Dispersion type hyperspectral camera color distortion measuring device and measuring method

Abstract

The invention provides a chromatic dispersion type hyperspectral camera color distortion measuring device and method. The device comprises a halogen lamp integrating sphere, a linear target, a collimator, a hyperspectral camera to be measured, a rotary table, a supporting and leveling platform, a rotary table control system and a data acquisition and analysis unit. The to-be-measured hyperspectral camera comprises a telescope objective, a hyperspectral camera slit, a hyperspectral camera light splitting assembly and a detector; according to the invention, the point-to-line alignment difficulty caused by simultaneous adjustment of pitching and orientation is reduced, and the alignment requirement of optical path measurement is simplified; through target selection, the measurement difficulty is reduced, and the measurement precision is improved; the method can be widely applied to color distortion measurement of a dispersion type high-precision spectral imaging system.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging and spectral detection, and particularly relates to a chromatic aberration measurement device and method for a dispersive hyperspectral camera. Background Technique

[0002] The chromatic aberration of a grating spectrometer is mainly caused by factors such as aberration caused by the off-axis of the optical system and defects of the grating itself. Its essence is the non-linear change of the magnification in the spatial dimension for different wavelengths, resulting in the physical scale of the target area corresponding to the pixels in the same spatial dimension shifting with the wavelength. This non-linearity may cause the spectrum received by a single pixel to contain information from adjacent spatial positions, leading to spectral aliasing between adjacent spatial dimensions, seriously affecting the fidelity of high-resolution imaging spectroscopy. By measuring chromatic aberration, the wavelength calibration error can be corrected, and the data credibility can be improved, which is crucial in application scenarios that require high-precision spectral measurement.

[0003] Patent CN112284537A describes a method for detecting spectral curvature and trapezoidal aberration for a push-broom hyperspectral imager. This method makes a spectral curvature and trapezoidal aberration detection target, collects dark background data and target imaging data, performs non-uniformity correction and radiometric calibration, averages the data in the time dimension direction, and finally calculates the spectral curvature and trapezoidal aberration through a homologous point search algorithm, with an accuracy up to the sub-pixel level. This patent mainly introduces the measurement process of spectral curvature and trapezoidal aberration, without introducing the specific design form of the target, and does not consider the difficulty brought by the two-dimensional adjustment of pitch and azimuth during optical path calibration. XUAN ZHANG et al. from North University of China proposed a spectrometer design method based on a prism-prism-grating (PPG) dispersion module in "Xuan Zhang, et al. "A design method for direct vision coaxial linear dispersion spectrometers." Optics Express 30.21(2022): 38266-38283." for correcting spectral non-linear aberration. This method analyzes the dispersion characteristics of prisms and gratings, selects appropriate optical materials, and uses a loop traversal algorithm to optimize the system structure parameters. The spectral linear index of the system is established through the dispersion equation of the PPG module, and the structure parameters of the PPG module are determined in combination with the design indicators to meet the requirements of linear dispersion. However, this method is highly dependent on optical materials, and if the material selection does not meet the requirements, it may affect the measurement accuracy; at the same time, it has high requirements for environmental conditions and light source uniformity. If the conditions are unstable, it may lead to errors and it is difficult to cope with instrument aging or environmental changes during long-term operation. These limitations may restrict its universality and reliability in practical applications.

[0004] In view of this, the present invention provides a device and method for measuring chromatic aberration of a dispersive hyperspectral camera. Summary of the Invention

[0005] The object of the present invention is to provide a device and method for measuring chromatic aberration of a dispersive hyperspectral camera, which reduces the difficulty of point-to-line alignment caused by simultaneous adjustment of pitch and azimuth, simplifies the alignment requirements for optical path measurement, reduces the measurement difficulty through the selection of the target, and improves the measurement accuracy. It can be widely applied to the measurement of chromatic aberration of a dispersive high-precision spectral imaging system.

