Structured light imaging device

Abstract

The application discloses a structured light imaging device, which comprises a projection illuminating device, an imaging device and a control device. The projection illuminating device comprises a first light source, a first polarizer, a second light source, a second polarizer, a light combining device and a spatial light modulator. The first light source and the first polarizer can generate first polarized light, the second light source and the second polarizer can generate second polarized light, the light combining device combines the first polarized light or the second polarized light or combines the first polarized light and the second polarized light into one polarized light which is emitted to the spatial light modulator, and the spatial light modulator modulates the light beam incident thereto into specific structured light to project the structured light to an imaged object. The imaging device comprises a polarizing detector and an image sensor. The polarizing detector projects the structured reflected light reflected by the imaged object to the image sensor after polarization detection to form an image. The control device controls the opening and closing of the first light source and the second light source. The structured light imaging device can inhibit high light reflection, and improve the accuracy and integrity of three-dimensional reconstruction of a high light reflection object.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of three-dimensional reconstruction, and particularly relates to a structured light imaging device. BACKGROUND

[0002] With the increasingly wide application of three-dimensional detection technology in the industrial automation field, the three-dimensional reconstruction technology based on a structured light 3D camera which takes the principle of triangulation as the core is also increasingly popular. The structured light camera often adopts a projector combined with a camera in a manner that the main optical axis of the projector and the main optical axis of the camera form a certain angle. The projector projects structured light on an object, the camera captures a structured light image of the object, and then three-dimensional reconstruction is performed to obtain a height image of the object to reconstruct the surface topography of the object.

[0003] The structured light 3D camera is a kind of diffuse reflection imaging system. However, the material of the surface of some objects can cause mirror reflection on the surface of the object, and the object has high light reflection characteristics. Therefore, the image captured by the camera is difficult to solve the actual surface topography of the reconstructed object due to overexposure or overdarkness. SUMMARY

[0004] The present application mainly solves the technical problem that high-light objects are difficult to effectively perform three-dimensional reconstruction.

[0005] To solve the above technical problem, an embodiment of the present application provides a structured light imaging device, which comprises a projection illumination device, an imaging device and a control device.

[0006] The projection illumination device comprises a first light source, a first polarizer, a second light source, a second polarizer, a light combining device and a spatial light modulator.

[0007] The first polarizer is arranged on the light path of the first light beam emitted by the first light source, and is used for polarizing the first light beam into first polarized light of a first polarization direction.

[0008] The second polarizer is arranged on the light path of the second light beam emitted by the second light source, and is used for polarizing the second light beam into second polarized light of a second polarization direction. The first polarization direction is different from the second polarization direction.

[0009] The control device is used for controlling the opening and closing of the first light source and the second light source.

[0010] The light combining device is arranged at the intersection of the light path of the first polarized light and the light path of the second polarized light, and is used for converging the first polarized light and the second polarized light into the same light path and emitting to the spatial light modulator when the first light source and the second light source are both turned on, and emitting the first polarized light or the second polarized light to the spatial light modulator when only the first light source is turned on or only the second light source is turned on.

[0011] The spatial light modulator is configured to modulate a light beam incident thereto into a specific structured light to project the structured light to the imaged object;

[0012] The imaging device comprises a polarizer and an image sensor;

[0013] The polarizer is configured to receive structured reflected light formed by the structured light reflected by the imaged object, and to project the structured reflected light onto the image sensor after depolarization.

[0014] According to the structured light imaging device of the above embodiment, the projection illumination device comprises a first light source, a first polarizer, a second light source, a second polarizer, a light combining device and a spatial light modulator. The first light source and the first polarizer can generate first polarized light, and the second light source and the second polarizer can generate second polarized light, so that the projection illumination device can project structured light with one or both of the polarized light. The imaging device is provided with a polarizer, which can depolarize the structured reflected light reflected by the imaged object. Since the projection illumination device can project polarized light, and the polarization state of the reflected light will change to a certain extent after the polarized light is reflected by the object surface, the high reflection light and glare light of a specific polarization direction can be filtered out by the polarizer during imaging, thereby improving the three-dimensional reconstruction performance of the high reflection object. The light combining device can combine the first polarized light and the second polarized light into one polarized light, which is projected at the same time. Since the polarization direction of the first polarized light is different from that of the second polarized light, it is almost impossible for the polarizer to filter out both of the polarized light completely. When one of the polarized light is filtered out, the other polarized light can play a complementary role, which can suppress the high reflection light while ensuring the illumination brightness. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A schematic diagram of multiple reflections of light on the surface of an object;

[0016] Figure 2 A structural schematic diagram of a structured light imaging device according to an embodiment;

[0017] Figure 3 A schematic diagram of the polarization directions of the first polarizer and the second polarizer and the depolarization direction of the depolarizer according to an embodiment;

[0018] Figure 4 A structural schematic diagram of a structured light imaging device according to another embodiment;

[0019] Figure 5 A schematic diagram of the relationship between the light transmittance of the polarizer and the incident angle of the light;

[0020] Figure 6Schematic diagram of geometric relationship between projection image plane of spatial light modulator, main plane of projection lens and projection object plane;

[0021] Figure 7 Schematic diagram of structural light imaging device of another embodiment;

[0022] Figure 8 Schematic diagram of projection control module of an embodiment;

[0023] Figure 9 Schematic diagram of light path of S-polarized light and P-polarized light after passing through light combining device;

[0024] Figure 10 Schematic diagram of process of three-dimensional reconstruction by using S-polarized light and P-polarized light to suppress multiple reflection;

[0025] Figure 11 Comparison diagram of effect of reconstruction method for suppressing multiple reflection proposed in the present application and traditional reconstruction method;

[0026] Figure 12 Schematic diagram of visual field blind area of three-dimensional reconstruction.

[0027] Reference signs:

[0028] 100, projection illumination device; 101, first light source; 102, second light source; 103, first polarizer; 104, second polarizer; 105, light combining device; 106, spatial light modulator; 107, projection lens group; 108, first collimating lens group; 109, second collimating lens group; 110, reflecting mirror; 111, light homogenizing device; 112, first relay lens; 113, second relay lens; 114, compound prism; 200, imaging device; 201, polarizing analyzer; 202, image sensor; 203, imaging lens group; 300, control device; 400, imaged object. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with the drawings by specific embodiments. In different embodiments, similar elements are associated with similar element signs. In the following embodiments, many details are described in order to make the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different cases, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification in order to avoid the core part of the present application being overwhelmed by too much description, and it is not necessary to describe these related operations in detail for those skilled in the art according to the description in the specification and general technical knowledge in the art.

[0030] In addition, features described in the specification, operations or characteristics can be combined in any appropriate manner to form various embodiments. Meanwhile, the steps or actions in the method description can also be sequentially changed or adjusted in a manner that can be apparent to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment, and do not mean that the sequence is necessary, unless otherwise stated that a certain sequence must be followed.

[0031] The serial numbers of components in this paper, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any order or technical meaning. The "connection" and "coupling" in this application include direct and indirect connections (couplings) unless otherwise specified.

