A method for measuring parameters based on optical polarization states

Abstract

The application relates to a parameter measurement method based on optical polarization states, which adopts an optical polarization measurement instrument and comprises the following steps: setting a to-be-measured light source; dynamically or statically calibrating the phase retardation of a liquid crystal box; after calibration, a driving circuit applies a voltage signal changing according to a certain rule to the liquid crystal box, and an experimental measurement mode is obtained based on a measurement device; a plurality of groups of parameters are scanned to obtain a trial solution mode; the experimental measurement mode and the trial solution mode are compared, iterative calculation is carried out, the optimal solution of the polarization state parameters is obtained, and the to-be-measured parameters are determined based on the optimal solution. Compared with the prior art, the application has the advantages of reducing measurement deviation, improving precision, improving efficiency and the like.

Description

Technical Field

[0001] This invention relates to the field of optical polarization state measurement, and in particular to a parameter measurement method based on optical polarization state. Background Technology

[0002] Currently, algorithms for calculating the polarization state of light are mainly based on their respective measurement methods. Generally, after measuring several characteristic values ​​to obtain parameters, these parameters are substituted into specific calculation formulas to directly obtain the relevant parameters of the polarization state. If measurement errors occur due to problems with optical components or incorrect optical component parameters or optical axes by the measurer, the resulting measurement errors are difficult to detect immediately. This inevitably leads to deviations in the calculated polarization state parameters, which are sometimes difficult to detect and eliminate. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art by providing a parameter measurement method based on optical polarization state with small measurement error.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A parameter measurement method based on optical polarization state is disclosed. The method employs an optical polarization measuring instrument, which includes at least one polarization state modulation device to be calibrated, at least one driving circuit, and at least one polarizer. The driving circuit applies a voltage signal to the calibrated polarization state modulation device. In the incident direction of light, at least one polarization state modulation device to be calibrated is located before a polarizer. The optical device closest to the measuring device is the polarizer. Light passing through the polarizer closest to the measuring device enters the measuring device. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the polarization state modulation device to be calibrated and the transmission axis of the polarizer.

[0006] The method includes the following steps:

[0007] Set the light source to be tested;

[0008] The phase delay of the polarization state modulation device to be calibrated is dynamically or statically calibrated to determine the polarization state modulation device to be calibrated, and at the same time the Jones matrix expression of the polarizer is obtained.

[0009] After calibration, the driving circuit applies a voltage signal that changes according to a certain rule to the calibrated polarization modulation device. Based on the measurement device, the change in light intensity transmittance of the emitted light with voltage is measured to obtain the experimental measurement mode. The change according to a certain rule is either increasing or decreasing.

[0010] The computer program scans multiple sets of parameters of the Jones vector of the light source under test. Each set of parameters consists of two parameters: characteristic angle and phase difference. Based on the Jones matrix expression and multiple sets of parameters, an attempted solution mode is obtained. Each attempted solution mode uses a set of parameters.

[0011] The experimental measurement mode and the attempted solution mode are compared by computer, and iterative calculations are performed to obtain the Jones vector parameters of the light source to be tested.

[0012] The system determines whether the Jones vector parameters of the light source under test meet the accuracy requirements. If not, it feeds back to the drive circuit, sets a new voltage signal, and performs measurement and calculation again until the Jones vector parameters of the light source under test meet the accuracy requirements.

[0013] In another aspect, this invention proposes a parameter measurement method based on optical polarization state. The method employs an optical polarization measuring instrument, which includes a light source with a known polarization state, a liquid crystal cell under test, at least one polarization state modulation device to be calibrated, at least one driving circuit, and at least one polarizer. The driving circuit applies a voltage signal to the calibrated polarization state modulation device. In the incident direction of light, at least one polarization state modulation device to be calibrated is located before a polarizer. The optical device closest to the measuring device is the polarizer. Light passing through the polarizer closest to the measuring device enters the measuring device. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the polarization state modulation device to be calibrated and the transmission axis of the polarizer.

[0014] The method includes the following steps:

[0015] Set up a light source with a known polarization state, and place the liquid crystal cell to be tested on the side of the modulator of the polarization state to be calibrated facing the light source or between the modulator of the polarization state to be calibrated and the polarizer.

[0016] The phase delay of the polarization state modulation device to be calibrated is dynamically or statically calibrated to determine the polarization state modulation device to be calibrated, and the Jones matrix expression of the polarizer is obtained at the same time.

[0017] After calibration, the driving circuit applies a voltage signal that varies according to a certain pattern to the calibrated polarization modulation device. Based on the measurement device, the change in light intensity transmittance of the emitted light as a function of voltage is measured to obtain the experimental measurement mode. The "variable according to a certain pattern" can be either increasing or decreasing.

[0018] Based on a light source with a specific polarization state, a computer program scans multiple sets of parameters of the Jones matrix of the liquid crystal cell under test. Each set of parameters consists of two parameters: phase delay and orientation azimuth. Based on the Jones matrix expression and multiple sets of parameters, an attempted solution mode is obtained. Each attempted solution mode uses a set of parameters.

[0019] The experimental measurement mode and the attempted solution mode are compared by computer, and iterative calculations are performed to determine the Jones matrix expression of the liquid crystal cell under test.

[0020] The system determines whether the Jones matrix expression of the liquid crystal cell under test meets the accuracy requirements. If not, it feeds back to the driving circuit, sets a new voltage signal, and performs measurement and calculation again until the Jones vector parameters of the light source under test meet the accuracy requirements.

