CN102829729A - Method for aliasing polarizations of high-gain laser displacement sensor - Google Patents
Method for aliasing polarizations of high-gain laser displacement sensor Download PDFInfo
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- CN102829729A CN102829729A CN2012103236036A CN201210323603A CN102829729A CN 102829729 A CN102829729 A CN 102829729A CN 2012103236036 A CN2012103236036 A CN 2012103236036A CN 201210323603 A CN201210323603 A CN 201210323603A CN 102829729 A CN102829729 A CN 102829729A
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Abstract
The invention relates to a method for aliasing the polarizations of a high-gain laser displacement sensor, which comprises a double-frequency laser, a photoelectric conversion circuit, a singlechip, a piezoelectric ceramics and a piezoelectric ceramics drive circuit, wherein the double-frequency laser comprises a laser gain tube, an output mirror and an anti-reflection window, the outer part of the output mirror is provided with a Wollaston prism which is vertical to the laser transmission direction, and a first photoelectric detector and a second photoelectric detector are correspondingly arranged along the light-emitting direction of the Wollaston prism respectively; the Wollaston prism is formed by adhering a first right-angle prism and a second right-angle prism along the inclined planes, the optical axes of the first right-angle prism and the second right-angle prism are vertical to each other and are vertical to the face normal of an incident face; and the method is characterized in that the Wollaston prism, the first photoelectric detector and the second photoelectric detector are used as a whole to rotate at the angular velocity of omega by taking the laser which is sent out by the double-frequency laser as an axis, and an x light and a y light which are sent out by the Wollaston prism are respectively received by the first photoelectric detector and the second photoelectric detector. The method can be widely applied in the laser displacement measured signal processing process.
Description
Technical field
The present invention relates to a kind of optical signal processing method of laser displacement sensor, particularly about a kind of polarization aliasing method of high gain lasers displacement transducer.
Background technology
As shown in Figure 1, when adopting laser displacement sensor to carry out displacement measurement, when two-frequency laser output power hour (low gain); In the process that piezoelectric ceramics voltage rises and voltage descends, because the long variation in chamber, o light is significantly different with e light appearance order; O light and e light have two light intensity to equate in each half-wavelength in the cycle point; Be called high isocandela point and hang down the isocandela point, when high isocandela point with hang down longitudinal gap between the isocandela point when big, circuit signal is handled relatively easy.For example: the patent No. is ZL200910076308.3; Name is called the Chinese patent of " the 1152nm wavelength helium neon laser nano is surveyed chi "; Adopting output light is the core of the infrared light laser instrument of 1152nm wavelength as displacement transducer, makes that range can be extended to more than the 100mm under the constant condition of resolution; Utilize the high-gain of infrared light laser instrument, realize non-contact measurement.As shown in Figure 2, its circuit signal processing procedure is: power tuning curve that curve is an o light wherein, and another curve is the power tuning curve of e light; At first with the whole amplification of signal, the longitudinal gap between high isocandela point F and the low isocandela point G is bigger, and A～E representes that the complete cycle of a bright dipping bandwidth is divided into quarter among the figure; Be AB=BC=CD=DE, signal Processing is provided with a threshold value H between high isocandela point F and low isocandela point G for ease; Only the signal more than the threshold value H is handled the realization displacement measurement, wherein, the AB section has only o light; BC is the mixed light of o light and e light, and CD has only e light, and DE is a no light zone; A～E representes that the chamber mirror moves λ/2, and then division such as four are not represented λ/8, promptly realizes four segmentations in the half-wavelength.