[0032] The existing structure light-based three-dimensional reconstruction method still has the following problems in dealing with complex surfaces (high reflectivity, multiple reflections, etc.):

[0033] 1. In the structure light three-dimensional reconstruction system, the imaging unit performs three-dimensional reconstruction by collecting the diffuse reflection image of the object surface, which uses the geometric constraint of reflected light. Its essence is that the incident light and the diffuse reflection light form a certain angle to form a triangular constraint. When the object surface is complex, the illumination light is incident on the object surface, and the complex surface causes multiple reflections. The image collected by the imaging unit is not the diffuse reflection image of the actual object surface, but a diffuse reflection image containing multiple surface information. Even if the reconstruction can be solved, the obtained topographic information cannot represent the true object surface information. For example, as shown in the figure, the incident light and the normal diffuse reflection light form a triangular constraint, but the geometric relationship between the multiple reflection light and the incident light is uncertain, which does not satisfy the triangular constraint. At this time, the geometric constraint of three-dimensional reconstruction is not established, resulting in incomplete and unrealistic reconstruction data; Figure 1

[0034] 2. Due to the angle, the structure light 3D camera will have 2 visual field blind areas: one is the area that the projector can illuminate but the camera cannot shoot; the second is the area that the camera can shoot but the projector cannot illuminate; These blind areas will cause incomplete reconstruction data.

[0035] In view of the above difficulties of the structure light-based three-dimensional reconstruction method, the existing method often uses a high-cost camera with low practicality, or a multiple exposure method without real-time performance to optimize the reconstruction integrity of the structure light three-dimensional reconstruction.

[0036] ​Patent application CN202310024635 uses a four-way polarization camera combined with a projected polarized light to solve the problem of high reflectivity. The four sets of polarization images of the polarization camera are fused to reconstruct the object's topography information, improving the robustness and reconstruction integrity of the system. Although the four-way polarization camera can provide reconstruction data in four polarization directions, it sacrifices the camera's resolution, with a system resolution of only one-fourth of a normal camera, and the camera cost is relatively high.

[0037] Patent application CN202210831038 uses a modified error energy function to remove abnormal invalid points. The error energy function combines the wrapped phase, background light intensity, and modulation light intensity related information of the fringe image. This patent application removes abnormal points from a purely algorithmic perspective, and does not solve the problem of high reflectivity and multiple reflections from an optical essence.

[0038] Patent application CN202110372335 uses multiple shooting to fuse reconstruction data under different projection intensities to solve the problem of high reflectivity. The optimal projection brightness number is estimated using image pixel features, and the corresponding number of fringe patterns is projected according to this number, and the object's fringe image is obtained by shooting. Fusing each group of fringe images obtains a high dynamic fringe image, and then reconstructs more complete data. This scheme trades time for completeness and does not have real-time performance. It also does not solve the problem of high reflectivity and multiple reflections from an optical perspective.

[0039] Patent application CN202110369458 uses a liquid crystal display to project linearly polarized light, and places a polarizer in front of the imaging lens. When the camera is shooting, the polarizer angle in front of the camera is rotated four times, and the corresponding coded images are collected. According to the four images, the Stokes parameters are calculated to determine the functional relationship between the linear polarization degree and the incident angle. Finally, the normal information of each point on the object surface is calculated according to the incident angle constraint condition, and the topography information of the object surface is obtained. This scheme uses the polarization characteristics of light to solve the problem of specular reflection, but it needs to mechanically rotate the polarizer in front of the lens and ensure the accuracy of the polarization angle, which is not very practical.

[0040] In addition, the disclosed method of using a polarizer to solve the problem of high reflectivity in structured light three-dimensional reconstruction can weaken or eliminate the high reflectivity phenomenon in certain areas of the image according to the difference between the polarization direction of the high reflectivity light and the imaging detection direction, but it also weakens the illumination intensity of other normally diffusely reflected areas, causing insufficient illumination and incomplete reconstruction due to dark imaging. This trade-off has created a new problem and has not improved the practicality of structured light three-dimensional reconstruction.

[0041] The application provides a high practicality, low cost, high real-time structured light imaging device, mainly aiming at the technical problem that the existing structured light 3D camera and three-dimensional reconstruction method cannot effectively solve the object surface multiple reflection, high reflection and visual field blind area, resulting in the inability to reconstruct complete data, and provides multiple embodiments to solve one or more of the above technical problems.

[0042] In some embodiments, an algorithm for suppressing multiple reflections is proposed, which combines polarization optical technology with an algorithm for suppressing multiple reflections, analyzes the characteristics of high reflection and abnormal reflection from the optical essence from the multidimension of optical principles and algorithm principles, proposes a technical solution consistent with theoretical analysis, and solves the difficult problems of poor reconstruction integrity and poor material adaptability caused by multiple reflections, high reflection and visual field blind area of the structured light three-dimensional reconstruction.

[0043] The concept of the application includes:

[0044] 1. When polarized light such as linearly polarized light is incident to the surface of an object and reflected, the polarization state of the reflected light will change to a certain extent, and a polarizer can filter out high reflection and glare light of a specific polarization direction.

[0045] 2. When linearly polarized light of different polarization directions is incident at the same angle, the reflectivity of the object surface is different (the reflection intensity is different), and the applicant realizes that the reflection intensity difference is large after multiple surface reflections. By using this point, the difference in reflectivity can be estimated to determine whether multiple reflections have occurred, and the reconstruction integrity can be improved.

[0046] 3. Multi-angle projection lighting can eliminate the area that the camera can shoot but the projector cannot illuminate.

[0047] According to the above concept, the applicant proposes a structured light imaging device of each embodiment of the application, which is described in detail below. Please refer to Figure 2 The structured light imaging device in some embodiments includes a projection lighting device 100, an imaging device 200 and a control device 300. The projection lighting device 100 adopts a two-channel illumination light source design, including a first light source 101, a first polarizer 102, a second light source 103, a second polarizer 104, a light combining device 105 and a spatial light modulator 106; the imaging device 200 includes a polarizer 201 and an image sensor 202.

[0048] The first light source 101 and the second light source 103 can be LED light sources, etc. The first polarizer 102 is disposed in the optical path of the first beam emitted by the first light source 101 and is used to polarize the first beam into first polarized light with a first polarization direction; the second polarizer 104 is disposed in the optical path of the second beam emitted by the second light source 102 and is used to polarize the second beam into second polarized light with a second polarization direction; wherein, the first polarized light and the second polarized light can be linearly polarized light, and the first polarization direction is different from the second polarization direction.

[0049] The control device 300 is used to control the opening and closing of the first light source 101 and the second light source 102. The first light source 101 and the second light source 102 are controlled by the control device 300 and can be both turned on or only one can be turned on.

[0050] The light combining device 105 is located at the intersection of the optical paths of the first polarized light and the second polarized light. When both the first light source 101 and the second light source 102 are turned on, it combines the first polarized light and the second polarized light into the same optical path and outputs them to the spatial light modulator 106. When only the first light source 101 or only the second light source 102 is turned on, it outputs either the first polarized light or the second polarized light to the spatial light modulator 106. The light combining device 105 combines the first polarized light and the second polarized light into the same optical path, which on the one hand makes the optical path structure compact, thus reducing the size of the projection lighting device 100; on the other hand, it allows the first polarized light and the second polarized light to share optical components, receive the same optical processing, and be incident at the same angle.

