WO2015101352A1 - 光的偏振态调制、检测装置及检测方法 - Google Patents

光的偏振态调制、检测装置及检测方法 Download PDF

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Publication number
WO2015101352A1
WO2015101352A1 PCT/CN2015/070146 CN2015070146W WO2015101352A1 WO 2015101352 A1 WO2015101352 A1 WO 2015101352A1 CN 2015070146 W CN2015070146 W CN 2015070146W WO 2015101352 A1 WO2015101352 A1 WO 2015101352A1
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polarization
light
lens
modulation
polarization state
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PCT/CN2015/070146
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English (en)
French (fr)
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马辉
常金涛
曾楠
何永红
廖然
孙树清
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清华大学深圳研究生院
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Priority to EP15733176.0A priority Critical patent/EP3093636B1/en
Publication of WO2015101352A1 publication Critical patent/WO2015101352A1/zh
Priority to US15/202,717 priority patent/US9976906B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J4/00—Measuring polarisation of light
    • G01J4/04—Polarimeters using electric detection means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J4/00—Measuring polarisation of light
    • G01J4/02—Polarimeters of separated-field type; Polarimeters of half-shadow type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties

Definitions

  • the present invention relates to a polarization state modulation device for light and a polarization state detection device for light, and more particularly to a modulation device capable of modulating a polarization state in a three-dimensional space to produce a spatially distributed polarization vector vortex field, and capable of real-time high speed
  • a polarization state detecting device that measures light of all Stokes vector parameters, and a detection method thereof.
  • Electromagnetic waves are transverse waves, and the polarization of light is one of the most important basic properties of light.
  • the polarization state of light is an important parameter.
  • detecting light of a specific polarization state can effectively identify a target.
  • polarization imaging can improve image resolution and provide pathological change information.
  • materials science polarized light can be used to measure a film. Parameters such as thickness and refractive index.
  • the Stokes vector is a general concept for characterizing the polarization state of light.
  • Light of any polarization including linearly polarized light, circularly polarized light, elliptically polarized light, and partially polarized light, can be used to represent it.
  • the measurement of the Stokes vector of light requires measuring the intensity of light after passing through a variety of ( ⁇ 4) different polarization elements.
  • various types of polarization detection devices for light have been invented at home and abroad in order to achieve accurate and rapid measurement.
  • the polarization detection device of light is classified into two types: time measurement and simultaneity measurement.
  • the initial polarization detecting device of light is composed of a rotating crystal wave plate and a polarizing plate, and has a simple structure and a mature theory.
  • the rotation of the wave plate or the polarizing plate needs to be performed by at least four measurements by manpower or motor, and cannot meet the requirements of rapid measurement.
  • Another time-dependent polarization detection device uses a liquid crystal wave plate (or electro-optical crystal) instead of a conventional crystal wave plate. It uses a modulation voltage to quickly change the phase delay. Although the measurement time is reduced, some fast measurements are still not satisfied. Demand. Moreover, such a polarization detecting device of light often requires two or more liquid crystal (or electro-optic crystal) modulators at a high cost.
  • the simultaneous detection device of the polarization state is of great significance.
  • the polarization state detecting device of the simultaneous light is realized by the method of pre-wavelength and sub-amplitude.
  • a pre-wavelength device often requires at least four independent micro-optical components to be placed in the optical path, and then the signals corresponding to each component are detected one by one.
  • Split amplitude device Multi-beam splitting prisms are used to divide one beam into more than four channels, each design is different, and finally the signal of each channel is detected.
  • the pre-wavelength device has higher requirements for the micromachining process. There are many components of the amplitude-dividing device, which are often bulky and costly. Moreover, each device often corresponds to various measurement methods, and the calibration work is complicated.
  • the existing polarization detecting device of light has more or less problems such as simultaneity, cost, stability, calibration difficulty and the like.
  • a new light polarization detection device is urgently needed.
  • spatially distributed polarization vector vortex fields have many important uses, including multi-channel optical information transmission for polarization remote sensing measurements and free space, for singular optics research, multi-channel polarization illumination, and Analysis, used to measure the optical axis direction of the crystal in a single measurement.
  • multi-channel optical information transmission for polarization remote sensing measurements and free space
  • multi-channel polarization illumination and Analysis, used to measure the optical axis direction of the crystal in a single measurement.
  • the present invention provides a polarization detecting device for light, comprising a housing, a polarizing plate sequentially disposed on the optical path, an imaging lens, a CCD, and a data processing device and a data transmission line connected between the CCD and the data processing device.
  • the polarizing plate, the imaging lens and the CCD are at least partially encapsulated in the outer casing, and further characterized by: further comprising a lens having a variable birefringence characteristic, wherein the lens having the birefringence characteristic can receive the incident light and emit the emitted light. The light generates a phase space of the light field and then enters the polarizing plate.
  • the light of different phases undergoes polarization interference through the polarizing plate to generate an interference pattern.
  • the interference fringe is projected on the CCD and recorded and transmitted to the data processing device.
  • the data processing device is different according to different The interference state of the different incident light corresponding to the shape of the interference pattern, the polarization state of the incident light is calculated;
  • the lens having the variable birefringence characteristic means a device having a certain phase retardation distribution, so that the lens having the birefringence characteristic is Means a device having a spatial phase retardation distribution with a certain birefringence parameter, the birefringence parameter including And the values of the refractive optical axis direction.
  • the invention also provides a light polarization detecting method, which comprises the following steps: A, the light beam to be measured enters the instrument inlet, the incident light has a certain polarization state; B, the incident light enters the variable birefringence characteristic.
  • the lens causes the spatial phase adjustment of the light field; C.
  • the light emitted from the lens having the birefringence characteristic enters the polarizing plate, and the light of different phases undergoes polarization interference through the polarizing plate to generate an interference pattern;
  • D the light passes through The lens enters the CCD, and the interference fringes are projected on the CCD; E.
  • the polarization state of the incident light is calculated according to the polarization state of different incident light shapes according to different interference pattern shapes.
  • the present invention also includes a polarization state modulation device for light, comprising a polarizing plate sequentially disposed on an optical path and a lens having a variable birefringence characteristic; and the lens having a variable birefringence property can be in a three-dimensional space with respect to a polarization state Modulating to produce a spatially distributed polarization vector vortex field;
  • the lens having a variable birefringence characteristic refers to a device having a spatial phase retardation distribution with a certain birefringence parameter, the birefringence parameter including a birefringence value and an optical axis direction.
  • the inventors have proposed that the above technical solution is based on the fact that the inventors observed in the experiment that the polarized light changes its original polarization state after passing through a self-focusing lens or other material having a birefringence index. In the case of a self-focusing lens, the change is similar.
  • the effect of many annular microwave plate arrays the phase delay of these micro wave plates is distributed between 0-180 degrees, and the birefringent fast axis direction is distributed between -90-90 degrees, which can traverse all possible wave plates. .
