Swing polarizer type polarization imaging measuring device and method

A polarization imaging and measurement device technology, which is applied to measurement devices, polarization spectroscopy, optical device exploration, etc., can solve problems such as insufficient polarization detection, and achieve the effects of improving sampling speed, simple operation, and solving fast measurement problems.

Active Publication Date: 2019-11-12
BEIJING INST OF ENVIRONMENTAL FEATURES
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AI-Extracted Technical Summary

Problems solved by technology

At present, this rotating polarizer-type time-sharing polarization imaging detection method is restricted by factors such as motor rotation speed, high-precision positioning, and polarization ima...
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Abstract

The invention relates to the technical field of polarization imaging, in particular to a swing polarizer type polarization imaging measuring device and method. The device comprises a lens module, a polarization module, a detection module and a control module, wherein the polarization module comprises a rotating shaft and a balance wheel arranged on the rotating shaft; the balance wheel is providedwith at least three polarizers with different polarization directions, the polarizers are arranged adjacently along the circumferential direction of the rotating shaft, the balance wheel is positioned between the detection module and the lens module, and each polarizer can rotate to a measuring position along with the rotating shaft respectively; the control module is electrically connected withthe polarization module and the detection module, and is used for generating a swing control command and sending the swing control command to the polarization module so as to control the rotation modeof the rotating shaft and realize reciprocating swing of the balance wheel, generating a collection control command and sending the collection control command to the detection module so as to realizethe measurement of radiation intensity images in different polarization directions in target scenes. Collection for polarization images is quick, the frame rate of output polarization is high, and the device is applicable for high-precision rapid measurement for polarization information in moving target scenes.

Application Domain

Polarisation-affecting propertiesPolarisation spectroscopy +2

Technology Topic

PhysicsPolarizer +8

Image

  • Swing polarizer type polarization imaging measuring device and method
  • Swing polarizer type polarization imaging measuring device and method
  • Swing polarizer type polarization imaging measuring device and method

Examples

  • Experimental program(3)