[0021] Furthermore, the process of iterative calculation, determining whether the accuracy requirement is met, and providing feedback is as follows:

[0022] A1. Set the global weight vector, initialize the global weight vector to 1, and select a solution mode to try;

[0023] A2. Compare the attempted solution mode with the experimental measurement mode, and calculate the deviation function between the attempted solution mode and the experimental measurement mode based on the global weight vector;

[0024] A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution.

[0025] A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal parameter set of the trial solution based on the optimal solution. If not, take the measured experimental Stokes parameters as reference values, transform them to obtain the corresponding reference mode, compare the reference mode and the trial solution mode based on the comparison function, train and iterate the global weight vector using artificial intelligence algorithm, return to A2, and apply the trained global weight vector to the bias function of A2.

[0026] A5. Calculate the error. If the error exceeds the preset threshold, it is fed back to the driving circuit to change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, the optimal parameter set of the optimal attempt solution at this time is taken as the final parameter to be measured.

[0027] Furthermore, the expression for the deviation function is:

[0028] ∑W·(T Try (U)-T M (U)) m

[0029] Where W is the global weight vector, T Try (U) represents the attempted solution mode, U is the voltage, and T is the voltage. M (U) represents the measurement mode, m represents the exponent, and m takes the value of a positive even number.

[0030] Furthermore, the expression for the comparison function is:

[0031] min(∑(∑W·(T Try (U)-T Ref (U)) 2 ))

[0032] Among them, T Ref (U) is the reference mode, T Try (U) represents the attempted solution mode, and W represents the global weight vector.

[0033] Furthermore, the polarization state modulation device to be calibrated uses two liquid crystal cells to be calibrated. When determining the Jones vector parameters of the light source under test, the expression for the mode solution is:

[0034]

[0035] Among them, T Try (U, θ, δ) represents the attempted solution mode, L(Γ1(U), Γ2(U)) represents the Jones matrix of the two liquid crystal cells to be calibrated, Γ1 represents the phase delay of the first polarization modulator to be calibrated, and Γ2 represents the phase delay of the second polarization modulator to be calibrated. J is the Jones vector of the scanned light source under test. 偏振片 Let θ be the Jones matrix of the polarizer, θ be the characteristic angle, and δ be the phase difference.

[0036] Furthermore, the artificial intelligence algorithm is the steepest gradient descent method, deep learning algorithm, or neural network algorithm.

[0037] Furthermore, the measuring device is a CMOS / CCD camera, an optical power meter, or a photodiode, and is used to measure the changing light intensity.

[0038] Furthermore, the static calibration steps are as follows: the liquid crystal cell to be calibrated is placed between two orthogonal polarizers, and the stable transmitted light intensity is measured at various voltages to obtain the light intensity transmittance-voltage curve. The phase delay-voltage curve is calculated based on the light intensity transmittance-voltage curve, and the Jones matrix expression of the polarization state modulation device to be calibrated is obtained from the phase delay-voltage curve.

[0039] The specific steps of dynamic calibration are as follows: the liquid crystal cell to be calibrated is placed between two orthogonal polarizers, the driving circuit applies an increasing, decreasing or regularly changing voltage signal to the liquid crystal cell to be calibrated, the changing transmitted light intensity is measured, and the light intensity transmittance-voltage curve is obtained. Based on the light intensity transmittance-voltage curve, the phase delay-voltage curve is calculated, and the Jones matrix expression of the polarization state modulation device to be calibrated is obtained from the phase delay-voltage curve.

[0040] Furthermore, the connection relationship between the polarization state modulators to be calibrated and the driving circuit is as follows: the polarization state modulators to be calibrated are connected in parallel, one driving circuit is connected to all the polarization state modulators to be calibrated at the same time, and the driving circuit voltage signal is applied to each calibrated polarization state modulator at the same time, or each driving circuit is connected to one polarization state modulator to be calibrated, and the driving circuit voltage signal of each driving circuit is applied to each calibrated polarization state modulator at the same time.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention trains and obtains an optimized global weight vector by trying different parameters and comparing them with experimentally obtained parameters. Using this optimized global weight vector, the optimal solution for the polarization state of the emitted light is obtained. Based on the optimal polarization state solution, the polarization state of the light source or the parameters of the liquid crystal cell can be obtained. The global weight vector used in this invention can effectively reduce or avoid the influence of experimentally measured parameters with large deviations, thereby improving accuracy. Attached Figure Description

[0043] Figure 1 This is a flowchart of Embodiment 1 of the present invention;

[0044] Figure 2 This is a schematic diagram of the structure of the present invention;

[0045] Figure 3 This is a schematic diagram of the optical polarization measuring instrument of the present invention during operation;

[0046] Figure 4 This is a schematic diagram of the structure of the liquid crystal cell of the present invention;

[0047] Figure 5 This is the iterative weight calculation logic diagram of the present invention;

[0048] Figure 6 This is a schematic diagram of Embodiment 1 of the present invention;

[0049] Figure 7 This is a schematic diagram of the first case of Embodiment 2 of the present invention;

[0050] Figure 8 This is a schematic diagram of the second case of Embodiment 2 of the present invention;

[0051] Figure 9 This is a flowchart of Embodiment 2 of the present invention;

