatial displacement laser spectrum detection method for wood identification of the present invention is implemented based on a spatial displacement laser spectrum detector. The detector is composed of an instrument body 31, a power supply module 33, and a handle 28.

[0014] The instrument body 31 is composed of an upper infrared conical lens 11, a lower infrared conical lens 1, a linear motor 2, an infrared beam expander collimator 4, an infrared laser 5, an infrared photonic crystal fiber 10, an infrared dichroic plate 12, an infrared perforated reflector 13, an infrared converging mirror 35, a Fourier transform infrared spectroscopy module 16, a controller 17, a receiving module 22, and a diffuse reflection accessory 25.

[0015] The power supply module 33, consisting of a switch 8, a lithium battery 7, and a power management unit 9, is used to power the linear motor 2, infrared laser 5, Fourier transform infrared spectroscopy module 16, controller 17, and receiving module 22 within the instrument body 31 via a power line 32. When the power supply module is connected to AC220V mains power, the mains power is converted to DC power by the power management unit 9, which charges the lithium battery 7 and also powers the instrument body 31. When the power supply module 33 is disconnected from the mains power, the lithium battery 7 is used to power the instrument body 31. The switch 8 is used to turn the power supply module 33 on and off.

[0016] The Fourier transform infrared spectroscopy module 16 includes an inlet 15 , a Michelson interferometer assembly 34 , an upper outlet 18 and a lower outlet 19 .

[0017] The receiving module 22 includes an upper detector 21 and a lower detector 23 with the same performance parameters.

[0018] The spatial displacement laser spectrometer has two detection optical paths: one for surface infrared diffuse reflectance spectroscopy and one for base-layer infrared laser spatial displacement scattering. The surface infrared diffuse reflectance spectroscopy detection path consists of an infrared laser 5, an infrared photonic crystal fiber 10, an infrared perforated reflector 13, an inlet 15, a Michelson interferometer assembly 34, an upper outlet 18, an upper channel 20, and an upper detector 21.

[0019] The components of the basic infrared laser spatial displacement scattering detection optical path are infrared laser 5, infrared beam expansion collimator 4, upper infrared conical lens 11, infrared dichroic plate 12, lower infrared conical lens 1, infrared converging mirror 35, infrared perforated reflector 13, entrance hole 15, Michelson interferometer assembly 34, lower outlet 19, lower left channel 26, diffuse reflection accessory 25, lower right channel 24, and lower detector 23.

[0020] The infrared laser 5 emits a monochromatic infrared continuous laser, which has a wavelength of 2200nm and a power of 300mW in this embodiment, and is then divided into two paths: The light is emitted along the main optical axis 6 and passes through the infrared photonic crystal fiber 10. Due to a variety of high-order nonlinear optical effects, the wavelength is broadened to a wide-spectrum supercontinuum infrared laser. In this embodiment, the wavelength range is 2222nm to 25000nm (corresponding to a wave number range of 400 to 4500cm -1 ), passes through the infrared perforated reflector 13 installed at a 45-degree angle to the main optical axis 6, enters the entrance hole 15, then enters the Michelson interferometer assembly 34, is output along the lower outlet 19 while scanning, enters the diffuse reflection accessory 25 through the lower left channel 26, is refracted, and is emitted through the window 36 to the surface layer 27 of the wood product in close contact with the window 36. After being refracted, the infrared light diffusely reflected by the surface layer 27 is received by the lower detector 23 through the lower right channel 24, thereby realizing the infrared diffuse reflection spectrum detection mode of the surface layer 27; The other path is emitted along the secondary optical axis 3, expanded and collimated by the infrared beam expander and collimator 4, and then emitted to the upward infrared cone lens 11, forming a ring-shaped infrared laser of a certain diameter. It is then reflected by the infrared dichroic plate 12 (this embodiment reflects 2200nm and transmits 2222 to 25000nm) installed at a 45-degree angle to the secondary optical axis 3, and then turned to the vertical optical axis 14. It then passes through the lower infrared cone lens 1 to form a focusing ring 29 on the surface 27 of the wood product. Some of the infrared laser photons on the ring can penetrate the surface layer 27 and enter the base layer 30, and there will be absorption, reflection and scattering effects. When the upper infrared conical lens 11 moves left and right along the secondary optical axis 3, the combination of the upper and lower infrared conical lenses 11 and 1 will produce focusing rings 29 of different diameters, thereby exciting some scattered photons at different depths of the base layer 30 to pass through the center of the ring, enter the lower infrared conical lens 1 in the opposite direction along the vertical optical axis 14, and then transmit through the infrared dichroic plate 12, and then pass through the infrared converging mirror 35. After reflection and convergence by the infrared perforated reflector 13, they enter the entrance hole 15, and then enter the Michelson interferometer assembly 34. While scanning, they are output from the upper outlet 18 and received by the upper detector 21' through the upper channel 20, thereby realizing the infrared laser spatial displacement scattering detection mode of the base layer 30.

