CN116527869A - Signal-to-noise ratio measuring method and measuring device of focal plane polarization image sensor - Google Patents
Signal-to-noise ratio measuring method and measuring device of focal plane polarization image sensor Download PDFInfo
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Abstract
The invention discloses a signal-to-noise ratio measuring method and a measuring device of a focal plane polarization image sensor, wherein the method comprises the following steps: acquiring an image data set, acquiring a first image data subset under a preset irradiance condition, and determining the average value and the time domain variance of pixel responses in the polarization principal axis directions under the preset irradiance condition based on the first image data subset; acquiring a second image data subset under a dark field condition, and determining an average value of pixel responses in the polarization principal axis directions under the dark field condition based on the second image data subset; and determining the signal to noise ratio in each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses in each polarization principal axis direction under the dark field condition and the average value and the time domain variance of the pixel responses in each polarization principal axis direction under the preset irradiance condition. The signal to noise ratio of the focal plane polarization image sensing can be accurately and efficiently measured.
Description
Technical Field
The invention belongs to the technical field of polarization imaging, and particularly relates to a signal-to-noise ratio measuring method and a measuring device of a focal plane-splitting polarization image sensor.
Background
Polarization imaging techniques can obtain polarized images of a scene. At present, the polarization imaging device is mainly divided into a time-sharing type, an amplitude-dividing type, an aperture-dividing type and a focal plane-dividing type. Compared with the former three types, the split-focal plane polarization imaging device has the advantages of compact structure, high integration level and snapshot imaging, and the core element is a split-focal plane polarization image sensor. The split focal plane polarization image sensor is realized by integrally packaging the micro-nano grating on the focal plane of the image sensor, so that the performance of the split focal plane polarization image sensor is influenced by various factors. The processing error of the micro-nano grating array, the integrated packaging error of the micro-nano grating and the image sensor, and the design and manufacturing process of the image sensor can all cause the performance of the split focal plane polarization image sensor to be reduced.
The signal-to-noise ratio of a split focal plane polarization image sensor is an important performance index of a split focal plane image sensor. For measuring the signal-to-noise ratio of the split focal plane polarization image sensing, no standard and effective measuring method exists in the prior art.
Therefore, how to accurately and efficiently measure the signal-to-noise ratio of the split focal plane polarization image sensing is a technical problem to be solved at present.
Disclosure of Invention
The invention aims to provide a signal-to-noise ratio measuring method and a measuring device of a focal plane polarization image sensor, which are used for solving the technical problem that the signal-to-noise ratio of the focal plane polarization image sensor cannot be accurately and efficiently measured in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the embodiment of the invention provides a signal-to-noise ratio measuring method of a focal plane splitting polarization image sensor, which specifically comprises the following steps:
acquiring an image data set, wherein the image data set is obtained by image shooting under dark field conditions and preset irradiance conditions when the pixel response value of each polarization main axis direction of the focal plane polarization image sensor is maximum;
acquiring a first image data subset under the preset irradiance condition, and determining the average value and the time domain variance of pixel response in the polarization principal axis direction under the preset irradiance condition based on the first image data subset; and
acquiring a second image data subset under the dark field condition, and determining an average value of pixel responses in the polarization principal axis directions under the dark field condition based on the second image data subset;
and determining the signal to noise ratio in each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses in each polarization principal axis direction under the dark field condition and the average value and the time domain variance of the pixel responses in each polarization principal axis direction under the preset irradiance condition.
