CN109579728B - Speckle structure light projection module based on holographic waveguide - Google Patents
Speckle structure light projection module based on holographic waveguide Download PDFInfo
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
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Abstract
The invention relates to the field of 3D topography measurement. The invention provides a speckle structure light projection module based on a holographic waveguide, which comprises a holographic waveguide unit, an array laser light source, a collimating lens and a diffraction optical element, wherein the holographic waveguide unit is composed of the holographic optical element and a waveguide substrate material. The holographic optical element is used as a coupling input and output modulation device, modulates a first spot pattern emitted by an array laser light source into total reflection waveguide transmission in a substrate, couples and outputs the total reflection waveguide transmission to a collimating lens after a certain distance, and the diffractive optical element receives collimated light beams, copies and expands the first spot pattern to form high-density speckle dot matrix illumination and projects the speckle dot matrix illumination to a scene to be measured. The laser array light source and other optical modulation devices can be separated by a certain distance in space by adopting a holographic waveguide transmission mode, so that a heat dissipation device is added for the light source, and the good heat dissipation characteristic is ensured while the light, thin and small design of the structure is realized.
Description
Technical Field
The invention relates to the field of 3D (three-dimensional) shape measurement, in particular to a speckle structure light projection module based on holographic waveguide.
Background
The 3D topography measurement technology can collect depth coordinate information of objects in a scene, and provides additional data processing freedom for back-end development. With the popularization of mobile terminal devices and intelligent interaction equipment, the 3D measurement technology becomes a new generation of core technology of human-computer interaction more and more, and has wide application prospects in the aspects of industrial detection, security retail, somatosensory games, mobile payment, biomedicine and the like.
Speckle structured light technology is a widely used 3D data acquisition scheme today. The method adopts spot light clusters which are randomly, pseudo-randomly or regularly arranged after being coded as optical probes to be projected to a space scene, and specific scene depth information is obtained by comparing spot displacement amounts through a triangulation principle. The projection module projects a preset structured light mode to an actual scene, and is a hardware basis of the speckle structured light depth camera. The module generally includes a laser light source, a collimating lens, and a Diffractive Optical Element (DOE).
As the application of depth sensing technology in mobile devices is becoming more widespread, the demands on the size of the projection module and the depth camera are becoming higher and higher. Compact and thin projection modules and depth cameras become urgent research requirements in the field; in addition, because the installation and the arrangement of each element in the miniaturized projection module are compact, the miniaturized projection module can face the problem of light source heat dissipation, and the development of the speckle projection module is severely restricted.
In summary, in the speckle structured light 3D topography measurement, how to design a speckle projection module with a light and thin structure and a small size, which is also convenient for heat dissipation of a light source, becomes one of the current technical problems to be solved.
Disclosure of Invention
The embodiment of the invention aims to provide a speckle structure light projection module based on holographic waveguide, so that the speckle projection module can meet the light, thin and small design of the structure and has good heat dissipation property.
In order to achieve the above object, an aspect of the embodiments of the present invention provides a speckle structure light projection module based on a holographic waveguide, including a holographic waveguide unit and an array light source for emitting a laser beam corresponding to a first speckle pattern, where the holographic waveguide unit includes a waveguide substrate, a first holographic optical element and a second holographic optical element, the first holographic optical element is attached to a first end of the waveguide substrate, and the second holographic optical element is attached to a second end of the waveguide substrate; the second holographic optical element is used for coupling the laser beams emitted by the array light source into the waveguide substrate, and the laser beams can be subjected to waveguide transmission in the waveguide substrate and output through the first holographic optical element.
The embodiment of the invention provides a speckle structure light projection module based on a holographic waveguide, which comprises a holographic waveguide unit and an array light source, wherein the array light source is used for emitting laser beams corresponding to a first speckle pattern; wherein a plane of the waveguide substrate at the second end is cut into an inclined plane to couple a laser beam to be waveguide-transmitted through the inclined plane so that the laser beam can be waveguide-transmitted in the waveguide substrate and output through the first holographic optical element.
