CN114415388B - Device for improving illumination uniformity - Google Patents
Device for improving illumination uniformity Download PDFInfo
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- CN114415388B CN114415388B CN202111675894.0A CN202111675894A CN114415388B CN 114415388 B CN114415388 B CN 114415388B CN 202111675894 A CN202111675894 A CN 202111675894A CN 114415388 B CN114415388 B CN 114415388B
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- 238000005286 illumination Methods 0.000 title claims abstract description 18
- 238000012545 processing Methods 0.000 claims abstract description 7
- 230000009467 reduction Effects 0.000 claims abstract description 5
- 230000010287 polarization Effects 0.000 claims description 5
- 238000007781 pre-processing Methods 0.000 claims description 4
- 230000003287 optical effect Effects 0.000 abstract description 15
- 230000000694 effects Effects 0.000 abstract description 12
- 230000005540 biological transmission Effects 0.000 abstract description 2
- 230000005764 inhibitory process Effects 0.000 abstract 1
- 230000010354 integration Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 238000007796 conventional method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/48—Laser speckle optics
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Abstract
The invention relates to a device for improving illumination uniformity, which comprises: device for improving illumination uniformity, characterized in that the device comprises: a beam processing unit and a speckle reduction unit disposed in the transmission path of the light beam outputted from the light source in this order; the light beam processing unit is used for adjusting the optical parameters of the light beam to a preset value and transmitting the preset value to the speckle attenuation unit; the speckle attenuation unit comprises a rotary disk, a plurality of reflection microstructures are arranged on the surface of the rotary disk, the reflection microstructures are annularly or spirally arranged on the rotary disk, each reflection microstructure comprises a reflection surface, the reflection surfaces of the reflection microstructures face the light beam processing unit, and the distances between the reflection surfaces of any two reflection microstructures and the reference surface of the rotary disk are different. The device has good inhibition effect on the speckle pattern caused by laser coherence.
Description
Technical Field
The invention relates to the technical field of optical equipment, in particular to a device for improving illumination uniformity.
Background
The laser radiation has a very strong coherence. When the surface of the object is irradiated by laser, because the surface of the object has certain roughness, different light beams scattered in all directions of space through the surface of the object interfere with each other due to the existence of tiny optical path difference, interference fringes can be formed on an image surface, noise which is irregularly distributed in particles, namely speckle noise, is generated, and uniform illumination is not facilitated. The presence of speckle seriously affects the detailed information of the image, reducing the definition and resolution of the image. Therefore, it is necessary to attenuate the image speckle due to the laser coherence.
The speckle contrast is generally used as an evaluation criterion for speckle noise, and the larger the contrast value is, the more serious the speckle noise is. The addition of N pairs of different speckle patterns during the CCD response time or during the human eye integration time is an effective way to reduce speckle contrast. When N mutually independent speckle patterns are overlapped, the speckle contrast received by the image plane or human eyes can be reduced to the original speckle contrastTherefore, the more the number of superimposed independent speckle patterns is within the CCD response time or the human eye integration time, the more ideal the speckle attenuation effect is, and the better the illumination uniformity is.
The conventional static speckle attenuation device adopting stepped reflecting elements distributed row by row/column by column or grid is more applicable to large-size light spots. When the device is used for small-size light spots, the light spots cannot be widely dispersed due to small size of the light spots, so that the speckle attenuation effect can be reduced, and the device processing difficulty and the cost can be increased if a large number of reflection microstructures are adopted.
Disclosure of Invention
The application provides a device for improving illumination uniformity, which solves the technical problems existing in the background art.
The device for improving illumination uniformity comprises a speckle attenuation unit, wherein the speckle attenuation unit comprises a plurality of reflection microstructures, the reflection microstructures are arranged on the surface of a rotating disc, each reflection microstructure comprises a reflection surface far away from the surface of the rotating disc, and the distances between at least any two adjacent reflection microstructures and the surface of the rotating disc are different.
In some embodiments, the laser light incident on the reflective microstructure is perpendicular to the reflective surface or at an angle to a perpendicular to the reflective surface that is not greater than a predetermined angle.
In some embodiments, any two of the reflective microstructures of the speckle reduction unit are not at the same distance from the surface of the rotating disk.
In some embodiments, the reflective surfaces of all of the reflective microstructures are the same shape and size.
