CN111964782A

CN111964782A - Method for detecting specific polarization angle of polaroid by space modulation polarization imaging

Info

Publication number: CN111964782A
Application number: CN202010824785.XA
Authority: CN
Inventors: 叶松; 张紫杨; 朱保华; 李树; 张文涛; 王方原; 汪杰君; 王新强; 陈妮艳
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2020-08-17
Filing date: 2020-08-17
Publication date: 2020-11-20
Anticipated expiration: 2040-08-17
Also published as: CN111964782B

Abstract

The invention provides a method for detecting a specific polarization angle of a polaroid by space modulation polarization imaging. The process comprises the following steps: a1, carrying out spatial modulation polarization imaging on incident light with the central wavelength of lambda to obtain an interference image containing polarization information; a2, transforming the interference image to find the position of Stokes vector modulation of the incident light with narrow bandwidth of central wavelength lambda in the frequency domain; a3, determining the number and position of Stokes vectors by analyzing and judging whether the signals on the modulated positions are interference; and A4, judging whether the polarization angle of the polarizer is correct by combining the polarization angle of the polarizer and the presence or absence of the Stokes vector in the frequency domain, and finally adjusting the polarizer to the correct polarization angle. The invention can be used for detecting and adjusting the polarization angle of the polaroid and can be widely applied to the fields of polarization imaging and the like.

Description

Method for detecting specific polarization angle of polaroid by space modulation polarization imaging

(I) technical field

The invention relates to a method for detecting a specific polarization angle of a polarizing film by space modulation polarization imaging, which can be used for detecting and adjusting the polarization angle of the polarizing film and belongs to the technical field of polarization imaging.

(II) background of the invention

Polarization represents the transverse wave characteristic of a light wave, and the light wave can be divided into polarized light and unpolarized light according to the polarization state of the light wave. The polarization state of the light wave can be changed through reflection and refraction, and the polarization is used for representing the physical basic properties of an object. The inherent polarization characteristics of light waves change with the physical properties of matter during their transmission, but they cannot be observed. With the rapid development of the polarization image detection technology, the polarization imaging detection becomes a very meaningful study in emerging directions of polarization information visualization, measurement information dimension expansion, simultaneous detection and the like. The polarization imaging can be roughly divided into a time-sharing type and a snapshot type, wherein the time-sharing type is a method for obtaining a specific polarization image by mechanically rotating a polarizing film to a specific angle or using an electric control liquid crystal for regulation and control, and has the advantages of high spatial resolution, simple subsequent operation and the like. The snapshot type is a method which can obtain all polarization information through correlation calculation by one-time imaging, has good real-time performance and practicability, and the imaging target is also expanded to a dynamic object.

Spatially modulated polarization imaging is advantageous in that it does not degrade the spatial resolution of the imaging nor does it require registration between images to obtain all of the polarization information of the target. The spatial modulation polarization imaging is to obtain several coherent light beams by utilizing the light splitting characteristic of the birefringent crystal, and obtain an interference pattern containing polarization information. After the birefringent wedge prism is applied to polarization imaging, which is proposed by Oka in 2003, the spatial modulation full-polarization imaging technology is used for boarding a stage of polarization imaging, and then Oka and Saito improve the technology and use a Savart plate to replace the birefringent wedge prism, so that the assembly process is simpler and more convenient. In 2008, Haitao Luo developed a principle prototype of Savart-based snapshot imaging SIP, and performed polarization imaging experiments on automobiles and buildings. In 2012, Cao improved the performance of spatial polarization imaging by changing the direction between the optical axes of the single plates in the Savart plate.

The polarizing plate is needed in a specific scene or in some experimental tests, and the error of the polarization angle of the polarizing plate affects the measurement result and causes certain interference to the experimental tests, so the polarization angle of the polarizing plate needs to be measured and adjusted.

The invention discloses a method for detecting a specific polarization angle of a polaroid by space modulation polarization imaging, which comprises the steps of obtaining a corresponding interference pattern by the space modulation polarization imaging, converting the interference pattern, and analyzing the polarization angle of a polaroid theory and the distribution condition of polarization components in a frequency domain to judge whether the special angle of the polaroid is accurate and adjust.

Disclosure of the invention

The invention aims to provide a method for detecting a specific polarization angle of a polaroid by space modulation polarization imaging, which has simple theory and easy operation.