[0051] like Figure 2 As shown, in some embodiments, the optical paths of the first polarized light and the second polarized light are perpendicular. The light combining device 105 is a beam splitter (also called a semi-transparent and semi-reflective mirror). The beam splitter is at a 45° angle to both the optical paths of the first and second polarized light, and the first and second polarized light are incident on the beam splitter from opposite sides. One path of polarized light is transmitted through the beam splitter, while the other path is reflected, thus converging into the same optical path.

[0052] The spatial light modulator 106 modulates an incident light beam (e.g., the outgoing light from the light combiner 105) into a specific structured light beam, which is then projected onto the imaged object 400 to achieve structured light projection. In some embodiments, the structured light is used to project a fringe pattern, for example, by projecting a fringe pattern using an N-step phase-shifting method. The imaging device 200 acquires N fringe projection images of the imaged object 400 and transmits them to the control device 300 for three-dimensional reconstruction. The control device 300 is also used to receive a user-defined projection pattern and control the spatial light modulator 106 to modulate the light beam into structured light that projects the pattern. The spatial light modulator 106 can be a digital micromirror device (DMD), an LCD, or an LCOS, etc.

[0053] The imaged object can be a product or workpiece in industrial production, a mechanical part, an electronic component, etc., which is not limited in the present application.

[0054] The polarizer 201 is used to receive the structured reflected light formed by the structured light reflected by the imaged object 400, and project the structured reflected light onto the image sensor 202 after depolarization to form an image. The image sensor 202 can be a CMOS sensor or a CCD sensor, etc.

[0055] The structured light imaging device of the present application uses polarized light for projection by the projection illumination device 100, and the polarization state of the reflected light will change to a certain extent after the polarized light is reflected by the object surface. The high reflection and glare light of a specific polarization direction can be filtered out by the polarizer 201 during imaging, thereby improving the three-dimensional reconstruction performance of high reflection objects, and improving the reconstruction integrity and material adaptability. Preferably, the depolarization direction of the polarizer 201 is different from the first polarization direction and the second polarization direction, so that the high reflection and glare light can be better filtered out when using two kinds of polarized light for projection.

[0056] In addition, considering that in the existing method of adding a polarizer in front of the imaging lens to solve the high reflection problem, the high reflection area is weakened and eliminated, but the other diffuse reflection area is also weakened and the problem of insufficient light appears. In the present application, the light combining device 105 is provided, which can combine the first polarized light and the second polarized light into one polarized light. The control device 300 can control the first light source 101 and the second light source 102 to work simultaneously, so that two kinds of polarized light can be used to project the imaged object 400 simultaneously. Since the polarization direction of the first polarized light is different from the polarization direction of the second polarized light, it is almost impossible to be completely filtered out by the polarizer 201 at the same time. In this way, the light intensity of the diffuse reflection area is complemented while the high reflection area is weakened, thereby improving the final three-dimensional reconstruction integrity.

[0057] Preferably, the first polarization direction is perpendicular to the second polarization direction. For example, the first polarizer 103 is horizontally polarized (referred to as S polarization), and the second polarizer 104 is vertically polarized (referred to as P polarization). The following will be described taking this as an example. Further, the depolarization direction of the polarizer 201 is at an angle of 45° with the first polarization direction and the second polarization direction, as shown in the following figure. Figure 3The analyzer 201 can eliminate the high reflection and glare light caused by the first polarized light (S polarized light) source and the second polarized light (P polarized light) source. In addition, even in the extreme case, when the first polarized light (S polarized light) source is reflected by the object surface, the polarization direction of the light changes and is perpendicular to the polarization direction of the analyzer 201 of the imaging device 200, the light cannot pass through the analyzer 201, and the first polarized light (S polarized light) cannot be imaged. However, when the second polarized light (P polarized light) source is reflected by the object surface, the reflected light is almost impossible to be perpendicular to the polarization direction of the analyzer 201, and can still pass through the analyzer 201 to achieve illumination imaging. In the normal case, the first polarized light (S polarized light) source and the second polarized light (P polarized light) source form a complementary illumination of the diffuse reflection area. It should be noted that the analyzer in the present application is assembled during the system assembly stage, and does not need to be rotated again during the subsequent use process.

[0058] Please refer to Figure 4 In some embodiments, the projection illumination device 100 further comprises a first collimating lens group 108 and a second collimating lens group 109. The first collimating lens group 108 is arranged between the first light source 101 and the first polarizer 103, and is used for collimating the first light beam and projecting it onto the first polarizer 103. The second collimating lens group 109 is arranged between the second light source 102 and the second polarizer 104, and is used for collimating the second light beam and projecting it onto the second polarizer 104.

[0059] Generally, a collimating lens is arranged behind a light source to collimate the light beam emitted by the light source. For a polarizer, theoretically, it can be placed at any position in the light path of the projection illumination device 100 to achieve the effect of light polarization. However, the light transmittance is different when the polarizer is placed at different positions, and the overall light transmittance of the projection illumination device 100 is greatly different. For example, Figure 5 As shown in the figure, if the incident angle is summarized to the range of 0° to 90°, the transmittance of the polarizer decreases as the incident angle of the light decreases, and the transmittance is the highest when the incident angle is 90°. Most of the currently disclosed methods place the polarizer in front of the projection lens, and the projection lens is a FA lens. The light has a fixed field of view, and the incident angle of the light at the edge of the field of view is small, and the light transmittance is low, which affects the final light transmittance and uniformity. In the present application, the polarizer is placed behind the collimating lens group of the light source. The light passing through the collimating lens group can ensure good collimation, and the incident light angle of each field of view is close to 90°. The light transmittance of the light passing through the polarizer is close to the highest, which greatly improves the light transmittance and projection uniformity.

[0060] Please refer to Figure 2 and Figure 4In some embodiments, the projection illumination device 100 further comprises a projection lens group 107 (also referred to as a projection lens), which is arranged in the light path of the structured light and is configured to project the structured light onto the imaged object 400. The projection lens group 107 can be designed in a conventional FA design or a telecentric design.

[0061] Generally, the projection object plane is not perpendicular to the main optical axis of the projection lens 107, but is at an angle, for example, 60°, to the main optical axis of the projection lens 107, i.e., the main optical axis of the projection lens 107 is at an angle of 30° (or other angles, generally in the range of [27°, 30°]) to the main optical axis of the imaging device 200. In order to ensure the clarity of the projection object plane, the spatial light modulator 106 is arranged at an angle in the light path design, so that the projection image plane of the spatial light modulator 106, the main plane of the projection lens 107, and the projection object plane satisfy the Scheimpflug principle. As shown in FIG. 2, the projection image plane extension line, the projection lens main plane extension line, and the projection object plane extension line intersect at a point, so that even if the projection lens 107 is installed at an angle, a clear projection pattern can still be obtained on the object plane. Figure 6

[0062] Please refer to Figure 2 and Figure 4 In some embodiments, the imaging device 200 further comprises an imaging lens group 203 (also referred to as an imaging lens), and the polarizer 201 is arranged between the imaging lens group 203 and the image sensor 202. The imaging lens group 203 is configured to receive the structured reflected light formed by the structured light reflected by the imaged object 400 and converge the structured reflected light to the polarizer 201.

