A multispectral light filtering imaging method

Abstract

The application discloses a multispectral filter imaging method, and belongs to the field of multispectral imaging technology in aviation and spaceflight. The method comprises the following steps: step 1, filter 2 coating and spectral band coding; step 2, the filter 2 moves in the imaging light path 1 according to a rule; step 3, planar array focal plane imaging; step 4, the planar array focal plane imaging image is segmented according to spectral bands; and step 5, the segmented image is synthesized according to spectral bands. The above steps are cycled to quickly obtain multispectral images of different targets. The application has the advantages of simplicity, reliability, a large number of spectral bands and unlimited expansion, and can be used in all imaging fields using planar array imaging and requiring spectral bands.

Description

Technical Field

[0001] This invention relates to the field of aviation and aerospace multispectral imaging technology, specifically to a multispectral filtering imaging method. Background Technology

[0002] A filter mechanism is a key component for realizing multispectral imaging in aerial and space-based joystick cameras. It filters the light entering the optical path by switching filter elements, allowing light of specific spectral bands to pass through, and ultimately realizes imaging of multiple spectral bands to obtain the spectral information of the observed target.

[0003] With the rapid development of the aviation and aerospace field, especially the technological breakthroughs in ultra-large aperture space remote sensors, the application scenarios of space remote sensors are becoming increasingly complex, the degree of subdivision of optical channels and optical spectrum is becoming higher and higher, the number of filters is increasing, and their size is also increasing.

[0004] Currently, multispectral filtering mechanisms in optical remote sensors often use a turntable design, such as the structure disclosed in Chinese invention patent application CN108957673A. Its advantages include simple structure, single-motor drive, and high reliability. However, its disadvantages are equally apparent. For large-aperture space remote sensors with urgent needs for large-size, multispectral filtering imaging, its size is too large to be arranged, ultimately limiting its application. While array-type filtering mechanisms, such as the structure disclosed in Chinese invention patent application CN112485878A, avoid these structural drawbacks, they require multiple power sources, have complex control systems, and are not highly reliable. Moreover, for more spectral bands (more than 10), their size remains large, and integration is equally difficult.

[0005] Therefore, based on the above-mentioned technical problems, those skilled in the art urgently need to develop a simple, reliable, and efficient multispectral filtering imaging method. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multi-spectral filtering imaging method that is simple, reliable, and efficient. This method is used to complete multi-spectral imaging of a space optical camera array imaging system and meet the needs of obtaining images of different spectral bands.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention discloses a multi-spectral filtering imaging method, which includes the following steps:

[0009] Step 1: Filter Coating and Spectral Encoding:

[0010] The filter consists of multiple local filtering zones distributed in a regular pattern, and each local filtering zone can filter a single spectrum of light passing through it.

[0011] Step 2: The filter moves in a regular pattern within the imaging optical path:

[0012] The filter moves within the imaging optical path according to a set motion law;

[0013] Step 3: Area array focal plane imaging:

[0014] The imaging optical path forms an image at the focal plane of the array after passing through the filter, and the image acquisition device acquires images S1-S2 containing information of different spectral bands. n The image subscript represents the order in which the images are acquired, and n represents the number of images to be acquired in one loop.

[0015] Step 4: Segment the focal plane imaging image of the area array according to spectral bands:

[0016] Image S containing information from different spectral bands i From single-band image S ij Mixed spectral band image H ij Composition, in which S ij Let S represent the image of single spectral band j during the i-th imaging process. i The single-spectral image S in ij Extract and record the spatial location of the image.

[0017] Step 5: Synthesize the segmented images according to spectral bands:

[0018] Multiple images S1—S n Extracted single-spectral image S ij By combining the images, an area array image of spectral band j can be obtained. By combining all the required single-band images, area array images of multiple spectral bands can be obtained within one imaging cycle.

[0019] Step 6: Repeat steps 2 to 5 to obtain multispectral imaging information for different targets.

[0020] In the above technical solution, the multi-band filtering imaging method provided by the present invention has the following advantages: using this method for multi-band area array imaging can significantly reduce the complexity of the filtering mechanism and improve its reliability; it can significantly reduce the size and weight of the mechanism, shorten the mission development cycle, and reduce development costs; the mechanism is not affected by the imaging spectral band, and using the same filtering mechanism, multispectral and even hyperspectral imaging can be achieved, with no upper limit on the theoretical imaging spectral band and a wide range of applications; by setting the motion law and imaging strategy of the filtering mechanism, imaging modes such as staring and short exposure can be achieved, which is highly functional; the present invention can be used in all imaging fields that utilize area array imaging and require specific spectral bands. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0022] Figure 1 This is a schematic diagram of the filtering process in a multi-band filtering imaging method disclosed in this invention;

[0023] Figure 2 This is a schematic diagram of the filter spectral bands in a multi-band filtering imaging method disclosed in this invention;

[0024] Figure 3 This is a schematic diagram showing the position of the light-transmitting window of the filter in the multi-spectral filtering imaging method disclosed in this invention (in its initial position);

[0025] Figure 4 This is a schematic diagram showing the position of the filter after the first image of the filter has been acquired in a multi-spectral filtering imaging method disclosed in this invention.

