Structured light projection device and 3D measurement system

Abstract

The invention relates to a structured light projection device and a 3D measurement system. The projection device comprises a display part, an axis closing part and a projection part. The display part comprises at least two display modules. The display module is configured to generate at least one sine fringe image with periodic light intensity change and project the sine fringe image along a projection optical axis. The sinusoidal fringe images have different frequencies and / or phases. The projection optical axes of any two display modules are not overlapped. The axis combining part is configured to axially align the sine fringe images projected by the display modules to the first optical axis. The projection section is configured to project the sinusoidal fringe image of the first optical axis outward. Compared with the prior art, according to the scheme, mechanical motion is not generated, high repetition precision is achieved, multiple sine stripe images are subjected to axis combination accurately, and the requirement of commercial application is met.

Description

Technical Field

[0001] The present invention relates to the technical field of structured light measurement, and in particular to a structured light projection device and a 3D measurement system. Background Art

[0002] Fringe Projection Profilometry (FPP) is a structured light 3D measurement technology that projects a sinusoidal fringe image onto the surface of the object to be measured through a projection device, and then uses an image acquisition device to collect and analyze the reflected fringes on the surface of the object to be measured to obtain the 3D shape of the surface of the object to be measured. The use of projection methods with multiple frequencies and / or phases to project multiple sinusoidal fringe images onto the surface of the object to be measured can improve the measurement accuracy. Taking the two-frequency three-step phase shift method as an example, it is necessary to project 6 sinusoidal fringe images in succession, including 2 fringe frequencies, and each frequency includes 3 phases.

[0003] Multiple sinusoidal fringe images require multiple backlight sources and need to be projected along the same optical axis. In related technologies, mechanical motion is usually used to achieve the same axis of projection. However, mechanical motion is difficult to guarantee high repeatability in long-term use, and it is difficult to meet the repeatability requirements of structured light products for sinusoidal fringe images, which is not conducive to commercial applications. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a structured light projection device and a 3D measurement system to overcome the above problems or at least partially solve the above problems, and can accurately align and project multiple sinusoidal fringe images to meet the requirements of commercial applications.

[0005] A further object of the present invention is to reduce the intensity loss of the sinusoidal fringe image when it is on-axis and improve the efficiency of the projection device.

[0006] Yet another further object of the present invention is to increase the types of coincidable sinusoidal fringe images, thereby improving the measurement accuracy of the projection device and expanding the application scenarios of the projection device.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] A structured light projection device comprises a display part, an axis-combining part and a projection part.

[0009] The display unit includes at least two display modules. The display modules are configured to generate at least one sinusoidal fringe image with periodic light intensity variation and project it along its projection optical axis. Each of the sinusoidal fringe images has a different frequency and / or phase. The projection optical axes of any two of the display modules do not overlap. The axis-matching unit is configured to axially align the sinusoidal fringe images projected by each of the display modules to a first optical axis. The projection unit is configured to project the sinusoidal fringe image of the first optical axis outward.

[0010] Optionally, the axis combining portion includes at least one beam splitter, which is at least one of a semi-transparent and semi-reflective mirror, a dichroic mirror, a color combining prism and a polarization beam splitter.

[0011] Optionally, the axis-coupling portion includes a first dichroic mirror.

[0012] The display unit includes a first display module and a second display module.

[0013] The first projection light axis of the first display module overlaps with the first optical axis, and the first display module emits light of a first wavelength to form the sinusoidal fringe image. The second projection light axis of the second display module is perpendicular to the first optical axis, and the second display module emits light of a second wavelength to form the sinusoidal fringe image.

[0014] The first wavelength is not equal to the second wavelength. The first dichroic mirror is configured to have a transmittance greater than that of the second wavelength for the first wavelength, and a reflectance greater than that of the second wavelength for the first wavelength.

[0015] Optionally, the axis-coupling portion further includes a second dichroic mirror.

[0016] The display unit further includes a third display module. The third display module emits light of a third wavelength to form the sinusoidal fringe image. The third wavelength is not equal to the first wavelength and the second wavelength.

[0017] The third projection light axis of the third display module is parallel to the second projection light axis, and the second display module and the third display module are arranged at intervals in the direction of the first light axis. The second dichroic mirror is configured to have a transmittance greater than the third wavelength for the first wavelength and the second wavelength, and a reflectance less than the third wavelength for the first wavelength and the second wavelength.

[0018] Optionally, the third projection light axis of the third display module is parallel to the first projection light axis, and the first display module and the third display module are arranged at intervals in the direction of the second projection light axis. The second dichroic mirror is configured to have a transmittance greater than the third wavelength for the second wavelength, and a reflectance greater than the second wavelength for the third wavelength. The first dichroic mirror is also configured to have a transmittance greater than the third wavelength for the first wavelength, and a reflectance greater than the third wavelength for the first wavelength.

[0019] Optionally, the axis combining portion includes a first polarization beam splitter.

[0020] The display unit includes a fourth display module and a fifth display module.

[0021] The fourth projection light axis of the fourth display module overlaps with the first light axis, and the fourth display module emits light of a first polarization state to form the sinusoidal fringe image. The fifth projection light axis of the fifth display module is perpendicular to the first light axis, and the fifth display module emits light of a second polarization state to form the sinusoidal fringe image.

[0022] The first polarization state and the second polarization state are orthogonal. The first polarization beam splitter is configured to have a greater transmittance to the first polarization state than to the second polarization state, and a greater reflectivity to the second polarization state than to the first polarization state.

[0023] Optionally, the axis combining portion further includes a second polarization beam splitter and a polarization changer, and the polarization changer is located between the first polarization beam splitter and the second polarization beam splitter.

[0024] The display unit further includes a sixth display module. A sixth projection light axis of the sixth display module is parallel to the fifth projection light axis, and the fifth display module and the sixth display module are arranged at intervals in the direction of the first light axis.

[0025] The polarization converter is configured to convert the second polarization state into the first polarization state. The sixth display module emits light of the second polarization state to form the sinusoidal fringe image. The second polarization beam splitter is configured to have a transmittance greater than the second polarization state for the first polarization state, and a reflectance greater than the first polarization state for the second polarization state.

[0026] Optionally, the polarization converter is configured to convert the first polarization state into the second polarization state. The sixth display module emits light of the first polarization state to form the sinusoidal fringe image. The second polarization beam splitter is configured to have a transmittance greater than the first polarization state for the second polarization state, and a reflectance greater than the second polarization state for the first polarization state.

[0027] Optionally, the axis-combining portion includes a first color-combining prism.

[0028] The display portion includes a seventh display module, an eighth display module and a ninth display module.