[0063] The imaging lens 203 is preferably designed in an image-side telecentric design or a double telecentric design. The polarizer 201 is arranged between the imaging lens 203 and the image sensor 202, and the imaging lens 203 is designed in an image-side telecentric lens or a double telecentric lens. In this way, the angle of the incident light passing through the polarizer 201 is as close to 90° as possible, so that the light transmittance and imaging uniformity on the imaging side can be ensured to be high. Under the same illumination brightness condition, the exposure time of the image sensor 202 is shorter, the photographing speed of the structured light three-dimensional imaging device is faster, and the real-time performance is higher.

[0064] Please refer to Figure 4 In some embodiments, the projection illumination device 100 further comprises a reflector 110, which is arranged in the light path of the light emitted by the light combining device 105 and is configured to reflect the light emitted by the light combining device 105 to the spatial light modulator 106. The angle θ between the normal of the reflecting surface of the reflector 110 and the light emitted by the light combining device 105 is in the range of 0° < θ < 90°, so that the light path of the light emitted by the light combining device 105 is bent.

[0065] Please refer to Figure 4 ​The projection illumination device 100 in some embodiments further comprises a light homogenizing device 111 arranged on the light path of the light emitted by the light combining device 105 and incident to the mirror 110, for homogenizing the light emitted by the light combining device 105 and projecting the homogenized light to the mirror 110. The light homogenizing device 111 can be a double-sided micro-lens array. The light homogenizing device 111 is arranged to make the light more uniform.

[0066] Please refer to Figure 4 The projection illumination device 100 in some embodiments further comprises a first relay lens 112 arranged on the light path of the light emitted by the light homogenizing device 111 and incident to the mirror 110, for converging the light emitted by the light homogenizing device 111 and projecting the converged light to the mirror 110. Since the light beam is more divergent after passing through the light homogenizing device 111, the first relay lens 112 is arranged in this embodiment to converge the light beam. For example, the light emitted by the light combining device 105 is cut into spots by the double-sided micro-lens array, and then converged by the first relay lens 112, so that the light is more concentrated.

[0067] Please refer to Figure 4 The projection illumination device 100 in some embodiments further comprises a second relay lens 113 arranged on the light path of the light reflected by the mirror 110 and incident to the spatial light modulator 106, for converging the light reflected by the mirror 110 and projecting the converged light to the spatial light modulator 106. The light beam is converged again here to improve the convergence effect.

[0068] As can be seen from Figure 4 The mirror 110 bends the originally straight light path, so that the optical devices can be more concentrated and compactly arranged in the projection illumination device 100.

[0069] Please refer to Figure 4 The projection illumination device 100 in some embodiments further comprises a compound prism 114 arranged in front of the spatial light modulator 106, so that the light emitted by the second relay lens 113 is incident to the spatial light modulator 106 through the compound prism 114, and the structured light emitted by the spatial light modulator 106 is reflected to the imaged object 400 through the compound prism 114.

[0070] The propagation path of the light in the compound prism 114 is as shown in Figure 4In some embodiments, the positions of the spatial light modulator 106 and the compound prism 114 are arranged in cooperation with the mirror 110, so that the direction of the structured light emitted by the compound prism 114 is opposite to the direction of the outgoing light of the light combining device 105, thereby making the overall light path of the projection illumination device 100 in the form of a U-turn, so that the structure of the projection illumination device 100 is more compact, and miniaturization is achieved. It should be noted that at this time, the projection image plane is not on the spatial light modulator 106, but is located on the reflection surface of the compound prism 114.

[0071] The control device 300 can include an embedded control system composed of a MCU (Microcontroller Unit), a SOC (System on Chips), a DSP (Digital Signal Processing) and / or a FPGA (Field Programmable Gate Array), which is mainly responsible for synchronization signal control, image processing and data transmission functions. The user can send instructions to the control device 300 through the host computer to control the structured light imaging equipment. The control device 300 starts the projection illumination device 100 and the imaging device 200 for projection and shooting according to the signal sent by the host computer. The shooting signal sent by the control device 300 to the imaging device 200 and the exposure time of the imaging device 200 need to be synchronized with the projection signal sent to the projection illumination device 100 and the projection time of the projection illumination device 100. After a series of projection and shooting of structured light patterns, the control device 300 collects the images imaged by the image sensor 200, starts the image algorithm for reconstruction and fusion, and finally obtains the height image of the imaged object 400, and then transmits the height image to the host computer.

[0072] Please refer to Figure 4 and Figure 7 In some embodiments, the control device 300 includes a projection control module for controlling the projection illumination device 100. The projection control module receives the control signal of the control device 300 and controls the two-channel light source (the first light source 101 and the second light source 102) and the spatial light modulator 106. When there are multiple projection illumination devices 100, each projection illumination device 100 corresponds to a projection control module for control, such as Figure 7 In some embodiments, the control device 300 includes a projection control module for controlling the projection illumination device 100. The projection control module receives the control signal of the control device 300 and controls the two-channel light source (the first light source 101 and the second light source 102) and the spatial light modulator 106. When there are multiple projection illumination devices 100, each projection illumination device 100 corresponds to a projection control module for control, such as Figure 8In some embodiments, the projection control module comprises a first light source control module, a second light source control module and a light modulation control module. The first light source control module and the second light source control module control the on-off enable and the current size of the two-channel light source respectively, and the projection brightness of the projection illumination device 100 is changed by adjusting the current size of the light source. The light modulation control module can control the pattern projected by the spatial light modulator 106.

[0073] In view of the difficulties in the structure light three-dimensional reconstruction described above, the existing methods usually improve and optimize the optical or algorithm scheme alone. The present application provides a reconstruction algorithm for suppressing multiple reflections in combination with the proposed structure light imaging device. Polarized light with different polarization directions is used to project structure light on the imaged object at the same incident angle. At this time, the reflectivity of the object surface is different, and the intensity of the polarized light reflected by the object surface at a certain position and imaged by the corresponding pixel position of the image sensor 220 is different, resulting in different intensities of the projection images of the imaged object collected. According to the difference in the projection image intensity, the multiple reflection area is identified, and the height image reconstructed is corrected. The present application analyzes the difference between multiple reflections and normal reflections from the optical essence, and solves the difficult problem of multiple reflections in three-dimensional reconstruction of complex surface objects by combining polarized optical technology and image processing algorithm. Among them, the structure light imaging device of the present application can be used to project structure light on the imaged object with different polarization directions at the same incident angle by controlling the device 300 to control the double-channel illumination light source to be lit in turn, so as to obtain two polarized structure light images with different polarization directions of the imaged object.

[0074] Therefore, under the control of the control device 300, the projection illumination device 100 can realize at least three projection modes: single-polarization projection mode: single-channel illumination light source is lit, that is, only one of the first light source 101 and the second light source 102 is turned on; double-polarization projection mode: double-channel illumination light source is lit at the same time, that is, the first light source 101 and the second light source 102 are both turned on, and the first polarized light and the second polarized light are projected at the same time, which can realize the complementation of the double-polarized light source; alternating projection mode: double-channel illumination light source is lit in turn, that is, the projection illumination device 100 projects structure light twice, once the first light source 101 is turned on and the second light source 102 is turned off, and the first polarized light is projected, and the other time the first light source 101 is turned off and the second light source 102 is turned on, and the second polarized light is projected, which can realize the suppression of multiple reflections. The user can input instructions to select the projection mode, and the corresponding single-polarization projection mode, double-polarization projection mode and alternating projection mode are respectively the first imaging instruction, the second imaging instruction and the third imaging instruction.

