Laser projection system, laser speckle suppression method and optical display device

Abstract

The embodiment of the invention provides a laser projection system, a laser speckle suppression method and optical display equipment. The laser projection system comprises a laser light source module, an active electric tuning metasurface device, a control module and an imaging module. The laser light source module is used for providing an illumination light beam; the active electric tuning metasurface device is arranged on a light emitting path of the laser light source module and is used for carrying out phase modulation on an incident illumination light beam; the control module is electrically connected with the active electric tuning metasurface device and is used for applying an electric signal for sequential control to the device and driving the device to perform dynamic phase modulation on illumination light beams with different wavelengths in a time-sharing manner, so that an emergent light beam deflects at a preset angle theta; the imaging module is used for receiving the deflected light beam and forming an image; wherein the control module is used for controlling the active electric tuning metasurface device, so that light beams with different deflection states are uniformly superposed on a projection surface, and laser speckles are inhibited.

Description

Technical Field

[0001] This application relates to the field of optical display technology, and more specifically, to a laser projection system, a laser speckle suppression method, and an optical display device. Background Technology

[0002] Laser projection has been widely used in many projection scenarios due to its significant advantages such as high color gamut and long lifespan. However, the high coherence of lasers has become a key factor limiting its display effect. When using laser light sources for projection imaging, the image presented on the screen appears grainy to the human eye, a phenomenon known as laser speckle, which greatly reduces the quality of the displayed image and seriously affects the viewing experience.

[0003] Currently, several solutions exist for the laser speckle problem. For example, the mechanical jitter method alleviates speckle by shaking the projection screen or vibrating diffuser, but this method introduces moving parts, leading to noise and wear, thus reducing product reliability and lifespan. The rotating diffuser method disrupts coherence by dynamically changing the optical path difference, but requires a high-speed motor (typically 6000 rpm), consumes more than 3W, and generates electromagnetic interference. The static metasurface method uses fixed nanostructures to generate random phase distributions, but still requires moving parts, such as an electrically controlled micro / nano rotating stage.

[0004] Existing technologies suffer from a contradiction between "insufficient dynamic control precision" (mechanical jitter angle error ±0.5°) and "poor adaptability of static solutions." In particular, in miniaturized projection modules, it is difficult to achieve real-time speckle suppression at high frequencies (>1kHz) and low power consumption (<0.5W), which has become a bottleneck restricting the further development of laser projection technology. Summary of the Invention

[0005] The purpose of this application is to provide a new technical solution for a laser projection system, a laser speckle suppression method, and an optical display device, which aims to solve the laser speckle problem existing in the current laser projection technology.

[0006] In a first aspect, embodiments of this application provide a laser projection system, the laser projection system comprising: Laser source module, used to provide illumination beam; An active electrically tunable metasurface device is disposed in the light output path of the laser source module to perform phase modulation on the incident illumination beam; The control module is electrically connected to the active electrically tunable metasurface device and is used to apply a timing control electrical signal to the active electrically tunable metasurface device to drive it to dynamically phase modulate the illumination beams of different wavelengths in a time-division manner, so that the emitted beams deflect at the target angle. An imaging module is used to receive the deflected light beam and form an image; The control module controls the active electrically tunable metasurface device to uniformly superimpose light beams with different deflection states on the projection surface, thereby suppressing laser speckle.

[0007] Optionally, the active electrically tunable metasurface device comprises: ... (The sentence is incomplete and requires further context to be fully translated.) First transparent substrate; A first transparent electrode layer is formed on the first transparent substrate; A metasurface structure layer is disposed on the first transparent electrode layer and contains periodically arranged nanostructure units; A liquid crystal material layer covers the metasurface structure layer; A second transparent electrode layer is formed on the liquid crystal material layer; A second transparent substrate covers the second transparent electrode layer; The first transparent electrode layer and the second transparent electrode layer are used to receive electrical signals provided by the control module to form an electric field in the liquid crystal material layer, thereby achieving dynamic modulation of the beam phase by changing the orientation of the liquid crystal molecules in the liquid crystal material layer.

[0008] Optionally, the liquid crystal material layer uses two dual-frequency modulated liquid crystal materials formed with two different refractive indices, and the refractive index difference Δn between the two materials is 0.2~0.3. The control module is configured to control the orientation of liquid crystal molecules in the liquid crystal material layer by switching the frequency of the driving signal, wherein: In low-frequency driving mode, the liquid crystal molecules are aligned parallel to the direction of the electric field; In high-frequency driving mode, the liquid crystal molecules are aligned perpendicular to the direction of the electric field.

[0009] Optionally, the thickness of both the first transparent electrode layer and the second transparent electrode layer is 20nm~100nm, and both are patterned into a pixelated electrode array; Each electrode unit in the pixelated electrode array can be independently addressed to provide a driving voltage for one or more corresponding nanostructure units; by applying different driving voltages to each electrode unit, local independent control of the phase of the incident illumination beam can be achieved.

[0010] Optionally, the cross-section of the nanoscale structural unit of the metasurface structure layer is rectangular and satisfies the aspect ratio L / W > 1:1, where L is the length of the nanoscale structural unit and W is the width of the nanoscale structural unit.

[0011] Optionally, the aspect ratio L / W of the nanoscale structural unit is 1:1.8.

[0012] Optionally, the overall thickness of the active electrically tunable metasurface device is less than 1 μm.

[0013] Optionally, the control module includes: The calculation unit is used to calculate the target deflection angle. θ and φ The phase distribution on the surface of the actively tunable metasurface device is calculated using the following phase modulation function: Φ(x,y)=(2π / λ)(x·sin θ cos φ +y·sin θ ·sin φ ), where λ is the wavelength of the incident illumination beam, and (x,y) are the coordinate positions on the surface of the active electrically tunable metasurface device; The driving signal generation unit is used to convert the calculated phase distribution Φ(x,y) into a corresponding voltage control signal to drive each nanostructure unit of the metasurface structure layer and achieve the required spatial phase modulation.

