Mueller matrix measuring device and calibration method

Abstract

The invention relates to the technical field of optical detection, and particularly provides a Mueller matrix measuring device and a calibration method.The Mueller matrix measuring device comprises a light source, a polarizing light path, a polarization detecting light path and a bidirectional light path, the bidirectional light path comprises a light splitting assembly for splitting polarization modulation light, and part of light beams are emitted to a sample to be measured through the light splitting assembly; the light beam passes through the sample to be detected in forward and reverse directions and then is emitted to the polarization detection light path by the light splitting assembly, and a beam expander can be additionally arranged to increase the diameter of the light beam emitted to the sample to be detected. Through the bidirectional light path design, the measurement light path is completely located on the same side of the to-be-measured sample, Mueller matrix measurement can be achieved without penetrating through the to-be-measured sample or arranging an external light path, the problem that a traditional reflection type ellipsometer cannot detect a high-thickness sample is solved, and medium interference is avoided. And measurement errors are eliminated by means of a plane mirror, and accurate calibration of the Mueller matrix is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of optical detection, and in particular relates to a Mueller matrix measurement device and a calibration method. Background Art

[0002] Polarization property detection technology is an important tool in modern scientific research and industrial applications. By analyzing the polarization state of light, we can gain a deeper understanding of the microstructure and surface properties of materials, thereby providing researchers with more comprehensive scientific research data. Therefore, polarization property detection technology plays an irreplaceable role in fields such as material analysis, environmental monitoring, and biomedical imaging.

[0003] Mueller matrix ellipsometer (MME) is a powerful polarization property detection tool that can obtain all 16 elements of the sample's Mueller matrix without contact. Common Mueller matrix ellipsometers are mainly divided into two categories: transmission type and reflection type. Transmission type Mueller matrix ellipsometer uses vertical incidence to obtain the Mueller matrix through the transmitted light of the sample, while reflection type Mueller matrix ellipsometer uses oblique incidence to obtain the Mueller matrix through the reflected light of the sample.

[0004] The detection light path of the transmission-type Mueller matrix ellipsometer needs to be located on both sides of the sample. If it is used to detect the polarization characteristics of samples in special working environments such as the observation window of a submersible, part of the light path needs to be placed outside the submersible cabin, that is, immersed in seawater. Considering the complex working environment of the deep sea, this solution has great risks and safety hazards. More importantly, the detection light path must pass through seawater, so the detection results will be seriously affected by the optical properties of seawater. Due to the use of oblique incidence, the reflection-type Mueller matrix ellipsometer cannot perform full-aperture detection on thick samples. In addition, due to the size limitations of polarization optical elements, the measurement range of the Mueller matrix ellipsometer cannot meet the measurement requirements of large-aperture samples.

[0005] In view of this, it is urgent to propose a new Mueller matrix measurement device and calibration method to complete the polarization characteristic measurement of large-aperture and high-thickness optical components under special working environments. Summary of the invention

[0006] In view of this, the present invention aims to provide a Mueller matrix measurement device and calibration method, which effectively solves the limitation of the prior art that it is unable to perform full-aperture detection on thick samples through a bidirectional optical path.

[0007] To achieve the above object, the technical solution created by the present invention is implemented as follows: The first aspect of the invention provides a Mueller matrix measurement device, comprising: a light source, a polarizing light path, a polarizing light path, and a bidirectional light path arranged in the exit direction of the polarizing light path; The bidirectional optical path includes a first light splitting component for splitting polarization modulated light emitted from the polarizing optical path; The light beam transmitted by the first beam splitter component is incident on the sample to be tested, and the transmitted light beam is reflected by the sample to be tested to the first beam splitter component, and the light beam is further reflected by the first beam splitter component into the polarization analyzer light path; or, the light beam reflected by the first beam splitter component is incident on the sample to be tested, and the reflected light beam is reflected by the sample to be tested to the first beam splitter component, and the light beam is further transmitted by the first beam splitter component into the polarization analyzer light path.

[0008] Preferably, it also includes: a beam expander disposed between the first beam splitting component and the sample to be measured, for expanding the diameter of the light beam directed to the sample to be measured.

[0009] Preferably, the calculation formula for calculating the unidirectional light path Mueller matrix from the bidirectional light path Mueller matrix is: ; in, is the bidirectional optical path Mueller matrix measured by the Mueller matrix measurement device, is the Mueller matrix of the one-way optical path, is the Mueller matrix of the plane mirror, .

