Spectral correction device and method for pixel filter type multi-spectral detector

Abstract

The application discloses a kind of spectral correction device and method of pixel filter type multispectral detector, wherein: the direction of exit light of frequency adjustable light source is consistent with the main optical axis of beam shaping system, pixel filter type multispectral detector;Beam shaping system is used to collimate, expand beam and uniform illumination shaping processing to the exit light of frequency adjustable light source;After the exit light processed by beam shaping system, it is irradiated to pixel filter type multispectral detector, and response image is obtained;Processor constructs the spectral correction matrix of each macro-pixel according to the received response image, then calls spectral correction matrix to implement regularization correction to each macro-pixel, and realizes the spectral correction of multispectral image.The device and method can solve the problem of poor correction quality, inconsistent pixel response affecting imaging quality under low illumination in prior art, so as to obtain high-quality multispectral image.

Description

Technical Field

[0001] This invention relates to the field of multispectral imaging equipment technology, and in particular to a spectral correction device and method for a pixel-filter type multispectral detector. Background Technology

[0002] Multispectral imaging equipment can simultaneously acquire two-dimensional images and spectral radiation information of objects, and is widely used in military reconnaissance, crop classification and identification, remote sensing information model research, agricultural disaster prediction, and other fields. Multispectral imaging equipment based on pixel-filtering spectral imaging devices is characterized by its compact size, light weight, simple operation, and real-time imaging capabilities, making it suitable for application scenarios that traditional scanning multispectral imaging equipment cannot handle, such as multispectral video acquisition and high-speed target detection.

[0003] The working principle of pixel-filter-based multispectral detectors is to arrange filter arrays among multiple adjacent physical pixels, treating each as a spectral macropixel. Each filter has a different center wavelength, allowing spectral data across all spectral bands to be acquired in a single exposure. Compared to traditional scanning multispectral imaging, this method offers several advantages: integrating a single filter array onto a standard CMOS detector significantly reduces stray light, improving sensitivity and imaging speed; the use of CMOS technology significantly reduces costs and has the potential for large-scale manufacturing; and the wafer-level design of each pixel filter enables compact snapshot-style spectral acquisition, greatly increasing the camera's portability, flexibility, and ease of use, making it particularly suitable for applications with size and weight constraints, such as small UAV camouflage target reconnaissance and identification. However, the current main drawback of this imaging method is that, due to the inherent limitations of its working principle, spectral aliasing inevitably exists between each spectral band of the filter and adjacent bands, significantly impacting image quality. The more spectral bands the filter has, the greater the impact on image quality. Summary of the Invention

[0004] The purpose of this invention is to provide a spectral correction device and method for a pixel-filtering multispectral detector. This device and method can solve the problems of poor correction quality and inconsistent pixel response affecting imaging quality in the prior art under low illumination, thereby obtaining high-quality multispectral images.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A spectral correction device for a pixel-filter type multispectral detector, the device comprising a frequency-tunable light source, a beam shaping system, a pixel-filter type multispectral detector, and a processor, wherein:

[0007] The emitted light direction of the frequency-tunable light source is consistent with the main optical axis of the beam shaping system and the pixel filter type multispectral detector; the frequency-tunable light source is used to output monochromatic light with different center wavelengths and bandwidths, and the center wavelength and bandwidth of the emitted light are matched with the center wavelength and bandwidth of the filter on the pixel filter type multispectral detector;

[0008] The frequency-tunable light source is fixed in front of the beam shaping system, and the pixel-filtering multispectral detector is fixed behind the beam shaping system.

[0009] The beam shaping system is used to collimate, expand, and homogenize the emitted light from the frequency-tunable light source so that the light intensity irradiated on each pixel of the pixel-filtering multispectral detector is approximately the same.

[0010] The emitted light, processed by the beam shaping system, illuminates the pixel-filtered multispectral detector to obtain a response image.