[0014] Optionally, the imaging module includes a display unit and an optical lens group, wherein: The display unit is configured to receive and process the emitted light beam modulated by the active electrically tunable metasurface device. The optical lens group is used to focus and image the light beam output by the display unit to form a clear and speckle-free projected image on the projection surface.

[0015] Secondly, this application provides a laser speckle suppression method, which includes: An illumination beam is provided by a laser light source module and directed to an actively electrically tunable metasurface device; The control module applies a timing control electrical signal to the active electrically tunable metasurface device, driving the active electrically tunable metasurface device to perform time-segmented dynamic phase modulation on the incident illumination beam, thereby causing the outgoing beam to deflect at a preset angle. The imaging module receives the deflected outgoing beam and performs imaging. The active electrically tunable metasurface device is controlled by the control module to uniformly superimpose beams with different deflection states within a preset angle range, thereby suppressing laser speckle.

[0016] Thirdly, this application provides an optical display device comprising the laser projection system as described in the first aspect.

[0017] The beneficial effects of this application are as follows: Traditional laser projection systems often face the problem of laser speckle, which seriously affects the quality of projected images. Furthermore, some solutions to speckle rely on mechanical moving parts, which have drawbacks such as slow response speed, high energy consumption, poor system stability, and high integration difficulty.

[0018] The laser projection system provided in this application uses a control module to drive an active electrically tunable metasurface device to achieve time-division dynamic phase modulation of illumination beams of different wavelengths. This causes the emitted beam to deflect at the target angle and allows beams with different deflection states to be uniformly superimposed on the projection surface, effectively solving the laser speckle problem and significantly improving the quality of the projected image. Furthermore, the optical solution provided in this application requires no moving mechanical parts, offering advantages such as fast response speed, low energy consumption, high system stability, and ease of integration.

[0019] Other features and advantages of this specification will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of this specification and, together with their description, serve to explain the principles of this specification.

[0021] Figure 1 This is one of the structural schematic diagrams of the laser projection system provided in the embodiments of this application; Figure 2 This is a second schematic diagram of the structure of the laser projection system provided in the embodiments of this application; Figure 3 A diagram showing the relationship between the active electrically tunable metasurface device and the control module provided in the embodiments of this application; Figure 4 A schematic diagram illustrating the working principle of the laser source module provided in this application embodiment; Figure 5 This is a schematic diagram of the structure of the active electrically tunable metasurface device provided in the embodiments of this application; Figure 6 A schematic diagram of a metasurface structure layer of an active electrically tunable metasurface device provided in an embodiment of this application; Figure 7 This is a hardware block diagram of the control module for an active electrically tunable metasurface device provided in an embodiment of this application.

[0022] Explanation of reference numerals in the attached figures: 1. Laser source module; 2. Active electrically tunable metasurface device; 21. First transparent substrate; 22. First transparent electrode layer; 23. Metasurface structure layer; 24. Liquid crystal material layer; 25. Second transparent electrode layer; 26. Second transparent substrate; 3. Control module; 31. Calculation unit; 32. Drive signal generation unit; 4. Imaging module; 41. Display unit; 42. Optical lens group. Detailed Implementation

[0023] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0024] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0025] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0026] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0028] The following description, in conjunction with the accompanying drawings, details a laser projection system, a laser speckle suppression method, and an optical display device provided in the embodiments of this application.

[0029] According to one embodiment of this application, a laser projection system is provided, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, the laser projection system includes: a laser source module 1, an active electrically tunable metasurface device 2, a control module 3, and an imaging module 4. The laser source module 1 provides the illumination beam. The active electrically tunable metasurface device 2 is disposed in the output light path of the laser source module 1 and is used to phase modulate the incident illumination beam. See also... Figure 3 and Figure 4The control module 3, electrically connected to the active electrically tunable metasurface device 2, applies a timing-controlled electrical signal to the active electrically tunable metasurface device 2, driving it to dynamically phase-modulate illumination beams of different wavelengths in a time-division manner, causing the emitted beam to deflect at the target angle. The imaging module 4 receives the deflected beam and forms an image. The control module 3 controls the active electrically tunable metasurface device 2 to uniformly superimpose beams with different deflection states on the projection surface, thereby suppressing laser speckle.

[0030] The optical solution provided in this application aims to address the shortcomings of existing speckle suppression technology in laser projection systems. It provides a laser projection system based on an active electrically tunable metasurface device, which achieves low-voltage, high-speed, and wide-range beam deflection through electrically controlled phase modulation, thereby suppressing laser speckle.

[0031] This application provides a laser projection system for suppressing laser speckle. Its core design is to replace the traditional bulky mechanical moving parts with an electrically tunable ultrathin planar optical device, namely an active electrically tunable metasurface device 2. The wavefront phase of the beam is quickly changed electronically to produce a slight deflection. Finally, the unpleasant laser speckle is eliminated by superimposing multiple deflected images.

[0032] This application proposes a novel laser projection system design, the optical architecture of which is described in [reference needed]. Figure 1 and Figure 2 The laser projection system mainly consists of four core parts: a laser source module 1, an active electrically tunable metasurface device 2, a control module 3, and an imaging module 4. These parts work together to achieve high-quality laser projection and effectively suppress laser speckle. The following describes these four core parts.

[0033] The laser light source module 1 serves as the light source for the entire laser projection system. It is responsible for providing the illumination beam, which provides the necessary light source foundation for subsequent projection imaging.

[0034] Specifically, the laser light source module 1 possesses excellent light-emitting performance, capable of outputting high-brightness R (red), G (green), and B (blue) three-color laser beams. Based on this characteristic of the laser light source module, the laser projection system has significant advantages in color performance and brightness output, enabling it to present more vibrant and vivid image effects.

[0035] However, the inherent high coherence of laser light sources, while bringing advantages such as high brightness and wide color gamut, also introduces speckle problems. During laser projection, due to the high coherence of the laser beam, the projected image exhibits grainy speckle, severely reducing image clarity and viewing comfort. Therefore, how to effectively suppress laser speckle has become a core technical problem that this application urgently needs to solve and overcome.

