CN111123537A

CN111123537A - Light projection module and image acquisition system and three-dimensional sensing system having the same

Info

Publication number: CN111123537A
Application number: CN201811295124.1A
Authority: CN
Inventors: 苑京立; 朱庆峰; 田克汉; 尹晓东; 张国伟; 蒋超; 杨兴朋
Original assignee: Beijing Theto Optical Science And Technology Development Co ltd
Current assignee: Beijing Theto Optical Science And Technology Development Co ltd
Priority date: 2018-11-01
Filing date: 2018-11-01
Publication date: 2020-05-08

Abstract

The present application discloses a light projection module, an image acquisition system and a three-dimensional sensing system including the same, wherein the light projection module includes a light source and an optical device, wherein the optical device receives the light from the light source, and forms a Structured light field and flood light field superimposed on each other. A light projection module capable of both structured light pattern projection and flood lighting, which can realize structured light field and uniform background illumination light field at the same time. The projected light field pattern, power and contrast are controllable, which is conducive to the integration and small size of the system. ization and cost reduction.

Description

Light projection module and image acquisition system and three-dimensional sensing system with same

Technical Field

The present invention relates generally to three-dimensional sensing technology, and in particular, to a light projection module applicable to three-dimensional sensing, an image acquisition system having the same, and a three-dimensional sensing system.

Background

The structured light three-dimensional sensing technology is more and more widely applied to the fields of consumer electronics, robots, logistics, industrial detection and the like. In the traditional three-dimensional sensing technology, a structured light field and a floodlight field are separately used, image acquisition is carried out under the two light fields respectively, and information processing is carried out based on different images obtained thereby.

In addition, the existing structured light projection module and the existing floodlighting projection module respectively adopt different light sources and optical devices to form separate components, and the two are combined for use in the application of the three-dimensional sensing technology, so that the problems of low system integration level, large volume, high cost and the like are caused.

Disclosure of Invention

The invention aims to provide a light projection module, an image acquisition system with the light projection module and a three-dimensional sensing system with the light projection module, wherein a structured light projection function and a floodlight illumination light field projection function are integrated, the system integration level is improved, the structure miniaturization is facilitated, and the cost is reduced.

According to one aspect of the invention, there is provided a light projection module comprising a light source and an optical device, wherein the optical device receives light from the light source and forms a structured light field and a flood illumination light field superimposed on each other.

Advantageously, the ratio of the luminance of the flood illumination light field to the structured light field is in the range of 1:3 to 1:50, preferably in the range of 1:3 to 1: 9.

In some advantageous embodiments, the optical device is a diffractive optical element, i.e., a DOE, and the ratio of the brightness of the structured light field formed by the diffractive optical element to the brightness of the uniform background light formed by the diffractive optical element transmitting the stray light is in the range of 3:1 to 50:1, preferably in the range of 3:1 to 9:1, and more preferably in the range of 4:1 to 8: 1.

The optical device may include a first optical region having first optical microstructures for forming a structured light field and a second optical region having second optical microstructures for forming a flood illumination light field. Preferably, the optical device is a diffractive optical element, i.e. a DOE. Preferably, the optical device is integrally formed.

The first optical zone may comprise a plurality of sub-zones arranged in an array, and the second optical zone at least partially surrounds the plurality of sub-zones.

In some embodiments, light from the same light source impinges on both the first optical area and the second optical area.

In other embodiments, the light source may include a first light source that illuminates the first optical zone and a second light source different from the first light source that illuminates the second optical zone.

Alternatively, the optical device may comprise a first optical region having first optical microstructures for forming a structured light field and a second optical region having at least one lens for forming a flood illuminated light field.

The at least one lens may comprise a microlens array.

The light projection module can further comprise a shell, the light source and the optical device are installed in the shell, and the inner wall of the shell is made of white diffuse reflection materials.

According to another aspect of the present invention, there is provided an image acquisition system comprising the light projection module as described above, and a camera for acquiring images of an object under illumination by the structured light field and the flood illumination light field superimposed on each other projected by the light projection module. Preferably, the camera is an infrared camera.

