Polarization adjustment assembly, polarization imaging device and polarization imaging method

Abstract

The application belongs to the technical field of polarization imaging, and particularly relates to a polarization adjusting assembly, a polarization imaging device and a polarization imaging method. The polarization imaging device sequentially comprises, from an object side to an image side, an imaging lens group located in front of a focal plane of an imaging detector, a polarization adjusting assembly, a linear polarizer and the imaging detector. The imaging lens group is used for focusing light on the focal plane of the imaging detector. The polarization adjusting assembly is used for adjusting a polarization direction of light emitted from the imaging lens group. The polarization adjusting assembly comprises a first polarization grating and a second polarization grating. The linear polarizer is used for performing polarization filtering on the light emitted from the polarization adjusting assembly. The imaging detector is used for acquiring image information of an object to be imaged. A controller is used for controlling the imaging detector to acquire image information when the first polarization grating or the second polarization grating moves to at least three specific positions in a preset stroke range, and calculating polarization state information of the object to be imaged by using the acquired image information and position information of the specific positions. The polarization adjusting device has high speed, practicability and accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polarization imaging, in particular to a polarization adjusting assembly, a polarization imaging device and a polarization imaging method. BACKGROUND

[0002] Polarization is one of the important characteristics of electromagnetic waves. The polarization state of light waves changes in the process of interaction with any matter in the ground and atmosphere, which is related to the properties of the matter itself and the angle of incident light. Polarization imaging technology can extract two-dimensional image information and polarization state information of the target at the same time. Through data processing, the information is usually represented as degree of polarization (DOP) and angle of polarization (AOP). Polarization information usually reflects the surface characteristics, shape, material and roughness of the matter itself. Therefore, the combination of polarization and imaging can obtain more comprehensive target and background information, effectively improve the ability to detect and identify targets, and has a wide range of application scenarios in military reconnaissance, camouflage, unmanned aerial vehicle remote sensing and other fields.

[0003] The key to polarization imaging technology lies in the extraction method of polarization information, which usually includes time-sharing, amplitude-sharing, aperture-sharing and focal plane-sharing methods. Time-sharing polarization imaging usually needs to obtain imaging information of different polarization angles under the same target scene according to a certain time sequence to extract effective polarization degree and polarization angle information. Therefore, in the scene where the target or image acquisition device moves, the time-sharing method has a deficiency in the speed of obtaining imaging information of different polarization angles.

[0004] In the prior art, an angle rotating device is used to drive a linear polarizer placed in an imaging lens to rotate to obtain imaging information of different polarization angles, so as to demodulate the polarization degree and polarization angle imaging results. However, this method still needs a long time to complete the measurement of polarization information due to the large stroke of the angle rotating device, and cannot meet the requirement of accurately detecting the polarization information of the target under high-speed motion. SUMMARY

[0005] The present application provides a polarization adjusting assembly, a polarization imaging device and a polarization imaging method, which can solve the technical problem that the polarization adjusting device in the prior art cannot adjust the polarization state at high speed.

[0006] In a first aspect, the present application provides a polarization adjusting assembly for adjusting the polarization direction of incident light, the polarization adjusting assembly comprising a first polarization grating and a second polarization grating,

[0007] The surfaces of the first polarization grating and the second polarization grating have the same one-dimensional subwavelength periodic structure, and the grating period directions of the first polarization grating and the second polarization grating are the same,

[0008] The first polarization grating and the second polarization grating can be relatively displaced in a grating period direction,

[0009] The polarization adjustment assembly further comprises a driving assembly and a controller,

[0010] The driving assembly is configured to drive the first polarization grating or the second polarization grating to move so as to cause the first polarization grating and the second polarization grating to be relatively displaced in the grating period direction,

[0011] The controller is configured to control the driving assembly to drive the first polarization grating or the second polarization grating to reciprocate within a preset stroke range.

[0012] According to the embodiment of the first aspect of the present application, the preset stroke satisfies that the first polarization grating is always within the effective light aperture of the second polarization grating.

[0013] According to any one of the foregoing embodiments of the first aspect of the present application, the preset stroke is equal to one half of the polarization grating period.

