CN101561317B - System for measuring the influence of object to polarization state of transmitted beams with high precision and automation - Google Patents

Abstract

The invention discloses a system for measuring the influence of an object to polarization state of transmitted beams, which is especially applicable to occasions needing high-precision automatic measurement. Based on the polarization principle, the system adopts the technologies of locking detection, double light path compensation and self-adaptive amplification and the like, designs a reasonable and feasible optical-mechanical mechanism, utilizes a computer to control all rotating motors and electric platforms automatically and finally realizes the purpose of measuring the influence of the object to polarization state of transmitted beams with high precision and automation.

Description

A kind of high-precision automatic measuring target is to the system of transmitting beam polarization state influence

Technical field

The present invention relates to optical detective technology, refer in particular to the system of a kind of high-precision automatic measuring target the influence of transmitting beam polarization state.

Background technology

Polarization is a specific character of light, by to the studying for a long period of time of light polarization phenomenon, polarized-light technique has been widely used in multiple subject such as physics, chemistry, biology: for example utilize solution such as sucrose to have measurement solution pol that optical activity the makes saccharometer with the maturity of judging fruit etc.; Utilization has the image beam of mutual vertical polarization and the stereogram pictures such as three-dimensional film that form; Utilize and apply the engineering detecting method etc. that external force can produce the photoelastic effect of proportional birefringent phenomenon on the homogeneous materials such as glass.Along with people's deepening continuously to polarisation of light phenomenon understanding and research, polarization information is applied to the detection to target gradually, plays important effect in fields such as atural object remote sensing, atmospheric exploration, undersea detection, astrosurveillance, medical diagnosis, target detection, Flame Image Process and Military Application.

In polarization application and research process thereof, for obtaining the influencing characteristic of different target to polarized light, must be to measuring through the light beam polarization characteristic behind the interacting goals, and existing polarization state detection system has great limitation in the actual measurement process: " a kind of elliptical polarized light analytical equipment " of number of patent application 200720046210.X, thereby it in use adopts USB interface control single chip computer control total system, but this system is still just measured light polarization merely, target is not considered in the design the polarization application need of polarization state influence, and in detection, just adopt simple monochromatic light road photocell detection, influence the precision of actual detected." a kind of novel quick-speed elliptical polarized light measurement instrument " of number of patent application 200520040201.0, it in use adopts combination analyzer and two-dimensional CCD detector to obtain the optical parametric of material, considered and detected the influence of target light polarization, but in use still have some problems: 1, still adopt the mode of single channel direct current on measurement means, the precision of detection is not high; When 2, goal in research is to the influencing of light polarization, can only finish the polarimetry of one-dimensional, energy measurement isotropy homogeneous material can not satisfy the needs of using fully.

The present invention takes into full account actual polarization demands of applications, based on polarization theory, adopt technology such as phase-locked detection, double light path compensation, self-adaptation amplification, feasible mechanical-optical setup reasonable in design, utilize each electric rotating machine of computer controlled automatic and electric platforms, realize the purpose of high-accuracy intelligent measurement target the influence of transmitting beam polarization state.

Summary of the invention

The objective of the invention is to, detect at existing polarized light on the basis of pattern,, adopt rational technique to improve existing shortcoming, propose a kind of high-precision automatic and measure the system that the multidimensional target influences the transmitting beam polarization state in conjunction with polarization demands of applications now.

The technical scheme of whole polarization state detection system is:

Detect target as shown in Figure 1, form by lasing light emitter 1, attenuator 2, chopper 3, Amici prism 4, transmission-type object module 5, reflective object module 6, analyzer and electric rotating machine assembly 7, first PIN photodiode 8 and second PIN photodiode 11, prime amplifier 12, self-adaptation prime amplifier 10, lock-in amplifier 13, electric machine controller 14, computing machine 15 to the system principle synoptic diagram of polarization state influence.Computing machine, self-adaptation prime amplifier, prime amplifier, lock-in amplifier, electric machine controller, electric rotating machine and electric platforms, PIN photoelectric tube control and data signal with the electric connection mode transmission.Encapsulation is every photo structure between the total system device.

In precision control, native system has carried out corresponding design in the degree of stability of energy of light source and these two contents of precision of photoelectric measurement:

At first, light source adopts circularly polarized light, and emergent light is produced by the laser instrument of high-energy degree of stability, and the stability of lasing light emitter energy can guarantee that reference energy keeps relative stablizing in measuring the extinction ratio process in measuring process.Under the condition that the phase-locked precision of photoelectricity allows, attenuation multiple should lack as far as possible, be in higher relatively level thereby guarantee when measuring extinction ratio, to detect faint signal energy, can improve the precision of Detection of Weak Signals like this, thereby improve the actual measurement precision of extinction ratio.