  • the polarized light passes through different phase retardation and wave plates in the optical axis direction, and then polarized interference occurs after passing through the polarizing plate, and various light intensity patterns are formed on the CCD. These patterns are in one-to-one correspondence with the incident polarization states.
  • the present invention can utilize different patterns to determine different incident polarization states, or to characterize different polarization states from different pattern extraction parameters.
  • the above-described polarization state detecting device based on light having a birefringent material of the present invention has the following advantages: first, it can meet the requirements of simultaneity measurement; second, it basically does not require mechanical rotation, and does not need to electrically modulate the phase optical element, without Excessive amplitude or pre-wavelength device, which effectively reduces the cost, compact and portable, can be easily applied to related systems, and has strong compatibility; third, it adopts static structure, stable performance and simple use; fourth, can Achieve high system-level accuracy, and the initial calibration of the system is fast and accurate.
  • the polarization detecting device of the light of the invention can be widely applied to various scientific research occasions and industrial applications involving the detection of polarization state of light, and can be specifically used for measuring polarization detectors, ellipsometers and Mueller matrix of various light. Instrument and polarization remote sensing device, etc.
  • the optical polarization modulation device of the invention has the characteristics that the modulation aperture is continuous everywhere and the modulation type is richly changed, and has significant performance advantages and price advantages compared with other polarization modulation devices prepared by micro-nano processing on the market.
  • Fig. 1a is a schematic view of imaging of a self-focusing lens (gray scale indicates that the birefringence is large in black and white is small).
  • Fig. 1b is a schematic cross-sectional view of a self-focusing lens (the gray scale indicates that the birefringence is large in black and white is small).
  • FIG. 2 is a schematic diagram of a polarization state detecting device for light of Embodiment 1 of the present invention.
  • 3a, 3b are the phase delay sizes of the self-focusing lens of Embodiment 1 respectively (the gray level indicates the phase delay)
  • the size is black, the white is small (0-180 degrees), and the birefringence is fast axis (-90-90 degrees).
  • Example 4 is a schematic view showing the light intensity on the CCD measured in Example 1 of the present invention.
  • Fig. 5 is a view showing a Stokes vector of incident light which is derived from a light intensity map in a certain case of the polarizer of the first embodiment of the present invention.
  • Figure 6 is a schematic flow chart of Embodiment 1 of the present invention.
  • Fig. 7 is a schematic diagram showing the distribution of polarization states of horizontally polarized light modulated by a GRIN lens in a certain section.
  • Fig. 8 is a view showing the optical path of polarization modulation in the second embodiment of the invention.
  • 9a-d are light intensity diagrams of the polarization modulation corresponding to FIG. 8 for different detections (0 degrees, 45 degrees, 90 degrees, and 135 degrees first polarization states).
  • Fig. 10 is a view showing the optical path of polarization modulation of the third embodiment of the invention.
  • 11a-d are light intensity diagrams of the polarization modulation corresponding to FIG. 10 for different detections (0 degrees, 45 degrees, 90 degrees, and 135 degrees prior polarization states).
  • Fig. 12 is a view showing the optical path of polarization modulation of the fourth embodiment of the invention.
  • 13a-d are light intensity diagrams of the polarization modulation corresponding to FIG. 12 for different detections (0 degrees, 45 degrees, 90 degrees, and 135 degrees first polarization states).
  • 14a-d are light intensity diagrams 2 of the polarization modulation corresponding to FIG. 12 for different detections (0 degrees, 45 degrees, 90 degrees, and 135 degrees first polarization states), wherein the wave plates used are different from those of FIG.
  • This patent proposes to use a GRIN lens as a polarization state modulation device for light to achieve modulation and demodulation of the polarization state, or to use the GRIN lens as a "biasing" and “detection bias” optical component.
  • This embodiment is a polarization state detecting device for explaining light using a self-focusing lens and a detecting method thereof.
  • a self-focusing lens also known as a gradient-index lens, refers to a cylindrical optical lens whose refractive index distribution is gradually tapered. With focus and imaging capabilities.
  • the self-focusing lens is different from the ordinary lens in that the self-focusing lens material can refract light transmitted in the axial direction and gradually reduce the distribution of the refractive index in the radial direction, thereby realizing that the emitted light is smooth and continuous. Converging to a point.
  • a schematic view of a side cross-section of a self-focusing lens is shown in Fig. 1a, wherein AB is an object and A'B' is an image.
  • the birefringence distribution of the self-focusing lens used in this example is different from the refractive index distribution, and the size of the birefringence gradually increases in the radial direction (the gradation increases from the center to the peripheral gradation in the figure), and the fast axis direction 10 follows the circular direction of the self-focusing lens.
  • the gray scale in the figure indicates the change of its birefringence, and the deeper the color, the larger the birefringence.
  • This embodiment is based on a self-focusing lens to construct a simultaneous polarized Stokes parameter detector (ie, one of the polarization detecting devices of the light of the present invention), as shown in FIG. 2, including a housing, and self-focusing.
  • Lens 1, polarizer P which is a polarizing plate of a fixed polarization angle
  • imaging lens L area array charge coupled device CCD
  • data transmission line electronic computer
  • data processing, analysis, and result display software The self-focusing lens 1, the polarizing plate P, the imaging lens L and the area array charge coupled device CCD are enclosed in a casing.
  • the self-focusing lens we use has a length of the order of centimeters.
  • the entire set of polarization detection devices can achieve a length of about 6 cm or less, a diameter of 1.5 mm or less, and portability and compatibility.
  • the memory or the single chip can also be packaged in the polarization detecting device of the light, and can work independently from the electronic computer.
  • 2 is an optical path diagram used in the embodiment. We adjust the optical path so that the CCD is located on the corresponding image plane of the front end surface of the self-focusing lens, wherein AB is an object, corresponding to the front end surface of the self-focusing lens, and A'B' is a self-focusing lens. In the imaging, A"B" is the imaging in the CCD.
  • the incident light has a certain polarization state, that is, the intensity and phase in the x direction and the y direction;
  • the incident light enters the self-focusing lens, and the phase space distribution of the light field is generated;
  • the light emitted from the self-focusing lens enters the polarizing plate, and the light of different phases undergoes polarization interference through the polarizing plate to generate an interference pattern;
  • the light enters the CCD through the lens, and the interference fringes are projected on the CCD and recorded;
  • Different interference pattern shapes correspond to different polarization states of incident light, that is, the polarization state of the incident light and the pattern of the CCD correspond one-to-one.
  • the one-to-one correspondence can be established by a calculation program, and the polarization state of the incident light can be calculated and saved by a specific pattern;
  • the Bangka ball and the corresponding ellipse parameter representing the polarization state are displayed on the user interface to visually display the result of the polarization measurement.
