Hyperspectral imaging detection device optimized for plane sample and light path folding method thereof

Abstract

The invention discloses a hyperspectral imaging detection device for optimizing a plane sample and a light path folding method thereof, and belongs to the technical field of hyperspectral imaging.A black box structure is formed by a box bottom and a box cover and used for blocking external light and stray light, it is ensured that only diffuse reflection light of a sample body enters the device after passing through a slit, and the light path folding effect is achieved; according to the invention, the light path between the sample and the hyperspectral camera is folded, so that the size and the weight of the device are reduced by several times, the overall size and the weight of the device are greatly reduced, and the light source used in the invention is close to the surface of the sample, so that the detection accuracy is improved. Therefore, the power demand is only about 10% of that of the traditional technology, and by folding the light path structure, high-quality hyperspectral data are obtained while the size and the weight of the device are reduced, so that the detection effect of the hyperspectral technology on planar samples such as files, calligraphy and painting or screens is optimized, and the device can be automatically combined and used according to actual use conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of hyperspectral imaging, and in particular to a hyperspectral imaging detection device optimized for a planar sample and an optical path folding method thereof. Background Art

[0002] Hyperspectral imaging technology can simultaneously obtain optical and spectral information of the object to be tested, that is, it can sense the spatial difference in light intensity to form a photo, and can also obtain the spectrum of each pixel; hyperspectral imaging technology is an important detection method, and its optical information can be used for object recognition and identification, while the spectral information is used to identify chemical composition and judge the similarities and differences of substances; therefore, it is widely used in many fields such as agricultural remote sensing, physical evidence identification, and industrial testing.

[0003] A hyperspectral camera is a device that realizes hyperspectral imaging, among which the spatial scanning type (referred to as line scanning type) hyperspectral camera is the most mature technical route; the line scanning type can obtain the spatial information and complete spectral information on a line at one time through optical modulation of lenses, slits, gratings, etc.; and then by moving the position of the camera or sample in a direction perpendicular to the fixed axis and taking spectral images of lines at different positions, the complete hyperspectral imaging data can be pieced together.

[0004] To achieve complete hyperspectral imaging functions, a hyperspectral camera is usually combined with light source, translation stage, darkroom, controller and other components to form a hyperspectral detection device; the camera and light source are located on the top of the darkroom, and the sample is located on the translation stage at the bottom; the light source emits continuous wavelength light, which is reflected on the sample surface and received by the camera to form a hyperspectral image.

[0005] Plane samples refer to samples whose area to be tested can be roughly regarded as a two-dimensional plane, such as paper documents, product packaging, display screens, and even leaves, wood boards, etc.; plane samples occupy a considerable proportion in the demand for hyperspectral imaging detection. Application scenarios include but are not limited to document detection box identification in forensic science, color difference and color consistency identification of product packaging, brightness, saturation and hue correction of display screens, and detection of water content and fiber quality of wood.

[0006] Current hyperspectral detection devices are limited in function and performance and are unable to meet all hyperspectral photography requirements for planar samples.

[0007] First of all, common flat samples such as polished plastics, laser colored paper, laser anti-counterfeiting labels, etc. have peculiar reflective properties on their surfaces; that is, the reflection process of light on the surface of such samples cannot be approximated as isotropic diffuse reflection, but there are obvious differences in the direction and intensity of the reflected light; because the light source of the hyperspectral detection device hits the sample in a nearly vertical direction, it will be affected by mirror reflection and other factors.

[0008] On the other hand, due to the small field of view of hyperspectral cameras, existing devices have a series of problems: the equipment is large in size and volume, which is not conducive to transportation; the light source is far away from the sample, so the power must be increased, leading to energy consumption and heat dissipation problems; the equipment must use more precise slides and anti-vibration to capture data of sufficient quality, which makes it expensive.