According to the technical scheme, the holographic waveguide unit and the array light source are arranged in the speckle structure light projection module, the holographic waveguide unit comprises a waveguide substrate, a first holographic optical element and a second holographic optical element, and in terms of position arrangement, the laser beams emitted by the array light source are coupled in through the second holographic optical element at one end and can be subjected to waveguide transmission in the waveguide substrate to be output through the first holographic optical element at the other end of the waveguide substrate. Therefore, the light source can be separated from other optical modulation devices by a long distance through waveguide transmission, and a heat dissipation device can be added to the light source independently, so that the light and thin miniaturized light-emitting diode can have good heat dissipation characteristics while the light and thin-type miniaturized light-emitting diode is designed.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a schematic structural diagram of a speckle structured light projection module based on a holographic waveguide according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a speckle structured light projection module based on a holographic waveguide according to a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a speckle-structured light projection module based on a holographic waveguide and configured with a holographic lens for coupling out according to a second embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a speckle structured light projection module based on holographic waveguide configured with compound HOE coupling-out according to a third embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a speckle-structured light projection module based on a holographic waveguide and configured with a holographic lens coupling-in and a holographic grating coupling-out according to a fourth embodiment of the present invention;
FIG. 6A is a schematic structural diagram of a speckle structured light projection module based on holographic waveguide configured with tilted surface coupling input according to a first embodiment of the present invention;
FIG. 6B is a schematic structural diagram of a speckle structured light projection module based on holographic waveguide configured with tilted surface coupling input according to a second embodiment of the present invention;
fig. 6C is a schematic structural diagram of a speckle structured light projection module based on a holographic waveguide configured with an inclined plane coupling input according to a third embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
As shown in fig. 1, the speckle structured light projection module based on a holographic waveguide according to an embodiment of the present invention includes an array light source 11 and a holographic waveguide unit 20, wherein the array light source 11 can emit a laser beam corresponding to a first speckle pattern, the holographic waveguide unit 20 includes a waveguide substrate 13, a first holographic optical element 201 and a second holographic optical element 202, the first holographic optical element 201 is attached to a first end of the waveguide substrate 13, the second holographic optical element 202 is attached to a second end of the waveguide substrate 13, the array light source 11 is disposed above the second end of the waveguide substrate 13, the laser beam emitted by the array light source 11 can be coupled into the waveguide substrate 13 via the second holographic optical element 202, and the laser beam can be waveguide-transmitted in the waveguide substrate 13 and output through the first holographic optical element 201; although fig. 1 shows an example in which the array light source is disposed above the second end of the waveguide substrate, it is understood that it is also permissible to dispose the array light source at other positions, for example, below the waveguide substrate, which can be flexibly adjusted according to the design of the system structure.
It should be noted that the Holographic Waveguide (HW) is an integrated Optical technology that uses a Holographic Optical Element (HOE) as a coupling input or output device to control light in glass or other Optical media for Waveguide transmission. The HOE is an optical component manufactured by a holographic interference method, can be manufactured into a holographic grating or holographic lens form according to the coupling function requirement, and is attached to the surface of glass or other optical media. Waveguide transmission is a way in which light modulates a guided light signal in a medium by Total Internal Reflection (TIR), and this way can be used to shift the optical axes of the input and output ends of an optical system with high efficiency.
In addition, the speckle structured light projection module needs to modulate the light corresponding to the first speckle pattern output by the array light source, such as collimation modulation and grating diffraction processing, so as to output speckles meeting expectations and requirements. The first holographic optical element 201 in the speckle structured light projection module of fig. 1 enables out-coupling of light in the waveguide substrate, and the second holographic optical element 202 enables in-coupling of light in the waveguide substrate for waveguide transmission in the waveguide substrate. It should be noted that, in the speckle structure light projection module of fig. 1, another light modulation component may be additionally disposed to implement modulation of the light beam, at this time, the light modulation component may be preferably disposed at a second end far away from the light source, that is, at a position close to the first optical element 201, so as to implement excellent heat dissipation performance, and specific details will also be developed in other embodiments below. In the embodiment of the present invention, by introducing the holographic waveguide unit 20, the light source and other optical elements are arranged by using the characteristic of optical axis deviation, so that the volume of the module is not increased while the heat dissipation function is realized, the structure is ensured to be light, thin and small, and the present invention can be widely and preferably applied to electronic devices.
