CN113589621B

CN113589621B - Structured light projector, camera module and electronic equipment

Info

Publication number: CN113589621B
Application number: CN202110806773.9A
Authority: CN
Inventors: 倪强; 韩江
Original assignee: Rockchip Electronics Co Ltd
Current assignee: Rockchip Electronics Co Ltd
Priority date: 2021-07-16
Filing date: 2021-07-16
Publication date: 2022-05-31
Anticipated expiration: 2041-07-16
Also published as: CN113589621A

Abstract

The invention provides a structured light projector, a camera module and an electronic device. The structured light projector includes: a light source for emitting light; the turning optical element is arranged on one side of the light source and is used for turning the light rays entering from the first port of the light source to the second port of the light source for emitting; the first diffraction optical element is arranged on one side of the turning optical element, which is far away from the light source, and is used for focusing and duplicating the light rays turned out from the turning optical element to form structured light. The structured light projector has a thinner thickness than the prior art.

Description

Structured light projector, camera module and electronic equipment

Technical Field

The present disclosure relates to optical assemblies, and particularly to a structured light projector, a camera module and an electronic device.

Background

The structured light projector is a key device of a 3D structured light module, and the projector in the market at present is mainly formed by stacking a light source, a collimating mirror and a Diffractive Optical Element (DOE), and since the several devices have a certain thickness, the total thickness of the stacked structured light projector usually exceeds 4 mm. However, the thinner and thinner consumer electronic products make the conventional structured light projector difficult to meet the requirement, and therefore, how to design a thinner structured light projector becomes one of the technical problems to be solved urgently by the related art.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a structured light projector, a camera module and an electronic device, which are used to solve the problem of excessive thickness of the structured light projector in the prior art.

To achieve the above and other related objects, a first aspect of the present invention provides a structured light projector comprising: a light source for emitting light; the turning optical element is arranged on one side of the light source and is used for turning the light rays entering from the first port of the light source to the second port of the light source for emitting; the first diffraction optical element is arranged on one side of the turning optical element, which is far away from the light source, and is used for focusing and duplicating the light rays turned out from the turning optical element to form structured light.

In an embodiment of the first aspect, the turning optical element is an oblique prism, and is configured to refract the light entering from the first port and turn the light out from the second port.

In an embodiment of the first aspect, angles between the side surface and the top surface and between the side surface and the bottom surface of the rhombic prism are 45 °, and the refractive index of the rhombic prism at the working wavelength is greater than 1.6.

In an embodiment of the first aspect, top and bottom surfaces of the rhombic prism are plated with antireflection films.

In an embodiment of the first aspect, the turning optical element has a first reflecting surface and a second reflecting surface that are parallel to each other, and the first reflecting surface and the second reflecting surface are used for turning the light entering from the first port of the turning optical element to the second port of the turning optical element and emitting the light.

In an embodiment of the first aspect, the light source is a vertical cavity surface emitting laser, and the vertical cavity surface emitting laser has a plurality of light emitting points thereon, and the light emitting points satisfy a pseudo-random distribution in a spatial distribution.

In an embodiment of the first aspect, the effective focal length of the first diffractive optical element is 2-7mm, and the order of speckle replication of the first diffractive optical element is greater than or equal to the order of 3 × 3.

In an embodiment of the first aspect, the structured light projector further comprises: and the second diffractive optical element is arranged on one side of the first diffractive optical element, which is far away from the turning optical element, and is used for copying the structured light and/or adjusting the light intensity distribution of the structured light.

A second aspect of the present invention provides a camera module, including: the structured light projector of any of the first aspect of the present invention for emitting structured light from a target object to produce a structured light pattern on the target object; the image collector is used for collecting the structured light pattern; and the image processor is in communication connection with the image collector and is used for processing the structured light pattern to obtain a depth image of the target object.

A third aspect of the present invention provides an electronic device including the camera module according to the second aspect of the present invention.

As described above, the structured light projector according to one or more embodiments of the present invention has the following advantageous effects:

the structured light projector comprises a turning optical element, and light rays emitted by the light source can be turned through the turning optical element, so that the thickness of the structured light projector is reduced under the condition that the effective focal length of the diffraction optical element is not changed.

Drawings

Fig. 1 is a schematic diagram of a structure of a structured light projector in the related art.

FIG. 2 is a schematic structural diagram of a structured light projector according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of an orthorhombic prism in an embodiment of the structured light projector according to the invention.

FIG. 4 is a schematic structural diagram of a structured light projector according to an embodiment of the present invention.

FIG. 5 is a schematic structural diagram of a structured light projector according to another embodiment of the present invention.