In some embodiments, the preset irradiance conditions are provided in a plurality, wherein acquiring the first subset of image data under the preset irradiance conditions includes:
extracting an image which is in any preset irradiance condition and is acquired in any polarization principal axis direction from the image data set as a target image, wherein each target image comprises K pixels in any polarization principal axis direction;
using the target image to form a first image data subset of any preset irradiance condition in the direction of any polarization principal axis;
correspondingly, determining an average value of pixel responses of all polarization principal axis directions under a preset irradiance condition based on the first image data subset comprises the following steps:
for a jth preset irradiance condition in the plurality of preset irradiance conditions, calculating an average value of pixel responses in the ith polarization principal axis direction under the jth preset irradiance condition by using a first subset of image data in the ith polarization principal axis direction under the jth preset irradiance condition based on the following formula (1);
wherein y is the average value of the pixel response in the ith polarization principal axis direction under the jth preset irradiance condition, N is the number of target images acquired in the ith polarization principal axis direction under the jth preset irradiance condition, each target image comprises K pixels in the ith polarization principal axis direction,is the response value of the pixel under the current light intensity;
adding 1 to i until n is equal to i, and obtaining an average value of pixel responses in all polarization main axis directions under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the average value of pixel responses of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (1), until j is equal to m, and obtaining the average value of pixel responses of all polarization principal axis directions under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
In some embodiments, under the dark field condition, acquiring the second subset of image data includes:
extracting images acquired in any polarization principal axis direction from the image data set to serve as target images, wherein each target image comprises K pixels in any polarization principal axis direction;
using the target image to form a second image data subset in any polarization main axis direction
Accordingly, determining an average value of pixel responses in each polarization principal axis direction based on the second subset of image data, comprising:
calculating an average value of pixel responses in the i-th polarization principal axis direction using the second subset of image data in the i-th polarization principal axis direction and based on the following formula (2);
wherein y.dark is the average value of pixel responses in the ith polarization principal axis direction under dark field conditions, N is the number of target images acquired in the ith polarization principal axis direction, and each target image comprises K pixels in the ith polarization principal axis direction，Is the response value of the pixel under dark field conditions;
and (3) adding 1 to i, and obtaining an average value of pixel responses of all polarization main axis directions under dark field conditions when n is equal to i, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions.
In some embodiments, determining the temporal variance of the pixel response for each principal polarization axis direction for each irradiance condition under a preset irradiance condition includes:
utilizing the j-th preset irradiance condition to first image data subset in the i-th polarization principal axis direction, and calculating the time domain variance of the pixel response in the i-th polarization principal axis direction under the j-th preset irradiance condition based on the following formula (3);
wherein,,for the time domain variance, A, B is two optional pictures from N photographed pictures, wherein the A picture comprises K pixels in the ith polarization main axis direction, the B picture comprises K pixels in the ith polarization main axis direction, and the response value of the K (K is more than or equal to 1 and less than or equal to K) pixels of the A picture is->The response value of the kth (K is more than or equal to 1 and less than or equal to K) pixel of the picture B is +.>
Adding 1 to i until n is equal to i, and obtaining the time domain variance of pixel response of each polarization principal axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization principal axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the time domain variance of the pixel response of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (3), until j is equal to m, and obtaining the time domain variance of the pixel response of each polarization principal axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
In some embodiments, determining the signal-to-noise ratio in each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses in each polarization principal axis direction under the dark field condition, and the average value and the time domain variance of the pixel responses in each polarization principal axis direction under the preset irradiance condition includes:
calculating the signal to noise ratio of the ith polarization principal axis direction under the jth preset irradiance condition according to the average value and the time domain variance of the pixel response of the ith polarization principal axis direction under the jth preset irradiance condition and the average value of the pixel response of the ith polarization principal axis direction under the dark field condition and based on the following formula (3);
SNR＝(y-y.dark)/σ y ； (4)
wherein SNR is signal-to-noise ratio, σ y Is the time domain standard deviation;
adding 1 to i until n is equal to i, and obtaining the signal to noise ratio of each polarization main axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization main axis direction, and calculating the signal to noise ratio of the i polarization main axis direction under the j preset irradiance condition based on the following formula (4), until j is equal to m, and obtaining the signal to noise ratio of each polarization main axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
In some embodiments, the picture is taken by a non-optical lens device of the split focal plane polarized image sensor.
In some embodiments, the irradiance of the parallel uniform light impinging on the photosurface of the split focal plane polarized image sensor is varied by adjusting parameters of the parallel uniform light source, parameters of the first optical device, and parameters of the second optical device.