[0014] In a second aspect, the embodiments of the present application provide a polarization imaging device, which comprises, in order from an object side to an image side:

[0015] An imaging lens group, located in front of a focal plane of an imaging detector, configured to focus light on the focal plane of the imaging detector,

[0016] A polarization adjustment assembly as described above, configured to adjust a polarization direction of light exiting from the imaging lens group,

[0017] A linear polarizer, configured to polarize and filter light exiting from the polarization adjustment assembly,

[0018] An imaging detector, configured to acquire image information of an object to be imaged,

[0019] The controller is further configured to control the imaging detector to acquire image information when the first polarization grating or the second polarization grating moves to at least three specific positions within the preset stroke range, and to calculate polarization state information of the object to be imaged by using the acquired image information and position information of the specific positions.

[0020] According to any one of the foregoing embodiments of the second aspect of the present application, the controller controls the imaging detector to acquire image information once every time the first polarization grating or the second polarization grating reaches a specific position.

[0021] According to any one of the foregoing embodiments of the second aspect of the present application, the calculation of the polarization state information of the object to be imaged by using the acquired image information and the position information of the specific positions comprises:

[0022] Extracting three corresponding image intensity information from the image information acquired at the three different specific positions,

[0023] The polarization state information of the object to be imaged is calculated using the extracted image intensity information and the corresponding position information of three specific locations.

[0024] According to any of the foregoing embodiments of the second aspect of this application, the controller uses multiple sets of data information to calculate the polarization state information of the object to be imaged multiple times. Each set of data information includes three corresponding image intensity information and three corresponding position information of specific locations extracted from three consecutive image information. The position information of the three specific locations in different sets of data information may be the same or completely different.

[0025] According to any of the foregoing embodiments of the second aspect of this application, when the first polarization grating or the second polarization grating reaches different specific positions, the phase delay of the light emitted from the polarization adjustment component is different.

[0026] Thirdly, embodiments of this application provide a polarization imaging method applied to the polarization imaging device described above, characterized in that: it includes...

[0027] Determine at least three specific locations within the preset travel range.

[0028] Control the first polarization grating or the second polarization grating to reciprocate within a preset travel range.

[0029] The controller instructs the imaging detector to acquire image information every time the first or second polarization grating reaches a specific position.

[0030] The controller uses the acquired image information and position information at a specific location to calculate the polarization state information of the object to be imaged.

[0031] When the first polarization grating or the second polarization grating reaches different specific positions, the phase delay of the light emitted from the polarization adjustment component is different.

[0032] According to an embodiment of the third aspect of this application, the controller calculates the polarization state information of the object to be imaged using the acquired image information and the position information of a specific location, including...

[0033] Based on the image information acquired by the imaging detector in three consecutive acquisitions and the position information of a specific location when the image information was acquired, the controller calculates the polarization state information of the object to be imaged using the following formula:

[0034] (1)

[0035] (2)

[0036] (3)

[0037] in, This represents the relative displacement between the first polarization grating and the second polarization grating, i.e., the positional information at a specific location.

[0038] This represents the polarization grating period of the first polarization grating and the second polarization grating.

[0039] This indicates the rotation angle of the polarization direction of the light after polarization adjustment by the polarization adjustment component.

[0040] This indicates that the first polarization grating and the second polarization grating interact. Image intensity information acquired at a specific location relative to displacement.

[0041] DOP represents the degree of polarization of the object to be imaged, and AOP represents the angle of polarization of the object to be imaged.

[0042] According to any of the foregoing embodiments of the third aspect of this application, the preset stroke satisfies that the first polarization grating never deviates from the effective light transmission aperture of the second polarization grating.

[0043] According to any of the foregoing embodiments of the third aspect of this application, the preset travel distance is equal to half of the polarization grating period, and three specific positions are taken within the preset travel distance range.

[0044] The polarization adjustment component of this application uses horizontal movement to drive the first polarization grating or the second polarization grating to move. Compared with the rotating polarization grating method in the prior art, the polarization adjustment component of this application uses horizontal movement to drive the first polarization grating or the second polarization grating to perform translational motion, which can improve the movement speed and thus improve the speed of polarization state adjustment, making it suitable for conditions that require the use of high frame rate cameras.