[0052] In the diagram, 1. Light emitted by the light source, 2. Optical polarization measuring instrument, 3. Outgoing light, 4. Voltage signal generating device, 5. Measuring device, 100. Optical path of the light source, 101. First liquid crystal cell, 102. Second liquid crystal cell, 103. Polarizer, 104. Driving circuit, 105. Optical power meter, 106. CMOS or CCD camera, 107. Computer, 1010. Glass substrate, 1011. ITO transparent conductive layer, 1012. Alignment layer or anchoring layer, 1013. Liquid crystal layer. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0054] Example 1:

[0055] This invention proposes an optical polarization state measurement method. The method employs an optical polarization measuring instrument 2, which includes at least one polarization state modulation device to be calibrated. This device can be a first liquid crystal cell 101 and a second liquid crystal cell 102, at least one driving circuit 104, and at least one polarizer. The driving circuit 104 applies a voltage signal to the liquid crystal cell to be calibrated. The liquid crystal cell, polarizer 103, and measuring device are arranged sequentially according to the incident direction of light 1 emitted from the light source. In the incident direction of light, there is at least one polarization state modulation device to be calibrated before each polarizer. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the liquid crystal cell to be calibrated and the transmission axis of the polarizer. The device used in this embodiment is as follows: Figure 2 As shown.

[0056] In this invention, the incident light is the light that is about to pass through the polarizer 103 closest to the measuring device 5, and the outgoing light is the light that has passed through the polarizer 103. The outgoing light is the light that enters the measuring device 5.

[0057] By changing the voltage of the driving circuit, the intensity of the emitted light 3 to be measured can be changed accordingly. Therefore, the optical polarization measuring instrument 2 can be placed between the light 1 emitted by the light source and the measuring device 5, and used in conjunction with the device for collecting light intensity information to obtain light intensity change information. The computer 107 calculates and compares the theoretical light intensity change pattern with the actual light intensity change pattern to obtain the best matching polarization state parameters. The measuring device 5 is a CMOS / CCD camera 106, an optical power meter 105, or a photodiode, used to record the light intensity distribution of the emitted light transmitted by the polarization state modulation device to be calibrated under different signal voltages. A schematic diagram of the optical polarization measuring instrument in operation is shown below. Figure 3 As shown. Figure 3 In the diagram, the light path 100 of the light source is the light path of the light 1 emitted by the light source.

[0058] The polarization modulation device to be calibrated in the optical polarization measuring instrument 2 includes a first substrate and a second substrate with transparent conductive electrodes, and an ordered liquid crystal layer 1013 arranged between the first substrate and the second substrate. The first substrate and the second substrate are the glass substrate 1010 in the figure. The ordered liquid crystal layer can be an optically modelable liquid crystal structure, such as parallel arrangement, vertical arrangement, mixed arrangement, twisted arrangement, chiral spiral arrangement, etc., and its arrangement depends on the alignment layer or anchoring layer 1012 disposed on the surface of the first substrate and / or the second substrate. The alignment layer is a photo-alignment layer or a trench alignment layer. An ITO transparent conductive layer 1011 is disposed between the glass substrate 1010 and the alignment layer or anchoring layer 1012. The liquid crystal layer 1013 is disposed parallel to the surface of the first substrate and the second substrate, and the liquid crystal layer 1013 is a nematic liquid crystal, a chiral liquid crystal, or a smectic liquid crystal. A schematic diagram of the structure of the liquid crystal cell to be calibrated is shown below. Figure 4 As shown.

[0059] The voltage signal generating device 4 includes a power supply and a driving circuit 104, which is used to apply a voltage signal to the liquid crystal cell to be calibrated.

[0060] In some embodiments, the optical polarization measuring instrument includes a driving circuit, a linear polarizer with its transmission axis in the horizontal direction, and two parallel-oriented nematic liquid crystal cells. The thickness of the liquid crystal layer in each cell is 12 micrometers. The angle between the optical axis of the first liquid crystal cell 101 and the transmission axis of the linear polarizer is 45°, and the angle between the optical axis of the second liquid crystal cell 102 and the transmission axis of the linear polarizer is 30°. The two liquid crystal cells are connected in parallel, meaning that the signal voltage is synchronously applied to the two liquid crystal cells.

[0061] In some embodiments, the light to be measured is 633 nanometers, and its Jones vector is:

[0062]

[0063] The polarizer 103 of the measuring instrument of the present invention is a linear polarizer, a circular polarizer, or an elliptical polarizer.

[0064] This embodiment uses the aforementioned apparatus to propose a parameter measurement method based on optical polarization state to measure the polarization state of a light beam with an unknown polarization state. The flowchart of this embodiment's method is as follows: Figure 1 As shown. In this embodiment, the Jones vector of the incident light to be measured is calculated by measuring the polarization Jones vector of the outgoing light, the Jones matrix of the polarization modulation device to be calibrated, and the polarizer.

[0065] The method in this embodiment employs an optical polarization measuring instrument, which includes at least one polarization state modulation device to be calibrated, at least one driving circuit, and at least one polarizer. The driving circuit is used to apply a voltage signal to the calibrated polarization state modulation device. In the incident direction of light, there is at least one polarization state modulation device to be calibrated before a polarizer. The optical device closest to the measuring device is the polarizer. Light passing through the polarizer closest to the measuring device enters the measuring device. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the polarization state modulation device to be calibrated and the transmission axis of the polarizer.

[0066] The polarization state modulation device in this embodiment uses two liquid crystal cells.

[0067] The method includes the following steps:

[0068] S1. Set the light source to be tested;

[0069] S2. Perform dynamic or static calibration on the phase delay of the polarization state modulation device to be calibrated, determine the polarization state modulation device to be calibrated, and obtain the Jones matrix expression of the polarizer.