[0075] When receiving the first imaging instruction input by the user, the control device 300 controls the projection illumination device 100 to project structured light on the imaged object 400 in the single-polarization projection mode, triggers the imaging device 200 to capture the imaged object 400, obtains a first polarized structured light image of the imaged object 400, performs three-dimensional reconstruction using the first polarized structured light image, and obtains a height image of the imaged object 400. The three-dimensional reconstruction here can adopt any three-dimensional reconstruction method, which is not limited in the present application.

[0076] When receiving the second imaging instruction input by the user, the control device 300 controls the projection illumination device 100 to project structured light on the imaged object 400 in the double-polarization projection mode, triggers the imaging device 200 to capture the imaged object 400, obtains a second polarized structured light image of the imaged object 400, performs three-dimensional reconstruction using the second polarized structured light image, and obtains a height image of the imaged object 400. The three-dimensional reconstruction here can adopt any three-dimensional reconstruction method, which is not limited in the present application.

[0077] When receiving the third imaging instruction input by the user, the control device 300 controls the projection illumination device 100 to project structured light on the imaged object 400 in the alternating projection mode, which is projected twice. Each time the control device 300 triggers the imaging device 200 to capture the imaged object 400, a third polarized structured light image and a fourth polarized structured light image of the imaged object 400 are obtained. Three-dimensional reconstruction is performed using the third polarized structured light image and the fourth polarized structured light image, and a height image of the imaged object 400 is obtained.

[0078] The three-dimensional reconstruction using the third polarized structured light image and the fourth polarized structured light image to obtain the height image of the imaged object 400 includes:

[0079] The three-dimensional reconstruction using the third polarized structured light image to obtain a first height image of the imaged object 400, and the three-dimensional reconstruction using the fourth polarized structured light image to obtain a second height image of the imaged object 400. The three-dimensional reconstruction here can adopt any three-dimensional reconstruction method, which is not limited in the present application.

[0080] A reflectivity difference map is calculated according to the third polarized structured light image and the fourth polarized structured light image. The pixel value of each pixel position of the reflectivity difference map represents the reflectivity difference degree of the pixel position, and the reflectivity difference degree represents the difference degree between the reflectivity of the first polarized light and the reflectivity of the second polarized light of the surface of the imaged object 400 corresponding to the pixel position.

[0081] According to the reflectivity difference map, it is judged whether the surface of the imaged object 400 corresponding to each pixel position exists multiple reflections, if yes, the height value of the pixel position is set as an invalid pixel value, if not, the final height value of the pixel position is determined according to the height values of the first height image and the second height image at the pixel position, so as to finally obtain the height image of the imaged object 400.

[0082] The applicant has carried out research on the projection of the fringe pattern in the structured light projection. The general N-step cosine phase shift method is used for three-dimensional reconstruction. The standard N-step cosine fringe pattern is projected onto the imaged object by controlling the projection illumination device 100, and N fringe projection images are collected by the imaging device 200. The phase image is obtained by the phase solving method, and the height image is reconstructed by combining the geometric constraint parameters of the projection illumination device 100 and the imaging device 200 which are pre-calibrated. Wherein N is an integer not less than 2.

[0083] The N-step phase shift method can be divided into encoding and decoding. First, the fringe pattern is encoded according to a certain rule and sent to the spatial light modulator 106 for projection. The encoding formula of the N-step fringe projection pattern is as follows:

[0084]

[0085] Wherein, I is the ideal projection intensity, I(x,y) represents the ideal projection intensity at the pixel position (x,y), represents the phase of the pixel position (x,y), A is the encoding background light intensity, B is the encoding modulation light intensity, both of which are ideal encoding values, and k is the step number.

[0086] After the fringe pattern is projected onto the object, the imaging device 200 performs imaging, and the N fringe projection images are decoded or said phase solving processing is performed to obtain the phase, the decoding background light intensity and the decoding modulation light intensity. The decoding formula is as follows:

[0087]

[0088] Wherein, I' is the intensity (gray value) of the photographed fringe projection image, I'(x,y) represents the intensity at the pixel position (x,y), A' is the decoding background light intensity, and B' is the decoding modulation light intensity.

[0089] Due to the influence of environmental light, light incidence angle difference, optical lens difference, nonlinear response of image sensor and reflectivity difference of object surface, the relationship between the ideal projection intensity and the intensity of the actually photographed fringe projection image can be briefly expressed as:

[0090] I'(x,y)=I(x,y)·F(x,y)·ξ(x,y)+μ(x,y), (3)

[0091] Wherein, μ(x, y) is the influence of the background ambient light on the pixel position (x, y), that is, the background light intensity collected by the imaging device 200 when the projection illumination device 100 is turned off; F(x, y) is the reflectivity of the surface of the imaged object corresponding to the pixel position (x, y); ξ(x, y) is the collective expression of other nonlinear influencing factors. After substituting formula (1), (2) into (3) and simplifying, the following formula can be obtained:

[0092]

[0093] From the above formula, the following formula can be obtained:

[0094] A' = A·F(x, y)·ξ(x, y) + μ(x, y),

[0095] B' = B·F(x, y)·ξ(x, y),

[0096] The above two formulas show that the difference in the reflectivity of the object surface can be reflected in the decoding of the background light intensity and the decoding of the modulated light intensity.

[0097] In the process of using the structured light imaging device of the present application to project and reconstruct with two polarized light sources (first polarized light and second polarized light) of different polarization directions, the current of the first light source 101 and the second light source 102 can be controlled by the control device 300 to be consistent, so as to ensure that the brightness of the light sources of the two channels is strictly consistent; and because the light sources of the two channels share the optical device, the imaging process also shares the image sensor, so the nonlinear influencing factors ξ(x, y) of the two projection reconstruction processes can be considered to be consistent; the environmental background light μ(x, y) is also consistent. Therefore, the first background light intensity image and the first modulated light intensity image obtained by projecting and reconstructing the first polarized light, and the second background light intensity image and the second modulated light intensity image obtained by projecting and reconstructing the second polarized light can be represented as:

[0098] A1'(x, y) = A(x, y)·F1(x, y)·ξ(x, y) + μ(x, y),

[0099] B1'(x, y) = B(x, y)·F1(x, y)·ξ(x, y),

[0100] A'2(x, y) = A(x, y)·F2(x, y)·ξ(x, y) + μ(x, y),

[0101] B'2(x, y) = B(x, y)·F2(x, y)·ξ(x, y),

[0102] Wherein, A1' represents the first background light intensity image, A1'(x, y) represents the first background light intensity at pixel position (x, y), A'2 represents the second background light intensity image, A'2(x, y) represents the second background light intensity at pixel position (x, y), B1' represents the first modulation light intensity image, B1'(x, y) represents the first modulation light intensity at pixel position (x, y), B'2 represents the second modulation light intensity image, and B'2(x, y) represents the second modulation light intensity at pixel position (x, y).

[0103] By subtraction, we have:

[0104] ΔA' = A1'- A'2 = [F1(x, y)- F2(x, y)]·A·ξ(x, y),

[0105] ΔB' = B1'- B'2 = [F1(x, y)- F2(x, y)]·B·ξ(x, y),

[0106] Wherein, ΔA' represents the difference between the first background light intensity image and the second background light intensity image, and ΔB' represents the difference between the first modulation light intensity image and the second modulation light intensity image.

