Structured light projector including an integrated metalens and diffractive optical element

An apparatus that includes a structured light projector which includes a light source, a metalens, and a diffractive optical element (DOE) multiplier. Each of the metalens and the DOE multiplier is integrated onto the light source. The structured light projector is operable such that light beams produced by the light source pass through the metalens and the DOE multiplier.

FIELD OF THE DISCLOSURE

The present disclosure relates to structured light projectors.

BACKGROUND

Structured light involves projecting a known pattern of light onto to a scene. The structured illumination may have any regular shape, e.g. lines or circles, or may have a pseudo-random pattern such as pseudo-random dot patterns or further may have pseudo-random shapes or sizes of shapes, depending on the application. A light pattern created in the scene by the structured light makes it possible to distinguish objects according to their distance from the apparatus emitting the structured light.

SUMMARY

The present disclosure describes an apparatus that includes a structured light projector. The structured light projector includes a light source, a metalens, and a diffractive optical element (DOE) multiplier. Each of the metalens and the DOE multiplier is integrated onto the light source. The structured light projector is operable such that light beams produced by the light source pass through the metalens and DOE multiplier.

Some implementations include one or more of the following features. For example, in some instances, the DOE multiplier and the metalens are disposed on the same surface or in the same plane as one another. In other instances, the DOE multiplier and the metalens are disposed in different planes from one another. In some cases, the DOE multiplier is disposed directly on an output face of the light source.

A spacer can be provided on the DOE multiplier, such that the metalens is disposed on a surface of the spacer and such that the spacer separates the metalens from the DOE multiplier. In some cases, the DOE multiplier and metalens are on a surface of the spacer such that the spacer separates the DOE multiplier and metalens from the output face of the light source. The spacer can be composed, for example, of an epitaxial or polymer layer. The spacer may be bonded, for example, to the output face of the light source. In some instances, a lateral dimension of the metalens is less than a corresponding lateral dimension of the DOE multiplier. In some implementations, an envelope profile of the metalens is the same as a two-dimensional grating profile of the DOE multiplier. In some case, the surface of the spacer on which the DOE multiplier and metalens are disposed is larger than the output face of the light source.

In some implementations, the light source include one or more VCSELs.

In some instances, by integrating the metalens and the DOE multiplier onto the light source, a highly compact projector can be obtained. This can be important, for example, where the structured light projector is incorporated into a portable computing device such as a smartphone.

Other aspects, features and advantages will be readily apparent from the following detailed description, the accompanying drawings, and the claims.

DETAILED DESCRIPTION

FIG. 1illustrates an example of a structured light projector20that includes a metalens and a diffractive optical element (DOE) multiplier, both of which are integrated onto a light source, such as a low divergence vertical cavity surface emitting laser (VCSEL) or array of VCSELs. The DOE multiplier is operable to multiply each source element beam by splitting the beams in an energy efficient manner to produce multiple beams from each source element (e.g., VCSEL). Thus, the DOE multiplier operates as a beam splitter that separates each incident beam into multiple non-overlapping beams. The intervals, intensity ratios and symmetrical distribution of the beams are set by the periodic microstructures of the DOE multiplier. The divergence angle, diameter and polarization of the incident beam remain substantially unchanged. The DOE multiplier can diffract the VCSEL source element beam into a regular or non-regular angular array of beams, depending on the particular implementation. On the other hand, the metalens is operable to imprint an arbitrary phase profile on the individual beams. The metalens defines a metasurface composed of sub-wavelength-spaced phase shifters at an interface, which allows for tight control over the light properties. In combination, the DOE multiplier and metalens allow the projector20to generate a structured light pattern (e.g. a pattern of spots). By integrating the metalens and the DOE multiplier onto the light source, a highly compact projector can be obtained in some instances.

As shown inFIG. 1, at least some of the light beams22produced by the projector20may be incident on a scene24. The light beams22impinging on the scene24create a pattern26that can be sensed and processed, for example, by a structured light imaging system to derive a three-dimensional depth map of one or more objects in the scene. Particular examples and further details of the structured light projector20according to some implementations are described below.

In some instances, as shown inFIG. 2, the DOE multiplier30and the metalens32are disposed in different planes from one another. In the illustrated example, the DOE multiplier30is fabricated directly on an output face of a VCSEL or an array34of VCSELs disposed on a submount36. A regrown epitaxial layer or a spin-on polymer layer, for example, can be provided as a spacer38on the DOE multiplier30. The metalens40then can be fabricated on the surface of the spacer38to form a fully integrated structured light projector20in which the VCSEL beams pass through the DOE multiplier30and the metalens32. The foregoing configuration, in which the DOE multiplier30is in a plane closer to the array34of VCSELs than is the plane of the metalens32, can be useful for projecting a relatively small field of illumination. To project a larger field of illumination, the metalens32can be disposed in a plane closer to the array34of VCSELs than is the plane of the DOE multiplier30.

In other instances, as shown inFIGS. 3 and 4, both the DOE multiplier40and the metalens42are manufactured on the same surface and may be disposed in the same plane. For example, the DOE multiplier40and metalens42can be fabricated on the surface of a glass or other transparent spacer48, that subsequently is attached (e.g., bonded) directly to the output face of a VCSEL or an array44of VCSELs disposed on a submount46. In some instances, the spacer48initially may be attached to the output face of the VCSEL(s) and the DOE multiplier and metalens subsequently are formed on the spacer surface.

Typically, the lateral dimension of the metalens42(e.g., on the order of 100 nm) is much less than the corresponding lateral dimension of the DOE multiplier40. In some cases, the envelope profile of the metalens42is about the same as the two-dimensional grating profile of the DOE multiplier40. The surface of the spacer48on which the DOE multiplier40and metalens42are formed can be larger than the output face of the VCSEL or VCSEL array, thereby providing sufficient surface area for both the DOE multiplier40and metalens42to be formed on the same surface. In a particular example, the beam divergence, after collimation by the metalens32, is about 4 mrad, and the beam diameter is about 7-8 μm. For such values, a lens focal length (FL) of about 2 mm is suitable. The thickness of the spacer48should be about FL*n, where n is the refractive index of the spacer.

In some implementations, the metalenses32has a flat surface composed of nanostructures. In some instances, for example, the metalens32is composed of nanofins. The desired phase can be imparted, for example, by appropriate rotation of the nanofins.

In implementations in which the light source includes an array of light emitting elements, the VCSEL array layout can take the form of a regular or non-regular array. In some cases, there may groups of regular and/or non-regular arrays. The array can have separately addressable source elements or groups of source elements (e.g., VCSELs). Further, a respective DOE multiplier can be integrated onto the face of each light source element (e.g., VCSEL). Each DOE multiplier can be designed to produce an array of multiple beams with the same layout or each element can have a different structure to produce a different multiplying structure of each VCSEL source element. Further, in some cases, a respective metalens structure is provided for each VCSEL element. Alternatively, a distributed metalens structure can be provided to cover multiple VCSEL elements.

The structured light projectors described here can be integrated into a wide range of small electronic devices, such as smart phones, wearables, bio devices, mobile robots, surveillance cameras, camcorders, laptop computers, and tablet computers, among others.

Various modifications can be made within the spirit of this disclosure. For example, certain features that are described in this specification in the context of separate embodiments also can be implemented in combination in the same embodiment. Conversely, various features that are described in the context of a single embodiment also can be implemented in multiple embodiments separately or in any suitable sub-combination. Accordingly, other implementations are within the scope of the claims.