CN117705282A - Spectral imaging method based on double microlens array segmentation - Google Patents
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Abstract
The invention discloses a spectrum imaging method based on double micro-lens array segmentation, in particular to the technical field of spectrum imaging, which comprises a first lens group G1, a second lens group G2 and a third lens group G3, wherein the incidence direction of light rays is sequentially arranged from left to right, scene information is collected by the G1, and a generated spectrum image is focused on an image plane by the G3 through collimation, segmentation and dispersion of the G2; the first lens group G1 is a projection lens, and the first lens group G1 includes nine lenses, i.e., L1, L2, L3, L4, L5, L6, L7, L8, and L9; the second lens group G2 is an image segmentation and dispersion module and consists of a collimating lens L10, a first micro-lens array, an area array diaphragm, a second micro-lens array and a dispersion prism. The invention can realize high-energy transmittance spectrum imaging, improve imaging quality, reduce spectrum distortion and avoid spectrum bending.
Description
Technical Field
The invention relates to the technical field of spectral imaging, in particular to a spectral imaging method based on double-microlens array segmentation.
Background
The spectrometer is an important measuring instrument, can decompose compound light, can directly acquire substance information through researching and analyzing spectrum information formed by the compound light, the spectrum imaging technology type can be divided into a swinging scanning type, a pushing scanning type and a snapshot type according to a scanning mode for acquiring a three-dimensional data cube, and the snapshot type imaging spectrometer becomes a hot spot direction of spectrometer research due to the advantages of strict structure, simple principle, low cost and the like.
The related scholars have proposed a prism mask spectrum optical system, which is composed of a triangular prism, a monochromatic camera and a mask, wherein incident light rays from a scene are sampled by the mask, a two-dimensional image is discretized to separate a space for chromatic dispersion, and the sparse light rays are dispersed through the triangular prism to form a spectrum and then captured by the monochromatic camera. The system utilizes the mask to replace a slit, controls the imaging of a spectrum on the CCD, improves the spatial resolution, reduces the spectrum distortion, has an integral structure which is composed of only a few low-cost optical devices and is easy to build and calibrate, however, the system is too heavy, and the mask is used for isolating most of light, so that the energy transmittance of the system is low, clear spectrum images are difficult to acquire in time, and the spectrum information is extremely easy to lose.
In order to solve the problem of light miniaturization of a mask type spectrometer, aiming at an optical information capturing part, a learner places an objective lens in front of a mask and performs simplified design of the number of lenses, a traditional prism is replaced by a grating, linear dispersion is realized, the structure is further compact, meanwhile, an incident scene is divided into two paths of space dimension and spectrum dimension through the spectroscope to be respectively collected, a space dimension light path image is obtained by utilizing an RGB camera, a high spatial resolution image is obtained, and then information fusion is performed on the high spatial resolution light path image, so that the acquisition of a spectrum high-dynamic video signal is realized. The system realizes the simplification of the snapshot spectrometer, improves the spatial resolution of the spectrum image, but still has the problem of low energy transmittance.
Meanwhile, a learner designs a large-view-field high-resolution imaging spectrometer, improves an objective lens on the basis of the existing snapshot imaging spectrometer, designs a large-view-field space telecentric lens to capture a scene image, widens the view angle to 48.8 degrees, and improves the incident light intensity of the whole system. The system utilizes micron-scale mask sampling, generates a spectrum image with high spectrum resolution by combining dispersive light rays through a prism-grating, and reduces the aperture of the mask, while improving the spectrum resolution, the energy transmittance is also seriously affected, and the system only calibrates the light rays at the central position, so that the spectrum curve is bent.
In summary, the problems in the spectral imaging method of the prior art are as follows:
1. the scene image obtained by using the mask sampling causes the energy transmittance of the optical system to be extremely low, and influences the imaging and the obtaining of the spectrum image;
2. the image is segmented and calibrated by only using the mask aperture imaging and single microlens collimation combination, so that the emergent ray direction of the peripheral position unit microlenses is different from that of the central position unit microlenses, and the spectrum curve is bent;
3. secondary overlapping and ghost phenomena are easily generated by utilizing grating dispersion light.