[0021] The linear motor 2 can control the upper infrared conical lens 11 to translate left and right along the secondary optical axis 3 , thereby adjusting the distance between the upper infrared conical lens 11 and the lower infrared conical lens 1 and changing the diameter of the focusing ring 29 .

[0022] The controller 17 is used to start the infrared laser 5, the Fourier transform infrared spectroscopy module 16, the receiving module 22, and set the wave number scanning range of the Michelson interferometer component 34 (400 to 4500 cm in this embodiment). -1 ) and scanning step length (0.8 cm in this embodiment -1 ), controls the output port selection of the Michelson interferometer assembly 34, controls the receiving module 22 to select the upper and lower detectors, and receives the spectral data output by the receiving module 22 for storage and analysis. The controller 17 is also used to issue instructions to the linear motor 2, thereby controlling the scanning step size and starting and ending positions of the upper infrared axicon 11 along the secondary optical axis 3.

[0023] During on-site inspection, the operator lifts the handle 28 to press the window 36 of the diffuse reflection accessory 25 against the surface 27 of the wood product being inspected, facilitating quick on-site inspection.

[0024] The spatial displacement laser spectrum detection method for wood identification proposed by the present invention comprises the following steps: S1, instrument initialization: During on-site testing, the instrument can be powered in one of two modes: AC or DC. If AC power is selected, the instrument's power supply module 33 is connected to the AC 220V mains electricity, which is converted to DC power by the power manager 9 to charge the lithium battery 7 and also power the instrument body 31. If DC power is selected, the power supply module 33 is disconnected from the mains electricity, and the lithium battery 7 is used to power the instrument body 31. During on-site testing, the operator turns on the switch 8, and the power supply module 33 supplies power via the power line 32 to the linear motor 2, infrared laser 5, Fourier transform infrared spectroscopy module 16, controller 17, and receiving module 22 within the instrument body 31.

[0025] S2, surface laser spectroscopy detection: During on-site testing, the operator lifts handle 28, pressing window 36 of diffuse reflectance accessory 25 against a standard gold-plated plate. Controller 17 activates infrared laser 5, Fourier transform infrared spectroscopy module 16, and receiver module 22, sets the wavenumber scanning range and scanning step size of Michelson interferometer assembly 34, selects lower output port 19 for Michelson interferometer assembly 34, and controls receiver module 22 to select lower detector 23, entering surface laser spectrum detection mode. At this time, the monochromatic infrared continuous laser light emitted by the infrared laser 5 along the main optical axis 6 passes through the infrared photonic crystal fiber 10, and is broadened into an infrared broadband laser light due to the high-order nonlinear effect. The infrared continuous laser light passes through the infrared perforated reflector 13 installed at a 45-degree angle to the main optical axis 6, enters the entrance hole 15, and then enters the Michelson interferometer assembly 34. The infrared light is output along the lower outlet 19 while scanning, enters the diffuse reflection accessory 25 through the lower left channel 26, is refracted, and is emitted through the window 36 to the standard gold-plated plate in close contact with the window 36. The infrared light diffusely reflected by the standard gold-plated plate is refracted and then received by the lower detector 23 through the lower right channel 24. The controller 17 receives and stores the diffuse reflection spectrum data of the standard gold-plated plate. The standard gold-plated plate is removed, and the operator lifts the handle 28 to press the window 36 of the diffuse reflection accessory 25 against the surface 27 of the wood product to be tested. After the same detection process as the standard gold-plated plate, the controller 17 receives the diffuse reflection spectrum data of the wood product surface 27 and stores it. It then divides it with the diffuse reflection spectrum data of the standard gold-plated plate to obtain the infrared wide-spectrum diffuse reflectance distribution of the wood product surface 27.

