CN115118956A - Method and system for measuring polarization performance of linear polarization image sensor - Google Patents
Method and system for measuring polarization performance of linear polarization image sensor Download PDFInfo
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Abstract
The invention provides a method and a system for measuring the polarization performance of a linear polarization image sensor, comprising the following steps: respectively controlling a turntable to rotate a high-performance linear polarizer under a bright field condition and a dark field condition and under each set exposure, and shooting a plurality of pictures by using a linear polarization image sensor without an optical lens; selecting a central area of a picture, obtaining gray response values of different polarization directions under a set exposure, and calculating by a fitting function or a physical formula with a curve function to obtain an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency of each polarization direction; and evaluating the polarization performance of the linear polarization image sensor by measuring the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction. The invention overcomes the defect that the polarization performance of the existing linear polarization image sensor is difficult to accurately measure, and realizes the accurate evaluation of the polarization performance of the linear polarization image sensor.
Description
Technical Field
The invention relates to the technical field of polarization imaging, in particular to a device and a method for measuring polarization performance of a linear polarization image sensor.
Background
At present, the test of the linear polarization image sensor does not form a uniform standard, and the test standards for the image sensor at home and abroad are the camera and image sensor test standards made by the European machine vision Association: EMVA Standard 1288, which is applicable to monochrome or color digital video cameras with linear characteristics as well as analog cameras and image sensors with image acquisition cards. At present, most of commercial integrated partial-focus plane polarization image sensors are linear polarization sensors. The EMVA 1288 standard is wider in application range, and is improved by adopting the EMVA 1288 standard so as to adapt to the response characteristic of the pixel of the integrated polarization sensor.
The existing polarization sensor performance evaluation and analysis noise model, which is usually a gaussian noise and poisson noise combined model, has a large error with an actual measurement value, mainly because the performance parameter test of the linear polarization sensor is still incomplete, and quantum efficiency, extinction ratio, angle error and uniformity are not taken into consideration. Therefore, to obtain a complete error model closer to the true value, various performance parameters of the linear polarization image sensor need to be measured and substituted.
Disclosure of Invention
The invention provides a device and a method for testing the polarization performance of a linear polarization image sensor, which are used for solving the problem that the linear polarization image sensor is difficult to accurately measure the polarization performance parameters so as to realize accurate evaluation of the polarization performance of the linear polarization image sensor.
The invention provides a method for measuring the polarization performance of a linear polarization image sensor, which comprises the following steps:
respectively rotating the linear polarizer under a bright field condition and a dark field condition and under each set exposure, and shooting a plurality of pictures through the linear polarization image sensor;
selecting a central area of a picture to obtain gray response values of pixels in different polarization directions, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction through a fitting function or a physical formula of a curve function;
and evaluating the polarization performance of the linear polarization image sensor by measuring the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
According to the polarization performance measuring method of the linear polarization image sensor provided by the invention, the central area of the picture is selected to obtain the gray response values of the pixels in different polarization directions, and the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency in each polarization direction are obtained through a fitting function or a physical formula with a curve function, and the method specifically comprises the following steps:
in a bright field environment and a dark field environment, under a certain relative rotation angle of a turntable, a plurality of pictures are shot by using optical-lens-free equipment loaded with a linear polarization image sensor, and the gray value difference value in the same polarization direction is observed so as to adjust the fixed angle of the linear polarization sensor;
in a bright field environment, setting different equal-interval exposure time of a linear polarization image sensor, rotating a linear polarizer, shooting M pictures with N periods, and selecting a picture center area containing pixels with different polarization directions;
under the condition of equal interval exposure time and wavelength, rotating the turntable to obtain a sequence of gray response mean values of pixels in each polarization direction changing along with the relative rotation angle, and performing Fourier fitting to obtain a fitting function, wherein the mean value of the peak value of a fitting curve is mu y ；
Setting the rotary table under a certain specific wavelength and exposure, rotating the rotary table to obtain a first group of sequences of gray response mean values of pixels in all polarization directions along with the change of relative rotation angles, performing Fourier fitting to obtain fitting functions, and calculating phase differences among the functions in different polarization directions to obtain angle calibration values;
setting the same wavelength and exposure, rotating the rotary table to obtain a sequence of the gray response value of each polarization direction pixel along with the change of the relative rotation angle, selecting the sequence of the gray response value of each polarization direction pixel along with the change of the rotation angle in the central area for fitting, and calculating the average value of the peak value and the valley value of the function, wherein the ratio of the peak value to the valley value is the extinction ratio of each polarization direction pixel;
under the dark field environment, the exposure time and the bright field condition are controlled to be changed at equal intervals to obtain different exposure times t exp The dark signal output value of (2) and finally the average value sequence mu is obtained y.dark Calculating the gray value variance of the bright field and dark field environment, and fitting the gray value variance
Response with gray scaleMean value (. mu.) y -μ y.dark ) A first linear curve that varies, the first linear curve having a slope of the overall system gain K;
under the same bright field condition, setting the exposure time and wavelength with the same interval, placing the calibrated photodiode at the same position as the linear polarization image sensor, rotating the linear polarizer, and calculating the average value E of irradiance in unit area;
the exposure (mu) of the linear polarization image sensor is fitted y -μ y.dark ) With exposure time t exp Obtaining the slope of the second linear curve by the changed second linear curve function, substituting the slope into a slope physical formula, and obtaining the quantum efficiency eta;
and converting the optical filters with different wavelengths to obtain different quantum efficiencies, and drawing a change relation curve of the wavelength lambda and eta (lambda).