[0011] The processor is connected to the pixel-filtered multispectral detector via a communication cable, and the pixel-filtered multispectral detector sends the obtained response image to the processor for processing.

[0012] The processor constructs a spectral correction matrix for each macropixel based on the received response image, and then calls the spectral correction matrix to perform regularization correction on each macropixel of the multispectral image to be corrected, thereby realizing the spectral correction of the multispectral image to be corrected.

[0013] A spectral correction method for a pixel-filter type multispectral detector, the method comprising:

[0014] Step 1: Use a frequency-tunable light source to output monochromatic light with different center wavelengths and bandwidths, and match the center wavelength and bandwidth of the emitted light with the center wavelength and bandwidth of the filter on the pixel filter type multispectral detector.

[0015] Step 2: Use a beam shaping system to collimate, expand, and homogenize the emitted light from the frequency-tunable light source.

[0016] Step 3: Use a pixel-filtering multispectral detector to acquire the response image of the outgoing light after it has been processed by the beam shaping system, and use the processor to construct the spectral correction matrix for each macropixel based on the response image;

[0017] Step 4: For the multispectral image to be corrected, the processor calls the spectral correction matrix to perform regularization correction on each macropixel of the multispectral image to be corrected, thereby realizing the spectral correction of the multispectral image to be corrected.

[0018] As can be seen from the technical solutions provided by the present invention, the above-mentioned device and method can solve the problems of poor correction quality and inconsistent pixel response affecting imaging quality in the prior art under low illumination, thereby obtaining high-quality multispectral images. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic diagram of the spectral correction device for a pixel-filter type multispectral detector provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of one implementation structure of the pixel-filtering multispectral detector 3 described in this invention;

[0022] Figure 3 This is a flowchart illustrating the method described in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, and do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0024] like Figure 1 This is a schematic diagram of the spectral correction device for a pixel-filtering multispectral detector provided in an embodiment of the present invention. The device includes a frequency-tunable light source 1, a beam shaping system 2, a pixel-filtering multispectral detector 3, and a processor 4, wherein:

[0025] The direction of the emitted light from the frequency-tunable light source 1 is consistent with the main optical axis of the beam shaping system 2 and the pixel filter type multispectral detector 3; the frequency-tunable light source 1 is used to output monochromatic light with different center wavelengths and bandwidths, and the center wavelength and bandwidth of the emitted light are matched with the center wavelength and bandwidth of the filter on the pixel filter type multispectral detector 3.

[0026] The frequency-tunable light source 1 is fixed in front of the beam shaping system 2, and the pixel-filtering multispectral detector 3 is fixed behind the beam shaping system 2;

[0027] The beam shaping system 2 is used to collimate, expand, and homogenize the emitted light from the frequency-tunable light source 1, so that the light intensity irradiated on each pixel of the pixel-filtering multispectral detector 3 is approximately the same; for example Figure 1 As shown, the beam shaping system 2 specifically includes an optical collimating lens group 21, an optical beam expander group 22, and a beam shaping lens group 23, wherein:

[0028] The optical collimating lens group 21 is used to collimate the emitted light from the frequency-tunable light source 1.

[0029] The optical beam expander group 22 is used to expand the outgoing light collimated by the optical collimator group 21.

[0030] The beam shaping lens group 23 is used to perform homogenization and illumination shaping processing on the outgoing light after the beam is expanded by the optical beam expander group 22.

[0031] The emitted light, after being processed by the beam shaping system 2, illuminates the pixel-filtering multispectral detector 3 to obtain a response image;

[0032] The processor 4 is connected to the pixel filter type multispectral detector 3 via a communication cable, and the pixel filter type multispectral detector 3 sends the obtained response image to the processor 4 for processing;

[0033] The processor 4 constructs a spectral correction matrix for each macropixel based on the received response image, and then calls the spectral correction matrix to perform regularization correction on each macropixel, thereby realizing spectral correction of the multispectral image. In a specific implementation, the processor 4 can be an ARM core board, containing an ARM processing core and a solid-state storage card. The functions of the processor can also be accomplished through interconnection between x86 or other architecture processors, FPGA chips or DSP chips with digital signal processing functions, and other hardware with equivalent functions.

