Light projection device, depth camera, detection device and dual-light-path projection implementation method

Abstract

The invention provides a light projection device, a depth camera, a detection device and a dual-light-path projection implementation method. The dual-wavelength light source projection device comprises a light source capable of emitting dual-wavelength light beams, an optical waveguide internally provided with a plurality of gratings and light beam shaping elements corresponding to the light beams with different wavelengths respectively. A light beam emitted by a light source is transmitted to an optical waveguide, the propagation direction of a dual-wavelength light beam is adjusted through a plurality of gratings arranged in the optical waveguide or light beams with different wavelengths are split, and a split light beam with a single wavelength output by the optical waveguide is obtained; each sub-beam is shaped by a beam shaping element and then is projected to obtain a projection pattern. The projection device provided by the invention can realize shaping and projection of two patterns with different wavelengths in the same light source and light beams in different directions, realizes detection of two light paths without mutual interference, is applied to the field of safety cameras, and is high in integration, low in cost, low in energy consumption, easy to manufacture, high in safety performance and suitable for popularization and application. And convenience is provided for dual-optical-path detection.

Description

Technical Field

[0001] The present invention relates to the field of light detection technology, and in particular to a light projection device, a depth camera, a detection device, and a method for implementing dual-light path projection. Background Art

[0002] A dual-wavelength light source projection device is a device that can project two different wavelengths of light simultaneously or separately. It is widely used in multiple technical fields, such as optical measurement, spectral analysis, biomedicine, display technology, etc.

[0003] Dual-light-path projection devices, used in binocular stereo cameras or 3D cameras, project texture patterns onto the scene being measured from different directions, using the two beams of light to capture surface information. However, in existing technologies, obtaining accurate projected images and detection information requires the use of two optical paths and additional optical components. This increased integration reduces the overall projection device's integration and increases its size, hindering the camera's portability and installation flexibility.

[0004] Therefore, the prior art needs to be further improved. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a light projection device, a depth camera, a detection device and a dual-light path projection implementation method to solve the defect of low integration of the light source projection device in the prior art.

[0006] In a first aspect, the present invention discloses a light projection device, comprising: a light source, an optical waveguide with multiple built-in gratings, and a beam shaping element corresponding to light beams of different wavelengths;

[0007] The light source is used to emit a light beam; wherein the light source is a broad spectrum light source and covers at least two wavelength bands;

[0008] The optical waveguide is arranged on the optical path of the light source, and is used to receive the light beam emitted by the light source, and use the built-in multiple gratings to adjust the propagation direction of the light beam or split the light beams of different wavelengths to output a split light beam of a single wavelength;

[0009] The beam shaping elements are respectively located on the transmission optical paths of light beams of different wavelengths, and shape the received sub-beams and then project them to obtain a projection pattern.

[0010] Optionally, the grating in the optical waveguide includes an in-coupling grating and an out-coupling grating; the number of the out-coupling gratings is at least two;

[0011] The coupling-in grating splits the input light beam into at least two sub-beams, each sub-beam is transmitted in the optical waveguide to the coupling-out grating, and is coupled out of the optical waveguide after the transmission direction is adjusted by the coupling-out grating.

[0012] Optionally, the coupling-in grating and each of the coupling-out gratings are one or more of a diffraction grating, a metasurface or a holographic grating.

[0013] Optionally, the beam shaping element is a diffractive optical element, a metasurface, a microlens array or a MEMS micro-vibration mirror.

[0014] Optionally, the number of the beam shaping elements is two, and the projection patterns output by the beam shaping elements are speckles or stripes.

[0015] Optionally, a collimating element is further provided between the light source and the optical waveguide;

[0016] The collimating element is used to receive the light beam emitted by the light source, collimate the light beam, and then input it into the optical waveguide.

[0017] Optionally, the light projection device is applied to a TOF camera or a structured light camera, and the wavelength range corresponding to the light beam output by the light source is 790nm-1400nm.

[0018] In a second aspect, the present invention discloses a depth camera, which includes the light projection device.

[0019] In a third aspect, the present invention provides a light detection device, comprising the light projection device and a wavelength detector arranged on the optical path of the light beam emitted by the light projection device;

[0020] The wavelength detector is used to receive the light beam emitted by the light projection device and convert the light signal into an electrical signal to obtain a wavelength detection result.