[0036] The active electrically tunable metasurface device 2, as the core control component of the entire laser projection system, is located in the output optical path of the laser source module 1. It is responsible for dynamically and precisely modulating the phase of the incident illumination beam, achieving precise control over the beam propagation direction by changing the phase distribution of the light wave. This characteristic makes the active electrically tunable metasurface device 2 an indispensable and important component of the laser projection system of this application.

[0037] Specifically, the active electrically tunable metasurface device 2 is a phase modulator. It utilizes a designed array of nanostructures to modulate the passing light beam. When the illumination beam emitted by the laser source module 1 is incident on the surface of the active electrically tunable metasurface device 2, its nanostructures can precisely change the phase distribution of the beam wavefront. This change in phase distribution is equivalent to precise control of the light propagation direction. Through the phase modulation mode designed in this application, the active electrically tunable metasurface device 2 can cause the emitted beam to undergo a slight deflection (±θ, e.g., θ = 0.5°) according to preset requirements, see [link to relevant documentation]. Figure 1 and Figure 2 This allows for precise control over the direction of beam propagation.

[0038] The control module 3, as the core control unit of the laser projection system, is electrically connected to the active electrically tunable metasurface device 2 and is responsible for system regulation. The control module 3 generates and applies electrical signals with precise timing characteristics to drive the active electrically tunable metasurface device 2 to perform time-division dynamic phase modulation, thereby achieving precise control of the propagation direction of the emitted beam.

[0039] Specifically, the control mechanism of the control module 3 has two core characteristics: (1) Time-sequential control mechanism: The control module 3 adopts a time-sharing working mode, see [link to relevant documentation]. Figure 4 The red, green, and blue laser beams are independently modulated sequentially according to a preset time sequence (t1, t2, t3, ...). This timing control method ensures that each color laser beam can obtain the required phase modulation at precise time points, thereby achieving spatial separation and temporal multiplexing of the emitted beam on the projection surface.

[0040] (2) Pixelated Dynamic Modulation Technology: The control module 3 not only has timing control capabilities, but also achieves pixel-level phase modulation by dynamically adjusting the voltage or frequency signal applied to the active electrically tunable metasurface device 2. This dynamic modulation method can drive the active electrically tunable metasurface device 2 to generate continuously changing phase patterns, thereby enabling rapid and continuous dynamic adjustment of the beam deflection angle within a preset range. Its ultimate goal is to enable the emitted beam to achieve millisecond-level rapid switching between multiple preset angles, providing a guarantee for the uniform superposition of the beam on the projection surface.

[0041] The imaging module 4 is located at the end of the entire optical path system and is responsible for converting the modulated beam into a visual projected image. The imaging module 4 receives the beam deflected by the active electrically tunable metasurface device 2, and through photoelectric conversion and imaging processing, finally forms a clear image that conforms to the visual characteristics of the human eye. Its performance directly determines the viewing experience quality of the end user.

[0042] From a technical implementation perspective, the imaging module 4 is constructed using mainstream projection display technology. Its configuration includes a DLP optical engine based on DMD (Digital Micromirror Device) or an LCD optical engine system based on LCD (Liquid Crystal Panel), which can be referred to separately. Figure 1 and Figure 2 Among them, the LCD optical-mechanical system based on LCD (liquid crystal panel) is referred to... Figure 1 It features a transmissive optical path design. For DLP optomechanics based on DMD (Digital Micromirror Device), see [link to relevant documentation]. Figure 2 It features a reflective optical path design.

[0043] Once the deflected light beam enters the imaging module 4, the DMD device achieves pixel-level optical switching control through the rapid flipping of millions of micromirrors, or the LCD panel achieves light intensity attenuation through the adjustment of liquid crystal molecule orientation. Both technical approaches can convert the light beam carrying phase modulation information into a projection beam containing complete image data, ultimately forming a high-contrast, low-noise, high-quality image on the projection screen. This process, through precise optical alignment and signal synchronization design, ensures the accuracy of the entire signal chain from beam modulation to image generation.

[0044] In terms of technical implementation, the laser projection system provided in this application achieves precise control of the active electrically tunable metasurface device 2 through the control module 3, enabling beams with different deflection states to be uniformly superimposed on the projection surface. This superposition effect effectively breaks the coherence of the laser beam, thereby significantly suppressing laser speckle and improving the overall quality of the projected image.

[0045] Driven by the control module 3, the active electrically tunable metasurface device 2 can rapidly and periodically switch the same beam of light between multiple tiny deflection angles.

[0046] Because of the integration time of the human eye and image sensors (the persistence of vision), each individually deflected image cannot be seen. What the user actually sees is the result of multiple images with the same content but different speckle patterns being superimposed and averaged over a short period of time.

[0047] Laser speckle is essentially random bright and dark interference spots. When multiple different speckle patterns are rapidly superimposed, their random bright and dark details are "smoothed out," thus significantly reducing the graininess of the image on a macroscopic scale and achieving the effect of speckle elimination.

[0048] In summary, the workflow of the laser projection system provided in this embodiment is as follows: Laser source module 1 emits an illumination beam (laser) → The illumination beam illuminates the active electrically tunable metasurface device 2 → Control module 3 applies a rapidly changing electrical signal to the active electrically tunable metasurface device 2 → The active electrically tunable metasurface device 2 dynamically modulates the phase of the beam, causing it to deflect slightly → The deflected beam enters the imaging module 4 and forms an image → The image is projected onto the projection surface. Due to the continuous change in the deflection angle, multiple speckle patterns are rapidly superimposed and merged into a clear, grain-free image in the human eye.

[0049] The advantages of the method provided in this application are: no mechanical moving parts (high reliability, no noise, long life), extremely fast response speed (down to microsecond level, far higher than mechanical vibration), extremely low power consumption (only needs to drive the liquid crystal and circuit, no motor is required), and compact overall structure (the metasurface is very thin, which is conducive to system miniaturization).

[0050] The laser projection system provided in this application solves the speckle problem in laser projection. Traditional methods often rely on mechanical moving parts, which have drawbacks such as slow response speed, high energy consumption, and poor stability. In contrast, this system requires no mechanical movement and achieves precise modulation and superposition of the beam through electronic control, fundamentally eliminating the negative impact of speckle on projection quality.