[0029] The seventh projection light axis of the seventh display module overlaps with the first light axis, and the seventh display module emits light of a fourth wavelength to form the sinusoidal fringe image. The eighth projection light axis of the eighth display module is perpendicular to the first light axis, and the eighth display module emits light of a fifth wavelength to form the sinusoidal fringe image. The ninth display module is arranged opposite to the eighth display module, and the ninth display module emits light of a sixth wavelength to form the sinusoidal fringe image. The first color combining prism is located between the eighth display module and the ninth display module.

[0030] The fourth wavelength, the fifth wavelength and the sixth wavelength are not equal. The first color combining prism is configured to have a transmittance greater than that of the fifth wavelength and the sixth wavelength for the fourth wavelength, and a reflectance greater than that of the fifth wavelength and the sixth wavelength for the fourth wavelength.

[0031] Optionally, the display module includes a strip-shaped light-emitting area extending along a first direction and a stripe generating structure.

[0032] The stripe generation structure is covered on the front side of the stripe-shaped light-emitting area. The stripe generation structure is configured to transform the light emitted by the stripe-shaped light-emitting area into the sinusoidal stripe image, and the sinusoidal stripe image has periodic light intensity changes in the first direction.

[0033] The strip-shaped light-emitting areas are N in number and are arranged at intervals along a second direction. The second direction is perpendicular to the first direction. The N number is greater than or equal to 3.

[0034] The stripe generation structures in front of the stripe-shaped light-emitting areas of the same display module have the same frequency and different phases, and the phase difference between any two adjacent phases is 2π / N. The stripe generation structures of different display modules have different frequencies.

[0035] Optionally, a ratio of a length of the strip-shaped light-emitting area along the first direction to a width of the strip-shaped light-emitting area along the second direction is greater than or equal to 4.

[0036] The projection unit includes a first lens, and the first lens is configured to uniformly stretch the sinusoidal fringe image in a direction perpendicular to the first direction. The first lens is a cylindrical lens or a quasi-cylindrical lens.

[0037] On the other hand, the present invention further provides a 3D measurement system, comprising an image acquisition device and the above-mentioned projection device, wherein the angle between the projection light axis of the projection device and the incident light axis of the image acquisition device is not zero.

[0038] A structured light projection device of the present invention can generate a variety of sinusoidal fringe images by arranging a plurality of display modules in a display section. By arranging an axis combining section, each sinusoidal fringe image can be combined to a first optical axis, and then projected to the surface of the object to be measured through a projection section. When performing 3D measurement, it is only necessary to control each display module in a time series to sequentially project a plurality of sinusoidal fringe images with different frequencies and / or phases to the surface of the object to be measured, so as to realize multi-frequency and / or multi-phase measurement. Compared with the prior art, this solution does not generate mechanical motion, achieves a higher repeatability, realizes accurate combination of multiple sinusoidal fringe images, and meets the requirements of commercial applications.

[0039] Furthermore, the projection device of the present invention, by arranging at least one of a dichroic mirror, a polarization beam splitter or a color combining prism at the axis combining part, improves the intensity of the light distributed to the first optical axis and reduces the light loss when the axes are combined, thereby achieving the effect of improving the efficiency of the projection device and reducing the energy consumption and heat generation of the projection device.

[0040] Furthermore, the projection device of the present invention can increase the types of sinusoidal fringe images by providing multiple display modules, each display module providing multiple strip-shaped light-emitting areas, thereby achieving the purpose of improving the measurement accuracy of the projection device and expanding the application scenarios of the projection device.

[0041] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0043] Figure 1 is a schematic structural diagram of a projection device according to an embodiment of the present invention;

[0044] Figure 2 is a schematic structural diagram of a projection device including a dichroic mirror according to an embodiment of the present invention;

[0045] Figure 3 is a schematic structural diagram of a projection device including a dichroic mirror according to an embodiment of the present invention;

[0046] Figure 4is a schematic structural diagram of a projection device including a dichroic mirror according to an embodiment of the present invention;

[0047] Figure 5 is a schematic structural diagram of a projection device including a dichroic mirror according to an embodiment of the present invention;

[0048] Figure 6 is a schematic structural diagram of a projection device including a polarization beam splitter according to an embodiment of the present invention;

[0049] Figure 7 is a schematic structural diagram of a projection device including a color combining prism according to an embodiment of the present invention;

[0050] Figure 8 is a schematic structural diagram of a projection device including a color combining prism and a dichroic mirror according to an embodiment of the present invention;

[0051] Fig. 9 is a schematic structural diagram of a projection device including a semi-transparent and semi-reflective mirror according to an embodiment of the present invention;

[0052] Fig.10 is a schematic front view of a display module of a projection device according to an embodiment of the present invention;

[0053] Fig.11 is a schematic cross-sectional view of a display module of a projection device according to an embodiment of the present invention;

[0054] Fig.12a is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0055] Figure 12b is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0056] Fig.12c is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0057] Fig.13a is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0058] Fig.13b is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0059] Fig.13c is a schematic front view of a stripe generating structure of a projection device according to an embodiment of the present invention;

[0060] Fig.14is a wavelength-transmittance curve of a dichroic mirror of a projection device according to one embodiment of the present invention;

[0061] Fig.15 is a schematic structural diagram of a 3D measurement system according to an embodiment of the present invention;

[0062] Fig.16 is a schematic flow chart of a control method of a 3D measurement system according to an embodiment of the present invention.

[0063] List of Figure Numbers:

[0064] 100, 3D measurement system; 200, projection device; 202, projection light axis; 300, display unit; 320, display module; 322, stripe light emitting area; 324, stripe generating structure; 326, substrate; 341, first display module; 342, second display module; 343, third display module; 344, fourth display module; 345, fifth display module; 346, sixth display module; 347, seventh display module; 348, eighth display module; 349, ninth display module; 35 0, tenth display module; 360, collimating lens; 400, axis combining unit; 402, first optical axis; 410, beam splitter; 421, first dichroic mirror; 422, second dichroic mirror; 423, third dichroic mirror; 441, first polarization beam splitter; 442, second polarization beam splitter; 443, polarization changer; 462, first color combining prism; 482, semi-transparent and semi-reflective mirror; 500, projection unit; 521, first lens; 600, image acquisition device; 602, incident optical axis; 702, surface of the object to be measured. DETAILED DESCRIPTION

[0065] Refer to the following Figures 1 to 16 To describe the structured light projection device and 3D measurement system of the embodiment of the present invention. In the description of this embodiment, it should be understood that the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features, that is, include one or more of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. When a feature "includes or contains" one or some of the features it covers, unless otherwise specifically described, this indicates that other features are not excluded and may further include other features.