[0021] In a fourth aspect, the present invention provides a method for implementing dual-light path projection, which includes:

[0022] A light beam emitted from a light source is input into the optical waveguide;

[0023] The light beam input into the optical waveguide is adjusted in propagation direction or split by the grating inside the optical waveguide, and then split into beams of single wavelength and output to the beam shaping element;

[0024] The beam shaping element shapes the received split beams and then projects them to obtain a dual-light-path projection pattern.

[0025] Beneficial effects:

[0026] The present invention provides a light projection device, a depth camera, a detection device, and a method for implementing dual-light path projection. The light projection device includes: a light source, an optical waveguide with multiple built-in gratings, and a beam shaping element corresponding to light beams of different wavelengths. The light beam emitted by the light source is transmitted to the optical waveguide, and the multiple built-in gratings in the optical waveguide adjust the propagation direction of the dual-wavelength light beam or split the light beams of different wavelengths to obtain a single wavelength split light beam output by the optical waveguide. Each split light beam is shaped by the beam shaping element and then projected to obtain a projection pattern. The projection device provided by the present invention can realize two different wavelength patterns from the same light source, as well as beam shaping and projection in different directions, enabling detection of two light paths without mutual interference. It is used in the field of security cameras. The present invention can achieve high integration, low cost, low energy consumption, easy manufacturing, and high safety performance, providing convenience for dual-light path detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the light projection device provided by the present invention;

[0028] Figure 2 This is a schematic diagram of the principle of the light projection device of the present invention in a specific application;

[0029] Figure 3 Schematic diagram of the propagation direction of the projected light in the light projection device provided by the present invention;

[0030] Figure 4 is a schematic diagram of a projection image projected by the light projection device provided by the present invention;

[0031] Figure 5 is a schematic diagram of the beam shaping structure provided by the present invention;

[0032] Figure 6 It is a flow chart of the steps of the dual-light-path projection implementation method provided by the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear and distinct, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0034] Dual-beam detection is an optical detection technology based on the principle of dual-beam interference. It primarily detects changes in physical quantities such as displacement, pressure, temperature, or concentration by measuring parameters such as the phase difference or intensity ratio between two beams of light.

[0035] A dual-path detection system typically consists of a light source, two optical paths, and a detector. Dual-path detection technology can precisely measure minute changes in physical quantities with high accuracy. It is widely used in various fields, such as scientific research, industrial testing, environmental monitoring, and biomedicine.

[0036] Existing depth camera laser projection devices involve two optical paths, requiring the design of two independent light transmission paths. This requires more optical components, increasing the system's size and weight and increasing the complexity of integration. Furthermore, the two independent light transmission paths must be able to accurately project onto objects and form limited interference or imaging effects, requiring precise alignment and calibration of the two light paths, further complicating system integration.

[0037] To overcome the above-mentioned drawbacks, this embodiment provides a light projection device, a depth camera, a detection device, and a dual-light path projection implementation method. The light projection device is provided with a wide-spectrum light source, an optical waveguide, and a beam shaping element. The optical waveguide is used to split the light of different wavelengths in the wide-spectrum light source into at least two beams. The beam shaping element is then used to shape the split beams coupled out of the optical waveguide before projection, thereby obtaining at least two projected images, achieving highly integrated and low-energy dual-light path projection. The light projection device provided by the present invention can be applied to a depth camera to enable the same light source to project light beams of different patterns and directions, thereby providing a highly integrated and highly secure dual-light path projection device and dual-light path detection device.

[0038] An example requirement (security camera certification): In the field of security detection, in order to improve the reliability of the system, it is necessary to use the same sensor for multi-path measurement, and the individual measurements do not interfere with each other, to ensure that the system is safe and reliable under the condition that one path is available. The wavelengths of the detection light sources commonly used by TOF detectors are 850nm and 940nm. By integrating two wavelength detection sensors with the same sensor to monitor the same area, dual-path detection can be achieved. High integration and volume control are important considerations for sensors. The light projection device, depth camera and detection device provided in this embodiment can achieve dual-path detection, which is a necessary condition for passing a certain level of security camera (TOF or structured light) certification.

[0039] The following is a further and more detailed description of a light projection device, a depth camera, a detection device and a dual-light path projection implementation method provided by this embodiment in conjunction with the accompanying drawings.