Description of the element reference numerals

1 structured light projector

11 light source

12 collimating mirror

13 diffractive optical element

2 structured light projector

21 light source

22 rhombic prism

23 first diffractive optical element

24 second diffractive optical element

251 first right-angle prism

252 second right-angle prism

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments of the present invention, belong to the protection scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the equipment or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

Referring to fig. 1, the structured light projector 1 in the related art is mainly formed by stacking a light source 11, a collimating mirror 12 and a Diffractive Optical Element (DOE) 13, and since the 3 devices have a certain thickness, the total thickness of the stacked structured light projector 1 usually exceeds 4 mm. However, the increasingly thinner dimensions of consumer electronics make the structured light projector 1 difficult to meet. To address this problem, the present invention provides a structured light projector including a turning optical element by which light emitted from a light source can be turned, thereby reducing the thickness of the structured light projector without changing the effective focal length of a diffractive optical element. The structured light projector of the present invention will be described in detail below with reference to specific embodiments.

Example one

Referring to fig. 2, a schematic structural diagram of a structured light projector 2 according to an embodiment of the present invention is shown, where the structured light projector 2 includes a light source 21, an oblique square prism 22 and a first diffractive optical element 23, in this embodiment, the turning optical element is the oblique square prism 22, and the oblique square prism 22 is disposed between the light source 21 and the first diffractive optical element 23.

The light source 21 is, for example, a laser or an array of lasers for emitting light. Optionally, the light source 21 further comprises a ceramic substrate.

The rhombic prism 22 is used for refracting the light entering from the first port and then turning the light out from the second port. The first port is a port of the rhombic prism 22 close to the light source 21, and the second port is a port of the rhombic prism 22 close to the first diffractive optical element 23. The turning refers to translating the light ray without changing its propagation direction.

The first diffractive optical element 23 is used to focus (collimate) and replicate the light rays that are turned out from the second port of the rhombic prism to form structured light, which when reaching the target object generates a structured light pattern on the surface of the target object.

In a specific application, the light emitted from the light source 21 is bent after passing through the rhombic prism 22, and the bent light passes through the first diffractive optical element 23 to form the structured light. Since the first diffractive optical element 23 has a certain effective focal length, and the structured light pattern generated on the surface of the target object is denser as the focal length of the first diffractive optical element 23 is larger, the 3D imaging effect on the target object is better. Based on this, the structured light projector 2 according to the present embodiment innovatively introduces the rhombic prism 22, so as to achieve a great reduction in the thickness of the structured light projector 2 on the premise that the effective focal length of the first diffractive optical element 23 is not changed by turning the light. Practical measurements have shown that the introduction of the rhombic prisms 22 in the present embodiment enables the structured light projector 2 to have a thickness of less than 3.5 mm.

In addition, in the present embodiment, by introducing the rhombic prism 22 into the structured light projector 2, the optical path length of the light emitted from the light source 21 reaching the first diffractive optical element 23 is increased, and thus the first diffractive optical element 23 can perform a focusing (collimating) function well. Therefore, the structured light projector 2 of the present embodiment does not need to be provided with a collimating mirror, which is beneficial to further reducing the thickness of the structured light projector 2.

Alternatively, referring to fig. 3, the angle between the side surface and the top surface of the rhombic prism 22 is 45 °, and the angle between the side surface and the bottom surface of the rhombic prism 22 is also 45 °. In addition, the refractive index of the rhombic prism 22 at the operating wavelength in the present embodiment is larger than 1.6. At this time, the rhombic prism 22 can ensure that the light is totally reflected on the side surface without plating a reflective film, which is beneficial to simplifying the processing technology and the element complexity. Meanwhile, the rhombic prism 22 of the present embodiment can increase the optical path length of the light reaching the first diffractive optical element 23 without changing the direction of the light.

In a specific implementation, the material and size of the rhombic prism 22 may be selected according to the light emitting area and the single-point divergence angle of the light source 21. Specifically, if the total divergence angle of the light emitting point of the light source 21 is θ, if the side surface of the rhombic prism 22 needs to satisfy the total reflection of the incident light, the refractive index n of the rhombic prism 22 should satisfy:

in addition, the effective focal length of the first diffractive optical element 23 is related to the size and refractive index of the rhombic prism 22, and the material and size of the rhombic prism 22 can be selected according to the light emitting parameters of the light source 21 in specific applications.

In assembling, the first diffractive optical element 23 may be assembled as a whole before being assembled with the light source 21. Preferably, the module assembly with the light source 21 can be implemented by using an AA (Active Alignment) process to ensure the speckle effect of the final module.