[0045] The polarization imaging device of this application embodiment adopts the polarization adjustment component as described above. It is a high-speed polarization imaging device based on polarization grating modulation. Especially when using a high frame rate camera, the polarization demodulation imaging frame rate of the polarization imaging device is related to the motion frequency f of the driving component. The limit can reach 4f, which is only limited by the camera frame rate and sensitivity. It can basically reach the level of light intensity imaging frame rate, which solves the traditional shortcomings of the existing time-division polarization imaging method. It has high speed, practicality and accuracy. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the polarization adjustment component provided in the embodiments of this application;

[0047] Figure 2 This is a schematic diagram of the polarization imaging device provided in the embodiments of this application. Detailed Implementation

[0048] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0049] Please see Figure 1 In a first aspect, embodiments of this application disclose a polarization adjustment component 100 for adjusting the polarization direction of incident light. The polarization adjustment component 100 includes a first polarization grating 110 and a second polarization grating 120. The first polarization grating 110 and the second polarization grating 120 have the same structure, and their surfaces have the same unidimensional subwavelength periodic structure. In the optical path structure where the polarization direction of the incident light needs to be adjusted, the first polarization grating 110 and the second polarization grating 120 are coaxially arranged, and the first polarization grating 110 and the second polarization grating 120 are... The gratings 120 have the same grating period direction; the first polarization grating 110 and the second polarization grating 120 can undergo relative displacement in the grating period direction; the polarization adjustment component 100 also includes a driving component 130 and a controller 140. The driving component 130 is used to drive the first polarization grating 110 or the second polarization grating to move so that the first polarization grating 110 and the second polarization grating 120 undergo relative displacement in the grating period direction. The controller 140 is used to control the driving component 130 to drive the first polarization grating 110 or the second polarization grating to reciprocate within a preset stroke range. During the relative displacement between the first polarization grating 110 and the second polarization grating 120, the polarization state of the incident light is modulated. By rapidly moving the first polarization grating 110 or the second polarization grating 120 by the driving component 130, rapid modulation of the polarization state of the incident light can be achieved. Compared to the rotating polarization grating method in the prior art, the polarization adjustment component 100 of this application uses a horizontal movement to drive the first polarization grating 110 or the second polarization grating 120 to perform translational motion, which can improve the movement speed and thus improve the speed of polarization state adjustment, making it suitable for conditions that require the use of high frame rate cameras.

[0050] The preset travel range is determined according to actual conditions. The preset travel range ensures that the first polarization grating never deviates from the effective light-passing aperture of the second polarization grating, and does not affect the light transmission of the entire optical path system. In some embodiments, the preset travel range is equal to half of the polarization grating period; the first polarization grating 110 or the second polarization grating 120 has the smallest travel range within this preset travel range, which can improve the movement efficiency of the first polarization grating 110 or the second polarization grating 120, thereby improving the efficiency of adjusting the polarization state of the incident light.

[0051] Please see Figure 2 Secondly, embodiments of this application provide a polarization imaging device 200, which includes, from the object side to the image side, an imaging lens group 210, a polarization adjustment component 100 as described above, a linear polarizer 220, and an imaging detector 230. The imaging lens group 210 is located in front of the focal plane of the imaging detector 230 and is used to focus light onto the focal plane of the imaging detector 230. The polarization adjustment component 100 is used to adjust the polarization direction of light emitted from the imaging lens group. The linear polarizer 220 is used to perform polarization filtering on the light emitted from the polarization adjustment component 100. The imaging detector 230 is used to acquire image information of the object to be imaged. The controller 140 is also used to control the imaging detector 230 to acquire image information when the first polarization grating 110 or the second polarization grating 120 moves to at least three specific positions within a preset travel range, and to calculate the polarization state information of the object to be imaged using the acquired image information and the position information of the specific positions. The specific position is selected based on the actual situation. When the first polarization grating 110 or the second polarization grating 120 moves to the specific position, the imaging detector 230 performs the aforementioned preset imaging action. The polarization imaging device of this application embodiment is a high-speed polarization imaging device based on polarization grating modulation. Especially under the condition of using a high frame rate camera, the polarization demodulation imaging frame rate of the polarization imaging device is related to the movement frequency f of the driving component 130, and can reach a limit of 4f. It is only limited by the camera frame rate and sensitivity, and can basically reach the level of light intensity imaging frame rate. It solves the traditional shortcomings of the existing time-division polarization imaging method and has high speed, practicality and accuracy.

