CN102468598A - Laser - Google Patents
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- CN102468598A CN102468598A CN2010105346652A CN201010534665A CN102468598A CN 102468598 A CN102468598 A CN 102468598A CN 2010105346652 A CN2010105346652 A CN 2010105346652A CN 201010534665 A CN201010534665 A CN 201010534665A CN 102468598 A CN102468598 A CN 102468598A
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Abstract
The invention provides a laser, which comprises a dispersion element which is positioned in a resonant cavity of the laser, wherein when the laser light which is produced by the laser passes by the dispersion element, the phase of the laser light is randomly modulated by the dispersion element, so the laser light is converted into partially coherent light to be output. The invention has the beneficial effects that: the coherence of the laser is reduced through inserting the dispersion element into the resonant cavity of the laser, accordingly, the speckle problem of the laser display technology is basically solved, and the quality of the laser displayed image is improved.
Description
Technical field
The present invention relates to laser field, be specifically related to a kind of laser.
Background technology
Laser is as a kind of new type light source; Have that monochromaticjty is good, good directionality, the coherence is good and brightness is high characteristics; Therefore laser display with tradition demonstration compare have bigger colour gamut, higher contrast and brightness, color is more bright-coloured, more can reflect natural realistic colour.But, when arriving the rough object surface, relevant fully laser radiation forms diffuse reflection easily, make to superpose at spatial coherence from the light of rough object surface reflection, interfere in whole space, thus the either overt or covert spot (being speckle) of formation random distribution.These speckles have had a strong impact on image quality, have reduced the contrast and the resolution of image.
In order to overcome above-mentioned defective, those skilled in the art have proposed several different methods, like a plurality of LASER Light Sources by different wave length incident light are provided; Utilize single fiber or fiber bundle (multiple beams of optical fiber) transmission; Utilize the stack of pulse laser, move scattering object, move aperture diaphragm; The vibration screen; Outside the chamber, utilize binary optical elements etc. to be transformed into flat top beam or super-Gaussian beam to Gaussian beam, it is relevant to utilize liquid crystal or frosted glass etc. to have a parts implementation part of scattering function again, or utilizes parts such as the variable reflectivity mirror that is installed in the chamber, gradual change phase place mirror, built-in flexible mirror to obtain method such as the uniform super-Gaussian beam of center intensity to reach the purpose that weakens speckle.These methods say it all is to form the back at laser it is carried out various processing to reach the purpose of eliminating speckle from principle, though can play a role, eliminate the DeGrain of speckle, and not from solving the speckle issue the laser display in essence.
Summary of the invention
For from solving the speckle issue the laser display in essence, the invention provides a kind of laser that can produce partially coherent light.
To achieve these goals, the invention provides a kind of laser, it comprises dispersing element, and said dispersing element is positioned at the resonant cavity of said laser; Wherein,
The laser that said laser produces is during via said dispersing element, and its phase place is by said dispersing element Stochastic Modulation, exports after making said laser change partially coherent light into.
In the technique scheme, said resonant cavity comprises laser crystal, frequency-doubling crystal and outgoing mirror; Said dispersing element is between said frequency-doubling crystal and the said outgoing mirror or between said laser crystal and said frequency-doubling crystal.
In the technique scheme, said resonant cavity comprises laser crystal and outgoing mirror; Said dispersing element is between said laser crystal and said outgoing mirror.
In the technique scheme, said resonant cavity comprises laser crystal and frequency-doubling crystal; Said dispersing element is between said laser crystal and said frequency-doubling crystal.
In the technique scheme, said dispersing element is liquid crystal cell or liquid crystal display screen.
In the technique scheme, said liquid crystal cell normality is scattering, and its scattering power raises with applied voltage and weakens.
In the technique scheme, said liquid crystal display screen adds the external voltage that is useful on the liquid crystal molecule generation polarization that makes in the said liquid crystal display screen.