In some embodiments, the speckle reduction units are not parallel to the reflective surfaces of at least two adjacent reflective microstructures.
In some embodiments, the difference in distance of the reflective surface of any two of the reflective microstructures from the reference surface of the rotating disk is greater than half the coherence length of the light beam.
In some embodiments, the plurality of reflective microstructures are arranged in an annular or spiral pattern on the rotating disk.
In some embodiments, the number of revolutions of the helical arrangement is related to spot size, rotational speed of the rotating disc, and desired speckle contrast.
In some embodiments, the apparatus further comprises a beam processing unit for preprocessing the beam, the preprocessing comprising adjusting one or a combination of beam, time dependence and beam polarization state of the beam.
The device for improving the illumination uniformity has applicability to light spots with different sizes. A large number of reflection microstructures with different characteristics can be arranged in a limited space, so that a larger number of independent speckle patterns are generated, and the speckle attenuation capability is improved. The laser beam spot is shaped without matching with other optical elements, the structure is easy to process, the operation is simple, the performance is stable, and the suppression effect on the speckle pattern caused by the laser coherence is good.
Drawings
FIG. 1 is a schematic diagram of an apparatus for improving illumination uniformity provided in one embodiment;
fig. 2 is a schematic view of an apparatus for improving illumination uniformity according to another embodiment.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It will be understood that the terms "first," "second," and the like, as used herein, may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element.
Referring to fig. 1, a schematic diagram of an apparatus for improving illumination uniformity to which the present application may be applied is shown.
The device for improving the illumination uniformity can comprise a speckle attenuation unit, wherein the speckle attenuation unit comprises a plurality of reflection microstructures, the reflection microstructures are arranged on the surface of a rotating disk, each reflection microstructure comprises a reflection surface far away from the surface of the rotating disk, and the distances between at least any two adjacent reflection microstructures and the surface of the rotating disk are different.
The distances between the two reflective microstructures and the surface of the rotating disk are different (i.e. the thicknesses of the reflective microstructures are different), so that when the light beams are emitted into the reflective microstructures on the rotating disk, each reflective microstructure generates one reflective sub-beam, the optical path difference exists between any two reflective sub-beams, and interference does not occur between all the reflective sub-beams.
According to the method, a large number of independent patterns are overlapped in the CCD camera or human eye integration time by adopting the reflective microstructure with the rotary annular distribution and different characteristics, so that the purpose of attenuating image speckles caused by laser coherence is achieved, the illumination uniformity can be improved, and the definition of a graph is improved. The method is applicable to light spots with different sizes. A large number of reflection microstructures with different characteristics can be arranged in a limited space, so that a larger number of independent speckle patterns are generated, and the speckle attenuation capability is improved.
Further, the speckle attenuation unit further comprises a motor, and the motor is connected with the rotating disc through a rotating wheel.
It is understood that reflective microstructures are stepped reflective surfaces of different heights. The number of reflective microstructures N is a natural number. All the reflecting microstructures are annularly distributed on a rotating wheel, the center of the rotating wheel is connected with a motor, and the rotating wheel is driven to rotate by the motor.
In some applications, as shown in fig. 1, an incident laser beam (beam) is reflected at each reflective microstructure surface, and each reflective microstructure produces a reflected sub-beam. All reflective microstructures have a certain difference in height. So that the incident laser beams have a certain optical path difference between the sub-beams after being reflected by each reflective microstructure surface. All reflected sub-beams are collectively referred to as reflected beams. The incident light beam may be perpendicular to the reflective microstructured surface or may have an angle of incidence with the reflective microstructured surface. In order to ensure that the reflected sub-beams do not interfere any more, the thickness difference between the stepped reflecting microstructures is larger than half of the coherence length of the incident laser, so that the optical path difference between the sub-beams reflected by the surfaces of all the reflecting microstructures is larger than the coherence length of the laser, and therefore the reflected sub-beams do not interfere with each other, and the generation of speckles is greatly attenuated. The light reflected by each reflective microstructure can produce a different speckle pattern relative to the other reflective microstructures. The more the number of the independent speckle patterns is accumulated in the integration time of the CCD or human eyes, the more the speckle contrast is reduced, the attenuation effect is achieved on the speckle, and the imaging quality is improved. The number N of the reflecting microstructures and the rotating speed of the rotating wheel can influence the number of the speckles overlapped with a certain integral time, and the larger the number N is, the better the attenuation effect of the speckles is. The rotating speed of the rotating wheel is matched with the CCD or the human eye integration time, the unit integration time corresponds to one rotation of the rotating wheel, and the rotating wheel starts a new cycle at the next integration time. The unit integration time can also correspond to other values such as 1/2 of a revolution of the wheel, or 1/3 of a revolution.