It should be noted that the above-described rhombic prism 22 having the above-described configuration is only one preferable embodiment of the present invention, and other configurations may be adopted in practical applications. For example, if the light cannot be totally reflected at the side of the rhombic prism 22, a reflective film may be coated on the side of the rhombic prism 22 to ensure that the light cannot be transmitted at the side.

Optionally, the bottom surface and the top surface of the rhombic prism 22 are coated with antireflection films to reduce or even eliminate the reflected light from the bottom surface and the top surface of the rhombic prism 22, thereby increasing the light transmission amount thereof and reducing or even eliminating the influence of stray light.

Optionally, the light source 21 is an Edge Emitting Laser (EEL).

Optionally, the light source 21 is a Vertical Cavity Surface Emitting Laser (VCSEL) and a ceramic substrate, the VCSEL has a plurality of light Emitting points thereon, the number of the light Emitting points is, for example, greater than 100, and the light Emitting points satisfy a pseudo-random distribution in a spatial distribution.

Preferably, the wavelength of the light emitted by the light source 21 is 800-1000 nm.

Optionally, the effective focal length of the first diffractive optical element 23 is 2-7mm, and the order of speckle replication of the first diffractive optical element 23 is greater than or equal to 3 × 3, at which time the first diffractive optical element 23 can effectively replicate and focus (collimate) the light after turning.

Optionally, referring to fig. 4, the structured light projector 2 further comprises a second diffractive optical element 24. The second diffractive optical element 24 is disposed on a side of the first diffractive optical element 23 away from the rhombic prism 22, and is configured to replicate the structured light and/or adjust the light intensity distribution of the structured light.

Preferably, the structured light formed by the first diffractive optical element 23 is stripe-structured light, the light intensity of the stripe is a flat-top distribution in the long side direction, the light intensity uniformity ((Imax-Imin)/Mean) is less than or equal to 30%, and/or the light intensity of any stripe in the stripe-structured light is a gaussian-like light intensity distribution or a flat-top distribution in the short side direction, which can be realized by customizing the first diffractive optical element 23.

As can be seen from the above description, the structured light projector 2 of the present embodiment can reproduce the structured light through the second diffractive optical element 24, so as to generate a larger number of structured light patterns on the target object. Compared with the related art, the structured light projector 2 of the present embodiment has the advantages of simple structure, low cost, small volume, and suitability for mass production.

Optionally, in this embodiment, the light source 21 is a horizontal cavity surface emitting laser, the horizontal cavity surface emitting laser is an addressable array laser, and the structured light projector 2 further includes a light source controller, where the light source controller is connected to the horizontal cavity surface emitting laser and is configured to control a light emitting point of the horizontal cavity surface emitting laser and intensity of laser emitted by the horizontal cavity surface emitting laser, so as to implement phase shift and/or light emitting timing control of the structured light.

For example, the light source controller may be configured to control a light emitting timing of each light emitting point in the horizontal cavity surface emitting laser to implement timing coding of the structured light. Specifically, the light source controller controls the light emitting sequence of different light emitting points, so that the surface of the target object has different structured light patterns at different moments, and an image obtained after three-dimensional reconstruction based on the structured light patterns has higher precision.

For another example, the light source controller may control a current value of each light emitting point in the horizontal cavity surface emitting laser to realize conversion of light intensity in a test space, thereby realizing phase shift of the structured light.

As can be seen from the above description, the structured light projector 2 may further include a light source controller, which can implement phase shift and/or light emitting timing control of the structured light, so as to obtain a more accurate 3D image.

Example two

Fig. 5 is a schematic structural diagram of a structured light projector 2 according to a second embodiment of the invention. The present embodiment is different from the first embodiment in that the turning optical elements are right-

angle prisms

251 and 252 disposed opposite to each other and spaced apart from each other. The right-angle prism 251 has a first reflection surface, the right-angle prism 252 has a second reflection surface, the first reflection surface and the second reflection surface are parallel to each other, and the inclination angles of the first reflection surface and the second reflection surface with respect to the light source 21 and the first diffractive optical element 23 can be set according to actual requirements, for example, 45 °. In this embodiment, the light enters the turning optical element from the first port, is reflected by the first reflecting surface and reaches the second reflecting surface, and is turned by the second port after being reflected again by the second reflecting surface. Wherein the turning can make the light ray generate translation without changing the propagation direction of the light ray.

Alternatively, the first reflecting surface is implemented by plating a high reflective film on the side surface of the right-angle prism 251, and the second reflecting surface is implemented by plating a high reflective film on the side surface of the right-angle prism 252.

