Large-angle high-signal-to-noise-ratio multi-working-mode structured light 3D imaging system and light beam emitting chip thereof

Abstract

The invention relates to a large-angle high-signal-to-noise-ratio multi-working-mode structured light 3D imaging system and a light beam emission chip thereof, the system comprises a control and calculation unit, an emission unit and a receiving unit, the emission unit is formed by integrating a photon chip, an integrated switch routing unit, a spot size converter and an inclined grating emission unit on a silicon substrate, laser is dynamically distributed to a plurality of independent sub-arrays through a switch routing unit, and ultra-large field angle light beam scanning without assistance of an external lens is realized by utilizing grating unit arrays with different inclination angles. The system supports three switchable working modes of high frame rate, high signal-to-noise ratio and adaptive staring, and can adjust the projection energy of each sub-array in real time according to the target surface reflectivity, thereby improving the imaging adaptability, reliability and precision in a complex environment and in the face of an object with non-uniform reflection. The problems that a traditional solid-state light beam deflection technology is limited in view field, low in integration level, rigid in mode and poor in environmental adaptability are solved.

Description

[0001] This invention relates to the field of structured light 3D imaging technology, specifically to a large-angle, high signal-to-noise ratio, multi-mode structured light 3D imaging system and its beam emitting chip. Background Technology

[0002] Structured light (SL) illumination, as one of the mainstream methods for 3D scene reconstruction, plays a significant role in various fields, including industrial inspection, facial recognition, and robot navigation. SL-based 3D reconstruction relies on precise spatial alignment between the transmitter and receiver. However, traditional beam steering techniques, such as digital micromirror devices (DMDs) and vertical-cavity surface-emitting laser-optical diffracting elements (VCSEL-DOEs), exhibit inherent limitations when used in highly dynamic or interference-prone outdoor environments. Therefore, these challenges have spurred the development of all-solid-state beam scanning devices with high stability and assembly-friendly manufacturing capabilities. Thanks to the maturity of silicon optoelectronic platforms, solid-state beam scanning devices, such as optical phased arrays (OPAs) and lens-assisted focal plane switch-gated arrays (FPSAs), are attracting increasing attention due to their software-defined scanning patterns and compact form factors, particularly in automotive LiDAR applications.

[0003] The characteristics of pure solid-state beam deflection schemes such as OPA and FPSA have been incorporated into structured light (SL) systems, successfully overcoming many limitations of traditional methods. For example, they achieve active spatiotemporal control of structured light patterns through programmable phase modulation, overcoming fixed projection modes such as static diffractive optical elements (DOES). This dynamic reconstruction capability enables real-time optimization of pattern density and projection angle in complex scenes, a crucial feature for robot navigation in cluttered environments. Secondly, current silicon photonics device design and fabrication primarily focus on wavelengths around 1550 nm, offering significant advantages in terms of eye safety. Furthermore, after years of development, this wavelength can support large-scale, multifunctional, and fully integrated on-chip systems. This integration approach, achieved through co-fabrication with on-chip photodetectors and CMOS logic circuits, provides a unified sensing platform suitable for a variety of advanced applications, from autonomous driving to immersive augmented reality / virtual reality interfaces.

[0004] However, both OPA and FPSA, the two pure solid-state beam deflection schemes, currently have many limitations. Because the grating vector and the incident wave vector are parallel in traditional lens-assisted and optical phased array beam deflection devices, the outgoing wave vector is confined to a single plane. Deflection in the other dimension can only be achieved using lens-assisted deflection or the phased array principle. For lens-assisted devices, the addition of lenses not only increases packaging costs, reduces integration density, and increases size, but also limits the scanning field of view of the beam scanning device. For optical phased array devices, while increasing control complexity, they also introduce degrading factors such as sidelobes and grating lobes. Furthermore, due to the existence of the single-slit diffraction factor, the emission loss increases with a larger deflection angle.

[0005] Therefore, there is an urgent need for a novel beam deflection scheme for structured light to effectively solve the problems of limited scanning field of view, low edge emission efficiency, complex packaging, high control complexity, and large size in traditional schemes.

