A spectropolarimeter and its measurement method

Abstract

The present invention provides a spectropolarimeter and a measurement method thereof. The spectropolarimeter comprises: a polarizing unit, the polarizing unit being used to generate a polarized light beam to be measured, the polarizing unit comprising: a light source, a polarizer and a quarter-wave plate arranged in sequence, the polarizer being located between the light source and the quarter-wave plate; and an analyzing unit, the polarizing unit comprising: a diffraction optical element, a double-cemented achromatic plano-convex lens, a vortex quarter-wave plate, an analyzer and a camera arranged in sequence. The diffraction optical element uses an optical axis as a symmetry axis to disperse light of different wavelengths to different angles, and collimates the light into a ring light beam after passing through the double-cemented achromatic plano-convex lens. The wavelength of the ring light beam increases continuously from the inside to the outside of the ring cross section of the ring light beam in a radial direction.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a spectropolarimeter and a measurement method thereof. Background Art

[0002] Polarization and wavelength (or frequency) are the basic properties of light waves and are also important information carriers. Any target will exhibit polarization characteristics determined by its own characteristics and the basic laws of optics in the process of emitting or reflecting (scattering, transmitting, diffracting) light waves. By detecting and analyzing the polarization characteristics of light waves, information such as the target material, complex refractive index, reflectivity, and surface normal direction can be obtained. The spectrum is a record of the wavelength components of the light waves radiated by a substance. It is a basic optical property of matter and has important applications in analyzing material structure, chemical composition, particle motion, local electromagnetic fields, etc. Spectral polarization detection technology combines polarization detection and spectral acquisition functions into one. In addition to obtaining spectral information, it also obtains polarization information of the detected object, which can detect and analyze the target from more dimensions. It has important applications in polarization remote sensing, biomedicine, astrophysics, chemical engineering and other fields.

[0003] Currently, there are many methods for implementing polarization detection, which can be divided into several categories based on the measurement principle, such as spectroscopic, time-series modulation, spatial modulation, and wavelength modulation. Spectroscopic polarization detection uses spectroscopic devices or subsystems to construct multiple measurement channels. By setting different polarization optical elements and detectors in each channel, the output light intensity in different states is simultaneously obtained, and the Stokes vector of the light wave is then calculated. Spectroscopic polarimeter can obtain the different polarization components of the light wave in real time, but the multi-channel structure will increase the size of the equipment and reduce energy utilization. The use of multiple detectors increases the cost and also places strict requirements on their spatial alignment. The time-series modulation detection system modulates the light intensity by rotating the optical elements in the light path or introducing a time-series modulation device in the light path, and measures the modulated light intensity to obtain the Stokes parameter. This type of detection system has a simple structure, but it is generally suitable for measuring light waves with slower polarization state changes, and the mechanical rotation of the optical elements and the fluctuation of the light source power will introduce measurement errors. Spatially modulated polarization systems utilize spatially modulating devices to modulate the polarization state of light waves, producing a spatially varying light intensity distribution. Polarization information is then obtained by analyzing and processing the intensity-modulated image. Spatially modulated polarization detectors require no mechanical motion or active components, offer a simple optical path, excellent stability, and fast measurement speed, and possess significant development potential. To further implement spectral polarization detection, these polarization detection systems typically require multiple measurements in conjunction with a monochromator, grating, and spectrometer, increasing system complexity and reducing measurement efficiency. Wavelength-modulated polarization detection systems utilize multi-stage wave plates to modulate the polarization spectrum to be measured onto multiple high-frequency carriers. A spectrometer receives the modulated signal and analyzes the spectrum to determine the polarization state of the light waves. Wavelength-modulated polarization detectors can achieve spectral polarization detection with high measurement speed and without interference from moving components. However, the multi-stage wave plates are sensitive to the incident angle of the light wave and ambient temperature, and their measurement bandwidth is narrow, resulting in lower accuracy.

[0004] Based on the above analysis, it is necessary to study a spectropolarimeter with simple system structure, good stability, fast measurement speed, high accuracy and wide spectrum. Summary of the Invention

[0005] The present invention provides a spectropolarimeter and a measurement method thereof to overcome the defects of the prior art.

