WO2012100642A1

WO2012100642A1 - Speckle removal device based on mie scattering and motion of magnetically controlled particles

Info

Publication number: WO2012100642A1
Application number: PCT/CN2012/000041
Authority: WO
Inventors: 陈旭远; 高文宏; 石云波; 张文栋
Original assignee: 中北大学
Priority date: 2011-01-29
Filing date: 2012-01-10
Publication date: 2012-08-02
Also published as: CN102062953A; CN102062953B

Abstract

A speckle removal device relating to the technical field of display having a coherent light as a light source, based on Mie scattering and motion of magnetically controlled particles, solves the problems in the prior art of bad speckle removal effect, complex structure, high cost, and being easily damaged. The speckle removal device (300) comprises a closed optical reflective chamber (302) disposed with an incident optical coupler device (301) and a projection emergent surface (303). The inner walls of the closed optical reflective chamber (302) are all mirrors except the inner wall of the projection emergent surface (303). The inside of the closed optical reflective chamber (302) is filled with a solution or a sol (401). Dispersed inside of the solution or sol (401) are magnetic medium particles (402) having a linear dimension that triggers Mie scattering on an incident laser. Disposed for the closed optical reflective chamber (302) is a magnetic field generation device for generating a magnetic field. The electromagnet (308) of the magnetic field generation device is disposed outside of the closed optical reflective chamber. The speckle removal device has a logical, compact structure, high speckle removal effect, and is safe, reliable, and easy to implement at a low cost. The device has high laser utilization rate and stability, and makes illumination even.

Description

Speckle elimination device based on Mie scattering and magnetron particle motion

The invention relates to the field of display technology using coherent light as a light source, in particular to a speckle elimination device based on Mie scattering and magnetron particle motion, which mainly relates to optical speckle phenomenon existing in laser display technology and optical instrument.

Background technique

When the laser is used as the light source to illuminate the screen, the coherence of the laser and the roughness of the screen cause the human eye to see the image covered by the speckle, which seriously affects the image display quality and hinders the observer from extracting useful information from the image. Therefore, how to eliminate speckle has always been a research and development hotspot in the field of optical instruments and display technology with laser as the light source. As far as the current research results are concerned, the methods used to eliminate speckle can be roughly divided into two categories: 1. Control the temporal coherence of the laser source to reduce speckle. The principle is to adjust the laser wavelength (or frequency). And the multi-wavelength light source generates boiling speckle. At present, the technical solution for successfully eliminating the spot by controlling the laser time coherence to achieve practical requirements is basically based on multi-light source superposition; 2. Eliminating speckle by controlling the spatial coherence of the laser beam is currently eliminated. The main method of speckle, the basic principle is to adjust the phase distribution of the elementary light wave in the laser beam, thereby changing the spatial distribution of the speckle, and superimposing the plurality of speckle images in the integration time of the human eye to obtain a uniform distribution of light energy. The image, in turn, achieves the purpose of eliminating speckle. The specific methods are: using a rotating scatterer, a vibrating screen, and vibration

Hadamard graphic scatterers, high frequency vibrating fibers, etc. The above method, or mechanical vibration, even requires high frequency or large vibration, or integrated multiple light sources, to achieve a complex structure, easy to damage, high cost, and more importantly, the speckle removal effect is not good.

There are also technical solutions that do not rely on mechanical vibration, for example: China with patent number 200820122639.7 The patent discloses "a scattering-based dephasing shimming device" that requires the use of a scattering medium having particles having a diameter that must be less than one tenth of the wavelength of the incident light to effect Rayleigh scattering of the incident laser. In the patent, an inorganic salt or an aqueous solution of an organic alcohol (such as NaCl, KC1, KN0 ₃ or ZnS0 ₄ aqueous solution) is used as a scattering medium. The inorganic salt or organic alcohol aqueous solution is present in the form of hydrated ions or macromolecules, which is much smaller than the laser wavelength. Rayleigh scattering is formed on the incident laser to split the incident laser and conduct it in the light pipe, in order to reduce the coherence of the incident laser to eliminate the speckle, and at the same time, use the light mixing effect of the light pipe to split the beam Homogenize to homogenize the coherence. However, according to the technical method described in the application, the speckle was removed by a light pipe filled with a saturated NaCl aqueous solution at a temperature of 50 mm at room temperature. As a result, as shown in Fig. 1, the speckle contrast was 70%, which hardly played. Reduce the effect of speckle.

Summary of the invention

The present invention provides a speckle reduction device based on Mie scattering and magnetron particle motion in order to solve the problems of poor speckle removal, complex structure, easy damage, and high cost in the existing speckle elimination method.

The invention is realized by the following technical solutions: a speckle elimination device based on Mie scattering and magnetron particle motion, comprising a closed optical reflection cavity provided with an incident light coupling device and a transmission exit surface, and a closed optical reflection cavity The inner wall except the inner wall of the transmission exit surface is a "mirror" inner wall (ie, the inner wall has a high reflectivity characteristic, and can "fully reflect" the laser beam incident on the optical reflection cavity), and the closed optical reflection cavity is filled with the entire a solution or sol of the closed optical reflection cavity, and the solution or sol is dispersed with magnetic medium particles whose linearity can cause Mie scattering of the incident laser; the closed optical reflection cavity is provided with a magnetic field generating device for generating a magnetic field, and The electromagnet of the magnetic field generator is disposed outside the enclosed optical reflection cavity.

