CN100386930C - HeNe laser device capable of outputting two beams of vertically polarized light with stabilized intensity - Google Patents
HeNe laser device capable of outputting two beams of vertically polarized light with stabilized intensity Download PDFInfo
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- CN100386930C CN100386930C CNB2005100113833A CN200510011383A CN100386930C CN 100386930 C CN100386930 C CN 100386930C CN B2005100113833 A CNB2005100113833 A CN B2005100113833A CN 200510011383 A CN200510011383 A CN 200510011383A CN 100386930 C CN100386930 C CN 100386930C
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Abstract
The present invention relates to He-Ne laser which can output two beams of vertical polarized light with stable light intensity, and the present invention belongs to the technical field of lasers. The present invention is characterized in that the present invention comprises a laser gain pipe, a main light beam output mirror, a transverse magnetic field generator and a small frequency difference generator, wherein both sides of the laser gain pipe are respectively provided with a high reflectance tail light output mirror and an anti-reflection window sheet; the main light beam output mirror is positioned at one side of the anti-reflection window sheet. The small frequency difference generator can be a birefringent crystal arranged between the anti-reflection window sheet and the main light beam output mirror, or a mechanical stress applied device for applying mechanical stress in a direction which is perpendicular to the axial direction of the laser gain pipe for the anti-reflection window sheet. The laser is fixed on a support stand, and the cavity length of the laser is designed to satisfy requirements for a single longitudinal mould or a double longitudinal mould output of the laser all along in the process of cavity coordination. The small frequency difference generator makes the longitudinal mould in a laser resonator split into two vertical polarization frequencies of small frequency differences. The present invention has the advantages of small light intensity variation, good stability and strong anti-interference ability.
Description
Technical field
The invention belongs to the laser design field
Background technology
Self-mixed interference displacement measuring technology (be also referred to as light and return routed measuring technology) is to utilize the laser light intensity to export light because of it to return a special kind of skill that phenomenon that resonant cavity changes is measured again.This kind displacement measuring device light path system has only a laser and an extraneous reverberation.The light of laser output be reflected or scattering after the return laser light resonant cavity, mix the variable power that causes laser with light in the chamber, external mirror whenever moves striped of displacement lasers device variable power of half optical wavelength, and the fluctuation degree of depth of striped and traditional double beam interference system can compare.The laser power striped can be directly used in counting and realize displacement measurement, and systemic resolution is a half wavelength.
What the self-mixed interference system utilized in measurement is that laser self light intensity changes and the realization counting, therefore the self-mixed interference system is higher to the stability requirement of the light intensity of laser, if laser causes himself light intensity shakiness because of ambient temperature variation, vibrations etc., make that the light intensity drift is bigger, the drift of light intensity will cause miscount so, thereby influences the accuracy of measurement result.
The self-mixed interference system generally uses the laser of single longitudinal mode, for example in the HeNe laser, make that laser is a single longitudinal mode laser, and it is long shorter generally will to design laser chamber, guarantees that at least laser bright dipping bandwidth is less than two longitudinal mode spacings.But consider the light intensity output that laser is bigger, generally will make laser works near centre frequency on the gain curve, laser is a single mode not only like this, and light intensity is bigger.
In actual applications, the laser light intensity is drifted about because of ambient temperature variation, vibrations etc., and this light intensity drift will cause miscount.The drift of laser light intensity can be simulated by the humorous process of intonation.The fluctuation degree of depth that at first defines laser is
I
MaxAnd I
MinBe respectively the maximum and the minimum value of laser output intensity.For the long HeNe laser of short cavity, its light intensity tuning curve as shown in Figure 1.Laser is not always the single mode state in the humorous process of intonation, laser is two longitudinal mode states in the fractionated gain curve ranges, and adjacent two longitudinal mode polarization directions are orthogonal.Fig. 1 hollow core circle point curve is directional light light intensity curve figure, and the real point curve is the vertical light light intensity curve.In the chamber two orthogonal polarized lights separately light intensity in the humorous process of intonation, change all greatlyyer, the two light beats degree of depth all are about 0.8.In the self-mixed interference system, returning the maximum fluctuation degree of depth of routed signal own is 1, and for the long HeNe laser of short cavity, the signal fluctuation degree of depth is relatively to be fit to practical application between the 0.4-0.7 in the actual measurement.If it is excessive to return the routed signal fluctuation degree of depth, then require the body surface reflectivity to want high; If instead the fluctuation degree of depth is big or small excessively, then weak output signal and be unfavorable for signal processing.