[0066] Unless otherwise clearly defined and limited, the terms "set", "install", "connect", "connect", "fix", "couple" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. A person skilled in the art should be able to understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0067] In addition, in the description of this embodiment, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. That is, in the description of this embodiment, the first feature being "above", "above", and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature being "below", "below", or "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0068] In the description of the present embodiment, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0069] Figure 1 is a schematic structural diagram of a projection device according to an embodiment of the present invention. Figure 1 As shown, and refer to Figures 2 to 16 , a structured light projection device 200. The projection device 200 includes a display unit 300, an axis-combining unit 400 and a projection unit 500.

[0070] The display unit 300 includes at least two display modules 320. The display modules 320 are configured to generate at least one sinusoidal fringe image with periodic light intensity variation and project it along its projection optical axis. Each sinusoidal fringe image has a different frequency and / or phase. The projection optical axes of any two display modules 320 do not overlap. The axis-matching unit 400 is configured to axially align the sinusoidal fringe images projected by each display module 320 to the first optical axis 402. The projection unit 500 is configured to project the sinusoidal fringe image of the first optical axis 402 outward.

[0071] The display module 320 is used to generate backlight stripes, that is, a sinusoidal stripe image with a one-dimensional light intensity distribution. The display module 320 can be provided with a light emitter (such as LED, OLED, LCD, MEMS, VCSEL, LD, etc.), and the light beam emitted by the light emitter can form a sinusoidal stripe image with periodic light intensity changes after being modulated by an optical element (such as a mask, an optical shaping piece, etc.). Each display module 320 has a projection light axis. The projection light axis can be the axis of symmetry of the optical system of the display module 320 or the central axis of the sinusoidal stripe image. The overlap of the two projection light axes means that they are on the same straight line and in the same direction so that the light beam can be projected into the incident end of the projection unit 500. If the two projection light axes are on the same straight line, but the projection directions are opposite, the two projection light axes do not overlap.

[0072] The display module 320 can form one or more sinusoidal fringe images, which is not limited at this time. The multiple sinusoidal fringe images of the multiple display modules 320 have different frequencies and / or phases. Exemplarily, one display module 320 in the display unit 300 can generate a sinusoidal fringe image with a period number of 16 (the period number of the sinusoidal fringe is inversely proportional to the frequency), and another display module 320 can generate a sinusoidal fringe image with a period number of 17. Or one display module 320 in the display unit 300 can generate a sinusoidal fringe image with a period number of 16 and an initial phase of 0, and another display module 320 can generate a sinusoidal fringe image with a period number of 16 but an initial phase of 2π / 3 (i.e., a phase deviation of 2π / 3).

[0073] Each display module 320 can be controlled independently, and each sinusoidal fringe image belonging to the same display module 320 can also be controlled independently. In this way, multiple sinusoidal fringe images can be lit up in sequence in time for projection.

[0074] The display modules 320 may be arranged adjacently or at intervals, and their projected optical axes may be spaced or at a certain angle. The axis combining unit 400 is used to axially align the sinusoidal fringe images of the display modules 320 to the first optical axis 402. The first optical axis 402 may be the exit optical axis of the axis combining unit 400 and the incident optical axis 602 of the projection unit 500. The axis combining unit 400 may be provided with optical elements such as a beam splitter, a beam splitter, and a reflector to achieve the purpose of axis combining.

[0075] The projection unit 500 is used to receive the sinusoidal fringe image of the first optical axis 402 and project it onto the surface 702 of the object to be measured. The projection unit 500 may also be provided with optical elements to improve the projection size and quality, such as stretching, collimation, and elimination of chromatic aberration, to meet measurement requirements.

[0076] It should be understood that the first optical axis 402 (ie, the incident optical axis 602 of the projection unit 500 ) may overlap or not overlap with the projection optical axis 202 of the projection device 200 , depending on the arrangement of the optical elements in the projection unit 500 .

[0077] The projection device 200 of the present invention can generate a variety of sinusoidal fringe images by providing a plurality of display modules 320 in the display unit 300. By providing an axis combining unit 400, each sinusoidal fringe image can be combined to the first optical axis 402, and then projected to the surface 702 of the object to be measured via the projection unit 500. When performing 3D measurement, it is only necessary to control each display module 320 in a time series to sequentially project a plurality of sinusoidal fringe images with different frequencies and / or phases to the surface 702 of the object to be measured, so as to achieve multi-frequency and / or multi-phase measurement. Compared with the prior art, the present technical solution does not generate mechanical motion, achieves a higher repeatability, and realizes accurate combination of multiple sinusoidal fringe images, thus meeting the requirements of commercial applications.

[0078] In some embodiments of the projection device of the present invention, such as Figure 2-9 As shown, the axis combining part 400 includes at least one beam splitter 410. The beam splitter 410 is at least one of a semi-transparent and semi-reflective mirror 482, a dichroic mirror, a color combining prism (x-cube), and a polarization beam splitter / polarization beam splitter prism.

[0079] The beam splitter 410 can conveniently and accurately adjust the propagation path of the light beam of each display module 320. It has a simple structure and a small size. When applied to the projection device 200, it can improve the repetitive accuracy of the sinusoidal fringe image projected onto the surface 702 of the object to be measured and reduce the size of the device.

[0080] In some embodiments of the projection device of the present invention, such as Figure 2 As shown, the axis combining portion 400 includes a first dichroic mirror 421 .

[0081] The display unit 300 includes a first display module 341 and a second display module 342. A first projection light axis (not shown in the figure) of the first display module 341 overlaps with a first optical axis 402, and the first display module 341 emits light of a first wavelength λ1 to form a sinusoidal fringe image. A second projection light axis (not shown in the figure) of the second display module 342 is perpendicular to the first optical axis 402, and the second display module 342 emits light of a second wavelength λ2 to form a sinusoidal fringe image.

[0082] The first wavelength λ1 is not equal to the second wavelength λ2. The first dichroic mirror 421 is configured to have a transmittance greater than that of the first wavelength λ1 and a reflectance greater than that of the second wavelength λ2.

[0083] The display module 320 can be configured to emit different wavelengths as needed. It should be understood that the first wavelength λ1 and the second wavelength λ2 indicate the central wavelengths of the corresponding display module 320. In actual use, the light beams of the display module 320 have a certain wavelength width (for example, tens of nanometers).

[0084] A dichroic mirror is an optical element coated with a film having selective transmittance (also called transmittance) for different wavelengths. In this embodiment, the light beams of the first display module 341 and the second display module 342 are incident on the opposite sides of the first dichroic mirror 421 at 45 degrees. The first dichroic mirror 421 has a high transmittance for the first wavelength λ1 and a high reflectivity for the second wavelength λ2. After the light beams of the first display module 341 and the second display module 342 pass through the first dichroic mirror 421, more light intensity is distributed to the first optical axis 402, and less light intensity is distributed to other directions, thereby achieving less light intensity loss.