[0034] In a specific implementation, the filters on the pixel-filtering multispectral detector 3 are arranged in a circular manner. Specifically, the detector is regarded as being composed of multiple identical macro pixels, each macro pixel containing multiple physical pixels of the detector, and the filters on all physical pixels have different center wavelengths.

[0035] All macropixels have the same filter arrangement.

[0036] For example, such as Figure 2 The diagram shown illustrates one implementation structure of the pixel-filtering multispectral detector 3 of this invention. In this example, the detector is a 4*4 cyclic coating multispectral detector, and its macro-pixel division is as follows: Figure 2As shown, the detector is divided into multiple identical macropixels. Within each macropixel, each physical pixel of the detector is coated with a filter film with a different center wavelength and bandwidth. Therefore, the spectral range received by each pixel is also different, and the raw data acquired by the detector is an image mixed with multiple spectral ranges.

[0037] In this embodiment, each macropixel of the detector has 16 physical pixels coated with filters of different center wavelengths, thus the final acquired multispectral image has 16 different spectral bands. In specific implementations, in addition to the above 16 spectral bands, other image sensors with 9, 25, or more spectral bands coated in the same or similar manner can also meet the requirements.

[0038] Based on the apparatus described in the embodiments of the present invention, the present invention also provides a spectral correction method for a pixel-filter type multispectral detector, such as... Figure 3 The diagram shown is a flowchart of the method described in an embodiment of the present invention. The method includes:

[0039] Step 1: Use a frequency-tunable light source to output monochromatic light with different center wavelengths and bandwidths, and match the center wavelength and bandwidth of the emitted light with the center wavelength and bandwidth of the filter on the pixel filter type multispectral detector.

[0040] Step 2: Use a beam shaping system to collimate, expand, and homogenize the emitted light from the frequency-tunable light source.

[0041] Step 3: Use a pixel-filtering multispectral detector to acquire the response image of the outgoing light after it has been processed by the beam shaping system, and use the processor to construct the spectral correction matrix for each macropixel based on the response image;

[0042] In this step, firstly, according to the specified number of center wavelengths and bandwidths of the filter film deposited on the pixel filter type multispectral detector, the frequency-tunable light source outputs monochromatic light with the corresponding number of center wavelengths and bandwidths in the arrangement order of the coated pixels; for example, if the coated filter film has 16 center wavelengths and bandwidths, then the frequency-tunable light source outputs monochromatic light with 16 center wavelengths and bandwidths in the arrangement order of the coated pixels.

[0043] Based on the specified number of center wavelengths and bandwidths of the filter film coated on the pixel-filtering multispectral detector, the frequency-tunable light source outputs monochromatic light with corresponding number of center wavelengths and bandwidths according to the arrangement order of the coated pixels.

[0044] For the k-th macropixel of a pixel-filtering multispectral detector, perform the following steps:

[0045] Let the original light intensity value received by the i-th physical pixel within the k-th macropixel during the j-th monochromatic light output of the frequency-tunable light source be a.(i,j) , 1≤i≤n; 1≤j≤n; n is the number of filter films coated on the pixel filter type multispectral detector; k is the macropixel number, the maximum value of which depends on the total number of physical pixels of the pixel filter type multispectral detector;

[0046] Based on the above settings, a spectral correction matrix A of dimension n*n is constructed. k Let the spectral correction matrix A k The element value in the i-th row and j-th column is equal to a. (i,j) ;

[0047] For spectral correction matrix A k Perform singular value decomposition to obtain singular values ​​σ. i Orthogonal row vector u i and orthogonal column vector v i As shown in the following formula:

[0048]

[0049] For the spectral correction matrix A k Each singular value σ i If the singular value σ i If the value is less than 1% of σ1, then let the singular value σ i It equals 0; σ1 is the first singular value, which is also the largest singular value.