In the technique scheme, said dispersing element is a random phase plate, and said random phase plate rotates in the course of the work.
In the technique scheme, said random phase plate rotates under the drive of motor.
In the technique scheme, said outgoing mirror is plano-concave mirror or level crossing.
The invention has the beneficial effects as follows: through in the resonant cavity of laser, inserting the coherence that dispersing element reduces laser, thereby solved the speckle issue in the laser display technology in itself, improved the picture quality of laser display.
Description of drawings
Fig. 1 is the formation schematic diagram of speckle in the laser display;
Fig. 2 is in one embodiment, inserts the structural representation of the laser of liquid crystal cell in the resonant cavity;
Fig. 3 is in one embodiment, inserts the structural representation of the laser of random phase plate in the resonant cavity.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is elaborated.
Before the present invention was elaborated, at first the formation principle to speckle in the laser display described.Fig. 1 is the formation schematic diagram of speckle in the laser display.According to coherent condition, direction of vibration is identical, vibration frequency is identical, phase place is identical or the constant light of phase difference maintenance is coherent light, and the light that is therefore produced by same light source generally speaking is coherent light, and the light that the projecting apparatus 102 among Fig. 1 is sent is coherent light.Light beam 103 and light beam 104 are the close two-beams in the light beam that sends of projecting apparatus 102, and this two-beam projects emission can take place to overflow on the rough surface 101, and then at an A constructive interference or a destructive interference takes place.If the generation constructive interference, the A point is a bright spot; If the generation destructive interference, then the A point is a dim spot.Similarly, the coherent light that projecting apparatus 102 sends has a lot of close beamlets all can be radiated at rough surface and just to have formed either overt or covert speckle as light beam 103 and light beam 104 the same generations length or destructive interference mutually.
Therefore, avoid the speckle phenomena in the laser display, the solution that the inventor proposed is not have full coherence between the light that makes light source (like laser) emit.In Fig. 2, provided the structure chart of a kind of implementation of the laser that can produce partially coherent light.
Fig. 2 inserts the structural representation of the laser of liquid crystal cell in one embodiment in the resonant cavity.Liquid crystal is a kind of comparatively ideal scattering object, and scattering liquid crystal is based on the scattering of molecular array, and the scattering particulate is little, have scattering evenly, the light energy transmitance is big, be easy to advantage such as control.Liquid crystal molecule is that arrangement is orderly, and its dielectric constant has anisotropy, and under the effect of extra electric field, liquid crystal molecule polarizes, and after extra electric field arrives to a certain degree greatly, produces irregular deformation, and liquid crystal molecule is along circular motion.Produce motion and orientation fluctuation because extra electric field brings out liquid crystal molecule, light wave in the resonant cavity has been caused dynamic scattering, destroyed the coherence of incident beam.Through the change applied voltage, the size of may command liquid crystal molecule coherence area size, thus reach the purpose of controlling incident laser.Because scattering liquid crystal need be by extra electric field, the liquid crystal cell that the liquid crystal molecule of therefore selecting for use scattering power to change noticeably with applied voltage is in the present embodiment formed.