[0009] Therefore, the present invention proposes a hyperspectral imaging detection device optimized for planar samples and an optical path folding method thereof. Without affecting the basic function of hyperspectral detection, the volume, weight, energy consumption and cost of the equipment are greatly reduced by optimizing the position and structure of the light source and folding the optical path. At the same time, the data quality for planar samples is improved, and samples with singular reflection characteristics can be handled. Summary of the invention

[0010] The purpose of the present invention is to provide a hyperspectral imaging detection device optimized for planar samples and an optical path folding method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0011] To achieve the above object, the present invention provides the following technical solution: a hyperspectral imaging detection device optimized for planar samples, comprising a protective shell, a transmission mechanism and a scanning box, wherein the protective shell comprises a bottom shell and a top plate, the scanning box slides horizontally in the bottom shell through the transmission mechanism, the scanning box comprises a bottom box and a box cover, a reflector group and a hyperspectral camera are respectively installed in the bottom box, and a working end of the hyperspectral camera extends into the bottom box;

[0012] Wherein, a slit is provided on the box cover, and a light source structure is installed on the box cover and on one side or both sides of the slit, and the width of the slit is 2mm-20mm;

[0013] The reflector group is composed of a series of reflectors at specific positions and directions, so that light from the sample and passing through the slit enters the entrance pupil position of the hyperspectral camera after being reflected by the reflectors in sequence;

[0014] Each reflector is a plane mirror or a reflector with curvature, and has sufficient reflectivity within the designed working wavelength range of the scanning box. Each reflector is made of a glass silver-coated reflector, a metal reflector or a designed total reflection prism.

[0015] As a further preferred embodiment of the present technical solution: the purpose of the reflector group is to reflect the incident light multiple times inside the scanning box, so as to achieve the purpose of folding the light path inside the scanning box, and finally send the optical signal to the hyperspectral camera;

[0016] The reflector group consists of a plurality of reflectors, which are installed at a specific angle and in a specific order in a manner that conforms to geometric optical characteristics, so as to guide the incident light from the slit to enter the subsequent optical structure after being reflected in sequence.

[0017] In this embodiment, specifically: the length of the equivalent optical path folded within the reflector group, and the length and width of each reflector surface should be determined by the field angle and working distance of the spectrometer, while the position, angle and number of reflections of the reflector should be designed in a comprehensive consideration with the expected spatial dimensions of the scanning box.

[0018] As a further preferred embodiment of the present technical solution: one reflector in the reflector group is used to receive reflection from the sample body and guide the part of diffusely reflected light into the light path folding path, and another reflector in the reflector group is used to send the reflected light into the hyperspectral camera for spectrometry;

[0019] The optical path folding distance achieved by the reflector group is equal to the distance from the sample body surface to the entrance pupil of the hyperspectral camera, which is equal to the working distance of the hyperspectral camera, so as to achieve a clear imaging effect. At the same time, when emitting, the fixed axis of the light is parallel to the fixed axis direction of the hyperspectral camera.

[0020] As a further preferred embodiment of the present technical solution: the length of each reflector in the reflector group is greater than or equal to the reduced length of the fixed axis of the incident light when reflected by the mirror surface, and the reduced length is the product of the length of the fixed axis at the mirror surface multiplied by the secant of the angle between the mirror surface and the light propagation direction, and the calculation formula is:

[0021] L=L 0,d secθ (1)

[0022] In formula (1), L is the reduced length, i.e., the minimum length allowed by the mirror in the fixed axis direction. 0，d is the fixed axis length at the mirror surface, that is, the minimum length of the mirror when it is perpendicular to the propagation direction of the optical path, d is the distance between the mirror surface and the entrance pupil of the hyperspectral camera lens, and θ is the angle between the mirror surface and the propagation direction of the optical path;

[0023] Among them, for the mirror perpendicular to the propagation direction of the light path, its minimum length should not be less than the fixed axis length here, and for the mirror inclined at 45°, its length should not be less than 2 times the square root of the fixed axis length here. The fixed axis lengths at various locations in the reflector group can be obtained by simply solving similar triangles:

[0024]

[0025] In formula (2), L0 is the fixed axis length (the length of the area where the sample body can be photographed), and d0 is the length of the folded light path, that is, the working distance of the hyperspectral camera.

[0026] As a further preferred embodiment of the technical solution: a sample placement table for placing the sample body is installed in the top plate, and a cover plate is hinged on the top plate through a pin shaft;

[0027] The sample placement table is transparent within the working wavelength range of the entire device without obvious absorption, and the sample placement table is made of glass, quartz glass, sapphire, and acrylic.