  • the incident light of different polarization states to be measured is projected onto the CCD after passing through the self-focusing lens and the polarizing plate. During this process, the change in polarization state is:
  • S in is the polarization state of the incident light
  • S out is the polarization state of the outgoing light on the CCD surface
  • M p is the Mueller matrix of the polarizing plate
  • M GRIN is the Mueller matrix of the self-focusing lens.
  • the final signal from the CCD detection is the intensity signal of the light, which is only related to the first line of the Mueller matrix of the polarizer.
  • Px and py are the extinction ratio of the outgoing light and the incident light in the minimum direction and the maximum direction of the polarizing plate extinction, and tp is the azimuth angle of the minimum extinction direction of the polarizing plate.
  • Figure 3a is the phase retardation of the self-focusing lens and Figure 3b is the birefringent fast axis direction.
  • the range of phase delay is 0-180 degrees, and the range of fast axis angle is -90 degrees to 90 degrees, which is the result of Muller matrix measurement.
  • the birefringence distribution of the autofocus lens is circularly symmetric.
  • the polarization properties of different positions in the aperture of the self-focusing lens are different, that is, the Mueller matrix is different.
  • the Mueller matrix of the nth sub-lens is:
  • ⁇ n and ⁇ n are the birefringent fast axis azimuth and phase delay corresponding to the nth sub-lens, respectively.
  • M P does not need to be measured and can be used directly.
  • M GRIN 's Mueller matrix was previously experimentally measured, and the experimentally obtained Muller matrix of the self-focusing lens can be used to derive the birefringence experiment results of Figure 3b.
  • the above M GRIN n is the interpretation of the experimentally obtained M GRIN in an ideal form.
  • the incident beam can be assumed to be an n-beam sub-beam, and the self-focusing lens is composed of n tiny micro-lenses of different phase delay magnitudes and optical axis directions. Accordingly, the light intensity value of n pixels is obtained on the CCD, and the n-th pixel
  • the formula for calculating the light intensity is:
  • a T is the transposition of A
  • (A T A) -1 is the inverse of (A T A).
  • I is the intensity value of each point on the CCD
  • A is a 4Xn matrix
  • a p -1 is the generalized inverse matrix of A, which are all known quantities when calculating the polarization state S in .
  • S in has four unknowns
  • n light intensity values are obtained on the CCD
  • n corresponds to the number of imaging pixels on the CCD, which is often large.
  • This is equivalent to solving a linear system of equations, the number of unknowns is 4, and the number of equations is n.
  • This is an overdetermined system of equations.
  • the process of solving can be done by means of a pseudo-inverse algorithm, which automatically obtains the optimal solution using least squares.
  • Theoretical calculations show that the measurement accuracy increases with the increase of n.
  • EWV equally weighted variance
  • W + is the pseudo inverse of W
  • Tr is the trace of the matrix
  • condition number condition number(k(A)) of another parameter matrix to find the optimal instrument matrix.
  • the minimum condition number of the matrix is 1, and the closer to 1, the more accurate the solution of the linear equations.
  • the polarization state of the incident light is obtained.
  • the collimated LED light is used to add a narrow-band filter (center wavelength 633 nm, half-height width 3 nm) to obtain quasi-monochromatic parallel light, followed by a polarized plate with a bias and a quarter-wave plate with phase adjustment.
  • a narrow-band filter center wavelength 633 nm, half-height width 3 nm
  • a polarized plate with a bias and a quarter-wave plate with phase adjustment we fixed the polarizer at an angle and rotated the quarter-wave plate.
  • the measured light intensity on the CCD is shown in Figure 4 ( Figure 4 is the polarization plate of the polarizer fixed, wave The intensity map on the corresponding CCD when the sheet is rotated 180 degrees).
  • Figure 4 shows a total of 18 graphs a to r in the 180 degree rotation of the wave plate as a schematic diagram, and each image selects a total of n pixels, and the light intensity of the nth pixel is S outn0 .
  • Figure 5 is the polarization states s in1 , s in2 , s in3 of the incident light calculated by the above algorithm by the intensity map on the CCD, and they all normalize s in0 .
  • Figure 5 is a Stokes vector of the incident light from the light intensity map of the corresponding 54 sets of CCDs when the polarizer of the polarizer is fixed and the wave plate is rotated by 180 degrees.
  • this embodiment can achieve accurate measurement of the polarization state. Its main advantages are:
  • the initial calibration of the system is fast and accurate, and the parameter selection can be optimized by a built-in algorithm, which greatly improves the ease of use and reduces the labor spent by the operator in instrument debugging.
  • the system has the problems of simultaneous polarization state, low cost, stability, universality, ease of use, etc., and has simple structure, stable performance and low cost. Can be used in a variety of complex situations.
  • the description of the above method is limited to the incident light of a uniform polarization state, and therefore is a point measurement, which has a requirement that the polarization state of the incident light in the aperture of the self-focusing lens is uniform.
  • the measurement of the surface imaging can also be achieved by a self-focusing lens.
  • the diameter of the self-focusing lens can be as small as 0.1 mm, so that a large number of self-focusing lenses can be used to form mXn, each of which is measured at a point corresponding to a point, and finally a spatial polarization state distribution of mXn size is obtained.
  • phase distribution is the distribution shown in FIG. 3a.
  • This distribution covers a phase delay of 0-180 degrees and a fast axis angle of -90-90 degrees.
  • the distribution traverses all possible planar birefringences with maximum error tolerance.
  • the method is not limited to a self-focusing lens, but is generally applicable to all devices having a certain phase delay distribution because the polarization state detecting device of light of any phase delay device can be handled universally using the method of the present invention. As long as the Mueller matrix of any phase delay device is known.
  • the present invention not only protects the polarization detecting means of the GRIN lens light, but also protects the polarization detecting means of the light of all the birefringent materials.
  • the above-described polarization detecting means for light can be applied to various ellipsometers, Mueller matrix measuring devices and polarization remote sensing devices, and the application of the self-focusing device to the above three aspects or the like is also within the scope of the present invention.
  • the above embodiment 1 and its variant embodiment use a GRIN lens to demodulate the polarization state.
  • the polarization state can also be modulated using a GRIN lens. That is, the GRIN lens can be used to modulate the polarization state in a three-dimensional space to produce a spatially distributed polarization vector vortex field. This will be explained in the following Examples 2-5.
  • Modulation of the polarization state in three dimensions using a GRIN lens can produce spatial distribution A polarization vector vortex field that contains any possible complete polarization state, ie, simultaneously produces all polarization states of the Bangka ball surface.
  • different phase modulations can be generated using different offset GRIN lenses during the production process.
  • ⁇ n and ⁇ n vary from 0 to 180 degrees, so S out can traverse all polarization states.
  • the positive sign of the above formula represents right-handed elliptically polarized light, and the negative sign carries left-handed elliptically polarized light.
  • the value is related to the values of ⁇ n and ⁇ n , that is, the proportion of circular polarization at different positions is different.
  • the figure shows a distribution map of the polarization state S out of the emitted light when the polarization state S in incident light is horizontally incident polarized light, that is, the polarized light modulated by the GRIN lens is in a certain one.
