The present disclosure relates to semiconductor-based light emitting devices and related devices and methods of operation.
Many emerging technologies, such as Internet-of-Things (IoT) and autonomous navigation, may involve detection and measurement of distance to objects in three-dimensional (3D) space. For example, automobiles that are capable of autonomous driving may require 3D detection and recognition for basic operation, as well as to meet safety requirements. 3D detection and recognition may also be needed for indoor navigation, for example, by industrial or household robots or toys.
Light based 3D measurements may be superior to radar (low angular accuracy, bulky) or ultra-sound (very low accuracy) in some instances. For example, a light-based 3D sensor system may include a detector (such as a photodiode or camera) and a light emitting device (such as a light emitting diode (LED) or laser diode) as light source, which typically emits light outside of the visible wavelength range. A vertical cavity surface emitting laser (VCSEL) is one type of light emitting device that may be used in light-based sensors for measurement of distance and velocity in 3D space. Arrays of VCSELs may allow for power scaling and can provide very short pulses at higher power density.
Some embodiments described herein provide methods, systems, and devices including electronic circuits that provide an optical emitter having one or more light emitter elements (including one or more semiconductor lasers, such as surface- or edge-emitting laser diodes, including vertical cavity surface emitting lasers (VCSELs); generally referred to herein as emitters).
According to some embodiments, an optical emitter device includes a plurality of emitters on a first substrate; one or more alignment patterns on the first substrate, where the one or more alignment patterns are positioned relative to the plurality of emitters; and at least one optical element arranged to receive respective light emissions from the plurality of emitters, where the at least one optical element is oriented based on the one or more alignment patterns.
In some embodiments, the emitters are arranged in an array, and the one or more alignment patterns are positioned adjacent a periphery of the array.
In some embodiments, the one or more alignment patterns comprise fiducial structures that extend along the periphery of the array.
In some embodiments, the plurality of emitters are provided on an intermediate substrate, the intermediate substrate is on a surface of the first substrate, and the fiducial structures extend along edges of the intermediate substrate.
In some embodiments, the fiducial structures protrude from a surface of the first substrate.
In some embodiments, the at least one optical element comprises a second substrate having edges and/or corners that are aligned based on the one or more alignment patterns.
In some embodiments, the second substrate comprises a first surface facing the plurality of emitters and a second surface opposite the first surface, where the second surface comprises a structured optical surface.
In some embodiments, the first surface of the second substrate directly contacts one or more of the emitters.
In some embodiments, the first surface of the second substrate is separated from the emitters by a gap therebetween.
In some embodiments, one or more pedestal structures attach the second substrate to the first substrate, where a height of the one or more pedestal structures is configured to provide a portion of a spacing between the emitters and the second surface of the second substrate.
In some embodiments, an adhesive pattern is between the one or more pedestal structures and the first substrate, where a thickness of the adhesive pattern is configured to provide a portion of the spacing.
In some embodiments, one or more spacer structures are between the first substrate and the first surface of the second substrate, where a height of the one or more spacer structures is configured to provide a portion of the spacing.
In some embodiments, the one or more spacer structures is integral to the second substrate or the intermediate substrate.
In some embodiments, the one or more pedestal structures extend onto the intermediate substrate to provide a portion of the spacing.
In some embodiments, the one or more alignment patterns comprise a corner of a frame structure that is positioned adjacent the periphery of the array.
In some embodiments, a coefficient of thermal expansion (CTE) of the second substrate is greater than that of the first substrate and/or the intermediate substrate.
In some embodiments, respective local optical axes of the structured optical surface are oriented independent of respective optical axes of the plurality of emitters.
In some embodiments, the structured optical surface comprises a diffractive optical element.
In some embodiments, the first substrate and/or the intermediate substrate having the emitters thereon is a non-native substrate.
According to some embodiments, a method of fabricating an optical emitter device includes providing a plurality of emitters on a first substrate; providing one or more alignment patterns on the first substrate, where the one or more alignment patterns are positioned relative to the plurality of emitters; and arranging at least one optical element to receive respective light emissions from the plurality of emitters, where the at least one optical element is oriented based on the one or more alignment patterns.