In some application scenarios, as shown in fig. 2, a surface gray area is distributed with a plurality of stepped microstructures (the stepped microstructures are not shown in the figure), and the microstructure is the same as the distribution in fig. 1. The center of the rotating wheel is connected with a motor through a rotating shaft, and the motor drives the rotating wheel to rotate (not shown in the figure). Unlike fig. 1, the microstructures in fig. 2 are spirally distributed on the rotating wheel, so that for the rotating wheel with the same size, more microstructures can be distributed, and further, more independent speckle patterns are generated, so that a better speckle attenuation effect is obtained. The number of helical revolutions of the wheel surface is variable depending on the particular application and is related to spot size, wheel speed, and desired speckle contrast value. The spiral implementation mode is that the beam position needs to linearly move simultaneously along with the uniform rotation of the rotating wheel, and the moving range of the light spot is about the distance d in the figure. The wheel rotation period is equivalent to the period of beam movement. As the wheel rotates, the spot is linearly translated from the outermost side of the wheel to the innermost side of the wheel (a distance of movement of about d) while the spot scans from the outermost microstructure area to the innermost area. When the wheel starts the next cycle, the spot moves again to the outermost side of the wheel.
In some embodiments, when a light beam is incident on the reflective surface of the reflective microstructure, the angle between the light beam and the reflective surface or the light beam is perpendicular to the reflective surface is not greater than a preset angle.
In some embodiments, the reflective surfaces of at least two reflective microstructures on the rotating disk are not parallel.
It will be appreciated that some of the stepped microstructure surfaces are parallel and that in some embodiments the reflective surfaces of any two reflective microstructures on the rotating disk are not parallel.
It will be appreciated that each stepped microstructure surface may also be non-parallel, such as with a slight angular difference between all microstructures, or with an angular difference between some microstructures. The non-parallel micro-structure surface can play a role in dual speckle attenuation, and on one hand, steps with different thicknesses can introduce certain optical path difference to each reflected sub-beam. In the second aspect, since there is a slight angle difference in the stepped surfaces, the transmission directions of the respective reflected sub-beams do not coincide completely, and the angular spread of the reflected beams is enlarged, thereby introducing spatial and angular diversity between the reflected sub-beams, and further reducing the probability of interference. Through the joint superposition of the optical path difference, the space and the angle diversity, the possibility of interference between sub-beams can be further reduced, and a better speckle attenuation effect is obtained.
Of course, in some implementations, each stepped microstructured surface is parallel, where all sub-beams reflected off the microstructured surface are transmitted in the same direction. The different step thicknesses among the microstructures can introduce optical path difference among the reflected sub-beams to reduce interference effect among the sub-beams, thereby playing a role of speckle attenuation.
In some embodiments, the reflective surfaces of all reflective microstructures arranged on the rotating disk are the same shape and size. The size of the reflecting surface of the reflecting microstructure is not smaller than the size of the spot of the light beam.
In some embodiments, the difference in distance of the reflective surface of any two reflective microstructures from the reference surface of the rotating disk is greater than half the coherence length of the light beam.
The surface area of all microstructures is the same, the surface size is equal to the spot size, and the whole spot size can be contained. The microstructures have the same surface shape, which may be rectangular, square, multiparty, or irregular. In the selection of the surface structure, only the side length of the light beam passing through in the moving process needs to be ensured to be larger than the side length or the diameter of the light spot.
The height of each microstructure (i.e., the thickness of each step) is different. The heights of all microstructures may be randomly distributed, or may be arranged in a circular manner that decreases one by one, or increases one by one.
The optimal choice of the height of the microstructures is that all microstructures have different thicknesses and that the height difference between all microstructures is larger than half the optical path difference, so that the best speckle attenuation effect can be obtained.
In some embodiments, the beam processing unit adjusts one or a combination of spectral bandwidth of the beam, time dependence, and polarization state of the beam.
The laser wavelength, polarization, illumination angle, coherence, and roughness of the illuminated object surface all have an effect on speckle characteristics.