Disclosure of Invention
In order to overcome the above-mentioned drawbacks of the prior art, the present invention provides a spectral imaging method based on dual microlens array segmentation.
In order to achieve the above purpose, the present invention provides the following technical solutions: the spectral imaging method based on the double micro lens array segmentation comprises a first lens group G1, a second lens group G2 and a third lens group G3, wherein the incidence direction of light rays is sequentially arranged from left to right, scene information is collected by the G1, and a generated spectral image is focused on an image plane by the G3 through collimation, segmentation and dispersion of the G2;
the first lens group G1 is a projection lens, and the first lens group G1 includes nine lenses, i.e., L1, L2, L3, L4, L5, L6, L7, L8, and L9;
the second lens group G2 is an image segmentation and dispersion module and consists of a collimating lens L10, a first micro-lens array, a planar array diaphragm, a second micro-lens array and a dispersion prism;
the third lens group G3 is a telecentric lens and consists of four lenses L11, L12, L13 and L14.
As a further improvement of the present invention, among the nine lenses in the first lens group G1, at least one lens has a refractive index nd > 1.8 and at least one lens has an abbe number Vdl < 40.
As a further improvement of the technical scheme of the present invention, the collimating lens L10 is disposed at the rear side of the projection lens, i.e. the first lens group G1, and is used for collimating the collected light and controlling the size of the light beam, so that the light beam is parallel-injected into the first microlens array with a size slightly smaller than that of the microlens array.
As a further improvement of the technical scheme of the invention, the first micro-lens array divides light rays through a lens focusing function, cuts images in a low-energy-loss mode, and the second micro-lens array collimates micro-light beams focused by the first micro-lens array one by one so that the micro-light beams are emitted in parallel in the same direction.
As a further improvement of the technical scheme of the invention, the area array diaphragm is arranged at the back focal length of the first micro lens array and the front focal length of the second micro lens array, and the dispersion prism is used for dispersing light so as to generate a spectral image, is arranged at the rear side of the second micro lens array and controls the length of the spectral line together with the second micro lens array.
As a further improvement of the technical scheme of the invention, the material of the dispersion prism is K9, and the size is 40-40 mm; the first micro-lens array and the second micro-lens array are two-dimensional lens arrays with 15 x 15, and the diameter of each sub-lens is 500nm; the area array diaphragm is made of an opaque metal copper sheet through punching, the diameter of the sub-aperture is 100nm, and the center distance of the aperture is 500nm.
As a further improvement of the technical scheme of the invention, the centers of the subunits of the first micro lens array, the area array diaphragm and the second micro lens array are in one-to-one correspondence, and the collimating lens L10, the first micro lens array, the area array diaphragm, the second micro lens array and the dispersion prism are coaxial.
The invention has the beneficial effects that:
1. the invention provides a double micro-lens array model, which utilizes lens focusing to replace mask aperture imaging to complete image segmentation task, changes a cutting mode in principle, improves energy transmittance, improves spectrum image brightness, enables the spectrum image brightness to be imaged clearly and is easier to capture by a camera;
2. the invention uses the one-to-one correspondence of sub lenses between the double micro lens array models to divide and collimate the acquired light, ensures that the emergent light of each lens is emitted in parallel towards a uniform direction and then enters a dispersion element, realizes the linear dispersion of the spectrum, solves the curve bending problem, and the mask acts as a planar array diaphragm to isolate stray light and wrong light, thereby becoming a second guarantee for avoiding the spectrum bending;
3. the invention uses the dispersion prism to replace the grating to realize the light dispersion, the dispersion prism has the advantages of low price, no light spectrum overlapping, good stability, little stray light, no secondary overlapping, no ghost wires and the like, therefore, the invention can realize the spectrum non-aliasing dispersion by using the dispersion prism as the dispersion element.
Drawings
FIG. 1 is a simulation of an optical structure of the present invention.
FIG. 2 is a graph showing the relationship between the energy transmittance and the aperture of a mask according to the present invention.
FIG. 3 is a graph of spectral distortion in accordance with the present invention.