The self-mixed interference displacement measuring technology is generally used the fringe count method.To use hysteresis comparator in the fringe count circuit to improve the antijamming capability of circuit, also can eliminate the caused miscount of light intensity minor variations simultaneously.The hysteresis comparator up and down setting of cut-ff voltage difference should guarantee to surpass back the fluctuation range of routed signal itself, if above could count.Simultaneously the cut-ff voltage difference can not be less than the scope of laser self light intensity drift up and down for hysteresis comparator, otherwise can cause miscount.If the drift of laser light intensity is excessive in the practical application, cut-ff voltage is poor up and down to have surpassed hysteresis comparator, will cause miscount.Therefore for the long HeNe laser of common short cavity, because its light intensity is drifted about greatlyyer because of the variation of environment, need take modes such as constant temperature or vibration isolation to guarantee that laser chamber is long stable, could effectively reduce miscount.Do to make the system complex heaviness like this, cost also can increase greatly simultaneously.
Summary of the invention
The object of the invention is to provide the HeNe laser of two stable orthogonal polarized lights of a kind of energy output intensity, and this laser light intensity can be used for the self-mixed interference system not because of significant changes such as variations in temperature or vibrations, effectively reduces miscount.
The present invention is characterised in that, it is the HeNe laser of two stable orthogonal polarized lights of energy output intensity, and it comprises:
Laser gain pipe, inside are filled with the HeNe mist;
Tail light outgoing mirror is 99.8% to the reflectivity of incident laser;
Anti-reflection window, this anti-reflection window and tail light outgoing mirror are individually fixed in the laser gain pipe two ends;
Little frequency difference generator, this little frequency difference generator makes the interior longitudinal mode of resonant cavity become the frequency of two little frequency difference vertical polarizations, this little frequency difference generator is a mechanical type stress bringing device, along axially being installed on the above-mentioned anti-reflection window, this anti-reflection window is applied a stress perpendicular to laser gain pipe;
Main beam outgoing mirror, reflectivity are 98%, and this main beam outgoing mirror and laser gain pipe lay respectively at little frequency difference generator both sides;
The transverse magnetic field generator, this transverse magnetic field generator applies parallel or perpendicular to the transverse magnetic field of the stress direction of little frequency difference generator to laser gain pipe;
The long L of this laser chamber satisfies:
3c/2Λ＞L＞c/Λ
Wherein Λ is a laser bright dipping bandwidth, and c is the light velocity, will guarantee that promptly laser is in the humorous process of intonation or be operated in the single mode state or be operated in the bimodulus state.
The invention provides a kind of HeNe laser of can output intensity stable two orthogonal polarized lights, not Yin Wendu or vibrations etc. and the significant change of this laser light intensity, being used for the self-mixed interference system can effectively reduce miscount, sees Fig. 2.
