CN205317939U - A differential detection system for laser velocimeter - Google Patents

Abstract

The utility model provides a differential detection system for laser velocimeter, including the laser instrument, the first beam splitter be connected with this laser instrument light path, second beam splitter and the first speculum be connected with this first beam splitter light path, third beam splitter and the chopper be connected with second beam splitter light path, the first detector and the the second mirror that are connected with third beam splitter light path, the second detector of being connected with the the second mirror light path, first speculum with third beam splitter light path is connected, the output of first detector with difference amplifier's an input is connected, the second detector with another input of difference amplifier is connected. The utility model has the advantages of as follows: light energy that can make full use of laser can improve laser velocimeter's detection sensitivity and precision, makes it become easy in well remote measurement field and realizes.

Description

A kind of differential detection system for laser velocimeter

Technical field

This utility model relates to kind of a differential detecting devices, particularly to a kind of differential detection system for laser velocimeter.

Background technology

Traditional laser velocimeter is all adopt single detector to constitute common Heterodyne Detection System, this optical heterodyne detection technology not only has that detectivity is strong, conversion gain is high, filtering performance is good, stability high, can also the information such as the amplitude of detectable signal, intensity, phase place, be widely used in the detection field of small-signal. But the insufficient sensitivity that this common Heterodyne Detection System has following defects that (1) laser velocimeter is high, medium and long distance measures signal difference, lossing signal is serious, and this makes common Heterodyne Detection System can not meet the requirement to detection accuracy and sensitivity in some field; (2) utilization rate of laser light energy is low, causes energy dissipation, and noise is big; (3) light source power size in laser velocimeter and stability requirement thereof is high, cost is greatly improved.

Summary of the invention

The technical problems to be solved in the utility model, being in that a kind of differential detection system for laser velocimeter of offer, improves the distance of the precision of detection, sensitivity and detection by this differential detection system.

This utility model is achieved in that a kind of differential detection system for laser velocimeter, including laser instrument, the first beam splitter, the second beam splitter, the 3rd beam splitter, chopper, the first reflecting mirror, the second reflecting mirror, the first detector, the second detector and difference amplifier; Described laser instrument is all-solid state continuous laser, the green glow that single-frequency output wavelength is 532nm of laser instrument;

Described first beam splitter is arranged on the front end of described laser instrument, and the beam Propagation that described laser instrument sends is divided into the first transmission light and the first reflection light two-way light to described first beam splitter; Described first transmission optical transport is to described first reflecting mirror, and after this first reflecting mirror reflects, transmission forms reference light to described 3rd beam splitter, is provided with one for regulating the attenuator of reference light power between described first reflecting mirror and the 3rd beam splitter;Described first reflected light pass is divided into the second transmission light and the second reflection light two-way light to described second beam splitter, and wherein, described second reflection light is invalid light; Described second transmission optical transport returns the scattering light carrying velocity information to described chopper, and this transmission of stray light is divided into the 3rd transmission light and the 3rd reflection light two-way light to described second beam splitter, and wherein, described 3rd transmission light is invalid light; Described 3rd reflected light pass forms flashlight to described 3rd beam splitter;

Reference light is divided into the 4th transmission light and the 4th reflection light two-way light after described 3rd beam splitter, flashlight is divided into the 5th transmission light and the 5th reflection light two-way light after described 3rd beam splitter, wherein, the input of described 4th reflection light and the 5th transmission optical transport extremely described first detector; Described 4th transmission light and the 5th reflected light pass are to described second reflecting mirror, and transmit the input to described second detector after this second reflecting mirror reflects;

The outfan of described first detector is connected with an input of described difference amplifier, and described second detector is connected with another input of described difference amplifier.

Further, the splitting ratio of the first beam splitter, the second beam splitter and the 3rd beam splitter is 50:50, and absorbance is 0.

The utility model has the advantage of:

1, take full advantage of the light energy of laser, improve detectivity and the certainty of measurement of laser velocimeter so that it is become easy realization in medium and long distance fields of measurement; The fluctuation of light source power is without affecting certainty of measurement and sensitivity simultaneously, and this makes velocity-measuring system that the requirement of light source power stability be substantially reduced;

2, the application differential detection system is applied in Laser Doppler Velocimeter, can further improve the sensitivity of Laser Doppler Velocimeter;

3, the signal of telecommunication of difference amplifier difference gained achieves the amplitude of AC signal in output signal and doubles, direct current signal is eliminated, both the electric current of intermediate frequency comprising object movable information it had been exaggerated, greatly suppress again the shot noise of detector and the noise of amplifying circuit, the interference that signal is caused by noise can be reduced, be effectively improved certainty of measurement.