According to the polarization performance measuring method of the linear polarization image sensor provided by the invention, the step of acquiring the correction parameter matrix from the picture specifically comprises the following steps:
under the bright field condition, setting multiple exposure time and wavelength with equal intervals, rotating the linear polarizer, rotating the angle every time, shooting a plurality of pictures by the linear polarization image sensor, and selecting a picture center area;
under a certain specific exposure time and a certain specific wavelength, carrying out least square fitting on gray response measured values and ideal values of all pixels in each polarization direction to obtain uniformity correction parameter matrixes and dark noise matrixes of all superpixels;
wherein, the gray scale response value obtained by the calibrated photodiode is regarded as an ideal light intensity value.
According to the polarization performance measuring method of the linear polarization image sensor provided by the invention, the turntable is rotated under a certain specific wavelength and exposure, so as to obtain a first group of sequences of the gray response mean value of each polarization direction pixel along with the change of the relative rotation angle, and the method specifically comprises the following steps:
controlling the exposure amount by changing the illumination intensity of the integrating sphere light source or adjusting the exposure time of the linear polarization image sensor;
rotating the high-performance linear polarizer, and obtaining a sequence of gray scale response values of all polarization directions changing along with a relative rotation angle under a certain specific exposure;
and aiming at each polarization direction, acquiring a first group of sequences of the gray response mean value of each polarization direction pixel along with the change of the relative rotation angle.
According to the polarization performance measuring method of the linear polarization image sensor provided by the invention, the method for solving the angle calibration value and the extinction ratio comprises the following steps:
fourier fitting is carried out on the first group of sequences to obtain a fitting function of the gray response value of each polarization direction pixel along with the change of the relative rotation angle, and the peak value and the valley value of the fitting function are calculated;
selecting a sequence of gray response values of pixels in all polarization directions changing along with the rotation angle to perform Fourier fitting, calculating phase differences among fitting functions in different polarization directions, and generating an angle calibration value;
and calculating the average value of the peak value and the valley value of the fitting function, wherein the ratio of the peak value to the valley value is the extinction ratio of the polarization array.
According to the performance measurement method of the linear polarization image sensor provided by the invention, a second linear curve of the exposure of the polarization image sensor changing along with the exposure time is fitted, and the quantum efficiency is obtained according to the slope of the second linear curve, and the method specifically comprises the following steps:
exposure (mu) according to linear polarization image sensor y -μ y.dark ) With exposure time t exp The variation fit generates a second linear curve equation,
slope to the second linear curve equation
And substituting the total system gain K, the wavelength lambda, the illumination intensity mean value E, the Planck constant h, the unit area A and the light speed c into the process to obtain the quantum efficiency eta.
