CN112924028B - Light field polarization imaging detection system for sea surface oil spill - Google Patents

Light field polarization imaging detection system for sea surface oil spill Download PDF

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CN112924028B
CN112924028B CN202110098224.0A CN202110098224A CN112924028B CN 112924028 B CN112924028 B CN 112924028B CN 202110098224 A CN202110098224 A CN 202110098224A CN 112924028 B CN112924028 B CN 112924028B
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light field
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polarization
information
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CN112924028A (en
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李英超
金钊
付强
姜会林
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Changchun University of Science and Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28Investigating the spectrum
    • G01J3/2823Imaging spectrometer
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12Generating the spectrum; Monochromators
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28Investigating the spectrum
    • G01J3/447Polarisation spectrometry
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/12Generating the spectrum; Monochromators
    • G01J2003/1291Generating the spectrum; Monochromators polarised, birefringent

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

A light field polarization imaging detection system for sea surface spilled oil belongs to the technical field of photoelectric imaging, and aims to solve the problem that the prior art is not suitable for real-time detection of sea surface dynamic scenes; the light field polarization information acquisition subsystem comprises a light sheet, a prepositive optical imaging main lens group, a micro-lens array and a micro-polarizer array imaging detector, wherein the section light sheet, the prepositive optical imaging main lens group, the micro-lens array and the micro-polarizer array imaging detector are coaxially arranged, the micro-lens array is positioned at the focal plane position of the prepositive optical imaging main lens group, and the micro-polarizer array imaging unit is positioned at the focal plane position of the micro-lens array; the snapshot imaging of sea surface spilled oil is realized on an onboard high-speed platform by utilizing the digital focusing function of the light field camera, and the real-time high-precision acquisition of the spilled oil image is realized; the polarization imaging can improve the contrast of the oil spill image and improve the resolution capability of different oil types.