[0070] S3. After calibration, the driving circuit applies a voltage signal that changes according to a certain rule to the calibrated polarization modulation device. Based on the measurement device, the change of light intensity transmittance of the emitted light with voltage is measured to obtain the experimental measurement mode. The change according to a certain rule is either increasing or decreasing.

[0071] S4. The computer program scans multiple sets of parameters of the polarization state Jones vector of the light source under test. Each set of parameters consists of two parameters, namely the characteristic angle and the phase difference. Based on the Jones matrix expression and multiple sets of parameters, the attempted solution mode is obtained. Each attempted solution mode uses a set of parameters.

[0072] S5. Based on the computer, the experimental measurement mode and the attempted solution mode are compared and iterative calculations are performed to obtain the Jones vector polarization state parameters of the light source to be tested;

[0073] S6. Determine whether the Jones vector parameters of the light source under test meet the accuracy requirements. If not, feed back to the drive circuit, set a new voltage signal, and perform measurement and calculation again until the Jones vector parameters of the light source under test meet the accuracy requirements. If yes, use the Jones vector parameters of the light source under test as the final Jones vector parameters of the light source under test.

[0074] In the above method, before measuring the polarization state of the light to be measured, S1 is first executed to calibrate the phase retardation of the two liquid crystal cells to be calibrated. Calibration is divided into dynamic calibration and static calibration. For dynamic calibration, the phase retardation (Γ)-voltage (U) curve is calculated by measuring the light intensity transmittance (T)-voltage (U) curves of the corresponding liquid crystal cells (with an angle of 45° between the optical axis and the transmission axis of one of the polarizers) placed between two orthogonal polarizers. When using two polarization state modulation devices to be calibrated, the Jones matrix expression (L(Γ1(U), Γ2(U))) of the polarization state modulation device composed of the two liquid crystal cells is obtained in this way. Simultaneously, the Jones matrix J of the polarizer is obtained. 偏振片 .

[0075] The specific steps of static calibration are as follows: Place the polarization state modulation device to be calibrated between two orthogonal polarizers, measure the stable transmitted light intensity at various voltages to obtain the light intensity transmittance-voltage curve, calculate the phase delay-voltage curve based on the light intensity transmittance-voltage curve, and obtain the Jones matrix expression of the polarization state modulation device and polarizer to be calibrated from the phase delay-voltage curve.

[0076] The specific steps of dynamic calibration are as follows: the polarization modulator to be calibrated is placed between two orthogonal polarizers, the driving circuit applies an increasing, decreasing or regularly changing voltage signal to the polarization modulator to be calibrated, the changing transmitted light intensity is measured, and the light intensity transmittance-voltage curve is obtained. Based on the light intensity transmittance-voltage curve, the phase delay-voltage curve is calculated, and the Jones matrix expression of the polarization modulator and polarizer to be calibrated is obtained from the phase delay-voltage curve.

[0077] Then, S2 is executed, and the power supply and drive circuit applies incremental AC voltage signals to the two liquid crystal cells. For example, the following voltage signals can be applied: 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, 1.6V, 1.7V, 1.8V, 1.9V, 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.8V, 3.0V, 3.3V, 3.5V, 3.8V, 4.0V, 4.3V, 4.5V, 4.8V, 5.0V, 7.5V, and 10.0V.

[0078] Then, in step S3, the light transmittance (T) of the emitted light is measured and recorded as a function of voltage (U) using an optical power meter 105 or a CMOS / CCD camera 106, thereby obtaining the experimentally measured T. M (U) mode. Experimentally measured T M (U) represents the normalized T of the light intensity signal that varies with voltage. M ~U curve, the horizontal axis of the curve is voltage, and the vertical axis is transmittance T.M .

[0079] Then execute S4 to scan multiple sets of parameters of the polarization state Jones vector of the light source under test.

[0080] In S5 and S6, the flowcharts for iterative calculations are as follows: Figure 5 As shown, the iterative calculation and feedback process is as follows:

[0081] A1. Set the global weight vector, initialize it to 1, and select a solution mode to try. in The Jones vector of the scanned light source under test;

[0082] A2, will attempt to solve the pattern With experimental measurement mode T M (U), that is, the normalized T of the emitted light. M ~ Compare the U curves, where T M For transmittance, the deviation function ∑W·(T) between the attempted solution mode and the experimental measurement mode is calculated based on the global weight vector. Try (U,θ i δ i )-T M (U)) m .

[0083] In A2, the transmittance of the emitted light determines the experimental measurement mode. During comparison, the Jones vector E of the light source under test is obtained by substituting the scanning parameters. 光源 The attempted Jones vector of the incident light is obtained, and the attempted light intensity transmittance of the outgoing light (i.e., the attempted solution mode) is obtained based on this attempted Jones vector. The light intensity transmittance at each voltage in the experimentally measured mode is compared with the light intensity transmittance at the corresponding voltage in the attempted solution mode obtained by scanning the Jones vector of the incident light according to the deviation function.

[0084] The formula used in this process is:

[0085] |E 出射 | 2 =|J 偏振片 E 入射 | 2

[0086] E 入射 =L(Γ1(U),Γ2(U)E 光源

[0087] Among them, E 光源 J is the Jones vector of the scanned light source under test. 偏振片 Let LΓ1(U),Γ2(U)) be the Jones matrix of the polarizer, and E be the Jones matrix of the modulation device for the polarization state to be calibrated.入射 The Jones vector for the incident light.

[0088] A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution.