According to another aspect of the present invention, there is provided a three-dimensional sensing system, comprising: the light projection module as described above; the camera is used for collecting images of an object irradiated by the structured light field and the floodlight field which are projected by the light projection module and are superposed with each other; and a calculation unit which receives the image acquired by the camera and acquires three-dimensional information of the object based on the image.

According to the embodiment of the invention, the light projection module can simultaneously realize the structured light field and the uniform background illumination field, and the projected light field has controllable pattern, power and contrast, thereby being beneficial to the integration and miniaturization of the system and reducing the cost.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 schematically illustrates the structure of a light projection module and its projected light field according to an embodiment of the invention;

FIG. 2 is a schematic block diagram of a three-dimensional sensing system according to an embodiment of the invention;

FIG. 3 is a schematic view of a light projection module according to a first embodiment of the present invention;

FIGS. 4A and 4B illustrate examples of optics that may be used with the light projection module of FIG. 3;

FIG. 5 is a schematic view of a light projection module according to a second embodiment of the present invention;

FIGS. 6A and 6B illustrate examples of optics that may be used with the light projection module of FIG. 5;

FIG. 7 is a schematic view of a light projection module according to a third embodiment of the present invention;

FIG. 8 illustrates an example of an optical device that may be used in the light projection module of FIG. 7;

FIG. 9 is a schematic view of a light projection module according to a fourth embodiment of the present invention; and

fig. 10A, 10B, and 10C illustrate examples of optical devices that may be used in the light projection module shown in fig. 9.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Fig. 1 schematically illustrates the structure of a light projection module 10 and a light field projected thereby according to an embodiment of the present invention. As shown, the light projection module 10 includes a light source 11, optics 12, and optionally a housing 13 for mounting/housing the light source 11 and the optics 12. The optical device 12 receives light from the light source 11 and forms a structured light field LF1 and a flood illumination light field LF2 superimposed on each other.

In some advantageous embodiments, the light source 11 may be an infrared light source; accordingly, the light projection module 10 projects a structured light field of infrared light and a flood light field of illumination light. The inventor of the invention finds that in some application scenes, the image of the face acquired under the simultaneous irradiation of the infrared structured light field and the floodlight illumination field can be more effectively used for acquiring the three-dimensional information of the face and carrying out face recognition. Of course, this may also be applied to detecting and identifying other objects.

In fig. 1, the structured light field LF1 is shown as a speckle light field, but this is merely exemplary and not limiting. Those skilled in the art will understand that the light projection module 10 according to the embodiment of the present invention can also project structured light field with other patterns, such as light spots, stripes, other patterns with specific shapes or position relationships, or any combination thereof; the invention is not limited in the particular form of the structured light field. The structured light field may be realized, for example, by optics that diffract light, for example, by Diffractive Optical Elements (DOEs), grating arrays.

A flood illumination field refers to a field of light that substantially uniformly illuminates a target area. The flood illumination light field can be realized by increasing the illumination angle of light through a lens, and can also be realized through a light homogenizing device, such as a micro-lens array or a DOE with a light homogenizing function.

The light source is preferably a Laser light source, for example, a Laser Diode (LD), a Vertical-Cavity Surface-Emitting Laser (VCSEL), or the like can be used; in some embodiments, a Light Emitting Diode (LED) may be used, but if the coherence of Light is to be used, a collimating device is also required to be disposed on the outgoing Light path of the LED.

The structured light field and the flood light field provided by the light projection module according to the embodiment of the invention are superimposed on each other, but can be used to acquire different information of the object, respectively. In order to enable the two light fields to provide sufficient and effective illumination respectively and simultaneously not generate excessive noise for information expected to be acquired based on the other light field, the brightness ratio of the flood lighting light field and the structured light field projected by the light projection module is within the range of 1: 3-1: 50, preferably within the range of 1: 3-1: 9.

In some advantageous embodiments, the light projection module 10 may include a housing 13, and the housing 13 is preferably made of a white diffuse reflection inner wall material to improve the optical reflection efficiency of the inner wall, so that the light irradiated on the inner wall can be emitted through the optical element by reflection to form a certain floodlight effect.