The present invention also provides a system for measuring polarization performance of a linear polarization image sensor, the system comprising:
the image acquisition module is used for rotating the linear polarizer under each set exposure under the bright field condition and the dark field condition respectively and shooting a plurality of images through the linear polarization image sensor;
the parameter calculation module is used for selecting a central area of the picture to obtain gray response values of pixels in different polarization directions, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction through a fitting function or a physical formula brought into a curve function;
and the polarization performance evaluation module is used for evaluating the polarization performance of the linear polarization image sensor through the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
According to the method and the system for measuring the polarization performance of the linear polarization image sensor, provided by the invention, the turntable is rotated in a bright field environment and a dark field environment, the linear polarization image sensor is used for shooting a plurality of pictures, a fitting function is obtained through fitting, a phase difference and a peak-valley value are calculated or are brought into a physical relation, an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency of each polarization direction are obtained, and the polarization performance of the linear polarization image sensor is measured. Accurate measurement of relevant data is achieved, and the performance of the linear polarization image sensor can be evaluated.
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In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for measuring polarization performance of a linear polarization image sensor according to the present invention;
FIG. 2 is a second schematic flowchart of a method for measuring polarization performance of a linear polarization image sensor according to the present invention;
FIG. 3 is a third schematic flowchart of a method for measuring polarization performance of a linear polarization image sensor according to the present invention;
FIG. 4 is a fourth schematic flowchart of a method for measuring polarization performance of a linear polarization image sensor according to the present invention;
FIG. 5 is a fifth flowchart illustrating a method for measuring polarization performance of a linear polarization image sensor according to the present invention;
FIG. 6 is a schematic diagram of light propagation of a polarization performance measuring apparatus of a linear polarization image sensor according to the present invention;
FIG. 7 is a schematic diagram of module connection of a polarization performance measurement system of a linear polarization image sensor provided in the present invention;
reference numerals:
110: a picture acquisition module; 120: a parameter calculation module; 130: and a polarization performance evaluation module.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The following describes a polarization performance measurement method of a linear polarization image sensor according to the present invention with reference to fig. 1 to 5, including:
s100, setting exposure time and wavelength at equal intervals under a bright field condition and a dark field condition respectively, rotating a linear polarizer, and shooting a plurality of pictures through a linear polarization image sensor;
s200, selecting a central area of a picture, obtaining a sequence of gray scale response values of all polarization directions changing along with a relative rotation angle, and calculating a phase difference and a peak-valley value through a fitted function or substituting the phase difference and the peak-valley value into a physical relation to obtain an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency of all polarization directions;
s300, evaluating the polarization performance of the linear polarization image sensor through the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
Referring to fig. 6, in order to acquire an image captured by the linear polarization image sensor, the present invention provides an integrating sphere light source, a filter wheel, a collimator, a linear polarizer with high extinction ratio and transmittance, a turntable, a calibrated photodiode, an optical lens-less device having the linear polarization image sensor mounted thereon, and a displacement stage. The path of the light ray is that parallel and uniform light emitted by the integrating sphere light source sequentially passes through the filter wheel, the collimator and the rotatable high-performance linear polarizer fixed on the turntable, and finally reaches the photosensitive surface of the linear polarization image sensor fixed by the displacement platform or the support or the calibrated photodiode. A plurality of images are taken by a linear polarization image sensor.
And the wavelength of the parallel uniform light incident to the light sensing surface of the linear polarization image sensor can be changed by adjusting the parameters of the parallel uniform light source emitted by the integrating sphere light source and adjusting the filter wheel.