Correspondingly, the invention also discloses a signal-to-noise ratio measuring device of the focal plane polarization image sensor. The device comprises:
an adjustable parallel uniform light source, a first optical device, a rotatable high-performance linear polaroid, a high-precision turntable, a second optical device and an optical lens-free device of a focal plane polarization image sensor are sequentially arranged along an optical platform;
the adjustable parallel uniform light source is used for emitting uniform light, and the uniform light irradiates the rotatable high-performance linear polarizing plate to form linear polarized light with adjustable polarization direction;
the optical lens device of the focal plane polarization image sensor is used for shooting polarized uniform light images;
the high-precision turntable is used for driving the rotatable high-performance linear polaroid to rotate relative to the focal plane polarization image sensor, collecting pixel response values corresponding to the polarization main axis directions after each rotation, and finding out the maximum pixel response value corresponding to the polarization main axis directions.
In some embodiments, the apparatus further comprises:
the lifting platform and the five-axis displacement platform are used for adjusting the spatial positions of the high-precision turntable, the rotatable high-performance linear polaroid and the focal plane-splitting polarized image sensor;
and a vertical polished rod for providing a vertical reference.
In some embodiments, the parallel uniform light source is an adjustable integrating sphere, and the adjustable integrating sphere emits uniform light, and after being processed, the parallel uniform light with stable light intensity is output.
The beneficial effects are that:
the signal-to-noise ratio is calculated through a formula, and the problem of signal-to-noise ratio parameter measurement of the focal plane polarization image sensor is solved. The invention has the advantages of high measurement precision and simple measurement process.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the application and to provide a further understanding of the application with regard to the other features, objects and advantages of the application. The drawings of the illustrative embodiments of the present application and their descriptions are for the purpose of illustrating the present application and are not to be construed as unduly limiting the present application. In the drawings:
fig. 1 is a schematic flow chart of a signal-to-noise ratio measurement method of a focal plane-splitting polarization image sensor provided in an embodiment of the present application;
FIG. 2 is a schematic flow chart of a signal-to-noise ratio measurement method of another focal plane-separated polarization image sensor according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a signal-to-noise ratio measurement device of a focal plane-splitting polarization image sensor according to an embodiment of the present application.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be briefly described below with reference to the accompanying drawings and the description of the embodiments or the prior art, and it is obvious that the following description of the structure of the drawings is only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art. It should be noted that the description of these examples is for aiding in understanding the present invention, but is not intended to limit the present invention.
Examples:
as shown in fig. 1, the present embodiment provides a flow chart of a signal-to-noise ratio measurement method of a focal plane-splitting polarization image sensor, where the method includes:
s101, acquiring an image data set, wherein the image data set is obtained by image shooting under dark field conditions and preset irradiance conditions when pixel response values of the focal plane polarization image sensors in the directions of polarization principal axes are maximum.
Specifically, through the signal-to-noise ratio parameter measuring device of the focal plane polarization image sensor, the rotatable high-performance linear polaroid can be driven by rotation of the turntable, and the adjustment of the polarization direction of parallel uniform light entering the photosensitive surface of the focal plane polarization image sensor is realized. The turntable drives the rotatable high-performance linear polaroid to perform rotary motion relative to the photosensitive surface of the focal plane polarization image sensor. And positioning the turntable to a position with the maximum preset polarization main axis direction pixel response value. The pixel response value is read by the optical device, and the value under each rotation angle is calculated after the pixel response value rotates for one circle, so that the relation between the response value and the rotation angle can be obtained, then the angle where the maximum response value is located is found, and then the pixel response value is rotated to the angle. And acquiring pixel response values corresponding to the polarization main axis directions after each rotation, finding out the maximum pixel response value corresponding to each polarization main axis direction, and recording and positioning the position of the turntable when the maximum pixel response value is located. And acquiring an image data set by using an optical lens with no light, wherein the optical lens is provided with a focal plane polarization image sensor, and the image data set is obtained by shooting an image under dark field conditions and preset irradiance conditions when the pixel response value of each polarization main axis direction of the focal plane polarization image sensor is maximum.
S102, under the preset irradiance condition, acquiring a first image data subset, and determining the average value and the time domain variance of pixel responses in the polarization principal axis directions under the preset irradiance condition based on the first image data subset; and under the dark field condition, acquiring a second image data subset, and determining an average value of pixel responses of the polarization main axis directions under the dark field condition based on the second image data subset.