[0028] As a further preferred embodiment of the present technical solution: the transmission mechanism comprises a stepping motor and a screw rod, one end of the screw rod is mounted on the output end of the stepping motor, and the other end of the screw rod is connected to the bottom shell through a bearing;

[0029] Wherein, a rolling nut for use with the screw rod is installed on the outer side of the screw rod, and the scanning box is installed on the rolling nut.

[0030] As a further preferred embodiment of the technical solution: two positioning rods are symmetrically fixedly connected on both sides of the bottom shell, and the two positioning rods both penetrate the scanning box.

[0031] As a further preferred embodiment of the present technical solution: the bottom shell is fixedly connected to the top plate, the box bottom is fixedly connected to the box cover, the box bottom and the box cover constitute a "black box structure", and the "black box structure" is used to block external light and stray light, thereby ensuring that only the diffusely reflected light of the sample body enters through the slit, avoiding that no other light source enters the "black box structure", and is used to receive components installed thereon or inside it.

[0032] The optical path folding method of a hyperspectral imaging detection device optimized for a planar sample comprises the following steps:

[0033] S1. The light source structure is set to irradiate the sample body through the sample placement table;

[0034] S2, the sample body diffusely reflects the light source received through the sample placement table into the slit;

[0035] S3, the light source entering the slit is irradiated onto a reflector in the reflector group;

[0036] S4, the light path is reflected in sequence by multiple reflectors;

[0037] S5. Finally, the light source is reflected into the entrance pupil position of the hyperspectral camera by another reflector in the reflector group.

[0038] As a further preferred embodiment of the present technical solution: the light source structure is used to illuminate the sample body with a specific angle distribution and a specific spectral wavelength characteristic, so that it produces reflected light or fluorescence, and the reflected light or fluorescence will show different reflectivity and fluorescence intensity at different wavelengths according to the different chemical components of the sample body, that is, the reflection spectrum or fluorescence spectrum;

[0039] As a further preferred embodiment of the present technical solution: the light source structure projects light with highly similar characteristics at each point on the sample surface, and presents specific spatial distribution characteristics of the light according to the sample requirements. In order to achieve more efficient and controllable lighting, the light source structure should be as close to the sample body as possible, so that the distance from the surface of the sample body is 0.5cm-5cm.

[0040] The light source structure includes a structural slot, a lamp group and a physical adjustment device. The physical adjustment device includes a soft light sheet or a filter. The main function of the soft light is to perform Gaussian blur on the light to make the originally uneven spatial illumination uniform. Common ones include soft light sheets, frosted glass sheets and light guides. The filter is to correct the spectral characteristics of the light source and filter out unnecessary emission wavelengths, so as to obtain a better light source emission spectrum.

[0041] The light source types in the lamp group are white light source and fluorescent light source, wherein the white light source can cover a wide spectrum light source in the working wavelength range, that is, the light source is required to have sufficient light intensity density at any wavelength in the detected wavelength range, and the white light source adopts a wide spectrum white light LED, arc lamp or halogen tungsten lamp;

[0042] The fluorescent light source provides a light source for sample fluorescence excitation, which is one or more groups of single-wavelength ultraviolet light sources with narrow half-width, using ultraviolet LEDs or low-pressure mercury lamps.

[0043] As a further preferred embodiment of the present technical solution: the folded optical path sends the diffuse reflected light from the sample body into the hyperspectral camera for imaging after multiple optical reflections. At the same time, the light is modulated and folded during the optical reflection process, thereby reducing the overall size of the device and reducing the interference of stray light and vibration, so as to obtain accurate data.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The present invention folds the optical path structure to obtain high-quality hyperspectral data while reducing the volume and weight of the device, thereby optimizing the detection effect of hyperspectral technology on flat samples such as documents, calligraphy and paintings or screens. At the same time, the operation method of the present invention can be optimized according to the special reflection characteristics of the sample, filling or compensating for the deficiency that the existing hyperspectral imaging solution cannot effectively capture samples with singular reflection characteristics;

