Optical element providing collimation and fan-out or diffusion

Abstract

The present disclosure describes an optical element and a method for designing and manufacturing such an optical element. An example of the device includes an optical element having a first surface and a second surface, the first and second surfaces being on opposite sides of the optical element. The first surface is structured to collimate a light beam incident on the first surface, and the second surface is structured to provide a correction to the collimation imparted by the first surface and to provide at least one of optical fan-out or diffusion of the light beam.

Description

Technical Field

[0001] The field of the present disclosure The present disclosure relates to an optical element for dot projection and the like.

Background Art

[0002] Background Various consumer products are designed to be able to recognize or navigate their surroundings. For example, some smartphones use an infrared (IR) dot projector that functions as a structured illuminator to provide face recognition. The projector generates a pattern of infrared dots in front of the smartphone, and the pattern can illuminate a face or other object, as a result of which the face or other object can be photographed by a camera. The dot projector can include, for example, a light-emitting unit, a lens, and an array of beam splitters. The lens and beam splitters generate a replication of the array source pattern and project a replicated pattern of dots onto a human face or other object. An infrared camera can capture the pattern used in a structured light algorithm to detect the three-dimensional (3D) shape of a face or other object.

Summary of the Invention

Means for Solving the Problems

[0003] Summary The present disclosure describes an optical element that can be used, for example, for dot projection and / or flood illumination, and a method for designing and manufacturing such an optical element.

[0004] For example, the present disclosure describes an apparatus including an optical element having a first surface and a second surface, where the first and second surfaces are on opposite sides of the optical element. The first surface is structured to collimate an optical beam incident on the first surface, and the second surface is structured to provide a correction to the collimation imparted by the first surface and to provide at least one of optical fan-out or diffusion of the optical beam.

[0005] Some implementations include one or more of the following features. For example, in some implementations, the structure of the first surface operable to collimate an optical beam has more high-frequency components than the structure of the second surface operable to provide a correction to the collimation imparted by the first surface. In some implementations, the structure of the first surface operable to collimate an optical beam corresponds to a first component of a phase function, and the structure of the second surface operable to provide a correction to the collimation imparted by the first surface corresponds to a second component of the phase function, and the maximum gradient of the first component of the phase function is smaller than the maximum gradient of the second component of the phase function. In some cases, the maximum amplitude of the second component of the phase function is smaller than the maximum amplitude of the first component of the phase function. For example, in some cases, the maximum amplitude of the second component of the phase function is 10% or less of the maximum amplitude of the first component of the phase function.

[0006] In some implementations, the optical fan-out is provided by a discrete periodic surface relief structure on the second surface and can divide the optical beam into a predetermined number of diffraction orders at respective angles. In some implementations, the light diffusion is provided by a discrete aperiodic surface relief structure on the second surface.

[0007] In some implementations, the apparatus further includes a light emitter operable to emit light toward the first surface of the optical element, the optical element is arranged such that the light passes through the optical element, and the optical element projects a pattern using the light.

[0008] The present disclosure also describes a method that includes splitting a phase function into first and second components, where the first component represents collimation implemented on a first surface of an optical element and the second component represents collimation correction implemented on a second surface of the optical element. The method includes obtaining a combined phase function by combining at least one of a fan-out phase function or a diffuser phase function with the second component of the collimator phase function, determining a first optical element structure corresponding to the first component of the collimator phase function, and determining a second optical element structure corresponding to the combined phase function. The method further includes manufacturing an optical device that includes a substrate having a first surface and a second surface on opposite sides of the substrate, where the first optical element structure is on the first surface and the second optical element structure is on the second surface.

[0009] In some implementations, instead of obtaining a combined phase function by combining a fan-out phase function with the second component of the collimator phase function, corresponding optical element structures are coupled. For example, the present disclosure also describes a method that includes splitting a phase function into first and second components, where the first component represents collimation implemented on a first surface of an optical element and the second component represents collimation correction implemented on a second surface of the optical element. The first component of the collimator phase function is converted into a corresponding first optical element structure, and the second component of the phase function is converted into a corresponding second optical element structure. The method includes coupling a fan-out structure with the second optical element structure to obtain a coupled optical element structure. The method further includes manufacturing an optical device that includes a substrate having a first surface and a second surface on opposite sides of the substrate, where the first optical element structure is on the first surface and the coupled optical element structure is on the second surface.