[0051] Thanks to the significant suppression of laser speckle, the graininess of the projected image is greatly reduced, resulting in a smoother and clearer picture. This not only enhances the user's viewing experience but also expands the application potential of laser projection technology in demanding display scenarios.

[0052] The active electrically tunable metasurface device 2 in this application, driven by the control module 3, can achieve fast and precise phase modulation. Compared with mechanical adjustment, this electronic control method has a faster response speed and lower energy consumption, which helps to improve the overall energy efficiency ratio of the system.

[0053] By eliminating complex moving mechanical parts, the laser projection system provided in this application has a simpler and more robust structure, reducing the risk of failure due to mechanical wear and vibration. At the same time, the compact optical path design facilitates system integration and installation, lowering the requirements for the operating environment.

[0054] See some examples in this application. Figure 5 The active electrically tunable metasurface device 2 comprises the following parts stacked sequentially: First transparent substrate 21; A first transparent electrode layer 22 is formed on the first transparent substrate 21; The metasurface structure layer 23 is disposed on the first transparent electrode layer 22 and contains periodically arranged nanostructure units. A liquid crystal material layer 24 covers the metasurface structure layer 23; A second transparent electrode layer 25 is formed on the liquid crystal material layer 24; The second transparent substrate 26 covers the second transparent electrode layer 25; The first transparent electrode layer 22 and the second transparent electrode layer 25 are used to receive electrical signals provided by the control module 3 to form an electric field in the liquid crystal material layer 24, thereby achieving dynamic modulation of the beam phase by changing the orientation of the liquid crystal molecules in the liquid crystal material layer 24.

[0055] The example provided in this application details the layered stacked structure of the active electrically tunable metasurface device 2. The active electrically tunable metasurface device 2 is a meticulously designed "sandwich" electro-optic modulator, the core of which lies in integrating the powerful wavefront modulation capability of the metasurface with the electrically tunable characteristics of the liquid crystal material.

[0056] The following is a detailed breakdown of each layer of the structure and an explanation of its functional principles: (1) Regarding the first transparent substrate 21 and the second transparent substrate 26: The first transparent substrate 21 serves as the bottom support structure of the active electrically tunable metasurface device 2. For example, it can be made of glass or quartz material with high light transmittance (>90%), and its thickness is controlled in the range of 0.5 mm to 1.1 mm. The substrate needs to have excellent optical transparency to reduce the transmission loss of the incident light beam.

[0057] The second transparent substrate 26 serves as the top-level encapsulation structure of the active electrically tunable metasurface device 2. It is made of a high-transmittance material of the same origin as the first transparent substrate 21, and its thickness is controlled, for example, within the range of 0.3 mm to 0.7 mm. Its functions include: 1) physically isolating and protecting the internal liquid crystal material layer 24 and each electrode layer from environmental moisture, mechanical scratches, etc.; 2) maintaining the overall structural rigidity of the device and preventing interlayer misalignment caused by temperature changes or external forces; 3) forming a parallel planar structure in conjunction with the first transparent substrate 21 to ensure that the incident light beam maintains minimal wavefront distortion when propagating inside the device.

[0058] The first transparent substrate 21 and the second transparent substrate 26 serve as the mechanical support for the entire active electrically tunable metasurface device 2, providing flatness and stability to ensure precise alignment and integration of each functional layer. Their "transparent" nature ensures that the illumination beam can efficiently penetrate the entire device.

[0059] (2) Regarding the first transparent electrode layer 22 and the second transparent electrode layer 25: Both the first transparent electrode layer 22 and the second transparent electrode layer 25 are, for example, made of indium tin oxide (ITO) thin film material, with their thicknesses controlled in the nanometer range of 20 nm to 100 nm. The first transparent electrode layer 22 is uniformly deposited on the surface of the first transparent substrate 21 using a magnetron sputtering process. The second transparent electrode layer 25 can be symmetrically deposited on the inner side of the second transparent substrate 26 using the same process, forming a parallel-plate capacitor structure that sandwiches the liquid crystal material layer 24.

[0060] The first transparent electrode layer 22 and the second transparent electrode layer 25 can be simply referred to as electrode layers. The core function of these two electrode layers is: Electric field construction: By receiving the timing electrical signal output by the control module 3, a uniform electric field perpendicular to the substrate plane is formed in the liquid crystal material layer 24, driving the dynamic change of liquid crystal molecule orientation; Pixelated control: The electrode layer is patterned into a microelectrode array, with each nanostructure unit corresponding to an independently addressed microelectrode, enabling precise control of the local electric field strength and frequency. This spatially programmable characteristic allows the device to perform nanometer-level phase modulation of the incident beam, providing a physical basis for complex wavefront manipulation such as beam deflection and speckle suppression.

[0061] The symmetrical design of the dual electrode layer ensures the uniformity of the electric field distribution. At the same time, the microelectrode array corresponds one-to-one with the nanostructure units of the metasurface structure layer 23, forming a synergistic modulation mechanism of "electric control-structure resonance".

[0062] (3) Regarding the metasurface structure layer 23 and the liquid crystal material layer 24: The metasurface structure layer 23 is composed of periodically arranged nanostructure units (such as nanopillars, nanopores, etc.), whose geometric parameters (such as periodicity P) are... x / P Length L, width w, etc., see Figure 6 Through optimized design, it can resonate with incident light of a specific wavelength. The core function of this metasurface structure layer 23 is: Geometrically induced orientation: Through the periodic arrangement of nanostructures, liquid crystal molecules are guided to form a specific orientation distribution in the initial state, replacing the traditional alignment layer and reducing the threshold voltage; Synergistic phase modulation: When the orientation of liquid crystal molecules is changed by electric field modulation, the metasurface structure and the dynamic refractive index change form a coupled resonance, which amplifies the phase modulation depth through near-field enhancement effect, and realizes efficient wavefront modulation under low voltage.