[0006] This invention addresses the problems of limited scanning field of view, low edge emission efficiency, complex packaging, high control complexity, and large size of traditional OPA or FPSA type solid beam deflection technology in the field of structured light ranging. This invention proposes a structured light 3D imaging scheme with large angle, high signal-to-noise ratio, and multiple working modes. Summary of the Invention

[0007] The purpose of this invention is to provide a large-angle, high signal-to-noise ratio, multi-mode structured light 3D imaging system and its beam emitting chip, whose emitting part can self-image without lens assistance. This solves the problems of limited scanning field of view, low edge emission efficiency, complex packaging, high control complexity, and large size associated with traditional OPA or FPSA type solid-state beam deflection technologies in the field of structured light ranging.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple working modes is characterized by comprising: a control and computing unit, a transmitting unit, and a receiving unit. The output terminal of the control and calculation unit is electrically connected to the control input terminals of the transmitting unit and the receiving unit, respectively, for sending instructions to the transmitting unit to select the working mode and control the energy allocation of the subarray, and to the receiving unit to send synchronous acquisition instructions; at the same time, its data input terminal is connected to the output terminal of the receiving unit, for receiving image data and calculating the three-dimensional information of the target object based on the triangulation method; The emitting unit includes a laser source, a beam emitting chip, and an external power supply. Under the command and control of the control and computing unit, the external power supply provides a driving voltage to the beam emitting chip. The optical output terminal of the laser source is coupled to the optical input terminal of the beam emitting chip through an optical waveguide. The beam emitting chip is a silicon-based on-chip photonic chip, which integrates a switching routing unit, a mode converter, and a grating emitting unit sequentially along the optical path. The input end of the switching routing unit serves as the optical input end of the chip, and its multiple output ends are connected to multiple independent subarrays through on-chip waveguides. Each subarray includes one mode converter and at least one grating emitting unit. The grating emitting unit is composed of a grating with a specific tilt angle, used to directly emit the on-chip guided light upward into free space, forming a structured light field with a predetermined spatial distribution without the need for external lens assistance. The receiving unit includes a lens and a CMOS image sensor. The lens images the reflected light formed by the structured light field modulated by the target object onto the photosensitive surface of the CMOS image sensor.

[0009] Furthermore, the switch routing unit is implemented by a programmable optical switch array based on a Mach-Zehnder interferometer, a micro-ring modulator, or a MEMS architecture, and its switching state is controlled by the voltage provided by the external power supply.

[0010] Furthermore, the mode converter adopts a tapered waveguide structure with a gradually changing cross-sectional size along the optical path direction. Its input end is connected to a narrow waveguide, and its output end is connected to a wider waveguide to match the input requirements of the grating emitting unit.

[0011] Furthermore, in the grating emitting unit, the perturbation tilt angle of the grating is configured to be different for each unit, so that the emitted beam direction of each grating emitting unit covers a viewing angle range of more than 180° in the transverse plane; the period of the grating and the wavelength of the laser source together determine the diffraction angle of the beam in the longitudinal plane.

[0012] Furthermore, the control and computing unit selectively executes at least three operating modes: High frame rate mode: Control the switch routing unit to simultaneously connect the paths of all subarrays, so that multiple grating emission units can work in parallel; High signal-to-noise ratio mode: The control switch routing unit concentrates the energy of the laser source to a single subarray, activating only a few or a single grating emission unit corresponding to that subarray; Adaptive gaze mode: First, control some subarrays to activate for low-density scanning. Then, based on the preliminary scan results, selectively activate one or more specific subarrays for high-density local scanning. At the same time, based on the preliminary scan results, adaptively adjust the energy distribution in multiple subarrays to achieve uniform illumination of objects under different reflectivities.

[0013] Furthermore, in the adaptive staring mode or the regular scanning mode, the control and computing unit can also dynamically adjust the control voltage of the external power supply to different paths in the switching routing unit according to the image brightness information fed back by the receiving unit, thereby adjusting the light energy intensity projected onto different areas of the target object in real time.

[0014] Furthermore, the laser source is a semiconductor laser that generates 1550nm wavelength laser, which is integrated with the beam emitting chip on the same silicon substrate by flip-chip bonding or edge coupling.

[0015] Furthermore, the beam emitting chip is a planar structure without lenses, and there are no discrete optical lens elements above all the grating emitting units. The structured light field is emitted and shaped directly from the chip surface.

[0016] Second, the present invention also provides a beam emitting chip for the aforementioned large-angle, high signal-to-noise ratio, multi-mode structured light 3D imaging system, characterized in that it is a silicon-based photonic integrated circuit, comprising: Public optical input port; The switch routing unit has its input end connected to the common optical input port and has multiple independently controllable output ports for dynamically distributing the input light to multiple sub-array channels. Multiple subarrays, each subarray including a mode converter and a grating emission unit; the input of the mode converter in each subarray is connected to a corresponding output port of the switch routing unit through an on-chip waveguide, and its output is connected to the grating emission unit; the grating emission unit is an irregularly shaped tilted grating with a specific angle between the grating perturbation vector and the light wave vector, used to realize beam emission in different directions.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The system described above can obtain three-dimensional information of objects based on the principle of active detection. 1. Through reasonable subarray design and suitable camera lens matching, the system can achieve a near-hemispherical field of view scanning angle.

