A multi-path projection device, three-dimensional measurement system and method

Abstract

The application discloses a multi-light-path projection device, a three-dimensional measurement system and a method, and relates to the field of three-dimensional measurement technology.The multi-light-path projection device comprises a uniform light source module, which is used for emitting a collimated light source with uniform light field distribution containing multiple colors; a light source modulation module, which is used for modulating the light source emitted by the uniform light source module, so that the light source contains a set projection pattern and the light source is decomposed into two beams of polarized light with different phases, and the two beams of polarized light are subjected to time sequence control; and a projection module, which comprises a plurality of pairs of projection outlets, each of which is used for projecting a light source with a single polarization state, the light sources projected by each pair of projection outlets are of the same color and different polarization states; and the positions of all the projection outlets are matched with each other, so that the areas projected by all the projection outlets are coincident.The light path structure of the projector is matched with the time sequence control of the light source and the reflective microcrystal projection chip, so that high-overlapping, multi-directional projection and real-time output of three-dimensional point cloud information and two-dimensional color images can be realized.

Description

Technical Field

[0001] The present invention relates to the field of optical projection technology, and in particular to a multi-light path projection device, a three-dimensional measurement system and a method. Background Art

[0002] Non-contact optical 3D measurement technology can be divided into active and passive types. In active measurement, the structured light projection measurement system primarily consists of a camera and a projector. The projector primarily projects a phase-shift pattern, while the camera primarily captures the phase-shift pattern modulated by the object's surface. Objects at different heights cause different phase changes. By extracting the phase information from the phase-shift pattern captured by the camera through an algorithm, the object under test can be reconstructed in three dimensions. After reconstruction, various 3D topographic information of the object under test can be obtained. Based on the 3D reconstruction results, 3D measurements of target parameters can be obtained according to specific measurement requirements. Existing structured light projection measurement systems primarily consist of a single camera and a single projector, resulting in numerous blind spots. They can only output 3D point cloud information on the object's surface and are unable to output 2D color images in real time. Measurement systems utilizing multiple projectors are simply a simple superposition of multiple projectors, resulting in problems such as low overlap in projection areas and a single projection wavelength.

[0003] Existing structured light projection measurement systems primarily consist of a single camera and a single projector. They use a computer to generate a fringe pattern, which is projected onto the surface of the object being measured via an optical projection system (projector). Objects at different heights cause different phase shifts in the fringe pattern. The camera captures the distorted fringe image modulated by the object's surface, and an algorithm extracts the phase information from the distorted fringe intensity map, enabling a three-dimensional reconstruction of the object being measured. Chinese patent CN113252685A utilizes multiple projectors to build a measurement system. However, this system is simply a simple overlay of multiple projectors, resulting in low overlap in projection areas, a single projection wavelength, complex setup, and the need for a white light source outside the projector. Chinese patent CN217113031U proposes a projection optical structure based on an LCOS imaging chip. This utilizes the LCOS imaging chip in conjunction with a polarizing element for projection, enabling simultaneous use of both S- and P-polarized light. However, this only addresses the use of multiple polarizations and lacks further design in the projection method, making it impossible to eliminate blind spots in measurement by combining multiple projection ports.

[0004] In summary, the main deficiencies of the prior art are as follows:

[0005] (1) The existing structured light projection measurement system mainly consists of a single camera and a single projector. There are many blind spots in the measurement. It can only output three-dimensional point cloud information of the object surface and cannot output two-dimensional color images in real time.

[0006] (2) The existing multi-projection system is simply a superposition of multiple projectors, which has problems such as low overlap of projection areas, single projection wavelength, complex device, and the need for white light source illumination outside the projector. Summary of the Invention

[0007] The present invention provides a multi-light-path projection device, a three-dimensional measurement system, and a method, which can solve at least one of the above-mentioned technical problems.