[0006] To achieve the above object, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a device for measuring chromatic aberration of a dispersive hyperspectral camera, which includes a halogen lamp integrating sphere, a linear target, a collimator, a hyperspectral camera to be measured, a turntable, a support and leveling platform, and a turntable control system and a data acquisition and analysis unit; The hyperspectral camera to be measured includes a telescopic objective lens, a hyperspectral camera slit, a hyperspectral camera spectral splitting component and a detector; the hyperspectral camera slit is arranged orthogonally to the opening length direction of the linear target, and the overlapping area between the hyperspectral camera slit and the opening of the linear target is the size of one pixel; The axis of the turntable is perpendicular to the opening length direction of the linear target. The hyperspectral camera to be measured is connected to the turntable and placed on the support and leveling platform through the turntable, so as to ensure that the optical axis of the hyperspectral camera to be measured is always in the same plane as the optical axes of the halogen lamp integrating sphere, the linear target and the collimator during the rotation around the axis; the optical axes of the halogen lamp integrating sphere, the linear target, the collimator and the hyperspectral camera to be measured in the initial state are on the same straight line, and the linear target is placed at the focal plane of the collimator to ensure that the broadband light emitted by the halogen lamp integrating sphere passes through the linear target and the collimator in sequence to form a parallel beam, and then is incident on the hyperspectral camera to be measured and passes through the telescopic objective lens, the hyperspectral camera slit and the hyperspectral camera spectral splitting component in sequence, and finally forms a discrete point image separated by wavelength on the detector; The turntable control system and the data acquisition and analysis unit are used to control the overall mechanism after the hyperspectral camera to be measured is connected to the turntable, perform image acquisition while driving the hyperspectral camera to be measured to rotate relative to the axis within a preset angle range through the turntable, and calculate the difference in the centroid coordinates of different wavelengths based on the acquired images to obtain the chromatic aberration amount.

[0007] Preferably, the width of the opening of the linear target d' The calculation is specifically as follows: In the formula, f 1 is the focal length of the collimator; f 2 is the focal length of the hyperspectral camera to be measured;d is the slit width of the slit of the hyperspectral camera.

[0008] Preferably, the support leveling platform adopts a three-point support leveling platform.

[0009] Preferably, it further includes an air-bearing optical platform, and the halogen lamp integrating sphere, the one-dimensional target, and the collimator are all fixedly installed on the air-bearing optical platform; to isolate and eliminate external vibrations on the halogen lamp integrating sphere, the one-dimensional target, and the collimator through the air-bearing optical platform, and maintain the relative position stability among the three.

[0010] In a second aspect, the present invention proposes a method for measuring chromatic aberration of a dispersive hyperspectral camera, and the method is implemented by using any one of the above-mentioned devices for measuring chromatic aberration of a dispersive hyperspectral camera, and specifically includes the following steps: S1. Turn on the halogen lamp integrating sphere. After the broadband light emitted passes through the one-dimensional target to form a one-dimensional bright light, it forms a parallel beam through the collimator and is incident on the hyperspectral camera to be measured; S2. Control the turntable to rotate to drive the hyperspectral camera to be measured to rotate and scan to cover the full field of view range, and synchronously trigger the hyperspectral camera to collect n frames of spectral-spatial two-dimensional images in the same field of view at each position; after completion, block the entrance pupil of the hyperspectral camera to be measured, and continuously collect m frames of images; and perform preprocessing on all the original image data; S3. For the m frames of images collected by blocking the entrance pupil of the hyperspectral camera to be measured after preprocessing, take the average value as the average noise brightness value of the image plane; S4. For the n frames of images collected in the same field of view after preprocessing, after eliminating random noise through time-domain median filtering, combine the average noise brightness value of the image plane to extract the centroid coordinates of the spatial dimension of the image at each wavelength point, and calculate the chromatic aberration value to generate a chromatic aberration distribution curve for the entire wavelength band.

[0011] Preferably, the preprocessing is specifically to perform band-pass filtering and non-uniformity correction of pixel response on the original image data.

[0012] Preferably, the opening length direction of the one-dimensional target is parallel to the ground, and the slit of the hyperspectral camera is perpendicular to the ground; the horizontal axis of the collected image represents the spectral dimension, and the vertical axis represents the spatial dimension.