Accompanying drawing explanation

This utility model is further described with reference to the accompanying drawings in conjunction with the embodiments.

Fig. 1 is the present invention light path principle figure for the differential detection system of laser velocimeter.

Detailed description of the invention

Refer to shown in Fig. 1, a kind of differential detection system for laser velocimeter, by being applied in laser doppler velocimeter system by this differential detection system, it is possible to measures the speed of any point tangential motion on chopper. Described differential detection system includes laser instrument the 1, first beam splitter the 2, first reflecting mirror 3, attenuator the 4, second beam splitting 5, chopper the 6, the 3rd beam splitter the 7, second reflecting mirror the 8, first detector the 91, second detector 92 and difference amplifier 10; Described laser instrument 1 is all-solid state continuous laser, the green glow that single-frequency output wavelength is 532nm of laser instrument 1, and this laser instrument 1 not only has the advantages such as low phase noise, the linearity be good, and has good polarization characteristic; Described first detector 91 is identical with the second detector 92 parameter.

The splitting ratio of described first beam splitter the 2, second beam splitter 5 and the 3rd beam splitter 7 is 50:50, and absorbance is 0. According to known optical knowledge, light beam is after beam splitter, and its transmission light has following relation with reflection light:

|T|²+|R|²=1;

$\left|{\mathrm{\φ}}_R-{\mathrm{\φ}}_T\right|=\frac{\mathrm{\π}}{2};$

Wherein, T represents that absorbance, R represent reflectance, φ_RRepresent the phase place of reflectance, φ_TRepresenting the phase place of absorbance, namely the absorbance of lossless BS and the quadratic sum of reflectance are 1, and have between reflectance and absorbancePhase contrast.

Described first beam splitter 2 is arranged on the front end of described laser instrument 1, and light beam 11 transmission that described laser instrument 1 sends is divided into the first transmission light 21 and the first reflection light 22 two-way light to described first beam splitter 2; Described first transmission light 21 transmission extremely described first reflecting mirror 3, and transmission to described 3rd beam splitter 7 forms reference light after this first reflecting mirror 3 reflects, described attenuator 4 is arranged between described first reflecting mirror 3 and the 3rd beam splitter 7, in use, this attenuator 4 can be passed through and regulate the power of reference light, so that reference light and flashlight, at the first detector 91 and the second detector 92, good mixing phenomenon occurs, it also is able to reduce the local oscillator noise of reference light simultaneously. Reference light is not subject to any modulation in the process formed, and its electric field component is represented by:

E_r=E_r0cos(2πf_rt+φ_r);

Wherein f_rRepresent the frequency of reference light; φ_rRepresent the initial phase of reference light.

Described first reflection light 22 transmission is divided into the second transmission light 51 and the second reflection light (not shown) two-way light to described second beam splitter 5, and wherein, described second reflection light is invalid light, does not note down; Described second transmission light 51 transmission returns the scattering light 61 carrying velocity information to described chopper 6, and the rotation of chopper 6 can make the frequency of scattering light 61 change, and carries required velocity information in the scattering light 61 therefore returned; The transmission of this scattering light 61 is divided into the 3rd transmission light (not shown) and the 3rd reflection light 611 two-way light to described second beam splitter 5, and wherein, described 3rd transmission light is invalid light, does not note down; Described 3rd reflection light 611 transmission forms flashlight to described 3rd beam splitter 7; The electric field component of this flashlight is represented by:

E_s=E_s0cos(2πf_st+φ_s);

Wherein f_sRepresent the frequency of flashlight; φ_sRepresent the initial phase of flashlight.

Reference light is divided into the 4th transmission light 712 and the 4th reflection light 711 two-way light after described 3rd beam splitter 7, flashlight is divided into the 5th transmission light 722 and the 5th reflection light 721 two-way light after described 3rd beam splitter 7, wherein, the input of described 4th reflection light 711 and the 5th transmission light 722 transmission extremely described first detector 91; Described 4th transmission light 712 and the 5th reflection light 721 transmission are to described second reflecting mirror 8, and transmit the input to described second detector 92 after this second reflecting mirror 8 reflects;

Described 4th reflection light 711 and the 5th transmission light 722 will be mixed after entering the first detector 91 on the first detector 91, described 4th transmission light 712 and the 5th reflection light 721 will be mixed after entering the second detector 92 on the second detector 92, it is possible to derive the output current signal i of the first detector 91₁Output current signal i with the second detector 92₂;

Wherein, B is photoelectric conversion factors, is numerically equal toη is the quantum efficiency of detector, and e is electronic charge, and h ν is single photon energy. i₁And i₂The difference of expression formula is that, the phase place (φ brought by the 3rd beam splitter 7 in cross term_T-φ_R) in two formulas, symbol is contrary, is pi/2 according to reflectance and absorbance phase contrast it can be seen that current signal i₁And i₂There is the phase contrast of 180 °.