FIG. 4 is a graph of spectral curvature versus object height for the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The spectral imaging method based on double micro-lens array segmentation as shown in fig. 1 comprises a first lens group G1, a second lens group G2 and a third lens group G3, wherein the incidence direction of light rays is sequentially arranged from left to right, scene information is collected by the G1, and a generated spectral image is focused on an image plane by the G3 through collimation, segmentation and dispersion of the G2;
the first lens group G1 is a projection lens, and the first lens group G1 includes nine lenses, i.e., L1, L2, L3, L4, L5, L6, L7, L8, and L9;
the second lens group G2 is an image segmentation and dispersion module and consists of a collimating lens L10, a first micro-lens array, an area array diaphragm, a second micro-lens array and a dispersion prism;
the third lens group G3 is a telecentric lens, and is composed of four lenses L11, L12, L13, and L14.
Preferably, among the nine lenses in the first lens group G1, at least one lens has a refractive index nd > 1.8, and at least one lens has an abbe number Vdl < 40, specific parameters of each lens are shown in table 1, the projection lens has a large field angle, and the projection lens captures scene information to obtain a large field image and higher luminous flux;
table 1 relevant parameter table of each lens in projection lens (G1)
Where R value refers to the radius of curvature of the surface, thickness refers to the on-axis distance of the current surface to the next surface, e.g., the thickness of surface S1 is the distance from S1 to S2, which may be the on-axis thickness of the medium or lens, and may be the on-axis air gap between them, nd and Vd are the refractive index abbe numbers of the material, respectively.
The image segmentation and dispersion module (the second lens group G2) is used as the core of the invention and is composed of 5 optical devices, namely a collimating lens L10, a first micro-lens array, a planar array diaphragm, a second micro-lens array and a dispersion prism, wherein specific parameters are shown in a table 2, the collimating lens L10 is arranged behind a projection lens, the converging light rays are collimated and the size of the light rays is controlled to enable the converging light rays to be parallel-injected into the first micro-lens array in a size slightly smaller than that of the micro-lens array, the first micro-lens array segments the light rays through a lens focusing function, an image is cut in a low energy loss mode to reserve space for dispersion, the second micro-lens array collimates the micro-light rays focused by the first micro-lens array one by one to enable the micro-light rays to be parallel-injected in the same direction, the main reason that the traditional spectrometer generates spectrum bending is that the directions of the parallel light rays of the incident prism are inconsistent, and the double-micro-lens array model can provide parallel micro-light rays with the consistent directions, so that the spectrum bending is fundamentally avoided; the area array diaphragm is arranged at the back focal length of the first micro lens array and the front focal length of the second micro lens array, so that stray light and error light are isolated, and the area array diaphragm becomes a second defense line for preventing spectrum bending; the prism is used for dispersing light to generate a spectral image, is arranged at the rear side of the second micro lens array, and controls the lengths of the spectral lines together with the second micro lens array to enable the spectral lines to be mutually separated so as to prevent aliasing interference.
TABLE 2 correlation parameter tables for each lens in image splitting and dispersing Module (G2)
Wherein S3 and S4 are the surfaces of a first micro-lens array, S7 and S8 are the surfaces of the first micro-lens array, the R value represents the curvature radius of a single sub-lens of the micro-lens array, the material of a dispersion prism is K9, the size of the dispersion prism is 40 x 40mm, and the first micro-lens array and the second micro-lens array used in the invention are two-dimensional lens arrays with 15 x 15, and the diameter of the sub-lens is 500nm; the area array diaphragm is made of an opaque metal copper sheet by punching, the diameter of a sub-aperture of the area array diaphragm is 100nm, and the center distance of the aperture is 500nm; in the installation process, the centers of the subunits of the first micro lens array, the area array diaphragm and the second micro lens array are in one-to-one correspondence, and the collimating lens L10, the first micro lens array, the area array diaphragm, the second micro lens array and the dispersion prism are coaxial.