[0040] The present invention discloses a light projection device, such as Figure 1As shown, the optical waveguide 200 includes a light source 100, an optical waveguide with multiple built-in gratings, and beam shaping elements corresponding to light beams of different wavelengths (including a first beam shaping element 310 and a second beam shaping element 320). The first beam shaping element and the second beam shaping element correspond to different optical paths, and the shaped output patterns can be the same or different.

[0041] The light source 100 is configured to emit a light beam; the light source 100 is a broad-spectrum light source covering at least two wavelength bands. Because the light source has a broad spectrum, the wavelengths of the emitted light can range from several hundred to several thousand wavelengths. Therefore, by refracting the light beam, multiple split beams of different wavelengths can be generated. Furthermore, the dual-wavelength light source projection device is used in a TOF camera or a structured light camera, with the dual-wavelength light beams output by the light source corresponding to wavelengths of 790 nm to 1400 nm.

[0042] The optical waveguide 200 is arranged on the optical path of the light source 100, and is used to receive the light beam emitted by the light source 100, and use the built-in multiple gratings to adjust the propagation direction of the light beam or split the light beams of different wavelengths to output a split light beam of a single wavelength.

[0043] An optical waveguide is a dielectric device that guides the propagation of light waves. It utilizes the principle that light is fully reflected at the interface between two materials with different refractive indices, restricting the transmission of light waves to a micrometer-scale range. The optical waveguide used in this embodiment is a grating waveguide, which utilizes the diffraction properties of the grating and the total internal reflection properties of the waveguide medium to achieve the transmission and expansion of the imaging beam. Because grating waveguide technology can eliminate the heavy structure of the optical system and achieve near-eye display of images with ultra-thin lenses and ultra-large screens, it has the advantages of being light, transparent, having a large field of view, and high light transmittance.

[0044] A grating periodically modulates the phase or amplitude of an incident light wave, causing diffraction and interference during propagation. This decomposes the complex light into monochromatic light, forming a spectrum. A grating is typically composed of a large number of parallel slits of equal width and spacing. These slits diffract the incident light, amplifying or weakening different wavelengths at specific angles, achieving spectroscopic separation.

[0045] The grating here can be a surface-embossed diffraction grating used in AR glasses, or a metasurface or holographic grating. In a specific implementation, a diffraction grating is embossed on the inner surface of the optical waveguide, or a metasurface grating is set on the optical waveguide, and the embossed diffraction grating or metasurface grating serves as the coupling-in grating and coupling-out grating of the optical waveguide.

[0046] The beam shaping elements 300 are respectively located on the transmission optical paths of light beams of different wavelengths, and shape the received split light beams before projection to obtain projection patterns.

[0047] The light source used in the light projection device provided by the present invention is a broad-spectrum light source, capable of emitting light in multiple wavelength bands. After the light is directed by an optical waveguide, it is split into at least two beams and then transmitted outward. The split beams output from the waveguide are then shaped by a beam shaping element to form at least two projection patterns.

[0048] In specific implementation, the light projection device provided by this embodiment can be applied to multiple fields to provide dual-light-path projection patterns. For example: applied to industrial inspection and measurement, precise measurement and quality inspection are performed by two paths of light emitted from the same light source. Applied to medical imaging equipment, it is used for high-resolution imaging of biological tissues. Applied to 3D projectors, 3D projection images are achieved by projecting two optical beams at different angles. It can also be applied to optical experimental devices to demonstrate phenomena such as interference and diffraction of light. When applied to TOF and structured light, the light output by the light source needs to be in the near-infrared band. The wavelength range is 790nm-1400nm. In specific implementation, in order to output two different wavelength light beams, a wide-spectrum light source consisting of two light sources with wavelengths of 850nm and 950nm can be used.

[0049] Further, combined with Figure 1 As shown, the gratings within the optical waveguide include an incoupling grating 210 and an outcoupling grating 220; there are at least two outcoupling gratings 220. Light input into the optical waveguide passes through the incoupling grating 210 and enters the optical waveguide. After undergoing total internal reflection within the optical waveguide, it is transmitted to the outcoupling grating. The optical signal is then coupled out of the optical waveguide via the outcoupling grating.

[0050] Specifically, the coupling-in grating splits the input light beam into at least two sub-beams, each of which is transmitted in the optical waveguide to the coupling-out grating and coupled out of the optical waveguide via the coupling-out grating.