[0010] Preferably, the polarizing optical path includes: a polarizer and a rotatable wave plate arranged along the transmission direction of the light beam, the polarizer is used to process the light beam provided by the light source into a light beam of a specific polarization state, and the wave plate adjusts the light beam of a specific polarization state into a light beam of a different polarization state by rotation.

[0011] Preferably, the polarization analysis optical path includes a second beam splitting component, a first polarization camera, a second polarization camera, and a quarter wave plate arranged between the second beam splitting component and the first polarization camera.

[0012] Preferably, the light beam propagating in the bidirectional optical path is incident vertically on the sample to be measured.

[0013] Preferably, the sample to be tested is an optical system or a single optical element.

[0014] Preferably, the light beam is incident on the optical system in a forward direction and then emitted from the optical system in a reverse direction; or the light beam is incident on the front surface of the single optical element in a forward direction and then emitted from the rear surface of the single optical element in a reverse direction.

[0015] The second aspect of the present invention provides a Mueller matrix calibration method, comprising: S1: Use the Mueller matrix measurement device to measure the sample to be tested to obtain the measured Mueller matrix , the real Mueller matrix of the sample to be tested is constructed as: ; in, is the Mueller matrix of the polarized light path, is the Mueller matrix of the first beam splitter component in the direction in which the light beam is emitted from the first beam splitter component to the sample to be measured, is the true Mueller matrix of the sample to be tested, The first beam splitter component reflects the Mueller matrix emitted from the first beam splitter component to the polarization analysis light path direction, is the Mueller matrix of the polarization light path; S2: A plane reflector is set between the first light splitting component and the sample to be measured, and the Mueller matrix is ​​measured again using the Mueller matrix measurement device to obtain the Mueller matrix , for: ; in, is the Mueller matrix of the plane mirror; S3: Mueller matrix of the first spectrometer is measured separately and the Mueller matrix of the polarization path ,use and Calibrate the real Mueller matrix of the sample to be tested; S4: According to and The Mueller matrix error of the light beam in the process of being emitted from the plane reflector to the polarization analyzer is: ; S5: Using the measured Mueller matrix and error The real Mueller matrix of the sample to be tested is calculated as: .

[0016] The third aspect of the present invention provides a Mueller matrix calibration method, comprising: a: Using the Mueller matrix measurement device as claimed in claim 2 to measure the sample to be measured to obtain the measured Mueller matrix , construct the measured Mueller matrix The expression is: ; in, is the Mueller matrix of the polarized light path, is the Mueller matrix of the first beam splitter component in the direction in which the light beam is emitted from the first beam splitter component to the sample to be measured, is the Mueller matrix of the beam expander in the direction of the light beam from the beam expander to the sample to be measured, that is, the forward Mueller matrix of the beam expander, is the true Mueller matrix of the sample to be tested, The Mueller matrix is ​​a reflection matrix of the first beam splitter component when the light beam is directed from the first beam splitter component to the polarization analyzer light path. is the Mueller matrix of the polarization light path, is the beam expander Mueller matrix in the direction of the light beam emitted from the beam expander to the first beam splitting component, that is, the reverse Mueller matrix of the beam expander; b: Establish the bidirectional Mueller matrix of the beam expander and the sample to be tested as follows: ; c: Set a plane reflector between the first beam splitter and the beam expander, and use the Mueller matrix measurement device to measure and obtain the Mueller matrix again , for: ; in, is the Mueller matrix of the plane mirror; d: Mueller matrix of the first spectrometer component measured separately and the Mueller matrix of the polarization path ,use and Calibrate the real Mueller matrix of the sample to be tested; e: According to and The Mueller matrix error of the light beam in the process of being emitted from the plane reflector to the polarization analyzer is: ; f: Using the measured Mueller matrix and error The Mueller matrix of the beam expander and the sample to be measured is expressed as: ; g: Move the plane reflector between the beam expander and the sample to be measured, and use the Mueller matrix measurement device to measure and obtain the Mueller matrix again. , for: ; h: Establish the bidirectional Mueller matrix of the beam expander as: ; The forward Mueller matrix of the beam expander is calculated by the bidirectional Mueller matrix of the beam expander. and the inverse Mueller matrix ; j: The forward Mueller matrix of the beam expander and the inverse Mueller matrix The bidirectional Mueller matrix of the beam expander and the sample to be tested is obtained as follows: .