[0046] 2. The present invention can perform different types of hyperspectral detection on planar samples and optimize the lighting scheme according to the reflective characteristics of the sample surface. By appropriately replacing the components inside the device, the scheme can be applicable to the current common hyperspectral device working wavelength range, from 400nm to 25μm. At the same time, by changing the type of light source, hyperspectral imaging detection functions including reflection spectrum, fluorescence spectrum and even Raman spectrum can be realized. Further, by changing the irradiation mode of the light source component, multiple types of lighting such as top light, side light, Gaussian light, etc. can be realized;

[0047] 3. The present invention folds the optical path from the sample to the hyperspectral camera, which reduces the volume and weight of the device by several times, thereby effectively achieving a significant reduction in the overall volume and weight of the device. In addition, since the light source of the device in the traditional technical solution is far away from the sample, it usually requires tens or even hundreds of watts, while the light source used in the present invention is close to the sample surface, so the power requirement is only about 10% of the traditional technology, thereby greatly reducing the energy consumption of the device;

[0048] 4. The built-in "black box structure" of the device of the present invention isolates the interference of ambient light, the light source is more uniform and brighter, and the compact device size reduces the impact of vibration during shooting, thereby comprehensively improving the data quality;

[0049] 5. The present invention can analyze samples with strange reflective properties. Compared with the traditional solution, the light source can only be installed on the top of the equipment, so it can only ensure uniform light intensity distribution, but cannot adjust the angle of the incident light and its distribution. In this application, the incident angle distribution of the light source can be adjusted according to the different needs of the samples. Therefore, samples with strange reflective properties such as grating paper and laser anti-counterfeiting labels can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of the structure of a hyperspectral imaging detection device optimized for planar samples according to the present invention;

[0051] Figure 2 This is a schematic diagram of the structure inside the bottom shell of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0052] Figure 3 A schematic diagram of the top view of the structure inside the bottom shell of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0053] Figure 4 A schematic diagram of the structure of a scanning box in a hyperspectral imaging detection device optimized for planar samples of the present invention;

[0054] Figure 5 This is a schematic diagram of the structure inside the bottom box of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0055] Figure 6 A schematic diagram of the cross-sectional structure of a scanning box in a hyperspectral imaging detection device optimized for a planar sample according to the present invention;

[0056] Figure 7 A schematic diagram of the folding path structure of the optical path folding method of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0057] Figure 8 The operating flow chart of the optical path folding method of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0058] Fig. 9 A schematic diagram of the structure of the fluorescent light source irradiation in the optical path folding method of the hyperspectral imaging detection device optimized for a planar sample according to the present invention;

[0059] Fig.10 It is a structural flow chart of dome light source irradiation in the optical path folding method of the hyperspectral imaging detection device optimized for planar samples of the present invention;

[0060] Fig.11 It is an operation flow chart of the side light source illumination in the light path folding method of the hyperspectral imaging detection device optimized for the planar sample of the present invention;

[0061] Fig.12 The optical path folding diagram of Example 5 in the optical path folding method of the hyperspectral imaging detection device optimized for a planar sample of the present invention;

[0062] Fig.13 This is a light path folding diagram of Example 6 of the light path folding method of the hyperspectral imaging detection device optimized for planar samples of the present invention.

[0063] In the figure: 1. protective shell; 11. bottom shell; 12. top plate; 121. sample placement table; 122. cover plate; 2. stepper motor; 3. lead screw; 4. positioning rod; 5. scanning box; 51. bottom box; 511. reflector assembly; 512. hyperspectral camera; 52. box cover; 521. light source structure; 522. slit. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0065] Example 1

[0066] See also Figure 1-Figure 8The present invention provides a technical solution: a hyperspectral imaging detection device optimized for a planar sample, comprising a protective shell 1, a transmission mechanism and a scanning box 5, wherein the protective shell 1 comprises a bottom shell 11 and a top plate 12, the scanning box 5 slides horizontally in the bottom shell 11 through the transmission mechanism, the scanning box 5 comprises a bottom box 51 and a box cover 52, a reflector group 511 and a hyperspectral camera 512 are respectively installed in the bottom box 51, and a working end of the hyperspectral camera 512 extends into the bottom box 51;

[0067] The box cover 52 is provided with a slit 522, and a light source structure 521 is installed on the box cover 52 and on one or both sides of the slit 522. The width of the slit 522 is 2 mm-20 mm.