[0008] To achieve the above objectives, the present invention proposes the following technical solutions:

[0009] A multi-light path projection device, comprising:

[0010] A uniform light source module is used to emit a collimated light source with a uniform distribution of light fields containing multiple colors;

[0011] A light source modulation module, used to modulate the light source emitted by the uniform light source module so that the light source is decomposed into two beams of polarized light with different phases and containing a set projection pattern;

[0012] The projection module receives the light modulated by the light source modulation module and projects it onto the object to be measured. It includes several pairs of projection outlets, each of which is used to project a light source with a single polarization state. The light sources projected by each pair of projection outlets have the same color but different polarization states. The positions of the various projection outlets are coordinated with each other so that the projection areas of all projection outlets overlap.

[0013] Furthermore, the uniform light source module includes:

[0014] A plurality of light sources emitting light of different colors, wherein a collimating optical element is provided in front of each light source to adjust the light emitted by the light source into collimated light;

[0015] A light source beam combining device, used to combine collimated light sources of different colors into one light source;

[0016] The uniform optical component is used to homogenize the light beam of the combined light source to obtain a collimated light source with uniform light field distribution containing multiple colors.

[0017] Furthermore, the lights of different colors are red, green and blue lights; and the light source beam combining device is an X-shaped beam combining prism.

[0018] Furthermore, the light source modulation module includes:

[0019] A first polarization splitter is used to split the light emitted by the uniform light source module into two beams of polarized light with different phases: S-polarized light and P-polarized light; the S-polarized light and P-polarized light are respectively irradiated onto corresponding LCOS chips;

[0020] The LCOS chip is configured to reflect and modulate the S-polarized light and P-polarized light incident thereon so that the reflected light source includes a predetermined projection pattern; the modulation further comprising: converting the S-polarized light into P-polarized light after reflection, and converting the P-polarized light into S-polarized light after reflection;

[0021] The two polarized lights reflected by the LCOS chip are reflected back along the original light path and enter the first polarization beam splitting device, merged into one light source and enter the projection module through the imaging lens.

[0022] Furthermore, the projection module includes:

[0023] A second polarization splitting device, used for separating the two polarized light beams emitted by the light source modulation module;

[0024] The optical path separation device is used to separate each polarized light beam according to its color, so that the separated light sources of different colors reach different projection outlets;

[0025] A reflector, disposed between the light path separation device and the projection outlet, is used to change the direction of the light and adjust the direction of the projection pattern contained in the light source;

[0026] There are several pairs of projection outlets, each pair of projection outlets projects light sources of the same color but different polarization states; the positions of the projection outlets are coordinated with each other, and then the reflectors are adjusted so that the projection areas of all projection outlets overlap.

[0027] Furthermore, the optical path separation device is a dichroic plate or a dichroic prism, which reflects light with a relatively shorter wavelength and transmits light with a relatively longer wavelength, thereby separating each beam of polarized light according to the color of the light.

[0028] Furthermore, the first polarization beam splitting device and the second polarization beam splitting device are polarization beam splitting prisms or polarization beam splitting plates;

[0029] A plurality of reflectors are provided between the light source modulation module and the projection module, and are used to change the direction of the light source modulated by the light source modulation module.

[0030] On the other hand, the present invention also provides a three-dimensional measurement system, comprising:

[0031] The multi-light path projection device mentioned above;

[0032] One or more cameras, used to acquire the image projected onto the object to be measured by the multi-light-path projection device;

[0033] The host computer is connected to the multi-light path projection device, and is used to control the LCOS chip to reflect the set projection pattern and perform timing control on the uniform light source module; the host computer is connected to the camera, and is used to control the camera to shoot and receive the image acquired by the camera for three-dimensional measurement.

[0034] In another aspect, the present invention further provides a three-dimensional measurement method, comprising:

[0035] Set fringe patterns with different spatial frequencies and phases;

[0036] The multi-light path projection device projects the stripe patterns of different colors onto the object to be measured;

[0037] One or more cameras acquire images of the stripe patterns of different colors projected onto the object to be measured;

[0038] The object to be measured is reconstructed in three dimensions based on the image acquired by the camera, and the three-dimensional measurement result is obtained based on the three-dimensional reconstruction model.