[0006] The present invention provides a spectropolarimeter, comprising: a polarizing unit, the polarizing unit being used to generate a polarized light beam to be measured, the polarizing unit comprising: a light source, a polarizer and a quarter-wave plate arranged in sequence, the polarizer being located between the light source and the quarter-wave plate; and an analyzing unit, the polarizing unit comprising: a diffractive optical element, a double-cemented achromatic plano-convex lens, a vortex quarter-wave plate, an analyzer and a camera arranged in sequence, wherein the diffractive optical element takes an optical axis as a symmetry axis, disperses light of different wavelengths to different angles, and collimates the light into a ring light beam after passing through the double-cemented achromatic plano-convex lens, wherein the wavelength of the ring light beam continuously increases from the inside to the outside of the ring cross section of the ring light beam.

[0007] The present invention also provides a measurement method for a spectropolarimeter, which uses the spectropolarimeter of the present invention, including: step S1: obtaining the corresponding relationship between the pixel radius and the wavelength of the light intensity modulation pattern, including: using filters of the first working wavelength to the Nth working wavelength to be placed between the light source and the polarizer, respectively, using a camera to collect the corresponding first light intensity modulation pattern to the Nth light intensity modulation pattern, where N is an integer greater than or equal to 2; obtaining the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern; based on the data of the first working wavelength to the Nth working wavelength and the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern, fitting to obtain the corresponding relationship between the wavelength and the pixel radius r of the circular light beam Step S2: Get the modulation vector of the polarization analyzer Including: setting the polarizing unit to generate 0 degree linear polarized light, 0 degree linear polarized light incident on the polarization analyzer unit, using the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate 45-degree linear polarized light, and the 45-degree linear polarized light is incident on the analyzer unit. Use the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate 90-degree linear polarized light, and the 90-degree linear polarized light is incident on the analyzer unit. Use the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate left-handed circularly polarized light, and the left-handed circularly polarized light is incident on the analyzer unit. Use the camera to capture the light intensity modulation image and obtain the corresponding light intensity modulation function Modulation vector of the polarization analyzer It can be calculated by the following formula: Step S3: The camera collects the test light intensity modulation image corresponding to the polarized light beam to be measured, and obtains the test light intensity modulation function according to the test light intensity modulation image. The test light intensity modulation function is the intensity of the test light intensity modulation image as the azimuth angle increases. Function of change; modulation function and modulation vector according to the test light intensity Get the Stokes vector of the polarized beam to be measured.

[0008] The technical solution of the present invention has the following beneficial effects:

[0009] The spectropolarimeter provided by the technical solution of the present invention has a simple system structure, good stability, fast measurement speed and high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 is a schematic structural diagram of a spectropolarimeter according to an embodiment of the present invention;

[0012] Figure 2 yes Figure 1 Schematic diagram of dispersion of diffractive optical elements;

[0013] Figure 3 Formulating a pattern for the first light intensity;

[0014] Figure 4 Customizing a pattern for the second light intensity;

[0015] Figure 5 Create patterns for the third light intensity;

[0016] Figure 6 Patterning for the fourth light intensity;

[0017] Figure 7 Create patterns for the fifth light;

[0018] Figure 8 The light intensity modulation image corresponding to 0 degree linear polarization light;

[0019] Figure 9 The light intensity modulation image corresponding to 45-degree linear polarized light;

[0020] Figure 10 The light intensity modulation image corresponding to 90-degree linear polarized light;

[0021] Figure 11 The light intensity modulation image corresponding to left-handed circularly polarized light;

[0022] Figure 12 is the modulation parameter Schematic diagram of;

[0023] Figure 13 is the modulation parameter Schematic diagram of;

[0024] Figure 14 is the modulation parameter Schematic diagram of;

[0025] Figure 15 is the modulation parameter Schematic diagram of;

[0026] Figures 16 to 19 Light intensity modulation images collected by the camera in 4 states;

[0027] Figure 20 for Figure 19 The light intensity modulation function obtained by analyzing the light intensity modulation image shown;

[0028] Figure 21 The comparison diagram of the theoretical and measured curves of Stokes parameters under the test conditions of α = 43° and β = 85°;

[0029] Figure 22 for Figure 21 The error between the corresponding measured curve and the theoretical curve;

[0030] Figure 23 The figure is a comparison between the theoretical and measured curves of Stokes parameters under the test conditions of α = 5° and β = 5°;

[0031] Figure 24 for Figure 23 The error between the corresponding measured curve and the theoretical curve;

[0032] Figure 25 The figure is a comparison between the theoretical and measured curves of Stokes parameters under the test conditions of α = 85° and β = 85°;

[0033] Figure 26 for Figure 25 The error between the corresponding measured curve and the theoretical curve;