Fig. 2 schematically illustrates a three-dimensional sensing system 200 according to an embodiment of the invention. As shown, the three-dimensional sensing system 200 includes a light projection module 10, a camera 20, and a calculation unit 30.

The light projection module 10 is a light projection module according to an embodiment of the present invention, and is configured to project a structured light field and a flood light field superimposed on each other. The camera 20 is used for collecting images of the object under the irradiation of the structured light field and the floodlight field which are superposed with each other and projected by the light projection module 10. The light projection module 10 and the camera 20 may constitute an image capturing system according to an embodiment of the present invention.

The calculation unit 30 receives the image captured by the camera 20 and acquires three-dimensional information based on the image. The calculation unit 30 may comprise a processor 31 and a memory 32, and the memory 32 may have stored thereon program instructions that, when executed by the processor 31, cause the processor 31 to process the image received by the calculation unit 30 to obtain the three-dimensional information. In some embodiments, execution of the program instructions may also cause the processor 31 to process to obtain information other than three-dimensional information.

The three-dimensional sensing system adopting the light projection module can be constructed into a monocular structured light system, a binocular structured light system or a multi-ocular structured light system by one, two or more cameras, and an independent floodlight module is not required to be used in the system. When the three-dimensional sensing system works, the structured light field and the floodlight field are projected at the same time, the image of the object is collected, the depth information can be obtained according to the structured light pattern image, the appearance information of the shot object can be obtained according to the floodlight image, and data with two kinds of information are formed.

According to the three-dimensional sensing system provided by the embodiment of the invention, based on the light projection module provided by the embodiment of the invention, a novel simplified three-dimensional sensing and object recognition algorithm and a using method of the three-dimensional sensing recognition system can be realized, the system calculation amount and the calculation time are reduced, and the operation efficiency is improved.

The light projection module 10 according to an embodiment of the present invention will be described in more detail with reference to fig. 3 to 10.

Fig. 3 is a schematic structural diagram of a light projection module 10A according to a first embodiment of the invention. As shown, the light projection module 10A includes first and second

light sources

11a and 11b, an optical device 12A, and a housing 13 for mounting the light sources and the optical device. The second light source 11b is different from the first light source 11 a. Here, "different" of the light sources means substantial differences in the types, parameters, and arrangement of the light sources, for example, the first light source 11a is an LD, the second light source 11b is an LED, or the first light source 11a is a VCSEL having a plurality of emission points arranged randomly, and the second light source 11b is a VCSEL having a plurality of emission points arranged in a regular array.

Fig. 4A and 4B illustrate examples of optics that may be used in the light projection module of fig. 3.

As shown in fig. 4A, the optical device 12A includes a first optical region 12A and a second optical region 12b, the first optical region 12A having first optical microstructures for forming a structured light field, the second optical region 12b having second optical microstructures for forming a flood-illuminated light field. According to the present embodiment, the first optical zone 12a and the second optical zone 12b are aligned with each other. In some embodiments, the first optical region 12a and the second optical region 12b may be formed on the same optical substrate. For example, the optical device 12A may be an integrally formed diffractive optical element, wherein the first optical region 12A and the second optical region 12b each have a different pattern of optical microstructures thereon, thereby essentially forming two different diffractive optical elements for providing a structured light field and an dodging light field, respectively. In other embodiments, the first optical zone 12a and the second optical zone 12b may be formed on separate optical substrates and spliced together. Furthermore, the optical microstructures, in particular the second optical microstructure for forming the flood-illuminated light field, are not limited to forming the optical microstructure pattern of the DOE element, but may also be other microstructures for homogenizing light by scattering and/or refraction, such as scattering-based homogenizers, microlens arrays, and the like.

The optical device 12A 'shown in fig. 4B is a variation of the optical device 12A shown in fig. 4A, wherein the optical device 12A' includes a third optical region 12c in addition to the first optical region 12A and the second optical region 12B. In the illustrated example, the third optical zone 12c surrounds the first and second

optical zones

12a, 12 b. In some examples, the third optical zone 12c may be an additional optical zone for providing a flood-illuminated light field. In other examples, third optical region 12c may also be a "blank" optical region for mounting optical device 12A', where no particular optical microstructures are formed.

