WO2012100643A1

WO2012100643A1 - Speckle removal device based on mie scattering and optical part

Info

Publication number: WO2012100643A1
Application number: PCT/CN2012/000042
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: CN102053382B; CN102053382A

Abstract

Disclosed is a speckle removal device (300) based on Mie scattering and an optical part. The speckle removal device (300) comprises: an optical reflective chamber (302) disposed with an incident optical coupler device (301) and an emergent surface (303), and an optical part (308) disposed facing the incident optical coupler device (301) of the optical reflective chamber (302). The optical part (308) is an optical part that changes the incident angle of light beams. The inner walls of the optical reflective chamber (302) are all mirrors except the inner wall of the emergent surface. The inside of the optical reflective chamber (302) is completely filled with a transparent solid matter (401), and dispersed inside of the transparent solid matter (401) are medium particles (402) that trigger Mie scattering on an incident laser. The speckle removal device (300) has a compact structure, high speckle removal effect, high laser utilization rate, and stability, and makes illumination even.

Description

Speckle elimination device based on Mie scattering and optical device

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 optical devices, mainly for laser display technology and optical speckle phenomenon existing in optical instruments.

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 light energy distribution 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, Chinese Patent No. 200820122639.7 discloses "a scattering-based dephasing debranching device", which requires that the diameter of the use must be less than A scattering medium of particles of one-tenth 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 ZnSO^ solution) is used as a scattering medium, and an inorganic salt or an aqueous solution of an organic alcohol is present in the form of a hydrated ion or a macromolecule, which is much smaller than the wavelength of the laser. 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 perform the splitting light Homogenize to homogenize the coherence. However, according to the technical method described in the application, the speckle was removed at room temperature by a light pipe filled with a saturated NaCl aqueous solution having a length of 50 mm. 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 optical devices 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 an optical device, comprising an optical reflection cavity provided with an incident light coupling device and a transmission exit surface, and an incident optical coupling device facing the optical reflection cavity An optical device; the optical device is an optical device capable of changing an incident angle when the light beam enters the optical reflection cavity of the optical reflection cavity; the inner wall of the optical reflection cavity except the inner wall of the transmission exit surface is a "mirror" inner wall (ie, the inner wall) It has high reflectivity and can "total reflection" of the laser beam incident on the optical reflection cavity. The optical reflection cavity is provided with a transparent solid material filling the entire optical reflection cavity, and the linear solid energy is dispersed in the transparent solid material. A medium particle that causes Mie scattering of incident laser light.

The optical device may employ a scanning micromirror, or a variable focus microlens.

When applied, as shown in Figures 5, 6, 8, and 9, the laser beam emitted by the laser source is modulated by an optical device (scanning micromirror or variable-focus microlens) and passed through the optical reflection cavity at different incident angles. Coupling The device is incident on the transparent solid material in the optical reflection cavity, and Mie scattering occurs with the medium particles dispersed in the transparent solid material (as shown in FIG. 4, when the incident laser 101 irradiates the dielectric particle 402 to Mie scattering, the incident The scattered light intensity of the 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 accounts for a small The portion, 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 medium particles 402, and is split into a plurality of intensities. Scattered light, while the scattered light scattering angle distribution is enlarged), split into a plurality of scattered light of different intensities, or reflected by the inner wall of the optical reflecting cavity, or again interact with the medium particles dispersed in the transparent solid matter to cause Mie scattering, The scattered light splits into more scattered light, which is emitted by the transmission exit surface of the optical reflective cavity after multiple Mie scattering; and the optical device makes the laser beam incident optically reflected The incident angle continuously changes, causing the scattered light obtained by scattering the incident laser beam at various moments to change direction and path in the transparent solid matter, and finally the phase distribution and scattering angle distribution of the scattered light emitted from the exit surface of the optical reflective 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 sets an optical reflection cavity, performs Mie scattering on the incident laser in the optical reflection cavity, performs scattering and splitting, and continuously changes the angle of the laser incident optical reflection cavity by the optical device, thereby randomly changing the scattering. The direction and path of the light beam in the optical reflection cavity, so that the exit surface of the optical reflection cavity distributes the scattered light of the incident laser with different phase distribution and scattering angle at different times; thus changing the spatial distribution of the speckle after projection, so that The speckle images are superimposed in the integration time of the human eye to obtain an image with uniform light energy distribution, thereby effectively eliminating 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 Figures 7 and 10, the image is scattered. The spot contrast is 3.72% and 3.91%, respectively, and the speckle removal effect is excellent; and the concentration of the medium particles in the transparent solid matter and the modulation state of the optical device can be improved (for example, the amplitude of the scanning micromirror angle, the focal length of the zoom lens) The magnitude of the change is to improve the speckle removal effect; the present invention performs "total reflection" on the incident laser in the optical reflection cavity, and the total light energy loss of the incident laser is minimal, ensuring high utilization of the laser, and in "total reflection" The purpose of the homogenization is achieved in the process; the components of the device of the invention are all solid, and there are no problems such as liquid leakage, sedimentation, suspension, etc., and the performance is stable, safe and reliable.

