CN100378445C - Intelligent synthesized measuring apparatus for half wave voltage of extinction ratio in crystal, and phase delay of wave plate - Google Patents

Abstract

A intelligent synthesized measuring apparatus for half wave voltage of extinction ratio in crystal, and phase delay of wave plate which is featured as setting a spectroscope in 45 degree to forward direction of light beam, setting polarizer, article to be tested, analyzer, the first photoelectric detector, the first demodulation and amplification circuit as well as the first A/D converter, a signal line connection computer of the first A/D converter in sequence at transmission direction of the spectroscope, the first output of the computer is rotated around optical axis by a first step motor driving analyzer, the second output of the computer is rotated around optical axis by a second step motor driving article to be tested; and an attenuator, the second photoelectric detector, the second demodulation and amplification circuit as well as the second A/D converter, a signal line connection computer of the second A/D converter in sequence at reflection direction of the spectroscope. The invention can not only complete integration measurement of a plurality of parameters, but also has characters of high measurement accuracy, good reliability, and convenient operation.

Description

The intelligent synthesized measuring apparatus of crystal extinction ratio half-wave voltage and wave plate phase delay

Technical field

The present invention is relevant with crystal, belongs to polarization optics physical detection instrument, the intelligent synthesized measuring apparatus of particularly a kind of crystal extinction ratio, half-wave voltage and wave plate phase delay.

Background technology

The extinction ratio of crystal and half-wave voltage are to weigh the important parameter of crystal optics performance, have reflected the defective that crystals may exist, and inhomogeneous etc. as internal stress, optics, the extinction ratio and the half-wave voltage of crystal are more little, illustrate that the optical quality of crystal is good more.The accuracy that crystal extinction ratio is measured directly influences development, production and the application of crystal.Equally,, bring a lot of troubles can for the driving power of Q-switch, before Q-switch finishing, the test screening of its half-wave voltage is very important if the half-wave voltage of crystal is very high.

Wave plate is one of fundamental sum optical element commonly used in the physical optics, in isolation, polarization interference, often needs accurately to measure the phase delay of wave plate.Along with modern industry and science and technology development, the effect that wave plate play more and more in optical instrument is important, more and more higher to the wave plate accuracy requirement, the accuracy detection of wave plate itself also becomes a vital task in the wave plate manufacturing.

The classic method of measuring crystal extinction ratio, half-wave voltage and wave plate phase delay is that the staff directly surveys light intensity with light power meter.This method complex operation step, measuring accuracy is low, and extinction ratio can only measure 10 ^-2Or 10 ^-3And just be in the laboratory applications stage, also there is not corresponding general measuring instrument on the home market at present, a lot of companies that produce crystal or polarizing device usually are by rule of thumb, and parameters such as the extinction ratio of usefulness artificial visually examine crystal and half-wave voltage just do not have real surveying instrument at all, measures of quantization also is far from being, so the precision when sample uses does not guarantee that reliability is very poor.

Summary of the invention

The technical problem to be solved in the present invention is that the precision of the complicacy, sample at above-mentioned prior art when using can not guarantee, can not finish automatically measurement, can not carry out the deficiencies in the prior art part such as comprehensive measurement, and the intelligent synthesized measuring apparatus of a kind of crystal extinction ratio, half-wave voltage and wave plate phase delay is provided.This general measuring instrument adopts computer control, not only can finish the composite measurement of a plurality of parameters at same instrument, and should have measuring accuracy height, good reliability, convenience operation, to improve efficiency of measurement greatly.

The technical solution used in the present invention is:

The intelligent synthesized measuring apparatus of a kind of crystal extinction ratio, half-wave voltage and wave plate phase delay, its formation is: a pulsed modulation light source, be 45 ° in the light beam working direction of this pulsed modulation light source and establish a spectroscope, in this spectroscopical transmission direction is the polarizer, testing sample, analyzer, first photodetector, first demodulation and amplifying circuit and first A/D converter successively, and the signal wire of this first A/D converter connects the first input end of computing machine; First output of this computing machine rotatablely moves around optical axis by the first step motor drive analyzer, and second output of this computing machine rotatablely moves around optical axis by the second step motor drive testing sample; At described spectroscopical reflection direction is attenuator, second photodetector, second demodulation and amplifying circuit, second A/D converter successively, and the signal wire of this second A/D converter connects second input end of computing machine.