[0039] Furthermore, it also includes:

[0040] The multi-light path projection device alternately projects stripe-free pattern light sources of red, green and blue colors, so that the camera can obtain a two-dimensional color image of the surface of the object to be measured.

[0041] The beneficial effects of the present invention are:

[0042] (1) The light source is combined with a polarization beam splitter and an LCOS chip to achieve multi-wavelength, multi-polarization projection pattern output. The combination can achieve a variety of projection outputs. Traditional projector solutions require multiple sets of light sources and multiple sets of LCOS chips. Using multiple wavelengths for projection can obtain not only the three-dimensional point cloud information of the object surface, but also the two-dimensional color information of the object.

[0043] (2) By using polarization beam splitters and dichroic filters, projections of different wavelengths and polarizations can be emitted from different projection outlets. By designing the projection outlets, multi-directional projections with high overlap of projection areas can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a structural diagram of the multi-light path projection device of the present invention;

[0045] Figure 2 It is a projection effect diagram of a multi-light path projection device in an existing projection device;

[0046] Figure 3 This is a projection effect diagram of the multi-light path projection device of the present invention;

[0047] Figure 4is a fringe pattern used in the three-dimensional measurement method of the present invention;

[0048] Figure 5 It is a schematic diagram of the timing control of the LCOS chip in the three-dimensional measurement method of the present invention.

[0049] In the figure: 1-LED light source; 2-light source shaping and collimator; 3-X-shaped beam combining prism; 4-uniform optical component; 5-first polarization splitting device; 6-first LCOS chip; 7-second LCOS chip; 8-imaging lens; 9-second polarization splitting device; 10-dichroic filter; 11-reflector; 12-first projection outlet; 13-second projection outlet; 14-third projection outlet; 15-fourth projection outlet; 16-first projector; 17-second projector; A-projection overlapping area. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0051] This embodiment first provides a multi-light path projection device, such as Figure 1 Shown, including:

[0052] The uniform light source module includes: a light source composed of an LED light source 1 and a light source shaper and collimator 2, wherein the LED light source 1 emits light of different colors, and the light source shaper and collimator 2 adjusts the light emitted by the light source into collimated light. The light source beam combining device 3 is an X-shaped beam combining prism, which is used to combine collimated light sources of different colors into a beam of light. The uniform optical component 4 is used to homogenize the light beam of the combined light source to obtain a collimated light source with a uniform light field distribution containing multiple colors. LED light sources 1 of different wavelengths are emitted separately. Taking red, green and blue as an example, the three wavelengths of light sources are overlapped into a collimated light path after passing through the light source shaper and collimator 2 and the X-shaped beam combining prism 3, and then pass through the uniform optical component 4 to achieve homogenization of the light source. The color and number of the LED light sources 1 can be adjusted according to the actual usage scenario, and the light source can also use other non-LED monochromatic light sources. The light source beam combining device can also be adjusted to other types of light source beam combining devices according to the actual usage scenario.

[0053] The light source modulation module includes a first polarization splitter 5 for splitting the light emitted by the uniform light source module into two polarized beams of different phases: S-polarized light and P-polarized light. A first LCOS chip 6 and a second LCOS chip 7 are disposed on corresponding sides of the first polarization splitter 5, respectively for reflecting and modulating the P-polarized and S-polarized light incident thereon. Light emitted by the uniform light source module is then split into horizontally and vertically polarized light, namely, P-polarized light and S-polarized light, by the first polarization splitter 5. The first polarization splitter 5 reflects the S-polarized light in the light source and allows the P-polarized light to pass through, resulting in a 90° phase difference between the two polarized lights. When the transmitted light P polarization is incident on the first LCOS chip 6, the first LCOS chip 6 can convert the P polarization into S polarization. The transmitted P polarization is converted into S polarization by the first LCOS chip 6 and reflected out, and at the same time, the reflected S polarization contains the set projection pattern. The reflected S polarization enters the first polarization splitting device 5 again and is reflected into the imaging lens 8; similarly, the S polarization reflected by the first polarization splitting device 5 is converted into P polarization by the second LCOS chip 7 and reflected again by the first polarization splitting device 5, and finally transmitted into the imaging lens 8; after the light field modulated by the first LCOS chip 6 and the second LCOS chip 7 is emitted through the imaging lens 8, the emitted light field at this time contains three color wavelengths and two polarization states, and contains the set projection pattern.