Although the first end attached to the first holographic optical element 201 and the second end attached to the second holographic optical element 202 are shown in fig. 1 as being disposed on the same side of the waveguide substrate, it is understood that the first holographic optical element 201 and the second holographic optical element 202 may be disposed on different sides of the waveguide substrate according to design requirements; it should be noted that, coupling modulation of the holographic optical element is also required on one side of the array light source to form waveguide transmission, and if coupling is not performed by the holographic optical element, the waveguide substrate may be cut into an inclined plane. It will be appreciated that the choice of the first holographic optical element 201 and the second holographic optical element 202 may also vary, for example both may be transmissive holographic optical elements and/or reflective holographic optical elements; this allows flexible arrangement of the system components to achieve a desired heat dissipation effect.
Although FIG. 1 shows a projection module using a transmissive HOE design, it is understood that the module of the present invention may still use a reflective holographic optical element HOE, and accordingly, only the component positions of the module need to be adjusted.
In order to ensure a good waveguide transmission effect of light in the waveguide substrate, the laser beam may be transmitted in the waveguide substrate 13 according to a preset light propagation angle to satisfy a total reflection condition, that is:
wherein the content of the first and second substances,
is a predetermined angle of propagation of the light,
n is the optical refractive index of the waveguide substrate for the angle of total reflection.
As shown in fig. 2, in the speckle structured light projection module based on the holographic waveguide according to another embodiment of the present invention, a part of the light modulation element is disposed at the other end of the waveguide substrate away from the light source, so that good heat dissipation performance is achieved. Specifically, the speckle structured light projection module based on the holographic waveguide includes an array light source 11, which is configured to be a light Emitting spot source array, and is configured to provide illumination in the form of a preset first speckle pattern 12, where the array light source may be a Vertical Cavity Surface laser emitter (VCSEL), and is configured as a two-dimensional regularly or randomly-configured array light source, infrared light with a wavelength of 940nm, or other wavelength windows with high transmission efficiency; 13 is a waveguide substrate made of glass or other optical medium material with refractive index n; 142 is a Holographic Optical Element (HOE), and the module can further include a coupling-in HOE141, the HOE is only a film system, so the volume is thin and the miniaturization design is convenient; the 15 is a collimating lens, which is used for modulating the light beam emitted by the holographic waveguide into a collimated light beam and then emitting the collimated light beam, and can be realized by adopting a single lens, a combined lens, a micro-lens array or a Fresnel lens; 16 is a diffractive optical element DOE, which is used for receiving the first speckle pattern 12, copying and expanding the first speckle pattern into a second speckle pattern, forming a large-area array speckle light ray cluster, and projecting the speckle light ray cluster into an actual scene to be measured; 17 is a scene object to be detected; and 18, projecting the final second speckle pattern by the module to realize the projection of the second speckle pattern to the object of the scene to be measured. In the embodiment, the light source is separated from other optical modulation devices by a certain distance through waveguide transmission, and a heat dissipation device can be added to the light source independently, which is very beneficial to heat dissipation of the whole system.
It should be noted that the collimating lens 15 may also be placed before the input HOE141 to couple the laser beams emitted by the array light source, collimate the light beams of the light source, and then couple the light beams for waveguide transmission. In addition, the position and focal length of the collimating lens 15 can be flexibly selected according to a specific system design scheme, so that the collimating lens is matched with the focal length to complete the collimating function.
As shown in fig. 3, the speckle structure light projection module based on holographic waveguide according to another embodiment of the present invention includes an array light source 11, which is arranged to be designed as a light emitting spot source array for providing illumination in the form of a preset first spot pattern 12; 13 is a waveguide substrate made of glass or other optical medium material with refractive index n; 141 is a coupling input HOE; 143 is an HOE with a lens factor, which not only has the function of coupling out, but also has the function of collimation, and can modulate the laser beam into a collimated beam; 16 is DOE, which is used for receiving the first speckle pattern 12, copying and expanding the first speckle pattern into a second speckle pattern, forming a large-area array speckle light cluster, and projecting the large-area array speckle light cluster into a scene to be measured; 17 is a scene object; 18 is the final second speckle pattern projected by the module.