Description of drawings
The light intensity tuning curve of different polarization light in the long HeNe laser of Fig. 1 short cavity;
The HeNe laser schematic diagram and the testing apparatus thereof of two orthogonal polarized lights that Fig. 2 the application's energy output intensity is stable;
The example 2 of the HeNe laser of two orthogonal polarized lights that Fig. 3 the application's energy output intensity is stable;
The light intensity tuning curve figure of two orthogonal polarized lights in Fig. 4 the application laser;
The application's laser two orthogonal polarized lights under no magnetic field condition return routed curve chart in the humorous process of Fig. 5 (a) intonation; (b) interior two orthogonal polarized lights of the application's laser return routed curve chart in the humorous process of intonation;
Embodiment
Experimental provision of the present invention as shown in Figure 2,1 is the tail light outgoing mirror of HeNe laser, its reflectivity is generally 99.8%, 2 is the gain tube of laser, and inside is filled with the mist of HeNe, and 3 is the anti-reflection window of laser, 4 is the main beam outgoing mirror of laser, and reflectivity is generally 98%.1,2,3 and 4 have formed the main body of a common HeNe laser jointly.In order to guarantee that laser can be operated in the single mode state or be operated in the bimodulus state, we design the long 155mm of being of laser chamber, and this chamber covers with the restriction of sufficient formula 2.In order to guarantee that certain polarization luminous energy obtains stable light intensity output in the chamber, apply a stress by 5 pairs of existing laser windows 3 of mechanical type stress bringing device and produce birefringence effect.The frequency that this birefringence effect can make two vertical polarizations of a longitudinal mode output, these two difference on the frequencies are 6.7MHz.This mechanical type stress bringing device is a reinforcing ring that studs with a screw, and the degree of tightness of adjustment screw can be regulated the size of stress.Because mode competition, two frequencies can only be exported one, so place transverse magnetic field generator 6 in the laser gain pipe both sides, it is made of jointly two blocks of permanent magnets.The transverse magnetic field direction that the transverse magnetic field generator produces is parallel or perpendicular to the direction of above-mentioned stress, the adding in magnetic field can reduce the mode competition of two frequencies in the two-frequency laser greatly to realize the output of little frequency difference.Six parts of 1-6 have constituted the application's laser, and this laser can be exported two linear orthogonal polarized lights.
7 is the exocoel speculum, and in actual applications, this speculum is an object under test.Piezoelectric ceramic 8 drives speculum 7 moving along radiation direction.7 and 8 two elements have been formed the exocoel of self-mixed interference system, and the chamber is long to be 310mm.7 and 8 two elements are used for the routed characteristic of returning of this laser is tested.
The tail light of laser is divided into two orthogonal polarized lights through Wollaston prism 9, and the polarised light of the two bundle quadratures that obtain this moment is surveyed by detector 10 and 11 respectively, and gained two photosignals are handled by computer 12.Computer 12 realizes collecting the function of signals collecting and measurement result demonstration by the mode of software programming.Element 9-12 is used for corollary system that the application's laser is tested.Whole experiment device can be divided into three parts: 13 are the application's laser, and 14 for measure portion is the exocoel of self-mixed interference system, and 15 is signal processing.
The principle of the invention is as follows.Burst and do not add under the condition in magnetic field at unglazed time, its light intensity tuning curve is as shown in Figure 1 in the humorous process of intonation for the long HeNe laser of the designed short cavity of the application.Two orthogonal polarized light light intensity all fluctuate greatlyyer in the chamber, and two polarised light light stabilities are bad, as are used for the self-mixed interference measuring system and cause miscount easily.When to laser when the window stress direction applies a transverse magnetic field, the laser gain curve becomes two, one is π gain of light curve, one is σ gain of light curve.Variation tendency was identical when two curves were in two longitudinal mode state at laser.The adding in magnetic field simultaneously also makes a longitudinal mode in the laser become the frequency (π light and σ light) of two vertical polarizations.At this moment, laser is as being operated in two longitudinal mode states, and each pattern all comprises π light and σ light.This disappears and other rises in the humorous process of intonation for the π light of adjacent two longitudinal modes or σ light, compensation mutually, so certain polarised light laser works during at two longitudinal mode light intensity do not have significant change.And when laser works during at the single longitudinal mode state, because the gain curve middle part is milder, the light of two kinds of polarization states does not have obvious light intensity yet to be changed.When laser works during at two longitudinal mode in two moulds with the light intensity summation of the frequency of polarization state and laser works during at single longitudinal mode the light intensity with the frequency of polarization direction approaching, so in the humorous process of whole intonation, the laser light intensity does not have significant change generally.The two orthogonal polarized light light intensity tuning curves that the application's laser is exported as shown in Figure 4.Two light are in the humorous process of intonation, and the light-intensity variation degree of depth is 0.14, and in Fig. 1 is 0.8 the fluctuation degree of depth, and the application's laser optical stiff stability will be got well a lot.