[0013] Preferably, the combining of the average noise brightness value of the image plane to extract the centroid coordinates of the spatial dimension of the image at each wavelength point is specifically calculated as follows: In the formula, y wavelenth is the centroid coordinate of the image formed by scanning the point image at a certain wavelength along the slit direction, y i is the iThe average spatial dimension coordinates collected n times for each field of view DN i is the i average spatial dimension pixel brightness value collected n times for the DN noise th field of view,

[0014] Preferably, the calculation of the chromatic aberration value is specifically as follows: In the formula, y smile is the wavelength λ 1 and the chromatic aberration between the wavelength λ 2, and are respectively the spatial dimension centroid coordinates of the wavelength λ 1 and the wavelength λ 2.

[0015] In a third aspect, the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, it implements any of the above chromatic aberration measurement methods for a dispersive hyperspectral camera.

[0016] Compared with the prior art, the present invention has the following beneficial effects: First of all, the present invention realizes accurate measurement through a high-precision one-dimensional target and uniform illumination, avoids relying on complex reference targets, and reduces the requirements for target design and production; secondly, the present invention simplifies the data processing process through turntable scanning and centroid calculation; at the same time, the device design is flexible and can be dynamically adjusted to adapt to environmental changes and instrument aging problems, improving the stability and reliability of measurement. The present invention can be used for chromatic aberration measurement of hyperspectral cameras and is particularly valuable in scenarios where high-precision spectral imaging is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the structure diagram of the device of the present invention; Figure 2 is the structure diagram of the hyperspectral camera to be measured of the present invention; Figure 3 is the flowchart of the method of the present invention; Figure 4 is the schematic diagram of the image coordinate axis of the present invention.

[0018] In the figure: 1 - halogen lamp integrating sphere; 2 - one-dimensional target; 3 - collimator; 4 - hyperspectral camera to be measured; 5 - turntable; 6 - support and leveling platform; 7 - turntable control system and data acquisition and analysis unit; 8 - telescopic objective; 9 - hyperspectral camera slit; 10 - hyperspectral camera spectroscopic component; 11 - detector. Detailed Implementation Manner

[0019] The following will specifically describe the technical solution of the present invention in conjunction with the attached Figures 1-4 drawings.

[0020] The present invention provides a chromatic aberration measurement device for a dispersive hyperspectral camera, which is applicable to the chromatic aberration measurement of hyperspectral cameras using planar, concave, and convex grating imaging; as Figure 1 shown, the device includes a halogen lamp integrating sphere 1, a linear target 2, a collimator 3, a to-be-tested hyperspectral camera 4, a turntable 5, a support leveling platform 6, and a turntable control system and data acquisition and analysis unit 7; As Figure 2 shown, the to-be-tested hyperspectral camera 4 includes a telescopic objective 8, a hyperspectral camera slit 9, a hyperspectral camera spectroscopic assembly 10, and a detector 11; the hyperspectral camera slit 9 is orthogonally arranged with respect to the opening length direction of the linear target 2, and the overlapping area between the hyperspectral camera slit 9 and the opening of the linear target 2 is the size of one pixel; The rotation axis of the turntable 5 is perpendicular to the opening length direction of the linear target 2, and the to-be-tested hyperspectral camera 4 is connected to the turntable 5 and placed on the support leveling platform 6 through the turntable 5, so as to ensure that the optical axis of the to-be-tested hyperspectral camera 4 is always in the same plane as the optical axes of the halogen lamp integrating sphere 1, the linear target 2, and the collimator 3 during the rotation around the rotation axis; the optical axes of the halogen lamp integrating sphere 1, the linear target 2, the collimator 3, and the to-be-tested hyperspectral camera 4 in the initial state are all on the same straight line, and the linear target 2 is placed at the focal plane of the collimator 3 to ensure that the broadband light emitted by the halogen lamp integrating sphere 1 passes through the linear target 2 and the collimator 3 in sequence to form a parallel beam, and then is incident on the to-be-tested hyperspectral camera 4 and passes through the telescopic objective 8, the hyperspectral camera slit 9, and the hyperspectral camera spectroscopic assembly 10 in sequence, and finally discrete point images are formed by wavelength separation on the detector 11; The turntable control system and data acquisition and analysis unit 7 is used to control the overall mechanism after the to-be-tested hyperspectral camera 4 is connected to the turntable 5, perform image acquisition while driving the to-be-tested hyperspectral camera 4 to rotate relative to the rotation axis within a preset angle range through the turntable 5, and calculate the difference in the centroid coordinates of different wavelengths based on the acquired images to obtain the chromatic aberration amount.