Obtaining polarization gray scale response values in different directions from a picture, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction through a fitting function or an equation of a relationship, wherein the method specifically comprises the following steps:
s201, in a bright field environment and a dark field environment, under a certain relative rotation angle of a rotary table, shooting a plurality of pictures by using optical-lens-free equipment loaded with a linear polarization image sensor, and observing a gray value difference value in the same polarization direction to adjust a fixed angle of the linear polarization sensor;
s202, in a bright field environment, setting different equal-interval exposure time of a linear polarization image sensor, rotating a linear polarizer, shooting M pictures with N periods, and selecting a picture center region to contain pixels with different polarization directions;
in the invention, the exposure time is set to be 1s, 2s, 1.. and 10s respectively, and under the condition of 10 times of exposure time, the pixel response value rotating along with the turntable is measured under the bright field and dark field conditions respectively, wherein the turntable drives the rotatable high-performance linear polarizer to rotate clockwise by the increment with the step length of 1 degree for 360 times;
s203, under the bright field environment and under the condition of equal-interval exposure time and wavelength, rotating the turntable to obtain a sequence of gray response mean values of pixels in all polarization directions changing along with the relative rotation angle, and performing Fourier fitting to obtain a fitting function, wherein the mean value of the peak value of a fitting curve is mu y ；
S204, setting a certain specific wavelength and exposure under a bright field environment, rotating a turntable to obtain a first group of sequences of gray response mean values of pixels in all polarization directions along with the change of relative rotation angles, performing Fourier fitting to obtain fitting functions, and calculating phase differences among the functions in different polarization directions to obtain angle calibration values;
s205, setting the same wavelength and exposure time, rotating the turntable to obtain a sequence of gray response values of all pixels in each polarization direction along with the change of a relative rotation angle, selecting the sequence of the gray response values of all polarization directions in a central area along with the change of the rotation angle for fitting, and calculating the average value of the peak value and the valley value of a function, wherein the ratio of the peak value to the valley value is the extinction ratio of the pixels in each polarization direction;
s206, under the dark field environment, controlling the exposure time and the bright field condition to be changed at equal intervals to obtain different exposure times t exp The dark signal output value of (2) and finally the average value sequence mu is obtained y.dark Calculating the gray value variance of the bright field and dark field environment, and fitting the gray value variance
Mean value (μ) with gray scale response y -μ y.dark ) A first linear curve that varies, the first linear curve having a slope of the overall system gain K;
s207, setting exposure time and wavelength with the same interval under the same bright field condition, placing the calibrated photodiode at the same position as the linear polarization image sensor, rotating the linear polarizer, and calculating the average value E of irradiance in unit area;
s208, fitting a linear polarization imageExposure dose (mu) of sensor y -μ y.dark ) With exposure time t exp Obtaining the slope of the second linear curve by the changed second linear curve function, substituting the slope into a slope physical formula, and obtaining the quantum efficiency eta;
s209, converting the optical filters with different wavelengths to obtain different quantum efficiencies, and drawing a variation relation curve of the wavelength lambda and eta (lambda).
Acquiring a uniformity correction parameter matrix, specifically comprising:
s301, under the bright field condition, under a certain specific exposure time and a certain specific wavelength, rotating the linear polarizer, rotating the angle each time, shooting a plurality of pictures by the linear polarization image sensor, and selecting a picture central area;
s302, performing least square fitting on the gray response measured values of all pixels in each polarization direction and ideal values to obtain uniformity correction parameter matrixes and dark noise matrixes of all super pixels;
wherein the ideal light intensity value is obtained by correcting the gray scale response value of the photodiode.
The polarization performance of the linear polarization image sensor can be evaluated by solving the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency in each polarization direction.
Under the bright field environment, under a certain specific wavelength and exposure, rotating the turntable to obtain a first group of sequences of gray response mean values of pixels in all polarization directions along with the change of relative rotation angles, which specifically comprises:
s2021, controlling exposure by changing the illumination intensity of an integrating sphere light source or adjusting the exposure time of a linear polarization image sensor;
s2022, rotating the high-performance linear polarizer, and obtaining a sequence of gray scale response mean values of all polarization directions changing along with a relative rotation angle under a certain specific exposure;
s2023, aiming at each polarization direction, obtaining a first group of sequences of the gray scale response mean value of each polarization direction pixel along with the change of the relative rotation angle.
Under bright field environment, by changing light intensity of integrating sphere light source or setting cameraThe exposure time of the computer is controlled, the rotary table is rotated to shoot M pictures with N periods under a certain exposure, 4 polarization directions exist in the selected area of the pictures, I is the pixel number of a certain polarization direction, the nth (N is more than or equal to 1 and less than or equal to N) picture of the polarization direction is recorded, and the response value of the ith (I is more than or equal to 1 and less than or equal to I) pixel
The average μ of the polarization direction pixel response at the relative rotation angle is:
all the pixel gray response values are
In the invention, a region containing 30000 pixels in each polarization direction in a picture is selected, and the average value of the response of each pixel in each polarization direction when the rotatable high-performance linear polarizer rotates to the position is calculated. Let the response value of the ith (i is more than or equal to 1 and less than or equal to 30000) pixel in a certain polarization direction be x i Then the corresponding average value μ of the pixel for that polarized pixel when the rotatable high performance linear polarizer is rotated to that angle is:
the method is adopted for each rotating angle of the rotatable high-performance linear polarizer, and finally, a sequence of pixel response average values of 360 points in each polarization direction under different exposure times is obtained.