In contrast to the embodiment shown in fig. 2, the coupling-out HOE 143 in fig. 3 is a holographic HOE (i.e., a holographic lens optical element), which may be machined by interference using plane waves and spherical waves. Therefore, the collimating lens and the coupling output element are combined into a modulation device, the light and thin degree of the system is improved, and the design of a miniaturized projection module is facilitated. In addition, the collimating lens factor in fig. 3 can also be added in the coupled-in HOE, and the above embodiment can be flexibly adjusted according to the system design requirement.
Referring to fig. 4, a speckle structure light projection module based on holographic waveguide according to another embodiment of the present invention employs a composite HOE element 144. The speckle structure projection module comprises an array light source 11, a first speckle pattern 12 and a second speckle pattern, wherein the array light source 11 is arranged and designed to be a luminous spot source array and used for providing illumination in the form of the preset first speckle pattern 12; 13 is a waveguide substrate made of glass or other optical medium material with refractive index n; 141 is a coupling input HOE; the coupling output HOE 144 has the functions of a collimating lens and a copying grating, can also be used as a coupling output element, can be used for receiving the first speckle pattern 12, copying and expanding the first speckle pattern into a second speckle pattern, forming a large-area array speckle light cluster, and projecting the large-area array speckle light cluster to an actual scene to be measured; 17 is a scene object; 18 is the final second speckle pattern projected by the module.
In contrast to the embodiment shown in fig. 3, the coupling-out HOE 144 in fig. 4 is a HOE that functions as both a collimating lens and a replica grating, and can modulate the laser beam into a collimated beam and also realize modulation and expansion of the speckle pattern. Therefore, the collimating lens, the replica grating and the coupling output element are combined into a modulation device, so that the light and thin degree of the system is improved, and the design of a miniaturized projection module is facilitated.
As shown in fig. 5, another embodiment of the present invention is a speckle structured light projection module based on holographic waveguide, which adds a collimating lens factor separately from a replica grating in the in-coupling HOE and the out-coupling HOE. Specifically, the speckle structure light projection module based on the holographic waveguide comprises an array light source 11, which is arranged and designed into a luminous spot source array and is used for providing illumination in the form of a preset first speckle pattern 12; 13 is a waveguide substrate made of glass or other optical medium material with refractive index n; 145 is a coupled-in HOE with a collimating lens function; 146, a coupling output HOE with a grating copying function is used for receiving the first speckle pattern 12, copying and expanding the first speckle pattern into a second speckle pattern, forming a large-area array speckle light cluster, and projecting the speckle light cluster into an actual scene to be measured; 17 is a scene object; 18 is the final speckle pattern projected by the module. Therefore, higher system light and thin degree can be realized, and the design of the miniaturized projection module is more convenient to carry out.
As shown in fig. 6A to 6C, the speckle structured light projection module based on the holographic waveguide according to another embodiment of the present invention may cut the glass substrate into an inclined plane, and the plane of the waveguide substrate at the second end is cut into an inclined plane, so as to couple the laser beam to be subjected to waveguide transmission by the inclined plane, and the inclined plane coupling input mode may be directly used instead of the coupling input HOE, thereby improving the energy utilization efficiency of the system and saving the module manufacturing cost. Specifically, as in the speckle structured light projection module based on the holographic waveguide provided in fig. 6A, the coupling-out HOE 142 may only have a coupling-out function, and the collimating lens 15 on one side of the HOE achieves a collimating effect and the DOE 16 achieves a modulation replication effect of the light beam; in the speckle structured light projection module based on holographic waveguide as provided in fig. 6B, the out-coupled HOE 143 may be a holographic lens optical element, and the modulation replication of the light beam is realized by the DOE 16; in the speckle structured light projection module based on holographic waveguide as provided in fig. 6C, the out-coupling HOE 143 can be an element having both lens function and replica grating function. More preferably, the inclined surface can be plated with an antireflection film, thereby increasing the coupling efficiency. For some components in the speckle structure light projection module based on holographic waveguide shown in fig. 6A-6C, reference may be made to the related description of the above embodiments, and therefore, the description thereof is omitted here.