[0026] Figure 5 This is a schematic diagram showing the position of the filter after the i-th image of the filter has been acquired in a multi-spectral filtering imaging method disclosed in this invention.

[0027] Figure 6 This is a schematic diagram of spectral information in all n (n=6) images in one imaging cycle of a multi-spectral band filtering imaging method disclosed in this invention;

[0028] Figure 7 This is a schematic diagram illustrating the segmentation of all n (n=6) images in one imaging cycle according to spectral bands in a multi-band filtering imaging method disclosed in this invention;

[0029] Figure 8 This is a schematic diagram illustrating the synthesis of segmented images within one imaging cycle according to spectral bands in a multi-band filtering imaging method disclosed in this invention;

[0030] Figure 9 This is a flowchart of a multi-spectral filtering imaging method disclosed in this invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] In the figure: 1. Imaging optical path; 2. Filter; 2-1. Local filtering area; 3. Imaging device; 4. Light transmission window; 5. Spectral aliasing imaging area. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] See Figure 1-9 As shown;

[0035] A multi-spectral band filtering imaging method is invented, the method comprising the following steps:

[0036] Step 1: Coating and spectral encoding of filter 2:

[0037] The filter 2 consists of multiple locally filtered regions 2-1 distributed in a regular pattern. These locally filtered regions 2-1 can filter a single spectrum of light passing through them through a coating process. For details, see [link to documentation]. Figure 1 As shown, each elongated area is a local filtering area 2-1, meaning that the local filtering areas 2-1 on the filter 2 are distributed sequentially and closely together in a regular pattern.

[0038] Step 2: Filter 2 moves regularly within imaging optical path 1:

[0039] The filter 2 moves within the imaging optical path 1 according to a set motion law. Specifically, the filtering efficiency is highest when the motion direction is perpendicular to the spectral bands, and it has no effect when it is parallel. Of course, the motion direction of the filter 2 can also be set to be non-perpendicular to the spectral array.

[0040] Step 3: Area array focal plane imaging:

[0041] Imaging optical path 1 passes through filter 2 and is imaged at the focal plane of the array by imaging device 3. The image acquisition device acquires images S1-S2 containing information in different spectral bands. n The image subscript represents the order of acquisition, and n represents the minimum number of images within one imaging cycle.

[0042] Step 4: Segment the focal plane image of the area array according to spectral bands:

[0043] Image S containing information from different spectral bands i From single-band image S ij Mixed spectral band image H ij Composition, in which S ij Let S represent the image of single spectral band j during the i-th imaging process. i The single-spectral image S in ij Extract and record the spatial location of the image, where H ij This represents the image containing both spectral band j and spectral band j-1 during the i-th imaging process. The position of this image corresponds to the area on the filter where the spatial positions of spectral band j and spectral band j-1 intersect. This varies depending on different system parameters and different filter motion laws H. ij The ranges are not the same;

[0044] Step 5: Synthesize the segmented images according to spectral bands:

[0045] Multiple images S1—S n Extracted single-spectral image S ij By combining the images, an area array image of spectral band j can be obtained. By combining all the required single-band images, area array images of multiple spectral bands can be obtained within one imaging cycle.

[0046] Step 6: Repeat steps 2 to 5 to obtain multispectral imaging information for different targets. Specific implementation method one;

[0048] Figure 1 This is a schematic diagram of a light filter. Filter 2 is coated with a strip-shaped filter film (all filter films have the same width l and equal length), which can transmit only a specific spectral band (B). i The effect of light, Figure 2 This is a schematic diagram of the filter's spectral segments, where n is the total number of spectral segments. The order of the spectral segments can be encoded according to actual usage requirements. In a specific embodiment, filter 2 is encoded as a 3-segment (B1, B2, B3) cyclic encoding. The direction of movement of filter 2 is perpendicular to the spectral segment encoding direction, and the movement of filter 2 is uniform with a speed of v.