[0089] A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal Jones vector for scanning based on it. If not, use the measured experimental Stokes parameters as reference values ​​and convert them to obtain the corresponding reference pattern. in The Jones vector of the reference light source is used to compare the reference mode and the attempted solution mode based on the comparison function. The global weight vector is trained and iterated using artificial intelligence algorithms and returned to A2. The trained global weight vector is then applied to the deviation function of A2.

[0090] A5. Calculate the error. If the error exceeds the preset threshold, change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, use the optimal scanned Jones vector at this time as the Jones vector polarization state parameter of the light source under test.

[0091] In A2, the expression for the deviation function is:

[0092] ∑W·(T Try (U,θ i δ i )-T M (U)) m

[0093] Where W is the global weight vector, T Try (U,θ i δ i () represents the attempted solution mode, where U is the voltage and θ is the voltage. i Let δ be the i-th characteristic angle. i Let θ be the i-th phase difference, where i is a positive integer from 1 to N, representing the index of the characteristic angle and the phase difference, and the parameter set (θ). i δ i T is obtained by dividing the preset total characteristic angle and total phase difference into N equal intervals within their respective value ranges. M (U) represents the measurement mode, and m represents the exponent, with a value of 2, 4, or 6. m can also take other positive even numbers.

[0094] Based on the above deviation function, mode comparison is performed to obtain intermediate solutions (θ). s δ s), where W is the global weight vector, and each component corresponds one-to-one with the voltage, with an initial value of 1.

[0095] In A4, the corresponding reference mode T is obtained by using theoretical values ​​or relatively accurate experimental values ​​(S1, S2, S3) obtained by other traditional methods as reference values ​​and then transforming them. Ref (U).

[0096] Substitute the reference mode into the following comparison function:

[0097] min(∑(∑W·(T Try (U,θ s δ s )-T Ref (U)) 2 ))

[0098] Among them, T Ref (U) is the reference mode, (θ) s δ s ) represents an intermediate solution, θ s The characteristic angle of the intermediate solution, δ s This represents the phase difference of the intermediate solution.

[0099] The global weight vector W is trained and iterated using the steepest gradient descent method to obtain an optimized global weight allocation. Alternatively, other artificial intelligence algorithms, such as deep learning algorithms and neural network algorithms, can be used instead of the steepest gradient descent method. Finally, the trained global weight vector W is applied again to the comparative calculation of the experimental measurement mode to obtain the polarization state parameters, i.e., the final optimal solution (θ, δ), which is then converted into normalized Stokes parameters (S1, S2, S3) using a formula. Based on the optimal solution, the polarization state of the incident light under test can be determined.

[0100] In this invention, when using a CMOS / CCD camera to simultaneously measure multiple polarization states, an additional algorithm for automatically classifying pixels is required. Based on the light intensity transmittance change curve, similar pixels are classified into the same polarization state, and then the parameter information of each polarization state is obtained according to the algorithm for calculating a single polarization state.

[0101] Example 2:

[0102] This embodiment uses the same apparatus as Embodiment 1, but differs in that it uses incident light with a known polarization state. The liquid crystal cell to be tested is placed on the side of the modulation device to be calibrated facing the light source, or between the modulation device and the polarizer. This embodiment obtains the Jones matrix of the liquid crystal cell to be tested by measuring the polarization state parameters of the emitted light, adding the polarization state of the light source, and the Jones matrix of the calibrated liquid crystal cell and polarizer. This yields the optical parameters of the liquid crystal cell, including bit retardation distribution, refractive index distribution, cell thickness distribution, or director distribution. The flowchart of this embodiment's method is shown below. Figure 9 As shown.

[0103] The method used in this embodiment includes the following steps:

[0104] S1. Set up a light source with a known polarization state, and place the liquid crystal cell to be tested on the side of the modulator of the polarization state to be calibrated facing the incident light or between the modulator of the polarization state to be calibrated and the polarizer.

[0105] S2. Perform dynamic or static calibration on the phase delay of the polarization state modulator to be calibrated, and determine the Jones matrix expression of the polarization state modulator and polarizer to be calibrated.

[0106] S3. After calibration, the driving circuit applies a voltage signal that changes according to a certain rule to the calibrated polarization modulation device. Based on the measurement device, the change of light intensity transmittance of the emitted light with voltage is measured to obtain the experimental measurement mode. The change according to a certain rule is either increasing or decreasing.

[0107] S4. The computer program scans multiple sets of parameters of the Jones matrix of the liquid crystal cell under test. Each set of parameters consists of two parameters, namely the phase delay and the orientation azimuth angle. Based on the Jones matrix expression and multiple sets of parameters, the attempted solution mode is obtained. Each attempted solution mode uses a set of parameters.

[0108] S5. Based on the computer, the experimental measurement mode and the attempted solution mode are compared, iterative calculations are performed, and the Jones matrix expression of the liquid crystal cell to be tested is determined.

[0109] S6. Determine whether the Jones vector parameters of the light source under test meet the accuracy requirements. If not, feed back to the drive circuit, set a new voltage signal, and perform measurement and calculation again until the Jones vector parameters of the light source under test meet the accuracy requirements.

[0110] The method used in S3 in this embodiment is the same as that in embodiment 1.

[0111] The difference between S4 and Example 1 is that the scanning parameter is the Jones matrix of the liquid crystal cell under test.