[0085] See also Fig.14 . Fig.14 Where T1 is a wavelength-transmittance curve of the first dichroic mirror 421 of an embodiment. When the first wavelength λ1 is less than 480nm, the transmittance of the first dichroic mirror 421 to it is close to 100%, that is, there is almost no light intensity loss during transmission. When the second wavelength λ2 is greater than 510nm, the transmittance of the first dichroic mirror 421 to it is close to 0%, but the reflectivity is close to 100%, that is, there is almost no light intensity loss during reflection. Exemplarily, 450nm can be selected as the first wavelength λ1 and 550nm as the second wavelength λ2. In actual use, in the presence of wavelength width, the transmittance of the light beam of the first display module 341 can exceed 90%, and the reflectivity of the light beam of the second display module 342 can exceed 90%.

[0086] In this embodiment, by setting a first dichroic mirror 421 in the axis-coupling portion 400, the intensity of the light distributed to the first optical axis 402 can be increased and the light loss can be reduced when the axes are coaxial, thereby achieving the effect of improving the efficiency of the projection device 200 and reducing the energy consumption and heat generation of the projection device 200.

[0087] In some embodiments of the projection device of the present invention, such as Figure 3 As shown, the axis combining portion 400 further includes a second dichroic mirror 422 .

[0088] The display unit 300 further includes a third display module 343. The third display module 343 emits light of a third wavelength λ3 to form a sinusoidal fringe image. The third wavelength λ3 is not equal to the first wavelength λ1 and the second wavelength λ2.

[0089] The third projection light axis (not shown in the figure) of the third display module 343 is parallel to the second projection light axis, and the second display module 342 and the third display module 343 are arranged at intervals in the direction of the first optical axis 402. The second dichroic mirror 422 is configured such that the transmittance of the first wavelength λ1 and the second wavelength λ2 are both greater than the third wavelength λ3, and the reflectance of the first wavelength λ1 and the second wavelength λ2 are both less than the third wavelength λ3.

[0090] The third display module 343 can emit a light beam with a third wavelength λ3, and the third wavelength λ3 indicates the central wavelength of the display module 320. In actual use, the light beam of the display module 320 has a certain wavelength width (eg, tens of nanometers).

[0091] In this embodiment, the light beam of the first display module 341 passing through the first dichroic mirror 421, the light beam of the second display module 342 reflected by the first dichroic mirror 421, and the light beam emitted by the third display module 343 are all incident on the opposite surface of the second dichroic mirror 422 at 45 degrees. The second dichroic mirror 422 has a high transmittance for the first wavelength λ1 and the second wavelength λ2, and has a high reflectivity for the third wavelength λ3. After the light beams of the first display module 341, the second display module 342, and the third display module 343 pass through the second dichroic mirror 422, more light intensity is distributed to the first optical axis 402, and less light intensity is distributed to other directions, thereby achieving less light intensity loss.

[0092] See also Fig.14 . Fig.14 Where T1 is a wavelength-transmittance curve of the first dichroic mirror 421 of an embodiment, and T2 is a wavelength-transmittance curve of the second dichroic mirror 422 of an embodiment. When the first wavelength λ1 and the second wavelength λ2 are less than 580nm, the transmittance of the second dichroic mirror 422 to them is close to 100%, that is, there is almost no light intensity loss during transmission. When the third wavelength λ3 is greater than 610nm, the transmittance of the second dichroic mirror 422 to them is close to 0%, but the reflectivity is close to 100%, that is, there is almost no light intensity loss during reflection. Exemplarily, 450nm can be selected as the first wavelength λ1, 550nm as the second wavelength λ2, and 630nm as the third wavelength λ3. In actual use, in the presence of wavelength width, the transmittance of the light beams of the first display module 341 and the second display module 342 can exceed 90%, and the reflectivity of the light beam of the third display module 343 can exceed 90%.

[0093] In this embodiment, the number of display modules 320 is further increased, thereby increasing the types of sinusoidal fringe images, which can improve the measurement accuracy of the projection device 200 on the same type of surface 702 of the object to be measured, and can also be applied to different types of surfaces 702 of the object to be measured, thereby expanding the application scenarios of the projection device 200. By arranging a variety of dichroic mirrors in the axis-coupling portion 400, the intensity of the light distributed to the first optical axis 402 is increased when the axis is coaxial, and the light loss is reduced, thereby achieving the effect of improving the efficiency of the projection device 200 and reducing the energy consumption and heat generation of the projection device 200.

[0094] In some embodiments of the projection device of the present invention, such as Figure 4 As shown, the third projection light axis of the third display module 343 is parallel to the first projection light axis, and the first display module 341 and the third display module 343 are arranged at intervals in the direction of the second projection light axis. The second dichroic mirror 422 is configured to have a transmittance greater than the third wavelength λ3 for the second wavelength λ2, and a reflectance greater than the second wavelength λ2 for the third wavelength λ3. The first dichroic mirror 421 is also configured to have a transmittance greater than the third wavelength λ3 for the first wavelength λ1, and a reflectance greater than the first wavelength λ1 for the third wavelength λ3.

[0095] By selecting a dichroic mirror with a suitable transmittance curve, the coaxial part 400 of different structural forms can be freely realized. In this embodiment, by reasonably setting the wavelengths of the first display module 341, the second display module 342 and the third display module 343, and the transmittance curves of the first dichroic mirror 421 and the second dichroic mirror 422, the light beam of the first display module 341 efficiently passes through the first dichroic mirror 421, the light beam of the second display module 342 efficiently passes through the second dichroic mirror 422, and then is efficiently reflected by the first dichroic mirror 421, and the light beam of the second display module 342 is efficiently reflected by the second dichroic mirror 422 and the first dichroic mirror 421, and finally coaxially aligned to the first optical axis 402.

[0096] Compared with the previous embodiment, the projection device 200 of this embodiment can have different aspect ratios and sizes as a whole to adapt to different application scenarios. When used in an example, it can be set as needed.

[0097] In some embodiments of the projection device of the present invention, such as Figure 5As shown, the axis-coupling portion 400 further includes a third dichroic mirror 423. The display portion 300 further includes a tenth display module 350. The tenth display module 350 emits light of a seventh wavelength λ7 to form a sinusoidal fringe image. The seventh wavelength λ7 is not equal to the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3. The third dichroic mirror 423 is configured such that the transmittance of the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 is greater than the seventh wavelength λ7, and the reflectivity of the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 is less than the seventh wavelength λ7.

