CN104236857A - Liquid crystal optical phase shift distribution detection system and method based on quarter-wave plate method - Google Patents

Abstract

The invention discloses a liquid crystal optical phase shift distribution detection system and method based on a quarter-wave plate method. The quarter-wave plate method is applied to obtain data of phase delay amount of each point on a sample to be detected, algorithm improvement is performed on data processing based on the quarter-wave plate method, accordingly a Fourier quarter-wave plate method is provided, interference of noise in the data is eliminated by means of a disperse Fourier algorithm, and a phase value is accurately obtained. The liquid crystal optical phase shift distribution detection system based on the quarter-wave plate method comprises a laser device, the sample to be detected, a micro-objective, a quarter-wave plate, a polarization analyzer, a stepping motor, a charge coupled device (CCD) and a computer control center. The liquid crystal optical phase shift distribution detection system and method based on the quarter-wave plate method determines the phase delay amount of the sample, achieves high-accuracy, high-resolution, quick and automatic detection on a two-dimensional liquid crystal phase shifting device and improves the resolution and accuracy of phased array phase distribution detection.

Description

Based on liquid crystal optics phase shift distributed detection system and the method for quarter-wave plate method

Technical field

The invention belongs to optics phase shift detection technique field, particularly relate to a kind of liquid crystal optics phase shift distributed detection system based on quarter-wave plate method and method.

Background technology

In liquid crystal optics phase shifting device, particularly in liquid crystal phase shift array device (such as: liquid crystal optical phased array), the technical indicators such as maximum deflection angle, effective aperture, pointing accuracy all have direct relation with the phase shift of device to incident laser.Therefore, the detection technique of liquid crystal optics phase shift can provide reliable detection means and foundation for further developing of the phased device of liquid crystal optics.Wherein: high resolving power, high precision, be its detection method or the system ability that needs to possess and technical indicator fast.Current Method for Phase Difference Measurement mainly contains spectrum and surveys phase method, penalty method, photon flux method, phase modulation method etc.But in enforcement these methods when building light path system, require that test environment possesses high shock resistance and the phase place of diverse location on sample just can be avoided to interact in the detection, therefore cannot test the Phase-Shifting Characteristics of the two-dimentional liquid crystal phase shift array device possessing higher spatial resolution, the space distribution details of 1 micron dimension in liquid crystal phase shift array device cannot be detected.Adopting traditional quarter wave plate method simultaneously and adding microcobjective improves in the method for spatial resolution, owing to needing the differentiation to minimum shoot laser power density, measuring accuracy, robotization realization, shock resistance, detection speed there is larger deficiency, the high precision to two-dimentional liquid crystal phase shifting device, high resolving power, detection fast and automatically cannot be realized.

Summary of the invention

The object of the embodiment of the present invention is to provide a kind of liquid crystal optics phase shift distributed detection system based on quarter-wave plate method and method, is intended to the problem that resolution is low, precision is low, shock resistance is low solving existing phase shift detection method.

The embodiment of the present invention is achieved in that a kind of liquid crystal optics phase shift based on quarter-wave plate method distribution detection method, it is characterized in that, should comprise based on the liquid crystal optics phase shift distribution detection method of quarter-wave plate method:

Step one, is erected in coaxial light path by linearly polarized laser device, testing sample, quarter wave plate, microcobjective, the analyzer of hollow stepper motor universal stage, charge coupled cell;

Step 2, the direction of the polarization direction of linearly polarized laser, analyzer is mutually vertical, and wherein analyzer analyzing direction sign is decided to be 0 degree of position of system perspective;

Step 3, by the adjustment of quarter wave plate optical axis direction at 0 degree or 90 degree, the direction of the optical axis of testing sample is arranged on 45 degree or 135 degree, testing sample and linearly polarized laser device, quarter wave plate, analyzer constitutes basic quarter wave plate method, the linearly polarized light that laser instrument sends is through the ordinary light and the extraordinary ray that are decomposed into certain phase differential during phased array sample, the polarized light of certain polarization direction is converted into again through quarter wave plate method, the angle changing of polarization direction is 1/2 of phase delay, rotate again analyzer again the change of polarization size of delustring to this linearly polarized light judge, thus obtain phase-delay quantity,

Step 4, the distance of adjustment microcobjective and testing sample, by the image of charge coupled cell, is adjusted to picture the most clear;

Step 5, drives analyzer to revolve turnback by computer controlling center control step universal stage, and while analyzer once often rotates, charge coupled cell obtains and obtains N frame gradation data I according to identical step angle _i(x, y), wherein i=(1,2,3,, the N) anglec of rotation that is analyzer, (x, y) is the point coordinate on sample, thus obtains N number of gradation data that on testing sample, each some position is corresponding;

Step 6, is obtaining each frame data I by charge coupled cell _iwhile (x, y), computer controlling center carries out data processing.