[0112] The difference between S5 and Example 1 is that when the liquid crystal cell under test is placed on the side of the polarization modulation device to be calibrated facing the incident light, the iterative calculation process in S5 is as follows:

[0113] A1. Set the global weight vector, initialize it to 1, and select a solution mode T to attempt. Try (U)=|J 偏振片 L(Γ1(U),Γ2(U))L try E 光源 | 2 L try E is the Jones matrix of the liquid crystal cell under test into which the scanning parameters are substituted. 光源 The Jones vector of the known light source;

[0114] A2. The trial solution mode and the experimental measurement mode T M (U), that is, the normalized T of the emitted light. M ~ Compare the U curves, where T M For transmittance, the deviation function ∑W·(T) between the attempted solution mode and the experimental measurement mode is calculated based on the global weight vector. Try (U,L try )-T M (U)) m .

[0115] In A2, the transmittance of the emitted light determines the experimental measurement mode. During comparison, the Jones matrix (L) of the liquid crystal cell under test is obtained by substituting the scanning parameters into it. 待测液晶盒 L try The parameters are used to obtain the attempted Jones vector of the incident light, and based on this attempted Jones vector, the attempted light intensity transmittance of the outgoing light (i.e., the attempted solution mode) is obtained. The light intensity transmittance at each voltage in the experimental measurement mode is then compared with the Jones matrix of the liquid crystal cell under test (L). 待测液晶盒 The light transmittance of the corresponding voltage in the attempted solution mode obtained from the parameters is compared according to the deviation function. The formula used in this process is:

[0116] |E 出射 | 2 =|J 偏振片 E 入射 | 2

[0117] E 入射 =L 待测液晶盒 L(Γ1(U),Γ2(U))E 光源 (E 入射 =L try L(Γ1(U),Γ2(U))E 光源 )

[0118] Among them, E光源 Let J be the Jones vector of the light source, and J be a known quantity. 偏振片 Let L(Γ1(U),Γ2(U)) be the Jones matrix of the polarizer, and let E be the Jones matrix of the modulation device whose polarization state is to be calibrated. 入射 For the attempted Jones vector of the incident light, L 待测液晶盒 The Jones matrix is ​​for the scanned liquid crystal cell under test.

[0119] A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution.

[0120] A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal Jones matrix for scanning based on this optimal solution. If not, take the measured experimental Stokes parameters as reference values ​​and transform them to obtain the corresponding reference pattern.

[0121] T Ref (U)=|J 偏振片 L(Γ1(U),Γ2(U))L 待测液晶盒 E 光源 | 2

[0122] Where E 光源 Given the Jones vector of the light source, L 待测液晶盒 The reference test liquid crystal cell's Jones matrix is ​​determined based on experimental Stokes parameters. The reference mode and the attempted solution mode are compared using a comparison function. An artificial intelligence algorithm is used to train and iterate the global weight vector, returning A2. The trained global weight vector is then applied to the bias function of A2.

[0123] A5. Calculate the error. If the error exceeds the preset threshold, change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, use the optimal scanned Jones matrix at this time as the Jones matrix of the liquid crystal cell under test.

[0124] The principle of calculating the parameters of the liquid crystal cell under test is as follows: Figure 7 As shown. The Jones matrices of the two calibrated liquid crystal cells are known, the Jones matrix of the polarizer is known, the polarization state of the incident light is known, and the polarization state parameters of the outgoing light are measured. At this point, the Jones matrix of the liquid crystal cell under test can be calculated, and the parameters of the liquid crystal cell under test can be obtained.

[0125] When the liquid crystal cell under test is placed between the modulation device for the polarization state to be calibrated and the polarizer, the principle for calculating the parameters of the liquid crystal cell under test is as follows: Figure 8As shown, the iterative calculation process of S5 at this point is as follows:

[0126] A1. Set the global weight vector, initialize it to 1, and select a solution mode T to attempt. Try (U,L try )=|J 偏振片 L try L(Γ1(U),Γ2(U))E 光源 | 2 L try E is the Jones matrix of the liquid crystal cell under test into which the scanning parameters are substituted. 光源 The Jones vector of the known light source;

[0127] A2. The trial solution mode and the experimental measurement mode T M (U), that is, the normalized T of the emitted light. M ~ Compare the U curves, where T M For transmittance, the deviation function ∑W·(T) between the attempted solution mode and the experimental measurement mode is calculated based on the global weight vector. Try (U,L try )-T M (U)) m .

[0128] In A2, the transmittance of the emitted light determines the experimental measurement mode. During comparison, the Jones matrix (L) of the liquid crystal cell under test is obtained by substituting the scanning parameters. 待测液晶盒 L try The parameters are used to obtain the attempted Jones vector of the incident light, and based on this attempted Jones vector, the attempted light intensity transmittance of the outgoing light (i.e., the attempted solution mode) is obtained. The light intensity transmittance at each voltage in the experimental measurement mode is then compared with the Jones matrix of the liquid crystal cell under test (L). 待测液晶盒 The light transmittance of the corresponding voltage in the attempted solution mode obtained from the parameters is compared according to a comparison function. The formula used in this process is:

[0129] |E 出射 | 2 =|J 偏振片 E 入射 | 2

[0130] E 入射 =L 待测液晶盒 L(Γ1(U),Γ2(U))E 光源 (E 入射 =L try L(Γ1(U),Γ2(U))E 光源 )

[0131] Among them, E 光源Let J be the Jones vector of the light source, and J be a known quantity. 偏振片 Let L(Γ1(U),Γ2(U)) be the Jones matrix of the polarizer, and let E be the Jones matrix of the modulation device whose polarization state is to be calibrated. 入射 Let L be the Jones vector of the incident light. 待测液晶盒 This is the Jones matrix of the liquid crystal cell under test.