[0010] Some implementations of this method include one or more of the following features. For example, in some cases, the maximum gradient of the first component of the phase correlation function is smaller than the maximum gradient of the second component of the phase correlation function. In some cases, the maximum amplitude of the second component of the phase correlation function is smaller than the maximum amplitude of the first component of the phase correlation function. For example, in some cases, the maximum amplitude of the second component of the phase correlation function is 10% or less of the maximum amplitude of the first component of the phase correlation function. In some implementations, the first diffractive optical element structure for collimation has more high-frequency components than the second diffractive optical element structure for providing correction for collimation.

[0011] In some implementations, the method further includes converting the fan-out structure into a corresponding fan-out phase correlation function before synthesizing the fan-out phase correlation function with the second component of the collimator phase correlation function to obtain a synthesized phase correlation function. Subsequently, the corresponding fan-out phase correlation function is used as the fan-out phase correlation function synthesized with the second component of the collimator phase correlation function.

[0012] In some implementations, manufacturing the optical device includes forming the first and second optical element structures on the first and second surfaces of the substrate, respectively, by nano-wafer level replication.

[0013] Other aspects, features, and advantages will become readily apparent from the following detailed description, the accompanying drawings, and the claims.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

[0015] Detailed Description The dot projector may use an array of light emitters (e.g., an array of vertical cavity surface emitting lasers (VCSLEs)) as a light source. The light emitted by the VCSELs is typically highly divergent and should be collimated. Thus, the dot projector may include one or more diffractive optical elements (DOEs), such as a fan-out diffractive beam splitter, to collimate the light from the VCSELs before the light passes through.

[0016] According to the present disclosure, a single optical element is described that provides both functions, i.e., the optical element serves to collimate the incident light beam and also provides a fan-out for generating a plurality of light beams by deflecting the incident light into different diffraction orders. In particular, the optical element is structured such that the collimation function is split between two surfaces of the optical element, and one of those surfaces also provides a fan-out function. For example, both the front and rear surfaces of the optical element can serve to collimate the incident light as a whole, and the rear surface can also provide a fan-out function. In some implementations, the optical element is structured such that the front surface provides most of the collimation, while the rear surface provides collimation correction and fan-out.

[0017] FIG. 1 shows an example of an optical element 10 having a first surface (e.g., a front surface) 12 and a second surface (e.g., a rear surface) 14. The first and second surfaces 12, 14 are on opposite sides of the optical element 10. The first surface 12 can be structured to substantially collimate one or more light beams incident on the first surface 12. The second surface 14 is structured to provide a correction to the collimation imparted by the first surface 12 and to provide a fan-out function (i.e., generate multiple light beams by deflecting the incident light to different diffraction orders). The following aspects refer to a diffractive optical element (DOE) as an example of the optical element 10. However, in some implementations, the optical element 10 can be a meta optical element (MOE).

[0018] In some implementations, the collimation structure on the first surface 12 includes high spatial frequencies, while the structure on the second surface that provides collimation correction consists of lower spatial frequencies that are less likely to significantly perturb or interfere with the fan-out function of the second surface.

[0019] As shown in FIG. 2, in use, each light beam 16 incident on the first surface 12 passes through the optical element 10, and multiple diffraction orders 18 exit through the second surface 14. A single optical element 10 can provide both a collimation function and a fan-out function for incident light (e.g., light beams emitted by an array of VCSELs). However, as described above, the collimation function is divided between the two surfaces 12, 14, and the collimation correction is provided by the structure of the second surface 14.

[0020] FIG. 3 is a flowchart showing a method of designing and manufacturing the optical element 10 as described above. Assume that the collimation function of the optical element 10 is designed to have a certain phase function. Next, as shown by 102, the phase function is divided into two components, C1 and C2. The first component C1 can represent, for example, the main collimation implemented on the first surface 12 of the optical element, and the second component C2 can represent the collimation correction implemented on the second surface 14 of the optical element. Preferably, the second component C2 should have a relatively low maximum gradient (i.e., slope). For example, the second component C2 can have a maximum gradient significantly smaller than that of the first component C1 and cannot vary significantly depending on the radial position more than the first component C1. That is, the second component C2 of the phase function should vary relatively slowly. One way to achieve this constraint is to define the maximum amplitude of the second component C2 of the phase function relative to the maximum amplitude of the first component C1. For example, in some implementations, the maximum amplitude of the second component C2 is set to be less than or equal to a specified percentage (e.g., 10%) of the maximum amplitude of the first component C1. Since the maximum amplitude of the second component C2 is relatively small, the maximum gradient of the second component C2 is also relatively low.

