Parasitic image correction method for large aperture spatiotemporal joint modulation interferometric imaging spectrometer

Abstract

The present invention belongs to a parasitic image correction method. In order to solve the current method of using a dimming film to block the parasitic image to reduce the influence of the parasitic image on the imaging quality, which will reduce the energy utilization rate, and it is difficult to meet the technical problem of high energy and high signal-to-noise ratio requirements when using a large-aperture spatiotemporal joint interference imaging spectrometer to obtain target information, a parasitic image correction method for a large-aperture spatiotemporal joint modulation interference imaging spectrometer is provided. Through the energy position relationship between a laser point and its corresponding parasitic image, the reflection center, reflection coefficient and parasitic image range of the interference imaging spectrometer can be accurately determined, so that the interference imaging spectrometer can accurately locate the parasitic image of its image. Then, the parasitic image correction can be completed by removing the corresponding parasitic image in the image, which provides a new idea for the parasitic image correction of the interference imaging spectrometer.

Description

Technical Field

[0001] The invention belongs to a parasitic image correction method, and in particular relates to a parasitic image correction method for a large-aperture spatiotemporal joint modulation interference imaging spectrometer. Background Art

[0002] Hyperspectral imagers use the principle of spatiotemporal joint modulation interference imaging spectroscopy to obtain images with interference information. Spatiotemporal joint modulation interference imaging spectroscopy has the inherent advantages of high throughput and multi-channels, but in the process of engineering implementation, it is limited by existing devices and process levels and still has its inherent difficulties and defects that need to be dealt with and overcome. The suppression and processing of parasitic images is one of the important issues.

[0003] The parasitic image is caused by the dielectric interface formed between the silicon surface of the detector and the air. The light transmittance enhancement process on the surface is insufficient, causing the light to be reflected by the detector, enter the interferometer again through the Fourier mirror, and then pass through the Fourier mirror again after being split by the interferometer, and enter the detector for the second time.

[0004] At present, dimming films are often used to block parasitic images to reduce their impact on imaging quality. However, this method will cause the incident energy to be weakened and reduce energy utilization. When a large-aperture spatiotemporal interferometric imaging spectrometer is actually used to obtain target information, it is difficult to meet its high energy and high signal-to-noise ratio requirements. Summary of the invention

[0005] The present invention aims to solve the technical problem that the current method of using a dimming film to block the parasitic image to reduce the influence of the parasitic image on the imaging quality will reduce the energy utilization rate and it is difficult to meet the high energy and high signal-to-noise ratio requirements when using a large aperture spatiotemporal joint interference imaging spectrometer to obtain target information. A parasitic image correction method for a large aperture spatiotemporal joint modulation interference imaging spectrometer is provided.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer is characterized in that it comprises the following steps:

[0008] S1, using a laser point to illuminate multiple positions close to zero optical path difference in the field of view of the interferometric imaging spectrometer, and collecting laser point images corresponding to each position respectively;

[0009] S2, obtaining the coordinates of the laser point image and the coordinates of the parasitic image corresponding to the laser point image through multi-threshold segmentation;

[0010] S3, determining the reflection center through the laser point image coordinates and the parasitic image coordinates;

[0011] S4, deducting the dark current value of the laser point image and obtaining the reflection coefficient;

[0012] S5, determining the parasitic image range through the laser point image and its parasitic image;

[0013] S6, obtaining a parasitic image corresponding to the interference spectrometer image according to the parasitic image range and the reflection center;

[0014] S7, according to the reflection coefficient and the parasitic image corresponding to the image obtained in step S6, the corresponding parasitic image is removed from the image obtained by the interference imaging spectrometer to complete the parasitic image correction.

[0015] Furthermore, step S3 specifically includes determining the reflection center by the mean of the laser point image coordinates and the parasitic image coordinates.

[0016] Furthermore, step S3 is specifically as follows:

[0017] S3.1, repeatedly performing dynamic threshold binary segmentation on the laser point image and the parasitic image by adjusting the binary segmentation threshold of the binary segmentation, until the difference between the number of pixels of the laser point image and the number of pixels of the parasitic image is greater than or equal to 0 and less than or equal to 5;

[0018] S3.2, respectively calculate the average value of the horizontal coordinates of each laser point image coordinate and each parasitic image coordinate, and the average value of the vertical coordinates of the laser point image coordinate and the parasitic image coordinate, respectively obtain the reflection center of each laser point image coordinate and each parasitic image coordinate, and take the average value of each reflection center (i center , j center ) as the reflection center, where i center is the mean value of the horizontal coordinates of each reflection center, j center is the mean ordinate of each reflection center.