[0018] 2. It can be matched with a variety of working modes, such as (1) high frame rate mode: by reasonably selecting the switch state, all subarray switches can be turned on at the same time, and with the help of frequency comb and other technologies, single frame data acquisition can be achieved; (2) outdoor high signal-to-noise ratio mode: the light wave is concentrated in a single subarray, and the energy concentration of the single subarray beam is improved. Although some frame rate is sacrificed, the signal-to-noise ratio can be greatly improved under the same laser intensity in environments with strong noise, such as outdoors; (3) staring mode: first, the contour information is obtained by coarse scanning with low point cloud density, and then important information can be selected by the user or manually to increase the point cloud density scanning. These flexible and varied modes are all thanks to the subarray scheme based on tilted grating.

[0019] 3. High adaptability to different object surfaces: Traditional structured light cameras often encounter situations where the same object has both high-reflectivity and low-reflectivity areas, resulting in overexposure of the high-reflectivity object and poor signal-to-noise ratio of the low-reflectivity object. This system easily achieves brightness adjustment for different parts by using a sub-array emission scheme. For high-reflectivity objects, the corresponding beam intensity is reduced; for low-reflectivity objects, the corresponding beam intensity is increased, thus overcoming this problem and achieving high adaptability to different object surfaces.

[0020] 4. The beam emission chip is a pure on-chip structure without the need for lens assistance. This structure greatly reduces its packaging difficulty and lowers the difficulty and cost of mass production. At the same time, the lensless architecture also increases the reliability of the entire system while reducing the size and weight of the entire system. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is an overall structural diagram of the large-angle, high signal-to-noise ratio, multi-mode structured light 3D imaging scheme provided in the embodiments of the present invention; Figure 2 This is a diagram of the transmitter chip architecture in the transmitter unit provided according to an embodiment of the present invention; Figure 3 This is a diagram of a tilted grating architecture provided according to an embodiment of the present invention; Figure 4 These are simulation images of the far-field light spots of the tilted grating at different tilt angles according to embodiments of the present invention. The reference numerals in the attached figures include: 1, receiving unit; 2, beam emitting chip; 3, laser source; 4, external power supply; 5, control and computing unit; 21, grating emitting unit; 22, mode converter; 23, switch routing unit. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in detail below with reference to the accompanying drawings. It should be noted that the described embodiments are merely preferred embodiments of this invention and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0023] Example This embodiment provides a structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple operating modes. The overall system structure is as follows: Figure 1 As shown, it mainly includes a control and computing unit 5, a transmitting unit, and a receiving unit 1. The transmitting unit further includes a beam emitting chip 2, a laser source 3, and an external power supply 4. This addresses the problems of limited scanning field of view, low edge emission efficiency, complex packaging, high control complexity, and large size associated with traditional OPA or FPSA type solid-state beam deflection technologies in structured light ranging applications.

[0024] The control and calculation unit 5 is used to control the emission chip to regulate laser emission, and at the same time control the camera to take pictures. Then, it calculates the three-dimensional information of the object according to the triangulation method.

[0025] The receiving unit 1 consists of a CMOS camera and a lens. The lens images the light reflected from the target onto the CMOS camera chip to obtain the corresponding pattern.

[0026] The emitting unit mainly consists of three parts: a beam emitting chip 2, an external power supply 4, and a laser source 3. The laser source is used to generate lasers of different wavelengths. It can be integrated with the beam emitting chip on the same chip or a separate external laser can be used. The external power supply is used to control the subarray selection of the beam emitting chip. The beam emitting chip reshapes the input laser and emits it onto the target object.

[0027] The detailed architecture of beam emitting chip 2 is as follows: Figure 2 As shown. This chip is fabricated on an 8-inch silicon wafer using a standard 220nm silicon-on-insulator (SOI) process. Its core functional layer consists of three layers: The switching routing unit 23 is used to route the laser to different subarrays. There are no restrictions on the switching scheme. It can be based on Mach-Zehnder interferometer architecture, micro-ring modulator architecture, MEMS architecture, etc. There are also no restrictions on the switching modulation method, such as electro-optic modulation using plasma dispersion effect, thermo-optic modulation using thermo-optic effect, etc.

[0028] The mode converter 22 is located at the entrance of each subarray channel. It is used to amplify the fundamental mode spot confined in the narrow waveguide to match the required mode size of the grating. Mode conversion can be achieved by means of a tapered structure based on mode gradient, a lens scheme using an on-chip lens system, or mode conversion using evanescent waves.