[0026] S3, base layer spatial displacement spectrum detection: Another path of infrared laser 5 is emitted along the secondary optical axis 3. After expansion and collimation by infrared beam expander and collimator 4, it is directed toward upper infrared conical lens 11, forming a ring of infrared laser light with a predetermined diameter. This light is then reflected by infrared dichroic filter 12, mounted at a 45-degree angle to the secondary optical axis 3, and then directed toward perpendicular optical axis 14. It then passes through lower infrared conical lens 1, forming a focusing ring 29 on the surface 27 of the wood product. Controller 17 sends commands to linear motor 2, controlling the scanning step size and starting and ending positions of upper infrared conical lens 11 along the secondary optical axis 3. Under control of linear motor 2, upper infrared conical lens 11 translates left and right along the secondary optical axis 3, thereby adjusting the distance between upper infrared conical lens 11 and lower infrared conical lens 1 and changing the diameter of focusing ring 29. Some of the infrared laser photons on the ring can penetrate the surface layer 27 and enter the base layer 30, which will have absorption, reflection and scattering effects. The focusing rings 29 of different diameters can excite some scattered photons at different depths of the base layer 30 to pass through the center of the ring, and enter the lower infrared conical lens 1 in the opposite direction along the vertical optical axis, and then transmit through the infrared dichroic plate 12, and then pass through the infrared converging mirror 35. After reflection and convergence by the infrared perforated reflector 13, it enters the entrance hole 15, and then enters the Michelson interferometer assembly 34. It is output from the upper outlet 18 while scanning, and is received by the upper detector 21 through the upper channel 20. The controller 17 receives the high-resolution infrared laser Raman and fluorescence spectrum data of the wood product base layer 30 for storage, thereby realizing the infrared laser spatial displacement scattering detection mode of the base layer 30.

[0027] S4, comprehensive spectrum analysis of detection targets: By performing spectral analysis on the infrared broadband diffuse reflectance of the wood product surface layer 27 obtained in step S2 and the high-resolution infrared laser Raman and fluorescence spectra of the wood product base layer 30 obtained in step S3, the molecular composition and content of the surface layer 27 and the base layer 30 can be obtained, and pattern recognition can be performed to determine the type of material of the surface layer 27 coating and the base layer 30.

[0028] The above-mentioned specific implementation methods are used to illustrate the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the scope of protection of the claims shall fall within the scope of protection of the present invention.

Claims

1. A spatial displacement laser spectroscopy detection method for wood identification, characterized by: The detection is performed using a wood product spatial displacement laser spectrum detector, which includes: Surface infrared diffuse reflectance spectrum detection optical path: The infrared laser is transmitted through the optical fiber and passes through a 45-degree reflector into the interferometer. The modulated light beam irradiates the sample surface through the diffuse reflectance accessory, and its reflected light is finally received by the detector to realize surface composition analysis and obtain molecular vibration information of the surface of wood products; Substrate infrared laser spatial displacement scattering detection optical path: After beam expansion and collimation, the infrared laser forms a ring beam through an aconic lens. After being reflected by a 45-degree dichroic mirror, it irradiates the sample vertically, forming a focusing ring on the surface. The substrate scattered light returns from the center of the ring, transmits in the reverse direction through the same optical path, and is finally received by the detector to achieve deep structure detection. The deep scattering signal is excited by the ring laser to achieve sub-surface structure detection; The test involves the following steps: Step S1: Sample placement and optical path calibration, with the detector window closely fitting the sample surface; Step S2, detecting the light path by using the surface infrared diffuse reflectance spectrum to obtain the infrared broadband diffuse reflectance of the wood product surface; Step S3, obtaining high-resolution infrared laser Raman and fluorescence spectra of the wood product substrate through the substrate infrared laser spatial displacement scattering detection light path; Step S4, performing spectral analysis on the infrared broadband diffuse reflectance of the wood product surface layer and the high-resolution infrared laser Raman and fluorescence spectra of the wood product base layer obtained in step S3 to obtain the molecular composition and content of the surface layer and base layer.