In some embodiments, providing the emitters and providing the one or more alignment patterns comprises providing the emitters in an array on the first substrate; and providing the one or more alignment patterns adjacent a periphery of the array.
In some embodiments, providing the one or more alignment patterns comprises providing fiducial structures on the first substrate that extend along the periphery of the array.
In some embodiments, providing the emitters on the first substrate comprises providing the emitters on an intermediate substrate; and providing the intermediate substrate on a surface of the first substrate, where the fiducial structures extend along edges of the intermediate substrate.
In some embodiments, the fiducial structures protrude from a surface of the first substrate. Providing the fiducial structures may include transfer-printing the fiducial structures on the first substrate.
In some embodiments, the at least one optical element comprises a second substrate, and arranging the at least one optical element comprises aligning edges and/or corners of the second substrate based on the one or more alignment patterns.
In some embodiments, the second substrate comprises a first surface facing the plurality of emitters and a second surface opposite the first surface, where the second surface comprises a structured optical surface.
In some embodiments, the second substrate is attached to the first substrate by one or more pedestal structures, where a height of the one or more pedestal structures is configured to provide a portion of a spacing between the emitters and the second surface of the second substrate.
In some embodiments, an adhesive pattern is provided on the one or more pedestal structures and/or on the first substrate, where a thickness of the adhesive pattern is configured to provide a portion of the spacing.
In some embodiments, one or more spacer structures are provided on the first substrate, where a height of the one or more spacer structures is configured to provide a portion of the spacing. Providing the one or more spacer structures may be performed using a transfer-printing process.
In some embodiments, providing the one or more alignment patterns comprises providing a frame structure on the first substrate adjacent the periphery of the array, where the one or more alignment patterns comprise a corner of the frame structure.
In some embodiments, providing the emitters comprises transferring the emitters from a native source substrate to the first substrate or to the intermediate substrate using a transfer-printing process.
In some embodiments, the optical emitter device is configured to be coupled to a vehicle and oriented relative to an intended direction of travel of the vehicle.
Other devices, apparatus, and/or methods according to some embodiments will become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional embodiments, in addition to any and all combinations of the above embodiments, be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments of the present disclosure. However, it will be understood by those skilled in the art that the present disclosure may be practiced without these specific details. In some instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present disclosure. It is intended that all embodiments disclosed herein can be implemented separately or combined in any way and/or combination. Aspects described with respect to one embodiment may be incorporated in different embodiments although not specifically described relative thereto. That is, all embodiments and/or features of any embodiments can be combined in any way and/or combination.
Embodiments of the present disclosure describe methods for assembling optical elements and aligning optical beams generated by emitter arrays, such as VCSEL arrays, or other arrays of emitters formed or placed on a common substrate. Embodiments of the present disclosure can be applied in lidar systems, illumination systems (such as vehicle headlights) and/or other illumination imagers that may use arrays of discrete emitters, such as LEDs or VCSELs.
An example application of embodiments of the present disclosure in a lidar system or circuit 100 is shown in
The emitter module or circuit 115 may include an array of emitter elements 108 (e.g., VCSELs), a corresponding array of optical elements 112 coupled to one or more of the emitter elements (e.g., lens(es) 112, such as microlenses), and/or driver electronics 116. The optical elements 112 may be configured to provide a sufficiently low beam divergence of the light output from the emitter elements 108 so as to ensure that respective fields of illumination of either individual or groups of emitter elements 108 do not significantly overlap, and yet provide a beam divergence of the light output from the emitter elements 108 to provide eye safety to observers. In some embodiments, the emitters 108 may be provided on a non-planar (e.g., curved) or flexible substrate so as to contribute to the desired illumination pattern.