[0068] The reflector group 511 is composed of a series of reflectors at specific positions and directions, so that the light from the sample and passing through the slit 522 enters the entrance pupil position of the hyperspectral camera 512 after being reflected by the reflectors in sequence;

[0069] Among them, each reflector is a plane mirror or a curved reflector, and has sufficient reflectivity (generally not less than 80%) within the designed working wavelength range of the scanning box 5, and each reflector is made of a glass silver-coated reflector, a metal reflector or a designed total reflection prism.

[0070] In this embodiment, specifically: the purpose of the reflector group 511 is to reflect the incident light multiple times inside the scanning box 5, so as to achieve the purpose of folding the light path inside the scanning box 5, and finally send the optical signal to the hyperspectral camera 512;

[0071] The reflector group 511 is composed of a plurality of reflectors, which are installed at a specific angle and in a specific order in a manner that conforms to geometric optical characteristics, so as to guide the incident light from the slit 522 to enter the subsequent optical structure after being reflected in sequence.

[0072] In this embodiment, specifically: the length of the equivalent optical path folded in the reflector group 511, and the length and width of each reflector surface should be determined by the field angle and working distance of the spectrometer, while the position, angle and number of reflections of the reflector should be designed in a comprehensive consideration with the expected spatial dimensions of the scanning box 5.

[0073] In this embodiment, specifically: one reflector in the reflector group 511 is used to receive reflection from the sample body and guide the diffusely reflected light into the folded light path, and another reflector in the reflector group 511 is used to send the reflected light into the hyperspectral camera 512 for spectrometry;

[0074] Among them, the optical path folding distance achieved by the reflector group 511 is equal to the distance from the surface of the sample body to the entrance pupil of the hyperspectral camera 512, which is equal to the working distance of the hyperspectral camera 512, so as to achieve a clear imaging effect. At the same time, when emitting, the fixed axis of the light is parallel to the fixed axis direction of the hyperspectral camera 512.

[0075] In this embodiment, specifically: the length of each reflector in the reflector group 511 is greater than or equal to the reduced length of the fixed axis of the incident light when reflected by the mirror surface, and the reduced length is the product of the length of the fixed axis at the mirror surface multiplied by the secant of the angle between the mirror surface and the light propagation direction, and the calculation formula is:

[0076] L=L 0,d secθ (1)

[0077] In formula (1), L is the reduced length, i.e., the minimum length allowed by the mirror in the fixed axis direction. 0，d is the fixed axis length at the mirror surface, that is, the minimum length of the mirror when perpendicular to the propagation direction of the optical path, d is the distance between the mirror surface and the entrance pupil of the hyperspectral camera 512 lens, and θ is the angle between the mirror surface and the propagation direction of the optical path;

[0078] Among them, for the mirror surface perpendicular to the propagation direction of the optical path, its minimum length should not be less than the fixed axis length here, and for the mirror surface inclined at 45°, its length should not be less than 2 times the square root of the fixed axis length here. The fixed axis lengths at various locations in the reflector group 511 can be obtained by simply solving similar triangles:

[0079]

[0080] In formula (2), L0 is the fixed axis length (the length of the area of ​​the sample body that can be photographed), and d0 is the length of the folded light path, that is, the working distance of the hyperspectral camera 512.

[0081] In this embodiment, specifically: a sample placement table 121 for placing the sample body is installed in the top plate 12, and a cover plate 122 is hinged on the top plate 12 through a pin shaft;

[0082] The sample placement platform 121 is transparent within the working wavelength range of the entire device without obvious absorption, and the sample placement platform 121 is made of glass, quartz glass, sapphire, and acrylic.

[0083] In this embodiment, specifically: the transmission mechanism includes a stepper motor 2 and a screw rod 3, one end of the screw rod 3 is installed at the output end of the stepper motor 2, and the other end of the screw rod 3 is connected to the bottom shell 11 through a bearing, and the stepper motor 2 is set as the driving body, thereby driving the scanning box 5 to run through the screw rod 3;

[0084] A rolling nut is installed on the outer side of the screw rod 3 for use with the screw rod, and the scanning box 5 is installed on the rolling nut.