Description

Light field polarization imaging detection system for sea surface oil spill
Technical Field
The invention belongs to the technical field of photoelectric imaging, and particularly relates to a light field polarization imaging detection system for sea surface oil spill.
Background
In the petroleum development and transportation process, sea oil spill events frequently occur due to natural factors or transport ship faults and the like, and the marine ecological environment is seriously influenced. After oil leaks, it is necessary to know the location of the oil leak, the type of spilled oil, and the extent of diffusion in order to specify appropriate countermeasures.
The airborne remote sensing technology is widely applied to the field of sea surface target remote sensing detection due to the advantages of miniaturization and convenience. However, the background environment of the ocean has complexity and specificity, and the problems of complex sea surface illumination, poor contrast of the target environment, solar radiation flare interference and the like exist. The traditional airborne detection imaging system mainly comprises intensity imaging and push-broom hyperspectral imaging, the real-time performance of the system and the contrast of the acquired images are poor, aliasing among spectral images can be caused under the flying motion state, and therefore the requirements for acquiring real-time high-quality information of ocean targets are difficult to meet. The polarization imaging technology can inhibit sea flare and enhance the contrast of images, but the current rotary polarizer type optical imaging system developed in China has poor instantaneity; the amplitude-division type polarization system has large volume and weight and low light energy utilization rate; and therefore is not suitable for real-time detection of sea surface dynamic scenes.
At present, the technologies of traditional optical intensity imaging, hyperspectral imaging, polarization imaging and the like have advantages and disadvantages in ocean typical target detection, and if multidimensional information is fused, the advantages of various detection means can be complemented, so that the detection and identification performances of ocean typical targets are improved.
As an emerging technology which is rapidly developed in recent years, the light field imaging technology can record information such as the intensity, the direction and the like of target radiation at the same time, and has a plurality of advantages which cannot be achieved by traditional imaging equipment. However, many information components such as polarization and wavelength are still underutilized in the current research work on light field imaging.
Disclosure of Invention
The invention provides a light field polarization imaging detection system for sea surface spilled oil, which aims to solve the problem that the prior art is not suitable for real-time detection of sea surface dynamic scenes, can realize simultaneous acquisition of light field and polarization multidimensional information of each region of a target to be detected through single exposure of a main optical system, and is a beneficial supplement to traditional imaging detection of sea surface targets. On one hand, the snapshot imaging of sea surface spilled oil is realized on an onboard high-speed platform by utilizing the digital focusing function of the light field camera, and the real-time high-precision acquisition of the spilled oil image is realized; on the other hand, polarization imaging can improve contrast of oil spill images and improve resolution capability of different oil types.
The technical scheme for solving the technical problems is as follows:
the light field polarization imaging detection system for sea surface oil spill is characterized by comprising a light field polarization information acquisition subsystem and an information processing subsystem; the light field polarization information acquisition subsystem comprises a light sheet, a prepositive optical imaging main lens group, a micro-lens array and a micro-polarizer array imaging detector, wherein the section light sheet, the prepositive optical imaging main lens group, the micro-lens array and the micro-polarizer array imaging detector are coaxially arranged, the micro-lens array is positioned at the focal plane position of the prepositive optical imaging main lens group, and the micro-polarizer array imaging unit is positioned at the focal plane position of the micro-lens array;
natural light reflected by the target spilled oil enters a front optical imaging main lens group through an optical filter, is focused and imaged through the front optical imaging main lens group, and then light fields in different directions are secondarily imaged through all micro lenses in a micro lens array, and finally the light fields are recorded on a micro polarizer array imaging detector to complete real-time acquisition of polarization information of the light field of the target spilled oil; then inputting the acquired information into an image acquisition unit, and inputting the acquired information into a calculation processing unit by the image acquisition unit to process the polarized image information of the oil spilling light field; the computing processing unit extracts corresponding pixels according to calibration data of a camera in the light field polarization information acquisition subsystem, and can realize unmixing of the light field information and the polarization information through corresponding computation; and then detecting and identifying the extracted light field information features and polarization information features, and finally obtaining identification results of different oil types according to the comparison of gray values in the image information and displaying the identification results by an image display unit.
The invention has the beneficial effects that: aiming at the problems that the distribution range of sea surface spilled oil is wide, and the polarization intensity characteristic of different areas is difficult to detect due to wave vibration, the invention discloses a light field polarization detection imaging system based on the combination of a micro lens array and a micro polarization array, and the light field information and the polarization information of the sea surface spilled oil can be simultaneously obtained by utilizing a single main optical system, thereby being beneficial to the traditional imaging detection. On one hand, the light field imaging system has a digital focusing function, so that the object to be measured can be photographed before being focused, and good instantaneity is achieved. Compared with the traditional marine target airborne imaging detection system, the system can remarkably improve the image resolution at the defocusing position and the equivalent focal depth can be improved by 7 times, so that the system can effectively solve the defocusing problem caused by inaccurate focusing of an optical imaging system in the high-speed flight process of an airborne platform; on the other hand, polarization imaging can improve image contrast compared with conventional imaging under the characteristic spectrum of the target. Experimental results show that compared with intensity imaging, the contrast between polarized images and seawater backgrounds for different oil seeds can be improved by 30% -70%. In addition, the polarization imaging can also inhibit water surface flare formed by specular reflection of the seawater surface on sunlight, so that the problem of contrast distortion caused by local excessive brightness of an image is solved, and the discrimination capability of an airborne remote sensing system on target oil spill detection is improved.