The outfan of described first detector 91 is connected with an input of described difference amplifier 10, and described second detector 92 is connected with another input of described difference amplifier 10.Based on current signal i₁And i₂There is the phase contrast of 180 °, after difference processing, it is possible to achieve in output signal, the amplitude of AC signal doubles, and direct current signal is eliminated. Therefore, can obtain comprising the current intermediate frequency signal i of object movable information after difference amplifier 10 difference processing:

I=BE_r0E_s0sin[2π(f_s-f_r)t+(φ_r-φ_s)];

After current intermediate frequency signal i is finally completed signals collecting by data collecting card and is done follow-up signal process, the frequency of differential signal can be obtained, i.e. Doppler frequency, owing to Doppler frequency is directly proportional to speed of moving body, so the Doppler frequency according to gained can calculate the speed of the tangential motion of tested point on chopper.

In sum, this utility model has the advantages that

1, take full advantage of the light energy of laser, improve detectivity and the certainty of measurement of laser velocimeter so that it is become easy realization in medium and long distance fields of measurement; The fluctuation of light source power is without affecting certainty of measurement and sensitivity simultaneously, and this makes velocity-measuring system that the requirement of light source power stability be substantially reduced;

2, the application differential detection system is applied in Laser Doppler Velocimeter, can further improve the sensitivity of Laser Doppler Velocimeter;

3, the signal of telecommunication of difference amplifier difference gained achieves the amplitude of AC signal in output signal and doubles, direct current signal is eliminated, both the electric current of intermediate frequency comprising object movable information it had been exaggerated, greatly suppress again the shot noise of detector and the noise of amplifying circuit, the interference that signal is caused by noise can be reduced, be effectively improved certainty of measurement.

Although the foregoing describing detailed description of the invention of the present utility model; but those familiar with the art is to be understood that; we are merely exemplary described specific embodiment; rather than for the restriction to scope of the present utility model; those of ordinary skill in the art, in the equivalent modification made according to spirit of the present utility model and change, should be encompassed in scope of the claimed protection of the present utility model.

Claims (2)

1. the differential detection system for laser velocimeter, it is characterised in that: include laser instrument, the first beam splitter, the second beam splitter, the 3rd beam splitter, chopper, the first reflecting mirror, the second reflecting mirror, the first detector, the second detector and difference amplifier; Described laser instrument is all-solid state continuous laser, the green glow that single-frequency output wavelength is 532nm of laser instrument;

Described first beam splitter is arranged on the front end of described laser instrument, and the beam Propagation that described laser instrument sends is divided into the first transmission light and the first reflection light two-way light to described first beam splitter; Described first transmission optical transport is to described first reflecting mirror, and after this first reflecting mirror reflects, transmission forms reference light to described 3rd beam splitter, is provided with one for regulating the attenuator of reference light power between described first reflecting mirror and the 3rd beam splitter; Described first reflected light pass is divided into the second transmission light and the second reflection light two-way light to described second beam splitter, and wherein, described second reflection light is invalid light; Described second transmission optical transport returns the scattering light carrying velocity information to described chopper, and this transmission of stray light is divided into the 3rd transmission light and the 3rd reflection light two-way light to described second beam splitter, and wherein, described 3rd transmission light is invalid light; Described 3rd reflected light pass forms flashlight to described 3rd beam splitter;

Reference light is divided into the 4th transmission light and the 4th reflection light two-way light after described 3rd beam splitter, flashlight is divided into the 5th transmission light and the 5th reflection light two-way light after described 3rd beam splitter, wherein, the input of described 4th reflection light and the 5th transmission optical transport extremely described first detector; Described 4th transmission light and the 5th reflected light pass are to described second reflecting mirror, and transmit the input to described second detector after this second reflecting mirror reflects;

The outfan of described first detector is connected with an input of described difference amplifier, and described second detector is connected with another input of described difference amplifier.

2. a kind of differential detection system for laser velocimeter according to claim 1, it is characterised in that: the splitting ratio of the first beam splitter, the second beam splitter and the 3rd beam splitter is 50:50, and absorbance is 0.