[0019] Furthermore, in step S4, the obtaining of the reflection coefficient is specifically to obtain the reflection coefficient by using an average DN value of the laser point image and an average DN value of the parasitic image.

[0020] Further, in step S4, the reflection coefficient is obtained by using the laser point image DN value and the parasitic image DN value. Specifically, the reflection coefficient Coeff is obtained by the following formula: reflect :

[0021]

[0022] Among them, DN reflect is the average DN value of the parasitic image, DN dark is the average DN value of dark current, DN laser is the average DN value of the laser point image.

[0023] Furthermore, step S6 is specifically as follows:

[0024] The parasitic image region I located within the parasitic image range in the image obtained by the interference imaging spectrometer sub , symmetrically rotate about the reflection center to obtain the parasitic image I corresponding to the image gosht .

[0025] Further, in step S6, the parasitic image I corresponding to the image gosht The coordinates are (a1, b1):

[0026] a1=2*i center –a, b1=2*j center –b

[0027] Wherein, a is the abscissa of the image coordinates obtained by the interferometric imaging spectrometer, and b is the ordinate of the image coordinates obtained by the interferometric imaging spectrometer.

[0028] Furthermore, step S7 specifically includes removing the parasitic image from the image obtained by the interference imaging spectrometer by the following formula:

[0029] I clean =I sub -I gosht *Coeff reflect

[0030] I clean An image obtained by an interference imaging spectrometer after removing parasitic images;

[0031] Complete parasitic image correction.

[0032] Furthermore, step S5 specifically includes adjusting the laser spot irradiation position, taking the position of the laser spot image corresponding to the parasitic image just disappearing as the parasitic image boundary point, and adjusting the laser spot irradiation position multiple times to determine the parasitic image range according to multiple parasitic image boundary points.

[0033] Further, in step S1, the distance close to zero optical path difference is 25-35 pixels away from zero optical path difference.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The parasitic image correction method of the large-aperture spatiotemporal joint modulation interferometric imaging spectrometer of the present invention can accurately determine the reflection center, reflection coefficient and parasitic image range of the interferometric imaging spectrometer through the energy position relationship between the laser point and its corresponding parasitic image, thereby enabling the interferometric imaging spectrometer to accurately locate the parasitic image of its image. Then, the parasitic image correction can be completed by simply removing the corresponding parasitic image in the image, which provides a new idea for the parasitic image correction of the interferometric imaging spectrometer.

[0036] 2. In the present invention, the coordinates of the laser point image and the coordinates of the parasitic image corresponding to the laser point image are obtained based on threshold segmentation. In particular, by adjusting the binarization segmentation threshold of the binarization segmentation, the difference between the number of pixels of the laser point image and the number of pixels of the parasitic image is greater than or equal to 0 and less than 5. This dynamic threshold binarization segmentation method can accurately obtain the laser point image area and the corresponding parasitic image area, and make the laser point image and the corresponding parasitic image data consistent in size, thereby more accurately determining the reflection coefficient.

[0037] 3. The parasitic image correction method of the present invention can remove the parasitic image from the interference spectrometer with high accuracy and obtain high-precision interference data. The method is convenient and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of an embodiment of a parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer of the present invention;

[0039] Figure 2 A schematic diagram of laser points acquired by the interference imaging spectrometer in an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of a laser point image, a parasitic image and a reflection center in an embodiment of the present invention;

[0041] Figure 4 In the embodiment of the present invention, Figure 3 Corresponding reflection center coordinate relationship diagram;

[0042] Figure 5 It is the original interference pattern of the large aperture spatiotemporal joint modulation interferometric imaging spectrometer without removing the parasitic image;

[0043] Figure 6 Schematic diagram of parasitic image range in an embodiment of the present invention;

[0044] Figure 7 A parasitic image corresponding to an image obtained by the interference imaging spectrometer in an embodiment of the present invention;

[0045] Figure 8 This is the image obtained by the interference imaging spectrometer in the embodiment of the present invention after the parasitic image is removed. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0047] Due to the detector process of the large aperture space-time joint modulation interferometric imaging spectrometer, the light will be reflected by the detector, enter the interferometer twice through the Fourier mirror, and then pass through the Fourier mirror again after being split by the interferometer and enter the detector to produce a parasitic image, such as Figure 5 As shown, the original interference pattern of the large-aperture spatiotemporal joint modulation interferometric imaging spectrometer without removing the parasitic image will cause the scene information to be superimposed on the interference pattern, resulting in distortion of the obtained interference data.