[0132] A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution.

[0133] A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal Jones matrix for scanning based on this optimal solution. If not, take the measured experimental Stokes parameters as reference values ​​and transform them to obtain the corresponding reference pattern.

[0134] T Ref (U,θ,δ0=|J 偏振片 L 待测液晶盒 L(Γ1(U),Γ2(U))E 光源 | 2

[0135] Where E 光源 Given the Jones vector of the light source, L 待测液晶盒 The Jones matrix of the LCD cell under test is used as a reference. The reference mode and the attempted solution mode are compared based on the comparison function. The global weight vector is trained and iterated using artificial intelligence algorithm, and A2 is returned. The trained global weight vector is applied to the deviation function of A2.

[0136] A5. Calculate the error. If the error exceeds the preset threshold, change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, use the optimal scanned Jones matrix at this time as the Jones matrix of the liquid crystal cell under test.

[0137] Similar to when the liquid crystal cell under test is placed on the side of the polarization modulation device to be calibrated facing the incident light, the Jones matrix of the two calibrated liquid crystal cells is known, the Jones matrix of the polarizer is known, the polarization state of the incident light is known, and the polarization state parameters of the outgoing light are measured. At this time, the Jones matrix of the liquid crystal cell under test can be calculated, and the parameters of the liquid crystal cell under test can be obtained.

[0138] The error in A5 of this invention refers to the root mean square error (RMSE), which, for Example 1, is:

[0139]

[0140] It can be set to a fixed threshold, and of course, the RMSE threshold can also be dynamically adjusted according to the algorithm, which makes it more flexible, efficient and accurate.

[0141] The polarization state modulation device to be calibrated in this invention can be a liquid crystal cell or lithium niobate material.

[0142] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A parameter measurement method based on optical polarization state, characterized in that, The method employs an optical polarization measuring instrument, which includes at least one modulator of a polarization state to be calibrated, at least one driving circuit, and at least one polarizer. The driving circuit applies a voltage signal to the calibrated modulator. In the incident direction of light, there is at least one modulator of a polarization state to be calibrated before each polarizer. The optical device closest to the measuring device is the polarizer. Light passing through the polarizer closest to the measuring device enters the measuring device. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the modulator of the polarization state to be calibrated and the transmission axis of the polarizer. The method includes the following steps: Set the light source to be tested; The phase delay of the polarization state modulation device to be calibrated is dynamically or statically calibrated to determine the polarization state modulation device to be calibrated, and at the same time the Jones matrix expression of the polarizer is obtained. After calibration, the driving circuit applies a voltage signal that changes according to a certain rule to the calibrated polarization modulation device. Based on the measurement device, the change in light intensity transmittance of the emitted light with voltage is measured to obtain the experimental measurement mode. The change according to a certain rule is either increasing or decreasing. The computer program scans multiple sets of parameters of the Jones vector of the light source under test. Each set of parameters consists of two parameters: characteristic angle and phase difference. Based on the Jones matrix expression and multiple sets of parameters, an attempted solution mode is obtained. Each attempted solution mode uses a set of parameters. The experimental measurement mode and the attempted solution mode are compared by computer, and iterative calculations are performed to obtain the Jones vector parameters of the light source to be tested. Determine whether the Jones vector parameters of the light source under test meet the accuracy requirements. If not, feed back to the drive circuit, set a new voltage signal, and perform measurement and calculation again until the Jones vector parameters of the light source under test meet the accuracy requirements. The iterative calculation, determination of accuracy, and feedback process are as follows: A1. Set the global weight vector, initialize the global weight vector to 1, and select a solution mode to try; A2. Compare the attempted solution mode with the experimental measurement mode, and calculate the deviation function between the attempted solution mode and the experimental measurement mode based on the global weight vector; A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution. A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal parameter set of the trial solution based on the optimal solution. If not, take the measured experimental Stokes parameters as reference values, transform them to obtain the corresponding reference mode, compare the reference mode and the trial solution mode based on the comparison function, train and iterate the global weight vector using artificial intelligence algorithm, return to A2, and apply the trained global weight vector to the bias function of A2. A5. Calculate the error. If the error exceeds the preset threshold, it is fed back to the driving circuit to change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, the optimal parameter set of the optimal attempt solution at this time is taken as the final parameter to be measured.