In particular, the dark field conditions mentioned in this application are no light environments, only one. Different irradiance conditions refer to the case where the output of the integrating sphere is of different intensities, and in the case of camera overexposure, there may be many irradiance conditions, such as 100lux, 500lux, 1000lux, etc. Under the preset irradiance condition, that is, the operator can select the irradiance condition by himself, one irradiance condition or a plurality of irradiance conditions can be adopted. If the operator selects 100lux, 500lux and 1000lux light intensities, determining the average value and the time domain variance of the pixel response in the preset polarization main axis direction under the current 100lux light intensity. And the average value and the time domain variance of the pixel response in the preset polarization principal axis direction at the subsequent 500lux and 1000lux light intensities. And under the dark field condition, determining the average value of the pixel response in the preset polarization main axis direction. Acquiring a first image data subset under the preset irradiance condition, and determining the average value and the time domain variance of pixel response in the polarization principal axis direction under the preset irradiance condition based on the first image data subset; and under the dark field condition, acquiring a second image data subset, and determining an average value of pixel responses of the polarization main axis directions under the dark field condition based on the second image data subset.
To determine the average value of the pixel response for each principal polarization axis direction at a predetermined irradiance, in this embodiment,
the preset irradiance conditions are provided in plurality, and under the preset irradiance conditions, the first image data subset is obtained as follows: extracting an image which is in any preset irradiance condition and is acquired in any polarization principal axis direction from the image data set as a target image, wherein each target image comprises K pixels in any polarization principal axis direction; using the target image to form a first image data subset of any preset irradiance condition in the direction of any polarization principal axis;
determining an average value of pixel responses of all polarization principal axis directions under a preset irradiance condition based on the first image data subset, wherein the average value comprises the following steps:
for a jth preset irradiance condition in the plurality of preset irradiance conditions, calculating an average value of pixel responses in the ith polarization principal axis direction under the jth preset irradiance condition by using a first subset of image data in the ith polarization principal axis direction under the jth preset irradiance condition based on the following formula (1);
wherein y is the average value of the pixel response in the ith polarization principal axis direction under the jth preset irradiance condition, N is the number of target images acquired in the ith polarization principal axis direction under the jth preset irradiance condition, K pixels in the ith polarization principal axis direction are arranged in the selected area of the picture, the nth (1N) picture in the ith polarization principal axis direction is recorded, and the response value of the kth (1K) pixel is
Adding 1 to i until n is equal to i, and obtaining an average value of pixel responses in all polarization main axis directions under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions; and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the average value of pixel responses of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (1), until j is equal to m, and obtaining the average value of pixel responses of all polarization principal axis directions under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
After calculation is completed under the preset irradiance condition, a sequence of the response average value of all the polarization principal axis direction pixels along with the variation of irradiance is obtained, and for all the polarization principal axis directions, the sequence of the response average value of all the polarization principal axis direction pixels along with the variation of irradiance can be obtained by adopting the method.
To determine the temporal variance of the pixel response for each principal polarization axis direction for each irradiance condition under a preset irradiance condition, comprising:
utilizing the j-th preset irradiance condition to first image data subset in the i-th polarization principal axis direction, and calculating the time domain variance of the pixel response in the i-th polarization principal axis direction under the j-th preset irradiance condition based on the following formula (3);
wherein,,for the time domain variance, A, B is two optional pictures from N photographed pictures, wherein the A picture comprises K pixels in the ith polarization main axis direction, the B picture comprises K pixels in the ith polarization main axis direction, and the response value of the K (K is more than or equal to 1 and less than or equal to K) pixels of the A picture is->The response value of the kth (K is more than or equal to 1 and less than or equal to K) pixel of the picture B is +.>
Adding 1 to i until n is equal to i, and obtaining the time domain variance of pixel response of each polarization principal axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization principal axis directions; and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the time domain variance of the pixel response of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (3), until j is equal to m, and obtaining the time domain variance of the pixel response of each polarization principal axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
The sequence that the response time domain variance of each polarization principal axis direction pixel changes along with irradiance is obtained by adopting the method.