Drawings
FIG. 1 is a schematic block diagram of a light field polarization imaging detection system for sea surface oil spill.
The system comprises a 1-light field polarization information acquisition subsystem, 10-target oil spill to be detected, 11-optical filters, 12-front optical imaging main lens groups, 13-micro lens arrays and 14-micro polarizer array imaging detectors; the system comprises a 2-information processing subsystem, a 21-image acquisition unit, a 22-calculation processing unit and a 23-image display unit.
Fig. 2 is a schematic structural diagram of a light field polarization information acquisition subsystem according to the present invention.
FIG. 3 is a schematic diagram of a micropolarizer array imaging detector in accordance with the present invention.
FIG. 4 is a flow chart of the light field polarization imaging detection system for sea surface oil spill according to the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and detailed description.
As shown in fig. 1, a light field polarization imaging detection system for sea surface oil spill consists of a light field polarization information acquisition subsystem 1 and an information processing subsystem 2.
As shown in fig. 2, the light field polarization information acquisition subsystem 1 includes an optical sheet 11, a front optical imaging main lens group 12, a microlens array 13, and a micropolarizer array imaging detector 14. The segment filter 11, the front optical imaging main lens group 12, the micro lens array 13 and the micro polarizer array imaging detector 14 are coaxially arranged, the micro lens array 13 is positioned at the focal plane position of the front optical imaging main lens group 12, and the micro polarizer array imaging detector 14 is positioned at the focal plane position of the micro lens array 13.
In actual operation, natural light reflected by the target spilled oil enters the front optical imaging main lens group 12 through the optical filter 11, is focused and imaged through the front optical imaging main lens group 12, then is secondarily imaged by all the micro lenses in the micro lens array 13 to light fields in different directions, and finally is recorded on the micro polarizer array imaging detector 14 to complete real-time acquisition of polarization information of the target light field.
The applicable wave band of the optical filter 11 is 650nm-1000nm, and the contrast ratio of the optical filter to the oil spilling polarized imaging image is higher in the wave band.
The microlens array 13 is formed by arranging a plurality of microlenses with the same size and focal length, and each microlens corresponds to a detector pixel in a fixed area range of the rear micro-polarizer array imaging detector 14.
As shown in fig. 3, the imaging principle of the micro-polarizer array imaging detector 14. The micro-polarizer array imaging detector 14 realizes the integration of the micro-polarizer array and the focal plane by directly photoetching a metal grating on a detector pixel, and the unit size of the micro-polarizer array is consistent with the pixel size of a photosensitive chip to be integrated. Four micro-polarizers of 0 degree, 45 degree, 90 degree and 135 degree in front of the focal plane are matched one by one respectively in a mode that every four detector pixels form a 2X 2 polarization super pixel, and four polarization information responses of angles can be acquired simultaneously in each super pixel, so that four images with different polarization detection directions can be obtained. FIG. 3 (a) is a single frame image acquired by a camera; taking out the pixel gray values with the same unit polarization direction, and respectively copying the pixel gray values to the corresponding positions of four null images with the same resolution, so as to obtain four images, wherein each image has one quarter of data, and the other is null, as shown in fig. 3 (b); the null region data are complemented by a linear interpolation method, so that four complete images with different polarization directions can be obtained, and as shown in fig. 3 (c), the light intensity values of the complete images are respectively I (0), I (45), I (90) and I (135). Finally, the real-time detection of four Stokes parameters is realized. In addition, the polarization degree image of the target can be calculated according to a Stokes parameter formula.
The microlens array 13 is provided to include M rows and N columns of microlenses, each of which includes the light field position of the spot and direction information relative to the main lens group 12. Setting the upper left corner as the origin of an image coordinate system, wherein X is the row number of pixels in an image matrix, and Y is the column number; the vertical downward direction is the image matrix row forward direction, and the horizontal rightward direction is the column forward direction. Then the coordinates of the pixel within the imaged circular spot corresponding to any microlens Len (m, n) in the image coordinate system are (Xm, n, ym, n). As shown in fig. 2, at this time, the single pixel (Xm, n, ym, n) on the micro-polarized column detector 14 includes both the light field position and the direction information relative to the main lens group 12 of the point, and the corresponding linear polarization information, and the gray value collected by the pixel reflects the polarization intensity corresponding to the point.
And finally, scaling the micro-lens array type light field imaging system, and extracting corresponding detector pixels according to scaling data, so that linear polarization images and polarization degree images at different angles can be reconstructed. Meanwhile, four images with different polarization angles can be obtained in the detector area corresponding to each microlens, and at the moment, the original light field intensity images with different angles and positions can be calculated and restored by fusing polarized images with 0 degrees and 90 degrees (or 45 degrees and 135 degrees) according to the definition of a Stokes parameter formula, so that the unmixing of the light field and the polarization information is realized. The purpose of 'light field + polarization' real-time imaging detection of the target spilled oil from multiple directions by using a single main optical system is achieved.
As shown in fig. 4, the working flow of the light field polarization imaging detection system for sea surface oil spill of the invention is as follows: firstly, the light field polarization information of the target spilled oil is acquired by the light field polarization information acquisition subsystem 1, then is input into the image acquisition unit 21, and then is input into the calculation processing unit 22 by the image acquisition unit 21 to process the spilled oil light field polarization image information. The computing processing unit 22 extracts corresponding pixels according to the calibration data of the camera in the light field polarization information acquisition subsystem 1, and can realize the unmixing of the light field information and the polarization information through corresponding computation; then, the extracted light field information features and polarization information features are detected and identified, and finally, identification results of different oil types are obtained according to the comparison of gray values in the image information and displayed by the image display unit 23.