Example Embodiment

[0033] Example one
[0034] Such as figure 1 As shown, a swing polarizer-type polarization imaging measurement device provided by an embodiment of the present invention includes a lens module 1, a polarization module 2, a detection module 3, and a control module ( figure 1 Not shown in). The lens module 1 includes an optical lens for imaging a target scene, and the detection module 3 includes a detector for receiving light emitted by the optical lens, and the central axis of the detector coincides with the central axis of the optical lens to receive light. Preferably, the lens module 1 further includes a lens fixing seat for setting an optical lens, and the detection module 3 further includes a detector fixing seat for setting a detector. An adjustable lens is preferably provided between the lens fixing seat and the detector fixing seat. Slide rail, used to locate the relative position of the detector and the optical lens.
[0035] Such as figure 1 with figure 2 As shown, the polarization module 2 includes a rotation axis and a balance wheel 22 arranged on the rotation axis. The balance wheel 22 is relatively fixed to the rotation axis and can rotate with the rotation axis. The rotating shaft is located on one side of the optical lens, and its central axis is parallel and spaced apart from the central axis of the optical lens. The balance wheel 22 is provided with at least three polarizers 23 with different polarization directions. The function of the balance wheel 22 is to install the polarizers 23 with different polarization directions. Wherein, the polarization direction here refers to the relative angle direction between the transmission axis of the polarizer 23 itself and the perpendicular from the center of the polarizer 23 to the central axis of the rotation axis.
[0036] Each polarizer 23 is arranged adjacently along the circumferential direction of the rotation axis, that is, each polarizer 23 is located at an equal distance from the central axis of the rotation axis, and is arranged around the central axis. The distance between any two adjacent polarizers 23 ( On the premise of not interfering with each other and being fixed and stable) as small as possible. The balance wheel 22 is located between the detector and the optical lens. Each polarizer 23 can follow the axis of rotation to the measurement position. The central axis of the polarizer 23 at the measurement position coincides with the central axis of the detector and the optical lens, and at this moment the polarizer 23 is at the entrance pupil of the detector. , The optical lens is at the entrance pupil of the clear aperture of the polarizer 23.
[0037] Preferably, the effective clear aperture of each polarizer 23 is larger than the size of the total image unit of the detector. Further, the geometric dimensions of the polarizing plates 23 are the same. The balance wheel 22 can adopt a polarizer frame structure (such as image 3 As shown), the polarizer 23 is clamped and fixed by a pressing ring to prevent it from slipping off. After the fixed installation is completed, the effective clear aperture of the polarizer 23 has a small difference from its effective diameter. The balance wheel 22 can also adopt a plate-shaped, fan-shaped or wheel-shaped structure, and can carry each polarizer 23, which is not further limited here, but the polarizer 23 should be concentrated on one side of the axis of rotation (that is, each polarizer 23 should be located as much as possible Compact layout), so that the balance wheel 22 shortens the reciprocating swing path, realizes the rapid switching of different polarization directions, and improves the imaging measurement efficiency.
[0038] Preferably, the rotation axis is set horizontally, the vertical line from the center of the polarizer 23 at the measurement position to the center axis of the rotation axis is horizontal, and the polarization direction can be considered as the angle between the light transmission axis of the polarizer 23 and the horizontal direction.
[0039] The control module is electrically connected to the polarization module 2 and the detection module 3, and is used to generate a swing control command and send it to the polarization module 2 to control the rotation of the rotation axis to realize the periodic reciprocating swing of the balance wheel 22, which means that each polarizer 23 is The optical lens and the detector move back and forth to switch different polarization directions, and the way of reciprocating swing is preferably uniform swing. The control module is also used to generate acquisition control instructions and send them to the detection module 3 to control the exposure of the detectors, so as to measure the radiation intensity images of the target scene under different polarization directions.
[0040] Further, the detection module 3 also includes an image processor, which is used to resolve each group of radiation intensity images corresponding to different polarization directions swinging from one side of the balance wheel 22 to the other side to obtain a polarization image. The polarization image includes a polarization degree image and a polarization angle image.
[0041] When the swing polarizer type polarization imaging measurement device provided by the present invention is used, the image information of the target scene is transmitted to the polarization module 2 through the optical lens. The image of the lens passes through the polarizer 23 and then enters the detector, and the detector obtains the radiation intensity image in the polarization direction of the polarizer 23. With the balance wheel 22 periodically swinging back and forth, the radiation intensity images of the target scene under different polarization angles can be measured, and then the Stokes vector characterizing the target polarization state can be obtained by calculation, and then the polarization degree image and polarization angle of the target scene can be obtained Image, realizing time-sharing polarization imaging measurement. The device provided by the present invention realizes switching of different polarization directions by only swinging, and can traverse the polarizer 23 of different polarization directions from one side of the balance wheel 22 to the other side, and has a high frame rate polarization image output, which improves the time sharing The sampling speed of the polarization imaging system solves the problem of rapid measurement of polarization imaging of moving target scenes.
[0042] Preferably, the polarization module 2 further includes a servo motor 21 and an encoder 24. Such as figure 2 As shown, the output shaft of the servo motor 21 is connected to the rotating shaft, and is used to drive the rotating shaft to rotate according to the swing control command of the control module, so as to realize the periodic reciprocating swing of the balance wheel 22. The encoder 24 is connected with the rotating shaft, and is used to measure the swing angle information of the balance wheel 22, that is, obtain the current posture information of the balance wheel 22, and feed back the measured angle information to the control module.
[0043] Further, the control module is used for generating swing control instructions and collecting control instructions according to the received angle information. The control module determines the current posture of the balance wheel 22 according to the angle information fed back by the encoder 24, and determines whether to generate and send corresponding swing control instructions and acquisition control instructions according to the current posture of the balance wheel 22.
[0044] Specifically, the detector can be a CCD detector, and the encoder 24 can be an absolute photoelectric encoder, preferably connected to the rotating shaft through a flexible coupling, such as figure 2 As shown, the absolute photoelectric encoder is preferably arranged on the side of the rotating shaft away from the servo motor 21, so as to accurately measure the rotation angle information actually generated by the balance wheel 22 when driven.
[0045] In some preferred embodiments, the balance wheel 22 is provided with three or four polarizers 23. When the device uses three or four polarizers 23, the balance wheel 22 has a small volume and a short swing path, making it easier to achieve rapid swing, so as to increase the output polarization frame rate.
[0046] Further, when the balance wheel 22 is provided with three polarizers 23, the polarization directions of the three polarizers 23 preferably correspond to 0°, 60°, and 120° respectively, such as image 3 As shown, in order to facilitate the distinction, the three polarizers are labeled A, B, and C respectively. The reference coordinate axis 222 of each polarizer is located at the vertical line from the center of the polarizer to the rotation axis, and the polarization direction of the polarizer labeled A is 60°, the angle between its own transmission axis 221 and the reference coordinate axis 222 is 60°, the polarization direction of the polarizer labeled C is 120°, and the angle between its own transmission axis 221 and the reference coordinate axis 222 is 120°, In the same way, the polarization direction of the polarizer labeled B is 0°, and its own light transmission axis 221 is arranged along the vertical line from the center to the rotation axis, and coincides with its own reference coordinate axis 222. It should be noted that the specific polarization directions of the three polarizers 23 can be exchanged as required, and there is no need to completely follow image 3 Shown.
[0047] Preferably, when the balance wheel 22 is provided with four polarizers 23, the polarization directions of the four polarizers 23 correspond to 0°, 45°, 90°, and 135°, respectively, which is beneficial to resolve the polarization image.