[0063] This synergistic design of structure and materials enables the metasurface structure layer 23 and the liquid crystal material layer 24 to jointly form a dynamically adjustable phase modulation unit, providing a physical basis for applications such as beam deflection and speckle suppression.

[0064] The liquid crystal material layer 24 employs a dual-frequency tunable liquid crystal material, such as dual-frequency tunable liquid crystal DP002-016, whose dielectric anisotropy (Δε) can be switched by driving the frequency. Under the influence of an electric field, the orientation angle (φ) of the liquid crystal molecules dynamically changes, resulting in an effective refractive index (Δn). LC The phase is changed, thereby achieving phase modulation (ΔΦ=(2π / λ)·d·Δn). LC This design enhances the refractive index change through near-field amplification, enabling significant phase shifts to be generated even at low voltages.

[0065] Electrically controlled refractive index change: The orientation of liquid crystal molecules determines their effective refractive index. When a voltage is applied to the upper and lower electrodes to create an electric field, the orientation angle (φ) of the liquid crystal molecules is changed. This change in molecular orientation directly leads to a change in the refractive index (n).

[0066] Dual-frequency drive is key to achieving fast response. Control module 3 changes the dielectric anisotropy (Δε) sign of liquid crystal molecules by switching the drive frequency (e.g., 20kHz low frequency and 200kHz high frequency).

[0067] Low-frequency drive (Δε>0): Molecules tend to align parallel to the direction of the electric field (φ→0°).

[0068] High-frequency drive (Δε<0): Molecules tend to align perpendicular to the direction of the electric field (φ→90°).

[0069] This bidirectional active control breaks through the slow relaxation process of traditional liquid crystals that rely solely on elastic recovery, shortening the shutdown time to below 800μs and meeting the projection system's demand for high-speed modulation.

[0070] For example, the birefringence difference Δn of the liquid crystal material layer 24 is 0.268, where: n e =1.779, n o =1.511@589nm.

[0071] The working principle and modulation mechanism of the active electrically tunable metasurface device 2 provided in this application example are described below: (1) Regarding electric field driving and liquid crystal response: The control module 3 applies timing electrical signals (20kHz low frequency / 200kHz high frequency) to the first transparent electrode layer 22 and the second transparent electrode layer 25, forming a vertical and uniform electric field in the liquid crystal material layer 24. For example, at low frequency Δε>0, the liquid crystal molecules align parallel to the electric field (φ=0°); at high frequency Δε<0, the molecules align perpendicular to the electric field (φ=90°). By switching frequencies, a bidirectional fast response of molecular orientation is achieved (the off time is shortened to 800μs).

[0072] (2) Synergistic enhancement effect of metasurfaces: The nanostructure of the metasurface structure layer 23 forms a coupled resonance with the orientation of the liquid crystal molecules: Geometrically induced orientation: The periodic arrangement of nanostructures guides the initial orientation of liquid crystal molecules, reducing the requirements of traditional alignment layers and lowering the threshold voltage by more than 50%.

[0073] Near-field amplification: Metasurface localized field enhancement amplifies changes in the refractive index of liquid crystals, improving modulation efficiency.

[0074] Dual-frequency electrically controlled rotation: Combining electric field frequency switching with metasurface resonance, it achieves low-voltage (<3.5Vrms) and high-speed (<1ms) phase dynamic tuning.

[0075] (3) Phase modulation and beam deflection: Based on the polarization state (θ, φ) of the incident light, the formula Φ(x,y)=(2π / λ)(x·sin θ cos φ +y·sin θ ·sin φ The phase distribution is calculated. The control module adjusts the electric field parameters in a 3-minute time division, so that the emitted beam switches rapidly between preset angles (±θ) to achieve uniform light intensity superposition required for speckle suppression.

[0076] This application designs an active electrically tunable metasurface device 2, which enables the entire system to have no mechanical moving parts, thus eliminating vibration and wear problems in traditional solutions and improving system reliability.

[0077] This application achieves low-voltage, high-speed modulation by designing an actively tunable metasurface device 2. The synergistic effect of dual-frequency drive and metasurface reduces the modulation voltage to below 0.6 Vrms, with a response speed of <1 ms.

[0078] The thickness of the multi-layer thin film structure is controllable (total thickness is about a few micrometers), which is suitable for the needs of micro projection modules.

[0079] The RGB three-color beams are independently deflected by timing phase modulation, forming a uniform light field with low speckle on the projection surface.

[0080] As can be seen, the design in this example solves the contradiction between insufficient dynamic control precision and poor adaptability of static schemes in traditional laser projection through the synergy of materials, structure and electric field, and provides a technical breakthrough for real-time speckle suppression with high frequency and low power consumption.

[0081] The method for manufacturing the active electrically tunable metasurface device 2 provided in this application includes the following steps: A first transparent substrate 21 is provided and a first transparent electrode layer 22 is fabricated thereon; A metasurface structure layer 23 containing periodic nanostructures is formed on the first transparent electrode layer 22; A liquid crystal material layer 24 is prepared on the metasurface structure layer 23; A second transparent substrate 26 is provided and a second transparent electrode layer 25 is fabricated thereon; The second transparent substrate 26 is assembled opposite to the first transparent substrate 21 with its second transparent electrode layer 25 facing the liquid crystal material layer 24, so that the liquid crystal material layer 24 is sealed between the two transparent electrode layers. The device is packaged to form a complete active electrically tunable metasurface device.

[0082] In some examples of this application, the liquid crystal material layer 24 employs a dual-frequency modulated liquid crystal material formed from two different refractive indices, with a refractive index difference Δn of 0.2 to 0.3. The control module 3 is configured to control the orientation of liquid crystal molecules in the liquid crystal material layer 24 by switching the frequency of the driving signal, wherein: In low-frequency driving mode, the liquid crystal molecules are aligned parallel to the direction of the electric field; In high-frequency driving mode, the liquid crystal molecules are aligned perpendicular to the direction of the electric field.