Acquiring a second subset of image data under dark field conditions, comprising: extracting images acquired in any polarization principal axis direction from the image data set to serve as target images, wherein each target image comprises K pixels in any polarization principal axis direction; and determining an average value of pixel responses in each polarization principal axis direction based on the second image data subset corresponding to the second image data subset in any polarization principal axis direction by using the target image, wherein the average value comprises the following components: calculating an average value of pixel responses in the i-th polarization principal axis direction using the second subset of image data in the i-th polarization principal axis direction and based on the following formula (2);
wherein y.dark is the average value of pixel responses in the ith polarization principal axis direction under dark field conditions, N is the number of target images acquired in the ith polarization principal axis direction, each target image comprises K pixels in the ith polarization principal axis direction,is the response value of the pixel under dark field conditions;
and (3) adding 1 to i, and obtaining an average value of pixel responses of all polarization main axis directions under dark field conditions when n is equal to i, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions.
S103, determining the signal-to-noise ratio of each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses of each polarization principal axis direction under the dark field condition, and the average value and the time domain variance of the pixel responses of each polarization principal axis direction under the preset irradiance condition.
In order to accurately measure the signal-to-noise ratio parameters of the split focal plane polarized image sensor, in some embodiments, the irradiance of the parallel uniform light impinging on the photosurface of the split focal plane polarized image sensor may be varied by adjusting parameters of the adjustable parallel uniform light source, adjusting parameters of the first optical device, adjusting parameters of the second optical device. The first optical device and the second optical device refer to devices capable of changing parameters of the parallel uniform light emitted by the parallel uniform light source, and can be removed when no use requirement exists.
In order to determine a signal-to-noise ratio in each polarization principal axis direction under a preset irradiance condition based on an average value of pixel responses in each polarization principal axis direction under a dark field condition and an average value and a time domain variance of pixel responses in each polarization principal axis direction under the preset irradiance condition, the method comprises the following steps:
calculating the signal to noise ratio of the ith polarization principal axis direction under the jth preset irradiance condition according to the average value and the time domain variance of the pixel response of the ith polarization principal axis direction under the jth preset irradiance condition and the average value of the pixel response of the ith polarization principal axis direction under the dark field condition and based on the following formula (3);
SNR＝(y-y.dark)/σ y ； (4)
wherein SNR is signal-to-noise ratio, σ y Is the time domain standard deviation;
adding 1 to i until n is equal to i, and obtaining the signal to noise ratio of each polarization main axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions; and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization main axis direction, and calculating the signal to noise ratio of the i polarization main axis direction under the j preset irradiance condition based on the following formula (4), until j is equal to m, and obtaining the signal to noise ratio of each polarization main axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
By adopting the method, the signal-to-noise ratio can be accurately measured, and the sequence of the signal-to-noise ratio of each polarization main axis direction along with irradiance change can be obtained.
In order to achieve the above objective, the present application further provides a signal-to-noise ratio measurement device of a focal plane splitting polarization image sensor, as shown in fig. 2, including:
an adjustable parallel uniform light source, a first optical device, a rotatable high-performance linear polaroid, a high-precision turntable, a second optical device and an optical lens-free device of a focal plane polarization image sensor are sequentially arranged along an optical platform;
the adjustable parallel uniform light source is used for emitting uniform light, and the uniform light irradiates the rotatable high-performance linear polarizing plate to form linear polarized light with adjustable polarization direction;
the optical lens device of the focal plane polarization image sensor is used for shooting polarized uniform light images;
the high-precision turntable is used for driving the rotatable high-performance linear polaroid to rotate.
The lifting platform and the five-axis displacement platform are used for adjusting the spatial positions of the high-precision turntable, the rotatable high-performance linear polaroid and the focal plane-splitting polarized image sensor;
and a vertical polished rod for providing a vertical reference.
The parallel uniform light source is an adjustable integrating sphere, the adjustable integrating sphere emits uniform light, and the parallel uniform light with stable light intensity is output after the treatment.