Described testing sample platform is provided with two DC electrode and links to each other with a direct current power supply.

Introduce the measuring process of each parameter below respectively:

One, the measurement of crystal extinction ratio:

Modulated light source is behind spectroscope, and reflected light is as the reference light beam, behind attenuator, is received by second photodetector, separates the mediation amplifying circuit through second, and second A/D converter is sent into computing machine then, and obtaining with reference to light intensity signal after the Computer Processing is I _rTransmitted light beam is through the polarizer, crystal to be measured, analyzer, receive by first photodetector, separate through first and to be in harmonious proportion amplifying circuit and first A/D converter and to send into computing machine, obtain to survey light intensity signal after the Computer Processing, rotate analyzer, make the polarization direction of the polarizer and analyzer vertical, rotate crystal then, the largest light intensity signal of being surveyed is I _{⊥ max}Rotate analyzer again, make the polarizer parallel with the analyzer polarization direction, and then rotate crystal, the largest light intensity signal of being surveyed is I _{∥ max}So, the extinction ratio ρ of this crystal is:

$\mathrm{\ρ}=10\log (\left(\frac{I_{\⊥\max }}{I_r}\right)/\left(\frac{I_{//\max }}{I_r}\right))---\left(1\right)$

Two, the measurement of crystal half-wave voltage:

Uniaxial crystal with longitudinal electro-optic effect, its direction of growth are optical axis (Z axle) direction.Make the optical axis of crystal to be measured be parallel to incident ray, electric field is along optical axis direction.When impressed voltage is 0, light does not produce birefringence during through crystal to be measured.When impressed voltage is not V, by crystal γ ₆₃The phasic difference δ that causes of longitudinal electro-optic effect be:

$\mathrm{\δ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}{n}_o^3{\mathrm{\γ}}_{63}V---\left(2\right)$

In the following formula, n _oFor the O optical index V in the crystal to be measured is the impressed voltage size; γ ₆₃Vertical electrooptical coefficient for crystal to be measured.

During measurement, crystal to be measured is placed between the polarizer and the analyzer, at first rotates analyzer, makes the polarization direction of the polarizer and analyzer vertical, and then light is through behind the analyzer, the light intensity I that is detected by first photodetector _oFor:

I _o＝I ₁sin ²θsin ²(δ/2)(3)

In the formula, I ₁Be the light intensity behind the process polarizer; θ is the O light that produces in the polarization direction of the polarizer and the crystal or the angle between a certain polarized light of E light.When θ=45 °, during δ=π, output intensity maximum (I _Omax=I ₁), the voltage that applied this moment is exactly the half-wave voltage V of this crystal _π

Three, the measurement of wave plate phase delay:

The angle of the polarization direction of the orientation of wave plate to be measured and the polarization direction of the polarizer and analyzer is respectively α, β.By the elliptically polarized light of modulated light source outgoing, after spectroscope, transmitted light is received by first photodetector behind the polarizer, wave plate to be measured and analyzer, according to the principle of polarized light interference, and its light intensity I that detects as can be known _oFor:

I _o＝I ₁(cos ²αcos ²β+sin ²αsin ²β+2cosαcosβsinαsinβcosδ)(4)

In the formula, I ₁Be the light intensity behind the process polarizer; δ is the phase delay of wave plate to be measured.

Rotate by the first stepping driven by motor analyzer, make the polarization direction of analyzer be parallel to the polarization direction of the polarizer, then, driving wave plate to be measured by second stepper motor rotates, the polarization direction of the position angle of wave plate to be measured and the polarizer, analyzer is overlapped, when being α=β=0 °, the light intensity I that detect this moment _O1For:

I _o1＝I ₁(5)

Then, the saturating folk prescription that keeps the polarizer and analyzer rotates 45 ° to parallel with wave plate to be measured, i.e. α=β=45 °, the light intensity I that detect this moment _O2For:

$I_{o2}=\frac{I_1}{2}(1+\cos \mathrm{\δ})---\left(6\right)$

With (6), (7) formula simultaneous, obtain:

$\cos \mathrm{\δ}=\frac{2I_{o2}}{I_{o1}}-1---\left(7\right)$

That is:

$\mathrm{\δ}=\arccos (\frac{2I_{o2}}{I_{o1}}-1)---\left(8\right)$

Thereby obtain the phase delay δ of wave plate to be measured.