The driver electronics 116 may each correspond to one or more emitter elements, and may each be operated responsive to timing control signals with reference to a master clock and/or power control signals that control the peak power of the light output by the emitter elements 108. In some embodiments, each of the emitter elements 108 in the emitter array 115 is connected to and controlled by a respective driver circuit 116. In other embodiments, respective groups of emitter elements 108 in the emitter array 115 (e.g., emitter elements 108 in spatial proximity to each other), may be connected to a same driver circuit 116. The driver circuit or circuitry 116 may include one or more driver transistors configured to control the modulation frequency, timing and amplitude of the optical signal emission that is output from the emitters 108. The maximum optical power output of the emitters 108 may be selected to generate a signal-to-noise ratio of the echo signal from the farthest, least reflective target at the brightest background illumination conditions that can be detected in accordance with embodiments described herein.
Light emission output from one or more of the emitters 108 impinges on and is reflected by one or more targets 150, and the reflected light is detected as an optical signal (also referred to herein as a return signal, echo signal, or echo) by one or more of the detectors 119 (e.g., via receiver optics 122 and/or wavelength-selective filter(s) 121), converted into an electrical signal representation (referred to herein as a detection signal), and processed (e.g., based on time of flight) to define a 3-D point cloud representation 170 of a field of view 190.
Operations of lidar systems in accordance with embodiments of the present disclosure as described herein may be performed by one or more processors or controllers, such as the control circuit 105 of
Emitter arrays in accordance with embodiments of the present disclosure may be used in both electrically-scanning (which generate image frames by raster scanning; also referred to herein as e-scanning) and flash or staring lidar systems (where the pulsed light emitting device array 115 emits light for short durations over a relatively large area to acquire images). The description above is primarily with reference to direct ToF (dToF) lidar systems, but it will be understood that embodiments described herein can be applied to indirect ToF (iToF) lidar systems as well.
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Often the raw combined output of the emitters 108 (in lidar and/or other applications) may not be sufficiently uniform in intensity. For example, it may be desirable to homogenize and/or to shape the respective light emissions from the emitters 108 and output a single light beam or light pattern with a specific shape, such as a top hat (i.e., a near uniform intensity distribution within a given area) or other predefined spatial distribution.
Some embodiments described herein provide light emitting devices, such as surface-emitting laser diodes (e.g., VCSELs), configured as emitter arrays that include beam shaping structures that can be self-aligned with the light emitting devices to output arbitrary or desired distributions of light intensity as a function of field of view angle, using light that originates from multiple discrete light emitting devices of the array. In some embodiments, the light beam output from the beam shaping structures may define a substantially uniform intensity distribution over a field of view of the laser array. For example, the field of view angle may be about 80 degrees to about 180 degrees in some embodiments, or greater than about 150 degrees in some embodiments.
Beam shaping may be achieved using discrete optical components, such as an array of macro lenses. However, such configurations are typically large, expensive, and can require careful co-alignment of many lenses. Diffusers may also be used to shape the beam. Some diffusers may only be able to shape the beam on a single axis, e.g., the Y axis. Some diffusers may not be able to achieve a desired beam shape, e.g., top hat. Some diffusers are designed for operation with collimated beams, which may be incompatible with emitter arrays that do not emit collimated light. Integrated optical elements, such as microlenses, may also be fabricated monolithically on the emitter array. Such optical elements may have limited performance such as a limited f-number and/or a limited focal length, which may limit ability to shape the beam, e.g., to collimate the beam. Also, integrating such optical elements monolithically on the array may require technologies which may not be readily available and/or may add cost.
Structured optical surfaces (also referred to herein as patterned or structured surfaces) can be applied to control light from emitter arrays and to distribute it in a highly efficient manner. Structured surfaces as described herein may include, but are not limited to, diffractive optical elements (DOEs; such as subwavelength structured surfaces (SWS)), diffusers, microlens arrays that are formed separately from the emitter array, and polarization filters and vortex plates. These surfaces may require alignment with respect to the emitter array in order to perform as designed. Such alignment may sometimes be implemented using active alignment techniques, which may be time consuming and expensive.
Some embodiments of the present disclosure provide methods and systems for aligning optical elements (e.g., including structured surfaces) with a distributed array of emitters on a substrate in one or more dimensions, for example, along angular dimensions (e.g., Theta (θ), Phi (φ)), and linear dimensions (e.g., along X-, Y-, and/or Z-axes). In some embodiments, the emitter array can be formed or placed on multiple co-planar or co-aligned surfaces.