In some preferred embodiments, the in-coupling HOE and/or the out-coupling HOE may be fabricated by laser interference exposure processing. Therefore, the holographic optical element manufactured by laser interference exposure processing is applied, and compared with a speckle structure which is designed by DOE based on an etching process and applied in the prior related art, the speckle structure light projection module in the embodiment adopts the holographic optical element which is manufactured by laser interference exposure processing, the ghost line interference problem is avoided, stray background light is reduced, and the holographic optical element can be manufactured more efficiently and with lower cost compared with the etching process.
Specifically, the hologram lens HOE having a collimating lens function may be a hologram lens manufactured by interference of plane waves and spherical waves. Preferably, the interference processing process can be subjected to aberration optimization design by adopting a wave front compensation technology in the processing process so as to obtain the holographic lens with high imaging quality. The focal length of the holographic lens HOE is related to the coordinate parameters of spherical waves used in the preparation process, so that the focal length value of the holographic lens can be controlled by setting the related parameters of interference spherical waves, and the system is designed in a matching mode, so that a high-quality collimation effect is achieved.
The holographic grating HOE with the grating copying and expanding function is prepared by adopting plane waves with corresponding wavelengths through interference. Preferably, in order to avoid overlapping between speckles obtained by the projection module in each diffraction order, the grating period can be customized by controlling in the manufacturing method. Specifically, a target grating period capable of preventing the speckles corresponding to multiple diffraction orders of the holographic optical element from overlapping with each other may be obtained first, for example, the target grating period may be a collimated light beam matched with the array light source and capable of inputting, and outputting the collimated light beam between the speckles (second speckle patterns) of the diffraction orders to prevent the speckles from overlapping with each other; then, an included angle between two interference beams in the laser interference process is determined based on an included angle period model and a target grating period, wherein the included angle period model comprises a relation between the included angle of the interference beams and the grating period.
The position of the diffraction order for preparing the HOE is determined by the grating equation:
wherein the content of the first and second substances,
and
the diffraction angles are respectively horizontal and vertical, m and n are respectively horizontal and vertical diffraction orders, and deltax and deltay are respectively the grating periods of the HOE in the horizontal and vertical directions. In order to achieve a detectable depth range, the VCSEL speckle patterns replicated by the HOE in the various diffraction orders should avoid overlapping, and therefore the angle θ between the interfering beams may be controlled during the processing of the HOE.
Therefore, the embodiment of the invention also provides that the included angle period model can meet the following conditions:
wherein, Delta is the target holographic grating period, lambda is the wavelength of the laser beam, and theta is the included angle of the interference beam; thus, the grating period of the holographic grating may be controlled by controlling the angle θ between the interfering beams.
In addition, the composite HOE has the functions of collimating lens and copying grating, and the preparation method can be realized by a composite preparation technology, namely, two times of exposure recording can be carried out, so that the lens factor and the grating structure are processed on the same HOE; therefore, the composite HOE can further optimize the module and achieve the purpose of thinner design.
Two HOEs coupled in and out are holographic gratings, and are manufactured by laser interference exposure processing, two interference wavefronts are plane waves, and the intensity distribution of grating light fields formed by interference is as follows:
I1＝|exp(ik1·r)+exp(ik2·r)|2
＝2+2cos[(k1-k2)r]
in the formula I1Is the intensity of the interference light field, i is the unit of imaginary number, k1And k2The wave vectors of the two parallel light beams are respectively, and r is a coordinate system of the light beams.
On the other hand, the HOE with a holographic lens may be processed by interference using a plane wave and a spherical wave, and the intensity of the optical field formed by the interference is:
in the formula I2Is the intensity of the interference light field, i is the unit of imaginary number, k3And k4The wave vectors of the plane wave and the spherical wave are respectively, and r is a coordinate system of the light beam. Therefore, the focal length of the manufactured collimating lens HOE is related to the coordinate parameter of the spherical wave, so that the focal length value of the manufactured collimating lens HOE can be controlled by setting the related parameter of the interference spherical wave.
In some embodiments, the photosensitive material used to prepare the holographic optical element HOE (including both in-hole and out-hole) may also be a photosensitive material that is sensitive at the wavelength of the laser beam emitted by the array light source, e.g., both 940 nm. The holographic optical element HOE may also be a holographic grating prepared by interference exposure processing using a light beam corresponding to the wavelength of the laser beam emitted by the array light source 11; for example, when the light source used in the projection module employs an infrared laser with a wavelength of 940nm, the corresponding HOE also operates with a corresponding wavelength of 940nm, and thus the wavelength of the interference light beam should be the same when the HOE is manufactured.