[0083] In the example of this application, the liquid crystal material layer 24 uses a dual-frequency modulated liquid crystal material, whose core characteristics are: Material parameters: It is composed of two liquid crystal materials with a refractive index difference Δn of 0.2 to 0.3. This refractive index difference can significantly enhance the beam phase modulation depth; The specific driving mechanism is as follows: Low-frequency mode (20kHz): When the control module 3 applies a low-frequency electrical signal, the liquid crystal molecules exhibit dielectric anisotropy (Δε>0), and the molecular axes are aligned parallel to the electric field direction (orientation angle φ=0°). At this time, the equivalent refractive index of the liquid crystal layer is low, corresponding to a blue shift in transmission resonance. High-frequency mode (200kHz): After switching to a high-frequency electrical signal, Δε < 0, the molecular axis is perpendicular to the electric field direction (φ = 90°), the equivalent refractive index increases, and the resonance redshift occurs.

[0084] Dynamic control effect: Through frequency switching (20kHz) At 200 kHz, the liquid crystal molecule orientation rapidly switches between parallel / perpendicular states (response time < 800 μs). Combined with the geometrically induced resonance effect of metasurface structure layer 23, efficient phase modulation (ΔΦ = (2π / λ)·d·Δn) is achieved under low voltage (0.6~3.5 Vrms). LC ).

[0085] This design utilizes dual-frequency drive to overcome the limitations of traditional unidirectional rotation of liquid crystals, enabling a single device to simultaneously meet the requirements of high-frequency (>1kHz) response and low power consumption (<0.5W), providing key technical support for real-time speckle suppression in the projector's optical path system.

[0086] In some examples of this application, the thickness of both the first transparent electrode layer 22 and the second transparent electrode layer 25 is 20 nm to 100 nm, and both are patterned as pixelated electrode arrays. Each electrode unit in the pixelated electrode array can be independently addressed to provide a driving voltage for one or more corresponding nanostructure units; by applying different driving voltages to each electrode unit, local independent control of the phase of the incident illumination beam can be achieved.

[0087] In the example provided in this application, the first transparent electrode layer 22 and the second transparent electrode layer 25 are made of indium tin oxide (ITO) thin film material with a thickness of 20nm to 100nm, and are patterned into a pixelated electrode array by photolithography. Their functions and control mechanisms are as follows.

[0088] Regarding electrode structure characteristics: (1) Array design of electrode layer: The electrode layer (the first transparent electrode layer 22 and the second transparent electrode layer 25 can be referred to as the electrode layer) is divided into many (e.g. tens of thousands) independent addressable microelectrode units. Each microelectrode unit corresponds to one or more nanostructure units (e.g., nanopillars / pores) in the metasurface structure layer 23, forming a one-to-one or one-to-many spatial mapping relationship of "microelectrode unit-nanostructure unit".

[0089] (2) Electrode layer thickness design: The thickness of the indium tin oxide (ITO) thin film material is 20nm to 100nm, while ensuring the light transmittance (>90%) and controlling the electrode resistivity at, for example, 10. -4 The voltage is on the order of Ωcm, ensuring uniformity of voltage drive.

[0090] Regarding the independent addressing control mechanism: (1) Voltage distribution: The control module 3 applies an independent driving voltage of 0.6V to 3.5Vrms to a specific microelectrode unit through the row and column driving circuit to form a local electric field in the liquid crystal material layer 24.

[0091] (2) Phase modulation principle: Under different voltages, the orientation angle φ of liquid crystal molecules changes continuously (0≤φ≤90°), resulting in an effective refractive index Δn LC (V) according to Δn LC (V ) =ne-no∝cos²φ(V) Dynamically adjusted, combined with the metasurface structure resonance effect, to achieve control of the beam phase in the corresponding region (ΔΦ=(2π / λ)·d·Δn) LC ).

[0092] Regarding the implementation of wavefront regulation: (1) Spatial resolution: The pixel size can be as small as 5μm×5μm, supporting local phase modulation of the incident beam with nanometer precision.

[0093] (2) Dynamic response: By switching the orientation direction of liquid crystal molecules through dual-frequency drive (20kHz / 200kHz) and in conjunction with voltage amplitude adjustment, a fast response (<800μs) and a wide range of continuous adjustment (0~2π) of phase modulation can be achieved.

[0094] This design breaks through the spatial resolution limitations of traditional overall control methods by driving the electrode array pixel by pixel, providing a technical basis for real-time dynamic control of complex wavefronts (such as speckle removal and beam deflection) in the projector optical path system.

[0095] See some examples in this application. Figure 6The cross-section of the nanoscale structural unit of the metasurface structure layer 23 is rectangular and satisfies the aspect ratio L / W > 1:1, where L is the length of the nanoscale structural unit and W is the width of the nanoscale structural unit.

[0096] The nanoscale structural units of the metasurface structure layer 23 are cubic in shape with rectangular cross-sections and an aspect ratio L / W > 1:1 (L is the length and W is the width). This ratio is designed to optimize the resonance effect with incident light by adjusting the geometric parameters of the rectangular nanoscale structural units.

[0097] The aspect ratio of rectangular cross-section nanoscale structural units directly affects their electromagnetic response characteristics. When L / W > 1:1, nanoscale structural units can excite a stronger electric field localization effect at a specific wavelength, enhancing the coupling efficiency with the orientation changes of liquid crystal molecules, thereby increasing the phase modulation depth.

[0098] The rectangular structure is easy to fabricate with high precision (linewidth accuracy <10nm) using electron beam lithography or nanoimprint lithography, and the aspect ratio can be flexibly adjusted to adapt to different working wavelengths (such as 670nm red light and 532nm green light).

[0099] This ratio range allows for optimization of the refractive index modulation range according to actual needs, such as achieving Δn by adjusting L / W under low voltage drive (0.6~3.5Vrms). LC(V) The linear response range is extended.

[0100] It should be noted that the nanoscale structural units of the metasurface structure layer 23 described in this application are not limited to a single geometric shape, and their design scope includes, but is not limited to, a single geometric shape. Figure 6 The cubic structure is shown. In actual implementations, the nanoscale structural unit can be flexibly selected from the following geometric configurations, such as cylindrical / elliptical cylinders, depending on the operating wavelength, modulation requirements, and process compatibility.