[0098] By selecting a dichroic mirror with a suitable transmittance curve, different structural forms of the coaxial part 400 can be freely realized. In this embodiment, the number of display modules 320 is further increased, thereby increasing the types of sinusoidal fringe images, achieving the purpose of improving the measurement accuracy of the projection device 200 and expanding the application scenarios of the projection device 200.

[0099] In some other embodiments of the projection device 200 of the present invention, the display unit 300 may be provided with more display modules 320, and the axis-coupling unit 400 may be provided with more dichroic mirrors to further increase the types of sinusoidal fringe images, thereby achieving the purpose of improving the measurement accuracy of the projection device 200 and expanding the application scenarios of the projection device 200.

[0100] In some embodiments of the projection device of the present invention, such as Figure 6 As shown, the axis-combining unit 400 includes a first polarization beam splitter 441. The display unit 300 includes a fourth display module 344 and a fifth display module 345. The fourth projection optical axis (not shown in the figure) of the fourth display module 344 overlaps with the first optical axis 402, and the fourth display module 344 emits light of a first polarization state to form a sinusoidal fringe image. The fifth projection optical axis (not shown in the figure) of the fifth display module 345 is perpendicular to the first optical axis 402, and the fifth display module 345 emits light of a second polarization state to form a sinusoidal fringe image.

[0101] The first polarization state and the second polarization state are orthogonal. The first polarization beam splitter 441 is configured such that the transmittance of the first polarization state is greater than that of the second polarization state, and the reflectivity of the second polarization state is greater than that of the first polarization state.

[0102] In this embodiment, the first polarization state and the second polarization state may be linear polarized light with perpendicular polarization directions, or may be left-handed and right-handed circular polarized light, respectively.

[0103] The polarization beam splitter is an optical element with selective transmittance for different polarization states. In this embodiment, the light beams of the fourth display module 344 and the fifth display module 345 are incident on the opposite side of the first polarization beam splitter 441 at 45 degrees. The first polarization beam splitter 441 has a high transmittance for the first polarization state and a high reflectivity for the second polarization state. After the light beams of the first display module 341 and the second display module 342 pass through the first polarization beam splitter 441, more light intensity is distributed to the first optical axis 402, and less light intensity is distributed to other directions, thereby achieving less light intensity loss, thereby achieving the effect of improving the efficiency of the projection device 200 and reducing the energy consumption and heat generation of the projection device 200.

[0104] The difference between this embodiment and the embodiment in which the axis is aligned by a dichroic mirror is that the embodiment does not need to set display modules 320 of multiple wavelengths, and each display module 320 can emit a light beam of the same wavelength. In this way, the types of parts can be reduced and the production cost can be reduced. The parameters of each optical element of the axis alignment part 400 and the projection part 500 can also be reasonably set according to the preset wavelength, so as to improve the efficiency and projection quality of the projection device 200. In actual use, the same model of display modules 320 can be used, and the corresponding polarizer can be set on the front side of the display module 320. Of course, different models of display modules 320 can also be used to directly emit light beams with orthogonal polarization states.

[0105] In some embodiments of the projection device of the present invention, such as Figure 6 As shown, the axis combining portion 400 further includes a second polarization beam splitter 442 and a polarization changer 443 . The polarization changer 443 is located between the first polarization beam splitter 441 and the second polarization beam splitter 442 .

[0106] The display unit 300 further includes a sixth display module 346. A sixth projection light axis (not shown) of the sixth display module 346 is parallel to the fifth projection light axis. The fifth display module 345 and the sixth display module 346 are arranged at intervals in the direction of the first light axis 402.

[0107] The polarization changer 443 is configured to convert the second polarization state into the first polarization state. The sixth display module 346 emits light of the second polarization state to form a sinusoidal fringe image. The second polarization beam splitter 442 is configured to have a greater transmittance to the first polarization state than to the second polarization state, and a greater reflectivity to the second polarization state than to the first polarization state.

[0108] The polarization changer 443 can be synchronously arranged with the fourth display module 344 and the fifth display module 345. When the fifth display module 345 emits a light beam in the second polarization state, the polarization changer 443 switches to a working state to convert the light beam passing therethrough from the second polarization state to the first polarization state. When the fourth display module 344 emits a light beam in the first polarization state, the polarization changer 443 switches its state to allow the light beam in the first polarization state to pass therethrough directly.

[0109] In this embodiment, by providing a polarization changer 443 and a plurality of polarization beam splitters in the coaxial portion 400, the number of display modules 320 is further increased, thereby increasing the types of sinusoidal fringe images, thereby achieving the purpose of improving the measurement accuracy of the projection device 200 and expanding the application scenarios of the projection device 200.

[0110] In some embodiments of the projection device of the present invention, the polarization changer 443 is configured to convert the first polarization state into the second polarization state. The sixth display module 346 emits light of the first polarization state to form a sinusoidal fringe image. The second polarization beam splitter 442 is configured to have a greater transmittance to the second polarization state than to the first polarization state, and a greater reflectivity to the first polarization state than to the second polarization state.

[0111] In some other embodiments of the projection device 200 of the present invention, the display unit 300 may be provided with more display modules 320, and the axis-coupling unit 400 may be provided with more vibration modulators and polarization beam splitters to further increase the types of sinusoidal fringe images, thereby achieving the purpose of improving the measurement accuracy of the projection device 200 and expanding the application scenarios of the projection device 200.

[0112] In some embodiments of the projection device of the present invention, such as Figure 7 As shown, the axis combining unit 400 includes a first color combining prism 462. The display unit 300 includes a seventh display module 347, an eighth display module 348 and a ninth display module 349. The seventh projection optical axis (not shown in the figure) of the seventh display module 347 overlaps with the first optical axis 402, and the seventh display module 347 emits light of a fourth wavelength λ4 to form a sinusoidal fringe image. The eighth projection optical axis (not shown in the figure) of the eighth display module 348 is perpendicular to the first optical axis 402, and the eighth display module 348 emits light of a fifth wavelength λ5 to form a sinusoidal fringe image. The ninth display module 349 is arranged opposite to the eighth display module 348, and the ninth display module 349 emits light of a sixth wavelength λ6 to form a sinusoidal fringe image. The first color combining prism 462 is located between the eighth display module 348 and the ninth display module 349.

[0113] The fourth wavelength λ4, the fifth wavelength λ5 and the sixth wavelength λ6 are not equal. The first color combining prism 462 is configured such that the transmittance of the fourth wavelength λ4 is greater than that of the fifth wavelength λ5 and the sixth wavelength λ6, and the reflectivity of the fifth wavelength λ5 and the sixth wavelength λ6 is greater than that of the fourth wavelength λ4.