Example Embodiment

[0048] Example two
[0049] With regard to the above-mentioned swinging polarizer type polarization imaging measurement device, the present invention also provides a swinging polarizer type polarization imaging measurement method, which uses the swinging polarizer type polarization imaging measurement device as described in any one of the above to perform polarization imaging measurement. Including the following steps:
[0050] S1. Deploy and calibrate a swing polarizer-type polarization imaging measurement device on one side of the target scene.
[0051] Among them, the calibration includes adjusting the relative positions of the lens module 1, the polarization module 2, and the detection module 3 so that the central axis of the detector coincides with the central axis of the optical lens, and any polarizer 23 can be rotated to make its own central axis and the detection When the central axes of the polarizer and the optical lens coincide, and the central axes of the polarizer 23, the detector and the optical lens coincide, the polarizer 23 is located at the entrance pupil of the detector, and the optical lens is located on the polarizer 23. The entrance pupil of the clear aperture.
[0052] S2. Let the balance wheel 22 drive each polarizer 23 to periodically reciprocate to achieve switching of different polarization directions. The reciprocating manner is preferably to oscillate at a uniform speed. When the polarizer 23 is present at the measurement position, the detector is exposed to light, and the radiation intensity image of the target scene in the polarization direction corresponding to the current polarizer 23 is collected.
[0053] Such as Figure 4 As shown, in one swing cycle, the way in which the balance wheel 22 drives the polarizer 23 to swing is: (B→C→B→A) 1 →(B→C→B→A) 2 →...→(B→C→B→A) n , Where A, B, C respectively represent image 3 The three polarizers labeled A, B, and C, or their corresponding radiation intensity images, n represents the number of cycles of reciprocating oscillation, and the size of n is determined according to the requirements of each measurement.
[0054] Further, in step S2, the balance wheel 22 is made to drive each polarizer 23 to periodically reciprocate, and when switching between different polarization directions is realized, the control module generates a swing control instruction and sends it to the polarization module 2, so that the balance wheel 22 periodically reciprocates The regular movement of the swing moves the next polarizer 23 to the measurement position. The next polarizer 23 here is the polarizer 23 that should be moved to the measurement position next according to the regular reciprocating swing. When the movement of the corresponding polarizer 23 is completed, there is a polarizer 23 at the measurement position, and the control module generates a collection control command and sends it to the detection module 3 to expose the detector and collect the radiation intensity image.
[0055] After the acquisition is completed, the control module continues to generate a swing control instruction and send it to the polarization module 2, repeating the above process, namely swing, collection, swing, acquisition, and so on, until the end of the entire measurement process.
[0056] Preferably, if the polarization module 2 further includes a servo motor 21 and an encoder 24, in step S2, the control module first determines the current posture of the balance wheel 22 according to the received angle information before generating the swing control instruction and sending it to the polarization module 2, Furthermore, the position of the next polarizer 23 and the movement mode of the balance wheel 22 are determined. Before the control module generates the acquisition control command and sends it to the detection module 3, it first judges the current posture of the balance wheel 22 according to the received angle information, and then determines whether the current polarizer 23 is at the measurement position. If the current polarizer 23 is at the measurement position, that is There is a polarizer at the measurement position, and then generate and send the acquisition control command.
[0057] S3. Calculate the Stokes vector representing the polarization state of the target according to the radiation intensity images in the respective polarization directions corresponding to the swing of the balance wheel 22 from one side to the other, and calculate the Stokes vector representing the polarization state of the target according to the relationship between the Stokes vector and the degree of polarization and the polarization angle The relationship between the polarization degree image and the polarization angle image of the target scene is obtained, and the polarization imaging measurement is realized.
[0058] The balance wheel 22 swings from one side to the other, and the polarizers 23 with different polarization directions pass through the measurement position, and a corresponding set of radiation intensity images in each different polarization direction can be obtained, through such a set of radiation intensity images. Solve the polarization image. Such as Figure 4 As shown, taking the balance wheel 22 provided with three polarizers 23 as an example, from one side to the other, whether it is C→B→A in a swing cycle or A→B→C across the cycle, it can be solved. Calculate the output of one frame of polarization image and swing back and forth for n cycles to obtain 2n-1 frames of polarization image with high imaging rate.
[0059] Preferably, in step S3, the Stokes vector representing the polarization state of the target is calculated according to the radiation intensity images (ie a set of radiation intensity images) corresponding to the polarization directions when the balance wheel 22 swings from one side to the other side. , Adopt the sorting iterative method, according to the periodic reciprocating swing, update the stored data in the order of collecting the radiation intensity images, and calculate the Stokes vector in an iterative way, that is, continuously replace the current storage with the newly collected radiation intensity image data Data, this method can reduce the amount of data storage, and further improve the polarization imaging rate. When calculating each group of radiation intensity images, the radiation intensity image data corresponding to the polarizing plates 23 at the edges of both sides (such as Figure 4 A and C) are reused when solving the Stokes vector that characterizes the target polarization state, which also helps to increase the imaging rate.
[0060] Preferably, when the balance wheel 22 is provided with three polarizers 23 with different polarization directions, different polarization channels are selected by driving the servo motor 21 to quickly swing the balance wheel 22 to measure the target scene in different polarization directions (0°, 60° and 120°). °) radiation intensity image. In step S3, when calculating the Stokes vector representing the polarization state of the target, the Stokes vector: S=[I,Q,U] T , The expression is:
[0061]
[0062] Among them, I'(θ) (θ=0°, 60°, 120°) represents the radiation intensity image data collected by the detector in the polarization direction θ, and θ represents the angle value corresponding to the polarization direction.
[0063] According to the relationship between the Stokes vector and the degree of polarization (DoP) and the angle of polarization (AoP) to obtain the polarization degree image and the polarization angle image of the target scene, the expression of the degree of polarization (DoP) and the angle of polarization (AoP) is :
[0064]
[0065]
[0066] According to the above formulas (2) and (3), the polarization degree image and the polarization angle image of the target scene can be obtained by solving.