[0085] In this embodiment, specifically: two positioning rods 4 are symmetrically fixedly connected on both sides of the bottom shell 11 , and both positioning rods 4 pass through the scanning box 5 . The running direction of the scanning box 5 is limited and guided by the provided positioning rods 4 .

[0086] In the present embodiment, specifically: the bottom shell 11 is fixedly connected to the top plate 12, the box bottom 51 is fixedly connected to the box cover 52, the box bottom 51 and the box cover 52 constitute a "black box structure", the "black box structure" is used to block external light and stray light, thereby ensuring that only the diffusely reflected light of the sample body enters through the slit 522, avoiding that no other light source enters the "black box structure", and is used to receive components installed thereon or inside thereof.

[0087] The optical path folding method of a hyperspectral imaging detection device optimized for a planar sample comprises the following steps:

[0088] S1, the light source of the light source structure 521 is set to irradiate the sample body through the sample placement table 121;

[0089] S2, the sample body diffusely reflects the light source received through the sample placement table 121 into the slit 522;

[0090] S3, the light source entering the slit 522 is irradiated onto a reflector in the reflector group 511;

[0091] S4, the light path is reflected in sequence by multiple reflectors;

[0092] S5. Finally, another reflector in the reflector group 511 reflects the light source into the entrance pupil position of the hyperspectral camera 512.

[0093] In this embodiment, specifically: the function of the light source structure 521 is to illuminate the sample body with a specific angle distribution and a specific spectral wavelength characteristic, so that it produces reflected light or fluorescence, and the reflected light or fluorescence will show different reflectivity and fluorescence intensity at different wavelengths according to the different chemical components of the sample body, that is, the reflection spectrum or fluorescence spectrum;

[0094] In this embodiment, specifically: the light source structure 521 projects light with highly similar characteristics at each point on the sample surface, and presents specific light spatial distribution characteristics according to the sample requirements. In order to achieve more efficient and controllable lighting, the light source structure 521 should be as close to the sample body as possible, so that the distance from the surface of the sample body is 0.5cm-5cm.

[0095] The type of light source and the spectral characteristics of the emission in the light source structure 521 are determined according to the measurement method requirements of the device, and the light source structure 521 includes a structural slot, a lamp group and a physical adjustment device. The physical adjustment device includes a soft light sheet or a filter. The main function of the soft light is to perform Gaussian blur on the light to make the originally uneven spatial illumination uniform. Common ones include soft light sheets, frosted glass sheets and light guides. The filter is to correct the spectral characteristics of the light source and filter out unnecessary emission wavelengths, so as to obtain a better light source emission spectrum.

[0096] Among them, the light source types in the lamp group are white light source and fluorescent light source, wherein the white light source can cover the wide spectrum light source of the working wavelength range, that is, the light source is required to have sufficient light intensity density at any wavelength within the detected wavelength range, and the white light source adopts a wide spectrum white light LED, arc lamp or halogen tungsten lamp;

[0097] The fluorescent light source provides a light source for sample fluorescence excitation, which is one or more groups of single-wavelength ultraviolet light sources with narrow half-width, preferably with a central wavelength in the range of 240nm-260nm or 340nm-390nm, using ultraviolet LED or low-pressure mercury lamp.

[0098] In this embodiment, specifically: the folded light path sends the diffuse reflected light from the sample body to the hyperspectral camera 512 for imaging after multiple optical reflections. At the same time, the light is modulated and folded during the optical reflection process, thereby reducing the overall size of the device and reducing the interference of stray light and vibration, so as to obtain accurate data.

[0099] Example 2

[0100] See also Fig. 9 The present invention provides a technical solution, a fluorescent light source irradiation structure:

[0101] Fluorescence spectroscopy analysis of samples can be performed by using a low-pressure mercury lamp as the light source and filtering out the visible light through a 400nm short-wave filter. When ultraviolet excitation of a specific wavelength is required, the mercury lamp can be replaced with an ultraviolet LED of the corresponding wavelength, or the filter can be replaced with a bandpass filter of the required wavelength.

