Optical element providing collimation and fan-out or diffusion

Abstract

The present disclosure describes optical elements and methods for designing and making such optical elements. An example apparatus includes an optical element having a first surface and a second surface, where the first surface and the second surface are on opposite sides of the optical element from each other. The first surface is configured to collimate a light beam incident on the first surface, and the second surface is configured to provide correction of the collimation caused by the first surface and to provide at least one of optical fan-out or diffusion for the light beam.

Description

Technical Field

[0001] The present disclosure relates to optical elements for point projection and the like. Background Art

[0002] Various consumer products are designed to be able to identify or navigate around their surroundings. For example, some smartphones use an infrared (IR) dot projector that acts as a structured light emitter to provide facial recognition. The projector produces a pattern of infrared dots in front of the smartphone, which can illuminate a face or other object so that the face or other object can be captured by a camera. The dot projector can include, for example, an array of light emitting units, a lens, and a beam splitter. The lens and beam splitter produce a replica of the array source pattern and project the replicated dot pattern onto a person's face or other object. The IR camera can capture the pattern to be used in a structured light algorithm to detect the three-dimensional (3D) shape of a face or other object. Summary of the invention

[0003] This disclosure describes optical elements that can be used, for example, for spot projection and / or flood illumination, and methods for designing and making such optical elements.

[0004] For example, the present disclosure describes an apparatus that includes an optical element having a first surface and a second surface, wherein the first surface and the second surface are on opposite sides of the optical element from each other. The first surface is configured to collimate a light beam incident on the first surface, and the second surface is configured to provide correction for the collimation caused by the first surface and provide at least one of optical fan-out or diffusion for the light beam.

[0005] Some embodiments include one or more of the following features. For example, in some embodiments, the structure of the first surface operable to collimate the light beam has more high frequency components than the structure of the second surface operable to provide correction for the collimation caused by the first surface. In some embodiments, 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 correction for the collimation caused by the first surface corresponds to a second component of the phase function, wherein the maximum gradient of the first component of the phase function is less 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 less 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 does not exceed 10% of the maximum amplitude of the first component of the phase function.

[0006] In some embodiments, optical fan-out is provided by discrete periodic surface relief structures on the second surface and can split the light beam into a predetermined number of diffraction orders at corresponding angles. In some embodiments, optical diffusion is provided by discrete non-periodic surface relief structures on the second surface.

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

[0008] The present disclosure also describes a method comprising: separating a phase function into a first component and a second component, wherein the first component represents the collimation to be achieved on a first surface of an optical element, and the second component represents the collimation correction to be achieved on a second surface of the optical element. The method comprises: combining at least one phase function of a fan-out phase function or a diffuse phase function with a second component of a collimator phase function to obtain a combined 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 comprises: making an optical device comprising a substrate having a first surface and a second surface respectively on opposite sides of the substrate, wherein the first optical element structure is on the first surface, and wherein the second optical element structure is on the second surface.

[0009] In some embodiments, instead of combining the fan-out phase function with the second component of the collimator phase function to obtain a combined phase function, the corresponding optical element structures are combined. For example, the present disclosure also describes a method comprising: separating the phase function into a first component and a second component, wherein the first component represents the collimation to be achieved on the first surface of the optical element, and the second component represents the collimation correction to be achieved on the second surface of the optical element. Converting the first component of the collimator phase function into a corresponding first optical element structure, and converting the second component of the phase function into a corresponding second optical element structure. The method comprises: combining the fan-out structure with the second optical element structure to obtain a combined optical element structure. The method further comprises: making an optical device, the optical device comprising a substrate having a first surface and a second surface on opposite sides of the substrate, respectively, wherein the first optical element structure is on the first surface, and wherein the combined optical element structure is on the second surface.

[0010] Some embodiments of the method include one or more of the following features. For example, in some cases, the maximum gradient of the first component of the phase function is less 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 less 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 does not exceed 10% of the maximum amplitude of the first component of the phase function. In some embodiments, the first diffractive optical element structure used for collimation has more high-frequency components than the second diffractive optical element structure used to provide correction for the alignment.

[0011] In some embodiments, the method further comprises: before combining the fan-out phase function with the second component of the collimator phase function to obtain the combined phase function, converting the fan-out structure into a corresponding fan-out phase function, and then using the corresponding fan-out phase function as the fan-out phase function combined with the second component of the collimator phase function.

[0012] In some embodiments, fabricating the optical device includes forming a first optical element structure and a second optical element structure on a first surface and a second surface of a substrate, respectively, by nanowafer-scale replication.

[0013] Other aspects, features, and advantages will be apparent from the following detailed description, the accompanying drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 An example of an optical element providing both a collimator function and a fan-out function is shown.