[0017] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention adopts a bidirectional optical path design so that the measurement optical path is completely located on the same side of the sample to be measured. The device optical path does not need to penetrate the sample to be measured or arrange an external optical path to achieve Mueller matrix measurement, avoiding the risk of external optical path in special environments such as deep sea and high pressure. It also avoids the light passing through seawater or other media, eliminates the interference of environmental media on the measurement results, and improves the detection reliability. In addition, the bidirectional optical path design is adopted, and the light passes through the sample to be measured twice vertically, forward and backward. Combined with the mathematical solution method, a conversion formula from the bidirectional Mueller matrix to the unidirectional matrix is ​​proposed, which accurately restores the true polarization characteristics of the sample and avoids the error introduced by the bidirectional optical path. It effectively solves the problem that the traditional reflection ellipsometer cannot detect high-thickness samples due to oblique incidence, and provides a solution for full-aperture detection of thick samples.

[0018] The present invention adds a beam expander in the bidirectional optical path, significantly increasing the detection beam aperture and supporting full-aperture polarization characteristic detection of large-aperture optical elements. The present invention also provides two corresponding calibration schemes, corresponding to the two cases with and without a beam expander respectively. The calibration method eliminates the errors introduced by the polarizing light path, the analyzing light path, the spectroscopic component and the beam expander with the help of the plane reflector optical path, and accurately obtains the true Mueller matrix of the sample to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a schematic structural diagram of a Mueller matrix measurement device provided according to Embodiment 1 of the present invention; Figure 2 is a schematic diagram of Mueller matrix calibration provided by Example 2 of the present invention; Figure 3 Schematic diagram of Mueller matrix calibration provided according to Example 3 of the present invention.

[0020] Reference numerals include: Polarizer 101 , wave plate 102 , first beam splitter 103 , beam expander 104 , second beam splitter 105 , quarter wave plate 106 , first polarization camera 107 , second polarization camera 108 , light source 109 , plane reflector 110 , and sample to be measured 111 . DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the invention clearer, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and do not constitute a limitation to the invention. Similar components in different embodiments use associated similar component numbers. In the following embodiments, many detailed descriptions are to enable the invention to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other components, materials, and methods. In some cases, some operations related to the invention are not shown or described in the specification, in order to avoid the core part of the invention being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed.

[0023] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0024] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0025] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0026] See also Figure 1 In one embodiment 1 of the present invention, a Mueller matrix measurement device is provided, which mainly includes a light source 109, a polarizing optical path, a polarizing optical path, and a bidirectional optical path, wherein the light source 109 is used to provide a measuring beam. The measuring beam emitted by the light source 109 is incident on the polarizing optical path for polarization modulation. The polarizing optical path is composed of a polarizer 101 and a rotatable wave plate 102. The transmission axis direction of the polarizer 101 is horizontal. The polarizer 101 and the wave plate 102 are coaxially arranged. The reference direction of the wave plate 102 is the transmission axis direction of the polarizer 101. The measuring beam passes through the polarizer 101 and the wave plate 102 in sequence. The wave plate 102 is clamped by a precision rotating motor to achieve high-precision rotation. As the wave plate 102 rotates, the measuring beam is modulated to generate polarization modulated light of different polarization states.

[0027] After the light beam is emitted from the polarizing optical path, it enters the bidirectional optical path arranged at the rear end of the polarizing optical path. The bidirectional optical path mainly includes the first beam splitter component 103, which is a beam splitter prism. The function of the first beam splitter component 103 is to direct the forward transmitted light beam to the sample to be tested 111, and to direct the reverse transmitted light beam reflected by the sample to be tested 111 to the polarizing optical path. Specifically, the first beam splitter component 103 can be designed in two ways, one of which is to have a transmission effect on the forward transmitted light beam emitted from the polarizing optical path to the first beam splitter component 103, and to have a reflection effect on the reverse transmitted light beam emitted from the sample to be tested 111 to the first beam splitter component 103. In this design, the bidirectional optical path is coaxial with the polarizing optical path, and the light beam is transmitted through the first beam splitter component 103 after being emitted from the polarizing optical path, and continues to be transmitted and emitted into the sample to be tested 111. The sample 111 to be tested is generally an optical system or a single optical element with a relatively large thickness. When the sample 111 to be tested is an optical system, after the light beam enters the optical system, it is transmitted along the optical path of the optical system, and is reflected at the last end of the optical system, and is reflected out through the optical system again, realizing forward and reverse bidirectional transmission in the optical system. After being emitted from the optical system, it is irradiated on the first beam splitter component 103 again, and the first beam splitter component 10 reflects the light beam to the polarization light path. If the optical system is a fully transmissive type, in order to enhance the intensity of the light beam reflected by the optical system, it is usually possible to choose to plate a reflection enhancement film on the rear surface of the last element of the optical system. Similarly, when the sample 111 to be tested is a single optical element, the light beam is incident from the front surface of the single optical element, reflected by the rear surface of the single optical element, and reflected out through the single optical element again, realizing forward and reverse bidirectional transmission in the single optical element. After being emitted from the single optical element, it is irradiated on the first beam splitter component 103 again, and the first beam splitter component 10 reflects the light beam to the polarization light path. In order to enhance the intensity of the light beam reflected by the rear surface of the single optical element, it is usually possible to coat the rear surface of the single optical element with an anti-reflection film.