[0021] In this embodiment, the width of the opening of the linear target 2 d' is specifically calculated as follows: In the formula, f 1 is the focal length of the collimator 3; f 2 is the focal length of the to-be-tested hyperspectral camera 4; d is the slit width of the hyperspectral camera slit 9.

[0022] In this embodiment, the support leveling platform 6 adopts a three-point support leveling platform.

[0023] In this embodiment, it further includes an air-bearing optical platform. The halogen lamp integrating sphere 1, the one-dimensional target 2, and the collimator 3 are all fixedly installed on the air-bearing optical platform. The air-bearing optical platform eliminates external vibrations through air film suspension isolation, maintaining the relative position stability among the halogen lamp integrating sphere 1, the one-dimensional target 2, and the collimator 3.

[0024] The present invention proposes a method for measuring chromatic aberration of a dispersive hyperspectral camera. The method is implemented by using any one of the above-mentioned devices for measuring chromatic aberration of a dispersive hyperspectral camera, such as Figure 3 , and specifically includes the following steps: S1. Turn on the halogen lamp integrating sphere 1. After the broadband light emitted passes through the one-dimensional target 2 to form a one-dimensional bright light, it forms a parallel beam through the collimator 3 and is incident on the hyperspectral camera 4 to be measured. S2. Control the turntable 5 to rotate to drive the hyperspectral camera 4 to be measured to rotate and scan to cover the full field of view range (at this time, on the hyperspectral camera detector, a series of point images of different wavelengths can be observed moving along the spatial dimension. When the point image scans to the edge of the slit, it is the edge of the field of view). Synchronously trigger the hyperspectral camera to collect n frames of spectral-spatial two-dimensional images of the same field of view at each position. After completion, block the entrance pupil of the hyperspectral camera 4 to be measured and continuously collect m frames of images. And preprocess all the original image data. In this embodiment, n = 10 and m = 50. S3. For the m frames of images collected with the entrance pupil of the hyperspectral camera 4 to be measured blocked after preprocessing, take the average value as the average noise luminance value of the image plane. S4. For the n frames of images collected in the same field of view after preprocessing, after eliminating random noise through time-domain median filtering, combine the average noise luminance value of the image plane to extract the centroid coordinates of the spatial dimension of each wavelength point image, and calculate the chromatic aberration value to generate a chromatic aberration distribution curve for the entire wavelength band.

[0025] In this embodiment, the preprocessing is specifically to perform band-pass filtering and non-uniformity correction of pixel response on the original image data.

[0026] In this embodiment, the opening length direction of the one-dimensional target 2 is parallel to the ground, and the slit 9 of the hyperspectral camera is perpendicular to the ground. The one-dimensional target 2 can be calibrated to have its opening length direction parallel to the ground by using a high-precision theodolite. And the turntable tabletop can be calibrated by using a high-precision theodolite so that the slit 9 of the hyperspectral camera is perpendicular to the ground. Such as Figure 4 , the horizontal axis of the collected image represents the spectral dimension, and the vertical axis represents the spatial dimension. The points in each row represent the point images of different wavelengths in the same field of view, and the points in each column represent the point images of different fields of view at the same wavelength. Wavelengths beyond the spectral range of the hyperspectral camera are not considered.

