Composite speckle suppression miniature device

Abstract

The invention relates to a composite speckle suppression miniature device, which comprises a thin film deposited with scattering particles and a micro-vibration structure, and is characterized in that the micro-vibration structure comprises a U-shaped outer frame, and the lower part of the U-shaped outer frame is provided with a magnetic induction switching assembly; a strip-shaped groove is formed in the inner wall of the upper portion of the U-shaped outer frame, the thin film assembly comprises a magnetic outer frame and a thin film, scattering particles are deposited on the thin film, in the magnetic outer frame, and the magnetic outer frame is embedded in the strip-shaped groove in a sliding mode; the outer side of the U-shaped outer frame is provided with a signal source interface. According to the invention, the transmittance of laser energy is improved, the difference of speckle images in an exposure time range is increased through the design of the motion plane, the speckle suppression efficiency is improved, the switching plane is easy to replace, the adopted devices are replaceable, the universality is high, the application range is wide, and the cost is effectively reduced; according to the invention, the spatial coherence is reduced, the time coherence is reduced, and the high brightness and definition of the micro-projection system in a small angle range are further improved.

Description

Technical Field

[0001] The present invention relates to the field of laser display, especially the field of micro-projection. Specifically, it relates to a composite speckle suppression micro-device. Background Art

[0002] Laser light sources have high brightness, wide color gamut, and high coherence, and are often used as the best imaging carriers in the display field. In laser display technology, due to the multiple scattering phenomenon caused by the surface roughness of the object being measured, an interference effect will be generated in the optical path, forming unevenly distributed speckles. These speckles will cover image details, reducing the resolution and imaging quality. As laser display systems develop towards miniaturization, the negative impact of speckles on image quality becomes more significant, becoming the main obstacle restricting the improvement of the imaging accuracy of micro-display systems. Therefore, for miniaturized display systems, it is particularly urgent to develop effective speckle suppression technologies.

[0003] In the field of laser display technology, speckle suppression strategies mainly reduce the spatial coherence, temporal coherence of the laser, or a combination of both. Currently, the main methods for coherent suppression and improving imaging brightness in visible light include random phase plates, microlens arrays, scanning micromirrors, rotating diffusers, reflective diffusers, etc. In existing technologies, there are patents using scattering sheets, microlens arrays, and diffractive microstructures for speckle suppression, such as "A Light Uniformity and Speckle Suppression Device and a Laser Projection System (202310905002.4)", which includes multiple microlenses that respectively perform speckle suppression on the mirror spots imaged and magnified by the imaging lens (301); "A Static Laser Speckle Suppression System Combining a Multimode Optical Waveguide and a Diffractive Optical Device (201920010760.9)", which uses different diffracted light beams of the diffractive optical device to irradiate into the multimode optical waveguide for beam splitting to achieve a static speckle suppression system; "A Double Scattering Sheet Laser Speckle Suppression Device (202410094937.3)", which respectively controls two optical glass sheets to vibrate in different directions. In these solutions, the microlens arrays, diffractive optical elements, and scattering sheets described as speckle suppression micro-devices mainly reduce the spatial coherence, and then dynamic elements can be used to reduce the temporal coherence, thereby achieving the effect of low speckles. However, they have the following problems in the process of achieving low speckles: 1. Since the movement of diffractive optical elements requires an external transmission device, it is difficult to miniaturize the speckle suppression device; 2. Since the microlens array will achieve surface focusing, it is difficult to achieve high brightness within a small angle range; 3. Since the light transmittance of the scattering sheet is poor, it is difficult to achieve high-definition imaging.

