Structured light projectors and 3D scanning equipment

Abstract

This invention provides a structured light projector and a 3D scanning device. The structured light projector includes a light source, a first lens, a second lens, and a diffractive optical element. The light source emits a light beam. The first lens focuses the light beam emitted by the light source into a spot. The second lens shapes the spot into a linear spot. The diffractive optical element diffracts the linear spot into multiple parallel linear spots, so that the structured light projected by the structured light projector presents a linear pattern. The structured light projector provided in this application first focuses the light beam emitted by the light source into a small-sized dot-shaped spot, and then shapes it into a linear spot. Therefore, the diameter of the lines in the final projected linear pattern can be very small, thus meeting the needs of some high-precision scenarios.

Description

Technical Field

[0001] This utility model relates to the field of three-dimensional scanning technology, and in particular to a structured light projector and a three-dimensional scanning device. Background Technology

[0002] A structured light projector is an optical device used to project light in a specific pattern (such as lines, grids, or dot matrix) onto the surface of a target object. It is widely used in 3D scanning, robot vision, industrial inspection, and other fields. In some scenarios, it is necessary to use a structured light projector to project line patterns onto the surface of a target object. However, the lines projected by current structured light projectors are often relatively thick, meaning the diameter of the lines is relatively large, which cannot meet the needs of some high-precision or fine measurement scenarios. Utility Model Content

[0003] This invention provides a structured light projector and a three-dimensional scanning device.

[0004] According to a first aspect of this application, a structured light projector is provided, the structured light projector comprising: a light source, a first lens, a second lens, and a diffractive optical element;

[0005] The light source is used to emit a beam of light;

[0006] The first lens is used to focus the light beam emitted by the light source into a dot-shaped light spot;

[0007] The second lens is used to shape the dot-shaped light spot into a linear light spot;

[0008] The diffractive optical element is used to diffract the linear light spot into multiple parallel linear light spots, so that the structured light projected by the structured light projector presents a linear pattern.

[0009] According to a second aspect of this application, a three-dimensional scanning device is provided, the three-dimensional scanning device including a camera and the structured light projector mentioned in the first aspect above.

[0010] The technical solutions provided by the embodiments of this utility model may include the following beneficial effects:

[0011] The structured light projector provided by this utility model first focuses the light beam emitted by the light source into a small dot-shaped spot through a first lens, and then shapes the small dot-shaped spot into a line-shaped spot with a smaller diameter through a second lens. Then, the line-shaped spot is diffracted into multiple parallel line-shaped spots using diffraction optical elements. In this way, the lines projected by the structured light projector can be very fine, thus meeting the needs of some high-precision scenarios. Attached Figure Description

[0012] Figure 1This is a schematic diagram of a structured light projector in related technologies.

[0013] Figure 2 This is a schematic diagram of the structure of a structured light projector according to an embodiment of this application.

[0014] Figure 3 This is a schematic diagram of the line pattern projected by an adjustable structured light projector according to an embodiment of this application.

[0015] Figure 4 This is a schematic diagram of the structure of a structured light projector according to another embodiment of this application.

[0016] Figure 5 This is a schematic diagram of the structure of a structured light projector according to another embodiment of this application.

[0017] Figure 6 This is a schematic diagram of the structure of a three-dimensional scanning device according to an embodiment of this application. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions in the embodiments of this utility model, and to make the above-mentioned objectives, features and advantages of the embodiments of this utility model more apparent and understandable, the technical solutions in the embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0019] Structured light projectors are widely used in 3D scanning, robot vision, industrial inspection and other fields. A structured light projector is an optical device that is mainly used to project specific light patterns (such as lines, grids or dot matrix) onto the surface of a target object. By projecting structured light onto the surface of the target object and analyzing the deformation of the structured light pattern, the surface shape, size and defects of the object can be accurately measured.

[0020] In some scenarios, structured light projectors are needed to project linear structured light beams; these projectors can be called line structured light projectors. Currently, most line structured light projectors project relatively large diameter lines, meaning the projected linear light spots are quite thick, which cannot meet the needs of some scenarios requiring high measurement accuracy.