[0034] Figure 27 The comparison diagram of the theoretical curve and the measured curve of Stokes parameters under the test conditions of α = 40° and β = 5°;

[0035] Figure 28 for Figure 27 The error between the corresponding measured curve and the theoretical curve;

[0036] Figure 29 Schematic diagram of space radius d and pixel radius r;

[0037] Figure 30 is the phase distribution of the diffractive optical element;

[0038] Figure 31 Schematic diagram of the structure of a superatom;

[0039] Figure 32 Phase delay of "superatoms" of different sizes a at 700nm wavelength;

[0040] Figure 33 is the top view of the diffractive optical element;

[0041] Figure 34 This is a 45-degree oblique view of the middle part of the diffractive optical element;

[0042] Figure 35 This is a 45-degree oblique view of the bottom of the diffractive optical element. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0044] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0046] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] An embodiment of the present invention provides a spectropolarimeter, referring to Figure 1, comprising: a polarizing unit 1 and an analyzing unit 2. Polarizing unit 1 includes: a light source 101, a polarizer 102, and a quarter-wave plate 103, wherein the polarizer 102 is located between the light source 101 and the quarter-wave plate 103. Analyzing unit 2 includes: a diffractive optical element 201, a double-cemented achromatic plano-convex lens 202, a vortex quarter-wave plate (operating wavelength 633nm) 203, an analyzer 204, and a camera 205, which are arranged in sequence. Polarizing unit 1 is used to generate a polarized light beam to be measured.

[0048] The light source 101 is a broadband light source, and the wavelength of the light beam emitted by the light source 101 is 200 nm to 2400 nm.

[0049] The light beam emitted by the light source 101 becomes linearly polarized light after passing through the polarizer 102. The linearly polarized light then passes through the quarter-wave plate 103 to become a polarized light beam to be measured, whose polarization state is dependent on the wavelength. Polarizer 102 and quarter-wave plate 103 are adjusted to generate polarized light beams to be measured with different polarization states. The analyzing unit 2 is used to measure the spectral polarization state of the polarized light beam to be measured.

[0050] In one embodiment, the operating wavelength of the quarter wave plate 103 is 633 nm.

[0051] In one embodiment, the operating wavelength of the vortex quarter-wave plate 203 is 633 nm.

[0052] like Figure 2 As shown, diffractive optical element 201, with the optical axis as its axis of symmetry, disperses light of different wavelengths to different angles. After passing through double-cemented achromatic plano-convex lens 202, the light is collimated into a circular beam. The wavelength of the circular beam increases continuously from the inside to the outside of the circular cross-section of the circular beam, resulting in distinct colors at different radial dimensions, giving the circular beam a "rainbow" appearance.

[0053] The annular beam is spatially polarized by the vortex quarter-wave plate 203 and then analyzed by the analyzer 204. This analysis forms a light intensity modulation pattern with regular variations in radial and angular intensity. The camera 205 captures this light intensity modulation pattern. By analyzing how the intensity of the light intensity modulation pattern varies with azimuth on circles of different radii, the polarization state (Stokes parameter) of the polarized beam to be measured at different wavelengths can be determined.

[0054] The wavelength corresponding to the circle of different pixel radius of the light intensity modulation pattern collected by the camera 205 is calibrated. The diffraction law of the diffractive optical element 201 is given by the following (Equation 1):

[0055]

[0056] In Formula 1, λ is the wavelength of the light beam, θ is the diffraction angle, and D is a constant related to the structure of the diffractive optical element 201. D is related to the period P of the diffractive optical element 201. The larger P is, the larger D is. The sine value of the diffraction angle is proportional to the wavelength, and 1 / D is the proportional coefficient.

[0057] For the 700nm wavelength light in the annular beam, the designed diffraction angle is 9 degrees. Combining the above formula, the constant D = 4474.7nm can be calculated. After the dispersed annular beam is collimated by the double-cemented achromatic plano-convex lens 202, the spatial radius d corresponding to different wavelengths can be calculated using the lens imaging formula:

[0058] d = f·tanθ (Equation 2)

[0059] In Formula 2, f is the focal length of the double cemented achromatic plano-convex lens 202, and the pixel radius r and the spatial radius d of the light intensity modulation pattern collected by the camera 205 are proportional to each other:

[0060] d = k·r (Equation 3)

[0061] In formula 3, k is the scaling factor.

[0062] Space radius d (reference Figure 29 ) is defined as: the radius of different circular rings in the circular beam after being collimated by the double-cemented achromatic plano-convex lens 202.