[0004] To solve the problems existing in the above-mentioned prior art, the prior art further provides a technical solution for achieving low speckle through a moving device. For example, in "A Device for Suppressing Laser Speckle in a Laser Display System (201720611037.7)", the vibration structure vibrates through its own coil with the assistance of an external permanent magnet. In "An Electromagnetic Vibration Device for a Screen Applied to a Laser Light Source Projection to Eliminate Speckle (201811023948.3)", the vibration units uniformly arranged on the screen are driven by electromagnetic force. In "A Speckle Suppression Movement Device Based on a Diffractive Optical Element (201811274730.5)", the transmission section is linked with the flexible variable-angle array diffractive optical microstructure. The vibration device mentioned above will still increase the volume of the overall device while achieving low speckle, and its structure is complex, which is not conducive to the imaging of a microdisplay system.

[0005] Therefore, there is still a need to strengthen the speckle suppression device that can achieve miniaturization, high brightness, and low speckle within a small angle range. Summary of the Invention

[0006] The present invention provides a composite speckle suppression micro-device to solve the problems in the prior art that the volume and structure are large and complex, which is not conducive to the imaging of a microdisplay system.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows:

[0008] A composite speckle suppression micro-device includes a thin film component deposited with scattering particles and a micro-vibration structure;

[0009] The micro-vibration structure includes a U-shaped outer frame, and a magnetic induction switching component is arranged at the lower part of the U-shaped outer frame;

[0010] Strip-shaped grooves are arranged on the inner wall of the upper part of the U-shaped outer frame. The thin film component includes a magnetic outer frame and a thin film deposited with scattering particles inside the magnetic outer frame, and the magnetic outer frame is slidably embedded in the strip-shaped grooves;

[0011] A signal source interface is arranged on the outer side of the U-shaped outer frame.

[0012] Further, the above magnetic induction switching component is a rotary electromagnet mechanism or a piezoelectric ceramic mechanism.

[0013] Further, the above rotary electromagnet mechanism is composed of a motor, a motor shaft, an electromagnet, and a crank-link mechanism. An electromagnet is installed on the upper part of the motor shaft, a crank-link mechanism is connected to the electromagnet, and the end of the crank-link mechanism is fixedly connected to the magnetic outer frame.

[0014] Further, slide rails are arranged in the strip-shaped grooves.

[0015] Further, the material of the above-mentioned thin film is BOPP and acrylate polymer, and the material of the scattering particles includes polymethyl methacrylate, polyethylene terephthalate, silicon dioxide, calcium fluoride particles, polypropylene or polyvinyl chloride.

[0016] Further, the above-mentioned thin film is adhesively fixed within a magnetic outer frame.

[0017] Further, a pair of magnetic cover plates are provided on the relatively facing surfaces of the lower part of the above-mentioned U-shaped outer frame.

[0018] Further, the above-mentioned U-shaped outer frame is made of aluminum alloy.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] 1. In the present invention, the diffractive optical element and the diffuser are improved to a thin film deposited with scattering particles. The thin film deposited with scattering particles serves as a moving switching plane. While ensuring its function of achieving uniform spatial light intensity distribution, the scattering angle distribution is controlled by the scattering particles. The spatial spacing of the distribution of the scattering particles improves the transmittance of laser energy, and the thin film deposited with scattering particles lays a foundation for miniaturizing the size of the speckle suppression device.

[0021] 2. The micro-vibration structure provided by the present invention effectively increases the coverage range of the moving switching plane. The design of this moving plane increases the difference in speckle images within the exposure time range, improves the speckle suppression efficiency, and the switching plane is easy to replace. The devices adopted are replaceable and have strong versatility, wide application range, and effectively reduce costs.

[0022] 3. In the present invention, the spatial coherence is reduced by using the thin film deposited with scattering particles as the particle scattering element, and the temporal coherence is reduced by the micro-vibration structure at the same time. Different sub-scattering points with different spatial distributions and small scattering angles are formed by using the particle scattering element, and then the imaging light intensities at different scattering positions are delayed and superimposed by using the micro-vibration structure to achieve the purpose of low spatio-temporal coherence. While the present invention achieves the high-efficiency speckle suppression effect of low spatio-temporal coherence, due to reducing the high coherence of the laser, it can reduce speckles from the source of speckle generation, achieve high-brightness imaging of the micro-projection system within a small angle range, and at the same time can further improve the high brightness and clarity of the micro-projection system within a small angle range.