[0048] The parasitic image correction method of the large aperture spatiotemporal joint modulation interferometric imaging spectrometer provided by the present invention is mainly aimed at correcting the parasitic image formed by the reflected light on the detector surface. The symmetry center of the parasitic image and the actual image is mainly obtained by using the laser symmetric point data, and then the reflection coefficient is obtained according to the laser point energy relationship, and then the parasitic image range is determined by the laser point image and its parasitic image, and finally, the parasitic image in the image obtained by the interferometric imaging spectrometer is determined, and then the parasitic image is removed therefrom to obtain the final corrected result.

[0049] like Figure 1 As shown, the correction method of the present invention is described in detail by taking the following embodiments as examples:

[0050] Step 1: Data Collection:

[0051] First, turn on the large aperture spatiotemporal joint modulation interferometric imaging spectrometer, wait for the instrument to stabilize (about five minutes later), and collect dark current data. Then, when the laser spot is irradiated near the zero optical path difference in the field of view of the interferometric imaging spectrometer, generally 30 pixels away from the zero optical path difference, select 6 points in the spatial dimension, located above and below the zero optical path difference, and obtain 6 laser point images. The positions of these 6 laser points are as follows: Figure 2 The imaging spectrometer is used to collect the laser point data at the corresponding position and obtain the parasitic image data at the symmetrical position at the same time.

[0052] Step 2: Calculation of reflection center:

[0053] Firstly, the laser point image and the parasitic image are binarized with dynamic threshold, and the number of pixels of the corresponding points of the segmented laser point image and the parasitic image is calculated. If the number of pixels of the parasitic image is less than that of the laser point image, the binary segmentation threshold of the laser point is increased until the difference between the number of laser point pixels and the number of pixels of the symmetrical reverse image points is within 5.

[0054] Then, the average values ​​of the horizontal coordinates of the laser point image coordinates and the parasitic image coordinates are calculated. center , and the ordinate average j of the laser point image coordinates and parasitic image coordinates center , with (i center , j center ) as the reflection center, such as Figure 3As shown, A is the parasitic image, C is the laser point image, and B is the reflection center. The specific coordinate position relationship is as follows Figure 4 When actually determining the reflection center, six reflection centers can be obtained through six laser point images, and finally the average of the six reflection centers is taken as the final reflection center.

[0055] Step 3: Calculate the reflection coefficient:

[0056] First, the dark current value is deducted from the laser point image. Then, the reflection coefficient Coeff is obtained by dividing the average DN value of the parasitic image by the average DN value of the laser point image. reflect , the calculation formula is as follows:

[0057]

[0058] Among them, DN reflect Indicates the average DN value of the parasitic image, DN dark Indicates the average DN value of dark current, DN laser It represents the average DN value of the laser spot image. In this embodiment, the reflection coefficient is 0.056.

[0059] Step 4: Determine the parasitic image range

[0060] The laser spot image and its parasitic image are used to determine Figure 6 The range of the parasitic image shown in the white box can be determined by adjusting the distance between the laser point and the reflection center point. When the laser point is irradiated at a certain position of the interference pattern, no parasitic image can be seen on the interference pattern. This is the boundary point of the parasitic image. The range of the parasitic image can be determined by adjusting the position of the laser point multiple times.

[0061] The aforementioned steps 1 to 4 are all preparatory work before formally performing parasitic image correction on the image obtained by the interferometric imaging spectrometer. The subsequent steps 5 and 6 are based on the aforementioned preparatory work to perform parasitic image correction on the image obtained by the interferometric imaging spectrometer.

[0062] Step 5: Obtain the parasitic image

[0063] The parasitic image region I in the parasitic image range in the image obtained by the interference imaging spectrometer sub , symmetrically rotate about the reflection center to obtain the parasitic image I corresponding to the image gosht , (a, b) is the parasitic image area I sub The coordinates of the parasitic image I are (a1, b1) gosht Coordinates of a1=2*i center –a, b1=2*j center –b.