[0114] A color-combining prism is usually an optical device composed of four right-angle prisms. On the ±45-degree diagonal planes, optical films are coated to selectively transmit light of different colors.

[0115] In this embodiment, the light beams emitted by the seventh display module 347, the eighth display module 348, and the ninth display module 349 are respectively incident on the color combining prism from three directions. The first color combining prism 462 has a high transmittance to the fourth wavelength λ4, and has a high reflectivity to the fifth wavelength λ5 and the sixth wavelength λ6. After the light beams of the first display module 341, the second display module 342, and the third display module 343 pass through the first color combining prism 462, more light intensity is distributed to the first optical axis 402, and less light intensity is distributed to other directions, thereby achieving less light intensity loss.

[0116] In this embodiment, the light beams emitted by the three display modules 320 are aligned by a color combining prism, which can greatly simplify the structure of the projection device 200 and reduce the volume of the projection device 200 .

[0117] In some embodiments of the projection device of the present invention, such as Figure 8 As shown, the axis-coupling portion 400 further includes a third dichroic mirror 423. The display portion 300 further includes a tenth display module 350. The tenth display module 350 emits light of a seventh wavelength λ7 to form a sinusoidal fringe image. The seventh display module 347, the eighth display module 348, and the ninth display module 349 respectively emit light of a fourth wavelength λ4, a fifth wavelength λ5, and a sixth wavelength λ6 to form a sinusoidal fringe image. The seventh wavelength λ7 is not equal to the fourth wavelength λ4, the fifth wavelength λ5, and the sixth wavelength λ6. The third dichroic mirror 423 is configured to have a transmittance greater than the seventh wavelength λ7 for the fourth wavelength λ4, the fifth wavelength λ5, and the sixth wavelength λ6, and a reflectance less than the seventh wavelength λ7 for the fourth wavelength λ4, the fifth wavelength λ5, and the sixth wavelength λ6.

[0118] In this embodiment, the color combining prism and the dichroic mirror are combined to further increase the number of display modules 320, thereby increasing the types of sinusoidal fringe images, thereby achieving the purpose of improving the measurement accuracy of the projection device 200 and expanding the application scenarios of the projection device 200.

[0119] In some embodiments of the projection device of the present invention, such as Fig. 9As shown, the axis-coupling portion 400 includes two semi-transparent and semi-reflective mirrors 482. The display portion 300 includes three first display modules 341. The first display module 341 emits light of a first wavelength λ1 to form a sinusoidal fringe image.

[0120] The semi-transparent and semi-reflective mirror 482 can split the incident light beam in a preset ratio. In this embodiment, by setting two semi-transparent and semi-reflective mirrors 482, the three-way light beam can be aligned. The semi-transparent and semi-reflective mirror 482 will lose a certain amount of light. By reasonably setting the transmission and reflection ratio of the semi-transparent and semi-reflective mirror 482, the light loss can be reduced. For example, Fig. 9 The transmission-reflection ratio of the semi-transparent and semi-reflective mirror 482 on the left side is set to 1:1. Fig. 9 The transmission-reflection ratio of the semi-transparent and semi-reflective mirror 482 on the middle right side is set to 2:1, so as to increase the ratio of the light beams emitted by the three first display modules 341 that converge to the first optical axis 402 .

[0121] In this embodiment, by setting a semi-transparent and semi-reflective mirror 482, the light beams of multiple display modules 320 with exactly the same wavelength and polarization state can be combined. The structure is simple and the cost is low. It is suitable for low-power application scenarios or application scenarios that are not sensitive to heat.

[0122] It should be understood that in other embodiments of the projection device of the present invention, the alignment of different light paths can be achieved by freely combining one or more of the semi-transparent and semi-reflective mirror 482, the dichroic mirror, the color combining prism and the polarization beam splitter. Ordinary beam splitters or beam splitting prisms can be used to replace the semi-transparent and semi-reflective mirror 482, which will not be described in detail here.

[0123] In some embodiments of the projection device of the present invention, such as Figure 2-9 As shown, the display module 320 is further provided with a collimating lens 360 to improve the quality of the light beam emitted by the display module 320 .

[0124] In some embodiments of the projection device of the present invention, such as Figure 10-11 As shown, the display module 320 includes a strip-shaped light-emitting area 322 extending along a first direction and a stripe generating structure 324. The stripe generating structure 324 is covered on the front side of the strip-shaped light-emitting area 322. The stripe generating structure 324 is configured to form a sinusoidal stripe image with periodic light intensity changes in the first direction from the light emitted by the strip-shaped light-emitting area 322. The strip-shaped light-emitting area 322 is N in number and arranged at intervals along a second direction. The second direction is perpendicular to the first direction. N is greater than or equal to 3.

[0125] The stripe generation structures 324 in front of the stripe light emitting areas 322 of the same display module 320 have the same frequency and different phases, and the phase difference between any two adjacent phases is 2π / N. The stripe generation structures 324 of different display modules 320 have different frequencies.

[0126] The display module 320 may be provided with a substrate 326, and each strip-shaped light-emitting area 322 is arranged on the substrate 326 along an array. The strip-shaped light-emitting area 322 may be composed of light emitters such as LED, OLED, LCD, MEMS, VCSEL, LD, etc., for forming a one-dimensional linear backlight strip. An optical film / uniform light film may also be provided in front of the strip-shaped light-emitting area 322 to improve the direction and uniformity of the light beam of the strip-shaped light-emitting area 322. The stripe generating structure 324 may be a mask, an optical shaping sheet, etc., for generating a sinusoidal stripe image with periodic light intensity changes in the linear backlight strip. An optical isolation structure may be provided between each strip-shaped light-emitting area 322 to reduce or eliminate the crosstalk between different strip-shaped light-emitting areas 322 and improve the projection quality. Each strip-shaped light-emitting area 322 is configured to be independently controlled to realize light emission and extinguishing.

[0127] Although the stripe generating structures 324 on the front side of each stripe luminous area 322 of the same display module 320 may have different frequencies and different phases, the current manufacturing process has high requirements and may affect the projection quality. In this embodiment, the stripe generating structures 324 on the front side of each stripe luminous area 322 of the same display module 320 have the same frequency and different phases, which can improve the accuracy of the phase. Different display modules 320 are set to have different frequencies, thereby realizing multi-frequency multi-step phase shift projection.

[0128] Due to the different light intensities, reflectivities and positions, for the sinusoidal fringe images of the same frequency, at least three phases need to be set to dephase, thereby obtaining the 3D shape of the surface 702 of the object to be measured. Therefore, in this embodiment, three or more strip-shaped light-emitting areas 322 are spaced apart along the second direction.