[0063] Pixel radius r (reference Figure 29 ) is defined as the radius of different circles in the light intensity modulation pattern captured by the camera 205. The pixel radius r is measured in pixels.

[0064] The corresponding relationship between the wavelength of the ring beam and the pixel radius r is obtained from Equations 1, 2, and 3:

[0065]

[0066] The spectropolarimeter satisfies the Stokes-Mueller matrix theory.

[0067]

[0068] In formula 5, S in (λ) is the Stokes vector of the polarized light beam to be measured generated by the polarizing unit 1, is the Mueller matrix of the vortex quarter-wave plate 203, M A is the Mueller matrix of the analyzer 204, is the total Mueller matrix of the analyzing unit 2; is the azimuth angle of the vortex quarter-wave plate in the Cartesian coordinate system, and λ is the wavelength of the light beam.

[0069] The camera 205 can detect the light intensity modulation pattern and process the light intensity modulation pattern to obtain the corresponding light intensity modulation function The light intensity modulation function is the light intensity in the light intensity modulation pattern as the azimuth angle Light intensity modulation function It is proportional to the first term of the Stokes vector of the outgoing light beam emitted from the analyzer 204.

[0070]

[0071] definition is the modulation vector of the polarization analyzer 2. The modulation vector of the polarization analyzer 2 is the first row of the total Mueller matrix of the polarization analyzer 2.

[0072]

[0073] Design of diffractive optical element (DOE): In one embodiment, the operating wavelength of the diffractive optical element is designed to be 400nm-700nm, the diffraction angle of the 700nm light wave is set to 9°, and the size of the plane perpendicular to the optical axis of the diffractive optical element is designed to be 4mm×4mm. The phase distribution of the diffractive optical element is calculated using the commercial software VirtualLab Fusion. Figure 30 and 31 As shown, the phase distribution ( Figure 30 ) is composed of 8000×8000 SiN square prisms with a height H of 1000nm and a period P of 500nm. x "Super Atom" ( Figure 31 ) was introduced. Then, the phase delay of "superatoms" of different sizes a at a wavelength of 700nm was calculated using a commercial finite-difference time-domain (FDTD) calculator, as shown in the following example: Figure 32 Then, 8 "superatoms" with equal phase delays ranging from 0 to 2π were selected as the "superatoms" of the diffractive optical element, as shown in Table 1. Finally, the diffractive optical element was made using photolithography technology. The scanning electron microscope image of the completed diffractive optical element is shown in Figure 33 The dispersion formula of a diffractive optical element can be expressed by the empirical formula sinθ=λ / D, where θ is the diffraction angle and D is a constant related to the structure of the diffractive optical element.

[0074] Table 1 Parameters of the 8 selected “superatoms”

[0075]

[0076] Figure 33 is the top view of the diffractive optical element, Figure 34 This is a 45-degree oblique view of the middle of the diffractive optical element. Figure 35This is a 45-degree oblique view of the bottom of the diffractive optical element.

[0077] Another embodiment of the present invention provides a method for measuring a spectropolarimeter, comprising:

[0078] Step S1: Obtaining the correspondence between the pixel radius and wavelength of the light intensity modulation pattern, including: using filters of the first working wavelength to the Nth working wavelength to be placed between the light source 101 and the polarizer, respectively, using the camera 205 to collect the corresponding first light intensity modulation pattern to the Nth light intensity modulation pattern, where N is an integer greater than or equal to 2; obtaining the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern; based on the data of the first working wavelength to the Nth working wavelength and the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern, fitting to obtain the correspondence between the wavelength and the pixel radius r of the circular light beam

[0079] Step S2: Obtain the modulation vector of the polarization analyzer unit 2 The method includes: setting a polarizing unit 1 to generate 0-degree linear polarized light, the 0-degree linear polarized light is incident on the polarizing unit 2, using a camera 205 to collect a light intensity modulation image and obtain a corresponding light intensity modulation function Set the polarizing unit 1 to generate 45-degree linear polarized light, and the 45-degree linear polarized light is incident on the analyzing unit 2. Use the camera 205 to collect the light intensity modulation image and obtain the corresponding light intensity modulation function. Set the polarizing unit 1 to generate 90-degree linear polarized light, and the 90-degree linear polarized light is incident on the analyzing unit 2. Use the camera 205 to collect the light intensity modulation image and obtain the corresponding light intensity modulation function. Set the polarizer unit 1 to generate left-handed circularly polarized light, and the left-handed circularly polarized light is incident on the analyzer unit 2. Use the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Modulation vector of polarization analyzer 2 It can be calculated by the following formula:

[0080]

[0081] Step S3: The camera 205 collects the test light intensity modulation image corresponding to the polarized light beam to be measured, and obtains the test light intensity modulation function according to the test light intensity modulation image. The test light intensity modulation function is the intensity of the test light intensity modulation image as the azimuth angle increases. Function of change; modulation function and modulation vector according to the test light intensity Get the Stokes vector of the polarized beam to be measured.