[0051] In a specific implementation, the coupling-in grating and each of the coupling-out gratings are one or more of a diffraction grating, a metasurface, or a holographic grating. The beam shaping element is a diffractive optical element, a metasurface, a microlens array, or a MEMS micro-vibrator. Diffractive optical elements offer high precision and flexibility, can combine multiple functions on a single surface, and have very low thermal sensitivity, making them suitable for shaping narrow lines and speckle patterns. Furthermore, diffractive optical elements have high transmittance and transmission efficiency, which can improve the clarity and precision of optical imaging. Metasurfaces offer the advantages of miniaturization and integration, enabling even greater miniaturization and integration while achieving the corresponding functions of diffractive optical elements, while also enabling efficient light modulation. A microlens array is composed of a meticulously arranged array of microlenses with micron-level apertures and relief depths. Parameters such as shape, focal length, arrangement, and duty cycle can be flexibly adjusted to achieve diverse optical functions, enabling widespread application in beam shaping applications such as floodlighting. By flexibly adjusting the various parameters of the lens units, the position and effect of light focus can be precisely controlled, improving the overall performance and integration of the optical system. MEMS micro-vibration mirrors, on the other hand, are small in size and simple in structure, making them suitable for use in miniaturized and highly integrated devices. They also offer advantages such as high reliability and low power consumption. Each of the aforementioned beam shaping components has its own unique characteristics, and selection should be based on comprehensive considerations of the specific application scenario and requirements. For example, in speckle projection applications requiring high precision and flexibility, DOEs and metasurfaces are good choices; measurement systems for flood projection require the use of microlens arrays, while MEMS micro-vibration mirrors offer advantages in scanning devices pursuing miniaturization and integration.

[0052] Furthermore, the number of the beam shaping elements is two, and the projection patterns output by the beam shaping elements are speckles or stripes.

[0053] In order to obtain a better light projection effect, a collimating element is further provided between the light source and the optical waveguide; the light beam outputted by the light source is collimated by the collimating element and then outputted to the optical waveguide.

[0054] The collimating element is used to receive the light beam emitted by the light source, collimate the light beam, and then input it into the optical waveguide. The collimating element can be a fiber collimator, a collimating lens (a single lens or a lens array composed of multiple lenses), or a microlens array collimator. After being collimated by the collimating element, the scattered light beam is converted into a parallel light beam, which is incident on the optical waveguide in parallel.

[0055] The number of light beams coupled out of the optical waveguide can be multiple based on the wavelength. Figure 1 As shown, there are two corresponding split beams, and the two split beams are respectively input into corresponding beam shapers, and after beam shaping by the corresponding beam shapers, are projected into the same or different patterns.

[0056] Combine Figure 2 As shown, when the light projection device provided by this embodiment is applied in industry, the light projection device provided by this embodiment can be installed at the front end of a robot. The light beam emitted by the control light source is sequentially shaped through a collimating element, an optical waveguide, and a beam shaper to obtain two projection patterns with different wavelengths. The information of the projection image is then detected by the first detector 500 and the second detector 600, respectively, to obtain corresponding detection information.

[0057] Combine Figure 3 As shown in the figure, when the coupling grating in the optical waveguide controls the propagation direction of the projected light, it modulates the phase or amplitude of the light wave based on its spatial periodic structure, thereby adjusting the propagation direction of the light. If the incident light beam is a single-wavelength beam, its transmission direction is changed by diffraction. If the incident light beam is a dual-wavelength beam, grating splitting can be achieved, that is, the propagation of the dual wavelengths in different directions can be achieved.

[0058] Further, such as Figure 4 As shown, after being shaped by the beam shaping element, the projected pattern can be speckle or stripes. The patterns projected by the two beams can be the same or different. Because the projected pattern is obtained through interference and diffraction, the resulting speckle is a uniformly distributed light spot. The resulting stripes are a periodically arranged pattern of alternating dark and dark stripes or bands.

[0059] Because the two patterns projected by the light projection device provided in this embodiment are speckle or fringe patterns, speckle or fringe patterns can encode spatial information through variations in width, spacing, or angle, facilitating high-precision decoding. This improves measurement accuracy and resolution. In industrial inspection applications, fringe patterns can be used to detect part edge defects or dimensional deviations. Furthermore, speckle patterns cover a wider field of view, making them suitable for large-area measurements. Therefore, the light projection device provided in this embodiment has high detection accuracy and resolution, meeting the requirements for high-precision and high-resolution detection scenarios.

