CN111539411A - Method for identifying objects of different materials by using polarization information - Google Patents

Method for identifying objects of different materials by using polarization information Download PDF

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CN111539411A
CN111539411A CN202010311100.1A CN202010311100A CN111539411A CN 111539411 A CN111539411 A CN 111539411A CN 202010311100 A CN202010311100 A CN 202010311100A CN 111539411 A CN111539411 A CN 111539411A
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polarization
refractive index
mathematical model
approximate
objects
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谭治英
赵宝来
徐孝彬
费仲文
骆敏舟
沙刘力
庞凤麟
赵鸣晖
王子龙
张瀛
高岩
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Changzhou Campus of Hohai University
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Abstract

The invention discloses a method for identifying objects of different materials by utilizing polarization information, which comprises the following steps: the industrial personal computer controls the light source to be lightened and triggers the polarization camera to acquire and process images; the polarization camera collects polarization images of an object in four directions of 0 degree, 45 degrees, 90 degrees and 135 degrees to obtain polarization intensities I in the four directions0，I45，I90And I135Then calculating the Stokes parameter S0、S1、S2(ii) a Calculating the polarization intensity I, the direction angle phi and the polarization degree rho by utilizing the Stokes parameters; deducing a mathematical model of the refractive index n based on the relation between the polarization degree rho and the refractive index n and the zenith angle theta, wherein the zenith angle theta is approximate to the azimuth angle phi, and the azimuth angle phi is substituted into the mathematical model of the refractive index n to obtain the approximate refractive index
Figure DDA0002457871540000011
A mathematical model; using clustering algorithm to approximate refractive index
Figure DDA0002457871540000012
And clustering the data to realize the identification of objects with different materials. The method has the advantages of high calculation precision, low cost and easy popularization.