[0021] The applicant found through research that, Figure 1 As shown, current line structured light projectors typically include a light source, a lens, and diffractive optical elements. The light beam emitted by the light source is shaped by the lens to obtain a linear light spot, which is then diffracted by the diffractive optical elements to obtain multiple parallel, equally spaced linear light spots. Because the diameter of the linear light spot obtained after the light beam emitted by the light source is directly shaped by the lens is often relatively large, the diameter of the lines in the final projected pattern is also relatively large, which cannot meet the needs of some scenarios with high measurement accuracy requirements.

[0022] To address the aforementioned problems, embodiments of this application provide a structured light projector, such as... Figure 2 As shown, the structured light projector includes a light source 11, a first lens 12, a second lens 13, and a diffractive optical element 14. The first lens 12 is located between the light source 11 and the second lens 13, and the second lens 13 is located between the first lens 12 and the diffractive optical element 14. The light source 11 can be used to emit a light beam, and the light source 11 can be any light source capable of emitting a light beam, such as a semiconductor laser.

[0023] The first lens 12 is used to focus the light beam emitted by the light source 11 into a dot-shaped light spot. The first lens 12 can be any type of converging lens that has a converging effect on the light beam. The main function of the first lens 12 is to focus the light beam emitted by the light source 11 into a small dot-shaped light spot. The dot-shaped light spot can be a light spot obtained by focusing the light beam into a small area. Its shape can be circular, square, or irregular. This application embodiment does not impose any limitations.

[0024] The second lens 13 is used to shape the dot-shaped light spot obtained by focusing the light beam from the first lens 12 into a linear light spot. The second lens 13 can be any lens that can shape the light beam into a linear light spot. After the light beam emitted by the light source 11 is focused into a small dot-shaped light spot by the first lens 12, the second lens 13 is used to shape the dot-shaped light spot, thus obtaining a very small diameter, i.e., a very thin linear light spot.

[0025] The diffractive optical element 14 (DOE) is used to diffract the linear light spot into multiple parallel linear light spots, so that the structured light projected by the structured light projector presents a linear pattern. The diffractive optical element 14 is an optical element that can utilize the diffraction phenomenon of light to control and change the propagation direction, intensity distribution, and phase distribution of the light beam. By designing the optical parameters of the diffractive optical element 14, it is possible to diffract the linear light spot shaped by the second lens 13 into multiple parallel linear light spots, thereby obtaining a linear pattern.

[0026] The structured light projector provided in this application embodiment first focuses the light beam emitted by the light source 11 into a small dot-shaped spot through the first lens 12, and then the second lens 13 shapes the small dot-shaped spot into a line-shaped spot with a smaller diameter. Then, the diffractive optical element 14 diffracts the line-shaped spot into multiple parallel line-shaped spots. In this way, the lines projected by the structured light projector can be very fine, thereby meeting the needs of some high-precision scenarios.

[0027] In some embodiments, the first lens 12 may be a superlens. A superlens is an optical element made of metamaterials, whose working principle is based on the subwavelength structure of the metamaterials to modulate the phase, amplitude, and polarization properties of light. These subwavelength structures are often called "meta-atoms" and can achieve optical performance that is difficult to achieve with conventional optical elements. Superlenses can achieve super-diffraction-limited focusing, that is, focusing light into a region smaller than the wavelength of light. This is mainly due to their unique optical design and subwavelength structure. The core of a superlens is its subwavelength structure (often called "meta-atoms" or "nanostructures"). These structures can precisely control the phase of light. By designing the shape, size, and arrangement of these nanostructures, superlenses can achieve high-precision beam focusing and shaping in the far field.

[0028] Because superlenses can achieve super-diffraction-limited focusing—focusing light into a region smaller than the wavelength of light—the size of the light spot obtained by focusing using a superlens can be extremely small. Furthermore, the linear light spots obtained after shaping this spot can also be extremely fine, thus enabling the creation of very fine linear structured light patterns. In addition, the ultra-thin nature of superlenses helps reduce the overall size of the structured light projector, making it more suitable for compact devices.