[0060] Furthermore, the light source disclosed in this embodiment is a dual-wavelength active light source that can output light of two different wavelengths simultaneously or alternately. The light source can be an electroluminescent LED or laser diode, or a chemiluminescent fluorescent stick or cold light film.

[0061] Furthermore, the optical path control of grating spectrometry can be calculated using the grating equation. The basic form of the grating equation is:

[0062] d(sinθ m + sinθi)=mλ;

[0063] Where d is the grating constant, the distance between two adjacent notches. iis the angle of incidence, i.e. the angle between the incident light and the normal to the grating plane, θ m is the diffraction angle of the mth order diffracted light, that is, the angle between the diffracted light and the normal to the grating plane, m is the diffraction order, and its value is 0, ±1, ±2, .... λ is the wavelength of the incident light.

[0064] Down Figure 5 This is a relief grating control method: efficiency can be controlled by the surface microstructure of the diffraction grating, where W is the width of a relief structure, P is the length of the periodic structure, c is the tilt angle of the relief structure, and H is the height of the relief structure. In one embodiment, a grating and substrate with a refractive index of 1.8 are surrounded by air and have a fixed period of 393 nm.

[0065] The light projection device provided by the present invention is further described below by taking the application of the light projection device provided by this embodiment to a structured light camera and realizing the projection of a dual-light path pattern as an example.

[0066] The light projection device of this embodiment is applied to the transmitting end of the structured light camera, which provides basic data for subsequent three-dimensional reconstruction and depth measurement by projecting striped or speckled laser light on the target object.

[0067] Specifically, the light source of the light projection device is a laser that emits a wide spectrum and can achieve two different patterns of wavelengths and beam shaping and projection in different directions. In this embodiment, the light source can achieve patterns corresponding to two wavelengths of 940nm and 850nm.

[0068] A collimating element is provided on the emission light path of the light source, and the laser emitted by the light source is collimated into a parallel light beam by the collimating element. The collimating element is a collimating lens.

[0069] The collimated light beam is incident on the optical waveguide, and the grating in the optical waveguide is used to split the light, thereby obtaining multiple sub-beams. In this embodiment, two sub-beams corresponding to 940nm and 850nm can be obtained respectively.

[0070] Finally, a beam shaping element is used to receive the light beam output from the optical waveguide and convert it into a stripe or speckle structure.

[0071] The light projection device provided in this embodiment uses a grating to control the propagation of light of different wavelengths within a waveguide, enabling the same light source (with a relatively wide spectrum) to shape and project two wavelengths (e.g., 940nm and 850nm) in different patterns and directions. Combined with two wavelength detectors, this device achieves interference-resistant detection and improves safety. Speckle patterns can be used for TOF or structured light detection, while stripes can be used for structured light detection.

[0072] In a second aspect, the present invention discloses a depth camera, which includes the light projection device.

[0073] The depth camera can be a structured light camera or a TOF camera. Since the structured light camera or TOF camera is provided with the light projection device provided in this embodiment, the depth camera has the function of projecting two light beams and can realize the shaping of the projected light speed on the two light paths, so that dual-light path detection in the scene can be performed simultaneously.

[0074] In a third aspect, the present invention provides a light detection device, comprising the light projection device and a wavelength detector arranged on the optical path of the light beam emitted by the light projection device;

[0075] The wavelength detector is used to receive the light beam emitted by the light projection device and convert the light signal into an electrical signal to obtain a wavelength detection result.

[0076] By arranging two detectors on both sides of the light projection device, a detector capable of realizing dual-light path detection is obtained.

[0077] In one implementation, when in use, the light projection device emits a laser beam, and the wavelength detector receives the laser beam reflected by the target and measures its round-trip time or phase change, thereby calculating the distance to the target.

[0078] In a fourth aspect, the present invention provides a method for realizing dual-light path projection, such as Figure 6 Shown, including:

[0079] Step S1: A light beam emitted from a light source is input into an optical waveguide.