Description

Method for identifying objects of different materials by using polarization information
Technical Field
The invention relates to a machine vision material identification method, in particular to a method for identifying objects of different materials by utilizing polarization information.
Background
With the application and development of machine vision technology, robots or automation equipment have stronger and stronger ability to perform identification by means of vision. However, the conventional visual recognition method relies on a color camera or a black and white camera to acquire an RGB color image or a grayscale image, and recognition of an object is limited to information such as color, texture, intensity and direction of reflected light on the surface of the object, and lacks information expression of material of the object. Although the spectral camera can be used for collecting multiband information of an object and identifying materials, the requirement on the illumination environment is strict and the price is high, so that the spectral camera is not widely applied to robots or automatic equipment.
Disclosure of Invention
The purpose is as follows: in order to overcome the defects in the prior art, the invention provides a method for identifying objects made of different materials by using polarization information, and solves the problems of difficulty in identifying the materials and high cost on the existing robot or automation equipment.
The technical scheme is as follows: in order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method for recognizing objects made of different materials by utilizing polarization information is disclosed, the used device comprises a polarization camera, an industrial lens, a light source and an industrial personal computer, and the method comprises the following steps:
the industrial personal computer controls the light source to be lightened and triggers the polarization camera to acquire and process images;
the polarization camera collects polarization images of an object in four directions of 0 degree, 45 degrees, 90 degrees and 135 degrees to obtain polarization intensities I in the four directions0，I45，I90And I135By means of I0，I45，I90And I135Calculating the Stokes parameter S0、S1、S2；
Calculating the polarization intensity I, the direction angle phi and the polarization degree rho by utilizing the Stokes parameters;
deducing a mathematical model of the refractive index n based on the relation between the polarization degree rho and the refractive index n and the zenith angle theta, wherein the zenith angle theta is approximate to the azimuth angle phi, and substituting the azimuth angle phi into the mathematical model of the refractive index n instead of the zenith angle theta to obtain the approximate refractive index
Figure BDA0002457871520000011
A mathematical model;
using clustering algorithm to approximate refractive index
Figure BDA0002457871520000012
And clustering the data to realize the identification of objects with different materials.
Further, the Stokes parameter S0、S1、S2The calculation process of (2) is as follows:
Figure BDA0002457871520000013
S1＝I0-I90，
S2＝I45-I135，
wherein S is0Represents the total intensity of light, S1Represents the difference between linearly polarized light components of 0 DEG and 90 DEG, S2Representing the difference between the 45 deg. and 135 deg. linearly polarized light components.
Further, the calculation process of the polarized light intensity I, the direction angle Φ and the polarization degree ρ is as follows:
I＝S0，
Figure BDA0002457871520000021
Figure BDA0002457871520000022
further, the relation between the polarization degree rho and the refractive index n and the zenith angle theta is as follows:
Figure BDA0002457871520000023
further, the mathematical model of the refractive index n is:
Figure BDA0002457871520000024
wherein the content of the first and second substances,
A＝ρ2cos4θ
B＝2ρ2cos2θ(2sin4θ-sin2θ)-4sin4θcos2θ
C＝ρ2(2sin4θ-sin2θ)2+4sin6θcos2θ。
further, the approximate refractive index
Figure BDA0002457871520000025
The mathematical model is as follows:
Figure BDA0002457871520000026
wherein the content of the first and second substances,
A′＝ρ2cos4φ
B′＝2ρ2cos2φ(2sin4φ-sin2φ)-4sin4φcos2φ
C′＝ρ2(2sin4φ-sin2φ)2+4sin6φcos2φ。
has the advantages that: compared with the existing machine vision identification method, the method for identifying the objects made of different materials by utilizing the polarization information disclosed by the invention has the following advantages:
the invention provides an object surface approximate refractive index calculated by utilizing a polarization image, and clustering the approximate refractive index data by utilizing a clustering algorithm to provide information for visual identification of objects, so that the objects of different materials can be identified; the approximate refractive index depends on strict mathematical theory derivation, and has the advantages of high calculation precision and high speed; compared with the existing spectral object material identification method, the method for identifying the object by using the polarization information has the characteristics of simplicity, low cost, easiness in popularization and the like, and can effectively meet the requirements of robots or automation equipment.
Drawings
FIG. 1 is a schematic diagram of the calculation process of the approximate refractive index of the identification method of the present invention;
FIG. 2 is a gray scale image normalized for polarization intensity for four comparative examples of the present invention;
FIG. 3 is a gray scale image normalized in azimuth for four comparative embodiments of the present invention;
FIG. 4 is a gray scale image normalized for polarization for four comparative examples of the present invention;
FIG. 5 is a bar graph of the approximate indices of refraction for four comparative examples of the present invention;
FIG. 6 is a graph of approximate refractive index clustering results for four comparative examples of the present invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
The invention provides a method for identifying material by using polarization information of an object surface, the calculation flow of the method is shown in figure 1, and the device used by the method comprises a polarization camera, a lens, a light source and an industrial personal computer. Four groups of objects made of different materials are selected for a comparison test, wherein the background material is metal, (a) the group is a metal block and a wood block, the metal block and the background material are the same, (b) the group is the wood block and a ceramic cup, (c) the group is a red plastic block and a green plastic shell, and (d) the group is the red plastic block and red paper.
After the device is started, the industrial personal computer controls the light source to be lightened, the polarization camera is triggered to collect polarization images of each group of objects in four directions of 0 degree, 45 degrees, 90 degrees and 135 degrees, and light intensity I in the four directions is obtained according to gray level calculation of the polarization images0，I45，I90And I135According to the polarization intensity I in four directions0，I45，I90And I135Calculating the Stokes parameter S0、S1、S2(ii) a The polarization intensity I, the direction angle phi and the polarization degree rho are calculated by utilizing the Stokes parameters.
Figure BDA0002457871520000031
The polarized image is normalized to the polarized intensity I as a gray scale image, i.e., as shown in fig. 2.
Figure BDA0002457871520000032
And (3) normalizing the radian (-pi, pi) gray scale at each pixel of the polarization image to 0-255 to obtain the image shown in FIG. 3.
Figure BDA0002457871520000041
The degree of polarization is the ratio of the light intensity of the polarized part in the light beam to the whole light intensity, and the value range is [0,1], and the ratio is scaled up to the range [0,255], that is, the image shown in fig. 4 is obtained by standardized gray scale processing.
Deducing a mathematical model of the refractive index n based on the relation between the polarization degree rho and the refractive index n and the zenith angle theta, wherein the zenith angle theta is approximate to the azimuth angle phi, and substituting the azimuth angle phi into the mathematical model of the refractive index n instead of the zenith angle theta to obtain the approximate refractive index
Figure BDA0002457871520000042
A mathematical model;
Figure BDA0002457871520000043
wherein the content of the first and second substances,
A′＝ρ2cos4φ
B′＝2ρ2cos2φ(2sin4φ-sin2φ)-4sin4φcos2φ
C′＝ρ2(2sin4φ-sin2φ)2+4sin6φcos2φ。
the results of the approximate refractive indices of the four comparative examples are shown in fig. 5, in which the ordinate represents the approximate refractive index. As can be seen from fig. 5, the similar refractive indexes of objects having the same material are similar even if the colors are different, and the similar refractive indexes of objects having different materials are greatly different even if the colors are the same, so that it is possible to identify objects having different materials based on the similar refractive indexes.
Using clustering algorithm to approximate refractive index
Figure BDA0002457871520000044
And clustering the data to realize the identification of objects with different materials. As shown in fig. 6, the result of clustering the approximate refractive index by using the clusterdata clustering function of matlab is shown.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (6)