[0107] Therefore, the reflectivity difference of the two times of polarized light projection reconstruction can be quantitatively represented by the numerical difference of the decoded background light intensity or the decoded modulation light intensity of the two times of reconstruction. Therefore, the reflectivity difference map ΔF can be determined by the following formula:

[0108] ΔF = ΔA' = A1'- A'2, (4)

[0109] Or,

[0110] ΔF = ΔB' = B1'- B'2, (5)

[0111] Although both of the above can represent the reflectivity difference, when the object surface is translucent, the contrast of the black and white stripe image is too low to cause the decoded modulation light intensity to be too low, and the reflectivity cannot be accurately reflected. At this time, it is more appropriate to use the decoded background light intensity to represent the reflectivity difference. When the object surface is a complex textured surface, the decoded background light intensity cannot accurately reflect the reflectivity, the contrast of the black and white stripe image is high, the decoded modulation light intensity is high, and it is more appropriate to use the decoded modulation light intensity to represent the reflectivity difference. In order to improve the stability and applicability of the system, the application preferably adopts a linear weighted manner to combine the difference of the reflectivity:

[0112] ΔF = α·ΔA' + (1-α)·ΔB', (6)

[0113] Wherein, α is a preset weight value, which is set by the user according to the use scene, and the value range is [0.0, 1.0].

[0114] Based on the above analysis, when the stripe pattern projection is used for three-dimensional reconstruction, the control device 300 controls the projection illumination device 100 to project structured light on the imaged object 400 in an alternating projection mode, including: controlling the projection illumination device 100 to project stripe patterns on the imaged object 400 in an alternating projection mode according to the N-step phase shift method. Then the third polarized structured light image includes N first stripe projection images obtained by projecting stripe patterns on the imaged object in the first polarized light according to the N-step phase shift method, and the fourth polarized structured light image includes N second stripe projection images obtained by projecting stripe patterns on the imaged object in the second polarized light according to the N-step phase shift method.

[0115] The control device 300 performs three-dimensional reconstruction using the third polarized structured light image to obtain a first height image of the imaged object 400, and performs three-dimensional reconstruction using the fourth polarized structured light image to obtain a second height image of the imaged object 400, and calculates a reflectivity difference map according to the third polarized structured light image and the fourth polarized structured light image, including:

[0116] The N first stripe projection images are subjected to phase unwrapping processing to obtain a first phase image, a first background light intensity image, and a first modulation light intensity image; the N second stripe projection images are subjected to phase unwrapping processing to obtain a second phase image, a second background light intensity image, and a second modulation light intensity image; here, the phase unwrapping processing can use any phase unwrapping method, which is not limited in the present application;

[0117] The first height image is obtained by three-dimensional reconstruction according to the first phase image; the second height image is obtained by three-dimensional reconstruction according to the second phase image; here, the three-dimensional reconstruction can use any three-dimensional reconstruction method, which is not limited in the present application;

[0118] The reflectivity difference map is calculated according to the difference between the first background light intensity image and the second background light intensity image, or according to the difference between the first modulation light intensity image and the second modulation light intensity image, or according to the difference between the first background light intensity image and the second background light intensity image, and the difference between the first modulation light intensity image and the second modulation light intensity image. The specific determination formula of the reflectivity difference map is shown in the above formulas (4), (5), and (6).

[0119] Regarding the height image of the imaged object 400 finally obtained, it is essentially obtained by fusing the first height image and the second height image using the reflectivity difference map, and in some embodiments, the height image of the imaged object 400 fused is determined by the following formula:

[0120]

[0121] Wherein, H(x, y) represents the height value at pixel position (x, y) in the height image of the imaged object 400 finally obtained, H1(x, y) represents the height value at pixel position (x, y) in the first height image, H2(x, y) represents the height value at pixel position (x, y) in the second height image, ΔF(x, y) represents the reflectivity difference degree at pixel position (x, y) in the reflectivity difference map, T is a preset reflectivity difference degree threshold, and Inv represents an invalid pixel value.

[0122] The following takes the first polarized light as S-polarized light and the second polarized light as P-polarized light as an example to illustrate the steps of three-dimensional reconstruction by using the dual-polarized light source to suppress multiple reflections. As shown in FIG. 2, Figure 9 The polarization directions of the S-polarized light and the P-polarized light are perpendicular, and after passing through the light combining device 105, the S-polarized light and the P-polarized light propagate along the same light path, Figure 9 The S-polarized light and the P-polarized light are shown at the same time for convenience of display, but it does not mean that the S-polarized light and the P-polarized light must be turned on at the same time. Please refer to Figure 10 The specific steps include:

[0123] 1. Turn on the first light source 101 (i.e., turn on the S-polarized light source) and turn off the second light source 102 (i.e., turn off the P-polarized light source) to project the fringe pattern, and obtain N first fringe projection images obtained by using S-polarized light projection through the image sensor 202, and perform phase unwrapping processing to obtain a first phase image, a first background light intensity image and a first modulation light intensity image;

[0124] 2. Turn on the second light source 102 (i.e., turn on the P-polarized light source) and turn off the first light source 101 (i.e., turn off the S-polarized light source) to project the fringe pattern, and obtain N second fringe projection images obtained by using P-polarized light projection through the image sensor 202, and perform phase unwrapping processing to obtain a second phase image, a second background light intensity image and a second modulation light intensity image;

[0125] 3. Perform three-dimensional reconstruction on the first phase image and the second phase image respectively through the geometric constraint relationship calibrated in advance to obtain a first height image and a second height image;

[0126] 4. Perform polarization light reflectivity difference calculation according to the difference between the first background light intensity image and the second background light intensity image and the difference between the first modulation light intensity image and the second modulation light intensity image to obtain a reflectivity difference map, please refer to formula (6) for details.

[0127] 5. Perform threshold comparison according to the reflectivity difference map to determine the pixel region where multiple reflections exist, set the corresponding height value as an invalid pixel value, thereby eliminating abnormal data caused by multiple reflections, and finally fuse to obtain a height image suppressing multiple reflections, please refer to formula (7) for details.

[0128] Please refer toFigure 11 It can be seen that, when facing a multiple reflection surface, the surface reconstructed by the conventional three-dimensional reconstruction method (Fig. (b)) is jagged, which is inconsistent with the actual situation, while the method of the present application correctly reconstructs the multiple reflection surface (Fig. (c)).

[0129] In view of the problem of the visual field blind area, the structured light imaging device of some embodiments of the present application adopts a double projection illumination device to irradiate the imaged object from two different incident angles, and achieves the removal of part of the visual field blind area through image fusion. Specifically, as shown in Figure 7 , the structured light imaging device includes two projection illumination devices 100, which are symmetrically arranged with the imaging device 200 as the center, and the two projection illumination devices 100 can implement projection illumination on the imaged object from two different incident angles, thereby solving the problem of reconstruction blind area caused by illumination blind area. Please refer to Figure 12 , when using a single projection illumination device for reconstruction, the A area in the figure is the camera shooting blind area, which cannot be shot even if it can be illuminated, resulting in the inability to reconstruct; the B area in the figure is the illumination blind area, which can be shot by the camera but cannot be illuminated, resulting in the inability to reconstruct. The embodiment adopts a double projection illumination device for projection illumination, and through twice projection reconstruction of the projection illumination devices placed in the symmetric direction, the illumination blind area of the B area in the figure can be removed after fusion.