[0129] For example, the projection device 200 is provided with three display modules 320, each display module 320 is provided with three strip-shaped light-emitting areas 322, and the phase difference of the stripe generating structures 324 of adjacent strip-shaped light-emitting areas 322 is 120 degrees. In this way, the projection device 200 can realize three-frequency three-step phase shift projection.

[0130] See also Figure 12a-12c . Figure 12a-12c The middle stripe generating structure 324 is a transmittance mask. The mask pattern in the figure is a grayscale image. Different grayscales represent different transmittances, thereby achieving spatial variation in the amount of light transmitted and generating the required light intensity distribution. Figure 12a-12c The three masks in each figure have the same frequency but have initial phase differences of 0 degrees, 120 degrees, and 240 degrees, respectively. Fig.12a , Figure 12b and Fig.12c The frequency of the mask is different.

[0131] See also Figures 13a-13c . Figures 13a-13c The middle stripe generation structure 324 is a binary mask. In the binary mask, each point in the space has only two states: light-transmitting and light-impermeable. The required light transmission can be achieved by controlling the length of the light-transmitting structure in the direction perpendicular to the long axis of the strip backlight to produce the required light intensity distribution. Figures 13a-13c The three masks in each figure have the same frequency but have initial phase differences of 0 degrees, 120 degrees, and 240 degrees, respectively. Fig.13a , Fig.13b and Fig.13c The frequency of the mask is different.

[0132] The fringe generating structure 324 may be an optical shaping sheet, which may directly modulate the outgoing light of the light source to form a required light intensity distribution on the intermediate image plane.

[0133] In some embodiments of the projection device of the present invention, such as Fig.10 As shown, the ratio L1 / W1 of the length L1 of the strip-shaped light-emitting area 322 along the first direction to the width W1 along the second direction is greater than or equal to 4.

[0134] The projection unit 500 includes a first lens 521, and the first lens 521 is configured to uniformly stretch the sinusoidal fringe image in a direction perpendicular to the first direction. The first lens 521 is a cylindrical lens or a quasi-cylindrical lens.

[0135] In this embodiment, the strip-shaped light-emitting area 322 has a larger aspect ratio to form a sinusoidal fringe image with a larger number of cycles (displaying more sinusoidal fringes on the same projection area), thereby increasing the frequency of the sinusoidal fringe image projected by the display module 320 and improving the measurement accuracy. The volume of the display module 320 can also be reduced, thereby reducing the volume and cost of the projection device 200.

[0136] Since the length and width of a single strip-shaped light-emitting area 322 are relatively large, in order to project an image with approximately the same length and width, a first lens 521 is provided in the projection unit 500. The first lens 521 may be a cylindrical lens or a quasi-cylindrical lens, and is used to converge light in the stripe spacing direction of the sinusoidal stripes (corresponding to the first direction of the strip-shaped light-emitting area 322), so that the projected image maintains a one-dimensional luminous flux distribution similar to the sinusoidal stripe image in this direction. In the direction perpendicular to it, that is, the stripe extension direction (corresponding to the second direction of the strip-shaped light-emitting area 322), the first lens 521 diverges the light, thereby generating stretched stripes.

[0137] Please refer to Figure 2-3 . Figure 2In the vertical direction which is the stripe spacing direction of the sinusoidal stripes (corresponding to the first direction of the strip-shaped light-emitting area 322), the first lens 521 converges the light in the vertical direction, so that the projected image maintains a one-dimensional luminous flux distribution similar to that of the sinusoidal stripe image in this direction. Figure 3 The up-down direction is the extension direction of the sinusoidal stripes (corresponding to the second direction of the strip-shaped light-emitting area 322 ), and the first lens 521 diverges the light in the up-down direction, thereby generating stretched stripes.

[0138] In this embodiment, by setting a larger aspect ratio in the strip-shaped light-emitting area 322 and cooperating with the first lens 521 , the number of periods of the sinusoidal fringe image can be increased, thereby improving the measurement accuracy.

[0139] In some embodiments of the projection device of the present invention, the ratio L1 / W1 of the length L1 of the strip light emitting area 322 along the first direction to the width W1 along the second direction is greater than or equal to 10, so as to further increase the number of cycles of the sinusoidal fringe image and thereby improve the measurement accuracy.

[0140] In some embodiments of the projection device of the present invention, the first lens 521 is a free-form surface or a super lens, so as to converge the light in one direction and diverge the light in a direction perpendicular to it.

[0141] In some embodiments of the projection device of the present invention, a second lens is further provided. The second lens may be a spherical or aspherical lens, and is used to improve the projection quality, such as eliminating chromatic aberration.

[0142] In some embodiments of the 3D measurement system of the present invention, Fig.15 As shown, the 3D measurement system 100 includes an image acquisition device 600 and a projection device 200 of any one of the above embodiments or a combination of embodiments. The angle α between the projection optical axis 202 of the projection device 200 and the incident optical axis 602 of the image acquisition device 600 is not zero.

[0143] The image acquisition device 600 may be a camera, a video camera, etc. It is used to acquire each sinusoidal fringe image projected by the projection device 200 on the surface 702 of the object to be measured. The image acquisition device 600 may also perform phase separation on the sinusoidal fringe image to obtain the measurement result of the surface 702 of the object to be measured. Alternatively, the image acquisition device 600 may also be connected to a computing device, and the computing device may process the acquired data to obtain the measurement result of the surface 702 of the object to be measured.

[0144] An angle α (eg, 45 degrees) is formed between the incident light axis 602 of the image acquisition device 600 and the projection light axis 202 of the projection device 200, so that the sinusoidal fringe image reflected by the surface 702 of the object to be measured can be acquired, and the 3D shape of the surface 702 of the object to be measured can be obtained through the deformation of the fringe.

[0145] In some embodiments of the 3D measurement system of the present invention, the measurement system may be used as follows Fig.16 The control directions shown are for image projection and acquisition.

[0146] S8100, start;

[0147] S8111, the first strip-shaped light-emitting area of ​​the first display module emits light;

[0148] S8112, the image acquisition device acquires images;

[0149] S8113, the first strip-shaped light-emitting area of ​​the first display module is turned off;

[0150] S8121, the second strip-shaped light-emitting area of ​​the first display module emits light;

[0151] …

[0152] S8341, the fourth strip-shaped light-emitting area of ​​the third display module emits light;

[0153] S8342, the image acquisition device acquires an image;

[0154] S8343, the fourth strip-shaped light-emitting area of ​​the third display module is turned off;

[0155] S8400, end.