Fig. 5 has provided time routed curve of the laser of the application in the intonation association process.It is humorous slowly laser to be carried out intonation when return to burst existing, and cycle much smaller than cycle of inner chamber mirror drive signal of the drive signal of exocoel speculum is set in the experiment.In the experiment to laser carry out the humorous purpose of intonation be initiatively make the drift of laser light intensity, simulate the drift that laser light intensity in the practical application causes because of variations in temperature or vibration.Fig. 5 (a) is time routed curve chart of the application's laser two orthogonal polarized lights in not having the condition cavity of resorption in magnetic field.Return routed curve chart in order better to observe two polarised lights, directional light returns the curve of the bursting 4500mV that made progress translation among Fig. 5, separately is convenient to analyze so that two polarised lights return the curve chart of bursting.Among each figure of Fig. 5, be that directional light returns routed curve chart by last curve, intermediate curve is an exocoel mirror drive signal for return the nethermost curve of curve chart of bursting for vertical light.Returning routed curve among Fig. 5 (a) is that the light intensity tuning curve is modulated by time routed signal on the whole, returns routed signal modulation amplitude and is directly proportional with the polarised light light intensity magnitude.Than returning routed signal amplitude, the drift of laser light intensity is excessive, can't prevent miscount.And two polarised lights all have one section unglazed zone, and this feasible measurement can't be carried out.Therefore this type laser is measured as being used for, and then requires chamber stability fine, and wants the latch well internal schema to be operated near the centre frequency, to obtain the bigger time routed signal of amplitude.This just has higher requirement to the manufacturing of measurement environment and laser, has not only dwindled range of application but also has increased cost.
Fig. 5 (b) is time routed performance diagram of the application's laser two orthogonal polarized lights in the humorous process lumen of intonation.Returning routed curve is still the light intensity tuning curve on the whole and is returned routed signal and modulate, but than returning routed signal amplitude, laser light intensity drift frames degree is significantly less than back routed signal fluctuation amplitude, and return routed signal in the humorous process of intonation, fluctuate amplitude in Fig. 5 (a) in the significant change of different gains curve location.Therefore we can be provided with easily in the fringe count circuit hysteresis comparator up and down the cut-ff voltage difference so just can effectively avoid miscount greater than laser light intensity drift maximum and less than returning routed signal fluctuation amplitude.Simultaneously in the humorous process of intonation, the state that can't carry out because of laser no-output light can not appear measuring in the state that certain polarised light of the application's laser does not extinguish.
The structural representation of example 2 of the present invention as shown in Figure 3.Element 1-4 and element 6 are identical with element 1-4 and element 6 among Fig. 2.What the little frequency difference generator that different with example 1 is in the example 1 used is stress bringing device 5, is birefringece crystal 16 and the little frequency difference generator in the example 2 uses.
The HeNe laser of two can the output intensity stable orthogonal polarized lights that the present invention is designed, the long design in chamber satisfy laser and remain laser single longitudinal mode or the output of two longitudinal mode in the processes of intonation association.Utilize the frequency splitting technology to make frequency that longitudinal mode splitting is two vertical polarizations of little frequency difference in the laserresonator, laser works is when two longitudinal mode, this disappears and other rises and compensation mutually for identical polarization state frequency light intensity in two longitudinal modes, makes two identical polarization state frequency light intensity summations stable and near with laser single longitudinal mode time strong cohesiveness.So the light-intensity variation in the humorous process of intonation of the application's laser is little, has light stability preferably, disturbs insensitive to external world.The HeNe laser of two can the output intensity stable orthogonal polarized lights that the present invention is designed has light intensity not Yin Wendu or vibrations etc. and the characteristics of significant change are suitable for the self-mixed interference system, can effectively reduce miscount.