[0023] 4. The particle scattering element of the present invention realizes a uniform spatial distribution within a controllable angle range, reducing the spatial coherence and the light loss of the device. The micro-vibration structure provided by the present invention can achieve multiple switches within the cycle range under an externally applied frequency signal. Therefore, the combination of the particle scattering element and the micro-vibration structure can reduce the temporal coherence by increasing the number of low-coherence or incoherent speckle patterns superimposed, and can reduce mechanical wear and the difficulties of uncontrollable mechanical structures. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of a system for realizing laser speckle suppression;

[0025] Figure 2 It is a schematic structural diagram of the present invention;

[0026] Figure 3 It is a motion process diagram of the micro-vibration structure of the present invention;

[0027] Figure 4 It is a theoretical diagram of speckle suppression of a composite speckle suppression micro-device of the present invention:

[0028] (a) Process of reducing spatial coherence by scattering particles, (b) Process of reducing temporal coherence by vibration to achieve pattern superposition;

[0029] Figure 5 It is a speckle pattern of a composite speckle suppression micro-device of the present invention in the working state;

[0030] (a) Speckle distribution without adding a composite speckle suppression micro-device of the present invention (b) Speckle distribution with adding a composite speckle suppression micro-device of the present invention;

[0031] The reference numerals are as follows:

[0032] 1 - Laser, 2 - Collimating lens, 3 - Optical filter, 4 - Telescope system, 5 - Diaphragm, 6 - Composite speckle suppression micro-device, 7 - Imaging lens, 8 - Projection screen, 9 - CCD camera, 10 - Computer processing system, 11 - Optical platform, 12 - U-shaped outer frame, 13 - Magnetic cover plate, 14 - Motor, 15 - Motor shaft, 16 - Electromagnet, 17 - Crank connecting rod mechanism, 18 - Signal source interface, 19 - Magnetic outer frame, 20 - Thin film, 21 - Large speckle pattern after imaging without adding particle scattering element, 22 - One pixel point, 23 - Small speckle pattern after imaging with adding particle scattering element, 24 - One speckle pattern superimposed within the exposure time range after imaging without adding micro-vibration structure, 25 - n speckle patterns superimposed within the exposure time range after imaging with adding micro-vibration structure. Specific embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments and the drawings.

[0034] Refer to Figure 1 , a system applied to realize laser speckle suppression is built according to the routine, including a laser 1, a collimating lens 2, an optical filter 3, a beam expander system 4, a diaphragm 5, a composite speckle suppression micro-device 6, an imaging lens 7, a projection screen 8, a CCD camera 9, a computer processing system 10 and an optical platform 11.

[0035] The laser beam emitted by the laser 1 is collimated, beam-expanded and calibrated through the modulation lens assembly (collimating lens 2, optical filter 3, beam expander 4, aperture 5), and is normally incident on a composite speckle suppression micro-device 6 provided by the present invention. The emitted light is incident on the imaging lens 7, and the imaging lens 7 corrects the scattered light to be nearly parallel and emits it onto the projection screen 8. The projection screen 8 records the laser micro-projection imaging, and the brightness and speckle distribution of the imaging pattern under vibration and non-vibration of the projection imaging pattern can be observed by the naked eye of a human. The CCD camera 9 records the micro-projection imaging result on the projection screen through the front-end imaging system, and the computer processing system 10 analyzes the speckle suppression situation by calculating the dynamic speckle contrast.

[0036] See Figure 2 , a composite speckle suppression micro-device, comprising a thin film assembly deposited with scattering particles and a micro-vibration structure. The micro-vibration structure includes a U-shaped outer frame 12, and a magnetic induction switching assembly is arranged at the lower part of the U-shaped outer frame 12; strip-shaped grooves are arranged on the inner wall of the upper part of the U-shaped outer frame 12, and slide rails are arranged in the strip-shaped grooves. The thin film assembly includes a magnetic outer frame 19 and a thin film 20 deposited with scattering particles inside the magnetic outer frame 19. The magnetic outer frame 19 is slidably embedded in the strip-shaped grooves to realize up and down movement along a fixed track.