[0021] FIG. 4 shows an example of the first component C1 and the second component C2 of the phase function for implementing collimation in the optical element 10. The physical structure 200 (see FIG. 5A) corresponding to the first component C1 of the phase function has more high-frequency components 202 than the physical structure 204 (see FIG. 5B) corresponding to the second component C2 of the phase function. Thus, the physical structure of the second component C2 of the phase function can be treated as being relatively flat so that it does not significantly perturb or interfere with the fan-out function it is subsequently synthesized into.

[0022] The fan-out function on the second surface 14 can be provided, for example, by a discrete periodic surface relief structure having a two-dimensional (x,y) shape. The fan-out structure can be designed, for example, to split a light beam into a specified number (e.g., 3) of diffraction orders at a specified angle. As shown by 104 (FIG. 3), in a situation where the fan-out structure is periodic and the feature size and unit cell size are relatively small, the physical structure of the fan-out can be determined, for example, using Maxwell's full wave equation. FIG. 6 shows an example of the fan-out structure 210. When the unit cell is relatively large, a scalar diffraction approximation of Maxwell's full wave equation can be used.

[0023] In some implementations, the second surface can be structured to provide a correction to the collimation imparted by the first surface and to provide diffusion of the light beam. The light diffusion can be provided, for example, by a discrete aperiodic surface relief structure on the second surface.

[0024] Next, as shown by 106 (FIG. 3), the fan-out structure 201 is converted into a corresponding fan-out phase function such that the vertical step is the same as in the case of the second component C2 of the collimator phase function. That is, there is a correspondence between the height of the structure and the phase delay introduced by the operating wavelength. FIG. 7 shows an example of the fan-out phase function 212 corresponding to the fan-out structure of FIG. 6.

[0025] Next, as shown by 108 (FIG. 3), the fan-out phase correlation function 212 (or diffusion function) is combined with the second component C2 of the collimator phase correlation function to obtain a combined phase correlation function. Since the high-frequency components of the collimator phase correlation function are analyzed and included in the first component C1 of the collimator phase correlation function, for example, the fan-out (or diffusion) phase correlation function can be combined with the second component C2 of the collimator phase correlation function without significantly perturbing the fan-out phase correlation function. As described above, analyzing the high-frequency components of the collimator phase correlation function can help reduce the extent to which perturbation is added to the fan-out phase correlation function (e.g., making the fan-out structure no longer periodic).

[0026] Next, as shown by 110 (FIG. 3), a first DOE structure for implementing the first component C1 of the collimator phase correlation function is determined. Similarly, as shown by 112 (FIG. 3), a second DOE structure for implementing the combined phase correlation function (i.e., the DOE structure corresponding to the combination of the fan-out phase correlation function 212 (or diffusion function) and the second component C2 of the collimator phase correlation function) is determined.

[0027] Then, as shown at 114, an optical device 10 can be manufactured that includes the first DOE structure on the first surface 12 and the second DOE structure on the second surface 14. In some implementations, the optical device 10 can be manufactured using polymer-on-glass technology. For example, the device 10 can be composed of a glass substrate having DOE structures on the first and second surfaces 12, 14 formed by nano-wafer level replication.

[0028] In some implementations, the operation of converting the fan-out structure 201 into a corresponding fan-out phase function (106 in FIG. 3), and then the operation of synthesizing the fan-out phase function 212 with the second component C2 of the collimator phase function (108 in FIG. 3) can be omitted. Instead, the second component C2 of the collimator phase function can be converted into a corresponding DOE structure 204 (see, for example, FIG. 5B), and that DOE structure can be combined with the fan-out structure. That is, instead of synthesizing the phase functions of the fan-out and the second component C2, their corresponding structures are combined. For example, the fan-out structure can be designed to be provided directly on the structure corresponding to the second component C2 of the collimator phase function.