[0029] In some embodiments, the second lens 13 may include one or more of the following: a Powell lens, a cylindrical lens.

[0030] A Powell lens can shape an incident light beam into a uniform linear light spot. This lens design ensures that the light is evenly distributed in a certain direction, thus forming a uniform line when projected onto a target surface. Due to its special optical design, the Powell lens can efficiently convert light energy into the desired linear light spot, reducing energy loss. Because the Powell lens can provide a very uniform light intensity distribution, it can be selected as the second lens 13 in applications requiring highly uniform light intensity distribution.

[0031] A cylindrical lens can focus a beam of light in one direction, forming a linear light spot. By selecting an appropriate focal length, the width and length of the line can be controlled. A cylindrical lens can flexibly control the shape and size of the beam by adjusting its focal length and position. Furthermore, the structure of a cylindrical lens is relatively simple, reducing manufacturing complexity. Therefore, for scenarios requiring simple design and flexible beam control, a cylindrical lens can be selected as the second lens 13.

[0032] In some embodiments, the cylindrical lens can be a planar cylindrical lens, where one side is a plane and the other side is a cylinder. This design makes the lens structurally more stable, easier to install and align. Similar to a cylindrical lens, a planar cylindrical lens can focus the light beam in one direction, forming a linear light spot. Due to its special optical design, the planar cylindrical lens can reduce aberrations and improve beam quality. Therefore, for scenarios requiring high stability and low aberration beams, the second lens 13 can be a planar cylindrical lens.

[0033] In some embodiments, the light source 11 may be a semiconductor laser, which has the advantages of high brightness, high monochromaticity and high coherence. Semiconductor lasers can provide high-brightness beams, which are suitable for applications that require high power. At the same time, the high monochromaticity and coherence of semiconductor lasers help to improve the stability and measurement accuracy of structured light.

[0034] Common semiconductor lasers include vertical-cavity surface-emitting lasers (VCSELs) and edge-emitting lasers (EELs). VCSELs emit beams with small divergence angles and circular spots, making them easy to couple with optical fibers and resulting in high coupling efficiency. The emission direction of a VCSEL is perpendicular to the substrate surface, facilitating the fabrication of two-dimensional arrays and making them suitable for high-density integration. Furthermore, VCSELs have low threshold currents, typically between 1-2 mA, resulting in low energy consumption. EELs offer higher single-emitter power, making them suitable for applications requiring high power. EELs have high power conversion efficiency, typically between 50-60%, and their beams can be shaped using external optical components, making them suitable for a variety of applications. In practical applications, the appropriate semiconductor laser can be selected as the light source based on the specific application scenario of the structured light projector.

[0035] In some embodiments, the structured light projector can be used in a 3D scanning device. Considering that the 3D scanning scene has high requirements for light source power, the light source 11 can be a multimode edge-emitting laser (EEL).

[0036] In some embodiments, the diffractive optical element 14 may be a diffraction grating, the period and angle of which are configured to diffract a linear light spot into a plurality of equally spaced parallel linear light spots along a specific direction. The surface of the diffraction grating has a periodically arranged fine structure, and diffraction occurs when light is incident on the grating. According to the diffraction formula:

[0037] dsinθ=mλ

[0038] Where: d is the period of the grating; θ is the diffraction angle; m is the diffraction order (integer); λ is the wavelength of light; by configuring a suitable grating period d and incident angle, the direction and intensity distribution of the diffracted light can be controlled, so that the diffraction grating can diffract linear light spots into multiple parallel linear light spots with equal spacing along a specific direction.