[0052] In some embodiments, the controller 140 controls the imaging detector 230 to acquire image information of the object to be imaged only while controlling the first polarization grating 110 or the second polarization grating 120 to move along the grating period direction. The controller 140 selects image information acquired at several different specific locations each time to calculate the polarization state information of the object to be imaged.

[0053] In some embodiments, the controller 140 controls the imaging detector 230 to acquire image information once each time the first polarization grating 110 or the second polarization grating 120 reaches a specific position. Alternatively, the imaging detector 230 may acquire image information of the object to be imaged only when the first polarization grating 110 and the second polarization grating 120 are moving away from each other, or it may acquire image information of the object to be imaged only when the first polarization grating 110 and the second polarization grating 120 are moving closer to each other. In this way, the polarization state information can be calculated by selecting image information acquired at several consecutive specific positions and the corresponding position information, without selecting repeated specific positions.

[0054] In some embodiments, the polarization state information of the object to be imaged is calculated using the acquired image information and the position information of a specific location, specifically including:

[0055] Three corresponding image intensity information are extracted from image information obtained from three different specific locations. Since the number of specific locations is greater than or equal to three, no duplicate selection will occur when selecting image information obtained from three consecutive specific locations.

[0056] The polarization state information of the object to be imaged is calculated using the extracted image intensity information and the corresponding position information at three specific locations. The position information at each specific location is related to the rotation angle of the polarization direction of the light rays after being modulated by the first polarization grating 110 and the second polarization grating 120.

[0057] In some embodiments, the controller 140 calculates the polarization state information of the object to be imaged multiple times using multiple sets of data information. The position information of three specific locations in different sets of data information may be partially the same or completely different. For example, suppose there are four specific locations within a preset travel range, namely... , , , , , , , This indicates the moving distance of the first polarization grating 110 or the second polarization grating 120, respectively. , , , Image intensity information is obtained at the location , can be used , , The polarization state information is calculated based on the corresponding image intensity information. Then, it can be used... , , The polarization state information is calculated based on the corresponding image intensity information. Then, it can be used... , , The polarization state information is calculated once using the corresponding image intensity information, and so on.

[0058] In some embodiments, when the first polarization grating 110 or the second polarization grating 120 reaches different specific positions, the phase delay of the light emitted from the polarization adjustment component 100 is different; thus, it is possible to adjust the different deflection angles of the incident light.

[0059] Thirdly, embodiments of this application provide a polarization imaging method applied to the polarization imaging device described above, the method comprising the following steps:

[0060] S1. Within a preset travel range, at least three specific positions are determined. When the first polarization grating 110 or the second polarization grating 120 reaches different specific positions, the phase delay of the light emitted from the polarization adjustment component 100 is different.

[0061] S2. Control the first polarization grating 110 or the second polarization grating 120 to reciprocate within a preset stroke range.

[0062] S3, the controller 140 controls the imaging detector 230 to acquire image information once each time the first polarization grating 110 or the second polarization grating 120 reaches a specific position.

[0063] S4, Controller 140 uses the acquired image information and position information at a specific location to calculate the polarization state information of the object to be imaged.

[0064] In some embodiments, step S4 includes:

[0065] Based on the image information acquired by the imaging detector 230 at three different specific locations and the position information of the specific location when the image information was acquired, the controller 140 calculates the polarization state information of the object to be imaged using the following formula:

[0066] (1)

[0067] (2)

[0068] (3)

[0069] in, This represents the relative displacement between the first polarization grating 110 and the second polarization grating 120, i.e., the positional information at a specific location, as described above. The value ranges from , , , Selected from; among them

[0070] This indicates the polarization grating period of the first polarization grating 110 and the second polarization grating 120.

[0071] This indicates the rotation angle of the polarization direction of the light after polarization adjustment by the polarization adjustment component 100.

[0072] This indicates that the first polarization grating 110 and the second polarization grating 120 interact. The image intensity information is obtained from the image at a specific position relative to the displacement, where the polarization direction rotation angle of the outgoing light is at that specific position. ;

[0073] DOP represents the degree of polarization of the object to be imaged, and AOP represents the angle of polarization of the object to be imaged.