From actual measurement, for the lower-powered displacement measurement system of two-frequency laser, on general guide rail linearity level, the chamber mirror moves in the scope of 10～20mm two-frequency laser can bright dipping, and light intensity is unstable; When continue strengthening moving range, two-frequency laser just can't bright dipping, so during actual measurement; Should select the bigger two-frequency laser of output power to carry out displacement measurement; But along with the two-frequency laser output power constantly increases, the two linearly polarized light o light and the e light of two-frequency laser output can't significantly separate at adjacent high and low isocandela point place, especially when the two-frequency laser output power is big; Adjacent high and low two isocandela point light intensity maybe be very close; Cause like this when adopting above-mentioned Nano-meter Measurement Ruler setting threshold method that signal is handled, causing miscount easily, thereby causing bigger measuring error.As shown in Figure 3; Through power tuning curve shown in Figure 3 is amplified observation; The signal voltage of 2 place's isocandela points is not equal fully in the one-period, but certain voltage difference is arranged, and the absolute voltage difference of observing 2 adjacent isocandela points among Fig. 3 and Fig. 1 simultaneously is close; For no other reason than that the overall magnitude of signal is bigger among Fig. 3; It is more approaching that two isocandelas point amplitude shows, the overall magnitude of signal is significantly dwindled if therefore can make the voltage difference of adjacent 2 isocandela points remain unchanged, and so just can make that just isocandela point is remarkable separates.
Summary of the invention
To the problems referred to above; The purpose of this invention is to provide a kind of when adopting high-power two-frequency laser to carry out displacement measurement; The o light of two-frequency laser output and the adjacent high and low isocandela point of e light are significantly separated, effectively avoid the polarization aliasing method of the high gain lasers displacement transducer of big measuring error.
For realizing above-mentioned purpose; The present invention takes following technical scheme: a kind of polarization aliasing method of high gain lasers displacement transducer; It comprises two-frequency laser, photoelectric switching circuit, single-chip microcomputer, piezoelectric ceramics and driver circuit for piezoelectric ceramics; Said two-frequency laser comprises laser gain pipe, outgoing mirror and anti-reflection window; Said outgoing mirror arranged outside has the wollaston prism vertical with the laser propagation direction, and the light direction of corresponding said wollaston prism is respectively arranged with first photodetector and second photodetector; Said wollaston prism is to be bonded along the inclined-plane by first right-angle prism and second right-angle prism, and the optical axis of said first right-angle prism and said second right-angle prism is orthogonal and all perpendicular to the face normal of the plane of incidence; It is characterized in that: with said wollaston prism, first photodetector and second photodetector is an anglec of rotation ω with said two-frequency laser emitting laser as a whole; Make the pairwise orthogonal linearly polarized light that impinges perpendicularly on said first right-angle prism through said two-frequency laser; Wherein the direction of vibration of a polarized light becomes the ω angle with the optical axis of said first right-angle prism; The direction of vibration of another polarized light becomes
angle with the optical axis of said first right-angle prism, x light and the y light exported through said wollaston prism are received by said first photodetector and second photodetector respectively.
The mixed light of the pairwise orthogonal linearly polarized light that said x light is said two-frequency laser outgoing, promptly o light and with the mixed light of e light, blending ratio is k, k=sin
2ω, said y light are the mixed light of o light and e light, and blending ratio is 1-k.
The span of said ω is: 0≤ω≤180.
It is the He-Ne two-frequency laser of 1152nm that said two-frequency laser adopts wavelength.
The present invention is owing to take above technical scheme; It has the following advantages: the present invention is because the laser that wollaston prism, first photodetector and second photodetector are exported with two-frequency laser as a whole is an axle rotation ω angle; Make the pairwise orthogonal linearly polarized light that impinges perpendicularly on first right-angle prism through two-frequency laser; Wherein the direction of vibration of a polarized light becomes the ω angle with the optical axis of first right-angle prism; The direction of vibration of another polarized light becomes
angle with the optical axis of first right-angle prism; Two-frequency laser is exported two linearly polarized lights and is transmitted into postrotational wollaston prism at this moment; X light and y light through wollaston prism output are received by first photodetector and second photodetector respectively; Therefore the present invention is under the prerequisite that does not increase any system cost and circuit complexity; Make that the voltage difference of adjacent high and low 2 isocandela points remains unchanged in the one-period, the overall magnitude of signal is significantly dwindled, thereby makes the voltage difference of adjacent high and low 2 isocandela points in signal integral body, occupy bigger ratio; Make adjacent high and low isocandela point significantly separately; Made things convenient for signal Processing, effectively avoided having improved the precision and the stability of laser displacement measurement system greatly owing to two measuring error that the isocandela point excessively closely causes miscount to cause at the overall signal middle distance.The present invention can be widely used in the signal processing of laser displacement measurement.