Specifically, the signal-to-noise ratio parameter measuring device of the focal plane splitting polarization image sensor comprises: the device comprises an adjustable parallel uniform light source, a first optical device 1, a rotatable high-performance linear polaroid, a lifting table, a high-precision turntable, a five-axis displacement platform, a vertical polished rod, a second optical device 2, a non-optical lens device with a focal plane polarization image sensor and an optical platform; the lifting platform and the five-axis displacement platform are used for adjusting the spatial positions of the high-precision turntable, the linear polaroid and the focal plane polarization image sensor, and the vertical polished rod is used for providing vertical reference. The positional relationship of the devices on the optical path is as follows: all devices except the optical platform are placed on the optical platform, parallel uniform light emitted by a uniform light source can be leveled, sequentially passes through the first optical equipment 1, the rotatable high-performance linear polaroid and the second optical equipment 2, and finally irradiates the photosensitive surface of the tested split focal plane polarized image sensor.
The signal-to-noise ratio parameter measuring device of the focal plane-separated polarized image sensor comprises: the turntable rotates to drive the rotatable high-performance linear polaroid to realize the adjustment of the polarization direction of the parallel uniform light incident to the photosensitive surface of the split focal plane polarization image sensor.
The invention provides a signal-to-noise ratio measuring device and a signal-to-noise ratio measuring method for a focal plane polarization image sensor, which solve the problem that the signal-to-noise ratio parameter of the focal plane polarization image sensor is difficult to measure in the prior art.
In order to further explain the technical idea of the invention, the technical scheme of the invention is described with specific application scenes.
The invention discloses a signal-to-noise ratio parameter measurement method of a focal plane-splitting polarization image sensor, which adopts any calibration device.
In this embodiment, an adjustable integrating sphere with collimator added is selected as the parallel uniform light source. An adjustable integrating sphere, a rotatable high-performance linear polarizer and an optical lens device with a focal plane polarization image sensor are arranged along an optical axis.
The adjustable integrating sphere emits uniform light, and the uniform light with stable light intensity is output after the uniform light is processed by the collimator. The parallel uniform light irradiates the rotatable high-performance linear polaroid to form linearly polarized light with adjustable polarization direction.
The measuring steps of the signal-to-noise ratio parameter measuring method in the focal plane-splitting polarization image sensor disclosed by the invention are as shown in fig. 3:
step 1: the turntable drives the rotatable high-performance linear polaroid to rotate clockwise by an increment of 1 DEG in step length, simultaneously observes the pixel response of each polarization main axis direction, rotates 360 times in total, and finds the position with the largest pixel response of each polarization main axis direction.
Step 2: the rotatable high-performance linear polaroid rotates to a position with maximum response of a certain polarization main axis direction pixel, the light intensity of the adjustable integrating sphere is adjusted, from a dark field condition, the light intensity of the adjustable integrating sphere is increased by 500lux each time until the sub-focal plane image sensor is overexposed, and 20 pictures are taken without optical lens equipment which is provided with the sub-focal plane polarization image sensor each time the light intensity is increased. Selecting a picture comprising the pixel area in the polarization main axis direction, and calculating the average value and the time domain variance of the pixel response in the polarization main axis direction when the current light intensity in the polarization main axis direction is calculated. Recording the response value of the ith (i is less than or equal to 140000) pixel of the nth (n is less than or equal to 1 and less than or equal to 10) picture under the light intensity of a certain polarization main axis direction L (L is less than or equal to 0 and less than or equal to overexposure intensity) as followsThe bias isThe corresponding average value y of the pixels in the vibration axis direction at the light intensity is: />Similarly, the corresponding average y.dark of the pixels in the polarization principal axis direction under dark field conditions is calculated. Selecting two pictures respectively marked as A and B from ten pictures, and marking time domain variance of the polarization main axis direction in the light intensity>The method comprises the following steps: />
The method is adopted for each polarization principal axis direction, and finally, a sequence that the pixel response average value and the time domain variance of each polarization principal axis direction change along with the light intensity is obtained.
Step 3: bringing the sequence obtained in step (2) into the formula snr= (y-y.dark)/σ y And obtaining a sequence of the signal-to-noise ratio of each polarization main axis direction along with the change of the light intensity, namely obtaining the signal-to-noise ratio of each polarization main axis direction.