From the angle of a laser light source, the bandwidth of a laser spectrum can be increased to realize the attenuation of the speckle, and the aim of improving the speckle is further achieved through changing the time correlation of the laser, or the attenuation of the speckle is realized through changing the polarization state of the laser and the like.
In addition to the static attenuation method, the method provided by the application can obtain the same effect as the conventional speckle attenuation method adopting a dynamic optical element. However, in the conventional method, when the spot size is relatively small, in order to obtain a relatively good speckle attenuation effect, shaping treatments such as beam expansion, collimation and the like may need to be performed on the spot in advance, and therefore, corresponding optical elements need to be introduced, which increases the cost and volume of the system. In addition, conventional methods such as vibrating optical fibers have problems such as difficult alignment of optical paths and high energy loss rate.
In some embodiments, the plurality of reflective microstructures are arranged in a spiral on the rotating disk, the number of rotations of the spiral being related to the spot size, the rotating disk speed, and the desired speckle contrast.
Those skilled in the art will appreciate that implementing all or part of the above-described embodiments of the apparatus may be accomplished by way of a computer program stored in a computer readable storage medium, which when executed may comprise the steps of embodiments of the apparatus as described above. The storage medium may be a nonvolatile storage medium such as a magnetic disk, an optical disk, a Read-Only Memory (ROM), or a random access Memory (Randoma Access Memory, RAM).
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (7)
1. A device for improving illumination uniformity, comprising a speckle attenuation unit, wherein the speckle attenuation unit comprises a plurality of reflection microstructures, the reflection microstructures are arranged on the surface of a rotating disk, each reflection microstructure comprises a reflection surface far from the surface of the rotating disk, and the distances between at least two reflection microstructures and the surface of the rotating disk are different;
the difference of the distances between the reflecting surfaces of any two reflecting microstructures and the reference surface of the rotating disk is more than half of the coherence length of the light beam;
the plurality of reflection microstructures are annularly arranged or spirally arranged on the rotating disc.
2. The apparatus of claim 1, wherein the angle between the laser light incident on the reflective microstructure and the perpendicular to the reflective surface is no greater than a predetermined angle.
3. The apparatus for improving illumination uniformity according to claim 1, wherein any two of said reflective microstructures of said speckle reduction unit are at different distances from the surface of said rotating disk.
4. The apparatus of claim 1, wherein the reflective surfaces of all of the reflective microstructures are the same shape and size.
5. The apparatus of claim 1, wherein the speckle reduction element is non-parallel to the reflective surfaces of at least two adjacent reflective microstructures.
6. The apparatus of claim 1, wherein the number of rotations of the spiral arrangement is related to spot size, rotation speed of the rotating disk, and desired speckle contrast.
7. The apparatus of claim 1, further comprising a beam processing unit for preprocessing the beam, the preprocessing comprising adjusting one or a combination of beam size, time dependence, and beam polarization state of the beam.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111675894.0A CN114415388B (en) | 2021-12-31 | 2021-12-31 | Device for improving illumination uniformity |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111675894.0A CN114415388B (en) | 2021-12-31 | 2021-12-31 | Device for improving illumination uniformity |
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| CN114415388A CN114415388A (en) | 2022-04-29 |
| CN114415388B true CN114415388B (en) | 2024-01-19 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010169828A (en) * | 2009-01-21 | 2010-08-05 | Victor Co Of Japan Ltd | Illumination device and projection image display apparatus using the same |
| CN102016763A (en) * | 2008-08-29 | 2011-04-13 | 康宁股份有限公司 | Systems and methods for speckle reduction |
| CN102906630A (en) * | 2010-05-21 | 2013-01-30 | 康宁股份有限公司 | Systems and methods for reducing speckle using diffusing surfaces |
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- 2021-12-31 CN CN202111675894.0A patent/CN114415388B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102016763A (en) * | 2008-08-29 | 2011-04-13 | 康宁股份有限公司 | Systems and methods for speckle reduction |
| JP2010169828A (en) * | 2009-01-21 | 2010-08-05 | Victor Co Of Japan Ltd | Illumination device and projection image display apparatus using the same |
| CN102906630A (en) * | 2010-05-21 | 2013-01-30 | 康宁股份有限公司 | Systems and methods for reducing speckle using diffusing surfaces |
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| CN114415388A (en) | 2022-04-29 |
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