According to the present embodiment, as shown in fig. 3, the first optical area 12a and the second optical area 12b are irradiated from the first light source 11a and the second light source 11b, respectively.

Fig. 5 is a schematic structural diagram of a light projection module 10B according to a second embodiment of the invention. The light projection module 10B according to the second embodiment of the present invention has substantially the same structure as the light projection module 10A according to the first embodiment of the present invention, except that only one light source, i.e., the light source 11, is included in the light projection module 10B for simultaneously illuminating the first and second optical areas on the optical device 12A to form the structured-light field and the flood-illumination light field superimposed on each other. In some advantageous embodiments, the light source 11 is a laser light source, such as a laser diode or a vertical cavity surface emitting laser; in other embodiments, the light source 11 is a light emitting diode, and the light projection module 10B further includes a collimating device for collimating light from the light emitting diode.

Compared to the light projection module according to the first embodiment of the present invention that employs different first and second light sources, the light projection module according to the present embodiment requires only one light source, advantageously reducing system power consumption. In addition, for the image acquisition system and the three-dimensional sensing system comprising the light projection module, only one projector needs to be controlled, so that the system structure and the working mode can be simplified, and the cost is further reduced.

The

optical devices

12A and 12A' described above with reference to fig. 4A and 4B may be applied to the light projection module 10B according to the second embodiment of the present invention, and will not be described herein again.

Fig. 6A and 6B illustrate further examples of optics that may be used in light projection module 10B. Fig. 6A shows an optical device 12B, and fig. 6B shows a modification of the optical device 12B, i.e., an optical device 12B'. Each of the

optics

12B and 12B 'includes a first optical area 12f and a second optical area 12g, the second optical area 12g at least partially surrounding the first optical area 12f, except that the first optical area 12f in the optics 12B' includes a plurality of partial sub-areas and the second optical area 12g at least partially surrounds the sub-areas. The plurality of sub-regions are preferably arranged in an array. In some advantageous embodiments, the first optical zone 12f has first optical microstructures for forming a structured-light field and the second optical zone 12g has second optical microstructures for forming a flood-light illumination light field. In some advantageous embodiments, the

optical devices

12B, 12B' are diffractive optical elements, i.e. DOEs.

When the

optical devices

12B, 12B 'are applied to the light projection module 10B shown in fig. 5, light from the same light source 11 can be irradiated onto the respective areas of the

optical devices

12B, 12B'.

Fig. 7 is a schematic structural diagram of a light projection module 10C according to a third embodiment of the invention. A light projection module 10C according to the third embodiment of the present invention has substantially the same structure as the light projection module 10B (see fig. 5) according to the second embodiment of the present invention, except mainly that a diffractive optical element having a uniform optical microstructure pattern is employed as the optical device 12C (hereinafter also referred to as "diffractive optical element 12C") in the light projection module 10C.

Fig. 8 is only a schematic representation of the diffractive optical element 12C, wherein the optical microstructure pattern is not shown. According to the present embodiment, the ratio of the luminance of the structured-light field formed by the diffractive optical element 12C to the luminance of the uniform background light formed by the diffractive optical element transmitting the stray light is in the range of 3:1 to 50:1, preferably in the range of 3:1 to 9:1, and more preferably in the range of 4:1 to 8:1, thereby providing flood lighting with the light amount portion of the transmitted, non-structured light.

Although it is common in the prior art to use Diffractive Optical Elements (DOEs) to form the structured-light field, and projecting the structured-light field (structured-light pattern) by the DOE is accompanied by background illumination caused by stray light, it should be noted that the prior art DOE designs strictly suppress such background illumination caused by stray light, and the background light brightness is usually controlled to be less than 1% of the structured light brightness, or even lower. There has been no suggestion in the prior art to provide a uniform and appropriately bright background light while providing both a structured-light field and a flood-illuminated field by controlling a DOE device.