Further, in step one, allow laser successively by the center of each device, hollow stepper motor universal stage, charge coupled cell are connected to computer controlling center by data line simultaneously.

Further, in step 5, wherein subscript i=1,2,3 ..., N, (x, y) is the space element marking of charge coupled cell gradation data, and the angle of corresponding analyzer is θ _idata acquisition number N is relevant with final precision, and the precision of the larger detection of N is higher, is subject to the impact of charge coupled cell frame per second simultaneously, and N causes more greatly the reduction of detection speed, and N is set as 50 ~ 200.

Further, each frame data I is being obtained by charge coupled cell _iwhile (x, y), computer controlling center is carried out data processing method and is:

According to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, survey the phase place of device in (x, y) position wherein: ${\mathrm{\φ}}_X=\arctan \left[\frac{\mathrm{Im}\left[X\right]}{\mathrm{Re}\left[X\right]}\right];$ By the calculating of computer controlling center, complete the phase shift information of all location of pixels of inside, single visual field.Fourier algorithm implementation method realizes the acquisition of minimum value in curve as follows:

The angular frequency of curve ₀for definite value, the total angle rotated by analyzer determines, assuming that intermediate variable complex matrix X (x, y), and utilizes the gradation data of every bit (x, y) on the mode calculation sample of weighted sum to become conversion again wherein ω ₀=2, θ _iin units of radian, thus obtain this curve at ω by Euler's formula ₀real part when=2 and imaginary part respectively the curve of every bit position on sample is processed when often obtaining frame data, calculated curve actual frequency ω ₀real part and imaginary part;

Data acquisition is complete, obtain real part and the imaginary part of every bit position on sample, according to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, and sinusoidal curve initial phase and the total phase difference of pi of minimum value, survey the phase place of device in (x, y) position wherein: by the calculating of control center, complete the phase shift information of all location of pixels of inside, single visual field.

Another object of the present invention is to provide a kind of liquid crystal optics phase shift distributed detection system based on quarter-wave plate method, it is characterized in that, should comprise based on the liquid crystal optics phase shift distributed detection system of quarter-wave plate method: laser instrument, microcobjective, quarter wave plate, analyzer, stepper motor, charge coupled cell, computer controlling center;

Laser instrument for sending linearly polarized laser connects testing sample, testing sample connects the microcobjective being used for flourishing laser, microcobjective connects the quarter wave plate for obtaining data, quarter wave plate connects analyzer and stepper motor, analyzer is connected charge coupled cell with stepper motor, and analyzer is connected computer controlling center with stepper motor and charge coupled cell;

Laser instrument produces linearly polarized laser as the initial laser that phase delay does not occur in experiment, microcobjective carries out high resolution scanning to sample, dephased ordinary light and extraordinary ray are changed into the polarized light having certain polarization direction by quarter wave plate, change of polarized direction angular dimension equals 1/2 phase-delay quantity, stepper motor drives the accurate stepping of analyzer to obtain this polarized light through the light intensity situation of change of analyzer when different angles, and charge coupled cell collects experimental data to light intensity and delivers to computer controlling center and carry out data processing.

Liquid crystal optics phase shift distributed detection system based on quarter-wave plate method provided by the invention and method, for the phase-delay quantity of every bit on testing sample, quarter-wave plate method is used to obtain data, on quarter wave plate method detection method basis, algorithm improvement has been carried out to data processing, thus propose Fourier quarter-wave plate method, the interference of noise in data is eliminated by discrete Fourier algorithm, Obtaining Accurate phase value, thus determine the phase-delay quantity of sample, by detecting the quarter wave plate device of standard and LCD phased array sample, the precision of known the method detected phase retardation reaches 0.3 degree, and this detection method can obtain introns distribution situation concrete in LCD phased array sample and the impact of spacing motor.Achieve and high precision, high resolving power, detection are fast and automatically carried out to two-dimentional liquid crystal phase shifting device, improve the resolution and precision that detect phased array PHASE DISTRIBUTION.