When applied, as shown in Figure 4, the laser beam emitted by the laser source is incident through the incident light coupling device. Mist scattering occurs in a solution or sol in a closed optical reflection chamber, and a magnetic medium particle dispersed in a solution or a sol (as shown in FIG. 3, when the incident laser 101 irradiates the magnetic medium particle 402 to Mie scattering) The intensity of the scattered light scattered by the incident laser 101 is distributed over a wide range of angles, mainly concentrated on the forward scattered light 104, 105, 106, which generally accounts for more than 90% of the total scattering; the backscattered light 102 only occupies a small The portion is usually less than 10%; the scattered light 105 along the direction of the incident laser light is the strongest, and the scattered light 103, 107 in the vertical direction is the weakest. Therefore, the incident laser light is scattered by the magnetic medium particles 402, and is split into a plurality of strengths. The scattered light, etc., while the scattering angle of the scattered light is enlarged, is split into a plurality of scattered light of different intensities, or reflected by the inner wall of the closed optical reflecting cavity, or again with the medium particles dispersed in the solution or sol. Mie scattering, the scattered light beam is more scattered light, after multiple Mie scattering, is emitted from the transmission exit surface of the closed optical reflection cavity; Under the system, the electromagnet is excited to form a constant magnetic field, or a pulsed magnetic field, or an alternating magnetic field outside the closed optical reflection cavity. The magnetic medium particles in the solution or sol are subjected to a magnetic field force to counteract the effect of gravity, and are made in solution or sol. Irregular thermal motion, or controlled motion under the action of a magnetic field, the incident laser will randomly move with the magnetic medium particles moving in the solution or sol to cause Mie scattering, so that the scattered light of the incident laser at each moment will randomly change in the solution or The direction and path of propagation in the sol, and finally the phase distribution and scattering angle distribution of the scattered light emitted from the exit surface of the optical reflection cavity are randomly changed. The scattered light at different times has different phase distribution and scattering angle distribution. After projection, a speckle image is generated correspondingly; in the eye integration time (50ms), multiple speckle images are superimposed, and An image with uniform light energy distribution achieves the purpose of eliminating speckle. '

Compared with the prior art, the present invention provides a closed optical reflection cavity filled with a solution or a sol, and the magnetic medium particles dispersed in the solution or the sol in the closed optical reflection cavity cause Mich scattering of the incident laser to perform scattering and splitting. And applying a magnetic field outside the closed optical reflection chamber to control the magnetic medium particles Irregular motion in a solution or sol, or counteracting gravity by magnetic force, causing irregular thermal motion of magnetic media particles, thereby randomly changing the propagation direction and path of the scattered beam in the closed optical reflection cavity, resulting in closed optical reflection The cavity exit surface distributes the scattered light of the incident laser with different phase distributions and scattering angles at different times; thereby changing the spatial distribution of the speckle after the projection, so that the plurality of speckle images are superimposed in the integration time of the human eye to obtain a The light energy is evenly distributed, which effectively eliminates speckle. And after testing, after applying the device of the invention, the speckle contrast of the image can be less than 4%, as shown in FIG. 5, the speckle contrast of the image is as low as 3.8%, and the speckle elimination effect is excellent; The speckle elimination effect is improved by increasing the temperature of the solution or sol, the concentration of the magnetic medium particles in the solution or the sol, controlling the variation of the field strength of the applied magnetic field, etc.; the present invention performs the incident laser in the closed optical reflection cavity. Total reflection", the total light energy loss of the incident laser is very small, which ensures the high utilization of the laser, and achieves the purpose of uniformity in the "total reflection"process; in addition, the closed optical reflection cavity structure used in the present invention is very common. Moreover, the solution and the sol do not need to select a special material, and have the advantage of low cost.

The invention has the advantages of reasonable structure, compactness, easy realization, low cost, good speckle elimination effect, high laser utilization rate, stable performance, safety and reliability, and uniform light function.

DRAWINGS

1 is a graph showing test results obtained by eliminating speckle using a prior art;

2 is a schematic structural view of the present invention;

Figure 3 is a diagram showing the angular distribution of light intensity of Mie scattering;

4 is a schematic view showing a transmission state of a light beam in the device of the present invention;

Figure 5 is a graph showing test results obtained by using the apparatus of the present invention to eliminate speckle;

6 is a schematic diagram of application of the device of the present invention in a point scan display system;

7 is a schematic diagram of application of the device of the present invention in a full frame display system; In the figure: 101 - incident laser; 102, 103, 104, 105, 106, 107 - scattered light;

300-speckle elimination device; 301-incident optical coupling device; 302-closed optical reflection cavity; 303- transmission exit surface; 304-incident optical aperture; 305, 306, 307-speckle elimination device; 308-electromagnet ( Not for the intentional table);