[0156] In this way, a total of 12 sinusoidal fringe images with three frequencies and four phases can be projected onto the surface of the object to be measured in time series. After passing through the image acquisition device, the 3D shape of the surface of the object to be measured can be obtained through calculation and analysis.

[0157] At this point, those skilled in the art should recognize that, although multiple exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all these other variations or modifications.

Claims

1. A structured light projection device, characterized in that: include: A display unit, comprising at least two display modules; The display module is configured to generate at least one sinusoidal fringe image with periodic light intensity variation and project it along its projection optical axis; Each of the sinusoidal fringe images has a different frequency and / or phase; the projection light axes of any two of the display modules do not overlap; an axis aligning portion, configured to axially align the sinusoidal fringe images projected by each of the display modules to a first optical axis; The projection unit is configured to project the sinusoidal fringe image of the first optical axis outward.

2. The projection device according to claim 1, characterized in that: The axis combining part includes at least one beam splitter; the beam splitter is at least one of a semi-transparent and semi-reflective mirror, a dichroic mirror, a color combining prism and a polarization beam splitter.

3. The projection device according to claim 1, characterized in that: The axis combining portion includes a first dichroic mirror; The display unit includes: a first display module, wherein a first projection light axis of the first display module overlaps with the first light axis, and the first display module emits light of a first wavelength to form the sinusoidal fringe image; a second display module, wherein a second projection light axis of the second display module is perpendicular to the first light axis, and the second display module emits light of a second wavelength to form the sinusoidal fringe image; The first wavelength is not equal to the second wavelength; the first dichroic mirror is configured to have a transmittance greater than the second wavelength for the first wavelength, and a reflectance greater than the first wavelength for the second wavelength.

4. The projection device according to claim 3, characterized in that: The axis combining portion further includes a second dichroic mirror; The display unit further includes a third display module; the third display module emits light of a third wavelength to form the sinusoidal fringe image; the third wavelength is not equal to the first wavelength and the second wavelength; The third projection light axis of the third display module is parallel to the second projection light axis, and the second display module and the third display module are arranged at intervals in the direction of the first light axis; the second dichroic mirror is configured to have a transmittance greater than the third wavelength for the first wavelength and the second wavelength, and a reflectance less than the third wavelength for the first wavelength and the second wavelength; or The third projection light axis of the third display module is parallel to the first projection light axis, and the first display module and the third display module are arranged at intervals in the direction of the second projection light axis; the second dichroic mirror is configured to have a transmittance greater than the third wavelength for the second wavelength, and a reflectivity greater than the second wavelength for the third wavelength; the first dichroic mirror is also configured to have a transmittance greater than the third wavelength for the first wavelength, and a reflectivity greater than the third wavelength for the third wavelength.

5. The projection device according to claim 1, characterized in that: The axis combining portion includes a first polarization beam splitter; The display unit includes: a fourth display module, wherein a fourth projection optical axis of the fourth display module overlaps with the first optical axis, and the fourth display module emits light of a first polarization state to form the sinusoidal fringe image; A fifth display module, wherein a fifth projection optical axis of the fifth display module is perpendicular to the first optical axis, and the fifth display module emits light of a second polarization state to form the sinusoidal fringe image; wherein the first polarization state and the second polarization state are orthogonal; and the first polarization beam splitter is configured such that the transmittance of the first polarization state is greater than that of the second polarization state, and the reflectivity of the second polarization state is greater than that of the first polarization state.

6. The projection device according to claim 5, characterized in that: The axis combining part further includes a second polarization beam splitter and a polarization changer, wherein the polarization changer is located between the first polarization beam splitter and the second polarization beam splitter; The display unit further includes a sixth display module; a sixth projection light axis of the sixth display module is parallel to the fifth projection light axis, and the fifth display module and the sixth display module are arranged at intervals in the direction of the first light axis; The polarization changer is configured to convert the second polarization state into the first polarization state; The sixth display module emits light of the second polarization state to form the sinusoidal fringe image; the second polarization beam splitter is configured to have a transmittance greater than that of the first polarization state and a reflectance greater than that of the second polarization state; or The polarization converter is configured to convert the first polarization state into the second polarization state; the sixth display module emits light of the first polarization state to form the sinusoidal fringe image; the second polarization beam splitter is configured to have a transmittance of the second polarization state greater than the first polarization state, and a reflectivity of the first polarization state greater than the second polarization state.

7. The projection device according to claim 1, characterized in that: The axis combining portion includes a first color combining prism; The display unit includes: a seventh display module, wherein a seventh projection optical axis of the seventh display module overlaps with the first optical axis, and the seventh display module emits light of a fourth wavelength to form the sinusoidal fringe image; an eighth display module, wherein an eighth projection optical axis of the eighth display module is perpendicular to the first optical axis, and the eighth display module emits light of a fifth wavelength to form the sinusoidal fringe image; a ninth display module, the ninth display module being arranged opposite to the eighth display module, the ninth display module emitting light of a sixth wavelength to form the sinusoidal fringe image; the first color combining prism being located between the eighth display module and the ninth display module; Among them, the fourth wavelength, the fifth wavelength and the sixth wavelength are not equal; the first color combining prism is configured to have a transmittance of the fourth wavelength greater than the fifth wavelength and the sixth wavelength, and a reflectivity of the fifth wavelength and the sixth wavelength greater than the fourth wavelength.

8. The projection device according to claim 1, characterized in that: The display module comprises: A strip-shaped light-emitting area extending along a first direction; a stripe generating structure, the stripe generating structure being covered on the front side of the stripe-shaped light-emitting area; the stripe generating structure being configured to transform the light emitted by the stripe-shaped light-emitting area into the sinusoidal stripe image, wherein the sinusoidal stripe image has a periodic light intensity variation in the first direction; The strip-shaped light-emitting areas are N in number and arranged at intervals along a second direction; the second direction is perpendicular to the first direction; and N is greater than or equal to 3; Among them, the stripe generating structures on the front side of the strip-shaped light-emitting areas belonging to the same display module have the same frequency and different phases, and the phase difference between any two adjacent phases is 2π / N; the stripe generating structures of different display modules have different frequencies.

9. The projection device according to claim 8, characterized in that: A ratio of the length of the strip-shaped light-emitting area along the first direction to the width of the strip-shaped light-emitting area along the second direction is greater than or equal to 4; The projection unit includes a first lens, and the first lens is configured to uniformly stretch the sinusoidal fringe image in a direction perpendicular to the first direction; the first lens is a cylindrical lens or a quasi-cylindrical lens.

10. A 3D measurement system, characterized in that: It comprises an image acquisition device and a projection device as claimed in any one of claims 1 to 9; the angle between the projection light axis of the projection device and the incident light axis of the image acquisition device is not zero.

Images