[0039] In some embodiments, the diffractive optical element 14 is a tunable diffractive optical element, and the diffraction characteristics of the tunable diffractive optical element can be adjusted by an external control signal to change the structured light pattern projected by the structured light projector. The structure of a conventional diffractive optical element 14 (e.g., a diffraction grating) is usually fixed; for example, once the diffractive optical element 14 is manufactured, its period and incident angle are fixed, and consequently, its diffraction characteristics are also fixed. However, in practical applications, it is generally desirable that the structured light pattern projected by the structured light projector can be flexibly changed and adjusted based on the actual scene to adapt to the needs of different scenarios. For example, as... Figure 3 As shown, taking line patterns as an example, it is often desirable to adjust the direction, spacing, etc., of the line patterns, which traditional structured light projectors cannot achieve. In order to allow the structured light pattern projected by the structured light projector to be dynamically adjusted to meet the needs of different application scenarios, in some scenarios, the diffraction optical element 14 is a tunable diffraction optical element. The diffraction characteristics of the tunable diffraction optical element can be adjusted. During use, the diffraction characteristics of the tunable diffraction optical element can be adjusted by inputting control signals in order to change the final projected structured light pattern.

[0040] For example, the diffractive optical element 14 can be a liquid crystal diffraction grating, whose diffraction characteristics can be adjusted by changing the alignment state of the liquid crystal, which can be controlled by applying an external electric field. Typically, liquid crystal molecules change their alignment direction under the action of an electric field, thereby changing the phase delay of light passing through the liquid crystal layer. This change in phase delay leads to changes in the diffraction angle and diffraction efficiency, which in turn can change the diffraction characteristics of the liquid crystal diffraction grating.

[0041] For example, the diffractive optical element 14 can be a magneto-optical diffraction grating, which can use the magneto-optical effect to change the propagation characteristics of light. By applying an external magnetic field, the refractive index of the material can be changed, thereby affecting the diffraction characteristics. Magneto-optical materials (such as certain crystals) will undergo a change in refractive index under the action of a magnetic field. This change can change the phase delay of light, thereby affecting the diffraction angle and diffraction efficiency.

[0042] Of course, the above are just exemplary examples. The tunable diffractive optical element can also be other types of optical elements with adjustable diffraction characteristics. This application does not impose any limitations.

[0043] In some embodiments, such as Figure 4As shown, the structured light projector also includes a collimating element 15, located between the light source 11 and the first lens 12, for collimating the divergent beam emitted by the light source 11 into a parallel beam. Typically, the beam emitted by the light source 11 is divergent. The collimating element 15 can convert the divergent beam emitted by the light source 11 into a parallel beam, thereby significantly improving the uniformity and directionality of the beam. This provides better beam conditions for subsequent focusing and shaping operations, which helps reduce energy loss and distortion of the beam in subsequent elements, ensuring that the shape and size of the final projected light spot meet design requirements.

[0044] In some embodiments, such as Figure 5 As shown, the structured light projector also includes a filter element 16, located between the light source 11 and the first lens 12, for filtering out stray light from the beam emitted by the light source 11. In fields such as 3D scanning, it is generally desirable for the structured light pattern projected by the structured light projector to have clear lines, thereby improving scanning accuracy and resolution. To project a clear structured light pattern, the purity of the beam emitted by the light source 11 is usually required to be high, with minimal stray light. However, due to its own limitations or various external light interferences, such as ambient light or reflected light from other light sources 11, the purity of the beam emitted by the light source 11 may be insufficient. To improve beam purity, a filter element 16 can be placed between the light source 11 and the first lens 12 to filter out stray light from the beam emitted by the light source 11, thereby improving beam purity, ensuring that the projected line pattern is clear and uniform, and reducing measurement errors. In some embodiments, the filter element 16 can be various filters, such as bandpass filters, polarizing filters, etc. In some embodiments, considering that the filtering effect of the filter may not be ideal, an aperture stop can also be used to filter out stray light. An anti-stray aperture stop is a physical structure specifically designed to suppress stray light interference in an optical system. Its core mechanism is to improve image plane purity by selectively intercepting non-imaging light rays. For example, it can block invalid light rays (such as ambient stray light) incident from outside the field of view and multiple reflections / scattering light within the system, preventing them from reaching the image plane and forming light spots or reducing contrast. Alternatively, the aperture stop surface can be coated with a black matte material (such as matte black paint) or designed with a rough inner wall / threaded structure to absorb and scatter stray light intensity, thereby achieving the effect of eliminating stray light.