Secondly, in the testing process of polarization extinction ratio, adopt the double light path penalty method.By Amici prism accurate pulsed light is divided into two bundles, the one tunnel is used for actual polarization extinction ratio measures, and another road is used for reference value and measures; When data processing, the result of actual measurement divided by reference value, is obtained the result of relative measurement, thereby reduce the influence that the energy of light source instability is brought.In testing process, can also adopt in the software processes that many groups are measured, abandoned being worth most, the data processing method of calculating mean value, drop to the influence of energy of light source degree of stability minimum.

Consider that existing system adopts the direct current detection mode, and direct current biasing can appear in photodetector more in working long hours, thereby influence the precision of input greatly.In polarization was used, extinction ratio measurement was the key that polarization state detects, and what mainly influence the extinction ratio measurement precision is exactly the measuring accuracy of feeble signal, and the precision of existing metering system obviously can not meet the demands.Adopt the technology of phase-locked amplification in the native system: the interchange light signal that the direct current light signal is become fixed frequency by chopper, the PIN photoelectric tube converts light signal to ac signal, after the prime amplifier amplification, the reference signal that lock-in amplifier transmits with chopper finally obtains high-precision measurement result with the phase-locked amplification of ac signal.

According to the needs that polarization is used, in actual detected, to wish to obtain the multidimensional information of target to the influence of transmitting beam polarization, the data of actual acquisition are bigger.So during to the measuring system layout of multidimensional, simultaneously rational design has been carried out in computer automation control.

According to detecting the difference of light through optical propagation direction behind the target material, system design transmission-type object module 5 and reflective object module 6.In the transmission-type object module, target 16 to be measured is placed on the first three-D electric platform 5.2, makes the part to be measured that can be radiated at target in the variation range of incidence point.Have three catoptrons in the reflective object module, the reflecting surface of preceding two catoptrons, first catoptron 6.1 and second catoptron 6.2 becomes 45 degree with incident ray, make the light of incident that one section translation take place in the horizontal direction; The reflecting surface keeping parallelism of the catoptron in back the 3rd catoptron 6.4 and target 16 is 45 degree with second polarizer and electric rotating machine assembly 6.5; The 3rd catoptron, second polarizer and electric rotating machine assembly 6.5 and target 16 are placed on the second three-D electric platform 6.3, make the part to be measured of the interior energy of the variation range coverage goal of incidence point.Though it is many that such design is wanted on the use device than usual, can guarantee that the back light path only one-dimensional translation need take place on level, just can realize the aligning of light path, in fact mechanical-optical setup has obtained simplifying greatly.

Prime amplifier in the actual detected circuit design adopts adaptive technique: by detecting the actual electric signal that is transmitted by the PIN photoelectric tube, automatically control the enlargement factor of amplifying circuit, output meets the pulse electrical signal that the lock-in amplifier input requires, thereby guarantees the robotization of electrical measurement process.Ray machine part in system, all adjust electric rotating machine and electric platforms that structure all adopts motor controller controls, thereby guarantee the robotization of mechanical adjustment process.

System controls whole measuring process by computer programming, obtain the angle and the displacement information of motor from electric machine controller, obtain the actual measured value of Photoelectric Detection from lock-in amplifier, and control signal is transferred to electric machine controller the motor adjustment process is carried out robotization control.Utilize the signal that obtains, finish data processing, just can obtain the polarization information of being concerned about in the application such as extinction ratio and polarization rotation angle by program.The present invention has the precision height, and the characteristics of robotization multidimensional measure can provide the multidimensional information of target to the influence of transmitting beam polarization state.

Description of drawings

Fig. 1 is the system principle synoptic diagram.

Fig. 2 is system's control and Measurement Algorithm process flow diagram.

Number in the figure: 1 is lasing light emitter, 2 is attenuator, 3 is chopper, 4 is Amici prism, 5 is that (5.1 is first polarizer and electric rotating machine assembly to the transmission-type object module, 16 is target, 5.2 be the first three-D electric platform), 6 is that (6.1 and 6.2 is reflecting surface becomes 45 degree with incident ray first catoptron and second catoptrons to reflective object module, 6.3 be the second three-D electric platform, 6.4 be the 3rd catoptron, 6.5 be second polarizer and electric rotating machine assembly, 16 is target), 7 is analyzer and electric rotating machine assembly, 8 is a PIN photoelectric tube, 9 is the one dimension electric platforms, 10 is the self-adaptation prime amplifier, 11 is the 2nd PIN photoelectric tube, and 12 is prime amplifier, and 13 is the binary channels lock-in amplifier, 14 is electric machine controller, and 15 is computing machine.Thick line is a light path among Fig. 1, and fine rule is a circuit.

