CN114415388A - Device for improving illumination uniformity - Google Patents
Device for improving illumination uniformity Download PDFInfo
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- CN114415388A CN114415388A CN202111675894.0A CN202111675894A CN114415388A CN 114415388 A CN114415388 A CN 114415388A CN 202111675894 A CN202111675894 A CN 202111675894A CN 114415388 A CN114415388 A CN 114415388A
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- 238000005286 illumination Methods 0.000 title claims abstract description 18
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- 238000007781 pre-processing Methods 0.000 claims description 4
- 230000003287 optical effect Effects 0.000 abstract description 15
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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 light beam processing unit and a speckle attenuating unit sequentially disposed on a transmission path of the light beam output from the light source; the light beam processing unit is used for adjusting the optical parameters of the light beams to preset values and emitting the light beams to the speckle attenuation unit; the speckle attenuation unit comprises a rotating disk and a plurality of reflection microstructures arranged on the surface of the rotating disk, the reflection microstructures are arranged on the rotating disk in an annular or spiral mode, each reflection microstructure comprises a reflection surface, the reflection surfaces of the reflection microstructures face the light beam processing unit, and the distances from the reflection surfaces of any two reflection microstructures to the reference surface of the rotating disk are different. The device has good effect of inhibiting speckle patterns 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 strong coherence. When the laser is used for irradiating the surface of an object, because the surface of the object has certain roughness, different light beams scattered to each direction of the space through the surface of the object interfere with each other due to the existence of a small optical path difference, so that interference fringes can be formed on the image surface, and granular irregularly distributed noise, namely speckle noise, is generated, which is not beneficial to obtaining uniform illumination. The existence of the speckles seriously affects the detail information of the image, and reduces the definition and the resolution of the image. Therefore, attenuation processing of image speckles due to laser coherence is required.
Speckle contrast is generally used as an evaluation criterion of speckle noise, and the larger the contrast value is, the more serious the speckle noise is. Superimposing N different speckle patterns within the CCD response time or the human eye integration time is an effective way to reduce speckle contrast. When N speckle patterns independent of each other are superposed, the contrast of speckle on image surface or received by human eyes can be reduced to original contrast
Therefore, the larger the number of independent speckle patterns that are superimposed during the CCD response time or the human eye integration time, the more desirable the speckle reduction effect and the better the illumination uniformity.
Conventional static speckle reduction devices that employ stepped reflective elements distributed row-by-row/column-by-column, or in a grid, are more suitable for large size spots. When the device is used for small-size light spots, the light spots cannot be widely dispersed due to small sizes, so that the speckle attenuation effect can be reduced, and if a large number of reflection microstructures are adopted, the possibility of improving the processing difficulty and cost of the device can be brought.
Disclosure of Invention
The application provides a technical problem that the above-mentioned background art part exists is solved to device that promotes illumination homogeneity.
A device for improving illumination uniformity, comprising a speckle attenuation unit, wherein the speckle attenuation unit comprises a plurality of reflective microstructures, the plurality of reflective microstructures are arranged on the surface of a rotating disk, each reflective microstructure comprises a reflective surface far away from the surface of the rotating disk, and the distances from the surface of the rotating disk to at least any two adjacent reflective microstructures are different.
In some embodiments, the laser light incident on the reflective microstructure is perpendicular to the reflective surface or perpendicular to the reflective surface at an angle not greater than a predetermined angle.
In some embodiments, any two of the reflective microstructures of the speckle attenuation cell are not 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 reflective surfaces of at least two adjacent reflective microstructures of the speckle attenuation cell are not parallel.
In some embodiments, the difference between the distances of the reflecting surfaces of any two of the reflecting microstructures from the reference surface of the rotating disk is greater than half of the coherence length of the light beam.
In some embodiments, the plurality of reflective microstructures is arranged in a ring or spiral on the rotating disk.
In some embodiments, the number of revolutions of the helical arrangement is related to the spot size, the rotational speed of the rotating disk, and the speckle contrast desired.
In some embodiments, the apparatus further comprises a beam processing unit for pre-processing the beam, the pre-processing 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 of different sizes. A large number of reflecting 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. Need not to match other optical element and come the plastic to the laser facula, the structure is easily processed, easy operation, stable performance, has fine suppression effect to the stripe pattern that the laser coherence leads to.
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FIG. 1 is a schematic diagram of an apparatus for enhancing illumination uniformity provided in one embodiment;
fig. 2 is a schematic diagram of an apparatus for improving illumination uniformity provided in another embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.