[0029] The grating emitting unit 21 is used to emit on-chip laser light into a target object in a certain shape, such as... Figure 3 The design shown comprises three parts: the grating width and length—which determine the divergence angle of the emitted beam, i.e., the energy concentration; the grating perturbation spacing—which, together with the incident wavelength, determines the far-field longitudinal diffraction angle; and the grating perturbation tilt angle—which determines the transverse diffraction angle of the incident wavelength, such as... Figure 4 As shown, by changing the tilt angle of the grating perturbation, a field of view scanning within a 180° range can be achieved.

[0030] The workflow of this embodiment is as follows: 1. Signal light of a specific wavelength and intensity is emitted from the light source.

[0031] 2. The control unit controls the power supply to change the routing status of the optical switch group, routing the signal light to different paths.

[0032] 3. After the signal light is routed to the corresponding path, it undergoes mode conversion via a mode converter. The core of this conversion is mode amplification, which is used to match the grating.

[0033] 4. The signal light is emitted to different positions in space through gratings with different spacing and tilt angles. The specific principle is as follows:

[0034] like Figure 4 As shown, where The wave vector corresponding to the incident light wave; Let be the wave vector corresponding to the outgoing light wave; and be the wave vector corresponding to the grating. Because momentum is conserved, the magnitudes of the wave vectors of the incident and outgoing light waves should remain constant. Based on this formula, the far-field diffraction angles for different grating shapes at a fixed wavelength can be derived.

[0035] 5. The light emitted by this beamforming chip will spread out in a cone shape, which can be characterized by the formula, where f is the focal length of the camera, [x', y'] are the pixel coordinates of the center line, [x0, y0, z0] are the vertices of the cone, [a x , a y ,a z ] is the axis vector of the cone, and θ is the half angle of the cone. These unknown parameters can be obtained by fitting a calibration image onto the target surface of the flat plate. The shape formula of the beam emitted by this system can then be obtained.

[0036]

[0037] 6. When a specially shaped light wave emitted by the chip strikes an object containing depth information, it deforms. This deformed light wave signal is captured by an infrared camera. Using triangulation, the specific depth information can be calculated based on the deformation.

[0038] This embodiment addresses the problems of limited scanning field of view, low edge emission efficiency, complex packaging, high control complexity, and large size associated with traditional OPA or FPSA solid-state beam deflection technologies in structured light ranging applications. This embodiment uses a tilted grating array as the core emitting element. By designing grating perturbations with different tilt angles, the wave vector direction of the emitted beam can be freely adjusted in a two-dimensional plane, achieving ultra-wide field of view (near hemispherical) beam projection on-chip without any moving parts or external lens assistance. This fundamentally solves the problems of limited field of view and complex structure associated with traditional OPA or lens-assisted solutions. Furthermore, based on a subarray-based dynamic multi-mode operating mechanism—dividing the emitting chip into multiple independently controllable "subarrays" through a switching routing section—this invention endows the system with unprecedented flexibility in operating modes, specifically manifested in: High frame rate mode: By controlling the switch to activate all subarrays simultaneously (or combining with optical frequency comb technology), parallel projection and acquisition of multi-point clouds within a single frame can be achieved, improving the frame rate and data acquisition speed of 3D imaging.

[0039] High signal-to-noise ratio mode: Under strong ambient light or noise interference (such as outdoor scenes), all laser energy can be concentrated and routed to a single or a small number of subarrays for projection. This increases the energy density of the light spot projected to the local area, thereby significantly improving the signal strength and system signal-to-noise ratio with the same total laser power.