Example Embodiment

[0067] Example three
[0068] Such as Figure 1 to Figure 4 As shown, the third embodiment is basically the same as the first embodiment, and the similarities will not be repeated here. The differences are:
[0069] The swing polarizer type polarization imaging measurement device uses three quartz wire grid polarizers with the same specifications, the effective diameter is 25.4mm, the effective wavelength range is visible to shortwave infrared, that is, 350~2500nm, the transmittance is greater than 80%, and the extinction The ratio is 1000:1. After the quartz wire grid polarizer is clamped on the balance wheel by the pressure ring, the difference between the effective clear aperture and the effective diameter of the polarizer is no more than 4mm. The minimum value of the number of cycles n of reciprocating oscillation is 25. CCD detectors are used to collect radiation intensity images.
[0070] During operation, the polarization module and the detection module keep working synchronously. After each polarizer is rotated in place, the control module quickly transmits a TTL pulse signal to the CCD detector to start collecting radiation intensity images at a speed of 5ms. After the image acquisition is completed, The balance wheel rotates to the next position, and so on, you can quickly collect the radiation intensity images of different polarization directions of the target, and use the 3 times 1 Stokes vector to represent the polarization state of each pixel, and then combine the formula (1 ), (2) and (3), using such as Figure 4 The sorting iterative method shown is to process the collected images, solve the three adjacent radiation intensity image data, and obtain the polarization image of the target. The acquisition frame rate of the CCD detector is 100 frames/sec. The device can output the polarization image of the target scene at a rate of 49 polarization frames/sec. The data volume is large and the economy is better. It can measure traditional time-sharing polarization imaging. The output speed of the polarization image is increased by more than 6 times, and the structure of the device is more concise, portable, convenient and fast adjustment, and suitable for the polarization detection requirements of most moving targets.
[0071] In summary, the present invention provides a time-sharing polarization imaging device and method capable of realizing rapid polarization measurement, which can be applied to polarization information measurement of moving target scenes, and is a meaningful breakthrough in the field of polarization imaging measurement.

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