[0050] Step 4: For the multispectral image to be corrected, the processor calls the spectral correction matrix to perform regularization correction on each macropixel of the multispectral image to be corrected, thereby realizing the spectral correction of the multispectral image to be corrected.

[0051] In this step, the spectral correction matrix is ​​invoked to perform regularization correction on each macro-pixel of the multispectral image to be corrected. The specific process of spectral correction of the multispectral image to be corrected is as follows:

[0052] For the k-th macropixel of a pixel-filtering multispectral detector, first set the light intensity value of the original multispectral image received by the i-th physical pixel within the k-th macropixel to be x. i 1≤i≤n, where n is the number of filter films coated on the pixel-filtering multispectral detector, and the original light intensity vector x is formed by the pixel arrangement order, where x=[x1,x2,…,x n ] T ;

[0053] Based on the singular value σ of the k-th macro-pixel i Orthogonal row vector u i and orthogonal column vector v iThe original light intensity vector x is spectrally corrected to obtain the corrected light intensity vector x'. The correction process uses the following formula:

[0054]

[0055] The elements of the corrected light intensity vector x' are extracted in sequence to obtain the spectral corrected image of the kth macro pixel;

[0056] By stitching together the spectral correction images of all macro pixels into a complete spectral correction image, spectral correction of multispectral images can be achieved.

[0057] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0058] In summary, the apparatus and method described in this embodiment of the invention can perform spectral correction on multispectral images acquired by a pixel-filtering multispectral detector. It can operate normally and obtain high-quality spectrally corrected images even in low-light environments. This method separates the spectral response acquisition process from the spectral correction calculation process. For a single pixel-filtering multispectral detector, only one spectral response acquisition process is required, significantly reducing the computational load required for the correction process and enabling high-speed correction of multispectral images. Furthermore, the spectral response acquisition process in this method only requires a small number of illuminations with different wavelengths using a frequency-tunable light source, eliminating the need for complete spectral curve measurements in minute steps, thus significantly improving the efficiency of spectral response acquisition.

[0059] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A spectral correction device for a pixel-filtered multi-spectral detector, characterized in that, The device comprises a frequency-adjustable light source, a light beam shaping system, a pixel-filtering multi-spectral detector and a processor, wherein: The light direction of the frequency-adjustable light source is consistent with the main optical axis of the light beam shaping system and the pixel-filtering multi-spectral detector; the frequency-adjustable light source is used to output monochromatic light with different center wavelengths and bandwidths, and the center wavelength and bandwidth of the outgoing light match the center wavelength and bandwidth of the filter on the pixel-filtering multi-spectral detector; The frequency-adjustable light source is fixed in front of the light beam shaping system, and the pixel-filtering multi-spectral detector is fixed behind the light beam shaping system; The light beam shaping system is used to collimate, expand and homogenize the outgoing light of the frequency-adjustable light source for shaping processing, so that the light intensity irradiated on each pixel of the pixel-filtering multi-spectral detector is substantially the same; The outgoing light processed by the light beam shaping system irradiates on the pixel-filtering multi-spectral detector to obtain a response image; The processor is connected with the pixel-filtering multi-spectral detector through a communication cable, and the pixel-filtering multi-spectral detector sends the obtained response image to the processor for processing; The processor constructs a spectral correction matrix of each macro-pixel according to the received response image, and then calls the spectral correction matrix to implement regularization correction on each macro-pixel of the multi-spectral image to be corrected, thereby realizing spectral correction of the multi-spectral image to be corrected.

2. The spectral correction device of the pixel-filtering multi-spectral detector according to claim 1, characterized in that: The filters on the pixel-filtering multi-spectral detector are arranged in a cyclic manner, specifically, the detector is regarded as being composed of a plurality of identical macro-pixels, each macro-pixel contains a plurality of physical pixels of the detector, and the filters on all the physical pixels have different center wavelengths; All the macro-pixels have the same filter arrangement manner.