401-solution or sol; 402-magnetic medium particles;

501, 502, 503-laser;

601 602 > 603-signal source;

700-lens; 701-relay lens; 702-light modulator DLP; 703-TIR prism; 704-relay lens; 705-TIR prism; 706-light modulator DLP; 707-relay lens; 708-plane mirror; 709-TIR prism; 710-light modulator DLP; 711-prism; 712-micro-scanning mirror;

800-screen.

detailed description

As shown in FIG. 2, the speckle elimination device based on Mie scattering and magnetron particle motion includes a closed optical reflection cavity 302 on which an incident light coupling device 301 and a transmission surface 303 are disposed, and closed optical reflection. The inner wall of the cavity 302 except the inner wall of the transmission exit surface 303 is a "mirror surface" inner wall (ie, the inner wall has a high reflectivity characteristic, and can "fully reflect" the laser beam incident on the optical reflection cavity), and the closed optical reflection 脍 302 Filled with a solution or sol 401 filled with the entire closed optical reflection cavity 302, and the solution or sol 401 is dispersed with magnetic medium particles 402 whose linearity can cause Mie scattering of the incident laser light; the closed optical reflection cavity 302 is provided with A magnetic field generating device that generates a magnetic field, and an electromagnet 308 of the magnetic field generator is disposed outside the closed optical reflecting chamber 302.

In a specific implementation, the solution is an organic solution or an inorganic solution; the sol is an aerosol or a sol; the magnetic medium particles 402 may be polystyrene magnetic microspheres, silica magnetic microspheres, The ferroferric oxide magnetic microspheres, the ferric oxide magnetic microspheres, and the like; the closed optical reflection cavity 302 is mostly made of metal, plane mirror, transparent plastic or glass, and the shape thereof is not particularly limited, and generally adopts a tubular shape. The surface of the transmission exit surface 303 of the closed optical reflection cavity 302 is mostly made of transparent plastic or glass, and is mostly a rectangular plane or a circular plane, and the surface is provided with an antireflection film matched with the incident laser band;

The incident light coupling device 301 on the closed optical reflection cavity 302 can be realized as follows: a transmission incident surface is adopted, and an antireflection film matching the incident laser band is provided on the surface; or an incident aperture structure is adopted, and An optical coupling element such as a lens is disposed on the incident aperture 304.

The speckle elimination device of the present invention can be applied to a laser projection display technology, for example, as shown in FIG. 6, applied to a Raster-Scanned Displays system, and the signal sources 601, 602, 603 are based on a two-dimensional image. The information of each pixel modulates the output power of the three primary color lasers 501, 502, 503 respectively; the three incident lasers are coupled to the speckle elimination device 300 of the present invention through the mirrors 504, 505, 506, modulated, and then exported through the exit surface. The lens 700 and the micro-scanning mirror (Scan Mirror 701 project to the screen 800. The micro-scanning mirror 701 scans the screen on a pixel-by-pixel basis according to the two-dimensional image driven by the electric signal. This application example is suitable for point scanning laser projectors and lasers TV display.

As shown in FIG. 7, the system is applied to a Full-Frame Displays system, and the three primary color lasers 501, 502, and 503 output a constant power laser beam, and are respectively introduced into the speckle elimination device 305, 306 of the present invention. After being modulated, the relay lenses 701, 704, 707, the plane mirror 708, and the TIR prisms 703, 705, 709 are condensed to the optical modulators DLP 702, 706, 710; the optical modulators DLP 702, 706, 710 are based on each frame. The 2-dimensional image information is modulated to produce a monochrome image; the three primary color images are blended by prism 711 and projected by lens 700 onto screen 800. This application example is suitable for laser projectors and laser TV displays based on optical modulators such as DMD and LCOS.

Claims

Claim

A speckle removal device based on Mie scattering and magnetron particle motion, comprising: a closed optical reflection cavity having an incident light coupling device (301) and a transmission exit surface (303);

(302), the closed optical reflection cavity (302) except for the inner wall of the transmission exit surface (303) is a "mirror" inner wall, and the closed optical reflection cavity (302) is filled with the entire closed optical reflection cavity.

a solution or sol (401) of (302), and a magnetic medium particle (402) whose linearity can cause Mie scattering of the incident laser is dispersed in the solution or sol (401); the closed optical reflection cavity (302) is disposed There is a magnetic field generating means for generating a magnetic field, and the electromagnet (308) of the magnetic field generator is disposed in the closed optical reflecting chamber (302).

2. The speckle reduction device based on Mie scattering and magnetron particle motion according to claim 1. The solution is an organic solution or an inorganic solution; and the sol is an aerosol or a sol.

3. The speckle reduction device based on Mie scattering and magnetron particle motion according to claim 1, wherein: the magnetic medium particles (402) are made of polystyrene magnetic microspheres or silica magnetic microspheres. Or ferroferric oxide magnetic microspheres, or ferric oxide magnetic microspheres.

4. The speckle reduction device based on Mie scattering and magnetron particle motion according to claim 1, wherein: the surface of the transmission exit surface (303) of the closed optical reflection cavity (302) is provided with an incident beam band Matching AR coating.