Description of drawings
Fig. 1 is a two-frequency laser output laser power power tuning curve hour; Wherein
is o light, and
is e light; The horizontal ordinate express time, the s of unit, ordinate are signal voltage, the V of unit, broken line are expressed as the process that piezoelectric ceramics (PZT) voltage rises and descends;
Fig. 2 is existing signal-count disposal route synoptic diagram, the horizontal ordinate express time, and the s of unit, ordinate are signal voltage, the V of unit;
Fig. 3 is the power tuning curve of two-frequency laser output laser power when big;
is o light, and
is e light; The horizontal ordinate express time, the s of unit, ordinate are signal voltage, the V of unit, broken line are expressed as the process that piezoelectric ceramics voltage rises and descends;
Fig. 4 is existing high-gain laser displacement transducer system architecture synoptic diagram;
Fig. 5 is the structural representation of wollaston prism in the embodiment of the invention;
expression first right-angle prism optical axis direction is parallel to paper, and " " expression second right-angle prism optical axis direction is perpendicular to paper;
Fig. 6 is the power tuning curve synoptic diagram that k gets 0 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless;
Fig. 7 is the power tuning curve synoptic diagram that k gets 0.1 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless;
Fig. 8 is the power tuning curve synoptic diagram that k gets 0.2 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless;
Fig. 9 is the power tuning curve synoptic diagram that k gets 0.3 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless;
Figure 10 is the power tuning curve synoptic diagram that k gets 0.4 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless;
Figure 11 is the power tuning curve synoptic diagram that k gets 0.45 o'clock x light and y light; " " is x light;
is y light, and horizontal ordinate is represented the long variation in chamber, the nm of unit; Ordinate is a light intensity, dimensionless.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is carried out detailed description.
As shown in Figure 4; It is basic identical that the disclosed 1152nm wavelength helium neon laser nano of laser displacement sensor that the present invention adopted and prior art is surveyed the laser displacement sensor structure that is adopted in the chi, and it comprises two-frequency laser, photoelectric switching circuit, single-chip microcomputer and driver circuit for piezoelectric ceramics; Two-frequency laser comprises laser gain pipe 1; One end of laser gain pipe 1 is provided with outgoing mirror 2; The other end is provided with anti-reflection window 3; Outgoing mirror 2 arranged outside have the polarization splitting prism vertical with the laser propagation direction 4, and the light direction of corresponding polarization splitting prism 4 is respectively arranged with first photodetector 5 and second photodetector 6; Anti-reflection window 3 outsides are disposed with birefringece crystal 7 and chamber mirror 8 along the laser propagation direction; The outside of chamber mirror 8 is set with piezoelectric ceramics (PZT) 9; Piezoelectric ceramics 9 is connected with the both positive and negative polarity of driver circuit for piezoelectric ceramics 10; Two-frequency laser output laser is transmitted into polarization splitting prism 4 through outgoing mirror 2; Polarization splitting prism 4 mutually perpendicular horizontal polarization light of output and orthogonal polarized light are received and are sent to two input ends of photoelectric switching circuit 11 respectively by first photodetector 5 and second photodetector 6; Photoelectric switching circuit 11 is handled the light signal that receives and is sent to single-chip microcomputer 12,9 work of single-chip microcomputer 12 control driver circuit for piezoelectric ceramics 10 drive pressure electroceramics.