1. A method for recognizing objects made of different materials by utilizing polarization information comprises a polarization camera, an industrial lens, a light source and an industrial personal computer, and is characterized in that: the method comprises the following steps:
the industrial personal computer controls the light source to be lightened and triggers the polarization camera to acquire and process images;
the polarization camera collects polarization images of an object in four directions of 0 degree, 45 degrees, 90 degrees and 135 degrees to obtain polarization intensities I in the four directions0，I45，I90And I135By means of I0，I45，I90And I135Calculating the Stokes parameter S0、S1、S2；
Calculating the polarization intensity I, the direction angle phi and the polarization degree rho by utilizing the Stokes parameters;
deducing a mathematical model of the refractive index n based on the relation between the polarization degree rho and the refractive index n and the zenith angle theta, wherein the zenith angle theta is approximate to the azimuth angle phi, and substituting the azimuth angle phi into the mathematical model of the refractive index n instead of the zenith angle theta to obtain the approximate refractive index
Figure FDA0002457871510000014
A mathematical model;
using clustering algorithm to approximate refractive index
Figure FDA0002457871510000015
And clustering the data to realize the identification of objects with different materials.
2. The method of claim 1, wherein the polarization information is used to identify the different material objects, and the method further comprises: the Stokes parameter S0、S1、S2The calculation process of (2) is as follows:
Figure FDA0002457871510000011
S1＝I0-I90，
S2＝I45-I135，
wherein S is0Represents the total intensity of light, S1Represents the difference between linearly polarized light components of 0 DEG and 90 DEG, S2Representing the difference between the 45 deg. and 135 deg. linearly polarized light components.
3. The method of claim 1, wherein the polarization information is used to identify the different material objects, and the method further comprises: the calculation processes of the polarized light intensity I, the direction angle phi and the polarization degree rho are as follows:
I＝S0，
Figure FDA0002457871510000012
Figure FDA0002457871510000013
4. the method of claim 1, wherein the polarization information is used to identify the different material objects, and the method further comprises: the relation among the polarization degree rho, the refractive index n and the zenith angle theta is as follows:
Figure FDA0002457871510000021
5. the method of claim 4, wherein the polarization information is used to identify the different material objects, and the method further comprises: the mathematical model of the refractive index n:
Figure FDA0002457871510000022
wherein the content of the first and second substances,
A＝ρ2cos4θ
B＝2ρ2cos2θ(2sin4θ-sin2θ)-4sin4θcos2θ
C＝ρ2(2sin4θ-sin2θ)2+4sin6θcos2θ。
6. the method of claim 1, wherein the polarization information is used to identify the different material objects, and the method further comprises: said approximate refractive index
Figure FDA0002457871510000023
The mathematical model is as follows:
Figure FDA0002457871510000024
wherein the content of the first and second substances,
A′＝ρ2cos4φ
B′＝2ρ2cos2φ(2sin4φ-sin2φ)-4sin4φcos2φ
C′＝ρ2(2sin4φ-sin2φ)2+4sin6φcos2φ。
CN202010311100.1A 2020-04-20 2020-04-20 Method for identifying objects of different materials by using polarization information Withdrawn CN111539411A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112058701A (en) * 2020-08-28 2020-12-11 河海大学常州校区 Coal and coal gangue sorting system and method based on polarization imaging
CN112379529A (en) * 2020-11-19 2021-02-19 中国人民解放军国防科技大学 Transparent object surface reflected light separation method based on polarization characteristics
CN112766256A (en) * 2021-01-25 2021-05-07 北京淳中科技股份有限公司 Grating phase diagram processing method and device, electronic equipment and storage medium
CN113283420A (en) * 2021-05-20 2021-08-20 维沃移动通信有限公司 Electronic device, material detection method, material detection device, and readable storage medium
CN113542172A (en) * 2021-07-12 2021-10-22 聊城大学 Elastic optical network modulation format identification method and system based on improved PSO clustering

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112058701A (en) * 2020-08-28 2020-12-11 河海大学常州校区 Coal and coal gangue sorting system and method based on polarization imaging
CN112379529A (en) * 2020-11-19 2021-02-19 中国人民解放军国防科技大学 Transparent object surface reflected light separation method based on polarization characteristics
CN112379529B (en) * 2020-11-19 2022-04-19 中国人民解放军国防科技大学 Transparent object surface reflected light separation method based on polarization characteristics
CN112766256A (en) * 2021-01-25 2021-05-07 北京淳中科技股份有限公司 Grating phase diagram processing method and device, electronic equipment and storage medium
CN112766256B (en) * 2021-01-25 2023-05-30 北京淳中科技股份有限公司 Grating phase diagram processing method and device, electronic equipment and storage medium
CN113283420A (en) * 2021-05-20 2021-08-20 维沃移动通信有限公司 Electronic device, material detection method, material detection device, and readable storage medium
CN113542172A (en) * 2021-07-12 2021-10-22 聊城大学 Elastic optical network modulation format identification method and system based on improved PSO clustering
CN113542172B (en) * 2021-07-12 2023-11-14 聊城大学 Elastic optical network modulation format identification method and system based on improved PSO clustering

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Application publication date: 20200814