[0074] In some embodiments, the preset travel distance ensures that the first polarizing grating never deviates from the effective aperture of the second polarizing grating; preferably, the preset travel distance is equal to half the period of the polarizing grating, and three specific positions are taken within the preset travel distance range. The first polarizing grating 110 or the second polarizing grating 120 has the smallest travel distance within this preset travel distance range, which can improve the movement efficiency of the first polarizing grating 110 or the second polarizing grating 120, thereby improving the efficiency of adjusting the polarization state of the incident light. Example

[0075] Arrange the components according to Figure 2 The structures shown are coaxially mounted, and the polarization grating periods of the first polarization grating 110 and the second polarization grating 120 are... Where the second polarization grating 120 is movable, the controller 140 controls the driving component 130 to translate, thereby driving the second polarization grating 120 to translate, and performing a reciprocating periodic translational motion in the periodic direction of the polarization grating. The relative displacement of the second polarization grating 120 relative to the first polarization grating 110 is... When linearly polarized light is incident, after passing through the first polarization grating 110 and the second polarization grating 120, its left-hand circularly polarized (LCP) component and right-hand circularly polarized (RCP) component acquire different Pancharatnam-Berry (PB) phase delays, causing the outgoing polarization direction to rotate. Angle, the angle of rotation With relative displacement Related, can be expressed as Assuming the polarization direction of the linear polarizer 220 is 0°, the corresponding image intensity information of the image information acquired by the imaging detector 230... , where the incident polarization angle is The linearly polarized light information. During the translational motion of the second polarization grating 120, after passing through half a period of the grating... Internal translational motion, respectively in , , , Image intensity information is obtained at the location Then, Stokes vector polarization demodulation is performed according to the following principle.

[0076] The polarization state of the target reflected light, i.e., the incident light in this embodiment, can be represented by the Stokes vector as follows:

[0077]

[0078] in, Related to left-hand and right-hand circularly polarized light, since the circular polarization component of a target in nature is very small and can be ignored, it is usually assumed that... The Stokes vector of the emitted light from the second polarization grating 120 in this embodiment of the application. It can be obtained by left-multiplying the Mueller matrices of polarizing devices 2 and 3 by the Stokes vector of the incident light, that is:

[0079]

[0080] The expression for the emitted light intensity is obtained as follows:

[0081]

[0082] As shown in the above formula, Take 3 values, that is, in 3 relative displacements At this location, obtain intensity image information. The solution can then be obtained. This allows for the demodulation of polarization degree (DOP) imaging and polarization angle (AOP) imaging information:

[0083]

[0084]

[0085] The high-speed demodulation polarization imaging process is as follows: control the second polarization grating 120 during the grating half-cycle. Internal translational motion, at specific positions , , , Image intensity information is obtained at the location , The 130th movement of the drive component cycle.

[0086] First, during the 130 motion cycle of the drive component. Inside, get , , The image intensity information at that location is obtained by first-stage polarization information demodulation. and ;

[0087] Exercise to The location, together with the two previous specific locations, includes , , The second polarization information demodulation is performed to obtain and ;

[0088] Exercise to The location, together with the two previous specific locations, includes , , The third polarization information demodulation is obtained and ;

[0089] In sequence, move to , Compared with the previous two specific location information, make the first Demodulation of secondary polarization information yields and .

[0090] In summary, this application presents a novel time-division polarization imaging device and method, particularly a high-speed polarization imaging device and method based on polarization grating modulation, especially under the condition of using a high frame rate camera, where the polarization demodulation imaging frame rate of the polarization imaging device is related to the motion frequency of the driving component 130. Regarding the limit, it can reach 4 Limited only by the camera's frame rate and sensitivity, it can basically reach the same frame rate level as light intensity imaging, solving the traditional shortcomings of existing time-division polarization imaging methods, and has the advantages of high speed, practicality, and accuracy.