[0102] Example 3

[0103] See also Fig.10 The present invention provides a technical solution, a dome light source irradiation structure:

[0104] A semi-cylindrical structure is formed with the slit 522 as the center, and a white light LED light source that meets the wavelength requirements is installed in parallel on the inner wall of the cylindrical structure. In front of the LED light source, a soft light plate is installed to Gaussianize the LED light, thereby achieving uniform illumination of the sample surface in all directions and eliminating the light and dark effects caused by the undulations on the sample surface, so as to measure the absolute reflectivity of the sample.

[0105] Example 4

[0106] See also Fig.11 The present invention provides a technical solution, a side light source irradiation structure:

[0107] The light emitted by the fluorescent light source is guided by the light guide and irradiates the sample at a large incident angle on the side of the slit 522. The side light source can enhance the concave-convex structure of the plane sample surface and is used to identify foreign matter such as stains and contamination on the sample surface.

[0108] Example 5

[0109] See also Fig.12 , the present invention provides a technical solution, a light path folding method:

[0110] Three total reflection prisms are used as a mirror group, so that the light reaches the hyperspectral camera 512 after a total of five total reflections. The total reflection prism can reduce the energy loss of light in the total reflection process and reduce the selective absorption of light at different wavelengths by the mirror, thereby reducing the demand for light source intensity and improving data quality.

[0111] Example 6

[0112] See also Fig.12 , the present invention provides a technical solution, a light path folding method:

[0113] A plane reflector and two parabolic reflectors are used as a mirror group, so that the light reaches the hyperspectral camera 512 after undergoing three total reflections. The parabolic reflector can fold the light more effectively, thereby reducing the number of lenses required for folding the light path.

[0114] In summary: Examples 1 to 6 can be combined and used according to actual usage. What needs to be further explained is that the line scanning type can obtain the spatial information and complete spectral information of a line at one time through optical modulation of lenses, slits, gratings, etc. (for the convenience of explanation, the direction in which this line extends is referred to as the "fixed axis" in the text), and then by moving the position of the camera or the sample in a direction perpendicular to the fixed axis, the spectral images of the lines at different positions are taken, which can be pieced together into complete hyperspectral imaging data.

[0115] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hyperspectral imaging detection device optimized for planar samples, comprising a protective shell (1), a transmission mechanism and a scanning box (5), wherein the protective shell (1) comprises a bottom shell (11) and a top plate (12), and the scanning box (5) slides horizontally in the bottom shell (11) through the transmission mechanism, characterized in that: The scanning box (5) comprises a bottom box (51) and a box cover (52), wherein a reflector group (511) and a hyperspectral camera (512) are respectively installed in the bottom box (51), and a working end of the hyperspectral camera (512) extends into the bottom box (51); The box cover (52) is provided with a slit (522), and a light source structure (521) is installed on the box cover (52) and located on one side or both sides of the slit (522); The reflector group (511) is composed of a series of reflectors at specific positions and directions, so that light from the sample and passing through the slit (522) enters the entrance pupil position of the hyperspectral camera (512) after being reflected by the reflectors in sequence; Each reflector is a plane mirror or a reflector with curvature, and has sufficient reflectivity within the designed working wavelength range of the scanning box (5). Each reflector is made of a glass silver-plated reflector, a metal reflector or a designed total reflection prism.

2. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: One reflector in the reflector group (511) is used to receive reflection from the sample body and guide the part of diffusely reflected light into the light path folding path, and another reflector in the reflector group (511) is used to send the reflected light into the hyperspectral camera (512) for spectrometry; The optical path folding distance achieved by the reflector group (511) is equal to the distance from the surface of the sample body to the entrance pupil of the hyperspectral camera (512), which is equal to the working distance of the hyperspectral camera (512), thereby achieving a clear imaging effect. At the same time, when emitting, the fixed axis of the light is parallel to the fixed axis direction of the hyperspectral camera (512).

3. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: The length of each reflector in the reflector group (511) is greater than or equal to the reduced length of the fixed axis of the incident light when reflected by the mirror surface, and the reduced length is the product of the length of the fixed axis at the mirror surface multiplied by the secant of the angle between the mirror surface and the light propagation direction, and the calculation formula is: L=L 0,d secθ (1) In formula (1), L is the reduced length, i.e., the minimum length allowed by the mirror in the fixed axis direction. 0，d is the fixed axis length at the mirror surface, that is, the minimum length of the mirror when perpendicular to the propagation direction of the light path, d is the distance between the mirror surface and the entrance pupil of the hyperspectral camera (512), and θ is the angle between the mirror surface and the propagation direction of the light path; Among them, for the mirror surface perpendicular to the propagation direction of the optical path, its minimum length should not be less than the fixed axis length here, and for the mirror surface inclined at 45°, its length should not be less than 2 times the square root of the fixed axis length here. The fixed axis lengths at various locations in the reflector group (511) can be obtained by simply solving similar triangles: In formula (2), L0 is the fixed axis length (the length of the area of ​​the sample body that can be photographed), and d0 is the length of the folded light path, that is, the working distance of the hyperspectral camera (512).

4. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: A sample placement table (121) for placing a sample body is installed in the top plate (12), and a cover plate (122) is hingedly connected to the top plate (12) via a pin shaft; The sample placement platform (121) is transparent within the working wavelength range of the entire device and has no obvious absorption. The sample placement platform (121) is made of glass, quartz glass, sapphire, and acrylic.

5. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: The transmission mechanism comprises a stepping motor (2) and a screw rod (3), one end of the screw rod (3) is mounted on the output end of the stepping motor (2), and the other end of the screw rod (3) is connected to the bottom shell (11) via a bearing; Wherein, a rolling nut for use with the screw rod (3) is installed on the outside thereof, and the scanning box (5) is installed on the rolling nut.

6. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: Two positioning rods (4) are symmetrically fixedly connected to the two sides of the bottom shell (11), and the two positioning rods (4) both penetrate the scanning box (5).

7. The hyperspectral imaging detection device optimized for planar samples according to claim 1, characterized in that: The bottom shell (11) is fixedly connected to the top plate (12), and the box bottom (51) is fixedly connected to the box cover (52). The box bottom (51) and the box cover (52) constitute a "black box structure". The "black box structure" is used to block external light and stray light, thereby ensuring that only diffusely reflected light from the sample body enters through the slit (522) to prevent other light sources from entering the "black box structure", and is used to receive components installed thereon or inside thereof.

8. A light path folding method for a hyperspectral imaging detection device optimized for planar samples, characterized in that: The following steps are involved: S1, the light source structure (521) is set to irradiate the sample body through the sample placement table (121); S2, the sample body diffusely reflects the light source received through the sample placement table (121) into the slit (522); S3, the light source entering the slit (522) is irradiated onto a reflector in the reflector group (511); S4, the light path is reflected in sequence by multiple reflectors; S5. Finally, another reflector in the reflector group (511) reflects the light source into the entrance pupil position of the hyperspectral camera (512).

9. The optical path folding method of the hyperspectral imaging detection device optimized for planar samples according to claim 7, characterized in that: The function of the light source structure (521) is to illuminate the sample body with a specific angle distribution and a specific spectral wavelength characteristic, so that it produces reflected light or fluorescence; The light source structure (521) comprises a structural slot, a lamp group and a physical adjustment device. The physical adjustment device comprises a soft light sheet or a filter. The main function of the soft light sheet is to perform Gaussian blur on the light, so that the originally uneven spatial illumination becomes uniform. Common soft light sheets include soft light sheets, frosted glass sheets and light guides. The light filter is to correct the spectral characteristics of the light source and filter out unnecessary emission wavelengths, so as to obtain a better emission spectrum of the light source. The light source types in the lamp group are white light source and fluorescent light source, wherein the white light source can cover a wide spectrum light source in the working wavelength range, that is, the light source is required to have sufficient light intensity density at any wavelength in the detected wavelength range, and the white light source adopts a wide spectrum white light LED, arc lamp or halogen tungsten lamp; The fluorescent light source provides a light source for sample fluorescence excitation, which is one or more groups of single-wavelength ultraviolet light sources with narrow half-width, using ultraviolet LEDs or low-pressure mercury lamps.

10. The optical path folding method of the hyperspectral imaging detection device optimized for planar samples according to claim 7, characterized in that: The folded optical path sends the diffusely reflected light from the sample body to the hyperspectral camera (512) for imaging after multiple optical reflections. At the same time, the light is modulated and folded during the optical reflection process, thereby reducing the overall size of the device and reducing the interference of stray light and vibration, so as to obtain accurate data.

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