The invention provides a signal-to-noise ratio measuring device and a measuring method of a plane polarization image sensor, which are used for solving the problem of signal-to-noise ratio parameter measurement of a focal plane polarization image sensor by adjusting the intensity of light emitted by a parallel uniform light source and the angle of a high-performance rotatable linear polaroid to obtain the relation of pixel response average value, pixel response time domain variance and irradiance of each polarization main axis direction and then calculating the signal-to-noise ratio through a formula. The invention has the advantages of high measurement precision and simple measurement process.
Finally, it should be noted that: the foregoing description is only of the preferred embodiments of the invention and is not intended to limit the scope of the invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A signal-to-noise ratio measurement method of a split focal plane polarization image sensor, the method comprising:
acquiring an image data set, wherein the image data set is obtained by image shooting under dark field conditions and preset irradiance conditions when the pixel response value of each polarization main axis direction of the focal plane polarization image sensor is maximum;
acquiring a first image data subset under the preset irradiance condition, and determining the average value and the time domain variance of pixel response in the polarization principal axis direction under the preset irradiance condition based on the first image data subset; and
acquiring a second image data subset under the dark field condition, and determining an average value of pixel responses in the polarization principal axis directions under the dark field condition based on the second image data subset;
and determining the signal to noise ratio in each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses in each polarization principal axis direction under the dark field condition and the average value and the time domain variance of the pixel responses in each polarization principal axis direction under the preset irradiance condition.
2. The measurement method of claim 1, wherein the preset irradiance condition is provided in plurality, wherein acquiring the first subset of image data under the preset irradiance condition comprises:
extracting an image which is in any preset irradiance condition and is acquired in any polarization principal axis direction from the image data set as a target image, wherein each target image comprises K pixels in any polarization principal axis direction;
using the target image to form a first image data subset of any preset irradiance condition in the direction of any polarization principal axis;
correspondingly, determining an average value of pixel responses of all polarization principal axis directions under a preset irradiance condition based on the first image data subset comprises the following steps:
for a jth preset irradiance condition in the plurality of preset irradiance conditions, calculating an average value of pixel responses in the ith polarization principal axis direction under the jth preset irradiance condition by using a first subset of image data in the ith polarization principal axis direction under the jth preset irradiance condition based on the following formula (1);
wherein y is the average value of the pixel response in the ith polarization principal axis direction under the jth preset irradiance condition, N is the number of target images acquired in the ith polarization principal axis direction under the jth preset irradiance condition, each target image comprises K pixels in the ith polarization principal axis direction,is the response value of the pixel under the current light intensity;
adding 1 to i until n is equal to i, and obtaining an average value of pixel responses in all polarization main axis directions under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the average value of pixel responses of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (1), until j is equal to m, and obtaining the average value of pixel responses of all polarization principal axis directions under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
3. The measurement method according to claim 1, wherein acquiring the second subset of image data under the dark field condition comprises:
extracting images acquired in any polarization principal axis direction from the image data set to serve as target images, wherein each target image comprises K pixels in any polarization principal axis direction;
using the target image to form a second image data subset in any polarization main axis direction
Accordingly, determining an average value of pixel responses in each polarization principal axis direction based on the second subset of image data, comprising:
calculating an average value of pixel responses in the i-th polarization principal axis direction using the second subset of image data in the i-th polarization principal axis direction and based on the following formula (2);
wherein y.dark is the average value of pixel responses in the ith polarization principal axis direction under dark field conditions, N is the number of target images acquired in the ith polarization principal axis direction, each target image comprises K pixels in the ith polarization principal axis direction,is the response value of the pixel under dark field conditions;
and (3) adding 1 to i, and obtaining an average value of pixel responses of all polarization main axis directions under dark field conditions when n is equal to i, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions.