[0027] In this embodiment, the spatial dimension centroid coordinates of the images at each wavelength point are extracted by combining the average noise luminance value of the image plane, and the specific calculation is as follows: In the formula, y wavelenth is the centroid coordinate of the image formed after scanning the point image at a certain wavelength along the slit direction, y i is the average spatial dimension coordinate collected n times in the i th field of view, DN i is the average spatial dimension pixel luminance value collected n times in the i th field of view, DN noise is the average noise luminance value of the image plane.

[0028] In this embodiment, the calculation of the color distortion value is specifically as follows: In the formula, y smile is the color distortion between wavelength λ 1 and wavelength λ 2, and are the spatial dimension centroid coordinates of wavelength λ 1 and wavelength λ 2 respectively.

[0029] The present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, it implements any of the above color distortion measurement methods for a dispersive hyperspectral camera.

[0030] In summary, aiming at the problems of the prior art such as relying on complex targets, cumbersome data processing, and weak anti-environmental interference ability, the present invention realizes efficient and accurate color distortion measurement through a high-precision one-dimensional target, a uniform illumination system, turntable scanning, and centroid calculation methods. The device includes a halogen lamp integrating sphere, a one-dimensional target, a collimator, a to-be-tested hyperspectral camera, a turntable, and a data acquisition and analysis unit. An infinite-distance composite color light image of the one-dimensional target is generated through the collimator. The slit of the dispersive hyperspectral camera is orthogonal to the one-dimensional target, and a single-point dispersion image is generated at the intersection point. By combining the full-field scanning of the turntable and the calculation of the centroid coordinate difference, the full-band color distortion distribution curve under each spatial field of view is obtained. The advantage of the present invention is to reduce the point-to-line alignment difficulty caused by the simultaneous adjustment of pitch and azimuth, and simplify the alignment requirements for optical path measurement. By selecting the target, the measurement difficulty is reduced and the measurement accuracy is improved. It can be widely applied to the color distortion measurement of dispersive high-precision spectral imaging systems.

[0031] The above are the preferred embodiments of the present invention. Any changes made to the technical solution of the present invention that do not exceed the scope of the technical solution of the present invention in terms of the functions and effects produced shall fall within the protection scope of the present invention.

Claims

1. A chromatic aberration measurement device for a dispersive hyperspectral camera, characterized in that The device includes a halogen lamp integrating sphere (1), a linear target (2), a collimator (3), a hyperspectral camera to be measured (4), a turntable (5), a support leveling platform (6), and a turntable control system and data acquisition and analysis unit (7); The hyperspectral camera to be measured (4) includes a telescopic objective lens (8), a hyperspectral camera slit (9), a hyperspectral camera spectral splitting component (10), and a detector (11); the hyperspectral camera slit (9) is orthogonally arranged in the opening length direction of the linear target (2), and the overlapping area between the hyperspectral camera slit (9) and the opening of the linear target (2) is the size of one pixel; The rotation axis of the turntable (5) is perpendicular to the opening length direction of the linear target (2), and the hyperspectral camera to be measured (4) is connected to the turntable (5) and placed on the support leveling platform (6) through the turntable (5) to ensure that the optical axis of the hyperspectral camera to be measured (4) is always in the same plane as the optical axes of the halogen lamp integrating sphere (1), the linear target (2), and the collimator (3) during the rotation around the rotation axis; the optical axes of the halogen lamp integrating sphere (1), the linear target (2), the collimator (3), and the hyperspectral camera to be measured (4) in the initial state are all on the same straight line, and the linear target (2) is placed at the focal plane of the collimator (3) to ensure that the broadband light emitted by the halogen lamp integrating sphere (1) passes through the linear target (2) and the collimator (3) in sequence to form a parallel beam, then enters the hyperspectral camera to be measured (4) and passes through the telescopic objective lens (8), the hyperspectral camera slit (9), and the hyperspectral camera spectral splitting component (10) in sequence, and finally forms a discrete point image separated by wavelength on the detector (11); The turntable control system and data acquisition and analysis unit (7) is used to control the overall mechanism after the hyperspectral camera to be measured (4) is connected to the turntable (5), drive the hyperspectral camera to be measured (4) to rotate relative to the rotation axis within a preset angle range while performing image acquisition, and calculate the difference in centroid coordinates of different wavelengths based on the acquired images to obtain the chromatic aberration variable.