[0028] Another design is: it has a reflection effect on the forward transmission light beam emitted from the polarizing light path to the first light splitting component 103, and has a transmission effect on the reverse transmission light beam emitted from the sample 111 to the first light splitting component 103. At this time, the polarizing light path and the analyzing light path are coaxial, and the bidirectional light path is perpendicular to the polarizing light path. The specific light beam transmission process is the same as the first design method, and will not be repeated here.

[0029] The light beam is directed to the polarization analyzer optical path by the first beam splitter component 103, and the polarization analyzer optical path includes the second beam splitter component 105, the quarter wave plate 106, the first polarization camera 107 and the second polarization camera 108, wherein the second beam splitter component 105 is used to split the light beam incident on the polarization analyzer optical path. After the light beam enters the polarization analyzer optical path, it first enters the second beam splitter component 105, and the second beam splitter component 105 uses a beam splitter prism with a splitting ratio of 50:50. The second beam splitter component 105 splits the light beam into two beams, one of which is directed to the quarter wave plate 106, and is modulated by the quarter wave plate 106 and then incident on the first polarization camera 107; the other beam is directly incident on the second polarization camera 108. In the embodiment of the present invention, four polarization channels (0°, 45°, 90°, 135°) of the second polarization camera 108 and two polarization channels (45°, 135°) of the first polarization camera 107 after passing through the quarter wave plate 106 are selected, for a total of six polarization channels. The polarization matrix is ​​composed of different polarization channels. All Stokes parameters are obtained through a single shot, and then the Mueller matrix is ​​calculated.

[0030] In order to enhance the applicability of the Mueller matrix measurement device, a beam adjuster is further provided at the rear end of the first beam splitter component 103, that is, on the optical path between the first beam splitter component 103 and the sample to be measured 111, to adjust the diameter of the beam directed to the sample to be measured 111. Usually, in order to meet the detection of large-aperture components, the adjuster is a beam expander, which expands the beam diameter to adapt to the Mueller matrix measurement of the large-aperture sample to be measured 111, thereby overcoming the disadvantage that the Mueller matrix ellipsometer (MME) cannot detect large-aperture components.

[0031] In addition, the embodiment of the present invention realizes that the light source 109, the polarizing light path, the polarizing light path and the bidirectional light path are all arranged on the same side of the sample to be tested 111 through the bidirectional light path design, avoiding the problem that the traditional light path needs to penetrate the sample to be tested 111, or arrange an external light path. In special environments such as deep sea and high pressure, the design of the present invention can effectively avoid the damage of deep sea or high pressure conditions to the equipment. At the same time, the light does not pass through the seawater medium, and the detection result avoids medium interference, which improves the detection reliability. And the light beam directed to the sample to be tested 111 is vertically incident, which solves the problem that the traditional reflective Mueller matrix ellipsometer needs to use oblique incidence.

[0032] Since the present invention adopts a bidirectional optical path, the detection light beam passes through the sample 111 to be measured twice, therefore, the Mueller matrix measured by the Mueller matrix measurement device of the embodiment of the present invention is essentially a bidirectional optical path Mueller matrix, so it is necessary to derive a calculation formula for calculating the unidirectional optical path Mueller matrix from the bidirectional optical path Mueller matrix. The Mueller matrix construction process of the embodiment of the present invention is the same as the principle of the traditional method, and is only briefly described as follows: Based on the Mueller matrix-Stokes vector theory, a theoretical model of the Mueller matrix measurement device is established. The entire optical path of the Mueller matrix measurement device can be described by the Mueller matrix: (0.1) in, is the horizontal linear polarization of the light emitted by the polarizer 101, that is, the Stokes vector of the forward incident light directed toward the sample 111 to be tested, The Mueller matrix measuring device measures the bidirectional optical path Mueller matrix of the sample 111 to be measured, δ is the phase delay of the wave plate 102, θ is the azimuth angle of the wave plate 102, t represents the time variable, represents the rotation matrix of the wave plate 102, It is the polarization state of the light after being modulated by the wave plate 102 and the sample to be tested 111, that is, the Stokes vector of the light emitted in the reverse direction by the sample to be tested 111.