Intelligent control section: measure in the light path, by first photodetector pulse detection light intensity signal that detects is become ac signal, again through separating the mediation amplifying circuit, ac signal is demodulated into dc signal, carry out the A/D conversion then, and, promptly survey light intensity signal and send into computing machine and carry out data processing the result of A/D conversion.In the reference path, by second photodetector pulse that measures is become ac signal with reference to light intensity signal equally, and through after second demodulation amplification and the 2nd A/D conversion, and with the result that A/D changes, promptly send into computing machine with reference to light intensity signal and handle.Computing machine is according to the different parameters of institute's test sample product, control two stepper motors respectively, drive analyzer and testing sample and turn to the desired position around optical direction, simultaneously, computing machine carries out data processing respectively and demonstrates measurement result according to the measuring process of institute's test sample product parameter.

Technique effect of the present invention is as follows:

The present invention both can be used for the laboratory, also can be used for the real-time measurement that a plurality of parameters are carried out in the production scene, and light, mechanical, electrical integrated technique and Computer Control Technology are combined effectively.

Because what light source adopted is the pulsed modulation light source, convert light intensity signal to ac signal through first photodetector, need demodulator circuit to carry out demodulation, ac signal is demodulated into dc signal, and after direct current amplification and A/D conversion, carry out data processing and display result by computing machine.

Because the present invention has adopted modulated light source, rather than with traditional DC light source, has not only eliminated the influence of photodetector dark current, and, reduced the influence of parasitic light, improved measuring accuracy greatly.

The present invention has adopted software to remove law technology, is meant: the light that modulated light source is sent is behind 45 ° of spectroscopes, and transmitted light is as measuring beam, pass through the polarizer, testing sample and analyzer respectively after, survey light intensity by first photodetector; Reflected light is obtained with reference to light intensity by second photodetector through attenuator as the reference light beam.After two paths of signals passes through demodulator circuit, amplifying circuit and A/D change-over circuit respectively, send into computing machine and carry out data processing, computing machine is measuring light intensity signal as molecule, with reference to light intensity signal as denominator, the two does division arithmetic.This computing particularly when surveying faint light intensity, has greatly reduced the influence of light source fluctuation.The measuring accuracy that makes crystal extinction ratio is by 10 ^-3Bring up to 10 ^-6, even higher.

In a word, intelligent synthesized measuring apparatus of the present invention has been realized light, mechanical, electrical and the integrated effective combination of computing machine, have measuring accuracy height, good reliability and characteristics easy and simple to handle, improved detection efficiency, have certain market significance crystal or corresponding polarizing device.The Computer Control Technology that is adopted has not only improved the measuring accuracy and the reliability of instrument, and plays a role in promoting for the raising of domestic Artificial Intelligence Instrument level.

Description of drawings

Fig. 1 is the light channel structure synoptic diagram of general measuring instrument of the present invention.

Fig. 2 is the synoptic diagram of the present invention's impressed DC voltage when measuring crystal half-wave voltage to be measured

Fig. 3 is generally speaking, and the angle of the polarization direction of the orientation of wave plate to be measured and the polarizer 3 and the polarization direction of analyzer 5 is respectively α, β synoptic diagram

Embodiment

Please refer to Fig. 1 earlier, Fig. 1 is the light channel structure synoptic diagram of general measuring instrument of the present invention, as seen from the figure, the formation of the intelligent synthesized measuring apparatus of crystal extinction ratio half-wave voltage of the present invention and wave plate phase delay is: a pulsed modulation light source 1, be 45 ° in the light beam working direction of this pulsed modulation light source 1 and establish a spectroscope 2, transmission direction at this spectroscope 2 is the polarizer 3, testing sample 4, analyzer 5, first photodetector 6, first demodulation and the amplifying circuit 7 and first A/D converter 8 successively, and the signal wire of this first A/D converter 8 connects the first input end of computing machine 9; First output of this computing machine 9 drives analyzer 5 by first stepper motor 10 and rotatablely moves around optical axis, and second output of this computing machine 9 drives testing sample 4 by second stepper motor 11 and rotatablely moves around optical axis; Reflection direction at described spectroscope 2 is attenuator 12, second photodetector 13, second demodulation and amplifying circuit 14, second A/D converter 15 successively, and the signal wire of this second A/D converter 15 connects second input end of computing machine 9.