[0037] A signal source interface 18 is arranged on the outer side of the U-shaped outer frame 12 to provide a signal to the magnetic induction switching assembly to control the action of the switching assembly, and then drive the thin film assembly to move up and down in the upper space of the U-shaped outer frame 12 for periodic motion.

[0038] In this embodiment, the magnetic induction switching assembly is a rotary electromagnet mechanism. The rotary electromagnet mechanism is composed of a motor 14, a motor shaft 15, an electromagnet 16 and a crank-link mechanism 17. The electromagnet 16 is installed on the upper part of the motor shaft 15, a crank-link mechanism 17 is connected to the electromagnet 16, and the end of the crank-link mechanism 17 is fixedly connected to the magnetic outer frame 19. See Figure 4 , when an external frequency signal is introduced into the signal source interface 18, the motor 14 works and the motor shaft 15 rotates, driving the electromagnet 16 on it to rotate in the horizontal direction. The rotational movement is converted into up and down movement through the end of the crank-link mechanism 17, so as to drive the magnetic outer frame 19 to move up and down. The thin film 20 inside the magnetic outer frame 19 follows to make up and down linear periodic motion, thus realizing the vibration motion process.

[0039] The material of the thin film 20 is BOPP and acrylate polymer, and the materials of the scattering particles deposited thereon include polymethyl methacrylate, polyethylene terephthalate, silicon dioxide, calcium fluoride particles, polypropylene or polyvinyl chloride. In this embodiment, the material of the selected scattering particles is polymethyl methacrylate; the thin film 20 is bonded and fixed within the magnetic outer frame 19. A pair of magnetic cover plates 13 are provided on the relatively facing surfaces at the lower part of the U-shaped frame 12 for closing the rotary electromagnet mechanism. The U-shaped frame 12 is made of aluminum alloy material.

[0040] See Figure 3 , the electromagnet 16 rotates in the horizontal direction, and the thin film 20 with scattering particles deposited therein within the magnetic outer frame 19 performs a linear periodic motion within the U-shaped outer frame 12, thereby realizing the vibration motion process.

[0041] See Figure 4 , laser direct imaging will generate a large speckle pattern 21. When no vibration element is introduced during the speckle suppression process, only one speckle pattern 24 will be superimposed within the exposure time T, and the speckles generated by the laser cannot be suppressed, thereby affecting the imaging effect. When using the device of the present invention, the laser will be incident on the thin film 20 deposited with scattering particles. The scattering microparticles will undergo multiple scatterings, and each scattering corresponds to a virtual sub-light source. The light emitted by a large number of virtual sub-light sources forms multiple small speckle patterns 23 on the imaging surface, and the small speckle patterns will be superimposed to form a uniform illumination light field. According to the Nyquist sampling theorem, the scattering process on the particle surface realizes that multiple speckle particles simultaneously fall within the same pixel point 22, generating the spatial averaging effect of the speckles, and will reduce the coherence in space. The introduction of the micro-vibration structure increases the number of n speckle patterns 25 superimposed within the exposure time T, and will reduce the coherence in time, thereby reducing the speckles simultaneously in both the time and space dimensions and improving the imaging quality.

[0042] Refer to Figure 5 , at a distance of 150 - 300 cm from the projection screen, with the corresponding externally applied frequency at 80 Hz, the speckle patterns are increased and the spatial scattering points are increased within the exposure time range of the human eye or CCD, destroying the temporal and spatial coherence of the laser, thereby achieving the suppression effect of low speckles, achieving high-brightness imaging with a transmittance of 90% within a small angle range of about 0 - 20°, and at the same time, the speckle contrast is less than 3%.