  • a schematic view of the cross section which can be seen to contain any linearly polarized light, left and right circularly polarized light and any possible elliptically polarized light.
  • the GRIN lens is capable of converting a single horizontally polarized light into any possible fully polarized light, such as linearly polarized light in any direction in the circumferential region of the 180 degree phase delay in the Figure.
  • This one-division method can be used to increase the bandwidth of optical communication;
  • the polarization vector vortex field generated by GRIN lens which contains many optical polarization singular points, can be used for singular optics research, and can also be used for optical orbital and optical orbital angular momentum research. ;
  • the simultaneous spatial polarization device which can be used to measure the optical axis direction of the crystal in a single time, that is, the GRIN lens is used to illuminate the crystal to be tested, and the polarized light received at different positions of the crystal is different, considering different positions.
  • the detection result can determine the optical axis direction of the crystal in a single time;
  • the simultaneous spatial polarizing device combined with the simultaneous polarization detecting device, that is, the GRIN lens polarimeter, the single-Muller matrix measurement of the sample can be realized.
  • the Light Source is a light source.
  • the polarizer (or other direction, here in the horizontal direction) in the horizontal 0 degree direction enters the GRIN lens GRIN1 to complete the polarization space. modulation.
  • the latter module is an analyzer consisting of four polarizers P2 with polarization angles of 0, 45, 90 and 135 degrees, and the CCD is an imaging detector.
  • the polarizer is used as a polarization analyzer, and the wave plates with different phase delays are used to assist in optical phase delay modulation.
  • the Light Path is shown in Figure 10.
  • the Light Source is the light source. After collimating through the lens group L, it passes through the horizontal 0 degree polarizer (or other direction, here in the horizontal direction) and then enters GRIN lens GRIN1, and GRIN lens GRIN2. , complete the polarization state spatial modulation.
  • the latter module is an analyzer consisting of four polarizers P2 with polarization angles of 0, 45, 90 and 135 degrees, and the CCD is an imaging detector.
  • the Light Source is the light source. After collimating through the lens group L, it passes through the polarizer in the horizontal 0 degree direction (or other direction, here in the horizontal direction as an example) and then enters the GRIN lens GRIN1, and then passes through R ( In this example, R is a quarter-wave plate), enters the GRIN lens GRIN2, and completes the polarization spatial modulation.
  • the latter module is an analyzer consisting of four polarizers P2 with polarization angles of 0, 45, 90 and 135 degrees, and the CCD is an imaging detector.
  • the Light path is still as shown in Fig. 12.
  • the Light Source is the light source.
  • the polarizer or other direction, here in the horizontal direction