Accompanying drawing explanation

Fig. 1 is the distribution of the liquid crystal optics phase shift based on the quarter-wave plate method detection method process flow diagram that the embodiment of the present invention provides;

Fig. 2 is the process flow diagram that control center that the embodiment of the present invention provides carries out data processing;

Fig. 3 is the liquid crystal optics phase shift distributed detection system structural representation based on quarter-wave plate method that the embodiment of the present invention provides;

Fig. 4 is the PHASE DISTRIBUTION testing result schematic diagram of the LCD phased array sample that the embodiment of the present invention provides;

In figure: 1, laser instrument; 2, testing sample; 3, microcobjective; 4, quarter wave plate; 5, analyzer and stepper motor; 6, charge coupled cell; 7, computer controlling center.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Below in conjunction with drawings and the specific embodiments, application principle of the present invention is further described.

As shown in Figure 1, the distribution of the liquid crystal optics phase shift based on the quarter-wave plate method detection method of the embodiment of the present invention comprises the following steps:

S101: linearly polarized laser device, testing sample, quarter wave plate, microcobjective, the analyzer of hollow stepper motor universal stage, charge coupled cell are erected in coaxial light path, and allow laser successively by the center of each device, hollow stepper motor universal stage, charge coupled cell are connected to computer controlling center by data line simultaneously;

S102: the distance of adjustment microcobjective and testing sample, by the image of charge coupled cell, is adjusted to picture the most clear;

S103: the direction of the polarization direction of linearly polarized laser, analyzer is mutually vertical, and wherein analyzer analyzing direction sign is decided to be 0 degree of position of system perspective;

S104: by the adjustment of quarter wave plate optical axis direction at 0 degree or 90 degree, the direction of the optical axis of testing sample is arranged on 45 degree or 135 degree;

S105: drive analyzer to revolve turnback by computer controlling center control step universal stage, meanwhile, charge coupled cell obtains and obtains N frame gradation data I according to identical step angle _i(x, y);

S106: obtained each frame data I by charge coupled cell _iwhile (x, y), computer controlling center carries out data processing;

S107: the spatial resolution that directly can be improved test component by the raising enlargement ratio of microcobjective and the resolution of charge coupled cell; The phase shifting accuracy of detection can be improved by the frame per second of adjustment acquisition data; By to the magnified sweep of sample and analysis, accurately can obtain the N number of gradation data on sample on every bit position, avoid the impact of light intensity on diverse location, improve the frame per second obtaining data, increase the gradation data that every bit position is corresponding, thus the minimum value of this data and curves can be obtained more accurately, namely improve phase-detection precision.

In step S105, wherein subscript i=1,2,3 ..., N, (x, y) is the space element marking of charge coupled cell gradation data, and the angle of corresponding analyzer is θ _idata acquisition number N is relevant with final precision, and the precision of the larger detection of N is higher, is subject to the impact of charge coupled cell frame per second simultaneously, and N causes more greatly the reduction of detection speed, and N can be set as 50 ~ 200;

In step s 106, fourier algorithm implementation method realizes the acquisition of minimum value in curve as follows:

The angular frequency of curve ₀for definite value, the total angle rotated by analyzer determines, assuming that intermediate variable complex matrix X (x, y), and utilizes the gradation data of every bit (x, y) on the mode calculation sample of weighted sum to become conversion again wherein ω ₀=2, θ _iin units of radian, thus obtain this curve at ω by Euler's formula ₀real part when=2 and imaginary part respectively the curve of every bit position on sample is processed when often obtaining frame data, calculated curve actual frequency ω ₀real part and imaginary part.

Data acquisition is complete, obtain real part and the imaginary part of every bit position on sample, according to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, and sinusoidal curve initial phase and the total phase difference of pi of minimum value, survey the phase place of device in (x, y) position wherein: by the calculating of control center, complete the phase shift information of all location of pixels of inside, single visual field.

Specific embodiments of the invention:

As shown in Figure 1, the distribution of the liquid crystal optics phase shift based on the quarter-wave plate method detection method of the embodiment of the present invention comprises:

The present invention relates to the Fourier quarter-wave plate method realized in liquid crystal optics phase shift distribution detection; Comprise the following steps:

Step one: the analyzer of linearly polarized laser device, testing sample, quarter wave plate, microcobjective, stepper motor universal stage, charge coupled cell (CCD) are erected in coaxial light path, and allow laser successively by the center of each device, hollow stepper motor universal stage, charge coupled cell (CCD) are connected to computer controlling center by data line simultaneously;

Step 2: the distance of adjustment microcobjective and testing sample, by the image of charge coupled cell (CCD), is adjusted to picture the most clear;