2. The spatial displacement laser spectrum detection method for wood identification according to claim 1, characterized in that: In the surface infrared diffuse reflectance spectrum detection light path, The monochromatic infrared continuous laser emitted by the infrared laser along the main optical axis passes through the infrared photonic crystal fiber, passes through the infrared perforated reflector installed at a 45-degree angle to the main optical axis, enters the entrance hole, and then enters the Michelson interferometer assembly. It is output along the lower outlet while scanning, enters the diffuse reflection accessory through the lower left channel, and is reflected. It is emitted through the window to the surface of the wood product in close contact with the window. The infrared light diffusely reflected by the surface is reflected and received by the lower detector through the lower right channel. In the base layer infrared laser spatial displacement scattering detection optical path, the monochromatic infrared continuous laser emitted by the infrared laser along the secondary optical axis is expanded and collimated by the infrared beam expander collimator and then emitted to the upper infrared cone lens to form a ring-shaped infrared laser of a certain diameter. The ring-shaped infrared laser is then reflected by the infrared dichroic plate installed at a 45-degree angle to the secondary optical axis and turned to the vertical optical axis. The ring is then formed on the surface of the wood product by the lower infrared cone lens, and some scattered photons of the base layer are excited to pass through the center of the ring, enter the lower infrared cone lens in the opposite direction along the vertical optical axis, and then transmit through the infrared dichroic plate, and then pass through the infrared converging mirror. After reflection and convergence by the infrared perforated reflector, the laser enters the Fourier transform infrared spectroscopy module, first enters the entrance hole, and then enters the Michelson interferometer assembly. The laser is output along the upper outlet while scanning and is received by the upper detector through the upper channel.

3. The spatial displacement laser spectrum detection method for wood identification according to claim 2, characterized in that: The step S2 specifically includes the following steps: Step S201: Broad-spectrum laser generation and optical path transmission: The infrared laser emits monochromatic continuous laser light, which is then broadened to a broad-spectrum infrared laser light through a high-order nonlinear effect after passing through an infrared photonic crystal fiber. The broad-spectrum laser light then passes through a 45° infrared perforated reflector and enters the Michelson interferometer assembly. The moving mirror scans the beam to generate a time-domain interference signal. The modulated beam is then output from the lower exit and enters the diffuse reflection accessory through the lower left channel. Step S202: Baseline spectrum acquisition: the excitation light illuminates the standard gold-plated plate, the diffusely reflected light returns through the lower right channel and is received by the lower detector, and the absolute reflectance spectrum data of the gold-plated plate is recorded as the baseline spectrum; Step S203, collecting the surface reflectance spectrum data of the wood product to be tested; Step S204 , spectral data processing and correction, divides the surface reflectance spectrum data of the wood product to be tested obtained in step S203 by the diffuse reflectance spectrum data of the standard gold-plated plate obtained in step S202 to obtain the infrared broadband diffuse reflectance distribution of the wood product surface.

4. The spatial displacement laser spectrum detection method for wood identification according to claim 2, characterized in that: The step S3 specifically includes the following steps: Step S301, the infrared laser emits monochromatic continuous laser light; Step S302: An annular beam is generated and focused. The laser is adjusted to parallel light by an infrared beam expander collimator and then converted into an annular beam by an upper infrared axicon. The annular beam is reflected by a 45° infrared dichroic filter and turned perpendicular to the optical axis. The lower infrared axicon focuses the annular light on the surface of the wood product, forming an adjustable focusing ring. Step S303: The linear motor drives the upper axicon to translate along the secondary optical axis, dynamically adjusting the distance between the upper and lower axicon lenses, thereby changing the focus ring diameter; Step S304: base layer signal excitation and collection. The edge photons of the ring laser penetrate the surface layer and excite the base layer. The base layer scattered photons return pure from the ring center and transmit in the reverse direction along the vertical optical path for signal extraction. Step S305: interference modulation and spectrum analysis: the scattered light enters the Michelson interferometer, and the moving mirror scans to generate a time domain interference pattern, which is converted into high-resolution Raman spectrum data and fluorescence spectrum data through Fourier transform.

5. The spatial displacement laser spectrum detection method for wood identification according to claim 1, characterized in that: The step S4 includes: performing spectral analysis on the infrared broadband diffuse reflectance of the wood product surface obtained in step S2 and the high-resolution infrared laser Raman and fluorescence spectra of the wood product base layer obtained in step S3 to obtain the molecular composition and content of the surface layer and the base layer, and performing pattern recognition to determine the type of the surface coating and the base layer material.

Images