[0082] In order to test the actual detection effect of the technical solution proposed by the present invention, according to Figure 1The system structure diagram shown here establishes a fast, wide-spectrum polarization detection optical path. The main equipment used in the specific embodiment is described as follows: the light source used in the system is a Hamamatsu EQ-99X-FC plasma light source, the diffractive optical element is a self-designed diffraction holographic element, the double-cemented achromatic plano-convex lens has a focal length of f = 70 mm, the vortex quarter-wave plate is a VR1-633Q-SP first-order vortex quarter-wave plate produced by LBTEK, the polarizer and analyzer are LPVISE100-A polarizers produced by Thorlabs, the quarter-wave plate is a WPQ10E-633 quarter-wave plate produced by Thorlabs, the camera is a Dhyana95 scientific-grade CMOS camera produced by Tucsen Optoelectronics, and the filter is a Thorlabs FKB-VIS-10 filter with a full width at half maximum (FWHM) of 10 nm.

[0083] In step S1, specifically, a filter with a working wavelength of 450 nm is placed behind the light source, and a first light intensity modulation pattern is acquired by using the camera 205 (refer to Figure 3 ); a filter with a working wavelength of 500nm is placed between the light source and the polarizer, and a second light intensity modulation pattern is obtained by collecting the light using the camera 205 (reference Figure 4 ); Using a filter with a working wavelength of 550nm placed between the light source and the polarizer, the camera 205 is used to capture the third light intensity modulation pattern (reference Figure 5 ); Using a filter with a working wavelength of 600nm placed between the light source and the polarizer, the fourth light intensity modulation pattern (reference Figure 6 ); Using a filter with a working wavelength of 650nm placed between the light source and the polarizer, the fifth light intensity modulation pattern is obtained by collecting the camera 205 (reference Figure 7 ); the pixel radius of the first light intensity modulation pattern is 562 pixels; the pixel radius of the second light intensity modulation pattern is 624 pixels; the pixel radius of the third light intensity modulation pattern is 688 pixels; the pixel radius of the fourth light intensity modulation pattern is 747 pixels; the pixel radius of the fifth light intensity modulation pattern is 808 pixels; using the correspondence between the working wavelength and the pixel radius of the filter, the corresponding relationship between the wavelength and the pixel radius is fitted to be λ=4474.7·sin[arctan(0.0001631·r)].

[0084] In step S2, the modulation vector of the polarization analyzer 2 is obtained. The process includes: setting a polarizing unit 1 to generate 0-degree linear polarized light, the 0-degree linear polarized light is incident on the analyzing unit 2, and collecting the light intensity modulated image (reference Figure 8) and obtain the corresponding light intensity modulation function Set the polarizing unit 1 to generate 45-degree linear polarized light, and the 45-degree linear polarized light is incident on the polarizing unit 2. Use the camera 205 to collect the light intensity modulation image (reference Figure 9 ) and obtain the corresponding light intensity modulation function Set the polarizing unit 1 to generate 90-degree linear polarized light, and the 90-degree linear polarized light is incident on the polarizing unit 2. Use the camera 205 to collect the light intensity modulation image (reference Figure 10 ) and obtain the corresponding light intensity modulation function Set the polarizing unit 1 to generate left-handed circularly polarized light, and the left-handed circularly polarized light is incident on the analyzing unit 2. The light intensity modulation image is collected by the camera (refer to Figure 11 ) and obtain the corresponding light intensity modulation function Modulation vector of polarization analyzer 2 It can be calculated by the following formula:

[0085] Further, yes Perform normalization processing.

[0086] Polarization state measurement: arbitrarily adjust the transmission axis direction of the polarizer and the fast axis direction of the quarter wave plate to produce two polarization states to be measured that do not change with wavelength and two polarization states to be measured that change with wavelength. The combinations of the transmission axis direction α of the polarizer and the fast axis direction β of the quarter wave plate in these four states are: (1) α = 5°, β = 5°; (2) α = 85°, β = 85°; (3) α = 40°, β = 5°; (4) α = 43°, β = 85°. The light intensity modulation images collected by the camera in the four states are as follows: Figures 16 to 19 shown.