[0064] Get as Figure 7 As shown, Figure 5 The corresponding parasitic image.

[0065] Step 6: Eliminate parasitic images from the image obtained by the interferometric imaging spectrometer

[0066] Remove the parasitic image obtained in step 5 from the image obtained by the interferometric imaging spectrometer:

[0067] I clean (i,j)=I sub (i,j)-I gosht (i,j)*Coeff reflect

[0068] Among them, I clean The image obtained by the interference imaging spectrometer is the image after the parasitic image is removed.

[0069] After parasitic image correction, we finally get Figure 8 High quality images shown.

[0070] pass Figure 8 and Figure 5 By comparison, it can be concluded that the parasitic image correction method of the large-aperture spatiotemporal joint modulation interferometric imaging spectrometer of the present invention can greatly reduce the influence of parasitic images, and the visual quality of the corrected interference data is significantly improved.

[0071] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer, characterized in that: The following steps are involved: S1, using a laser point to illuminate multiple positions close to zero optical path difference in the field of view of the interferometric imaging spectrometer, and collecting laser point images corresponding to each position respectively; S2, obtaining the coordinates of the laser point image and the coordinates of the parasitic image corresponding to the laser point image through multi-threshold segmentation; S3, determining the reflection center through the laser point image coordinates and the parasitic image coordinates; S4, deducting the dark current value of the laser point image and obtaining the reflection coefficient; S5, determining the parasitic image range through the laser point image and its parasitic image; S6, for the parasitic image region I located within the parasitic image range in the image obtained by the interference imaging spectrometer sub , symmetrically rotate about the reflection center to obtain the parasitic image I corresponding to the image gosht ; S7, remove the parasitic image from the image obtained by the interferometric imaging spectrometer by the following formula: I clean =I sub -i gosht *Coeff reflect I clean An image obtained by an interference imaging spectrometer after removing parasitic images; Complete parasitic image correction.

2. The parasitic image correction method of the large aperture spatiotemporal joint modulation interferometric imaging spectrometer according to claim 1, characterized in that: Step S3 specifically includes determining the reflection center by the mean of the laser point image coordinates and the parasitic image coordinates.

3. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer according to claim 2, characterized in that: Step S3 is specifically as follows: S3.1, repeatedly performing dynamic threshold binary segmentation on the laser point image and the parasitic image by adjusting the binary segmentation threshold of the binary segmentation, until the difference between the number of pixels of the laser point image and the number of pixels of the parasitic image is greater than or equal to 0 and less than or equal to 5; S3.2, respectively calculate the average value of the horizontal coordinates of each laser point image coordinate and each parasitic image coordinate, and the average value of the vertical coordinates of the laser point image coordinate and the parasitic image coordinate, respectively obtain the reflection center of each laser point image coordinate and each parasitic image coordinate, and take the average value of each reflection center (i center , j center ) as the reflection center, where i center is the mean value of the horizontal coordinates of each reflection center, j center is the mean ordinate of each reflection center.

4. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer as claimed in claim 3, characterized in that: In step S4, the reflection coefficient is obtained by using the average DN value of the laser point image and the average DN value of the parasitic image.

5. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer as claimed in claim 4, characterized in that: In step S4, the reflection coefficient is obtained by using the laser point image DN value and the parasitic image DN value. Specifically, the reflection coefficient Coeff is obtained by the following formula: reflect : Among them, DN reflect is the average DN value of the parasitic image, DN dark is the average DN value of dark current, DN laser is the average DN value of the laser point image.

6. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer as claimed in claim 5, characterized in that: In step S6, the parasitic image I corresponding to the image gosht The coordinates are (a1, b1): a1=2*i center –a, b1=2*j center –b Wherein, a is the abscissa of the image coordinates obtained by the interferometric imaging spectrometer, and b is the ordinate of the image coordinates obtained by the interferometric imaging spectrometer.

7. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer as claimed in claim 6, characterized in that: Specifically, step S5 adjusts the laser spot irradiation position, takes the position of the laser spot image corresponding to the parasitic image just disappearing as the parasitic image boundary point, and determines the parasitic image range according to multiple parasitic image boundary points by adjusting the laser spot irradiation position multiple times.

8. The parasitic image correction method for a large aperture spatiotemporal joint modulation interferometric imaging spectrometer as claimed in claim 7, characterized in that: In step S1, the distance close to zero optical path difference is 25-35 pixels away from zero optical path difference.

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