[0101] In some examples of this application, the aspect ratio L / W of the nanoscale structural unit is 1:1.8.

[0102] In this application, the aspect ratio L / W of the nanoscale structural unit is further optimized to 1:1.8. This ratio, verified through simulation and experiments, can significantly improve the metasurface-liquid crystal synergistic modulation efficiency.

[0103] When L / W is 1:1.8, the equivalent dielectric constant of the nanoscale structural unit is optimally matched with the dielectric anisotropy (Δε) of the liquid crystal material layer 24 (dual-frequency tunable liquid crystal DP002-016), making the electric field energy more concentrated in the liquid crystal material layer 24 and improving the phase modulation sensitivity.

[0104] Under the optimized ratio proposed in this example, the response curve of the liquid crystal molecule orientation angle φ to voltage is closer to linear (nonlinearity < 5%), and more precise phase control can be achieved in the voltage range of 0.6~3.5Vrms.

[0105] The arrangement of the nanoscale structural units with an L / W ratio of 1:1.8 can significantly reduce speckle contrast while maintaining a response time of <800μs.

[0106] The basic resonance modulation capability is provided by a rectangular design with an aspect ratio of L / W > 1:1, while breakthroughs are achieved in phase modulation sensitivity, linear response and speckle suppression performance by optimizing the L / W ratio to 1:1.8.

[0107] In some examples of this application, the overall thickness of the active electrically tunable metasurface device 2 is less than 1 μm.

[0108] In this example of the application, the active electrically tunable metasurface device 2 reduces its overall thickness to <1 μm by optimizing the integration design of the metasurface structure layer 23 and the liquid crystal material layer 24. Specifically, the metasurface structure layer 23 has a thickness of approximately 300 nm, the liquid crystal material layer 24 has a thickness of approximately 500 nm, and the total thickness of the two transparent electrode layers (ITO) is <50 nm. This ultrathin structure, combined with the synergistic design of nanoscale geometric parameters (such as rectangular units with an aspect ratio of L / W=1:1.8) and the resonant enhancement effect of the dual-frequency liquid crystal material (Δn=0.28), achieves low-voltage drive (0.6~3.5Vrms), high-frequency response (<800μs), and high phase modulation accuracy while reducing the device size. Its beneficial effects include: overcoming the limitations of traditional speckle suppression technology on space and power consumption, enabling the micro-projector optical path system to maintain high resolution while reducing both size and power consumption, significantly improving system integration and reliability.

[0109] See some examples in this application. Figure 7 The control module 3 includes: Calculation unit 31 is used to calculate based on the target deflection angle. θ and φ The phase distribution on the surface of the active electrically tunable metasurface device 2 is calculated using the following phase modulation function: Φ(x,y)=(2π / λ)(x·sin θ cos φ +y·sin θ ·sin φ ), where λ is the wavelength of the incident illumination beam, and (x,y) are the coordinate positions on the surface of the active electrically tunable metasurface device 2; The driving signal generation unit 32 is used to convert the calculated phase distribution Φ(x,y) into a corresponding voltage control signal to drive each nanostructure unit of the metasurface structure layer 23 and achieve the required spatial phase modulation.

[0110] In the example provided in this application, the control module 3 achieves precise dynamic control of the beam phase by the active electrically tunable metasurface device 2 through the coordinated operation of calculation and drive. The specific process is as follows: Calculation Unit 31: Based on the target deflection angle (θ is the polar angle of deflection, φ is the azimuth angle) and the incident light wavelength (λ), the formula Φ(x,y)=(2π / λ)(x·sin θ cos φ +y·sin θ ·sin φ This function calculates the required phase value at each coordinate point (x, y) on the surface of the active electrically tunable metasurface device 2. It directly correlates spatial position with phase offset, ensuring the beam deflects at a set angle.

[0111] The driving signal generation unit 32 converts the calculated phase distribution Φ(x,y) into a voltage control signal to drive the nanostructure units at the corresponding positions in the metasurface structure layer 23. For example, if a certain region requires a phase delay of π, the driving voltage (0.6~3.5Vrms) of the liquid crystal material layer 24 in that region is adjusted to change the orientation of the liquid crystal molecules to achieve the target refractive index, ultimately forming a spatial phase modulation wavefront.

[0112] This application achieves rapid beam deflection (<800μs response) and speckle suppression without mechanical movement, significantly improving the image quality and reliability of the projection system.

[0113] See some examples in this application. Figure 1 and Figure 2 The imaging module 4 includes a display unit 41 and an optical lens group 42, wherein: the display unit 41 is configured to receive and process the emitted light beam modulated by the active electrically tunable metasurface device 2; the optical lens group 42 is used to focus and image the light beam output by the display unit 41 to form a clear and speckle-free projected image on the projection surface.

[0114] In the example of this application, the imaging module 4, through the coordinated operation of the display unit 41 and the optical lens group 42, converts the light beam modulated by the active electrically tunable metasurface device 2 into a clear, speckle-free projected image.

[0115] The display unit 41 receives the spatial phase-modulated beam output from the active electrically tunable metasurface device 2, which has undergone wavefront correction (such as speckle phase compensation or deflection angle control) through the electro-controlled liquid crystal material layer 24. The optical lens group 42 (focusing imaging) is designed, for example, a direct-transmission lens group or a catadioptric lens group, to focus the beam output from the display unit 41.

[0116] The display unit 41 may be a digital micromirror device (DMD) or a liquid crystal display (LCD).

[0117] When the display unit 41 is a liquid crystal display (LCD), a transmissive optical path structure is formed, see [link to relevant documentation]. Figure 1 .

[0118] When the display unit 41 is a digital micromirror device (DMD), a reflective optical path structure is formed, see [link to relevant documentation]. Figure 2 .