[0040] Adaptive staring scan mode: First, a rapid coarse scan is performed with low point cloud density (activating fewer subarrays) to obtain the general outline of the scene; then, based on a preset algorithm or manual command, it automatically switches to a high-density (activating more subarrays) fine scan for the region of interest. This "global first, local later" intelligent scanning strategy balances efficiency and accuracy.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the principle of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple working modes, characterized in that, include: Control and computing unit (5), transmitting unit and receiving unit (1); The output terminal of the control and calculation unit (5) is electrically connected to the control input terminal of the transmitting unit and the receiving unit (1), respectively, and is used to send the transmitting unit a command for selecting the working mode and controlling the energy allocation of the subarray, and to send the receiving unit (1) a synchronous acquisition command; at the same time, its data input terminal is connected to the output terminal of the receiving unit (1), and is used to receive image data and calculate the three-dimensional information of the target object based on the triangulation method; The emitting unit includes a laser source (3), a beam emitting chip (2), and an external power supply (4). The external power supply (4) provides a driving voltage to the beam emitting chip (2) under the command control of the control and computing unit (5). The optical output end of the laser source (3) is coupled to the optical input end of the beam emitting chip (2) through an optical waveguide. The beam emitting chip (2) is a silicon-based on-chip photonic chip, which has a switch routing unit (23), a mode converter (22) and a grating emitting unit (21) sequentially integrated along the optical path inside. The input end of the switch routing unit (23) serves as the optical input end of the chip, and its multiple output ends are connected to multiple independent subarrays through on-chip waveguides. Each subarray contains one mode converter (22) and at least one grating emitting unit (21). The grating emitting unit (21) is composed of a grating with a specific tilt angle, which is used to directly emit the on-chip guided light upward into free space to form a structured light field with a predetermined spatial distribution that does not require external lens assistance. The receiving unit (1) includes a lens and a CMOS image sensor. The lens images the reflected light formed by the structured light field after being modulated by the target object onto the photosensitive surface of the CMOS image sensor.

2. The structured light 3D imaging system with large angle, high signal-to-noise ratio, and multiple working modes according to claim 1, characterized in that: The switch routing unit (23) is implemented by a programmable optical switch array based on a Mach-Zehnder interferometer, a micro-ring modulator or a MEMS architecture, and its switching state is controlled by the voltage provided by the external power supply (4).

3. The structured light 3D imaging system with large angle, high signal-to-noise ratio, and multiple working modes according to claim 1, characterized in that: The mode converter (22) adopts a tapered waveguide structure with a gradually changing cross-sectional size along the optical path direction. Its input end is connected to a narrow waveguide, and its output end is connected to a wider waveguide to match the input requirements of the grating emitting unit (21).

4. The structured light 3D imaging system with large angle, high signal-to-noise ratio, and multiple working modes according to claim 1, characterized in that: In the grating emitting unit (21), the perturbation tilt angle of the grating is configured to be different for each grating, so that the direction of the emitted beam of each grating emitting unit (21) covers a viewing angle range of more than 180° on the transverse plane; the period of the grating and the wavelength of the laser source (3) together determine the diffraction angle of the beam on the longitudinal plane.

5. A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple operating modes according to claim 1, characterized in that: The control and computing unit (5) selectively executes at least three operating modes: High frame rate mode: Control the switch routing unit (23) to simultaneously open the paths of all subarrays, so that multiple grating emission units (21) can work in parallel; High signal-to-noise ratio mode: The switch routing unit (23) is controlled to concentrate the energy of the laser source (3) to a single subarray, and only a few or a single grating emission unit (21) corresponding to the subarray is activated. Adaptive gaze mode: First, control some subarrays to activate for low-density scanning. Then, based on the preliminary scan results, selectively activate one or more specific subarrays for high-density local scanning. At the same time, based on the preliminary scan results, adaptively adjust the energy distribution in multiple subarrays to achieve uniform illumination of objects under different reflectivities.

6. A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple operating modes according to claim 5, characterized in that: In the adaptive gaze mode or the regular scanning mode, the control and calculation unit (5) can also dynamically adjust the control voltage of the external power supply (4) on different paths in the switch routing unit (23) according to the image brightness information fed back by the receiving unit (1), thereby adjusting the light energy intensity projected onto different areas of the target object in real time.

7. A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple working modes according to claim 1, characterized in that: The laser source (3) is a semiconductor laser that generates 1550nm wavelength laser, which is integrated with the beam emitting chip (2) on the same silicon substrate by flip-chip bonding or edge coupling.

8. A structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple operating modes according to claim 1, characterized in that: The beam emitting chip (2) is a planar structure without lenses. There are no discrete optical lens elements above all the grating emitting units (21). The structured light field is emitted and shaped directly from the chip surface.

9. A beam emitting chip (2) applied to a structured light 3D imaging system with a large angle, high signal-to-noise ratio, and multiple operating modes as described in any one of claims 1-8, characterized in that, It is a silicon-based photonic integrated circuit, including: Public optical input port; The switch routing unit (23) has its input end connected to the common optical input port and has multiple independently controllable output ports for dynamically distributing the input light to multiple sub-array channels. Multiple subarrays, each subarray including a mode converter (22) and a grating emission unit (21); the input end of the mode converter (22) in each subarray is connected to a corresponding output port of the switch routing unit (23) through an on-chip waveguide, and its output end is connected to the grating emission unit (21); the grating emission unit (21) is an irregularly shaped tilted grating with a specific angle between the grating perturbation vector and the light wave vector, used to realize beam emission in different directions.

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