Described testing sample platform is provided with two DC electrode and links to each other with a direct current power supply.

The course of work of the present invention:

Utilize the present invention to measure the detailed process of crystal extinction ratio:

Modulated light source 1 is behind spectroscope 2, and reflected light is as the reference light beam, behind attenuator 12, receive by second photodetector 13, separate through second and be in harmonious proportion amplifying circuit 14 second A/D converters 15, send into computing machine 9 then and carry out data processing, the reference light intensity signal after the processing is I _rTransmitted light beam is through the polarizer 3, crystal 4 to be measured, analyzer 5, received by first photodetector 6, through first demodulation and amplifying circuit 7, first A/D converter 8, sends into computing machine 9 then and carries out data processing; At first rotating analyzer 5, make the polarizer 3 vertical with analyzer 5 polarization directions, rotate crystal 4 to be measured then, make first photodetector 6 detect the largest light intensity signal, at this moment, is I by the signal after the Computer Processing _{⊥ max} Rotate analyzer 5 again, make the polarizer 3 parallel with analyzer 5 polarization directions, and then rotate crystal 4 to be measured, the largest light intensity signal that first photodetector 6 is detected at this moment, is I by the signal after the Computer Processing _{∥ max}Then, computing machine 9 calculates according to above-mentioned formula (1)

$\mathrm{\ρ}=10\log (\left(\frac{I_{//\max }}{I_r}\right)/\left(\frac{I_{\⊥\max }}{I_r}\right))$

Can obtain the extinction ratio of crystal to be measured.

Two, utilize the present invention to measure the detailed process of crystal half-wave voltage:

Fig. 2 is that the present invention measures the wave plate of wave plate phase delay and the schematic diagram of impressed DC voltage, at first rotate analyzer 5, make polarization direction vertical of the polarization direction of analyzer 5 and the polarizer 3, put into crystal 4 to be measured then, and make impressed voltage begin to increase gradually from 0V, rotate crystal to be measured while increasing, the minimum intensity of light value that first photodetector 6 is detected remains unchanged, at this moment, O light or e polarisation of light direction in the birefringence that expression is caused by photoelectric effect overlap with the polarization direction of the polarizer 3 and analyzer 5 respectively, then, again with 45 ° of Crystal Rotation to be measured, O light that produces in the polarization direction of the expression polarizer 3 and the crystal 4 to be measured or the angle theta between a certain polarized light of e light have been 45 °, then, again impressed voltage is reduced to 0V, and begin to increase gradually from 0V, the voltage magnitude that every increase is certain, by computer recording and the signal of handling a time first photodetector 6 detecting, when this signal reached maximum, the amplitude of impressed voltage was the half-wave voltage of this crystal 4 to be measured.

Three, utilize the detailed process of apparatus measures of the present invention wave plate phase delay to be measured:

Fig. 3 is generally speaking, and the angle of the polarization direction of the orientation of wave plate to be measured and the polarizer 3 and the polarization direction of analyzer 5 is respectively α, β synoptic diagram.Generally speaking, the angle of the polarization direction of the polarization direction of the orientation of wave plate 4 to be measured and the polarizer 3 and analyzer 5 is respectively α, β.Measuring process:

At first driving analyzer 5 by first stepper motor 10 rotates, the light intensity maximum that first photodetector 6 is detected, this moment, analyzer 5 was parallel with the polarization direction of the polarizer 3, put into wave plate 4 to be measured then, and by second stepper motor, 11 drives wave plate 4 rotations to be measured, and the light intensity maximum that first photodetector 6 is detected, the polarization direction of the position angle of wave plate 4 to be measured and the polarizer 3 and analyzer 5 overlaps at this moment, be α=β=0 °, the signal after being handled by computing machine 9 is I _O1Then, drive wave plate 4 to be measured by second stepper motor 11 and rotate 45 °, i.e. α=β=45 °, the signal after being handled by computing machine 9 is I _O2At last, computing machine 9 calculates according to formula (8),

$\mathrm{\δ}=\arccos (\frac{2I_{o2}}{I_{o1}}-1)$

Can obtain the phase delay δ of wave plate to be measured.