[0054] The projection module includes a second polarization splitting device 9, which is used to separate the two beams of polarized light emitted by the light source modulation module; and an optical path separation device composed of a dichroic filter 10, which is used to separate the light of different colors in each beam of polarized light. The light field emitted by the light source modulation module enters the projection module, and is first split into two by the second polarization splitting device 9, and the P polarized light and the S polarized light are respectively projected in different directions; and both pass through the dichroic filter 10. After passing through the dichroic filter 10, short-wavelength light such as blue light is reflected, and long-wavelength light such as green light and red light is transmitted; the separated light of different colors passes through one or more reflectors 11 and reaches the corresponding projection outlets, which are the first projection outlet 12, the second projection outlet 13, the third projection outlet 14, and the fourth projection outlet 15. The projection outlets are arranged in pairs, and the light sources projected by each pair of projection outlets are the same color but different polarization states; the positions of the various projection outlets cooperate with each other so that the areas projected by all projection outlets overlap. As Figure 3 As shown, the light source passes through the second polarization splitter 9, and according to the above optical path structure, passes through the dichroic filter 10 and the reflector 11 and then is projected out from the four projection outlets. Figure 3 This is a plan view diagram. In actual application, it is a three-dimensional structure. The projection direction of the light source of each projection outlet is as follows: Figure 3 As shown in , the areas projected by the projection outlets overlap. The second polarization beam splitting device 9 is a polarization beam splitting prism or a polarization beam splitting plate.

[0055] The projection outlet in this embodiment is designed with a second polarization beam splitter 9 that corresponds to the first polarization beam splitter 5 to separate the two polarized light beams emitted by the light source modulation module, thereby simplifying the optical path and reducing the complexity of hardware design.

[0056] LCOS chips are often manufactured to sizes that meet actual usage requirements. For example, the resolution of a common 1080P LCOS chip is 1920*1080 pixels, which means that the image modulated by the LCOS chip is often a rectangular area. The measurement system using multiple projectors is simply a simple superposition of multiple projectors. The rectangles projected by mutually perpendicular projectors do not overlap. Figure 2 As shown, the overlapping portion of the rectangular areas projected by the first projector 16 and the second projector 17 is only the projection overlap area A; this system uses one or more reflectors 11 to ensure that the distance between each projection exit and the imaging lens 8 is equal, as shown in FIG. Figure 3 As shown, the rectangular pattern has the same direction at the four projection outlets, and each projection outlet can project it to the same position, thus achieving multi-directional projection with a high degree of overlap in projection area.

[0057] In the multi-light-path projection device of this embodiment, the first polarization beam splitter 5 is a polarization beam splitter prism or a polarization beam splitter plate. The dichroic filter 10 can be replaced with a dichroic prism. The dichroic filter 10 can also be set to reflect long-wavelength light and transmit short-wavelength light. The number of projection outlets in this embodiment can also be changed according to the actual use scenario. If only a single color of projection light is required, only two projection outlets can be retained. Alternatively, the light can be further separated by color so that each projection outlet projects monochromatic light, increasing the number of projection outlets to six.

[0058] Several reflectors are positioned between the light modulation module and the projection module to redirect the modulated light. This allows the projection unit to be positioned entirely below the light source, better meeting product development and protection requirements. By utilizing a spatial structure, with the light source located on the first level and the projection unit on the second level, connected by reflectors, the projector unit is reduced in size and less susceptible to external influences.

[0059] This embodiment then provides a three-dimensional measurement system, which is based on the above-mentioned multi-path projection device and adds one or more cameras to obtain the image projected by the multi-path projection device onto the object to be measured. If there is only one camera, the camera is located at the symmetrical center of several pairs of projection outlets; if there are multiple cameras, the multiple cameras are symmetrically distributed relative to the several pairs of projection outlets.