[0130] Based on the double projection illumination device, the control device 300 is further configured to, when receiving an imaging instruction input by a user:

[0131] control one of the two projection illumination devices to perform structured light projection on the imaged object in a projection mode corresponding to the imaging instruction, so as to perform three-dimensional reconstruction and obtain a first projection direction height image;

[0132] control the other of the two projection illumination devices to perform structured light projection on the imaged object in a projection mode corresponding to the imaging instruction, so as to perform three-dimensional reconstruction and obtain a second projection direction height image;

[0133] fuse the first projection direction height image and the second projection direction height image to obtain a height image of the imaged object.

[0134] The user can select the projection mode according to the actual scene needs. In the scene with higher real-time requirement, the single-polarization projection mode of only turning on the single-channel polarized light source can be selected; in the scene with multiple reflections, the alternate projection mode can be selected; in the scene with high reflection and glare, the double-polarization projection mode of simultaneously turning on the double-channel polarized light source can be selected. In each projection mode, the control device 300 adopts the corresponding three-dimensional reconstruction method for reconstruction.

[0135] In some embodiments, the height image of the imaged object is determined by the following equation:

[0136]

[0137] where I h (x,y) represents the height value at pixel position (x,y) in the height image of the imaged object, H 1d (x,y) represents the height value at pixel position (x,y) in the first projection direction height image, H 2d (x,y) represents the height value at pixel position (x,y) in the second projection direction height image.

[0138] Two symmetrically arranged projection illumination devices 100 are defined as one projection illumination combination, that is, one projection illumination combination includes two projection illumination devices 100, and the two projection illumination devices 100 are symmetrically arranged with the imaging device 200 as the center. In some embodiments, the structured light imaging equipment can include at least one projection illumination combination.

[0139] The structured light imaging equipment provided by the embodiments of the present application can use polarized light for projection by the projection illumination device, and the polarization state of the reflected light will change to a certain extent after the polarized light is reflected by the object surface. The high-reflective light and glare light of a specific polarization direction can be filtered out by the analyzer during imaging, thereby improving the three-dimensional reconstruction performance of the high-reflective object and improving the reconstruction integrity and material adaptability.

[0140] In addition, the light combining device can combine the first polarized light and the second polarized light into one polarized light and simultaneously project. Since the polarization direction of the first polarized light is different from the polarization direction of the second polarized light, it is almost impossible to be completely filtered out by the analyzer at the same time. When one kind of polarized light is filtered out, the other kind of polarized light can play a complementary role, thereby suppressing the high-reflective light while ensuring the illumination brightness.

[0141] At the same time, the light combining device also makes the optical path structure compact to a certain extent. In some embodiments, in cooperation with the compound prism, the miniaturization of the equipment can be realized.

[0142] In some embodiments, by setting the positions of the polarizer and the analyzer, the structured light imaging equipment of the present application has high light transmission efficiency and high uniformity of light.

[0143] In an embodiment of the present application, a reconstruction method for suppressing multiple reflections is also proposed, which solves the difficult problem of multiple reflections in three-dimensional reconstruction of complex surface objects by combining polarization optics technology and image processing algorithm, thereby improving the reconstruction integrity.

[0144] The structured light imaging device in the embodiment of the present application further removes the illumination blind area and further improves the reconstruction integrity by setting two projection illumination devices which are symmetrically relative to the imaging device as the center and irradiating the imaged object from two different incident angles.

[0145] Those skilled in the art can understand that all or part of the functions of the various methods in the above embodiments can be realized by hardware or by a computer program. When all or part of the functions in the above embodiments are realized by a computer program, the program can be stored in a computer readable storage medium, which can include a read-only memory, a random access memory, a magnetic disk, an optical disk, a hard disk, etc. The above functions are realized by executing the program by a computer. For example, the program is stored in a memory of a device, and when the program in the memory is executed by a processor, the above all or part of the functions are realized. In addition, when all or part of the functions in the above embodiments are realized by a computer program, the program can also be stored in a storage medium such as a server, another computer, a disk, an optical disk, a flash disk or a mobile hard disk, and is downloaded or copied into the memory of a local device or the system of the local device is updated, and when the program in the memory is executed by a processor, the above all or part of the functions in the embodiments are realized.

[0146] The above application of specific examples is used to help understand the present application and does not limit the present application. Those skilled in the art can make several simple deductions, deformations or substitutions according to the idea of the present application.

Claims

1. A structured light imaging device, characterized in that, Includes projection lighting devices, imaging devices, and control devices; The projection lighting device includes a first light source, a first polarizer, a second light source, a second polarizer, a light combining device, and a spatial light modulator; The first polarizer is disposed in the optical path of the first beam emitted by the first light source, and is used to polarize the first beam into first polarized light with a first polarization direction. The second polarizer is disposed in the optical path of the second beam emitted by the second light source, and is used to polarize the second beam into second polarized light with a second polarization direction; wherein the first polarization direction is different from the second polarization direction. The control device is used to control the opening and closing of the first light source and the second light source; The light combining device is located at the intersection of the optical path of the first polarized light and the optical path of the second polarized light. When both the first light source and the second light source are turned on, it combines the first polarized light and the second polarized light into the same optical path and emits them to the spatial light modulator. When only the first light source or only the second light source is turned on, it emits the first polarized light or the second polarized light to the spatial light modulator. The spatial light modulator is used to modulate the incident light beam into a specific structured light to project the structured light onto the object being imaged; The imaging device includes an analyzer and an image sensor, wherein the polarization direction of the analyzer is different from both the first polarization direction and the second polarization direction. The analyzer is used to receive the structured light reflected by the object being imaged, and to analyze the structured light before projecting it onto the image sensor for imaging.

2. The structured light imaging device as described in claim 1, characterized in that, The first polarization direction is perpendicular to the second polarization direction.

3. The structured light imaging device as described in claim 2, characterized in that, The polarization direction of the analyzer is at a 45° angle to both the first polarization direction and the second polarization direction.

4. The structured light imaging device as described in claim 1, characterized in that, The projection lighting device further includes a first collimating lens group and a second collimating lens group; The first collimating lens group is disposed between the first light source and the first polarizer, and is used to collimate the first beam and project it onto the first polarizer; The second collimating lens group is disposed between the second light source and the second polarizer, and is used to collimate the second beam and project it onto the second polarizer.

5. The structured light imaging device as described in claim 1, characterized in that, The optical paths of the first polarized light and the second polarized light are perpendicular, and the light combining device is a beam splitter; The beam splitter is at a 45° angle to both the optical path of the first polarized light and the optical path of the second polarized light, and the first polarized light and the second polarized light are incident on the beam splitter from both sides of the beam splitter.

6. The structured light imaging device as described in claim 1, characterized in that, The projection lighting device further includes a reflector, which is disposed in the optical path of the light output of the light combining device and is used to reflect the light output of the light combining device to the spatial light modulator; the angle θ between the normal of the reflector surface and the light output of the light combining device is in the range of 0° < θ < 90°.