Please refer to fig. 1, which shows a schematic diagram of an apparatus for improving illumination uniformity to which the present application may be applied.
A device for improving 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 from at least any two adjacent reflection microstructures to the surface of the rotating disk are different.
The distances between the two reflecting microstructures and the surface of the rotating disk are different (namely, the thicknesses of the reflecting microstructures are different), so that when light beams are incident to the reflecting microstructures on the rotating disk, each reflecting microstructure generates one reflecting sub-light beam, the optical path difference exists between any two reflecting sub-light beams, and the interference between all the reflecting sub-light beams does not occur any more.
According to the method, a large number of independent patterns are superposed in the integration time of a CCD camera or human eyes by adopting the method of rotating the reflective reflection microstructures with different characteristics and annularly distributed, so that the purpose of attenuating image stripes caused by laser coherence is achieved, the illumination uniformity can be improved, and the definition of the patterns is improved. The method has applicability to different sizes of light spots. A large number of reflecting 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 reduction unit further comprises a motor connected to the rotating disc via a rotating wheel.
It will be appreciated that the reflective microstructures are stepped reflective surfaces of different heights. The number N of the reflecting microstructures 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 (light beam) is reflected at the surface of each reflective microstructure, and each reflective microstructure generates a reflected sub-beam. There is a certain difference in the height of all the reflective microstructures. So that the sub-beams after the incident laser beam is reflected by the surface of each reflecting microstructure have a certain optical path difference. All reflected sub-beams are collectively referred to as reflected beams. The incident light beam can be vertical to the surface of the reflecting microstructure and can also have a certain incidence angle with the surface of the reflecting microstructure. In order to ensure that the reflected sub-beams do not interfere with each other any more, the thickness difference between the stepped reflective microstructures should be greater than half of the coherence length of the incident laser, so as to ensure that the optical path difference between the sub-beams reflected by the surfaces of all the reflective microstructures is greater than the coherence length of the laser, so that the reflected sub-beams do not interfere with each other, and the generation of speckles is greatly attenuated. The light reflected from each reflective microstructure can produce a different speckle pattern relative to the other reflective microstructures. In the integration time of the CCD or human eyes, the more the number of the accumulated independent speckle patterns is, the more the speckle contrast can be reduced, the speckle can be attenuated, and the imaging quality can be improved. The number N of the reflecting microstructures and the rotating speed of the rotating wheel can both influence the number of the superposed stripes within a certain integration time, and the larger the numerical value of N is, the better the effect of attenuation on the stripes is. The rotating speed of the rotating wheel is matched with the CCD or human eye integral time, the unit integral time corresponds to one rotation of the rotating wheel, and the rotating wheel starts new circulation at the next integral time. The unit integration time may correspond to 1/2 revolutions or 1/3 revolutions, among other values.
In some application scenarios, as shown in fig. 2, a plurality of step-shaped microstructures (step-shaped microstructures are not shown in the figure) are distributed in the surface gray region, and the microstructure form is the same as that in 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 same size of the rotating wheel, a larger number of microstructures can be distributed to generate a larger number of independent speckle patterns, and a better speckle attenuation effect can be obtained. The number of helical rotations of the surface of the wheel is variable depending on the particular application, depending on the spot size, the rotational speed of the wheel, and the speckle contrast desired. The spiral is realized in such a way that the light beam position needs to be linearly moved 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 period of wheel rotation is equal to the period of beam movement. When the wheel rotates, the light spot scans from the microstructure area at the outermost side to the area at the innermost side, and simultaneously, the light spot linearly translates from the outermost side of the wheel to the innermost side of the wheel (the moving distance is about d). When the wheel starts the next cycle, the spot moves back to the outermost side of the wheel.
In some embodiments, when a light beam enters the reflecting surface of the reflecting microstructure, the light beam is perpendicular to the reflecting surface or the included angle between the light beam and the reflecting surface is not greater than a preset included 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 in some embodiments, the reflective faces 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 a partial microstructure having an angular difference. The non-parallel microstructured surfaces may serve a dual speckle attenuation function, where on the one hand steps with different thicknesses introduce a certain optical path difference for each reflected sub-beam. In the second aspect, because of the slight angle difference of the step surfaces, the transmission directions of the respective reflected sub-beams do not completely coincide, and the angular spread of the reflected light beam is enlarged, thereby introducing spatial and angular diversity between the reflected sub-beams, and further reducing the probability of interference. The possibility of interference between the sub-beams can be further reduced by the common superposition of the optical path difference and the spatial and angular diversity, so that a better speckle attenuation effect is obtained.