[0033] The information obtained by the different polarization channels of the first polarization camera 107 and the second polarization camera 108 is the light intensity, which is the Stokes vector of the outgoing light. The first element of , so the light intensity information obtained by a single measurement of a single polarization channel is: (0.2) Where I represents the light intensity measured in a certain polarization channel, Each element in corresponds to the measurement result of a polarization channel. Represents the response coefficient of different polarization channels to each component of the Stokes vector. Each element in the matrix It represents the response degree of the corresponding polarization channel to the specific component of the Stokes vector. is the Stokes vector of the outgoing light, which represents the polarization state of the outgoing light and is used to describe the different polarization characteristics of light.

[0034] The embodiment of the present invention selects 4 polarization channels (0°, 45°, 90°, 135°) of the second polarization camera 108 and 2 polarization channels (45°, 135°) of the first polarization camera 107 after passing through the quarter wave plate 106, for a total of 6 polarization channels. Therefore, the polarization matrix P composed of different polarization channels is: (0.3) So each measurement process can be described as: (0.4) in, is the light intensity vector output from the six polarization channels, which can be simplified to obtain: (0.5) in, is the polarized light intensity detected by polarization channel i when the wave plate 102 rotates by an angle of θ, The Mueller matrix of the optical element to be measured is formed. As the wave plate 102 rotates continuously, the Stokes vector of the incident light forms the incident matrix of the system, and the Stokes vector of the outgoing light forms the outgoing matrix of the system. The wave plate 102 rotates at least four times, constructing 16 equations and solving the 16 unknowns of the Mueller matrix.

[0035] Based on the above, the outgoing light matrix in the reverse transmission process can be calculated as: (0.6) in, is the measured optical path Mueller matrix, represents the incident matrix generated by the rotation of the wave plate 102, Represents the outgoing light matrix during the reverse transmission process.

[0036] Formula (0.6) is further adjusted to: (0.7) The above process is the basic principle of the traditional Mueller matrix polarimeter measurement. However, there is a bidirectional optical path in the Mueller matrix measurement device of the embodiment of the present invention, and the light will pass through the sample 111 to be measured twice, so the optical path Mueller matrix measured in the above formula (0.7) is In essence, it is a bidirectional Mueller matrix, that is, the matrix reflects both the light emitted from the first light splitting component 103 to the sample to be tested 111 and the light emitted from the sample to be tested 111. The bidirectional Mueller matrix cannot correctly characterize the polarization properties of the sample to be tested 111, so it is necessary to calculate the unidirectional Mueller matrix from the bidirectional Mueller matrix. Therefore, the Mueller matrix measurement device of the embodiment of the present invention measures the bidirectional Mueller matrix obtained by the actual measurement. The mathematical relationship between it and the one-way Mueller matrix is: (0.8) in, and is the Mueller matrix of the one-way optical path, The Mueller matrix is ​​a unidirectional optical path of the light beam transmitted in the forward direction, which is emitted from the first light splitting component 103 to the direction of the sample to be tested 111. The Mueller matrix is ​​a unidirectional optical path of the light beam transmitted in the reverse direction from the sample to be tested 111 to the first light splitting component 103. is the Mueller matrix of the plane mirror, specifically: (0.9) According to the polar decomposition of the Mueller matrix, the Mueller matrix of a single light passing through the sample 111 to be tested can be expressed as: (0.10) in, represents the phase delay of the matrix, and the corresponding Mueller matrix is: (0.11) Represents the two-way attenuation of the matrix, and the corresponding Mueller matrix is: (0.12) in, , , are different phase delay components of the sample 111 to be tested, , , They are different two-way attenuation scores of the sample 111 to be tested.

[0037] When the light propagates in the reverse direction, the polarization characteristics of the sample 111 to be tested remain unchanged, but the coordinate system changes, so the polarization component is reversed. ∆ is a matrix depolarizer. According to the experimental results, the depolarizer can be expressed as: (0.13) in, , , is the polarization component of the depolarizer, indicating the polarization performance of the depolarizer, a and b is the linear depolarization parameter, c is the circular depolarization parameter.