7. The structured light imaging device as described in claim 6, characterized in that, The projection lighting device further includes a light homogenizing device, which is disposed on the optical path from the light combining device to the reflector, and is used to homogenize the light emitted from the light combining device before projecting it onto the reflector.

8. The structured light imaging device as described in claim 7, characterized in that, The projection lighting device further includes a first relay lens, which is disposed on the optical path from the light output of the light homogenizing device to the reflector, and is used to converge the light output of the light homogenizing device and project it onto the reflector.

9. The structured light imaging device as described in claim 7 or 8, characterized in that, The projection lighting device further includes a second relay lens, which is disposed on the optical path from the reflected light of the reflector to the spatial light modulator, and is used to converge the reflected light of the reflector and project it onto the spatial light modulator.

10. The structured light imaging device as described in claim 9, characterized in that, The projection lighting device further includes a composite prism, which is disposed in front of the spatial light modulator so that the light emitted from the second relay lens is incident on the spatial light modulator through the composite prism, and the structured light emitted from the spatial light modulator is reflected onto the object being imaged by the composite prism.

11. The structured light imaging device as described in claim 1, characterized in that, The projection lighting device further includes a projection lens group, which is disposed in the optical path of the structured light and is used to project the structured light onto the object being imaged. The projection image plane of the spatial light modulator, the principal plane of the projection lens group, and the projection object plane satisfy Schahm's law.

12. The structured light imaging device as described in claim 1, characterized in that, The imaging device further includes an imaging lens group, and the analyzer is disposed between the imaging lens group and the image sensor; The imaging lens group is used to receive the structured light reflected by the object being imaged, and to converge and project it onto the analyzer.

13. The structured light imaging device as described in claim 12, characterized in that, The imaging lens group is an image-side telecentric lens or a double telecentric lens.

14. The structured light imaging device as described in claim 1, characterized in that, The control device is used for: When the first imaging command input by the user is received, the projection lighting device is controlled to project structured light onto the object to be imaged in a single polarization projection mode, triggering the imaging device to take a picture of the object to be imaged, thereby obtaining a first polarization structured light image of the object to be imaged, and using the first polarization structured light image to perform three-dimensional reconstruction to obtain a height image of the object to be imaged; in the single polarization projection mode, only one of the first light source and the second light source is turned on. When a second imaging command is received from the user, the projection lighting device is controlled to project structured light onto the object being imaged in a dual-polarization projection mode, triggering the imaging device to capture an image of the object being imaged, thereby obtaining a second-polarization structured light image of the object being imaged. The second-polarization structured light image is then used for three-dimensional reconstruction to obtain a height image of the object being imaged. In the dual-polarization projection mode, both the first light source and the second light source are turned on. When a third imaging command is received from the user, the projection illumination device is controlled to project structured light onto the object being imaged in an alternating projection mode. In this alternating projection mode, the projection illumination device performs two structured light projections: once with the first light source on and the second light source off, and again with the first light source off and the second light source on. Each projection triggers the imaging device to capture an image of the object being imaged, resulting in a third-polarization structured light image and a fourth-polarization structured light image of the object. The third-polarization structured light image and the fourth-polarization structured light image are then used to perform three-dimensional reconstruction to obtain the height image of the object being imaged. The step of using the third polarization structured light image and the fourth polarization structured light image to perform three-dimensional reconstruction to obtain the height image of the imaged object includes: The first height image of the imaged object is obtained by performing three-dimensional reconstruction using the third polarization structured light image; the second height image of the imaged object is obtained by performing three-dimensional reconstruction using the fourth polarization structured light image. A reflectance difference map is calculated based on the third polarization structured light image and the fourth polarization structured light image. The pixel value of each pixel position in the reflectance difference map represents the degree of reflectance difference at that pixel position. The degree of reflectance difference represents the degree of difference between the reflectance of the surface of the imaged object corresponding to that pixel position to the first polarized light and the reflectance to the second polarized light. Based on the reflectivity difference map, it is determined whether there is multiple reflection on the surface of the object being imaged corresponding to each pixel position. If so, the height value of the pixel position is set as an invalid pixel value. If not, the final height value of the pixel position is determined based on the height values ​​of the first height image and the second height image at that pixel position, so as to obtain the height image of the object being imaged.

15. The structured light imaging device as described in claim 14, characterized in that, The step of controlling the projection illumination device to project structured light onto the object being imaged in an alternating projection mode includes: controlling the projection illumination device to project a stripe pattern onto the object being imaged in an alternating projection mode using an N-step phase-shifting method; where N is an integer not less than 2. The third polarization structured light image includes N first fringe projection images obtained when the first polarized light is used to project a fringe pattern onto the imaged object using an N-step phase-shifting method; the fourth polarization structured light image includes N second fringe projection images obtained when the second polarized light is used to project a fringe pattern onto the imaged object using an N-step phase-shifting method. The process involves using the third polarization structured light image for 3D reconstruction to obtain a first height image of the imaged object, using the fourth polarization structured light image for 3D reconstruction to obtain a second height image of the imaged object, and calculating a reflectance difference map based on the third and fourth polarization structured light images, including: Phase-de-phase processing is performed on N first fringe projection images to obtain a first phase image, a first background light intensity image, and a first modulated light intensity image; phase-de-phase processing is performed on N second fringe projection images to obtain a second phase image, a second background light intensity image, and a second modulated light intensity image; Three-dimensional reconstruction is performed based on the first phase image to obtain the first height image; three-dimensional reconstruction is performed based on the second phase image to obtain the second height image; The reflectance difference map is calculated based on the difference between the first background light intensity image and the second background light intensity image, or the reflectance difference map is calculated based on the difference between the first modulated light intensity image and the second modulated light intensity image, or the reflectance difference map is calculated based on the difference between the first background light intensity image and the second background light intensity image, and the difference between the first modulated light intensity image and the second modulated light intensity image.

16. The structured light imaging device as described in claim 15, characterized in that, The reflectance difference map is determined by the following formula: ， or, , or, ; in, ΔF This represents the reflectivity difference map. This indicates the difference between the first background light intensity image and the second background light intensity image. This indicates the difference between the first modulated light intensity image and the second modulated light intensity image. This represents the first background light intensity image. This represents the second background light intensity image. This represents the first modulated light intensity image. This represents the second modulated light intensity image. α The preset weight values.

17. The structured light imaging device as described in claim 14, characterized in that, It includes two of the aforementioned projection lighting devices, and the two projection lighting devices are symmetrically arranged with the imaging device as the center; The control device is also used to: when receiving an imaging command input by the user: Control one of the two projection lighting devices to perform structured light projection on the object being imaged in a projection mode corresponding to the imaging command, so as to perform three-dimensional reconstruction and obtain a first projection direction height image; Control the other of the two projection lighting devices to perform structured light projection on the object being imaged in a projection mode corresponding to the imaging command, so as to perform three-dimensional reconstruction and obtain a second projection direction height image; The height image of the first projection direction and the height image of the second projection direction are fused together to obtain the height image of the imaged object.

18. The structured light imaging device as described in claim 1, characterized in that, It includes at least one projection lighting combination, each projection lighting combination including two projection lighting devices, and the two projection lighting devices in each projection lighting combination are symmetrically arranged with respect to the imaging device.

Images