  • the GRIN lens GRIN1 After collimating through the lens group L, the polarizer (or other direction, here in the horizontal direction) in the horizontal 0 degree direction enters the GRIN lens GRIN1, and then passes through the R. (However, unlike in the fourth embodiment, R is a half-wave plate in this example), the GRIN lens GRIN2 is entered to complete the polarization spatial modulation.
  • the latter module is an analyzer consisting of four polarizers P2 with polarization angles of 0, 45, 90 and 135 degrees, and the CCD is an imaging detector.
  • Embodiments 2-5 above describe four different embodiments of spatial polarization modulation using GRIN lenses, which can produce more different spatial polarization modulations using more or different lengths of GRIN lenses and different wave plates. It can't be exhausted here.
  • GRIN lens As a spatial polarization modulation device, GRIN lens has the characteristics of continuous modulation aperture and rich variety of modulation types. Compared with other polarization modulation devices based on micro-nano processing, it has significant performance advantages and price advantages.

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Abstract

一种偏振态检测装置，检测方法及一种光的偏振态调制方法，偏振态检测装置包括一具有变双折射率特性的自聚焦透镜（1），作为光学相位延迟调制器；一偏振片，作为偏振态分析器；若干普通透镜和一CCD，作为成像器件；一数据处理和显示单元。偏振态检测装置利用自聚焦透镜（1）等变双折射率光学元件广泛具有的特殊双折射分布，通过CCD单帧成像即可得到待测光的斯托克斯向量，能够快速准确地确定光的偏振态。偏振态检测装置构造简单，成本较低，不含有任何运动部件和电调制设备，是完全静态的全斯托克斯向量偏振态检测装置。光的偏振态调制装置包括一具有变双折射率特性的自聚焦透镜（1）。调制方法在调制孔径内各处连续，调制种类变化丰富，成本低廉。

Description

光的偏振态调制、检测装置及检测方法 技术领域
本发明涉及一种光的偏振态调制装置和光的偏振态检测装置，尤其涉及一种能够对偏振态在三维空间内进行调制产生具有空间分布的偏振矢量涡旋场的调制装置，以及能够实时高速测量全部斯托克斯向量参数的光的偏振态检测装置，以及其检测方法。
技术背景
电磁波是横波，而光的偏振态是光最重要的儿个基本属性之一。在各个光学领域中，光的偏振态都是重要的参数。例如在遥感技术中，检测特定偏振态的光能够有效识别目标物，在生物医学光子学中，偏振成像可以提高影像的分辨率，提供病理变化信息，在材料学中，利用偏振光可以测量薄膜的厚度和折射率等参数。
要想确定一束光的所有偏振信息，我们需要测量这束光的斯托克斯向量。斯托克斯向量是表征光的偏振态的通用概念，任意偏振态的光，包括线偏振光，圆偏振光，椭圆偏振光和部分偏振光，都可以用它来表示。
光的斯托克斯向量的测量需要分别测量光经过多种(≥4种)不同偏振元件后的光强。在过去的几十年间，国内外发明了各式光的偏振态检测装置，目的就是实现准确而快速的测量。总体来说，光的偏振态检测装置分为含时性测量和同时性测量两类。最初的光的偏振态检测装置一股由转动的晶体波片和偏振片组成，它结构简单，理论成熟。但波片或偏振片的转动需要依靠人力或电机，进行至少四次测量，无法满足快速测量的要求。另外，波片的转动会造成光束漂移，整个***是非静态的，增加了测量的不确定性。另一种含时的光的偏振态检测装置使用液晶波片(或电光晶体)代替传统晶体波片，它利用调制电压快速改变相位延迟，虽然降低了测量时间，但仍然不能满足某些快速测量的需求。并且，这种光的偏振态检测装置往往需要两个或者更多的液晶(或电光晶体)调制器，成本较高。
因此，偏振态的同时性检测装置具有重要意义。同时性光的偏振态检测装置多是利用分波前和分振幅的方法实现的。分波前装置往往需要设计至少四个独立的微型光学元件置于光路中，然后一一探测每个元件对应的信号。而分振幅装置 多使用分光棱镜将一路光束分成4路以上，每路设计不同，最后探测每路的信号。分波前装置对微加工工艺的要求较高。分振幅装置元件较多，往往体积较大，成本较高。而且每种装置往往对应各式不同测量方法，校准工作复杂。
由上面的陈述可知，现有的光的偏振态检测装置或多或少存在同时性、成本、稳定性、校准难度等问题。新的光的偏振态检测装置亟待推出。
另一方面，具有空间分布的偏振矢量涡旋场具有很多重要用途，包括用于偏振遥感测量和自由空间的多通道光信息传输、用于奇点光学(singular optics)研究、多通道偏振照明和分析、用于单次测量晶体的光轴方向等。目前，市场上存在一些通过薄膜加工等工艺制备的二维空间相位调制片，价格较为昂贵，并且具有调制孔径各处不连续，调制种类变化不够丰富的缺点。
发明内容
本发明的目的在于提供一种光的偏振态调制、检测装置及检测方法，满足同时性测量的要求，并提供一种具有性能和价格优势的光的偏振态检调制装置。
为此，本发明提出一种光的偏振态检测装置，包括外壳，依次设置于光路上的偏振片、成像透镜、CCD，以及数据处理装置和连接于CCD与数据处理装置之间的数据传输线，其中偏振片、成像透镜和CCD至少部分封装在外壳内，其特征是：还包括具有变双折射率特性的透镜，所述具有变双折射率特性的透镜可接收被测入射光并使出射的光线产生光场的相位空间分布后进入偏振片，不同相位的光线经过偏振片发生偏振干涉，产生干涉花样，干涉条纹投射在CCD上记录下来并传输到数据处理装置；所述数据处理装置根据不同的干涉花样形状对应的不同的入射光的偏振态，计算出入射光的偏振态；所述具有变双折射率特性的透镜是指有一定相位延迟分布的器件所谓具有变双折射率特性的透镜是指有一定双折射参数有空间相位延迟分布的器件，所述双折射参数包括双折射值和光轴方向。
本发明还提出一种光偏振检测方法，其特征是：包括如下步骤：A、使得待测光束进入仪器进光口，入射光线具有一定的偏振态；B、入射光进入具有变双折射率特性的透镜，使其产生光场的空间相位调节；C、从具有变双折射率特性的透镜出射的光线进入偏振片，不同相位的光线经过偏振片发生偏振干涉，产生干涉花样；D、光线经过透镜进入CCD，干涉条纹投射在CCD上记录下来；E、根据不同的干涉花样形状对应不同的入射光的偏振态检，计算出入射光的偏振态检。
本发明还包括一种光的偏振态调制装置，包括依次设置于光路上的偏振片和具有变双折射率特性的透镜；所述具有变双折射率特性的透镜可对偏振态在三维空间内进行调制，产生具有空间分布的偏振矢量涡旋场；所述具有变双折射率特性的透镜是指有一定双折射参数有空间相位延迟分布的器件，所述双折射参数包括双折射值和光轴方向。