4. The method of claim 1, wherein determining the temporal variance of the pixel response for each principal polarization axis direction for each irradiance condition under the predetermined irradiance condition comprises:
utilizing the j-th preset irradiance condition to first image data subset in the i-th polarization principal axis direction, and calculating the time domain variance of the pixel response in the i-th polarization principal axis direction under the j-th preset irradiance condition based on the following formula (3);
wherein,,for the time domain variance, A, B is two optional pictures from N photographed pictures, wherein the A picture comprises K pixels in the ith polarization main axis direction, the B picture comprises K pixels in the ith polarization main axis direction, and the response value of the K (K is more than or equal to 1 and less than or equal to K) pixels of the A picture is->The response value of the kth (K is more than or equal to 1 and less than or equal to K) pixel of the picture B is +.>
Adding 1 to i until n is equal to i, and obtaining the time domain variance of pixel response of each polarization principal axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization principal axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization principal axis direction, and calculating the time domain variance of the pixel response of the i polarization principal axis direction under the j preset irradiance condition based on the following formula (3), until j is equal to m, and obtaining the time domain variance of the pixel response of each polarization principal axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
5. The method of measuring according to claim 1, wherein determining the signal-to-noise ratio in each polarization principal axis direction under the preset irradiance condition based on the average value of the pixel responses in each polarization principal axis direction under the dark field condition, and the average value and the time domain variance of the pixel responses in each polarization principal axis direction under the preset irradiance condition, comprises:
calculating the signal to noise ratio of the ith polarization principal axis direction under the jth preset irradiance condition according to the average value and the time domain variance of the pixel response of the ith polarization principal axis direction under the jth preset irradiance condition and the average value of the pixel response of the ith polarization principal axis direction under the dark field condition and based on the following formula (3);
SNR＝(y-y.dark)/σ y ； (4)
wherein SNR is signal-to-noise ratio, σ y Is the time domain standard deviation;
adding 1 to i until n is equal to i, and obtaining the signal to noise ratio of each polarization main axis direction under any preset irradiance condition, wherein the initial value of i is 1, and n is the total number of the polarization main axis directions;
and (3) adding 1 to j, and reusing the first image data subset of the j preset irradiance condition in the i polarization main axis direction, and calculating the signal to noise ratio of the i polarization main axis direction under the j preset irradiance condition based on the following formula (4), until j is equal to m, and obtaining the signal to noise ratio of each polarization main axis direction under each preset irradiance condition, wherein the initial value of j is 1, and m is the total number of the preset irradiance conditions.
6. A method of measuring according to claim 3, characterized in that the method further comprises:
the picture taking is performed by the afocal optical lens apparatus of the split focal plane polarized image sensor.
7. The measurement method according to claim 1, characterized in that the method further comprises:
the irradiance of the parallel uniform light irradiated to the photosensitive surface of the split focal plane polarization image sensor is changed by adjusting parameters of the parallel uniform light source, parameters of the first optical device and parameters of the second optical device.
8. A signal-to-noise ratio measurement device of a split focal plane polarization image sensor, comprising:
an adjustable parallel uniform light source, a first optical device, a rotatable high-performance linear polaroid, a high-precision turntable, a second optical device and an optical lens-free device of a focal plane polarization image sensor are sequentially arranged along an optical platform;
the adjustable parallel uniform light source is used for emitting uniform light, and the uniform light irradiates the rotatable high-performance linear polarizing plate to form linear polarized light with adjustable polarization direction;
the optical lens device of the focal plane polarization image sensor is used for shooting polarized uniform light images;
the high-precision turntable is used for driving the rotatable high-performance linear polaroid to rotate relative to the focal plane polarization image sensor, collecting pixel response values corresponding to the polarization main axis directions after each rotation, and finding out the maximum pixel response value corresponding to the polarization main axis directions.
9. The measurement device of claim 8, wherein the device further comprises:
the lifting platform and the five-axis displacement platform are used for adjusting the spatial positions of the high-precision turntable, the rotatable high-performance linear polaroid and the focal plane-splitting polarized image sensor;
and a vertical polished rod for providing a vertical reference.
10. The measuring device of claim 8, wherein the measuring device comprises a sensor,
the parallel uniform light source is an adjustable integrating sphere, the adjustable integrating sphere emits uniform light, and the parallel uniform light with stable light intensity is output after the treatment.
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