The invention has reasonable and compact structure, 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 schematic view showing another structure of the present invention;

Figure 4 is a diagram showing the angular distribution of light intensity of Mie scattering;

5 is a schematic view showing the state of the device according to the present invention when the scanning micromirror is incident on the laser at an angle; FIG. 6 is a schematic view showing the state of the device according to the present invention after the scanning micromirror changes the incident angle of the incident laser; FIG. The device shown eliminates the test result map obtained by speckle;

Figure 8 is a schematic view showing the state of the apparatus of the present invention when the variable focus microlens is incident on the laser at a certain focal length;

9 is a schematic view showing the state of the device of the present invention after the zoom lens is incident on the zoom lens; FIG. 10 is a view showing the test result obtained by using the device shown in FIG. 3 to eliminate speckle;

Figure 11 is a schematic view showing the application of the apparatus shown in Figure 2 in a point scan display system;

12 is a schematic diagram of an application of the apparatus shown in FIG. 3 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 light coupling device; 302-optical reflection cavity; 303-transmitting exit face; 304-incident light hole; 305, 306, 307-speckle elimination device; 308-optical device;

401-transparent solid matter; 402-media particles;

501, 502, 503-laser; 504, 505, 506-mirror;

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 and FIG. 3, the speckle elimination device based on Mie scattering and optics includes an optical reflection cavity 302 on which the incident light coupling device 301 and the transmission exit surface 303 are disposed, and the light incident cavity 302 is incident on the optical reflection cavity 302. The optical device 308 is provided by the coupling device 301; the optical device 308 is an optical device capable of changing the incident angle when the light beam enters the optical reflection cavity 302 into the optical coupling device 301; the optical reflective cavity 302 is the inner wall except the inner wall of the transmission exit surface 301. Both are "mirror" inner walls (ie, the inner wall has a high reflectivity characteristic, can "total reflection" of the laser beam incident into the optical reflection cavity), and the optical reflection cavity 302 is provided with a transparent solid substance 401 filling the entire optical reflection cavity 302. And the transparent solid material 401 is interspersed with medium particles 402 whose linearity can cause Mie scattering of the incident laser light. The optics 308 can employ a scanning micromirror, or a variable focus microlens.

In a specific implementation, the scanning micro-mirror may be a one-dimensional scanning micro-mirror or a two-dimensional scanning micro-mirror; the variable-focusing microlens may be a variable-focusing convex lens or a variable-focusing concave lens; the transparent solid substance 401 should be a transparent solid material having no transmission loss to the incident laser light, such as a polymer gel; the dielectric particle 402 may be a medium particle such as polystyrene microspheres or titanium dioxide particles (Ti0 ₂ ); The optical reflection cavity 302 is mostly made of metal, plane mirror, transparent plastic or glass, and the shape thereof is not particularly limited, and a tubular cavity is generally used; the transmission and exit surface 303 of the optical reflection cavity 302 is mostly made of transparent plastic or glass. And mostly rectangular, and the surface is provided with an anti-reflection film that matches the incident beam. The incident light coupling device 301 on the optical reflection cavity 302 can be realized as follows: a transmission incident surface is adopted, and an antireflection film matching the incident beam band is provided on the surface; or an incident optical hole structure is adopted, and The optical aperture 304 is provided with an optical coupling element such as a lens.

The speckle elimination device of the present invention can be applied to a laser projection display technology, for example, as shown in FIG. 11, 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 Mirrory 701 project to the screen 800. The micro-scanning mirror 701 scans the image on the screen pixel by pixel according to the two-dimensional image driven by the electric signal. This application example is suitable for point scanning laser projector and laser television Display.

As shown in FIG. 12, applied to a Full-Frame Displays system, the three primary color lasers 501, 502, 503 output a constant power laser beam, and are respectively coupled and introduced into the speckle elimination device 305, 306, 307 of the present invention. After modulation, the relay lenses 701, 704, 707, the plane mirror 708 and the TIR prisms 703, 705, 709 converge to the light modulators DLP 702, 706, 710; the light modulators DLP 702, 706, 710 according to each frame 2 The 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 modulation devices such as DMD and LCOS.

Claims

Claim

A speckle reduction apparatus based on Mie scattering and an optical device, comprising: an optical reflection cavity (302) having an incident light coupling device (301) and a transmission exit surface (303); Optical reflection cavity (302) optics (308) disposed in the incident light coupling device (301); the optical device (308) is an incident angle capable of changing the incident light coupling cavity (302) of the optical reflection cavity (302) The optical device; the optical reflective cavity (302) except for the inner wall of the transmission exit surface (301) is a "mirror" inner wall, and the optical reflective cavity (302) is provided with a transparent solid state filling the entire optical reflection cavity (302). The substance (401) and the transparent solid substance (401) are dispersed with medium particles (402) whose linearity can cause Mie scattering of the incident laser light.

2. The speckle reduction device based on Mie scattering and scanning micromirror according to claim 1, wherein: the surface of the transmission exit surface (303) of the optical reflection cavity (302) is provided with an increase in matching with the incident beam band. Through the membrane.

A speckle reduction apparatus based on Mie scattering and scanning micromirrors according to claim 1, wherein said optical device (308) is a scanning micromirror or a variable focus microlens.

A speckle reduction apparatus based on Mie scattering and scanning micromirrors according to claim 1, wherein said transparent solid matter (401) is a transparent solid substance having no transmission loss to incident laser light.

The speckle reduction apparatus based on Mie scattering and scanning micromirrors according to claim 1, wherein the medium particles (402) are polystyrene microspheres or titanium dioxide particles.