本发明人提出上述技术方案是基于发明人在实验中观测到偏振光经过自聚焦透镜或其他具有变双折射率的材料后会改变原来的偏振态，在自聚焦透镜的情形，这种改变类似于很多环形微小波片阵列的效果，而这些微小波片的相位延迟分布在0-180度之间，同时双折射快轴方向分布在-90-90度之间，能够遍历所有可能的波片。偏振光经过不同的相位延迟和光轴方向的波片，再经过偏振片后会发生偏振干涉现象，进而会在CCD上形成各种不同的光强花样分布。而这些花样和入射的偏振态是一一对应的。本发明可以利用不同的花样确定不同的入射偏振态，或者从不同的花样提取参数表征不同的偏振态。
本发明的上述基于具有变双折射率材料的光的偏振态检测装置具有以下优势：第一，能满足同时性测量的要求；第二，它基本无需机械转动，无需电调制相位光学元件，无需多余的分振幅或分波前器件，从而有效降低了成本，结构紧凑便携，可以很容易应用于相关***中，兼容性强；第三，采用静态结构，性能稳定，使用简单；第四，可以达到很高的***级精度，而且***的初始校准快捷准确。
本发明光的偏振态检测装置可广泛应用于涉及到光的偏振态检测的各种科研场合和工业应用场合，具体可用于制作各种光的偏振态检测器、椭偏仪、穆勒矩阵测量仪和偏振遥感装置等等。
本发明光偏振调制器件具有调制孔径各处连续，调制种类变化丰富的特点，相较于目前市面上其他的基于微纳加工制备的偏振调制器件，具有显著的性能优势和价格优势。
附图说明
图1a是自聚焦透镜成像示意图(灰度表示双折射大小黑色为大，白色为小)。
图1b是自聚焦透镜横截面示意图(灰度表示双折射大小黑色为大，白色为小)。
图2本发明实施例1光的偏振态检测装置示意图。
图3a、3b分别是实施例1自聚焦透镜的相位延迟大小(灰度表示相位延迟 大小黑色为大，白色为小(0-180度))和双折射快轴方向示意图(-90-90度)。
图4是本发明实施例1测量得到的CCD上的光强示意图。
图5是本发明实施例1起偏器的一定情况下的光强图推出的入射光的斯托克斯向量示意图。
图6是本发明实施例1流程示意图。
图7为经过GRIN lens调制后的水平线偏振光在某一个截面的偏振态分布示意图。
图8为发明实施例2偏振调制的光路示意图。
图9a-d为图8对应的偏振调制对于不同检偏(0度你、45度、90度及135度先偏振态检偏)的光强图。
图10为发明实施例3偏振调制的光路示意图。
图11a-d为图10对应的偏振调制对于不同检偏(0度你、45度、90度及135度先偏振态检偏)的光强图。
图12为发明实施例4偏振调制的光路示意图。
图13a-d为图12对应的偏振调制对于不同检偏(0度你、45度、90度及135度先偏振态检偏)的光强图之1。
图14a-d为图12对应的偏振调制对于不同检偏(0度你、45度、90度及135度先偏振态检偏)的光强图之2，其中所用波片与图13不同。
具体实施方式
本专利提出将GRIN lens用作光的偏振态检调制器件，以实现偏振态的调制和解调，或者说，将GRIN lens用作“起偏”和“检偏”光学元件。
实施例1
本实施例是用于说明利用自聚焦透镜的光的偏振态检测装置及其检测方法。
自聚焦透镜(GRIN Lens)又称为梯度变折射率透镜，是指其折射率分布是沿径向渐变的柱状光学透镜。具有聚焦和成像功能。
当光线在空气中传播当遇到不同介质时，由于介质的折射率不同会改变其传播方向。传统的透镜成像是通过控制透镜表面的曲率，利用产生的光程差使光线汇聚成一点。
自聚焦透镜同普通透镜的区别在于，自聚焦透镜材料能够使沿轴向传输的光产生折射，并使折射率的分布沿径向逐渐减小，从而实现出射光线被平滑且连续 的汇聚到一点。如图1a所示为某一自聚焦透镜侧截面成像示意图，其中AB为物，A’B’为像。本例中使用的自聚焦透镜的双折射分布与折射率分布不同，双折射大小沿径向逐渐增加(图中从中心到***灰度逐渐增加)，快轴方向10沿自聚焦透镜的环形方向(如图1b)，图中灰度表示其双折射率的变化，颜色越深的区域其双折射率越大。
本实施例是基于自聚焦透镜构建一种同时性的偏振光斯托克斯参量检测仪(即本发明的光的偏振态检测装置的一种)，如图2所示，包括外壳、自聚焦透镜1、偏振片P(其为一固定偏振角度的偏振片)、成像透镜L、面阵电荷耦合器件CCD、数据传输线、电子计算机，和数据处理、分析、结果显示软件。其中自聚焦透镜1、偏振片P、成像透镜L和面阵电荷耦合器件CCD封装在外壳内。我们使用的自聚焦透镜的长度在厘米量级，整套光的偏振态检测装置的可以做到6厘米左右或者更短的长度，直径为1.5毫米或者更细，便携性和兼容性强。亦可将存储器或单片机封装在光的偏振态检测装置中，可脱离电子计算机独立工作。图2为本实施例使用的光路图，我们调节光路，使得CCD位于自聚焦透镜前端面对应的像平面上，其中AB为物，对应自聚焦透镜前端面，A’B’为自聚焦透镜中的成像，A”B”为在CCD中的成像。
本实施例利用上述检测仪进行偏振检测的测量步骤如下(如图6所示)：
A、使得待测光束进入仪器进光口。入射光线具有一定的偏振态，即x方向和y方向的强度和相位；
B、入射光进入自聚焦透镜，产生了光场的相位空间分布；
C、从自聚焦透镜出射的光线进入偏振片，不同相位的光线经过偏振片发生偏振干涉，产生干涉花样；
D、光线经过透镜进入CCD，干涉条纹投射在CCD上记录下来；
E、不同的干涉花样形状对应不同的入射光的偏振态，即入射光的偏振态和CCD的花样一一对应。通过计算程序可以将这种一一对应的关系建立起来，并可以通过某个特定的花样计算出入射光的偏振态，并保存；
F、还可选择在用户界面将表征偏振态的邦加球和对应的椭圆参数显示出来，从而形象地显示出偏振测量的结果。
上述光的偏振态检测装置方法原理分析说明如下：
使待测不同偏振态的入射光经过自聚焦透镜和偏振片后投射在CCD上。在此过程中，偏振态的变化为：
Sout＝MP·MGRIN·Sm
Sin为入射光的偏振态，Sout为出射光在CCD表面时的偏振态，Mp为偏振片的穆勒矩阵，MGRIN是自聚焦透镜的穆勒矩阵。
CCD探测得到的最终信号是光的强度信号，它只与偏振片的穆勒矩阵的第一行有关。
其中，偏振片穆勒矩阵的第一行为：
Figure PCTCN2015070146-appb-000001
px和py分别为偏振片消光极小方向和极大方向的出射光与入射光消光比，tp为偏振片极小消光方向的方位角。
固定偏振片的通光方向为水平时，上式可简化为：
Figure PCTCN2015070146-appb-000002
我们在实验中发现，自聚焦透镜产生的相位延迟大小和双折射快轴方向如图3a、3b所示：
图3a是自聚焦透镜的相位延迟大小，图3b是双折射快轴方向。相位延迟的范围是0-180度，快轴角度的范围是-90度到90度，这是穆勒矩阵测量得到的结果。
由此图可见，自聚焦透镜的双折射分布是环形对称的。自聚焦透镜口径内不同位置的偏振性质不同，即穆勒矩阵不同。为此，我们将自聚焦透镜划分为n个微小区域，如果每个微小区域足够小，它内部的偏振性质可以认为是相同的。我们称每个微小区域为子透镜，而相应地，入射光束可以划分为n束子光束，每束子光束对应各自的子透镜。第n个子透镜的穆勒矩阵为：
Figure PCTCN2015070146-appb-000003
δn和θn分别为第n个子透镜对应的双折射快轴方位角和相位延迟大小。公式中MP不需要测量，可直接使用。MGRIN的穆勒矩阵是事先通过实验测得的，实验得到的自聚焦透镜的穆勒矩阵可以推演出图3b的双折射实验结果。上面的MGRINn是我们用理想的形式对实验得到的MGRIN进行解释，在实施中，我们同样可以使用测得的自聚焦透镜的穆勒矩阵的各个阵元代替MGRINn进行下面的计算。
前面假设入射光束可假设为n束子光束，自聚焦透镜由n个微小的不同相位延迟大小和光轴方向的微透镜组成，相应地，CCD上会得到n个像素的光强值，第n个像素的光强的计算公式为：