[0038] The depolarization properties of the sample 111 to be tested are the same in the forward transmission and the reverse transmission, and the depolarization parameters do not change. , The sign of is reversed. Therefore, the back-propagated Mueller matrix is ​​transformed to: (0.14) From equations (0.8) and (0.14), the vertical bidirectional Mueller matrix measured by the Mueller matrix measurement device can be expressed as: (0.15) Therefore, the solution formula for obtaining the forward Mueller matrix through the vertical bidirectional Mueller matrix is: (0.16) Based on the above Mueller matrix measurement device, the present invention further proposes a corresponding Mueller matrix calibration method. Since the Mueller matrix measurement device of Embodiment 1 of the present invention can be designed with a beam expander 104 or not, there are two different calibration methods, which are as follows: See also Figure 2 In one embodiment 2 of the present invention, a Mueller matrix calibration method is provided. The method is mainly aimed at the measurement device without the beam expander 104 in the embodiment 1. When the Mueller matrix measurement device without the beam expander 104 is used to measure the Mueller matrix of the sample 111 to be measured, the real Mueller matrix of the sample 111 to be measured is calibrated by the following method: S1: First, the Mueller matrix measurement device without the beam expander 104 is used to measure the sample 111 to obtain the measured Mueller matrix , the measured Mueller matrix It will be affected by the polarization optical path error, the bidirectional optical path error, and the polarization optical path error, wherein the bidirectional optical path error is mainly introduced by the first light splitting component 103. Therefore, according to the polarization optical theory, the measured Mueller matrix can be It is expressed as: (0.17) in, is the Mueller matrix of the polarized light path, is the Mueller matrix of the first beam splitter component 103 in the direction of the light beam emitted from the first beam splitter component 103 to the sample to be tested 111, is the real Mueller matrix of the sample 111 to be tested, The first light splitting component 103 reflects the Mueller matrix emitted from the first light splitting component 103 to the polarization analysis light path direction, is the Mueller matrix of the polarization light path.

[0039] According to the above formula, the real Mueller matrix of the sample 111 to be tested can be further constructed as: (0.18) S2: In order to eliminate the influence of the polarization optical path error, the bidirectional optical path error, and the polarization optical path error, a plane reflector 110 is set on the optical path between the first light splitting component 103 and the sample to be measured 111, and the Mueller matrix of the optical path at this time is measured again using the Mueller matrix measurement device , at this time the optical path Mueller matrix It can be expressed as: (0.19) in, is the Mueller matrix of the plane mirror, and equal.

[0040] S3: Using other existing methods to separately measure the Mueller matrix of the first light splitting component 103 in advance and the Mueller matrix of the polarization path , the measurement process can be measured by traditional equipment or methods such as Mueller matrix ellipsometer. and The real Mueller matrix of the sample 111 to be measured is calibrated.

[0041] S4: Based on the results of S2 and S3, the Mueller matrix error of the reflected echo optical path of the sample 111 to be tested (or the Mueller matrix error of the rear optical path of the sample 111 to be tested) is derived and calibrated in the process of the light beam of the sample 111 to be tested being emitted from the plane reflector 110 to the polarization analyzer optical path: (0.20) S5: Substitute the rear optical path error formula (0.20) obtained in S4 into the real Mueller matrix formula (0.18) of the sample 111 to be tested in S1 to obtain the real Mueller matrix of the sample to be tested, which is calculated as follows: (0.21) All matrices in formula (0.21) have been calibrated, so now we can use the measured matrix The real Mueller matrix of the sample 111 to be tested is calculated by the calibration result .

[0042] See also Figure 3 In one embodiment 3 of the present invention, another Mueller matrix calibration method is provided. This method is mainly aimed at the measurement device with a beam expander 104 in embodiment 1. When the Mueller matrix measurement device with a beam expander 104 is used to measure the Mueller matrix of the sample 111 to be measured, the real Mueller matrix of the sample 111 to be measured is calibrated by the following method: a: Similarly, firstly, the Mueller matrix measuring device with a beam expander 104 is used to measure the sample 111 to obtain the measured Mueller matrix , at this time the measured Mueller matrix The numerical value has changed from the data measured in Example 2, and both represent the measured Mueller matrix under different conditions. It will be affected by the polarization optical path error, the bidirectional optical path error, and the polarization optical path error. The bidirectional optical path error includes not only the error introduced by the first beam splitter 103, but also the error introduced by the beam expander 104. Therefore, according to the theory of polarization optics, the measured Mueller matrix can be It is expressed as: (0.22) in, is the Mueller matrix of the polarized light path, is the first beam splitter component Mueller matrix in the direction of the light beam emitted from the first beam splitter component 103 to the sample to be tested 111, is the Mueller matrix of the beam expander 104 in the direction of the light beam emitted from the beam expander 104 to the sample 111 to be measured, that is, the forward Mueller matrix of the beam expander 104, is the real Mueller matrix of the sample 111 to be tested, The Mueller matrix is ​​a reflection matrix of the first beam splitter component 103 which is emitted from the first beam splitter component 103 to the polarization analysis light path. is the Mueller matrix of the polarization light path, It is the Mueller matrix of the beam expander 104 in the direction of the light beam emitted from the beam expander 104 to the first beam splitting component 103 , that is, the reverse Mueller matrix of the beam expander 104 .