2. A parameter measurement method based on optical polarization state, characterized in that, The method employs an optical polarization measuring instrument, which includes a light source with a known polarization state, a liquid crystal cell under test, at least one modulator of the polarization state to be calibrated, at least one driving circuit, and at least one polarizer. The driving circuit applies a voltage signal to the calibrated modulator of the polarization state. In the incident direction of light, there is at least one modulator of the polarization state to be calibrated before a polarizer. The optical device closest to the measuring device is the polarizer. Light passing through the polarizer closest to the measuring device enters the measuring device. The measuring device is connected to a computer. A certain angle is formed between the optical axis of the modulator of the polarization state to be calibrated and the transmission axis of the polarizer. The method includes the following steps: Set up a light source with a known polarization state, and place the liquid crystal cell to be tested on the side of the modulator of the polarization state to be calibrated facing the light source or between the modulator of the polarization state to be calibrated and the polarizer. The phase delay of the polarization state modulation device to be calibrated is dynamically or statically calibrated to determine the polarization state modulation device to be calibrated, and at the same time the Jones matrix expression of the polarizer is obtained. After calibration, the driving circuit applies a voltage signal that varies according to a certain pattern to the calibrated polarization modulation device. Based on the measurement device, the change in light intensity transmittance of the emitted light as a function of voltage is measured to obtain the experimental measurement mode. The "variable according to a certain pattern" can be either increasing or decreasing. Based on a light source with a specific polarization state, a computer program scans multiple sets of parameters of the Jones matrix of the liquid crystal cell under test. Each set of parameters consists of two parameters: phase delay and orientation azimuth. Based on the Jones matrix expression and multiple sets of parameters, an attempted solution mode is obtained. Each attempted solution mode uses a set of parameters. The experimental measurement mode and the attempted solution mode are compared by computer, and iterative calculations are performed to determine the Jones matrix expression of the liquid crystal cell under test. The process involves determining whether the Jones matrix expression of the liquid crystal cell under test meets the accuracy requirements. If not, feedback is sent to the driving circuit to set a new voltage signal, and the measurement and calculation are repeated until the Jones vector parameters of the light source under test meet the accuracy requirements. The specific steps of iterative calculation, accuracy determination, and feedback are as follows: A1. Set the global weight vector, initialize the global weight vector to 1, and select a solution mode to try; A2. Compare the attempted solution mode with the experimental measurement mode, and calculate the deviation function between the attempted solution mode and the experimental measurement mode based on the global weight vector; A3. If the deviation function is not at its minimum, select another trial solution mode and repeat A2. If the deviation function is at its minimum, use the parameter set of the trial solution mode as an intermediate solution. A4. Determine whether the intermediate solution has undergone global weight vector training. If so, take the intermediate solution as the final optimal solution and determine the optimal parameter set of the trial solution based on the optimal solution. If not, take the measured experimental Stokes parameters as reference values, transform them to obtain the corresponding reference mode, compare the reference mode and the trial solution mode based on the comparison function, train and iterate the global weight vector using artificial intelligence algorithm, return to A2, and apply the trained global weight vector to the bias function of A2. A5. Calculate the error. If the error exceeds the preset threshold, it is fed back to the driving circuit to change the driving signal, change the voltage applied to the polarization modulation device, update the experimental measurement mode, and return to A2. If the error does not exceed the preset threshold, the optimal parameter set of the optimal attempt solution at this time is taken as the final parameter to be measured.

3. A parameter measurement method based on optical polarization state according to claim 1 or 2, characterized in that, The expression for the deviation function is: ∑W∙ ( T Try ( U ) -T M ( U )) m in, W This is the global weight vector. T Try ( U To attempt to solve the pattern, U For voltage, T M ( U ) represents the measurement mode, m represents the exponent, and m takes the value of a positive even number.

4. The parameter measurement method based on optical polarization state according to claim 3, characterized in that, The expression for the comparison function is: min ( ∑ ( ∑W∙ ( T Try ( U ) -T Ref ( U )) 2 )) in, T Ref ( U (This is a reference model.) T Try ( U To attempt to solve the pattern, W This is the global weight vector.

5. The parameter measurement method based on optical polarization state according to claim 4, characterized in that, The polarization state modulation device to be calibrated uses two liquid crystal cells to be calibrated. When determining the Jones vector parameters of the light source under test, the expression for the mode solution is: in, In order to attempt to solve the pattern, For the Jones matrix of two uncalibrated liquid crystal cells, This represents the phase delay of the first polarization state modulator to be calibrated. This represents the phase delay of the second polarization state modulator to be calibrated. The Jones vector of the scanned light source under test. The Jones matrix of the polarizer. The characteristic angle, This represents the phase difference.

6. A parameter measurement method based on optical polarization state according to claim 1 or 2, characterized in that, The artificial intelligence algorithms are steepest gradient descent, deep learning algorithms, or neural network algorithms.

7. A parameter measurement method based on optical polarization state according to claim 1 or 2, characterized in that, The measuring device is a CMOS / CCD camera, an optical power meter, or a photodiode, and is used to measure changes in light intensity.

8. A parameter measurement method based on optical polarization state according to claim 1 or 2, characterized in that, The specific steps of static calibration are as follows: place the liquid crystal cell to be calibrated between two orthogonal polarizers, measure the stable transmitted light intensity under various voltages to obtain the light intensity transmittance-voltage curve, calculate the phase delay-voltage curve based on the light intensity transmittance-voltage curve, and obtain the Jones matrix expression of the polarization state modulation device to be calibrated from the phase delay-voltage curve. The specific steps of dynamic calibration are as follows: the liquid crystal cell to be calibrated is placed between two orthogonal polarizers, the driving circuit applies an increasing, decreasing or regularly changing voltage signal to the liquid crystal cell to be calibrated, the changing transmitted light intensity is measured, and the light intensity transmittance-voltage curve is obtained. Based on the light intensity transmittance-voltage curve, the phase delay-voltage curve is calculated, and the Jones matrix expression of the polarization state modulation device to be calibrated is obtained from the phase delay-voltage curve.

9. A parameter measurement method based on optical polarization state according to claim 1 or 2, characterized in that, The connection relationship between the polarization state modulators to be calibrated and the driving circuit is as follows: the polarization state modulators to be calibrated are connected in parallel, one driving circuit is connected to all the polarization state modulators to be calibrated at the same time, and the driving circuit voltage signal is applied to each calibrated polarization state modulator at the same time, or each driving circuit is connected to one polarization state modulator to be calibrated, and the driving circuit voltage signal of each driving circuit is applied to each calibrated polarization state modulator at the same time.

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