[0049] Figure 3 This is a schematic diagram showing the position of the light-transmitting window 4 of the filter (in its initial position). Using the staring imaging mode, the imaging time is ΔT = ΔS / v. Figure 4 This is a schematic diagram showing the position of the filter after the first image of the filter has been acquired. Figure 5 This is a schematic diagram showing the position of the filter after the i-th image of the filter has been acquired. Thus, during the uniform movement of filter 2, there are a single spectral band image with a width of s = l - ΔS and a mixed spectral band image with a width of ΔS on the imaging focal plane (e.g., ...). Figure 6 A schematic diagram of spectral information in all n (n=6) images in one imaging cycle. (For ease of understanding...) Figures 4 to 7 In the middle, ΔS = l / 2. After one cycle of staring imaging (when imaging ΔS = l / 2 can obtain images of all spectral bands of the imaging target, the number of imaging cycles is 6), all single spectral band images are segmented (e.g., ...). Figure 7 As shown), the images are then synthesized according to spectral bands. Figure 8 (This refers to the synthesized single-band image). In practical applications, ΔS can be slightly less than 1 / 2, so that there is some overlap when segmenting the image by spectral band, making image synthesis easier. Although the specific embodiment is described using 3 spectral bands, the method described in this invention can infinitely expand the spectral bands, and the spectral band array can also be used in an irregular manner.

[0050] When an imaging cycle is completed, the filter 2 can be moved in its original direction to obtain a multi-spectral image for the next imaging cycle, or the direction of movement can be reversed to obtain full-spectrum information after one imaging cycle. When this imaging method is used, the filter mechanism has the smallest structural size and the highest integration.

[0051] As can be seen from the above introduction, the staring imaging time is related to the movement speed of filter 2. Therefore, the imaging time can be extended by reducing the movement speed without increasing the width of the filter film on filter 2. Thus, the filter film can be made very narrow, making the filtering mechanism very compact and allowing for a large number of spectral bands. Moreover, it is easy to expand and has a low cost. Specific implementation method two;

[0053] This embodiment is basically the same as Embodiment 1, and will not be described in detail here. The difference is that the motion law of the filter 2 does not adopt uniform motion, but adopts an intermittent motion mode of motion and stop. When it moves once, it moves 1, and then stops to perform imaging. This mode has the highest time utilization. Specific implementation method three;

[0055] This embodiment is basically the same as Embodiment 1, and will not be described in detail here. The difference is that the filter 2 uses two-dimensional filter coding and moves in a certain way in the horizontal and vertical directions to obtain higher spectral imaging efficiency. Testing the filter film on the filter 2 requires the use of a rectangular grid two-dimensional array, and the image processing difficulty is also very high. Specific implementation method four;

[0057] This embodiment is basically the same as Embodiment 1, and will not be described in detail here. The difference is that the filter 2 uses a reflective filter film. The method described in this invention can also be applied to reflective filter optical paths.

[0058] In the above technical solution, the multi-band filtering imaging method provided by the present invention has the following advantages: using this method for multi-band area array imaging can significantly reduce the complexity of the filtering mechanism and improve its reliability; it can significantly reduce the size and weight of the mechanism, shorten the mission development cycle, and reduce development costs; the mechanism is not affected by the imaging spectral band, and using the same filtering mechanism, multispectral and even hyperspectral imaging can be achieved, with no upper limit on the theoretical imaging spectral band and a wide range of applications; by setting the motion law and imaging strategy of the filtering mechanism, imaging modes such as staring and short exposure can be achieved, which is highly functional; the present invention can be used in all imaging fields that utilize area array imaging and require specific spectral bands.

[0059] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A multi-spectral band filtering imaging method, characterized in that, The method includes the following steps: Step 1: Filter (2) Coating and Spectral Encoding: The filter (2) is composed of multiple local filtering zones (2-1) distributed in a regular pattern, and the local filtering zones (2-1) can filter a single spectrum of light passing through. Step 2: The filter (2) moves regularly within the imaging optical path (1): The filter (2) moves within the imaging optical path (1) according to a set motion law. The direction of motion of the filter (2) is perpendicular to the spectral encoding direction. The motion law of the filter (2) is uniform motion with a motion speed of v. Step 3: Area array focal plane imaging: The imaging optical path (1) forms an image at the focal plane of the array after passing through the filter (2), and the image acquisition device acquires images S1-S2 containing information of different spectral bands. n The image subscripts represent the order in which the images were acquired, and n represents the number of images to be acquired in one loop. Using gaze imaging mode, the imaging time is... , where ∆s is the displacement of the filter during the acquisition of a single image within one imaging cycle; During the uniform movement of filter (2), a width of [missing information] exists on the imaging focal plane. A single spectral band image and a width of Mixed spectral band images; Step 4: Segment the focal plane imaging image of the area array according to spectral bands: Image S containing information from different spectral bands i From single-band image S ij Mixed spectral band image H ij Composition, in which S ij Let S represent the image of single spectral band j during the i-th imaging process. i The single-spectral image S in ij Extract and record the spatial location of the image; Step 5: Synthesize the segmented images according to spectral bands: Multiple images S1—S n Extracted single-spectral image S ij By combining the images, an array image of spectral band j can be obtained. By combining all the required single-band images, array images of multiple spectral bands can be obtained within one imaging cycle. Step 6: Repeat steps 2 to 5 to obtain multispectral imaging information for different targets.

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