Under the conditions of setting different exposure quantities and wavelengths at equal intervals, the sequence of the gray response mean value of the pixels in each polarization direction changing along with the relative rotation angle is obtained by adopting the method; under the bright field environment and under a certain exposure and wavelength, the gray scale response mean value of each polarization direction pixel changes along with the first group of sequences of relative rotation angles.
Fourier fitting is carried out on the first group of sequences to obtain a fitting function, pixels in the central area of the image are selected to obtain a fitting function of the gray response value of the pixels along with the relative rotation angle, the phase difference between the fitting functions in the polarization directions, namely the angle calibration value, and the ratio of the peak value to the mean value of the valley value of the fitting curve, namely the extinction ratio, are obtained.
Under a dark field environment, controlling the exposure time and the bright field condition to change at equal intervals, measuring the gray value of the linear polarization image sensor for N times, and calculating a gray value response mean value sequence; calculating the variance of gray values under bright field condition and dark field condition, for example, when the acquisition time N is 2, synthesizing a pixel map with the same polarization direction and the variance of gray values is
Fitting gray value variance under different rotation angles
Mean value of the gray value (mu) y -μ y.dark ) A second linear curve of change with a slope of the overall system gain K.
Fixing the calibrated photodiode at the same position of the experimental linear polarization image sensor, setting the emergent light intensity of the integrating sphere to be the same as that of a dark field environment, setting the exposure time to be changed at equal intervals with that of the dark field environment, rotating the rotary table under the same bright field environment, measuring N periods, and calculating to obtain the mean value E of the illumination intensity of the unit area A.
The exposure (mu) of the linear polarization image sensor is fitted y -μ y.dark ) With exposure time t exp The second linear curve that changes, the slope according to second linear curve seeks quantum efficiency, specifically includes:
s2061, fitting the exposure (mu) of the linear polarization image sensor y -μ y.dark ) With exposure time t exp A second linear curve equation of varying slope
Wherein the total system gain K is substituted,The quantum efficiency eta can be obtained by the wavelength lambda, the illumination intensity mean value E, the Planck constant h, the unit area A and the light speed c. Different quantum efficiencies can be obtained by converting the optical filters with different wavelengths, so that a change relation curve of the wavelength lambda and the eta (lambda) can be drawn.
Difference of pixel gray scale response average value and exposure time average value t through bright and dark fields in each polarization direction exp The linear curve function of the linear polarization image sensor obtains the slope of the linear polarization image sensor, carries the slope into each obtained and known constant to obtain eta, measures the function curve of the eta along with the wavelength under different wavelength conditions, solves the problem of measuring the quantum efficiency of each polarization direction in the linear polarization image sensor, and can also obtain an extinction ratio, an angle calibration value and a correction parameter matrix, thereby being convenient for evaluating the performance of the linear polarization image sensor.
Referring to fig. 7, the present invention also discloses a polarization performance measurement system of a linear polarization image sensor, the system comprising:
the image acquisition module 110 is used for rotating the linear polarizer under a bright field condition and a dark field condition respectively, and taking a plurality of images by using the linear polarization image sensor once each time the linear polarizer rotates;
the parameter calculation module 120 is configured to select a central area pixel of the image to obtain a sequence of gray response values in different polarization directions changing with the relative rotation angle, and calculate a phase difference and a peak-valley value through a fitting function or bring the phase difference and the peak-valley value into a physical relation to obtain an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction;
and the polarization performance evaluation module 130 is configured to evaluate the polarization performance of the linear polarization image sensor according to the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
The image acquisition module 110 is used for setting exposure time and wavelength at equal intervals under a bright field condition, rotating the linear polarizer once, and shooting a plurality of images by the linear polarization image sensor;
the exposure amount is changed by changing the illumination intensity of the light source or adjusting the exposure time;
and rotating the linear polarizer to obtain a first group of sequences of gray scale response mean values of pixels in each polarization direction along with the change of the relative rotation angle under a certain exposure and wavelength.
The parameter calculation module 120 fits the first group of sequences by a fourier fitting method to obtain a fitting function of the gray response mean value of each polarization direction pixel along with the change of the relative rotation angle, and calculates the phase difference between the fitting functions of different polarization directions, namely the angle calibration value;
and calculating the mean value of the peak value and the valley value of the fitting function of each polarization direction, wherein the ratio of the peak value to the valley value is the extinction ratio of the polarization array.