Laser shown in Figure 2 comprises LD pumping source 201, condenser lens 202, laser crystal 203, frequency-doubling crystal 204, liquid crystal cell 205 and outgoing mirror 206.Laser crystal 203, frequency-doubling crystal 204, liquid crystal cell 205 and outgoing mirror 206 constitute resonant cavity.Wherein, liquid crystal cell 205 normalities are scattering states, and scattering power weakens with the applied voltage rising and scattering power changes noticeably with applied voltage.Liquid crystal molecule size in the liquid crystal cell 205 is at 0.5-2.0 μ m, the thick 2.2cm of liquid crystal cell, and liquid crystal bed thickness 10 μ m, light transmission rate is 70%.The operating voltage range of liquid crystal cell 205 is 0-50V, and working temperature is 0-50 ℃.When said laser is installed, liquid crystal cell 205 is inserted in the resonant cavity, can be positioned between frequency-doubling crystal 204 and the outgoing mirror 206.In other embodiments, liquid crystal cell 205 also can be positioned between laser crystal 203 and the frequency-doubling crystal 204.Become fundamental frequency light after the light line focus lens 202 that LD pumping source 201 sends get into laser crystal 203, fundamental frequency light becomes frequency doubled light through frequency-doubling crystal 204 again.According to aforesaid liquid crystal molecule scattering principle; Under the effect of extra electric field, the liquid crystal molecule in the liquid crystal cell 205 can cause scattering to the fundamental frequency light that laser crystal 203 is sent, and destroys the coherence of fundamental frequency light; Make the resonant cavity inner light beam become partially coherent light, after outgoing mirror 206 outputs.This laser has just disturbed light before laser output coherence is from solved the speckle issue owing to coherence's generation laser display is used of laser in essence.Though in the present embodiment, adopt liquid crystal cell to realize that to the fundamental frequency scattering of light, those skilled in the art also can adopt the liquid crystal cell of other types, as be added with the liquid crystal display screen etc. of external voltage.
Fig. 3 is among another embodiment, in resonant cavity, inserts the laser structure sketch map of random phase plate.Random phase plate is actual to be a transparent medium plate; Examine under a microscope its structure; Can find to be thick with the different unit of many irregular, concavo-convex degree on it, different local density are distinguished to some extent, when laser passes random phase plate; By additional optical path difference at random, thereby removed spatial coherence.Based on this principle, in the embodiment shown in fig. 3, laser comprises LD pumping source 201, condenser lens 202, laser crystal 203, frequency-doubling crystal 204, random phase plate 305, outgoing mirror 206 and motor 307.On the output light path of LD pumping source 201, place condenser lens 202 successively, laser crystal 203, frequency-doubling crystal 204, random phase plate 305, motor 307 and outgoing mirror 206.Wherein, the one side of laser crystal 203 is coated with pump light anti-reflection film and the output laser film that is all-trans, and as the incident parts of resonant cavity, outgoing mirror 206 is as the outgoing parts of resonant cavity.Outgoing mirror 206 can be plano-concave mirror or level crossing.Random phase plate 305 is embedded in 307 li in motor, is integrated with it, drives random phase plate 305 by motor 307 and is rotated, and causes being radiated at the random phase of the laser on the random phase plate 305.After the pump light line focus lens 202 that LD pumping source 201 sends focus on, become fundamental frequency light through laser crystal 203, fundamental frequency light becomes frequency doubled light through frequency-doubling crystal 204 again.Fundamental frequency light gets into random phase plate 305, during through random phase plate 305, by everywhere concavo-convex degree is different on it; The fundamental frequency light that causes inciding has everywhere produced different optical path; Caused the phase place of output light chaotic, promptly obtained partially coherent light, at last by outgoing mirror 206 outputs.The laser of this laser output has partial ocoherence, and the speckle issue in the laser display is had the improvement on the essential meaning.
Though among two embodiment, adopted dispersing element in the above, also can adopt other dispersing elements that make light carry out scattering in other embodiments of the invention, as include the suspension of nano particle such as liquid crystal cell, random phase plate.In addition, in the above-described embodiments, all between frequency-doubling crystal and outgoing mirror, but in other embodiments, the position of dispersing element is not limited to this such as the dispersing element of liquid crystal cell, random phase plate.As long as dispersing element places in the laser resonant cavity, as between laser crystal and frequency-doubling crystal.At last; In the above-described embodiments, except including dispersing element, also all include laser crystal, frequency-doubling crystal and outgoing mirror in the said laser resonant cavity such as liquid crystal cell, random phase plate; But in other embodiments; Except said dispersing element, said laser resonant cavity can only comprise laser crystal, frequency-doubling crystal, and said dispersing element is between said laser crystal and said frequency-doubling crystal; Or only comprising laser crystal and outgoing mirror, said dispersing element is between said laser crystal and said outgoing mirror.