Embodiment

System schematic of the present invention as shown in Figure 1, behind attenuator 2, decay to certain light intensity by lasing light emitter 1 emitting laser, form the accurate light signal that exchanges by chopper 3, be divided into the two-way light beam of determining the energy ratio through Amici prism 4 again: the one tunnel directly is converted into electric signal by 11 receptions of the 2nd PIN photoelectric tube, measures reference value (reference signal of lock-in amplifier is provided by the modulation signal of chopper) by lock-in amplifier phase-locked 13 after prime amplifier 12 amplifies; Another road is the actual detected light signal, adopt transmission-type object module 5 (passing through transmission target 16 again through first polarizer and electric rotating machine group 5.1 earlier) or reflective object module 6 (to become first catoptron 6.1 and 6.2 reflections of second catoptron of 45 degree earlier with incident ray through reflecting surface by detecting light through the characteristic decision of optical propagation direction behind the target material, reflect on the 3rd catoptron 6.4 surfaces parallel again with target surface, inclined to one side through second polarizer and 6.5 of electric rotating machine assemblies, reflect on target 16 surfaces at last), after passing through analyzer and 7 analyzings of electric rotating machine assembly then, be converted into electric signal after 8 receptions of the one PIN photoelectric tube, after self-adaptation prime amplifier 10 amplifies, measured the actual detected values by lock-in amplifier phase-locked 13.

System of the present invention further describes as follows:

1) main devices

A) laser instrument: the adjustable power fiber laser that Thorlabs company produces, model is S1FC780, wavelength 780nm;

B) polarizer/analyzer: the product of Thorlabs company, model are LPVIS100, its Specifeca tion speeification: service band is 600-1200nm; Polarization extinction ratio is 10000: 1; Caliber size is 25mm, and effective aperture is 90% of a bore; Playing inclined to one side analyzing angle is ± 20 °;

C) Amici prism: Thorlabs company model is the broadband beam splitter prism of BS011, and available band is 700-1100nm;

D) PIN photoelectric tube: Centronic company model is OSD15-5T, dark current 3nA, wavelength coverage 400-1050nm, peak spectral response 850nm, peak response rate 0.45A/W (V _R=12V);

E) prime amplifier: use AD795 chip design circuit voluntarily;

F) lock-in amplifier: the phase-locked anti-amplifier of Nanjing University's Detection of Weak Signals center HB-212 type binary channels two-phase, frequency of operation 5Hz-50kHz, full scale sensitivity 100nV-1V, reference signal input voltage range 100mV-10V, signal input mode voltage is single-ended;

G) electric rotating machine: the Shanghai friendship ties optical-fiber laser apparatus M52*1 of factory mesopore one dimension electric rotary table (360 degree scales can appoint revolve), the rating of electric machine 42 motors, mesa dimensions

Scale least count 0.2 degree, motor synchronizing operation resolution 0.0133 degree, repetitive positioning accuracy is less than 0.05 degree.

2) software section

Electric machine controller 14 is controlled one dimension rotary electric machine, the first three-D electric platform 5.2, the second three-D electric platform 6.3, the horizontal translation electric platforms 9 at first polarizers and electric rotating machine assembly 5.1, second polarizer and electric rotating machine assembly 6.5 and analyzer and electric rotating machine assembly 7 places, and obtains the angle and the positional information of rotary electric machine and electric platforms.Computing machine according to automated procedures setting issue the motor controller controls signal, and read information from electric machine controller and lock-in amplifier, according to the program of setting, calculate, thereby obtain net result.

The computer controlled measurement algorithm flow chart is as shown in Figure 2:

1, after program brings into operation, the initialization first three-D electric platform 5.2 or the second three-D electric platform 6.3;

2, mobile and horizontal translation electric platforms 9 is aligned (rise under the equidirectional situation of inclined to one side analyzing, measure light intensity and reach maximum) up to light path;

3, control first polarizer and electric rotating machine assembly 5.1 or second polarizer and 6.5 to initial angles of electric rotating machine assembly, control analyzer and 7 to initial angles of electric rotating machine assembly, finish 10 groups of measurements, control analyzer and electric rotating machine assembly 7 then and rotate a low-angle (precision can be made as 0.2 degree), each surveying work that repeats 10 groups is finished the rotation of half cycle up to analyzer and electric rotating machine assembly 7;