As shown in Figure 5; Polarization splitting prism 4 adopts wollaston prism 4 among the present invention; Wollaston prism 4 is the rectangular prisms that are bonded along the inclined-plane by first right-angle prism 41 and second right-angle prism 42; The optical axis of first right-angle prism 41 and second right-angle prism 42 is orthogonal and all perpendicular to the face normal of the plane of incidence (MN face), first right-angle prism 41 and second right-angle prism 42 all adopt calcite crystal to be made.Incide first right-angle prism 41 of wollaston prism 4 through the pairwise orthogonal linearly polarized light of two-frequency laser outgoing; When the MN face of the direction of vibration of two linearly polarized lights and first right-angle prism 41 is parallel or vertical; The pairwise orthogonal linearly polarized light is separated by strictness; When the direction of vibration of two linearly polarized lights became other angle beta (β ≠ 0 or 90) with the optical axis of first right-angle prism, the pairwise orthogonal linearly polarized light was failed behind wollaston prism 4 separately, but is blended in the two-beam according to different proportion.
According to the principle of cross polarization laser, chamber mirror 8 whenever moves half wavelength, the laser intensity fluctuation one-period of outgoing mirror 2 outputs; The laser of chamber mirror 8 outputs is the mixed light of o light and e light; O light and e light inequality proportion are mixed the other two-beam of formation: x light and y light, comprise part o light and e light in the x light, also comprise part o light and e light in the y light; Suppose that blending ratio is that k (0≤k≤1) o light gets into x light, then ratio is the o light entering y light of (1-k); In like manner, ratio is that the e light of k gets into y light, and ratio is that the e light of (1-k) gets into x light, and then the light intensity of x light and y light is expressed as:
I
x/y＝k×I
o/e+(1-k)×I
e/o
According to above-mentioned principle; The present invention serves as an axle rotation ω angle (0≤ω≤180) with the laser of two-frequency laser output with wollaston prism 4, first photodetector 5 and second photodetector 6 as a whole; Make the pairwise orthogonal linearly polarized light that impinges perpendicularly on first right-angle prism 41 through two-frequency laser; Wherein the direction of vibration of a polarized light becomes the ω angle with the optical axis of first right-angle prism 41, and the direction of vibration of another polarized light becomes with the optical axis of first right-angle prism 41
Angle; Two-frequency laser is exported two linearly polarized lights and is transmitted into postrotational wollaston prism 4 at this moment, and x light and the y light exported through wollaston prism 4 are received by first photodetector 5 and second photodetector 6 respectively, and wherein x light is the mixed light of o light and e light; Blending ratio is k; Y light is the mixed light of o light and e light, and blending ratio is 1-k, k=sin
2ω, the size of angle ω can be confirmed according to the experiment needs, as long as with high and low two isocandela points adjacent in the one-period separately.
Shown in Fig. 6～11; Further specify practical implementation process of the present invention through specific embodiment below, it is the He-Ne two-frequency laser of 1152nm that two-frequency laser adopts wavelength, through rotation wollaston prism 4; Make first right-angle prism 41 and form a series of different angle ω through the two-frequency laser emitting laser; Make k=0,0.1,0.2,0.3,0.4 and 0.45, when the value of blending ratio k value increased gradually, the adjacent high and low isocandela point that can observe o light and e light obviously separated gradually; For example: the blending ratio k of o light and e light gets 0.45 in the x light; The anglec of rotation is that ω is about arcsin0.67082, and as can be seen from Figure 11 the absolute voltage difference of adjacent high and low isocandela point does not change, but the overall magnitude of signal is greatly reduced; O light significantly separates with the adjacent high and low isocandela point of e light, so just can adopt existing method easily signal to be carried out subsequent treatment.
In sum, further show, adopt polarization aliasing method of the present invention through experiment; Not only can significantly increase the relative distance of height isocandela point; Easily the interval width of each segmentation is regulated, and do not changed the lateral attitude of adjacent height isocandela point, measurement result is accurate.