Fig. 9 is a schematic structural view of a light projection module 10D according to a fourth embodiment of the present invention, and fig. 10A, 10B, and 10C illustrate examples of optical devices,

optical devices

12D, 12E, and 12F, that can be used in the light projection module 10D shown in fig. 9.

As shown in fig. 9 and 10, a light projection module 10D according to a fourth embodiment of the present invention is substantially the same as the

light projection modules

10B, 10C according to the second and third embodiments of the present invention except that the light projection module 10D employs an optical device including a first optical region having a first optical microstructure for forming a structured-light field and a second optical region having at least one lens for forming a flood-light illumination field at a central position of the optical device.

The optical device 12D shown in fig. 10A includes a first optical region 12k and a second optical region 12l, the second optical region 12l being located at a central position and including a refractive lens. The refractive lens may be either a convex or concave lens, provided that it is positioned relative to the light source 11 to spread the light from the light source to form a flood light.

The optic 12E shown in fig. 10B includes a first optical zone 12k and a centrally located second optical zone 12m, the second optical zone 12m including a fresnel lens for diverging light entering the fresnel lens to form flood illumination.

The optic 12F shown in fig. 10C includes a first optical zone 12k and a centrally located second optical zone 12n, the second optical zone 12n including a microlens array that produces a dodging effect on light impinging thereon, thereby forming flood illumination.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims

1. A light projection module, comprising a light source and an optical device, wherein the optical device receives light from the light source and forms a structured light field and a flood lighting light field superimposed on each other.

2 . The light projection module according to claim 1 , wherein the luminance ratio of the flood light field and the structured light field is in the range of 1:3～1:50, preferably 1:3～ in the range of 1:9.

3. The light projection module of claim 1, wherein the optical device is a diffractive optical element, namely DOE, and the brightness of the structured light field formed by the diffractive optical element is different from the stray light transmitted by the diffractive optical element. The ratio of the brightness of the formed uniform background light is in the range of 3:1 to 50:1, preferably in the range of 3:1 to 9:1, and more preferably in the range of 4:1 to 8:1.

4. The light projection module of claim 1 , wherein the optical device comprises a first optical region and a second optical region, the first optical region having a first optical microstructure for forming a structured light field structure, the second optical region has a second optical microstructure for forming a flood lighting light field.

5. The light projection module of claim 4, wherein the first optical area comprises a plurality of sub-areas arranged in an array, and the second optical area at least partially surrounds the plurality of sub-areas.

6. The light projection module of claim 4 or 5, wherein light from the same light source impinges on both the first optical zone and the second optical zone.

7. The light projection module of claim 4, wherein the light source comprises a first light source and a second light source different from the first light source, the first light source illuminates the first optical region, and the second light source The second optical zone is illuminated.

8. The light projection module of claim 4, wherein the optical device is a diffractive optical element, ie DOE.

9. The light projection module of claim 4, wherein the optics are integrally formed.

10. The light projection module of claim 1 , wherein the optical device comprises a first optical region and a second optical region, the first optical region having a first optical microstructure for forming a structured light field structure, the second optical region has at least one lens for forming a flood light field.

11. The light projection module of claim 10, wherein the at least one lens comprises a microlens array.

12. The light projection module according to any one of claims 1-11, further comprising a housing in which the light source and the optical device are installed, wherein the inner wall of the housing adopts white diffuse reflection material.

13. An image acquisition system, comprising:

The light projection module of any one of claims 1-12; and

The camera is used for collecting the image of the object illuminated by the superimposed structured light field and the flood lighting light field projected by the light projection module.

14. The image acquisition system of claim 13, wherein the light source of the light projection module is an infrared light source, and the camera is an infrared camera.

15. A three-dimensional sensing system, comprising:

The light projection module of any one of claims 1-12;

a camera, configured to capture an image of an object illuminated by the superimposed structured light field and the flood lighting light field projected by the light projection module; and

a computing unit, which receives an image captured by the camera, and acquires three-dimensional information of the object based on the image.