2. The chromatic aberration measurement device for a dispersive hyperspectral camera according to claim 1, characterized in that, The width of the opening of the linear target (2) d' is calculated specifically as follows: In the formula, f 1 is the focal length of the collimator (3); f 2 is the focal length of the hyperspectral camera (4) to be measured; d is the slit width of the hyperspectral camera slit (9).

3. The chromatic aberration measurement device for a dispersive hyperspectral camera according to claim 1, characterized in that, The support leveling platform (6) adopts a three-point support leveling platform.

4. A chromatic aberration measurement device for a dispersive hyperspectral camera according to claim 1, characterized in that, It further includes an air-bearing optical platform, and the halogen lamp integrating sphere (1), the linear target (2), and the collimator (3) are all fixedly installed on the air-bearing optical platform; the air-bearing optical platform eliminates external vibrations through air film suspension isolation to maintain the relative position stability among the halogen lamp integrating sphere (1), the linear target (2), and the collimator (3).

5. A method for measuring color distortion of a dispersive hyperspectral camera, characterized in that, The method is implemented by using the chromatic aberration measurement device for a dispersive hyperspectral camera according to any one of claims 1-4, and specifically includes the following steps: S1. Turn on the halogen lamp integrating sphere (1), and after the emitted broadband light forms a linear bright light through the linear target (2), form a parallel beam through the collimator (3) and enter the hyperspectral camera to be measured (4); S2. Control the turntable (5) to rotate, driving the hyperspectral camera to be measured (4) to rotate and scan to cover the full field of view range. Synchronously trigger the hyperspectral camera to collect n frames of spectral-spatial two-dimensional images of the same field of view at each position. After completion, block the entrance pupil of the hyperspectral camera to be measured and continuously collect m frames of images. And preprocess all the original image data. S3. For the m frames of images collected by blocking the entrance pupil of the hyperspectral camera to be measured after preprocessing, take the average value as the average noise brightness value of the image plane. S4. For the n frames of images collected in the same field of view after preprocessing, after eliminating random noise by time-domain median filtering, combine the average noise brightness value of the image plane to extract the centroid coordinates of the spatial dimension of the image at each wavelength point, and calculate the chromatic aberration value to generate a chromatic aberration distribution curve of the full band.

6. A method for measuring color distortion of a dispersive hyperspectral camera according to claim 5, characterized in that, The preprocessing is specifically to perform band-pass filtering and non-uniformity correction of pixel response on the original image data.

7. A method for measuring chromatic aberration of a dispersive hyperspectral camera according to claim 5, characterized in that, The opening length direction of the one-dimensional target (2) is parallel to the ground, and the slit (9) of the hyperspectral camera is perpendicular to the ground. The horizontal axis of the collected image represents the spectral dimension, and the vertical axis represents the spatial dimension.

8. A method for measuring chromatic aberration of a dispersive hyperspectral camera according to claim 7, characterized in that, The extraction of the centroid coordinates of the spatial dimension of the image at each wavelength point by combining the average noise brightness value of the image plane is specifically calculated as follows: In the formula, y wavelenth is the centroid coordinate of the image formed after scanning the point image at a certain wavelength along the slit direction, y i is the average spatial dimension coordinate collected n times for the i th field of view, DN i is the average spatial dimension pixel brightness value collected n times for the i th field of view, DN noise is the average noise brightness value of the image plane.

9. A method for measuring chromatic aberration of a dispersive hyperspectral camera according to claim 8, characterized in that, The calculation of the chromatic aberration value is specifically as follows: Wherein, y smile is the wavelength λ The chromatic aberration between 1 and the wavelength λ 2, and are respectively the spatial dimensional centroid coordinates of the wavelength λ 1 and the wavelength λ 2.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the chromatic aberration measurement method of the dispersive hyperspectral camera as described in any one of claims 5-9.

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