The purpose of the invention is realized by the following technical means:

a method for spatially modulated polarization imaging for polarizer specific polarization angle detection, comprising:

a1, carrying out spatial modulation polarization imaging on incident light with the central wavelength of lambda to obtain an interference image containing polarization information;

a2, transforming the interference image to find the position of Stokes vector modulation of the incident light with narrow bandwidth of central wavelength lambda in the frequency domain;

a3, determining the number and position of Stokes vectors by analyzing and judging whether the signals on the modulated positions are interference;

and A4, judging whether the polarization angle of the polarizer is correct by combining the polarization angle of the polarizer and the presence or absence of the Stokes vector in the frequency domain, and finally adjusting the polarizer to the correct polarization angle.

Further, the incident light in step a1 is subjected to spatially modulated polarization imaging, and the result of the polarization imaging system is shown in fig. 1, where 1 is a polarizer, 2 is a polarizer set, and 3 is an imaging camera. After entering the polarization imaging system, the incident light is divided into four coherent light beams, and then an interference image containing all polarization information of the target is obtained in the imaging camera.

Further, the step a4 judges whether the polarization angle of the polarizer is correct by combining the polarization angle of the polarizer and whether the Stokes vector exists in the frequency domain, wherein the distribution of the Stokes vector in the frequency domain is shown in fig. 2, fig. 2(a) is a distribution diagram in the frequency domain when the polarization angle is 0 ° or 90 °, fig. 2(b) is a distribution diagram in the frequency domain when the polarization angle is 45 °, and fig. 2(c) is a distribution diagram in the frequency domain when the specific polarization angle is deviated.

The invention has the beneficial effects that: compared with the prior method, the method for detecting the specific polarization angle of the polaroid by the spatial modulation polarization imaging is more visual and concrete, has simpler and clearer theory and better adjustment effect on the polarization angle of the polaroid by analyzing the distribution condition of the polarization components in the frequency domain.

(IV) description of the drawings

FIG. 1 is composed of a polarizer 1, a polarizer 2 and an imaging camera 3. After incident light passes through a polarizing film 1 and a polarizing lens 2, the light is divided into four coherent light beams, and finally an interference image is formed in an imaging camera 3 to obtain an interference image with a specific polarization angle.

Fig. 2 is a distribution diagram of Stokes vectors in different cases in a frequency domain, fig. 2(a) is a distribution diagram in the frequency domain at a polarization angle of 0 ° or 90 °, fig. 2(b) is a distribution diagram in the frequency domain at a polarization angle of 45 °, and fig. 2(c) is a distribution diagram in the frequency domain at a deviation of a specific polarization angle.

FIG. 3 is a flow chart of a method for polarizer specific polarization angle detection based on spatially modulated polarization imaging.

(V) detailed description of the preferred embodiments

The invention is further illustrated below with reference to specific examples.

As shown in fig. 3, a method for detecting a specific polarization angle of a polarizer by spatially modulated polarization imaging according to the present invention comprises:

Specifically, in the step a4, it is determined whether the polarization angle of the polarizer is correct by combining the polarization angle of the polarizer and whether the Stokes vector exists in the frequency domain, and taking the polarization angle of 0 ° as an example, when the distribution of the Stokes vector in the frequency domain is shown in fig. 2(a), it indicates that the polarization angle of the polarizer is correct at this time and is not to be adjusted, and when the distribution of the Stokes vector in the frequency domain is shown in fig. 2(c), it indicates that the polarization angle of the polarizer has a certain deviation, and it is necessary to adjust the polarizer so that the distribution of the Stokes vector in the frequency domain is shown in fig. 2(a), and the polarization angle adjustment of the polarizer is completed.

Although the present invention has been described in detail with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims. The techniques, shapes, and structural parts not described in detail in the present invention are all known techniques.

Claims

1. A method for detecting the specific polarization angle of a polaroid by space modulation polarization imaging. The method is characterized by comprising the following specific steps of:

2. The method of claim 1, wherein the method comprises the steps of: by comparing the values of the Stokes vector positions with those of the other Stokes vector positions in determining whether the signal at the modulated position is an interference, it is indicated as an interference when it is too small.

3. The method of claim 1 for polarization angle-specific detection of polarizers by spatially modulated polarization imaging. The method is characterized in that: in judging whether the polarization angle of the polarizing plate is correct, only a specific Stokes vector appears at a specific polarization angle in a frequency domain, thereby adjusting the polarization angle of the polarizing plate.