Optionally, the first diffractive optical element 23 is glued to the bottom surfaces of the right-

angle prisms

251 and 252, so that the thickness of the whole module is further reduced, which is beneficial to improving the integrity of the module.

In this embodiment, the right-

angle prisms

251 and 252 can also function to increase the optical path, so that the effective focal length of the first diffractive optical element 23 is larger, and the speckle density is higher.

It should be noted that the alternatives in the first embodiment are also applicable to the present embodiment, and redundant description is not repeated here for saving the description space. In addition, the present embodiment has been described only by taking the

rectangular prisms

251 and 252 as an example, but the present invention is not limited thereto, and any optical element having a first reflective surface and a second reflective surface that are parallel to each other and can realize turning of light can be applied to the present invention.

Based on the above description of the structured light projector 2, the present invention also provides a camera module. The camera module comprises a structured light projector shown in fig. 2, 4 or 5, and comprises an image collector and an image processor. Wherein the structured light projector is to emit structured light towards a target object to produce a structured light pattern, such as speckles or stripes, on the target object. The image collector is used for collecting the structured light pattern, and the image processor is in communication connection with the image collector and used for processing the structured light pattern to obtain a depth image of the target object.

Based on the above description of the structured light projector, the invention further provides an electronic device, which includes the camera module of the invention.

In view of the problem that the thickness of the conventional structured light projector is difficult to meet the requirements of ultra-thin electronic devices, one or more embodiments of the present invention provide a structured light projector that includes a turning optical element by which light emitted from a light source can be turned, thereby reducing the thickness of the structured light projector without changing the effective focal length of a diffractive optical element.

In addition, in one or more embodiments of the present invention, by introducing the turning optical element into the structured light projector, the optical path length of the light emitted from the light source reaching the diffractive optical element is increased, so that the diffractive optical element can better perform the focusing (collimating) function. Therefore, the structured light projector does not need to be provided with a collimating mirror, which is beneficial to further reducing the thickness of the structured light projector 2.

Moreover, in this embodiment, the turning optical elements may be implemented by right-angle prisms that are oppositely disposed and spaced from each other, and at this time, the first diffractive optical element may be glued to the bottom surface of the right-angle prism, which is beneficial to further reducing the thickness of the structured light projector.

In conclusion, the present invention effectively overcomes various disadvantages of the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A structured light projector, comprising:

a light source for emitting light;

the turning optical element is arranged on one side of the light source and is used for turning the light rays entering from the first port of the turning optical element to the second port of the turning optical element for emitting the light rays;

a first diffractive optical element disposed on a side of the turning optical element away from the light source for focusing and replicating the light turned out from the turning optical element to form structured light,

wherein the first diffractive optical element has an effective focal length of 2mm to 7mm and a speckle replication order of the first diffractive optical element is greater than or equal to 3 x 3 orders, and/or

The structured light projector also comprises a second diffraction optical element which is arranged on one side of the first diffraction optical element far away from the turning optical element and is used for copying the structured light and/or adjusting the light intensity distribution of the structured light.

2. The structured light projector of claim 1 wherein: the turning optical element is an oblique square prism and is used for refracting the light entering from the first port of the turning optical element and then turning the light out from the second port of the turning optical element.

3. The structured light projector of claim 2 wherein: the angles between the side surface and the top surface and between the side surface and the bottom surface of the rhombic prism are both 45 degrees, and the refractive index of the rhombic prism at the working wavelength is larger than 1.6.

4. The structured light projector of claim 3 wherein: and the top surface and the bottom surface of the rhombic prism are plated with antireflection films.

5. The structured light projector of claim 1 wherein: the turning optical element is provided with a first reflecting surface and a second reflecting surface which are parallel to each other, and the first reflecting surface and the second reflecting surface are used for turning the light rays entering from the first port of the turning optical element to the second port of the turning optical element to be emitted.

6. The structured light projector of any one of claims 1 to 5 wherein: the light source is a vertical cavity surface emitting laser, the vertical cavity surface emitting laser is provided with a plurality of light emitting points, and the light emitting points meet pseudo-random distribution in spatial distribution.

7. The utility model provides a camera module which characterized in that, camera module includes:

the structured light projector of any one of claims 1 to 6 for emitting structured light toward a target object to produce a structured light pattern on the target object;

the image collector is used for collecting the structured light pattern;

and the image processor is in communication connection with the image collector and is used for processing the structured light pattern to obtain a depth image of the target object.

8. An electronic device, characterized in that: the electronic device comprises the camera module of claim 7.