[0119] According to another embodiment of this application, a laser speckle suppression method is provided, which includes the following steps: The laser light source module 1 provides an illumination beam and guides it to the actively electrically tunable metasurface device 2; The control module 3 applies a timing control electrical signal to the active electrically tunable metasurface device 2, driving the active electrically tunable metasurface device 2 to perform time-segmented dynamic phase modulation on the incident illumination beam, thereby causing the outgoing beam to deflect at a preset angle. The imaging module 4 receives the deflected outgoing beam and performs imaging. The active electrically tunable metasurface device 2 is controlled by the control module 3 to uniformly superimpose beams with different deflection states within a preset angle range, thereby suppressing laser speckle.

[0120] The laser speckle suppression method provided in this application uses a control module 3 to drive an active electrically tunable metasurface device 2 to achieve time-division dynamic phase modulation of illumination beams of different wavelengths. This causes the emitted beam to deflect at the target angle, and the beams with different deflection states are uniformly superimposed on the projection surface, effectively solving the laser speckle problem and significantly improving the quality of the projected image. Furthermore, the optical method provided in this application requires no mechanical moving parts, offering advantages such as fast response speed, low energy consumption, high system stability, and ease of integration.

[0121] According to another embodiment of this application, an optical display device is provided, the optical display device comprising the laser projection system as described above.

[0122] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0123] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A laser projection system, characterized in that, include: A laser light source module (1) is used to provide an illumination beam; An active electrically tunable metasurface device (2) is disposed in the light output path of the laser light source module (1) for phase modulation of the incident illumination beam; The control module (3) is electrically connected to the active electrically tunable metasurface device (2) and is used to apply a timing control electrical signal to the active electrically tunable metasurface device (2) to drive it to dynamically phase modulate the illumination beams of different wavelengths in a time-division manner, so that the outgoing beams will deflect at the target angle. Imaging module (4) is used to receive the deflected beam and form an image; The control module (3) controls the active electrically tunable metasurface device (2) to make beams with different deflection states uniformly superimposed on the projection surface, thereby suppressing laser speckle.

2. The laser projection system according to claim 1, characterized in that, The active electrically tunable metasurface device (2) comprises the following sequentially stacked components: First transparent substrate (21); A first transparent electrode layer (22) is formed on the first transparent substrate (21); A metasurface structure layer (23) is disposed on the first transparent electrode layer (22) and contains periodically arranged nanostructure units; A liquid crystal material layer (24) is applied over the metasurface structure layer (23); A second transparent electrode layer (25) is formed on the liquid crystal material layer (24); A second transparent substrate (26) covers the second transparent electrode layer (25); The first transparent electrode layer (22) and the second transparent electrode layer (25) are used to receive electrical signals provided by the control module (3) to form an electric field in the liquid crystal material layer (24) and to achieve dynamic modulation of the beam phase by changing the orientation of the liquid crystal molecules in the liquid crystal material layer (24).

3. The laser projection system according to claim 2, characterized in that, The liquid crystal material layer (24) is made of two different refractive indices forming a dual-frequency modulated liquid crystal material, and the refractive index difference Δn between the two different refractive index materials is 0.2 to 0.

3. The control module (3) is configured to control the orientation of liquid crystal molecules in the liquid crystal material layer (24) by switching the frequency of the driving signal, wherein: In low-frequency driving mode, the liquid crystal molecules are aligned parallel to the direction of the electric field; In high-frequency driving mode, the liquid crystal molecules are aligned perpendicular to the direction of the electric field.

4. The laser projection system according to claim 2, characterized in that, The thickness of the first transparent electrode layer (22) and the second transparent electrode layer (25) is 20nm to 100nm, and both are patterned into pixelated electrode arrays; Each electrode unit in the pixelated electrode array can be independently addressed to provide a driving voltage for one or more corresponding nanostructure units; by applying different driving voltages to each electrode unit, local independent control of the phase of the incident illumination beam can be achieved.

5. The laser projection system according to claim 2, characterized in that, The cross-section of the nanoscale structural unit of the metasurface structure layer (23) is rectangular and satisfies the aspect ratio L / W > 1:1, where L is the length of the nanoscale structural unit and W is the width of the nanoscale structural unit.

6. The laser projection system according to claim 5, characterized in that, The aspect ratio L / W of the nanoscale structural unit is 1:1.

8.

7. The laser projection system according to any one of claims 1-6, characterized in that, The overall thickness of the active electrically tunable metasurface device (2) is less than 1 μm.

8. The laser projection system according to claim 1, characterized in that, The control module (3) includes: The calculation unit (31) is used to calculate the phase distribution of the surface of the active electrically tunable metasurface device (2) according to the target deflection angles θ and φ by the following phase modulation function: Φ(x,y)=(2π / λ)(x·sinθ·cosφ+y·sinθ·sinφ), where λ is the wavelength of the incident illumination beam and (x,y) is the coordinate position on the surface of the active electrically tunable metasurface device (2); The driving signal generation unit (32) is used to convert the calculated phase distribution Φ(x,y) into a corresponding voltage control signal to drive each nanostructure unit of the metasurface structure layer (23) to achieve the required spatial phase modulation.

9. The laser projection system according to claim 1, characterized in that, The imaging module (4) includes a display unit (41) and an optical lens group (42), wherein: The display unit (41) is configured to receive and process the emitted light beam modulated by the active electrically tunable metasurface device (2); The optical lens group (42) is used to focus and image the light beam output by the display unit (41) to form a clear and speckle-free projection image on the projection surface.

10. A method for suppressing laser speckle, characterized in that, include: An illumination beam is provided by a laser light source module (1) and directed to an actively electrically tunable metasurface device (2); The control module (3) applies a timing control electrical signal to the active electrically tunable metasurface device (2), driving the active electrically tunable metasurface device (2) to perform time-segmented dynamic phase modulation on the incident illumination beam, thereby causing the outgoing beam to deflect at a preset angle. The imaging module (4) receives the deflected outgoing beam and performs imaging. The active electrically tunable metasurface device (2) is controlled by the control module (3) so that beams with different deflection states are uniformly superimposed within a preset angle range, thereby suppressing laser speckle.

11. An optical display device, characterized in that, Includes the laser projection system according to any one of claims 1-10.

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