Figure PCTCN2015070146-appb-000004
上式可以写成矩阵形式
I＝A·Sin，
Figure PCTCN2015070146-appb-000005
Figure PCTCN2015070146-appb-000006
Figure PCTCN2015070146-appb-000007
采用伪逆计算公式
Figure PCTCN2015070146-appb-000008
其中，AT为A的转置，(ATA)-1为(ATA)的逆。
最终反推得到入射偏振态
Figure PCTCN2015070146-appb-000009
这里的I为CCD上每点的强度值，A是一个4Xn的矩阵，Ap -1是A的广义逆矩阵，在计算偏振态Sin时它们都是已知量。Sin有四个未知量，CCD上会得到n个光强值，n对应与CCD上的成像像素个数，往往很大。这相当于求解一个线性方程组，未知数的个数为4，方程数为n。这是一个超定方程组，求解的过程可以借助伪逆的算法，它会使用最小二乘法自动获得最优解。理论计算发现，一股地，测量精度会随着n的增加而增加。
我们使用equally weighted variance(EWV)表示***的测量误差容忍度，EWV越小，容忍度越高。
Figure PCTCN2015070146-appb-000010
这里W+为W的伪逆，Tr为求矩阵的迹。
当然，对于n个光强，n个方程，并不是每个都是必须的。
我们同时利用另一个参数矩阵的条件数condition number(k(A))来寻找最优化的仪器矩阵，矩阵的条件数最小为1，越接近1，线性方程组的求解越精确。
k(A)＝||A||||A-1||
Figure PCTCN2015070146-appb-000011
为A的第二类范数。
通过均衡最优化的EWV和条件数，我们可以选取一定相位延迟范围的环形 区域，以保证测量精度。使用公式
Figure PCTCN2015070146-appb-000012
即可得到入射光的偏振态。
Figure PCTCN2015070146-appb-000013
Figure PCTCN2015070146-appb-000014
其中
Figure PCTCN2015070146-appb-000015
本实施例的实验验证：
使用准直的LED光后加入窄带滤波片(中心波长633nm，半高宽3nm)的方法得到准单色平行光，后加入一起偏的偏振片和调节相位的一四分之一波片。在本例中，我们固定偏振片为某一角度，旋转四分之一波片，此时测量得到的CCD上的光强如图4所示(图4是起偏器的偏振片固定，波片转动180度时对应的CCD上的光强图)。图4中显示了波片转动180度中a～r共18幅图作为示意，每幅图选取共n个像素，第n个像素的光强为Soutn0。图5为由CCD上的光强图通过上述算法计算得到的入射光的偏振态sin1，sin2，sin3，他们都对sin0进行了归一化。图5是起偏器的偏振片固定、波片转动180度时对应的54组CCD的光强图推出的入射光的斯托克斯向量，理论的理想曲线：S1、S2、S3，实验结果：方块：接近S1，圆圈：接近S2；三角：接近S3，图5中，横轴是角度θ，单位为度，纵轴是斯托克斯参量归一化的数值。
上述列举了一系列完全偏振光的测量花样和结果，部分偏振光或自然光的结果同样可以实现单次测量。
由此可见，本实施例可以实现偏振状态的准确测量。其主要优点是：
1：单帧图片即可确定入射的偏振态，满足同时性测量的要求；
2：全静态***，无需任何机械转动器件；
3：无需任何电调制相位光学元件(易受温度等外界因素影响，对调制电源要求高)，因此***受电信号的干扰小，误差低，更稳定；
4，无需任何多余的分振幅或分波前器件有效降低成本，结构紧凑便携，可以很容易应用于相关***中，兼容性强；
5，相比目前大部分光的偏振态检测装置，该***的初始校准快捷准确，可通过内置算法一键式优化参数选取，大大提高易用度，降低操作者花费在仪器调试中的劳动。
6，该***具备了偏振态同时性，低成本，稳定性，通用型，易用性等问题，而且结构简单，性能稳定，成本低廉。可用于各种复杂场合。
使用GRIN lens对偏振态进行解调，还有更多的变通实施方式，例如：
1：上述讨论是针对某一特定波长，上述实验结果在中心波长633nm、带宽3nm的LED红光光源下完成，事实上，其他特定波长的分析类似，该光的偏振态检测装置拥有宽广的波长测量范围，只要入射光是窄带光即可。
2：上述方法的描述仅限于均匀偏振态的入射光，因此是点测量，它有一个要求，就是入射光在自聚焦透镜口径内的偏振态是均匀的。但通过自聚焦透镜同样可以实现面成像的测量。自聚焦透镜的直径可以小到0.1mm，因此可以使用大量自聚焦透镜组成mXn的，每个自聚焦透镜对应一个点测量，最终得到mXn大小的空间偏振态分布。
3：本实施例是以自聚焦透镜为例来说明的，其相位分布就是图3a所示的分布，这个分布覆盖了0-180度的相位延迟，-90-90度的快轴角度，这样的分布遍历了所有可能的平面双折射，拥有最大的误差容忍度。但本方法不仅仅限于自聚焦透镜，而是通用于所有有一定相位延迟分布的器件，因为使用本发明的方法可以通用性地处理任意相位延迟器件的光的偏振态检测装置。只要任意相位延迟器件的穆勒矩阵是已知的就行。例如：设计一种薄膜，它也能拥有较大的相位延迟和快轴角度范围，也可以直接使用本文的方法构成偏振测量仪。因此，本发明不仅仅保护GRIN lens光的偏振态检测装置，而且保护所有变双折射材料的光的偏振态检测装置。
4：上述光的偏振态检测装置可使用于各种椭偏仪，穆勒矩阵测量装置和偏振遥感装置中，将自聚焦器件应用于上述三个方面或类似领域，同样属于本发明的范围。
上述实施例1及其变通实施方式是使用GRIN lens对偏振态进行解调。但本发明人发现，还能使用GRIN lens对偏振态进行调制。即：可以使用GRIN lens对偏振态在三维空间内进行调制，产生具有空间分布的偏振矢量涡旋场。下面实施例2-5将对此进行说明。
使用GRIN lens对偏振态在三维空间内进行调制，可以产生具有空间分布的 偏振矢量涡旋场，该涡旋场包含任意可能的完全偏振态，即同时产生邦加球表面所有的偏振态。同时可以在生产过程中使用不同截距的GRIN lens产生不同的相位调制。如前所述，目前，市场上存在一些通过薄膜加工等工艺制备的二维空间相位调制片，价格较为昂贵，而使用GRIN lens作为相位调制器，不仅可以取代目前市场上已有的相位调制片，并做到价格低廉，而且能产生三维的空间调制。
考虑一个实例，当水平线偏振光进入GRIN lens时，出射光的斯托克斯向量为
Figure PCTCN2015070146-appb-000016
θn和δn的取值都在0度到180度之间变化，因此Sout可以遍历所有的偏振态。
偏振角度为
Figure PCTCN2015070146-appb-000017
与θn和δn的取值相关，即不同位置AoP值不同。
圆偏振所占比例为
Figure PCTCN2015070146-appb-000018
上式正号代表右旋椭圆偏振光，负号带包左旋椭圆偏振光。取值与θn和δn的取值相关，即不同位置圆偏振所占比例不同。
如图7所示，图中表示的是入射光的偏振态Sin为水平入射偏振光时，对应出射光的偏振态Sout的分布图，即表示经过GRIN lens调制后的偏振光在某一个截面的示意图，由图可见它包含任意线偏振光，左右旋圆偏振光和任意可能的椭圆偏振光。
具有空间分布的偏振矢量涡旋场的用途包括：
(1)用于偏振遥感测量和自由空间的多通道光信息传输。从图7中可以看到，GRIN lens能够将单一的水平偏振光转化为任意可能的完全偏振光，例如在图中180度相位延迟的圆周区域产生了任意方向的线偏振光。这种一分为多的方式可以用于提高光通信的带宽；