[0029] The foregoing description has referred to the DOE as an example of the optical element 10, but in some implementations, the optical element 10 can be a meta-optical element (MOE). Thus, for example, in some implementations, the apparatus according to the present disclosure can include a meta-optical element (MOE) having a first surface and a second surface, the first and second surfaces being on opposite sides of the MOE. The first surface can be structured to collimate the light beam incident on the first surface, and the second surface is structured to provide a correction to the collimation imparted by the first surface and to provide an optical fan-out of the light beam.

[0030] The above optical structure can be used, for example, in 3D sensing, LiDAR, and / or dot projectors for machine vision applications targeting the home appliance, industrial, Internet of Things (IoT), medical, and / or automotive markets. These can be particularly well-suited for industries that require excellent performance, superior light control, lightweight and compact designs. Examples of other consumer products that can incorporate a dot projector include robotic vacuum cleaners and lawn mowers, machine vision applications (such as augmented and virtual reality), and autonomous guided vehicles (AGVs). Additionally, in some implementations, the optical structure can function, for example, as a diffuser incorporated into flood lighting for standard imaging and / or 3D sensing.

[0031] The various aspects of the subject matter and functional operations described herein (e.g., the operations described in connection with FIGS. 3-7) can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware. Accordingly, aspects of the subject matter described herein can be implemented, for example, as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter that generates a machine-readable propagated signal, or one or more combinations thereof. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware.

[0032] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, either as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. The program can be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), a single file dedicated to the program in question, or multiple cooperating files (e.g., files that hold one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer, or located on one site, or distributed across multiple sites and executed on multiple computers interconnected by a communication network.

[0033] The processes and logical flows described herein can be implemented by one or more programmable processors executing one or more computer programs to perform functions by operating on input data to produce output. The processes and logical flows can also be implemented by, for example, FPGA (field programmable gate array) or ASIC (application specific integrated circuit) dedicated logic circuitry, and the apparatus can also be implemented as dedicated logic circuitry, such as an FPGA or ASIC.

[0034] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, as well as any one or more processors of any kind of digital computer. In general, a processor receives instructions and data from a read only memory or a random access memory or both. Essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, by way of example semiconductor memory devices, such as, EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, dedicated logic circuitry.

[0035] FIG. 8 shows an example of an optical dot projector 800. The dot projector 800 includes a substrate 802 and a light emitter 804 mounted on or integrated with the substrate 802. The light emitter 804 may include, for example, one or more lasers (e.g., vertical cavity surface emitting lasers) or light emitting diodes. Light 806 (e.g., infrared) generated by the light emitter 804 passes through the DOE 10 and exits the dot projector. The DOE 10 may be implemented as the optical device described above in connection with FIGS. 1 and 2, for example. The DOE 10 is arranged to intersect the path of the emitted light 806 and is operable to collimate the light 806 and split it into a plurality of diffraction orders 808, such that the dot projector 800 projects a pattern of dots onto an object (e.g., a human face) external to the projector 800.

[0036] Although this document contains details of many specific implementation forms, these should not be construed as limitations on the scope of any invention or what can be claimed by a patent, but rather should be construed as descriptions of features specific to particular embodiments. Specific features described herein in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented separately, or in any suitable partial combination, in a plurality of embodiments. Various modifications can be made to the foregoing examples. For example, steps shown to be performed in a particular order may be performed in a different order or simultaneously. Accordingly, other implementation forms are also within the scope of the claims.

Claims

1. An optical element having a first surface and a second surface, wherein the first and second surfaces are on opposite sides of the optical element, The first surface is structured to collimate a light beam incident on the first surface, and An apparatus in which the second surface is structured to provide a correction for the collimation provided by the first surface and to provide at least one of optical fan-out or diffusion of the light beam.

2. The apparatus according to claim 1, wherein the structure of the first surface, which is operable to collimate the light beam, has more high-frequency components than the structure of the second surface, which is operable to provide the correction to the collimation provided by the first surface.