[0080] When a dual-light-path projection pattern is required, the light beam emitted by the light source must first be diffracted or interfered with by a grating and then split into two beams. Therefore, the light source used here is a wide-spectrum light source. The light beam emitted by this light source can be split into two beams.

[0081] Step S2: The light beam input into the optical waveguide is adjusted in propagation direction or split by the grating inside the optical waveguide, and then split into beams of single wavelength and output to the beam shaping element.

[0082] The light beam emitted by the light source is split by the grating in the optical waveguide and then divided into two sub-beams, which are then input into corresponding beam shaping elements. In a specific implementation, the beam shaping element is a DOE.

[0083] Step S3: The beam shaping element shapes the received split beams and then projects them to obtain a dual-light-path projection pattern.

[0084] The beam shaping element shapes the received split beams to project a spot or fringe pattern. The resulting speckle pattern can be used for TOF or structured light detection, while the resulting fringe pattern can be used for structured light detection. Specifically, the beam shaping element can be a lens, prism, grating, spatial light modulator, or microlens array. In this embodiment, to achieve better dual-path projection patterns, the beam shaping element uses a microlens array to achieve fine division and redistribution of the light beam, thereby producing a more uniform and higher-quality speckle or fringe pattern.

[0085] The dual-path projection method provided by this invention can simultaneously perform dual-path projection and detection in a scene. The projected beams can form patterns such as speckles and stripes. Using a single broad-wavelength laser light source, optical waveguide, and grating, this method achieves highly integrated, low-energy, and highly secure dual-path detection with strong anti-interference performance, low cost, and ease of implementation.

[0086] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0087] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0088] It is understandable that the above embodiments are exemplary and should not be construed as limiting the present application. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A light projection device, characterized in that include: A light source, an optical waveguide with multiple built-in gratings, and beam shaping elements corresponding to light beams of different wavelengths; The light source is used to emit a light beam; wherein the light source is a broad spectrum light source and covers at least two wavelength bands; The optical waveguide is arranged on the optical path of the light source, and is used to receive the light beam emitted by the light source, and use the built-in multiple gratings to adjust the propagation direction of the light beam or split the light beams of different wavelengths to output a split light beam of a single wavelength; The beam shaping elements are respectively located on the transmission optical paths of light beams of different wavelengths, and shape the received sub-beams and then project them to obtain a projection pattern.

2. The light projection device according to claim 1, wherein The grating in the optical waveguide includes an in-coupling grating and an out-coupling grating; the number of the out-coupling gratings is at least two; The coupling-in grating splits the input dual-wavelength light beam into at least two sub-beams, each sub-beam is transmitted in the optical waveguide to the coupling-out grating, and is coupled out of the optical waveguide after the transmission direction is adjusted by the coupling-out grating.

3. The light projection device according to claim 2, wherein: The coupling-in grating and each of the coupling-out gratings are one or more of a diffraction grating, a metasurface or a holographic grating.

4. The light projection device according to claim 2, wherein The beam shaping element is a diffractive optical element, a metasurface, a microlens array or a MEMS micro-vibration mirror.

5. The light projection device according to claim 1, wherein The number of the beam shaping elements is two, and the projection patterns output by the beam shaping elements are speckles or stripes.

6. The light projection device according to claim 1, wherein A collimating element is further provided between the light source and the optical waveguide; The collimating element is used to receive the light beam emitted by the light source, collimate the light beam, and then input it into the optical waveguide.

7. The light projection device according to claim 1, wherein The light projection device is applied to a TOF camera or a structured light camera, and the wavelength range corresponding to the light beam output by the light source is 790nm-1400nm.

8. A depth camera, characterized in that The device comprises a light projection device as described in any one of claims 1 to 7.

9. A light detection device, characterized in that: comprising a light projection device according to any one of claims 1 to 7 and a wavelength detector arranged on an optical path of a light beam emitted by the light projection device; The wavelength detector is used to receive the light beam emitted by the light projection device and convert the light signal into an electrical signal to obtain a wavelength detection result.

10. A method for realizing dual-light path projection, characterized in that: include: A light beam emitted from a light source is input into the optical waveguide; The light beam input into the optical waveguide is adjusted in propagation direction or split by the grating inside the optical waveguide, and then split into beams of single wavelength and output to the beam shaping element; The beam shaping element shapes the received split beams and then projects them to obtain a dual-light-path projection pattern.

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