Step 3: the direction of the polarization direction of linearly polarized laser, analyzer is mutually vertical, and wherein analyzer analyzing direction sign is decided to be 0 degree of position of system perspective;

Step 4: by the adjustment of quarter wave plate optical axis direction at 0 degree or 90 degree, the direction of the optical axis of testing sample is arranged on 45 degree or 135 degree;

Step 5: drive analyzer to revolve turnback by control center's control step universal stage, meanwhile, charge coupled cell (CCD) obtains and obtains N frame gradation data I according to identical step angle _i(x, y), wherein subscript i=1,2,3 ..., N, (x, y) is the space element marking of charge coupled cell (CCD) gradation data, and the angle of corresponding analyzer is θ _idata acquisition number N is relevant with final precision, and the precision of the larger detection of N is higher, and be subject to the impact of charge coupled cell (CCD) frame per second, N causes more greatly the reduction of detection speed simultaneously, and generally N can be set as between 50 ~ 200;

Step 6: obtaining each frame data I by charge coupled cell (CCD) _iwhile (x, y), computer controlling center carries out data processing, and as shown in Figure 2, step is as follows for Processing Algorithm flow process:

Assuming that intermediate variable complex matrix X (x, y), and the mode of weighted sum is utilized to calculate wherein ω ₀=2, θ _iin units of radian;

According to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, survey the phase place of device in (x, y) position wherein: ${\mathrm{\φ}}_X=\arctan \left[\frac{\mathrm{Im}\left[X\right]}{\mathrm{Re}\left[X\right]}\right];$ By the calculating of control center, complete the phase shift information of all location of pixels of inside, single visual field;

Step 7, directly can improve the spatial resolution of test component by the raising enlargement ratio of microcobjective and the resolution of charge coupled cell (CCD); The phase shifting accuracy of detection can be improved by the frame per second of adjustment acquisition data.

As shown in Figure 3, the embodiment of the present invention based on quarter-wave plate method liquid crystal optics phase shift distributed detection system primarily of: laser instrument 1, testing sample 2, microcobjective 3, quarter wave plate 4, analyzer and stepper motor 5, charge coupled cell 6, computer controlling center 7 form;

Laser instrument 1 for sending linearly polarized laser connects testing sample 2, testing sample 2 connects the microcobjective 3 being used for flourishing laser, microcobjective 3 connects the quarter wave plate 4 for obtaining data, quarter wave plate 4 connects analyzer and stepper motor 5, analyzer is connected charge coupled cell 6 with stepper motor 5, and analyzer is connected computer controlling center 7 with stepper motor 5 and charge coupled cell 6.

The principle of work of the liquid crystal optics phase shift distributed detection system based on quarter-wave plate method of the embodiment of the present invention: the shadow print image that the laser that the laser instrument 1 of linear polarization sends forms testing sample PHASE DISTRIBUTION successively after testing sample 2, microcobjective 3, quarter wave plate 4, analyzer and stepper motor 5 projects on the target surface of charge coupled cell (CCD) 6; The center of microcobjective 3, quarter wave plate 4, analyzer and high precision stepper motor 5, charge coupled cell (CCD) 6 is clear aperature, before testing sample 2 is placed on microcobjective 3, allow linearly polarized light perpendicular through.

Present invention achieves and high precision, high resolving power, detection are fast and automatically carried out to two-dimentional liquid crystal phase shifting device, phase-detection precision through experiment this invention known can reach 0.3 degree, the impact of the distribution and electrode separation etc. of introns in LCD phased array sample can be obtained, as table 1, Fig. 4, improve the resolution and precision that detect phased array PHASE DISTRIBUTION.

The phase delay testing result of table 1 standard quarter wave plate device

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (5)

1. based on a liquid crystal optics phase shift distribution detection method for quarter-wave plate method, it is characterized in that, should comprise based on the liquid crystal optics phase shift distribution detection method of quarter-wave plate method:

Step one, is erected in coaxial light path by linearly polarized laser device, testing sample, quarter wave plate, microcobjective, the analyzer of hollow stepper motor universal stage, charge coupled cell;

Step 2, the direction of the polarization direction of linearly polarized laser, analyzer is mutually vertical, and wherein analyzer analyzing direction sign is decided to be 0 degree of position of system perspective;