[0060] The three-dimensional measurement system of this embodiment also includes a host computer, which is connected to the above-mentioned multi-light path projection device, and is used to control the LCOS chip to reflect the corresponding projection pattern and perform timing control on the LED light source 1; the host computer is connected to the camera, and is used to control the camera to shoot and receive the images obtained by the camera for three-dimensional measurement.

[0061] Finally, this embodiment provides a three-dimensional measurement method based on the above three-dimensional measurement system.

[0062] like Figure 4 As shown, in the field of optical measurement, fringe projection profilometry is one of the commonly used three-dimensional measurement technologies. It uses a computer to generate a fringe pattern, which is projected onto the surface of the object to be measured through an optical projection system (projector). The phase changes of the fringe pattern caused by objects of different heights are different. Use a camera to collect the deformed fringe image after being modulated by the object surface, and extract the phase information in the distorted fringe intensity image through an algorithm to reconstruct the object to be measured in three dimensions. Among them, phase shift profilometry requires at least three phase-shifted fringe patterns to achieve high-precision phase measurement pixel by pixel. In order to correctly reconstruct the three-dimensional morphology, the phase needs to be unfolded. Common phase unfolding methods are divided into two categories: spatial phase unfolding and temporal phase unfolding. Among them, the multi-frequency time phase unfolding method usually uses three fringe patterns with different periodic frequencies to perform multi-frequency heterodyning to perform phase unfolding. The fringe image that needs to be projected in the multi-frequency heterodyning method used in this embodiment is as follows Figure 4 As shown in the nine figures, the patterns in different rows have different spatial frequencies (16Hz, 15Hz, and 12Hz), and the patterns in different columns have different phases (0, 2π / 3, and 4π / 3). These patterns are generated by the LCOS chip controlled by the host computer and projected onto the object under test.

[0063] The projection process is realized by controlling the LCOS chip through the host computer. The control method of the timing of the combination of LED and LCOS chip is as follows: Figure 5 As shown in the figure, "R", "G" and "B" represent the light sources of red, green and blue colors, LCOS6 and LCOS7 represent the first LCOS chip 6 and the second LCOS chip 7, a, b, c and d represent the first projection outlet 12, the second projection outlet 13, the third projection outlet 14 and the fourth projection outlet 15 respectively. The blue LED light source is lit first, that is, Figure 5 In the figure "B", the first LCOS chips 6 and 7 alternately project structured light patterns 1-9, the light field modulated by the first LCOS chip 6 is emitted from the first projection outlet 12, and the light field modulated by the second LCOS chip 7 is emitted from the fourth projection outlet 15; then, the green LED light source is turned on, i.e. Figure 5In the "G" in the image, the first LCOS chip 6 and the second LCOS chip 7 alternately project structured light patterns 1-9 again. The light field modulated by the first LCOS chip 6 is emitted from the second projection outlet 13, and the light field modulated by the second LCOS chip 7 is emitted from the third projection outlet 14. The camera, in conjunction with the above projection process, captures images of each projection pattern of each color projected onto the object to be measured and transmits the images to the host computer. The host computer performs a three-dimensional reconstruction of the object to be measured using a multi-frequency heterodyne method and performs three-dimensional measurement of the object's topography based on the reconstructed 3D object. Finally, the red, green, and blue LED light sources are each activated once, and the multi-light path projection device alternately projects stripe-free patterns of red, green, and blue, allowing the camera to capture a two-dimensional color image of the object's surface. By using the red, green, and blue colors and the demodulated patterns in the light sources, a two-dimensional color image of the object can be obtained. Existing structured light projection measurement systems are unable to capture both two-dimensional and two-dimensional color images of objects. The present invention, by designing light sources of different colors and combining them with LCOS chip modulation, can capture three-dimensional color images of objects.