(2)GRIN lens产生的偏振矢量涡旋场，包含很多光学偏振奇点，可用于奇点光学(singular optics)研究，还可用于用于光学轨道和自旋角动量(optical orbital angular momentum)研究；
(3)用于同时性空间起偏装置，可用于多通道偏振照明和分析，即使用GRIN lens照明待测样品，样品的不同位置接收到的偏振光各不相同，可以进行高通量测量：
(4)用于同时性空间起偏装置，可用于单次测量晶体的光轴方向，即使用GRIN lens照明待测晶体，晶体的不同位置接收到的偏振光各不相同，综合考虑不同位置的探测结果可以单次将晶体的光轴方向确定；
(5)用于同时性空间起偏装置，结合同时性检偏装置即GRIN lens偏振计，可实现样品的单次穆勒矩阵测量。
GRIN lens被用作偏振态调制器件的实施例以下举例说明：
实施例2
光路如图8所示，Light Source为光源，经过透镜组L准直后，经过水平0度方向的偏振片(或其他方向，这里以水平方向为例)后进入GRIN lens GRIN1，完成偏振态空间调制。后面的模块为4个偏振角度0度、45度、90度、135度的偏振片P2组成的检偏器，CCD为成像探测器。其中偏振片作为偏振态分析器，相位延迟不同的波片用于辅助进行光学相位延迟调制。
使用图8的偏振调制方案，可以产生某种特定的偏振空间分布形式。为了对偏振分布可视化，我们使用P2转动4个角度记录CCD上的光强图，如图9a、9b、9c、9d所示，依次对应P2为4个偏振角度0度、45度、90度、135度的情形。
实施例3
光路如图10所示，Light Source为光源，经过透镜组L准直后，经过水平0度方向的偏振片(或其他方向，这里以水平方向为例)后进入GRIN lens GRIN1，和GRIN lens GRIN2，完成偏振态空间调制。后面的模块为4个偏振角度0度、45度、90度、135度的偏振片P2组成的检偏器，CCD为成像探测器。
使用图10的偏振调制方案，可以产生某种特定的偏振空间分布形式。为了对偏振分布可视化，我们使用P2转动4个角度记录CCD上的光强图，如图11a、11b、11c、11d所示，依次对应P2为4个偏振角度0度、45度、90度、135度的情形。
实施例4
光路如图12所示，Light Source为光源，经过透镜组L准直后，经过水平0度方向的偏振片(或其他方向，这里以水平方向为例)后进入GRIN lens GRIN1，后经过R(该范例中R为四分之一波片)，进入GRIN lens GRIN2，完成偏振态空间调制。后面的模块为4个偏振角度0度、45度、90度、135度的偏振片P2组成的检偏器，CCD为成像探测器。
使用图12的偏振调制方案，可以产生某种特定的偏振空间分布形式。为了对偏振分布可视化，我们使用P2转动4个角度记录CCD上的光强图，如图13a、13b、13c、13d所示，，依次对应P2为4个偏振角度0度、45度、90度、135度的情形。
实施例5
光路仍如图12所示，Light Source为光源，经过透镜组L准直后，经过水平0度方向的偏振片(或其他方向，这里以水平方向为例)后进入GRIN lens GRIN1，后经过R(但与实施例4不同的是，本例中R为二分之一波片)，进入GRIN lens GRIN2，完成偏振态空间调制。后面的模块为4个偏振角度0度、45度、90度、135度的偏振片P2组成的检偏器，CCD为成像探测器。
使用图12的偏振调制方案，可以产生某种特定的偏振空间分布形式。为了 对偏振分布可视化，我们使用P2转动4个角度记录CCD上的光强图，如图14a、14b、14c、14d所示，依次对应P2为4个偏振角度0度、45度、90度、135度的情形。
上面实施例2-5介绍了四种不同的使用GRIN lens进行空间偏振调制的实施例，使用更多的或不同长度的GRIN lens以及不同的波片可以产生更多不同的空间偏振调制。这里无法穷举。
将GRIN lens作为空间偏振调制器件，具有调制孔径各处连续，调制种类变化丰富的特点，相较于目前市面上其他的基于微纳加工制备的偏振调制器件，具有显著的性能优势和价格优势。

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  1. 一种光的偏振态检测装置，包括外壳，依次设置于光路上的偏振片、成像透镜、CCD，以及数据处理装置和连接于CCD与数据处理装置之间的数据传输线，其中偏振片、成像透镜和CCD至少部分封装在外壳内，其特征是：还包括具有变双折射率特性的透镜，所述具有变双折射率特性的透镜可接收被测入射光并使出射的光线产生光场偏振态的空间相位调制，调制后的光线随后进入偏振片，不同相位的光线经过偏振片发生偏振干涉，产生干涉花样，干涉条纹投射在CCD上记录下来并传输到数据处理装置；所述数据处理装置根据不同的干涉花样形状计算出对应的不同的入射光的偏振态；所述具有变双折射率特性的透镜是指有一定双折射参数有空间相位延迟分布的器件，所述双折射参数包括双折射值和光轴方向。
  2. 如权利要求1所述的光的偏振态检测装置，其特征是：所述数据处理装置是外接计算机，或者是封装在光的偏振态检测装置中的存储器、单片机和显示屏封组合。
  3. 如权利要求1或2所述的光的偏振态检测装置，其特征是：所述具有变双折射率特性的透镜是自聚焦透镜。
  4. 如权利要求3所述的光的偏振态检测装置，其特征是：所述自聚焦透镜可以只有一个，实现偏振态单点探测，也可以有多个，组成m×n的透镜阵列，实现偏振态平面内测量，每个自聚焦透镜对应一个点测量，以便最终得到m×n大小的空间偏振态分布，其中m和n是正整数。
  5. 如权利要求3所述的光的偏振态检测装置，其特征是：所述自聚焦透镜的相位延迟分布覆盖了0-180度的相位延迟，-90-90度的快轴角度。
  6. 如权利要求3所述的光的偏振态检测装置，其特征是：所述光的偏振态检测装置可应用于椭偏仪、穆勒矩阵测量装置和偏振遥感装置。
  7. 一种光偏振检测方法，其特征是：包括如下步骤：
    A、使得待测光束进入仪器进光口，入射光线具有一定的偏振态；
    B、入射光进入具有变双折射率特性的透镜，使其产生光场偏振态的空间相位调节；
    C、从具有变双折射率特性的透镜出射的光线进入偏振片，不同相位的光线经过偏振片发生偏振干涉，产生干涉花样；
    D、光线经过透镜进入CCD，干涉条纹投射在CCD上记录下来；
    E、根据不同的干涉花样形状对应不同的入射光的偏振态，计算出入射光的偏振态。
  8. 如权利要求7所述的光偏振检测方法，其特征是：还包括步骤F、在用户界面将表征偏振态的邦加球和对应的椭圆偏振参数和偏振度显示出来，从而形象地显示出偏振测量的结果。
  9. 如权利要求7所述的光偏振检测方法，其特征是：所述具有变双折射率特性的透镜是自聚焦透镜。
  10. 一种光的偏振态调制装置，其特征是：包括依次设置于光路上的偏振片和具有变双折射率特性的透镜；所述具有变双折射率特性的透镜可对偏振态在三维空间内进行调制，产生具有空间分布的偏振矢量涡旋场；所述具有变双折射率特性的透镜是指有一定双折射参数有空间相位延迟分布的器件，所述双折射参数包括双折射值和光轴方向。
  11. 如权利要求10所述的光的偏振态调制装置，其特征是：所述具有变双折射率特性的透镜有一个或一个以上，在光路串联设置。
  12. 如权利要求10所述的光的偏振态调制装置，其特征是：所述具有变双折射率特性的透镜是自聚焦透镜。
  13. 如权利要求10所述的光的偏振态调制装置，其特征是：还包括波片，在光路上设置于具有变双折射率特性的透镜之间。
  14. 如权利要求13所述的光的偏振态调制装置，其特征是：所述波片是1/2波片或1/4波片。
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