Above-mentioned each embodiment only is used to explain the present invention, and wherein all implementation processes of method etc. all can change to some extent, and every equivalents of on the basis of technical scheme of the present invention, carrying out and improvement all should not got rid of outside protection scope of the present invention.
Claims (5)
1. the polarization aliasing method of a high gain lasers displacement transducer; It comprises two-frequency laser, photoelectric switching circuit, single-chip microcomputer, piezoelectric ceramics and driver circuit for piezoelectric ceramics; Said two-frequency laser comprises laser gain pipe, outgoing mirror and anti-reflection window; Said outgoing mirror arranged outside has the wollaston prism vertical with the laser propagation direction, and the light direction of corresponding said wollaston prism is respectively arranged with first photodetector and second photodetector; Said wollaston prism is to be bonded along the inclined-plane by first right-angle prism and second right-angle prism, and the optical axis of said first right-angle prism and said second right-angle prism is orthogonal and all perpendicular to the face normal of the plane of incidence; It is characterized in that: with said wollaston prism, first photodetector and second photodetector is an anglec of rotation ω with said two-frequency laser emitting laser as a whole; Make the pairwise orthogonal linearly polarized light that impinges perpendicularly on said first right-angle prism through said two-frequency laser; Wherein the direction of vibration of a polarized light becomes the ω angle with the optical axis of said first right-angle prism; The direction of vibration of another polarized light becomes
angle with the optical axis of said first right-angle prism, x light and the y light exported through said wollaston prism are received by said first photodetector and second photodetector respectively.
2. the polarization aliasing method of a kind of high gain lasers displacement transducer as claimed in claim 1; It is characterized in that: the mixed light of the pairwise orthogonal linearly polarized light that said x light is said two-frequency laser outgoing; Be o light and with the mixed light of e light, blending ratio is k, k=sin
2ω, said y light are the mixed light of o light and e light, and blending ratio is 1-k.
3. the polarization aliasing method of a kind of high gain lasers displacement transducer as claimed in claim 1, it is characterized in that: the span of said ω is: 0≤ω≤180.
4. the polarization aliasing method of a kind of high gain lasers displacement transducer as claimed in claim 2, it is characterized in that: the span of said ω is: 0≤ω≤180.
5. like the polarization aliasing method of claim 1 or 2 or 3 or 4 described a kind of high gain lasers displacement transducers, it is characterized in that: it is the He-Ne two-frequency laser of 1152nm that said two-frequency laser adopts wavelength.
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Citations (4)
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|---|---|---|---|---|
| US5896200A (en) * | 1997-07-29 | 1999-04-20 | The University Of Chicago | Optical design for laser encoder resolution extension and angular measurement |
| CN1233093A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Displacement self-sensing helium-neon laser system and its embodiment method |
| CN1645036A (en) * | 2005-01-21 | 2005-07-27 | 清华大学 | Self-mixed interference displacement sensor based on two-way laser |
| CN102506685A (en) * | 2011-10-26 | 2012-06-20 | 清华大学 | Displacement measurement method based on piezoelectric ceramic open-loop modulation |
-
2012
- 2012-09-04 CN CN201210323603.6A patent/CN102829729B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5896200A (en) * | 1997-07-29 | 1999-04-20 | The University Of Chicago | Optical design for laser encoder resolution extension and angular measurement |
| CN1233093A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Displacement self-sensing helium-neon laser system and its embodiment method |
| CN1645036A (en) * | 2005-01-21 | 2005-07-27 | 清华大学 | Self-mixed interference displacement sensor based on two-way laser |
| CN102506685A (en) * | 2011-10-26 | 2012-06-20 | 清华大学 | Displacement measurement method based on piezoelectric ceramic open-loop modulation |
Non-Patent Citations (2)
| Title |
|---|
| 赵慧洁: "外差干涉仪频率混叠误差分析", 《计量学报》 * |
| 赵慧洁: "激光束频率混叠误差分析", 《宇航计测技术》 * |
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