Claims (1)
1. the HeNe laser of two can output intensity stable orthogonal polarized lights is characterized in that it comprises:
Laser gain pipe, inside are filled with the HeNe mist;
Tail light outgoing mirror is 99.8% to the reflectivity of incident laser;
Anti-reflection window, this anti-reflection window and tail light outgoing mirror are individually fixed in the laser gain pipe two ends;
Little frequency difference generator, this little frequency difference generator makes the interior longitudinal mode of resonant cavity become two frequencies with little frequency difference vertical polarization, this little frequency difference generator is a mechanical type stress bringing device, along axially being installed on the above-mentioned anti-reflection window, this anti-reflection window is applied a stress perpendicular to laser gain pipe;
Main beam outgoing mirror, reflectivity are 98%, and this main beam outgoing mirror and laser gain pipe lay respectively at little frequency difference generator both sides;
The transverse magnetic field generator, this transverse magnetic field generator applies parallel or perpendicular to the transverse magnetic field of the stress direction of little frequency difference generator to laser gain pipe;
The long L of this laser chamber satisfies:
3c/2Λ＞L＞c/Λ
Wherein Λ is a laser bright dipping bandwidth, and c is the light velocity, will guarantee that promptly laser is operated in the single mode state or is operated in the bimodulus state in the humorous process of intonation.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100113833A CN100386930C (en) | 2005-03-04 | 2005-03-04 | HeNe laser device capable of outputting two beams of vertically polarized light with stabilized intensity |
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2005100113833A CN100386930C (en) | 2005-03-04 | 2005-03-04 | HeNe laser device capable of outputting two beams of vertically polarized light with stabilized intensity |
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| CN1671011A CN1671011A (en) | 2005-09-21 |
| CN100386930C true CN100386930C (en) | 2008-05-07 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106500601A (en) * | 2016-10-13 | 2017-03-15 | 南通大学 | Helium neon laser nano surveys ruler system |
| CN106500602A (en) * | 2016-10-13 | 2017-03-15 | 南通大学 | Helium neon laser nano surveys ruler system |
| CN110940941B (en) * | 2018-04-12 | 2022-03-25 | 安徽大学 | Magnetic field sensing measurement device and method based on multi-longitudinal-mode self-mixing effect |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1089763A (en) * | 1993-09-14 | 1994-07-20 | 中国科学院上海光学精密机械研究所 | Laser system with double frequence |
| CN1207598A (en) * | 1998-09-08 | 1999-02-10 | 清华大学 | Tunable middle frequency difference He-Ne double frequency laser |
| CN1233092A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Birefrigent double-frequency laser without frequency tolerance blocking and its frequency tolerance accuracy control method |
| CN1233093A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Displacement self-sensing helium-neon laser system and its embodiment method |
| CN2506002Y (en) * | 2001-10-31 | 2002-08-14 | 清华大学 | Two-dimension force applying mode zecman double reflection bifrequency laser |
| CN1379225A (en) * | 2002-05-31 | 2002-11-13 | 清华大学 | Frequency-dividing self-mixing feedback-type non-contact He-Ne laser micrometer |
-
2005
- 2005-03-04 CN CNB2005100113833A patent/CN100386930C/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1089763A (en) * | 1993-09-14 | 1994-07-20 | 中国科学院上海光学精密机械研究所 | Laser system with double frequence |
| CN1207598A (en) * | 1998-09-08 | 1999-02-10 | 清华大学 | Tunable middle frequency difference He-Ne double frequency laser |
| CN1233092A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Birefrigent double-frequency laser without frequency tolerance blocking and its frequency tolerance accuracy control method |
| CN1233093A (en) * | 1999-04-02 | 1999-10-27 | 清华大学 | Displacement self-sensing helium-neon laser system and its embodiment method |
| CN2506002Y (en) * | 2001-10-31 | 2002-08-14 | 清华大学 | Two-dimension force applying mode zecman double reflection bifrequency laser |
| CN1379225A (en) * | 2002-05-31 | 2002-11-13 | 清华大学 | Frequency-dividing self-mixing feedback-type non-contact He-Ne laser micrometer |
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