3. The spectral correction device for pixel-filtered multi-spectral detector according to claim 1, characterized in that, The light beam shaping system specifically comprises an optical collimating mirror group, an optical expanding mirror group and a light beam shaping mirror group, wherein: The optical collimating mirror group is used to collimate the outgoing light of the frequency-adjustable light source; The optical expanding mirror group is used to expand the outgoing light collimated by the optical collimating mirror group; The light beam shaping mirror group is used to perform homogenization illumination shaping processing on the outgoing light expanded by the optical expanding mirror group.

4. A method of spectral correction of a pixel-filtered multi-spectral detector, characterized in that The method comprises: Step 1, outputting monochromatic light with different center wavelengths and bandwidths by using a frequency-adjustable light source, and matching the center wavelength and bandwidth of the outgoing light with the center wavelength and bandwidth of the filter on the pixel-filtering multi-spectral detector; Step 2, performing collimation, expansion and homogenization illumination shaping processing on the outgoing light of the frequency-adjustable light source by using a light beam shaping system; Step 3, obtaining a response image of the outgoing light processed by the light beam shaping system by using a pixel-filtering multi-spectral detector, and constructing a spectral correction matrix of each macro-pixel by a processor according to the response image; Step 4, for the to-be-corrected multi-spectral image, the processor calls the spectral correction matrix to implement regularized correction on each macro-pixel of the to-be-corrected multi-spectral image, so as to realize spectral correction of the to-be-corrected multi-spectral image.

5. The method of claim 4, wherein the method further comprises: In step 3: According to the specified number of center wavelengths and bandwidths of the filter film coated on the pixel filter type multi-spectral detector, the frequency adjustable light source respectively outputs monochromatic light corresponding to the number of center wavelengths and bandwidths in the arrangement order of the coated film pixels; For the kth macro-pixel of the pixel filter type multi-spectral detector, the following steps are performed: Set the original light intensity value received by the i-th physical pixel in the k-th macro-pixel when the j-th monochromatic light output of the frequency adjustable light source as a (i,j) , 1≤i≤n; 1≤j≤n; n is the number of filter films plated on the pixel filter type multi-spectral detector; k is the macro-pixel number, the maximum value of which depends on the total number of physical pixels of the pixel filter type multi-spectral detector; Based on the above settings, a spectral correction matrix A of n*n dimension is constructed k , the element value of the i-th row and j-th column of the spectral correction matrix A k is equal to a (i,j) ; A spectral correction matrix A k singular value decomposition to obtain singular values σ i orthogonal row vectors u i and orthogonal column vectors v i as follows: For each singular value σ k of the spectral correction matrix A i , if the value of the singular value σ i is less than 1% of σ1, the singular value σ i is set equal to 0; σ1 is the first singular value, that is, the largest singular value.

6. The method of claim 5, wherein the method further comprises: In step 4, the spectral correction matrix is called to implement regularized correction on each macro-pixel of the to-be-corrected multi-spectral image, and the process of realizing the spectral correction of the to-be-corrected multi-spectral image is as follows: For the kth macro-pixel of the pixel-filtering multi-spectral detector, first set the light intensity value of the original multi-spectral image received by the ith physical pixel in the kth macro-pixel as x i , 1≤i≤n, n is the number of filter films plated on the pixel-filtering multi-spectral detector, and is arranged in the order of the pixel to form an original light intensity vector x, wherein x=[x1,x2,…,xn] n ] T ; According to the singular value σ of the kth macro-pixel i , the orthogonal row vector u i , and the orthogonal column vector v i , the original light intensity vector x is corrected by spectral calculation to obtain the corrected light intensity vector x', and the correction process uses the following formula: The elements of the corrected light intensity vector x' are extracted in order to obtain the spectral correction image of the kth macro-pixel; The spectral correction images of all macro-pixels are spliced into a complete spectral correction image to realize the spectral correction of the multi-spectral image.

Images