Exposure (mu) according to linear polarization image sensor y -μ y.dark ) With exposure time t exp The variation fit generates a second linear curve equation,
and substituting the total system gain, the wavelength, the illumination intensity mean value, the unit area, the Planck constant and the light speed into the slope of the second linear curve equation to obtain the quantum efficiency.
The exposure (mu) of the linear polarization image sensor is fitted y -μ y.dark ) With exposure time t exp A second linear curve equation of varying slope
The quantum efficiency eta can be obtained by substituting the total system gain K, the wavelength lambda, the illumination intensity mean value E, the Planck constant h, the unit area A and the light speed c. Different quantum efficiencies can be obtained by converting the optical filters with different wavelengths, so that a curve of the variation relation between the wavelength lambda and the mu (lambda) can be drawn.
The polarization performance evaluation module 130 rotates the turntable under the bright field condition and the dark field condition, obtains the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction by using a plurality of pictures shot by the linear polarization image sensor, and measures the polarization performance of the linear polarization image sensor. The method and the device realize accurate measurement of related data and can accurately evaluate the performance of the linear polarization image sensor.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A method for measuring polarization performance of a linear polarization image sensor is characterized by comprising the following steps:
respectively rotating the linear polarizer under a bright field condition and a dark field condition and under each set exposure, and shooting a plurality of pictures through the polarized image sensor;
selecting a central area of a picture to obtain gray response values of pixels in different polarization directions, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction through a fitting function or a physical formula of a curve function;
and evaluating the polarization performance of the linear polarization image sensor by measuring the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
2. The method of claim 1, wherein the central region of the image is selected to obtain gray response values of pixels with different polarization directions, and the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction are obtained by a fitting function or a physical formula with a curve function, and the method specifically comprises:
in a bright field environment and a dark field environment, under a certain relative rotation angle of a turntable, a plurality of pictures are shot by using optical-lens-free equipment loaded with a linear polarization image sensor, and the gray value difference value in the same polarization direction is observed so as to adjust the fixed angle of the polarization sensor;
in a bright field environment, setting different equal-interval exposure time of a linear polarization image sensor, rotating a linear polarizer, shooting M pictures with N periods, and selecting a picture center area containing pixels with different polarization directions;
under the condition of equal interval exposure time and wavelength, rotating the turntable to obtain a sequence of gray response mean values of pixels in each polarization direction changing along with the relative rotation angle, and performing Fourier fitting to obtain a fitting function, wherein the mean value of the peak value of a fitting curve is mu y ；
Setting the rotation table under a certain specific wavelength and exposure, rotating the rotation table to obtain a first group of sequences of gray response mean values of pixels in all polarization directions along with the change of relative rotation angles, performing Fourier fitting to obtain fitting functions, and calculating phase differences among the functions in different polarization directions to obtain angle calibration values;
setting the same wavelength and exposure, rotating the rotary table to obtain a sequence of the gray response value of each polarization direction pixel along with the change of the relative rotation angle, selecting the sequence of the gray response value of each polarization direction pixel of the central area along with the change of the rotation angle for fitting, calculating the average value of the peak value and the valley value of the function, calculating the ratio of the peak value to the valley value, and obtaining the extinction ratio of each polarization direction pixel;
under the dark field environment, the exposure time and the bright field condition are controlled to be changed at equal intervals to obtain different exposure times t exp The dark signal output value of (2) and finally the average value sequence mu is obtained y.dark Calculating the gray value variance of the bright field and the dark field environment, and fitting the gray value variance
Mean value (μ) with gray scale response y -μ y.dark ) A first linear curve that varies, the first linear curve having a slope of the overall system gain K;
under the same bright field condition, setting the exposure time and wavelength with the same interval, placing the calibrated photodiode at the same position as the linear polarization image sensor, rotating the linear polarizer, and calculating the average value E of irradiance in unit area;
the exposure (mu) of the linear polarization image sensor is fitted y -μ y.dark ) With exposure time t exp Obtaining the slope of the second linear curve by the changed second linear curve function, substituting the slope into a slope physical formula, and obtaining the quantum efficiency eta;
and (3) converting the optical filters with different wavelengths to obtain different quantum efficiencies, and drawing a change relation curve of the wavelength lambda and eta (lambda).