[0043] b: According to formula (0.22), the bidirectional Mueller matrix of the beam expander 104 and the sample 111 is established as a whole (i.e., the Mueller matrix of the light beam emitted from the beam expander 104 to the sample 111, and then reflected by the sample 111 and emitted again through the beam expander 104) is: (0.23) c: In order to eliminate the influence of the polarization optical path error, the first beam splitter 103, and the polarization optical path error, a plane reflector 110 is set on the optical path between the first beam splitter 103 and the sample 111 to be measured, and the Mueller matrix at this time is measured again using the Mueller matrix measurement device , for: (0.24) d: Using other existing methods to separately measure the Mueller matrix of the first light splitting component 103 in advance and the Mueller matrix of the polarization path , the measurement process can be measured by traditional equipment or methods such as Mueller matrix ellipsometer. and The real Mueller matrix of the sample 111 to be measured is calibrated.

[0044] e: Based on the results of steps b and c, the Mueller matrix error of the reflected light path of the sample 111 to be measured is derived and calibrated in the process of the light beam of the sample 111 to be measured being directed from the plane reflector 110 to the polarization analyzer light path: (0.25) f: Substitute the optical path error formula (0.25) obtained in step e into the actual Mueller matrix formula (0.22) of the sample 111 to be tested in step a, and use the measured Mueller matrix and error The Mueller matrix of the beam expander 104 and the sample to be tested 111 as a whole is expressed as: (0.26) g: In order to calibrate the Mueller matrix of the beam expander 104 separately, the error introduced by the beam expander 104 is eliminated, such as Figure 3 As shown, the plane reflector 110 needs to be moved to the optical path between the beam expander 104 and the sample to be tested 111 to separate the beam expander 104 from the sample to be tested 111. At this time, the Mueller matrix of the optical path is measured again using the Mueller matrix measurement device to obtain the Mueller matrix of the optical path at this time. for: (0.27) h: Same processing principle as steps a to e, using The Mueller matrix of the beam expander 104 is calibrated to obtain a bidirectional Mueller matrix of the beam expander 104: (0.28) According to the calculation formula (0.16) of the Mueller matrix measurement device provided above for calculating the Mueller matrix of the unidirectional optical path from the Mueller matrix of the bidirectional optical path, the forward transmission Mueller matrix of the beam expander 104 is calculated from the bidirectional Mueller matrix of the beam expander 104: and the reverse transmission Mueller matrix , complete the individual calibration of the beam expander 104.

[0045] The beam expander 104 transmits the Mueller matrix forward. and the reverse transmission Mueller matrix Substituting the bidirectional Mueller matrix (0.26) of the beam expander 104 and the sample 111 to be tested in step f, the real Mueller matrix of the sample 111 to be tested can be obtained as: (0.29) All matrices in formula (0.29) have been calibrated, so now we can use the measured matrix The real Mueller matrix of the sample 111 to be tested is calculated by the calibration result .

[0046] In short, the above description is only a preferred embodiment of this specification and is not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included in the protection scope of this specification.

[0047] The systems, devices, modules or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0048] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0049] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0050] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A Mueller matrix measurement device, comprising a light source, a polarizing light path and an analyzing light path, characterized in that: It also includes a bidirectional light path arranged in the outgoing direction of the polarized light path; The bidirectional optical path includes a first light splitting component for splitting the polarization modulated light emitted from the polarizing optical path; The light beam transmitted by the first beam splitter component is incident on the sample to be tested, the transmitted light beam is reflected by the sample to be tested to the first beam splitter component, and the light beam is further reflected by the first beam splitter component into the polarizer light path; or, the light beam reflected by the first beam splitter component is incident on the sample to be tested, the reflected light beam is reflected by the sample to be tested to the first beam splitter component, and the light beam is further transmitted by the first beam splitter component into the polarizer light path.

2. The Mueller matrix measurement device according to claim 1, characterized in that: Also includes: The beam expander disposed between the first light splitting component and the sample to be measured is used to expand the diameter of the light beam directed to the sample to be measured.

3. The Mueller matrix measurement device according to claim 1, characterized in that: The calculation formula for calculating the Mueller matrix of a unidirectional light path from the Mueller matrix of a bidirectional light path is: ； in, is the bidirectional optical path Mueller matrix measured by the Mueller matrix measurement device, is the Mueller matrix of the one-way optical path, is the Mueller matrix of the plane mirror, .