[0015] Figure 2 Show Figure 1 Example operation of the optical element.

[0016] Figure 3 It is shown that the design and manufacture Figure 1 A flow chart of an example method of an optical element.

[0017] Figure 4 An example of two components of the collimator phase function is shown.

[0018] Figure 5A An example DOE structure corresponding to the first component of the collimator phase function is shown.

[0019] Figure 5B An example DOE structure corresponding to the second component of the collimator phase function is shown.

[0020] Figure 6 An example fan-out structure is shown.

[0021] Figure 7 Shown with Figure 6Example of the phase function corresponding to the fan-out structure.

[0022] Figure 8 An example of an optical dot projector is shown. DETAILED DESCRIPTION

[0023] Dot projectors sometimes use an array of light emitters (e.g., a vertical cavity surface emitting laser (VCSLE) array) as a light source. The light emitted by a VCSLE is typically strongly divergent and should be collimated. Therefore, a dot projector may include one or more diffractive optical elements (DOEs) to collimate the light from the VCSLE before passing the light through a fan-out diffractive optical element (e.g., a fan-out diffractive beam splitter).

[0024] According to the present disclosure, a single optical element is described that provides two functions; namely, the optical element is used to collimate an incident light beam, and also provides fan-out to generate multiple light beams by deflecting the incident light into different diffraction orders. In particular, the optical element is constructed so that the collimation function is divided between two of the surfaces of the optical element, and one of the surfaces also provides the fan-out function. For example, both the front surface and the rear surface of the optical element can be used together to collimate the incident light, and the rear surface can also provide the fan-out function. In some embodiments, the optical element is constructed so that the front surface provides most of the collimation, while the rear surface provides collimation correction as well as fan-out.

[0025] Figure 1 An example of an optical element 10 having a first (e.g., front) surface 12 and a second (e.g., rear) surface 14 is shown. The first surface 12 and the second surface 14 are on opposite sides of the optical element 10. The first surface 12 can be configured so that one or more light beams incident on the first surface 12 are substantially collimated. The second surface 14 is configured to provide correction for the collimation caused by the first surface 12 and to provide a fan-out function (i.e., generating multiple light beams by deflecting the incident light into different diffraction orders). The following aspects relate to a diffractive optical element (DOE) as an example of the optical element 10. However, in some embodiments, the optical element 10 can be a meta-optical element (MOE).

[0026] In some embodiments, the collimating structures on the first surface 12 include high spatial frequencies, while the structures on the second surface providing collimation correction consist of lower spatial frequencies that are less likely to significantly perturb or interfere with the fan-out function of the second surface.

[0027] like Figure 2As shown, in use, each light beam 16 incident on the first surface 12 passes through the optical element 10, and a plurality of diffraction orders 18 are emitted through the second surface 14. A single optical element 10 can provide both collimation and fan-out functions for incident light (e.g., a light beam emitted by a VCSLE array). However, as described above, the collimation function is split between the two surfaces 12, 14, and the collimation correction is provided by the structure of the second surface 14.

[0028] Figure 3 1 is a flow chart showing a method for designing and manufacturing an optical element 10 as described above. Assume that the collimation function of the optical element 10 is designed to have a specific phase function. Then, as shown in 102, the phase function is divided into two components, C1 and C2. The first component C1 can represent, for example, the main collimation to be achieved on the first surface 12 of the optical element, and the second component C2 can represent the collimation correction to be achieved 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 that is significantly smaller than the gradient of the first component C1, and can vary significantly less with radial position than the first component C1. That is, the second component C2 of the phase function should change relatively slowly. One way to achieve this constraint is to limit 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 embodiments, the maximum amplitude of the second component C2 is set to not exceed 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 will also be relatively low.

[0029] Figure 4 An example of a first component C1 and a second component C2 of a phase function for achieving collimation in an optical element 10 is shown. Compared with a physical structure 204 corresponding to the second component C2 of the phase function (see Figure 5B ), the physical structure 200 corresponding to the first component C1 of the phase function (see Figure 5A ) will have more high frequency components 202. This allows the physical structure of the second component C2 of the phase function to be treated as if it were relatively flat, making it less likely to significantly perturb or interfere with the fan-out function with which it is subsequently combined.

[0030] 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 the light beam into a specified number (e.g., three) of diffraction orders at a specified angle. As shown in 104 ( Figure 3), for the case 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 equations. Figure 6 An example of a fan-out structure 210 is shown. If the unit cell is relatively large, then the scalar diffraction approximation of Maxwell's full wave equations can be used.

[0031] In some embodiments, the second surface can be configured to provide correction for the collimation caused by the first surface and provide diffusion for the light beam.For example, optical diffusion can be provided by discrete non-periodic surface relief structures on the second surface.