Claims

1. A polarization adjustment component, wherein the polarization adjustment component is used to adjust the polarization direction of incident light, characterized in that: The polarization adjustment assembly comprises a first polarization grating and a second polarization grating, The first polarization grating and the second polarization grating have the same one-dimensional subwavelength period structure on their surfaces, and the grating period directions of the first polarization grating and the second polarization grating are the same, The first polarization grating and the second polarization grating can be relatively displaced in the grating period direction, The polarization adjustment assembly further comprises a driving assembly and a controller, The driving assembly is used to drive the first polarization grating or the second polarization grating to move so as to relatively displace the first polarization grating and the second polarization grating in the grating period direction, The controller is used to control the driving assembly to drive the first polarization grating or the second polarization grating to reciprocate within a preset stroke range.

2. The polarization conditioning assembly of claim 1, wherein: The preset stroke satisfies that the first polarization grating is always within the effective light passing aperture of the second polarization grating.

3. The polarization conditioning assembly of claim 2, wherein: The preset stroke is equal to one-half of the polarization grating period.

4. A polarimetric imaging apparatus, characterized by: From the object side to the image side, sequentially comprise An imaging lens group, located in front of the focal plane of the imaging detector, used to focus light on the focal plane of the imaging detector, The polarization adjustment assembly of claim 1 or 2, used to adjust the polarization direction of light emitted from the imaging lens group, A linear polarizer, used to polarize and filter light emitted from the polarization adjustment assembly, An imaging detector, used to acquire image information of the object to be imaged, The controller is further used to control the imaging detector to acquire image information when the first polarization grating or the second polarization grating moves to at least three specific positions within the preset stroke range, and calculate the polarization state information of the object to be imaged by using the acquired image information and the position information of the specific positions.

5. The polarimetric imaging apparatus of claim 4, wherein: The controller controls the imaging detector to acquire image information once every time the first polarization grating or the second polarization grating reaches a specific position.

6. The polarimetric imaging apparatus of claim 5, wherein: The calculation of the polarization state information of the object to be imaged by using the acquired image information and the position information of the specific positions comprises Extracting three corresponding image intensity information from the image information acquired at the three different specific positions, Calculating the polarization state information of the object to be imaged by using the extracted image intensity information and the position information of the corresponding three specific positions.

7. The polarimetric imaging apparatus of claim 6, wherein: The controller calculates the polarization state information of the object to be imaged by using multiple sets of data information multiple times, and the position information of the three specific positions in different sets of data information is partially the same or completely different.

8. The polarimetric imaging apparatus of claim 4, wherein: The phase delay of light emitted from the polarization adjustment assembly is different when the first polarization grating or the second polarization grating reaches different specific positions.

9. A polarization imaging method applied to the polarization imaging device according to any one of claims 4 to 7, characterized in that: Comprise Determining at least three specific positions within the preset stroke range, Controlling the first polarization grating or the second polarization grating to reciprocate within the preset stroke range, The controller controls the imaging detector to acquire image information once every time the first polarization grating or the second polarization grating reaches a specific position, The controller calculates the polarization state information of the object to be imaged by using the acquired image information and the position information of the specific positions, The phase delay of light emitted from the polarization adjustment assembly is different when the first polarization grating or the second polarization grating reaches different specific positions.

10. The polarization imaging method of claim 9, wherein: The controller calculates the polarization state information of the object to be imaged by using the acquired image information and the position information of the specific positions, including The controller calculates the polarization state information of the object to be imaged according to the image information acquired by the imaging detector at three different specific positions and the position information of the specific positions when the image information is acquired, by the following formula: （1） （2） （3） wherein represents the relative displacement between the first polarization grating and the second polarization grating, i.e. the position information of a specific position, denotes the period of the polarization gratings of the first polarization grating and the second polarization grating, denotes the angle of rotation of the polarization direction of the light rays after the polarization adjustment effect of the polarization adjustment assembly, represents image intensity information of image information acquired at a specific position at which relative displacement of the first polarization grating and the second polarization grating occurs represents image intensity information of image information acquired at a specific position at which relative displacement of the first polarization grating and the second polarization grating occurs DOP represents the degree of polarization of the object to be imaged, and AOP represents the polarization angle of the object to be imaged.

11. The polarization imaging method of claim 9, wherein: The preset stroke satisfies that the first polarization grating is always not deviated from the effective light aperture of the second polarization grating.

12. The polarization imaging method of claim 11, wherein: The preset stroke is equal to one half of the period of the polarization grating, and three specific positions are taken within the preset stroke range.

Images