In the embodiment of the invention, various design implementation schemes of the speckle projection module which is light, thin and small in structure and convenient for radiating the light source are provided. Wherein, the first design implementation scheme comprises four parts: the first part is an array light source, preferably a VCSEL light source, to output a first speckle pattern; the second part is a holographic waveguide unit which consists of a glass or other optical medium substrate and two HOEs serving as a coupling-in and coupling-out device; the third part is a collimating lens which modulates the laser beam emitted by the light source into a collimated beam; the fourth part is DOE which receives the first speckle pattern and copies and expands the first speckle pattern into a second speckle pattern which is not overlapped with each other and has uniform speckle density distribution, and projects the second speckle pattern onto the scene object to be measured.
In order to further improve the light, thin and small size of the system, the collimating lens can be designed as a holographic HOE attached to the waveguide medium substrate and used as a coupling-out element. The second design implementation therefore includes three parts: the first part is an array light source, preferably a VCSEL light source, to output a first speckle pattern; the second part is a holographic waveguide unit which consists of a glass or other optical medium substrate and two HOEs serving as a coupling-in and coupling-out device; the third part is DOE which receives the first spot pattern and copies and expands the first spot pattern into a second spot pattern which is not overlapped with each other and has uniform spot density distribution, and projects the second spot pattern onto the scene object to be measured.
In order to further improve the light, thin and small-sized degree of the system, the collimating lens and the DOE can be designed into an HOE to be attached to the waveguide medium substrate to be used as a coupling-out element, or the collimating lens and the DOE can be designed into HOEs with coupling-in and coupling-out functions respectively to be used. The third design implementation thus includes two parts: the first part is a VCSEL array light source and forms a first speckle pattern; the second part is a holographic waveguide unit which consists of a glass or other optical medium substrate and two HOEs serving as an in-out device and an out-in device, receives the first spot pattern, copies and expands the first spot pattern into a second spot pattern which is not mutually overlapped and has uniform spot density distribution, and projects the second spot pattern onto a scene object to be measured.
More preferably, the outcoupled HOE comprises both the collimating lens factor and the DOE modulation structure, and both are designed into a composite HOE, so that the composite HOE has the functions of both the collimating lens and the replica of the expansion grating. Regarding the preparation of the compound type HOE, the preparation can be completed by dividing into two exposure records, and the lens factor and the DOE grating structure are processed together on the same piece of HOE, and the specific processing can refer to the interference exposure process of the above brand new lens optical element and the holographic grating optical element.
In addition, when the incoming HOE is a holographic HOE and the outgoing HOE includes a DOE grating structure, the incoming HOE and the outgoing HOE may be separately manufactured.
In the above three design implementation schemes: in order to improve the energy utilization efficiency of the system, the glass substrate can be cut into inclined planes, and the mode of coupling and inputting the inclined planes can be directly used for replacing HOE. If the third implementation scheme adopts an inclined plane coupling-in mode, the collimating lens and the DOE need to be designed into a composite HOE and attached to the waveguide substrate to be used as a uniform coupling-out functional device. In order to improve the imaging effect of the system, the inclined glass substrate surface can be further designed into a free-form surface type so as to optimize the aberration of the system.
Therefore, in the speckle projection module provided by the embodiment of the invention, the speckle projection module not only has the advantages of compact, light and thin structure and high miniaturization design degree, but also can separate the light source from the optical axes of other optical elements by a certain distance through the transmission function of the waveguide, so that a heat dissipation device is separately added for the light source, and the overall heat dissipation design of a system is facilitated.
Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and the simple modifications all belong to the protection scope of the embodiments of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention do not describe every possible combination.
In addition, any combination of various different implementation manners of the embodiments of the present invention is also possible, and the embodiments of the present invention should be considered as disclosed in the embodiments of the present invention as long as the combination does not depart from the spirit of the embodiments of the present invention.