Claims (2)

1. The light field polarization imaging detection system for sea surface oil spill is characterized by comprising a light field polarization information acquisition subsystem (1) and an information processing subsystem (2);
the light field polarization information acquisition subsystem (1) comprises a light filter (11), a front optical imaging main lens group (12), a micro lens array (13) and a micro-polarizer array imaging detector (14), wherein the light filter (11), the front optical imaging main lens group (12), the micro lens array (13) and the micro-polarizer array imaging detector (14) are coaxially arranged, the micro lens array (13) is positioned at the focal plane position of the front optical imaging main lens group (12), and the micro-polarizer array imaging detector (14) is positioned at the focal plane position of the micro lens array (13);
natural light reflected by the object to be detected oil spill (10) enters a front optical imaging main lens group (12) through an optical filter (11), after being focused and imaged by the front optical imaging main lens group (12), light fields in different directions are secondarily imaged by all micro lenses in a micro lens array (13), the micro lens array (13) comprises M rows and N columns of micro lenses, the position of each micro lens comprises the light field position of the point and direction information relative to the main lens group (12), the position of each micro lens is finally recorded on a micro-polarizer array imaging detector (14), the real-time acquisition of the polarization information of the light field of the object oil spill is completed, at the moment, a single pixel on the micro-polarizer array imaging detector (14) comprises the light field position of the point and the direction information relative to the main lens group (12), the corresponding linear polarization information is also included, and the gray value acquired by the pixel reflects the polarization intensity corresponding to the point; then inputting the acquired information into an image acquisition unit (21), and inputting the acquired information into a calculation processing unit (22) by the image acquisition unit (21) to process the polarized image information of the oil spilling light field; the computing processing unit (22) extracts corresponding pixels according to calibration data of a camera in the light field polarization information acquisition subsystem (1), reconstructs linear polarization images and polarization degree images at different angles and positions, and restores original light field intensity images at different angles and positions through corresponding computation, so that the unmixing of light field information and polarization information can be realized; then, detecting and identifying the extracted light field information features and polarization information features, and finally, obtaining identification results of different oil types according to the comparison of gray values in the image information, and displaying the identification results by an image display unit (23);
the applicable wave band of the optical filter (11) is 650nm-1000nm.
2. The sea surface oil spill-oriented light field polarization imaging detection system according to claim 1, wherein the micro lens array (13) is formed by arranging a plurality of micro lenses with the same size and focal length, and each micro lens is in corresponding relation with a detector pixel in a fixed area range of a rear micro-polarizer array imaging detector (14).
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