Step 3, by the adjustment of quarter wave plate optical axis direction at 0 degree or 90 degree, the direction of the optical axis of testing sample is arranged on 45 degree or 135 degree, testing sample and linearly polarized laser device, quarter wave plate, analyzer constitutes basic quarter wave plate method, the linearly polarized light that laser instrument sends is through the ordinary light and the extraordinary ray that are decomposed into certain phase differential during phased array sample, the polarized light of certain polarization direction is converted into again through quarter wave plate method, the angle changing of polarization direction is 1/2 of phase delay, rotate again analyzer again the change of polarization size of delustring to this linearly polarized light judge, thus obtain phase-delay quantity,

Step 4, the distance of adjustment microcobjective and testing sample, by the image of charge coupled cell, is adjusted to picture the most clear;

Step 5, drives analyzer to revolve turnback by computer controlling center control step universal stage, and while analyzer once often rotates, charge coupled cell obtains and obtains N frame gradation data I according to identical step angle _i(x, y), wherein i=(1,2,3,, the N) anglec of rotation that is analyzer, (x, y) is the point coordinate on sample, thus obtains N number of gradation data that on testing sample, each some position is corresponding;

Step 6, is obtaining each frame data I by charge coupled cell _iwhile (x, y), computer controlling center carries out data processing.

2. as claimed in claim 1 based on the liquid crystal optics phase shift distribution detection method of quarter-wave plate method, it is characterized in that, in step, allow laser successively by the center of each device, hollow stepper motor universal stage, charge coupled cell are connected to computer controlling center by data line simultaneously.

3. as claimed in claim 1 based on the liquid crystal optics phase shift distribution detection method of quarter-wave plate method, it is characterized in that, in step 5, wherein subscript i=1,2,3 ... N, (x, y) is the space element marking of charge coupled cell gradation data, and the angle of corresponding analyzer is that θ i data acquisition number N is relevant with final precision, the precision of the larger detection of N is higher, be subject to the impact of charge coupled cell frame per second, N causes more greatly the reduction of detection speed, and N is set as 50 ~ 200 simultaneously.

4., as claimed in claim 1 based on the liquid crystal optics phase shift distribution detection method of quarter-wave plate method, it is characterized in that, obtained each frame data I by charge coupled cell _iwhile (x, y), computer controlling center is carried out data processing method and is:

According to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, survey the phase place of device in (x, y) position wherein: ${\mathrm{\φ}}_X=\arctan \left[\frac{\mathrm{Im}\left[X\right]}{\mathrm{Re}\left[X\right]}\right];$ By the calculating of computer controlling center, complete the phase shift information of all location of pixels of inside, single visual field, fourier algorithm implementation method realizes the acquisition of minimum value in curve as follows:

The angular frequency of curve ₀for definite value, the total angle rotated by analyzer determines, assuming that intermediate variable complex matrix X (x, y), and utilizes the gradation data of every bit (x, y) on the mode calculation sample of weighted sum to become conversion again wherein ω ₀=2, θ _iin units of radian, thus obtain this curve at ω by Euler's formula ₀real part when=2 and imaginary part respectively the curve of every bit position on sample is processed when often obtaining frame data, calculated curve actual frequency ω ₀real part and imaginary part;

Data acquisition is complete, obtain real part and the imaginary part of every bit position on sample, according to the fourier series relation of cosine function, time domain amount of delay equals frequency domain with the product of angular frequency and prolongs mutually, and sinusoidal curve initial phase and the total phase difference of pi of minimum value, survey the phase place of device in (x, y) position wherein: by the calculating of control center, complete the phase shift information of all location of pixels of inside, single visual field.

5. the liquid crystal optics phase shift distributed detection system based on quarter-wave plate method, it is characterized in that, should comprise based on the liquid crystal optics phase shift distributed detection system of quarter-wave plate method: laser instrument, microcobjective, quarter wave plate, analyzer, stepper motor, charge coupled cell, computer controlling center;

Laser instrument for sending linearly polarized laser connects testing sample, testing sample connects the microcobjective being used for flourishing laser, microcobjective connects the quarter wave plate for obtaining data, quarter wave plate connects analyzer and stepper motor, analyzer is connected charge coupled cell with stepper motor, and analyzer is connected computer controlling center with stepper motor and charge coupled cell;

Laser instrument produces linearly polarized laser as the initial laser that phase delay does not occur in experiment, microcobjective carries out high resolution scanning to sample, dephased ordinary light and extraordinary ray are changed into the polarized light having certain polarization direction by quarter wave plate, change of polarized direction angular dimension equals 1/2 phase-delay quantity, stepper motor drives the accurate stepping of analyzer to obtain this polarized light through the light intensity situation of change of analyzer when different angles, and charge coupled cell collects experimental data to light intensity and delivers to computer controlling center and carry out data processing.