[0032] Next, as shown in 106 ( Figure 3 ), the fan-out structure 201 is converted into a corresponding fan-out phase function so that the vertical step is the same as the second component C2 of the collimator phase function. That is, there is a corresponding relationship between the height of the structure and the phase delay to be introduced at the operating wavelength. Figure 7 Shown corresponding to Figure 6 An example of a fan-out phase function 212 of a fan-out structure.

[0033] Next, as shown in 108 ( Figure 3 ), the fan-out phase function 212 (or diffuse function) is combined with the second component C2 of the collimator phase function to obtain a combined phase function. It is possible to combine the fan-out (or diffuse) phase function with the second component C2 of the collimator phase function without significantly disturbing the fan-out phase function because the high-frequency components of the collimator phase function have been resolved and included in the first component C1 of the collimator phase function. As described above, resolving the high-frequency components of the collimator phase function can help reduce the extent to which the fan-out phase function is disturbed (e.g., such that the fan-out structure will no longer be periodic).

[0034] Next, as 110( Figure 3 ), determine the first DOE structure that realizes the first component C1 of the collimator phase function. Similarly, as shown in 112 ( Figure 3 ), a second DOE structure that implements the combined phase function (ie, a DOE structure corresponding to a combination of the fan-out phase function 212 (or diffuse function) and the second component C2 of the collimator phase function) is determined.

[0035] Then, as shown at 114, an optical device 10 can be fabricated, which includes a first DOE structure on its first surface 12 and a second DOE structure on its second surface 14. In some embodiments, a polymer-on-glass technology can be used to fabricate the optical device 10. For example, the device 10 can be composed of a glass substrate having DOE structures formed by nanowafer-level replication on the first surface 12 and the second surface 14.

[0036] In some embodiments, the conversion of the fan-out structure 201 into the corresponding fan-out phase function ( Figure 3 106) and then combining the fan-out phase function 212 with the second component C2 of the collimator phase function ( Figure 3 Conversely, the second component C2 of the collimator phase function can be converted to a corresponding DOE structure 204 (see, for example, Figure 5B ), and the DOE structure can be combined with the fan-out structure. That is, instead of combining the phase functions for the fan-out and the second component C2, their corresponding structures are combined. For example, the fan-out structure can be designed to be directly arranged on the structure corresponding to the second component C2 of the collimator phase function.

[0037] Although aspects of the foregoing description refer to a DOE as an example of an optical element 10, in some embodiments, the optical element 10 may be a meta-optical element (MOE). Thus, for example, in some embodiments, a device according to the present disclosure may include a meta-optical element (MOE) having a first surface and a second surface, wherein the first surface and the second surface are on opposite sides of the MOE. The first surface may be configured to collimate a light beam incident on the first surface, and the second surface may be configured to provide correction for the collimation caused by the first surface and provide optical fan-out for the light beam.

[0038] The above optical structures can be used, for example, in dot projectors for 3D sensing, LiDAR, and / or machine vision applications for consumer electronics, industrial, Internet of Things (IoT), medical, and / or automotive markets. They can be particularly suitable for industries that require excellent performance, superior light control, light weight, and compact design. Examples of other consumer products that can incorporate dot projectors include robotic vacuum cleaners and lawn mowers, machine vision applications (e.g., augmented reality and virtual reality), and autonomous guided vehicles (AGVs). In addition, in some embodiments, the optical structure can be used as a diffuser incorporated into, for example, a flood illuminator for standard imaging and / or for 3D sensing.

[0039] The subject matter and functional operations described in this specification (for example, in conjunction with Figures 3 to 7Various aspects of the subject matter described in this specification may be implemented in digital electronic circuits, or in computer software, firmware, or hardware. Thus, various aspects of the subject matter described in this specification may be implemented 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 a data processing apparatus or for controlling the operation of a data processing apparatus. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, a combination of substances that affect a machine-readable propagated signal, or a combination of one or more of them. In addition to hardware, the apparatus may include code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware.

[0040] A computer program (also referred to as a program, software, software application, script, or code) may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, subroutines, or code fragments). A computer program may be deployed to execute on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0041] The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuits (e.g., FPGAs (field programmable gate arrays) or ASICs (application specific integrated circuits)), and the apparatus can also be implemented as special purpose logic circuits.

[0042] Processors suitable for executing computer programs include, for example, both general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing 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, including, for 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 memory may be supplemented by or incorporated in special-purpose logic circuits.