The telecentric lens (G3) comprises four lenses L11, L12, L13 and L14, the specific parameters of each lens are shown in table 3, the telecentric lens has the characteristics of stable magnification and eliminating perspective effect, so that the photographed image is clear and deformation-free, the error can be obviously reduced, the telecentric lens is used for capturing a spectrum image, and the spectrum can be imaged in a CCD clearly and deformation-free.
Table 3 table of parameters related to each lens in telecentric lens (G3)
As shown in figures 2-4, the spectrometer provided by the invention can realize high-energy transmittance and low-distortion spectral imaging, wherein the energy transmittance is more than 66.2%, the overall distortion is less than 0.43%, and the spectral curvature is less than 22% of pixels.
Working principle: the invention provides a novel image segmentation model applied to a spectrometer, which consists of a collimating lens L10, a first micro-lens array, a planar array diaphragm, a second micro-lens array and a dispersion prism, wherein the collimating lens L10 collimates converging scene light so that the light entering the first micro-lens array is parallel light beams, the model utilizes the sub-lens focusing function of the micro-lens array to realize image segmentation of a second loss, replaces a mask used for image segmentation in the traditional snapshot imaging spectrometer, greatly improves the energy transmittance of an optical system, places the planar array diaphragm and the second micro-lens array behind the first micro-lens array to form a double micro-lens array model, and the center points of the sub-units of three optical elements are in one-to-one correspondence, so that the segmented micro-light beams respectively have corresponding diaphragms and collimating lens groups, so that all the micro-light beams are ensured to be parallel to be emitted in the same direction and enter the dispersion prism to complete dispersion, and spectrum bending is avoided.
In summary, the image segmentation model based on the double-microlens array provided by the invention can realize high-energy transmittance spectrum imaging, improve imaging quality, reduce spectrum distortion and avoid spectrum bending.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. The spectrum imaging method based on the double-microlens array segmentation is characterized by comprising the following steps of: the system comprises a first lens group G1, a second lens group G2 and a third lens group G3, wherein the incidence direction of light is sequentially arranged from left to right, scene information is collected by the G1, and a generated spectrum image is focused on an image surface by the G3 through collimation, segmentation and dispersion of the G2;
the first lens group G1 is a projection lens, and the first lens group G1 includes nine lenses, i.e., L1, L2, L3, L4, L5, L6, L7, L8, and L9;
the second lens group G2 is an image segmentation and dispersion module and consists of a collimating lens L10, a first micro-lens array, a planar array diaphragm, a second micro-lens array and a dispersion prism;
the third lens group G3 is a telecentric lens and consists of four lenses L11, L12, L13 and L14.
2. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: of the nine lenses in the first lens group G1, at least one lens has a refractive index nd of > 1.8 and at least one lens has an Abbe number Vdl of < 40.
3. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: the collimating lens L10 is disposed at the rear side of the projection lens, i.e. the first lens group G1, and is used for collimating the collected light and controlling the size of the light beam so that the light beam is parallel-incident into the first microlens array with a size slightly smaller than that of the microlens array.
4. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: the first micro-lens array divides light rays through a lens focusing function, images are cut in a low-energy-loss mode, and the second micro-lens array collimates micro-light beams focused by the first micro-lens array one by one so that the micro-light beams are emitted in parallel in the same direction.
5. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: the area array diaphragm is arranged at the back focal length of the first micro lens array and the front focal length of the second micro lens array, and the dispersion prism is used for dispersing light so as to generate a spectral image, is arranged at the rear side of the second micro lens array and controls the length of the spectral line together with the second micro lens array.
6. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: the dispersion prism is made of K9 and has a size of 40-40 mm; the first micro-lens array and the second micro-lens array are two-dimensional lens arrays with 15 x 15, and the diameter of each sub-lens is 500nm; the area array diaphragm is made of an opaque metal copper sheet through punching, the diameter of the sub-aperture is 100nm, and the center distance of the aperture is 500nm.
7. The spectral imaging method based on dual microlens array segmentation according to claim 1, wherein: the centers of the subunits of the first micro lens array, the area array diaphragm and the second micro lens array are in one-to-one correspondence, and the collimating lens L10, the first micro lens array, the area array diaphragm, the second micro lens array and the dispersion prism are coaxial.
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