[0064] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A multi-light path projection device, characterized in that: include: A uniform light source module is used to emit a collimated light source with a uniform distribution of light fields containing multiple colors; A light source modulation module, used to modulate the light source emitted by the uniform light source module so that the light source is decomposed into two beams of polarized light with different phases and containing a set projection pattern; The projection module receives the light source modulated by the light source modulation module and projects it onto the object to be measured; The projection module includes: A second polarization splitting device, used for separating the two polarized light beams emitted by the light source modulation module; The optical path separation device is used to separate each polarized light beam according to its color, so that the separated light sources of different colors reach different projection outlets; A reflector, disposed between the light path separation device and the projection outlet, is used to change the direction of the light and adjust the direction of the projection pattern contained in the light source; Several pairs of projection outlets are provided, each of which is used to project a light source with a single polarization state. The light sources projected by each pair of projection outlets have the same color but different polarization states. The positions of the projection outlets are coordinated with each other, and the reflectors are adjusted so that the projection areas of all projection outlets overlap.

2. The multi-light path projection device according to claim 1, wherein: The uniform light source module comprises: A plurality of light sources emitting light of different colors, wherein a collimating optical element is provided in front of each light source to adjust the light emitted by the light source into collimated light; A light source beam combining device, used to combine collimated light sources of different colors into one light source; The uniform optical component is used to homogenize the light beam of the combined light source to obtain a collimated light source with uniform light field distribution containing multiple colors.

3. The multi-light path projection device according to claim 2, wherein: The lights of different colors are red, green and blue lights; and the light source beam combining device is an X-shaped beam combining prism.

4. The multi-light path projection device according to claim 1, wherein: The light source modulation module includes: A first polarization splitter is used to split the light emitted by the uniform light source module into two beams of polarized light with different phases: S-polarized light and P-polarized light; the S-polarized light and P-polarized light are respectively irradiated onto corresponding LCOS chips; The LCOS chip is configured to reflect and modulate the S-polarized light and P-polarized light incident thereon so that the reflected light source includes a predetermined projection pattern; the modulation further comprising: converting the S-polarized light into P-polarized light after reflection, and converting the P-polarized light into S-polarized light after reflection; The two polarized lights reflected by the LCOS chip are reflected back along the original light path and enter the first polarization beam splitting device, merged into one light source and enter the projection module through the imaging lens.

5. The multi-light path projection device according to claim 4, characterized in that: The optical path separation device is a dichroic plate or a dichroic prism, which reflects light with a relatively shorter wavelength and transmits light with a relatively longer wavelength, thereby separating each beam of polarized light according to the color of the light.

6. The multi-light path projection device according to claim 5, characterized in that: The first polarization beam splitting device and the second polarization beam splitting device are polarization beam splitting prisms or polarization beam splitting plates; A plurality of reflectors are provided between the light source modulation module and the projection module for changing the direction of the light source modulated by the light source modulation module.

7. A three-dimensional measurement system, characterized in that: include: The multi-light-path projection device according to any one of claims 4 to 6; One or more cameras, used to acquire the image projected onto the object to be measured by the multi-light-path projection device; The host computer is connected to the multi-light path projection device, and is used to control the LCOS chip to reflect the set projection pattern and perform timing control on the uniform light source module; the host computer is connected to the camera, and is used to control the camera to shoot and receive the image acquired by the camera for three-dimensional measurement.

8. A three-dimensional measurement method, characterized in that: include: Set fringe patterns with different spatial frequencies and phases; The multi-light path projection device according to any one of claims 4 to 6 projects the stripe patterns of different colors onto the object to be measured; One or more cameras acquire images of the stripe patterns of different colors projected onto the object to be measured; The object to be measured is reconstructed in three dimensions based on the image acquired by the camera, and the three-dimensional measurement result is obtained based on the three-dimensional reconstruction model.

9. The three-dimensional measurement method according to claim 8, characterized in that: Also includes: The multi-light path projection device alternately projects stripe-free pattern light sources of red, green and blue colors, so that the camera can obtain a two-dimensional color image of the surface of the object to be measured.

Images