3. The method of claim 1, wherein the selecting a central region of a picture to obtain gray response values of pixels with different polarization directions, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix, and quantum efficiencies in each polarization direction through a fitting function or a physical formula substituted into a curve function, further comprises:
under the bright field condition, setting multiple exposure time and wavelength with equal intervals, rotating the linear polarizer, rotating the angle every time, shooting a plurality of pictures by the polarized image sensor, and selecting a picture center area;
under a certain specific exposure time and a certain specific wavelength, carrying out least square fitting on gray response measured values of all pixels in each polarization direction and ideal values to obtain uniformity correction parameter matrixes and dark noise matrixes of all super pixels, wherein the super pixels are formed by combining 4 pixels in different polarization directions;
wherein, the gray scale response value obtained by the calibrated photodiode is regarded as an ideal light intensity value.
4. The method for measuring polarization performance of a linear polarization image sensor according to claim 2, wherein the rotating the turntable under a specific wavelength and exposure to obtain a first set of sequences of gray scale response mean values of pixels in each polarization direction changing with relative rotation angle specifically comprises:
controlling the exposure amount by changing the illumination intensity of the integrating sphere light source or adjusting the exposure time of the linear polarization image sensor;
rotating the high-performance linear polaroid to obtain a sequence of gray scale response mean values of all polarization directions changing along with a relative rotation angle under a certain specific exposure;
and aiming at each polarization direction, acquiring a first group of sequences of the gray response mean value of each polarization direction pixel along with the change of the relative rotation angle.
5. The method for measuring the polarization performance of the linear polarization image sensor according to claim 2, wherein the method for calculating the angle calibration value and the extinction ratio comprises:
fourier fitting is carried out on the first group of sequences to obtain a fitting function of the gray response value of each polarization direction pixel along with the change of the relative rotation angle, and the peak value and the valley value of the fitting function are calculated;
selecting a sequence of gray response values of pixels in all polarization directions changing along with the rotation angle to perform Fourier fitting, calculating phase differences among fitting functions in different polarization directions, and generating an angle calibration value;
and calculating the average value of the peak value and the valley value of the fitting function, wherein the ratio of the peak value to the valley value is the extinction ratio of the polarization array.
6. The method for measuring polarization performance of a linear polarization image sensor according to claim 2, wherein the fitting of a second linear curve of exposure of the polarization image sensor varying with exposure time, and the obtaining of quantum efficiency according to a slope of the second linear curve specifically comprises:
exposure (mu) according to polarization image sensor y -μ y.dark ) With exposure time t exp The variation fit generates a second linear curve equation,
slope to the second linear curve equation
And substituting the total system gain K, the wavelength lambda, the illumination intensity mean value E, the Planck constant h, the unit area A and the light speed c into the middle to obtain the quantum efficiency eta.
7. A polarization performance measurement system of a linear polarization image sensor, the system comprising:
the image acquisition module is used for rotating the linear polarizer under each set exposure under the bright field condition and the dark field condition respectively and shooting a plurality of images through the polarized image sensor;
the parameter calculation module is used for selecting a central area of the picture to obtain gray response values of pixels in different polarization directions, and obtaining an extinction ratio, an angle calibration value, a correction parameter matrix and quantum efficiency in each polarization direction through a fitting function or a physical formula brought into a curve function;
and the polarization performance evaluation module is used for evaluating the polarization performance of the linear polarization image sensor through the extinction ratio, the angle calibration value, the correction parameter matrix and the quantum efficiency of each polarization direction.
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| CN115272138A (en) * | 2022-09-28 | 2022-11-01 | 荣耀终端有限公司 | Image processing method and related device |
| CN117528066A (en) * | 2024-01-05 | 2024-02-06 | 浙江双元科技股份有限公司 | Linear array camera testing system and method |
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| CN115272138A (en) * | 2022-09-28 | 2022-11-01 | 荣耀终端有限公司 | Image processing method and related device |
| CN115272138B (en) * | 2022-09-28 | 2023-02-21 | 荣耀终端有限公司 | Image processing method and related device |
| CN117528066A (en) * | 2024-01-05 | 2024-02-06 | 浙江双元科技股份有限公司 | Linear array camera testing system and method |
| CN117528066B (en) * | 2024-01-05 | 2024-03-22 | 浙江双元科技股份有限公司 | Linear array camera testing system and method |
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