It should be noted last that above embodiment is only unrestricted in order to technical scheme of the present invention to be described.Although the present invention is specified with reference to embodiment; Those of ordinary skill in the art is to be understood that; Technical scheme of the present invention is made amendment or is equal to replacement, do not break away from the spirit and the scope of technical scheme of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (10)
1. a laser is characterized in that it comprises dispersing element, and said dispersing element is positioned at the resonant cavity of said laser; Wherein,
The laser that said laser produces is during via said dispersing element, and its phase place is by said dispersing element Stochastic Modulation, exports after making said laser change partially coherent light into.
2. laser according to claim 1 is characterized in that said resonant cavity comprises laser crystal, frequency-doubling crystal and outgoing mirror; Said dispersing element is between said frequency-doubling crystal and the said outgoing mirror or between said laser crystal and said frequency-doubling crystal.
3. laser according to claim 1 is characterized in that said resonant cavity comprises laser crystal and outgoing mirror; Said dispersing element is between said laser crystal and said outgoing mirror.
4. laser according to claim 1 is characterized in that said resonant cavity comprises laser crystal and frequency-doubling crystal; Said dispersing element is between said laser crystal and said frequency-doubling crystal.
5. according to claim 1 or 2 or 3 or 4 described lasers, it is characterized in that said dispersing element is liquid crystal cell or liquid crystal display screen.
6. laser according to claim 5 is characterized in that, said liquid crystal cell normality is scattering, and its scattering power raises with applied voltage and weakens.
7. laser according to claim 5 is characterized in that, said liquid crystal display screen adds the external voltage that is useful on the liquid crystal molecule generation polarization that makes in the said liquid crystal display screen.
8. according to claim 1 or 2 or 3 or 4 described lasers, it is characterized in that said dispersing element is a random phase plate, said random phase plate rotates in the course of the work.
9. laser according to claim 8 is characterized in that said random phase plate rotates under the drive of motor.
10. according to claim 2 or 3 described lasers, it is characterized in that said outgoing mirror is plano-concave mirror or level crossing.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2010105346652A CN102468598A (en) | 2010-11-03 | 2010-11-03 | Laser |
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| CN2010105346652A CN102468598A (en) | 2010-11-03 | 2010-11-03 | Laser |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103048791A (en) * | 2013-01-18 | 2013-04-17 | 苏州大学 | Method for producing partially coherent Airy beams |
| CN108767632A (en) * | 2018-06-14 | 2018-11-06 | 清华大学 | For generating the non-steady partially coherent photosystem of space-time |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008056318A2 (en) * | 2006-11-07 | 2008-05-15 | Koninklijke Philips Electronics N.V. | Method and device for speckle reduction |
| CN201845994U (en) * | 2010-11-03 | 2011-05-25 | 北京中视中科光电技术有限公司 | Laser device |
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2010
- 2010-11-03 CN CN2010105346652A patent/CN102468598A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008056318A2 (en) * | 2006-11-07 | 2008-05-15 | Koninklijke Philips Electronics N.V. | Method and device for speckle reduction |
| CN201845994U (en) * | 2010-11-03 | 2011-05-25 | 北京中视中科光电技术有限公司 | Laser device |
Non-Patent Citations (1)
| Title |
|---|
| QIANG LIN, ..ETC: "optical resonators producing partially coherent flat-top beams", 《OPTICS COMMUNICATIONS》, vol. 175, 1 March 2000 (2000-03-01), XP004202906, DOI: doi:10.1016/S0030-4018(00)00471-5 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103048791A (en) * | 2013-01-18 | 2013-04-17 | 苏州大学 | Method for producing partially coherent Airy beams |
| CN108767632A (en) * | 2018-06-14 | 2018-11-06 | 清华大学 | For generating the non-steady partially coherent photosystem of space-time |
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Application publication date: 20120523 |