[0043] In the embodiment of the present invention, the transmittance of the thin film 20 deposited with scattering particles is greater than 80%, the absorption rate is less than 5%, the angle is less than 30°, the viscosity is greater than 80%, and the externally connected frequency signal input through the signal source interface 18 is less than 80 Hz.

[0044] The average particle size of the scattering particles is 0.5 - 10 μm, and the light transmittance is greater than 90%.

[0045] The scattering particles are distributed on the 80×80 μm element size surface, and poly(methyl methacrylate) microparticles with a particle size of 10 μm are randomly distributed. When the particle concentration should be 4 μm -2 , the coherence length of the corresponding particle scattering element is the smallest, the peak value of the correlation function decreases, the surface variance of the particle scattering element is the largest, and the corresponding coherence is the lowest. When the coherence length of the surface of the particle scattering element decreases, the speckle light intensity after scattering on the surface of the particle scattering element is enhanced, and thus the weakening of the speckle pattern correlation is realized more quickly, meeting the requirements of high forward scattering efficiency, forward scattering angles concentrated around 0-20°, high scattering light intensity uniformity, and high brightness. Then, the scattering particles deposit poly(methyl methacrylate) microparticles on the film 20 made of BOPP and acrylate polymers. Finally, the film 20 is bonded to the inner wall of the magnetic outer frame 19 by bonding, and the thickness of the film is 0.05-0.5 mm.

[0046] The remaining materials of the micro-vibration structure are made of aluminum alloy.

[0047] The above description is an illustration of the specific implementation of the present invention, rather than a limitation of the present invention. Those skilled in the relevant technical field can also make various equivalent technical solutions without departing from the scope of the present invention. Therefore, all equivalent technical solutions should be included in the protection scope of the present invention.

Claims

1. A composite speckle suppression micro-device, comprising a thin film component with scattering particles deposited thereon and a micro-vibration structure, characterized in that: The micro-vibration structure comprises a U-shaped outer frame (12), and a magnetic induction switching component is arranged at the lower part of the U-shaped outer frame (12); A strip-shaped groove is provided on the inner wall of the upper portion of the U-shaped outer frame (12); the film assembly comprises a magnetic outer frame (19) and a film (20) deposited with scattering particles inside the magnetic outer frame (19); the magnetic outer frame (19) is slidably embedded in the strip-shaped groove; and a signal source interface (18) is provided on the outer side of the U-shaped outer frame (12).

2. A composite speckle suppression micro-device according to claim 1, characterized in that: The magnetic induction switching component is a rotating electromagnet mechanism or a piezoelectric ceramic mechanism.

3. A composite speckle suppression micro-device according to claim 2, characterized in that: The rotating electromagnet mechanism is composed of a motor (14), a motor shaft (15), an electromagnet (16) and a crank-connecting rod mechanism (17); the electromagnet (16) is mounted on the upper part of the motor shaft (15); the crank-connecting rod mechanism (17) is connected to the electromagnet (16); and the end of the crank-connecting rod mechanism (17) is fixedly connected to a magnetic outer frame (19).

4. The composite speckle suppression micro-device according to claim 3, characterized in that: A slide rail is arranged in the strip-shaped groove.

5. The composite speckle suppression micro-device according to claim 4, characterized in that: The material of the film (20) is BOPP and acrylic polymers, and the material of the scattering particles includes polymethyl methacrylate, polyethylene terephthalate, silicon dioxide, calcium fluoride particles, polypropylene or polyvinyl chloride.

6. The composite speckle suppression micro-device according to claim 5, characterized in that: The film (20) is bonded and fixed inside the magnetic outer frame (19).

7. The composite speckle suppression micro-device according to claim 6, characterized in that: A pair of magnetic cover plates (13) are provided on opposite surfaces of the lower portion of the U-shaped outer frame (12).

8. The composite speckle suppression micro-device according to claim 7, characterized in that: The U-shaped outer frame (12) is made of aluminum alloy.

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