Claims (1)

1. the general measuring instrument of an intelligent crystal extinction ratio, half-wave voltage and wave plate phase delay, be characterised in that its formation: a pulsed modulation light source (1), be 45 ° in the light beam working direction of this pulsed modulation light source (1) and establish a spectroscope (2), transmission direction at this spectroscope (2) is the polarizer (3), testing sample (4), analyzer (5), first photodetector (6), first demodulation and amplifying circuit (7) and first A/D converter (8) successively, and the signal wire of this first A/D converter (8) connects the first input end of computing machine (9); First output of this computing machine (9) drives analyzer (5) by first stepper motor (10) and rotatablely moves around optical axis, and second output of this computing machine (9) drives testing sample (4) by second stepper motor (11) and rotatablely moves around optical axis; Reflection direction at described spectroscope (2) is attenuator (12), second photodetector (13), second demodulation and amplifying circuit (14), second A/D converter (15) successively, the signal wire of this second A/D converter (15) connects second input end of computing machine (9), described testing sample (4) places on the testing sample platform, this testing sample platform is provided with two DC electrode and links to each other with a direct current power supply, applies DC voltage for testing sample (4);

Described computing machine (9) is controlled and to carry out the process of data processing as follows:

1) measurement of crystal extinction ratio:

Pulsed modulation light source (1) is behind spectroscope, folded light beam is as the reference light beam, behind attenuator, receive by second photodetector (13), separate mediation amplifying circuit (14) through second, second A/D converter (15) is sent into computing machine (9) then, and it is I with reference to light intensity signal that computing machine (9) is handled the back acquisition _r

Transmitted light beam is through the polarizer (3), crystal to be measured (4), analyzer (5), receive by first photodetector (6), separate through first and to be in harmonious proportion amplifying circuit (7) and first A/D converter (8) and to send into computing machine (9), computing machine (9) is handled the back and is obtained to survey light intensity signal, rotate analyzer (5), make the polarizer (3) vertical with the polarization direction of analyzer (5), rotate crystal to be measured (4) then, the largest light intensity signal of being surveyed is I _{⊥ max}Rotate analyzer (5) again, make the polarizer (3) parallel with analyzer (5) polarization direction, and then rotate crystal to be measured (4), the largest light intensity signal of being surveyed is I _//max, so, the extinction ratio ρ of this crystal to be measured (4) is:

$\mathrm{\ρ}=10\log (\left(\frac{I_{\⊥\max }}{I_r}\right)/\left(\frac{I_{//\max }}{I_r}\right));$

2) measurement of crystal half-wave voltage to be measured:

Crystal to be measured (4) optical axis is parallel to incident ray, electric field is along optical axis direction, impressed voltage, O light that in the polarization direction of the polarizer (3) and crystal to be measured (4), produces or angle theta=45 between a certain polarized light of E light, during the phasic difference δ that is caused by the longitudinal electro-optic effect of crystal to be measured=π, the voltage that is applied is exactly the half-wave voltage V of this crystal _π

3), the measurement of wave plate phase delay:

The phase delay of wave plate to be measured is:

$\mathrm{\δ}=\arccos (\frac{{2I}_{o2}}{I_{o1}}-1)$

In the formula: I _O1For the polarization direction of the position angle of wave plate to be measured (4) and the polarizer (3), analyzer (5) overlaps, i.e. α=β=0 o'clock, the light intensity that detects,

I _O2For the saturating folk prescription that keeps the polarizer (3) and analyzer (5) to parallel, with 45 ° of wave plate to be measured (4) rotations, i.e. α=β=45 o'clock, the light intensity that detects.

Images