[0087] Taking the measurement of the spectral polarization state under the conditions of α=43° and β=85° as an example, the specific measurement process is demonstrated. Figure 19 The light intensity modulation image shown in FIG is processed to obtain the light intensity modulation function of the light intensity at each position with a pixel radius of 496 pixels to 877 pixels (wavelength 400 nm to 700 nm) as a function of azimuth angle. Figure 20 The light intensity modulation functions at 11 wavelengths are shown.

[0088] The spectral Stokes parameters can be obtained by processing the light intensity modulation function. The results are as follows: Figure 21 As shown, the error between the measured results and the theoretical value is as follows Figure 22As shown in the figure, the maximum measurement errors (MMEs) of the Stokes parameters S1, S2, and S3 at 382 wavelengths in the range of 400nm to 700nm are 0.015, 0.016, and 0.012, respectively, and the root mean square errors (RMSs) are 0.004, 0.004, and 0.004, respectively. The entire image processing process takes only 20ms, demonstrating the accuracy and speed of the spectral Stokes polarimeter proposed in this invention.

[0089] The spectral Stokes parameters of the three states of α = 5°, β = 5°, α = 85°, β = 85° and α = 40°, β = 5° were further measured. The measurement results and errors are shown in the table below. Figures 23 to 28 As shown in the figure, the maximum measurement errors (MME) of the Stokes parameters S1, S2, and S3 under the three conditions are less than 0.013, 0.033, and 0.037, respectively, and the root mean square errors (RMS) are less than 0.005, 0.008, and 0.014, respectively, further demonstrating the accuracy of the spectral Stokes polarimeter proposed in this invention.

[0090] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A spectropolarimeter, characterized in that: include: A polarizing unit, the polarizing unit is used to generate a polarized light beam to be measured, the polarizing unit comprising: a light source, a polarizer and a quarter wave plate arranged in sequence, the polarizer being located between the light source and the quarter wave plate; The polarization analyzer unit includes: a diffractive optical element, a double-cemented achromatic plano-convex lens, a vortex 1 / 4 wave plate, an analyzer and a camera arranged in sequence; the diffractive optical element uses the optical axis as the axis of symmetry, disperses light of different wavelengths to different angles, and collimates the light into a circular beam after passing through the double-cemented achromatic plano-convex lens. The wavelength of the circular beam increases continuously from the inside to the outside of the circular cross-section of the circular beam.

2. A method for measuring a spectropolarimeter, using the spectropolarimeter according to claim 1, characterized in that: include: Step S1: Obtaining the correspondence between the pixel radius and wavelength of the light intensity modulation pattern, including: using filters of the first working wavelength to the Nth working wavelength to be placed between the light source and the polarizer respectively, using a camera to respectively capture the corresponding first light intensity modulation pattern to the Nth light intensity modulation pattern, where N is an integer greater than or equal to 2; obtaining the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern; based on the data of the first working wavelength to the Nth working wavelength and the pixel radius of the first light intensity modulation pattern to the Nth light intensity modulation pattern, fitting to obtain the correspondence between the wavelength and the pixel radius r of the circular light beam Where D is a constant related to the structure of the diffractive optical element, k is the scale factor, and f is the focal length of the doublet achromatic plano-convex lens; Step S2: Get the modulation vector of the polarization analyzer Including: setting the polarizing unit to generate 0 degree linear polarized light, 0 degree linear polarized light incident on the polarization analyzer unit, using the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate 45-degree linear polarized light, and the 45-degree linear polarized light is incident on the analyzer unit. Use the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate 90-degree linear polarized light, and the 90-degree linear polarized light is incident on the analyzer unit. Use the camera to collect the light intensity modulation image and obtain the corresponding light intensity modulation function Set the polarizing unit to generate left-handed circularly polarized light, and the left-handed circularly polarized light is incident on the analyzer unit. Use the camera to capture the light intensity modulation image and obtain the corresponding light intensity modulation function Modulation vector of the polarization analyzer It can be calculated by the following formula: Step S3: The camera collects the test light intensity modulation image corresponding to the polarized light beam to be measured, and obtains the test light intensity modulation function according to the test light intensity modulation image. The test light intensity modulation function is the intensity of the test light intensity modulation image as the azimuth angle increases. Function of change; according to the test light intensity modulation function and modulation vector Get the Stokes vector of the polarized beam to be measured.

Images