[0043] Figure 8 An example of a spot projector 800 is shown. The spot projector 800 includes a substrate 802 and a light emitter 804 mounted on or integrated in 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 (e.g., infrared light) 806 generated by the light emitter 804 passes through the DOE 10 and exits the spot projector. The DOE 10 is implemented, for example, as a combination of the above Figure 1 and Figure 2 DOE 10 is arranged to intersect the path of the outgoing light 806 and is operable to collimate the light 806 and separate it into a plurality of diffraction orders 808 so that the dot projector 800 projects a dot pattern onto an object external to the projector 800 (eg, a person's face).

[0044] Although this document contains many specific implementation details, these implementation details should not be interpreted as limitations on any invention or the scope of the claims, but rather as descriptions of features specific to a particular embodiment. Certain features described in this document in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. Various modifications may be made to the foregoing examples. For example, steps indicated as being performed in a particular order may be performed in a different order or simultaneously. Therefore, other implementations are also within the scope of the claims.

Claims

1. A device comprising: an optical element having a first surface and a second surface, wherein the first surface and the second surface are on opposite sides of the optical element, The first surface is configured to collimate a light beam incident on the first surface, and The second surface is configured to provide correction for the collimation caused by the first surface and to provide at least one of optical fanning or diffusion for the light beam.

2. The device according to claim 1, wherein: The structure of the first surface operable to collimate the light beam has a greater high frequency component than the structure of the second surface operable to provide correction for the collimation caused by the first surface.

3. The device 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 correction for the collimation caused by the first surface corresponds to a second component of the phase function, wherein the maximum gradient of the first component of the phase function is less than the maximum gradient of the second component of the phase function.

4. The device 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 device according to claim 4, wherein: The maximum amplitude of the second component of the phase function is no greater than 10% of the maximum amplitude of the first component of the phase function.

6. The device according to any one of claims 1 to 5, wherein: The second surface is configured to provide an optical fan-out for the light beam, and wherein the optical fan-out is provided by a discrete periodic surface relief structure on the second surface.

7. The device according to any one of claims 1 to 5, wherein: The second surface is configured to provide diffusion for the light beam, and wherein the diffusion is provided by discrete non-periodic surface relief structures on the second surface.

8. The device according to any one of claims 1 to 6, wherein: The second surface is configured to provide an optical fan-out for the light beam, and wherein the optical fan-out is operable to split the light beam into a predetermined number of diffraction orders at respective angles.

9. The device according to any one of claims 1 to 8, further comprising: a light emitter operable to emit light toward the first surface of the optical element, The optical element is configured so that the light passes through the optical element, and the optical element projects a pattern using the light.

10. A method comprising: separating the phase function into a first component and a second component, wherein the first component represents a collimation to be achieved on a first surface of an optical element and the second component represents a collimation correction to be achieved on a second surface of the optical element; combining at least one of a fan-out phase function or a diffuse phase function with the second component of the collimator phase function to obtain a combined phase function; determining a first optical element structure corresponding to the first component of the collimator phase function; determining a second optical element structure corresponding to the combined phase function; and An optical device is fabricated, the optical device comprising a substrate having a first surface and a second surface respectively on opposite sides of the substrate, wherein the first optical element structure is on the first surface, and wherein the second optical element structure is on the second surface.

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 no greater than 10% of the maximum amplitude of the first component of the phase function.

14. The method according to any one of claims 10 to 13, wherein: The first optical element structure for collimation has more high frequency components than the second optical element structure for providing correction for the collimation.

15. The method according to any one of claims 10 to 14, comprising combining the fan-out phase function with the second component of the collimator phase function to obtain the combined phase function, the method further comprising: before combining the fan-out phase function with the second component of the collimator phase function to obtain a combined phase function, converting the fan-out structure into a corresponding fan-out phase function; as well as The corresponding fan-out phase function is then used as the fan-out phase function combined with the second component of the collimator phase function.

16. The method according to any one of claims 10 to 15, wherein: Fabricating the optical device includes forming the first optical element structure and the second optical element structure on the first surface and the second surface of the substrate respectively by nano-wafer-level replication.

17. A method comprising: separating the phase function into a first component and a second component, wherein the first component represents a collimation to be achieved on a first surface of an optical element and the second component represents a collimation correction to be achieved on a second surface of the optical element; converting the first component of the collimator phase function into a corresponding first optical element structure; converting a second component of the phase function into a corresponding second optical element structure; combining the fan-out structure with the second optical element structure to obtain a combined optical element structure; An optical device is fabricated, the optical device comprising a substrate having a first surface and a second surface respectively on opposite sides of the substrate, wherein the first optical element structure is on the first surface, and wherein the combined optical element structure is on the second surface.

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 no greater than 10% 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: Fabricating the optical device includes forming the first optical element structure and the combined optical element structure on the first surface and the second surface of the substrate respectively by nano-wafer-level replication.

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