Of course, in some implementations, each stepped microstructure surface is parallel, where all sub-beams reflected by the microstructure surface travel in the same direction. The different step thicknesses between the microstructures can introduce optical path difference between the reflected sub-beams to reduce the interference effect between the sub-beams, thereby playing the role of speckle attenuation.
In some embodiments, the reflective surfaces of all reflective microstructures arranged on a 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 light spot of the light beam.
In some embodiments, the difference in the distances of the reflective surfaces of any two reflective microstructures from the reference surface of the rotating disk is greater than half the coherence length of the light beam.
All microstructures have the same surface area, the surface size is equal to the light spot size, and the whole light spot size can be contained. The microstructures have the same surface shape, and the surface shape can be rectangular, square, multi-square or irregular. In the aspect of surface structure selection, only the side length of the light beam passing through in the moving process needs 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 ring-like manner that decreases one by one, or increases one by one.
The height of the microstructures is optimally chosen such that all microstructures have different thicknesses and that the height difference between all microstructures is guaranteed to be larger than half the optical path difference, so that the best speckle attenuation is obtained.
In some embodiments, the beam processing unit adjusts one or a combination of the spectral bandwidth, the time-dependence, and the polarization state of the light beam.
The laser wavelength, polarization, illumination angle, coherence, and roughness of the illuminated object surface all contribute to speckle characteristics.
From the perspective of a laser light source, the laser spectral bandwidth can be increased to achieve speckle attenuation, and the speckle can be improved by changing the time correlation of laser light, or the speckle attenuation can be achieved by changing the polarization state of the laser light.
In addition to the static attenuation method, the method proposed by the present application achieves the same effect as the conventional speckle attenuation method using a dynamic optical element. However, in the conventional method, when a small spot size is faced, in order to obtain a good speckle attenuation effect, the spot may need to be shaped in advance by beam expansion, collimation, or the like, so that a corresponding optical element needs to be introduced, and the cost and the volume of the system are increased. In addition, conventional methods such as vibrating optical fibers have problems of difficulty in optical path alignment, high energy loss rate, and the like.
In some embodiments, the plurality of reflective microstructures are arranged in a spiral pattern on the rotating disk, and the number of revolutions of the spiral pattern is related to the spot size, the rotating speed of the rotating disk, and the desired speckle contrast.
It will be understood by those skilled in the art that all or part of the processes of the apparatus implementing the embodiments described above can be implemented by the relevant hardware instructed by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the apparatus described above. The storage medium may be a non-volatile storage medium such as a magnetic disk, an optical disk, a Read-Only Memory (ROM), or a Random Access Memory (RAM).
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. An apparatus for improving illumination uniformity, comprising a speckle attenuation unit, wherein the speckle attenuation unit comprises a plurality of reflective microstructures, the plurality of reflective microstructures are arranged on a surface of a rotating disk, each reflective microstructure comprises a reflective surface far away from the surface of the rotating disk, and the distances from at least any two adjacent reflective microstructures to the surface of the rotating disk are different.
2. The device for improving illumination uniformity of claim 1, wherein the angle between the laser beam incident on the reflective microstructure and the vertical plane of the reflective surface or the vertical plane of the reflective microstructure is not greater than a preset angle.
3. The apparatus of claim 1, wherein any two of the reflective microstructures of the speckle attenuation cell are not the same distance from the surface of the rotating disk.
4. The apparatus of claim 1, wherein the reflecting surfaces of all the reflecting microstructures have the same shape and size.
5. The apparatus of claim 1, wherein the reflective surfaces of at least two adjacent reflective microstructures of the speckle attenuation unit are not parallel.
6. The apparatus of claim 1, wherein the difference between the distances of the reflecting surfaces of any two of the reflecting microstructures from the reference surface of the rotating disk is greater than half of the coherence length of the light beam.
7. The apparatus of claim 1, wherein the plurality of reflective microstructures are arranged in a ring or spiral on the rotating disk.
8. The apparatus of claim 7, wherein the number of revolutions of the helical arrangement is related to the spot size, the rotational speed of the rotating disk, and the speckle contrast desired.
9. The apparatus according to claim 1, further comprising a beam processing unit for preprocessing the beam, wherein the preprocessing comprises adjusting one or a combination of a beam size, a time dependence and a beam polarization state of the beam.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111675894.0A CN114415388B (en) | 2021-12-31 | 2021-12-31 | Device for improving illumination uniformity |
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| CN202111675894.0A CN114415388B (en) | 2021-12-31 | 2021-12-31 | Device for improving illumination uniformity |
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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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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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