3. The apparatus according to claim 1, wherein the structure of the first surface operable to collimate the light beam corresponds to a first component of a phase function, and the structure of the second surface operable to provide the correction for the collimation provided by the first surface corresponds to a second component of the phase function, and the maximum gradient of the first component of the phase function is smaller than the maximum gradient of the second component of the phase function.

4. The apparatus according to claim 3, wherein the maximum amplitude of the second component of the phase function is smaller than the maximum amplitude of the first component of the phase function.

5. The apparatus according to claim 4, wherein the maximum amplitude of the second component of the phase function is 10% or less of the maximum amplitude of the first component of the phase function.

6. The apparatus according to claim 1, wherein the second surface is structured to provide an optical fan-out of the light beam, and the optical fan-out is provided by a discrete periodic surface relief structure on the second surface.

7. The apparatus according to claim 1, wherein the second surface is structured to provide diffusion of the light beam, and the diffusion is provided by a discrete non-periodic surface relief structure on the second surface.

8. The apparatus according to claim 1, wherein the second surface is structured to provide an optical fan-out of the light beam, and the optical fan-out is operable to divide the light beam into a predetermined number of diffraction orders at each angle.

9. The optical element further includes a light-emitting body that is operable to emit light toward the first surface of the optical element, The optical element is arranged such that light passes through the optical element, and the optical element projects a pattern using the light. The apparatus according to any one of claims 1 to 8.

10. Dividing the phase function into first and second components, wherein the first component represents collimation implemented on a first surface of the optical element, and the second component represents collimation correction implemented on a second surface of the optical element, A composite phase function is obtained by combining at least one of the fan-out phase function or the diffusion phase function with the second component of the collimator phase function, Determining the first optical element structure corresponding to the first component of the collimator phase function, To determine the second optical element structure corresponding to the aforementioned composite phase function, Manufacturing an optical device including a substrate having a first surface and a second surface on opposite sides of the substrate, wherein the first optical element structure is on the first surface and the second optical element structure is on the second surface. Methods that include...

11. The method according to claim 10, wherein the maximum gradient of the first component of the phase function is smaller than the maximum gradient of the second component of the phase function.

12. The method according to claim 11, wherein the maximum amplitude of the second component of the phase function is smaller than the maximum amplitude of the first component of the phase function.

13. The method according to claim 12, wherein the maximum amplitude of the second component of the phase function is 10% or less of the maximum amplitude of the first component of the phase function.

14. The method according to claim 10, wherein the first optical element structure for collimation has more high-frequency components than the second optical element structure for providing the correction for the collimation.

15. The method includes combining the fan-out phase function with the second component of the collimator phase function to obtain the combined phase function, Before combining the aforementioned fan-out phase function with the second component of the collimator phase function to obtain a combined phase function, the fan-out structure is transformed into the corresponding fan-out phase function. Next, the corresponding fan-out phase function is used as the fan-out phase function that is combined with the second component of the collimator phase function. The method according to claim 10, further comprising:

16. The method according to any one of claims 10 to 15, wherein the manufacturing of the optical device includes forming the first and second optical element structures on the first and second surfaces of the substrate, respectively, by nanowafer-level replication.

17. Dividing the phase function into first and second components, wherein the first component represents collimation implemented on a first surface of the optical element, and the second component represents collimation correction implemented on a second surface of the optical element, Converting the first component of the collimator phase function into the corresponding first optical element structure, Converting the second component of the phase function to the corresponding second optical element structure, The fan-out structure is coupled with the second optical element structure to obtain a coupled optical element structure, Manufacturing an optical device including a substrate having a first surface and a second surface on opposite sides of the substrate, wherein the first optical element structure is on the first surface and the coupled optical element structure is on the second surface. Methods that include...

18. The method according to claim 17, wherein the maximum gradient of the first component of the phase function is smaller than the maximum gradient of the second component of the phase function.

19. The method according to claim 18, wherein the maximum amplitude of the second component of the phase function is smaller than the maximum amplitude of the first component of the phase function.

20. The method according to claim 19, wherein the maximum amplitude of the second component of the phase function is 10% or less of the maximum amplitude of the first component of the phase function.

21. The method according to any one of claims 17 to 20, wherein the manufacturing of the optical device includes forming the first and second coupled optical element structures on the first and second surfaces of the substrate, respectively, by nanowafer-level replication.

Images