4, control analyzer and electric rotating machine assembly 7 to measure the angle of minimum value, measure 50 groups of data, revolve and turn 90 degrees (being defaulted as the maximal value angle), finish 50 groups of measurements, COMPUTER CALCULATION and store results;

5, control first polarizer and electric rotating machine assembly 5.1 or second polarizer and low-angle of electric rotating machine assembly 6.5 rotations (general precision can be made as 1 degree), repeat 3,4 steps, finish the rotation of half cycle up to first polarizer and electric rotating machine assembly 5.1 or second polarizer and electric rotating machine assembly 6.5;

6, the control first three-D electric platform 5.2 or low-angle of second three-D electric, 6.3 rotations (general precision can be made as 1 degree) repeat 2,5 steps, up to finishing the ranges of incidence angles that need measure;

7, the control first three-D electric platform 5.2 or second three-D electric 6.3 move a little translational movement (general precision can be made as 1cm), repeat 6 steps, up to the two-dimensional translation scanning of finishing target 16 surface range to be measured;

8, complete measuring process finishes.

Determine at target surface under the situation of incidence point, incident angle and incident light polarization direction, obtain the polarizing angle degree θ of polarizer slice; Measuring the analyzing angle θ of minimum voltage value _Min, obtain 50 groups of measuring voltage values, remove 5 minimum value of 5 maximal values, calculate mean value V _Min, obtain the magnitude of voltage that 50 groups of reference paths detect, remove 5 minimum value of 5 maximal values, calculating with reference to mean value is V _Min'; Revolving the analyzing angle θ that turn 90 degrees _Min+ 90 ° (being defaulted as the angle that detects maximum voltage value) obtains 50 groups of measuring voltage values, removes 5 minimum value of 5 maximal values, calculates mean value V _Max, obtain the magnitude of voltage that 50 groups of reference paths detect, remove 5 minimum value of 5 maximal values, calculating with reference to mean value is V _Max'.

The relative value of minimum voltage: ${\mathrm{\η}}_{\min }=\frac{V_{\min }}{{V_{\min }}^{\′}}.$

The relative value of maximum voltage: ${\mathrm{\η}}_{\max }=\frac{V_{\max }}{{V_{\max }}^{\′}}.$

The final polarization extinction ratio of measuring: $\mathrm{ER}=\frac{{\mathrm{\η}}_{\max }}{{\mathrm{\η}}_{\min }}.$

The polarization direction rotation angle: $\mathrm{\Δ\θ}=\mathrm{\θ}-({\mathrm{\θ}}_{\min }+\frac{\mathrm{\π}}{2}).$

Through the perfect measurement process, finally can obtain the influence situation of target surface each point to the polarized light of different incidence angles degree different polarization light direction.

Claims (3)

1. a high-precision automatic measuring target is to the system of transmitting beam polarization state influence, by lasing light emitter (1), attenuator (2), chopper (3), Amici prism (4), transmission-type object module (5), reflective object module (6), analyzer and electric rotating machine assembly (7), the one PIN photoelectric tube (8), the 2nd PIN photoelectric tube (11), self-adaptation prime amplifier (10), prime amplifier (12), binary channels lock-in amplifier (13), electric machine controller (14) and computing machine (15) are formed, and it is characterized in that: described system can measure the transmission or the polarization by reflection characteristic of target; Self-adaptation prime amplifier (10) in the described system can be adjusted enlargement factor automatically according to the input electrical signal that a PIN photoelectric tube (8) provides, make the electric signal that is input to lock-in amplifier (13) be in the work range of lock-in amplifier, realize that the robotization of system detects.

2. a kind of high-precision automatic measuring target according to claim 1 is to the system of transmitting beam polarization state influence, it is characterized in that: described transmission-type object module (5) is made up of first polarizer and electric rotating machine assembly (5.1), target (16), the first three-D electric platform (5.2), the first three-D electric platform (5.2) can drive target (16) and rotate translation in level and vertical plane on surface level.

3. a kind of high-precision automatic measuring target according to claim 1 is to the system of transmitting beam polarization state influence, it is characterized in that: described reflective object module (6) is become first catoptron (6.1) and second catoptron (6.2) of 45 degree with incident ray by reflecting surface, the second three-D electric platform (6.3), the 3rd catoptron (6.4), second polarizer and electric rotating machine assembly (6.5), target (16) is formed, keeping parallelism and fixing position relation between described the 3rd catoptron (6.4) and the target (16), described second polarizer and electric rotating machine assembly (6.5) are positioned between the 3rd catoptron (6.4) and the target (16); Described three-D electric platform (6.3) can drive the 3rd catoptron (6.4), second polarizer and electric rotating machine assembly (6.5) and target (16) is rotated translation in level and vertical plane on surface level.

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