4. The Mueller matrix measurement device according to claim 1, characterized in that: The polarizing optical path includes: a polarizer and a rotatable wave plate arranged along the light beam transmission direction. The polarizer is used to process the light beam provided by the light source into a light beam with a specific polarization state, and the wave plate adjusts the light beam with a specific polarization state into a light beam with a different polarization state by rotating.

5. The Mueller matrix measurement device according to claim 1, characterized in that: The polarization analyzer optical path includes a second beam splitter component, a first polarization camera, a second polarization camera, and a quarter wave plate arranged between the second beam splitter component and the first polarization camera.

6. The Mueller matrix measurement device according to claim 1, characterized in that: The light beam propagating in the bidirectional light path is incident vertically on the sample to be measured.

7. The Mueller matrix measurement device according to claim 1, characterized in that: The sample to be tested is an optical system or a single optical element.

8. The Mueller matrix measurement device according to claim 7, characterized in that: The light beam enters the optical system in a forward direction and then exits from the optical system in a reverse direction; or the light beam enters the front surface of the single optical element in a forward direction and then exits from the rear surface of the single optical element in a reverse direction.

9. A Mueller matrix calibration method, characterized in that: include: S1: Using the Mueller matrix measurement device as described in any one of claims 1, 3 to 8 to measure the sample to be measured to obtain a measured Mueller matrix , the real Mueller matrix of the sample to be tested is constructed as: ； in, is the Mueller matrix of the polarized light path, is the Mueller matrix of the first beam splitter component in the direction in which the light beam is emitted from the first beam splitter component to the sample to be measured, is the true Mueller matrix of the sample to be tested, The first beam splitter component reflects the Mueller matrix emitted from the first beam splitter component to the polarization analysis light path direction, is the Mueller matrix of the polarization light path; S2: a plane reflector is arranged between the first light splitting component and the sample to be measured, and the Mueller matrix is ​​measured again using the Mueller matrix measurement device to obtain the Mueller matrix , for: ； in, is the Mueller matrix of the plane mirror; S3: Mueller matrix of the first spectrometer is measured separately and the Mueller matrix of the polarization path ,use and Calibrate the real Mueller matrix of the sample to be tested; S4: According to and The Mueller matrix error of the light beam in the process of being emitted from the plane reflector to the polarization analyzer is: ； S5: Using the measured Mueller matrix and error The real Mueller matrix of the sample to be tested is calculated as: 。 10. A Mueller matrix calibration method, characterized in that: include: a: Using the Mueller matrix measurement device as described in claim 2 to measure the sample to be measured to obtain the measured Mueller matrix , construct the measured Mueller matrix The expression is: ； in, is the Mueller matrix of the polarized light path, is the Mueller matrix of the first beam splitter component in the direction in which the light beam is emitted from the first beam splitter component to the sample to be measured, is the Mueller matrix of the beam expander in the direction of the light beam from the beam expander to the sample to be measured, that is, the forward Mueller matrix of the beam expander, is the true Mueller matrix of the sample to be tested, The Mueller matrix is ​​a reflection matrix of the first beam splitter component when the light beam is directed from the first beam splitter component to the polarization analyzer light path. is the Mueller matrix of the polarization light path, is the beam expander Mueller matrix in the direction of the light beam emitted from the beam expander to the first beam splitting component, that is, the reverse Mueller matrix of the beam expander; b: Establish the bidirectional Mueller matrix of the beam expander and the sample to be tested as follows: ； c: a plane reflector is arranged between the first light splitting component and the beam expander, and the Mueller matrix is ​​measured again using the Mueller matrix measurement device to obtain the Mueller matrix , for: ； in, is the Mueller matrix of the plane mirror; d: Mueller matrix of the first spectrometer component measured separately and the Mueller matrix of the polarization path ,use and Calibrate the real Mueller matrix of the sample to be tested; e: According to and The Mueller matrix error of the light beam in the process of being emitted from the plane reflector to the polarization analyzer is: ； f: Using the measured Mueller matrix and error The Mueller matrix of the beam expander and the sample to be measured is expressed as: ； g: Move the plane reflector between the beam expander and the sample to be measured, and use the Mueller matrix measurement device to measure and obtain the Mueller matrix again. , for: ； h: Establish the bidirectional Mueller matrix of the beam expander as: ； The forward Mueller matrix of the beam expander is calculated by the bidirectional Mueller matrix of the beam expander. and the inverse Mueller matrix ; j: The forward Mueller matrix of the beam expander and the inverse Mueller matrix The bidirectional Mueller matrix of the beam expander and the sample to be tested is obtained as follows: 。

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