Devices and fabrication methods in accordance with embodiments of the present disclosure are describe below with reference to the examples of
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The fiducial marks or structures 106 may be used in a self-aligned process, to assemble the optical element 112 with a desired orientation (e.g., along angular dimensions (0, (p) and/or linear dimensions (X, Y, Z)) on and relative to the emitter array 115. For example, as shown in
In some embodiments, pressure may be applied to the second substrate 102 such that the first/lower surface directly contacts a top surface of one or more of the emitters 108. In
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Likewise, in any of the embodiments described herein, the air gap between the emitter array 115 and the beam shaping optic 112 may be filled with transparent optical quality silicone (or other material with a relatively high refractive index n) to protect the assembly from condensed moisture and to improve the optical transmission through the assembly. For example, a higher index material (e.g., 1.5) in comparison to air (1.0) may be used to fill the gap(s) between the emitters 108 and/or between the emitters 108 and the second substrate 102 in some embodiments.
Lidar systems and arrays described herein may be applied to ADAS (Advanced Driver Assistance Systems), autonomous vehicles, UAVs (unmanned aerial vehicles), industrial automation, robotics, biometrics, modeling, augmented and virtual reality, 3D mapping, and security. In some embodiments, the emitter array may include a non-native substrate that is different from a source wafer or substrate on which the emitters were formed (e.g., a curved or flexible substrate) having thousands of discrete emitter elements electrically connected in series (e.g., anode-to-cathode) and/or parallel thereon, with the driver circuit implemented by driver transistors integrated on the non-native substrate adjacent respective rows and/or columns of the emitter array, as described for example in U.S. Patent Application Publication No. 2018/0301872 to Burroughs et al., the disclosure of which is incorporated by reference herein. Beam shaping may also be achieved using optical elements and associated structures as described as described for example in U.S. Patent Application Publication No. 2018/0301874 to Burroughs et al., the disclosure of which is incorporated by reference herein.
Various embodiments have been described herein with reference to the accompanying drawings in which example embodiments are shown. These embodiments may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough and complete and fully conveys the inventive concept to those skilled in the art. Various modifications to the example embodiments and the generic principles and features described herein will be readily apparent. In the drawings, the sizes and relative sizes of layers and regions are not shown to scale, and in some instances may be exaggerated for clarity.
The example embodiments are mainly described in terms of particular methods and devices provided in particular implementations. However, the methods and devices may operate effectively in other implementations. Phrases such as “example embodiment”, “one embodiment” and “another embodiment” may refer to the same or different embodiments as well as to multiple embodiments. The embodiments will be described with respect to systems and/or devices having certain components. However, the systems and/or devices may include fewer or additional components than those shown, and variations in the arrangement and type of the components may be made without departing from the scope of the inventive concepts.
The example embodiments will also be described in the context of particular methods having certain steps or operations. However, the methods and devices may operate effectively for other methods having different and/or additional steps/operations and steps/operations in different orders that are not inconsistent with the example embodiments. Thus, the present inventive concepts are not intended to be limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features described herein.
It will be understood that when an element is referred to or illustrated as being “on,” “connected,” or “coupled” to another element, it can be directly on, connected, or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly on,” “directly connected,” or “directly coupled” to another element, there are no intervening elements present.
It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower”, can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below.
The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “include,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Embodiments of the disclosure are described herein with reference to illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.
Unless otherwise defined, all terms used in disclosing embodiments of the invention, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and are not necessarily limited to the specific definitions known at the time of the present invention being described. Accordingly, these terms can include equivalent terms that are created after such time. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the present specification and in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entireties.
Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments of the present invention described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.
Although the invention has been described herein with reference to various embodiments, it will be appreciated that further variations and modifications may be made within the scope and spirit of the principles of the invention. While specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the present invention being set forth in the following claims.
This application claims priority from U.S. Provisional Patent Application Ser. No. 63/104,731, filed Oct. 23, 2020, the disclosure of which is incorporated by reference herein in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2021/056217 | 10/22/2021 | WO |
Number | Date | Country | |
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63104731 | Oct 2020 | US |