[0045] In some embodiments, the centers of the light source 11, the first lens 12, the second lens 13, and the diffractive optical element 14 are located on the same straight line. When the centers of all optical elements are aligned, the beam propagation path between the elements is straight, without lateral offset. This straight-line propagation ensures that the shape and direction of the beam remain consistent across the elements, thereby reducing beam offset. Furthermore, by aligning the centers of all optical elements on the same straight line, the beam propagates along the same straight line between each element, reducing path differences and thus reducing optical distortion. This helps maintain the quality and shape of the beam, ensuring that the projected light spot meets design requirements.

[0046] When using a structured light projector, the centers of the light source 11, the first lens 12, the second lens 13, and the diffractive optical element 14 can be aligned on a straight line. This alignment design ensures that the beam transmission path is consistent among the various elements, reducing beam offset and distortion, and improving the stability and consistency of the optical system. This design simplifies the alignment and calibration process, reduces production costs and maintenance difficulty, and improves the reliability and performance of the system.

[0047] In addition, such as Figure 6 As shown in the embodiments of this application, a three-dimensional scanning device is also provided, which includes a camera 20 and a structured light projector 10 mentioned in the above embodiments. The three-dimensional scanning device may include one or more cameras. During the process of scanning a target object using the three-dimensional scanning device to reconstruct a three-dimensional model of the target object, a structured light pattern can be projected onto the surface of the target object using the structured light projector. Due to the shape and contour of the target object's surface, the structured light pattern will be deformed. For example, the projection of a linear light beam onto the object's surface may be bent or distorted. The camera can capture the deformation of the light pattern projected onto the target object's surface. To obtain complete three-dimensional information of the target object, it is usually necessary to photograph the target object from multiple angles, obtaining multiple images from different perspectives. Then, the target object can be reconstructed in three dimensions based on these images.

[0048] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the description disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the 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 exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0049] It should be understood that this invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

[0050] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the scope of protection of the present utility model.

Claims

1. A structured light projector, characterized in that, The structured light projector includes: a light source, a first lens, a second lens, and diffractive optical elements; The light source is used to emit a beam of light; The first lens is used to focus the light beam emitted by the light source into a dot-shaped light spot; The second lens is used to shape the dot-shaped light spot into a linear light spot; The diffractive optical element is used to diffract the linear light spot into multiple parallel linear light spots, so that the structured light projected by the structured light projector presents a linear pattern.

2. The structured light projector according to claim 1, characterized in that, The first lens includes a superlens.

3. The structured light projector according to claim 1, characterized in that, The second lens includes one or more of the following: Powell lens, cylindrical lens.

4. The structured light projector according to claim 1, characterized in that, The light source includes a semiconductor laser.

5. The structured light projector according to claim 1, characterized in that, The diffractive optical element is a diffraction grating, the period and angle of which are configured to diffract the linear light spot into multiple equally spaced parallel linear light spots along a specific direction.

6. The structured light projector according to claim 1, characterized in that, The diffractive optical element is a tunable diffractive optical element, and the diffraction characteristics of the tunable diffractive optical element can be adjusted by an external control signal to change the structured light pattern projected by the structured light projector.

7. The structured light projector according to claim 1, characterized in that, The structured light projector also includes a collimating element located between the light source and the first lens, which is used to collimate the light beam emitted by the light source into a parallel light beam.

8. The structured light projector according to claim 1, characterized in that, The structured light projector also includes a filter element located between the light source and the first lens, which is used to filter out stray light in the light beam emitted by the light source.

9. The structured light projector according to claim 1, characterized in that, The center of the light source, the center of the first lens, the center of the second lens, and the center of the diffractive optical element are located on the same straight line.

10. A three-dimensional scanning device, characterized in that, The three-dimensional scanning device includes a camera and a structured light projector as described in any one of claims 1-9.

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