Claims (11)
1. A speckle structure light projection module based on holographic waveguide comprises a holographic waveguide unit and an array light source, wherein the array light source is used for emitting laser beams corresponding to a first speckle pattern, the holographic waveguide unit comprises a waveguide substrate, a first holographic optical element and a second holographic optical element, the first holographic optical element is attached to a first end of the waveguide substrate, and the second holographic optical element is attached to a second end of the waveguide substrate; the speckle structure light projection module also comprises a diffraction optical element, a first light source and a second light source, wherein the diffraction optical element is used for receiving the first speckle pattern, copying and expanding the first speckle pattern into a second speckle pattern which is not mutually overlapped and has uniform speckle density distribution, and projecting the second speckle pattern into a scene to be measured;
the second holographic optical element is used for coupling laser beams emitted by the array light source into the waveguide substrate, and the laser beams can be subjected to waveguide transmission in the waveguide substrate and are output through the first holographic optical element;
the first holographic optical element and/or the second holographic optical element are/is a holographic grating which is prepared by processing laser interference exposure of light beams corresponding to the wavelength of the laser beams emitted by the array light source.
2. The holographic waveguide-based speckle structured light projection module of claim 1, wherein the speckle structured light projection module further comprises a collimating lens for modulating the laser beam into a collimated beam, wherein
The collimating lens is disposed near the first end for modulating the laser beam output by the first holographic optical element, or
The collimating lens is disposed near the second end for modulating the laser beam emitted by the array light source.
3. The holographic waveguide-based speckle structured light projection module of claim 2, wherein said collimating lens comprises one or more of: single lenses, combination lenses, microlens arrays, and fresnel lenses.
4. The holographic waveguide-based speckle structured light projection module of claim 1, wherein said first holographic optical element is a holographic lens optical element for modulating a laser beam into a collimated beam; or
The second holographic optical element is a holographic lens optical element for modulating the laser beam into a collimated beam.
5. The holographic waveguide based speckle structured light projection module of any of claims 2-4, wherein said first holographic optical element further comprises a grating replication function for modulating the expanded collimated light beam to form a second speckle pattern and projecting the second speckle pattern onto the scene object under test.
6. The holographic waveguide-based speckle structured light projection module of claim 1, wherein the first and second holographic optical elements comprise transmissive and/or reflective holographic optical elements, and
the first holographic optical element and the second holographic optical element are attached to the same side or different sides of the waveguide substrate.
7. The speckle structured light projection module based on the holographic waveguide of claim 1, wherein the laser beam is transmitted in the waveguide substrate according to a preset light propagation angle, and the following conditions are satisfied:
wherein the content of the first and second substances,
is a predetermined angle of propagation of the light,
n is the optical refractive index of the waveguide substrate for the angle of total reflection.
8. A speckle structure light projection module based on holographic waveguide comprises a holographic waveguide unit and an array light source, wherein the array light source is used for emitting laser beams corresponding to a first speckle pattern, the holographic waveguide unit comprises a waveguide substrate and a first holographic optical element, and the first holographic optical element is attached to a first end of the waveguide substrate; the speckle structure light projection module also comprises a diffraction optical element, a first light source and a second light source, wherein the diffraction optical element is used for receiving the first speckle pattern, copying and expanding the first speckle pattern into a second speckle pattern which is not mutually overlapped and has uniform speckle density distribution, and projecting the second speckle pattern into a scene to be measured;
wherein a plane of the waveguide substrate at the second end is cut into an inclined plane to couple a laser beam to be subjected to waveguide transmission through the inclined plane so that the laser beam can be waveguide-transmitted in the waveguide substrate and output through the first holographic optical element;
the first holographic optical element is a holographic grating which is prepared by processing laser interference exposure of light beams corresponding to the wavelength of the laser beams emitted by the array light source.
9. The holographic waveguide-based speckle structured light projection module of claim 8, further comprising a collimating lens proximate to the first end for modulating the laser beam output by the first holographic optical element into a collimated beam.
10. The holographic waveguide-based speckle structured light projection module of claim 8, wherein said first holographic optical element is a holographic lens optical element for modulating a laser beam into a collimated beam.
11. The holographic waveguide based speckle structured light projection module of claim 9 or 10, wherein the first holographic optical element further comprises a grating replication function for modulating the expanded collimated light beam to form a second speckle pattern and projecting the second speckle pattern onto the scene object to be measured.
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