Optical elements for beam-shaping and illumination
An example device may include a light source, an optical element, and, optionally, an encapsulant layer. A light beam generated by the light source may be received by the optical element and redirected towards an illumination target, such as an eye of a user. The optical element may include a material, for example, with a refractive index of at least approximately 2 at a wavelength of the light beam. The light source may be a semiconductor light source, such as a light-emitting diode or a laser. The optical element may be supported by an emissive surface of the light source. Refraction at an exit surface of the optical element, and/or within a metamaterial layer, may advantageously modify the beam properties, for example, in relation to illuminating a target. In some examples, the light source and optical element may be integrated into a monolithic light source module.
1. A device, comprising:
a plurality of light source modules, wherein each light source module of the plurality of light source modules comprises:
a light source configured to emit a light beam through a light-emissive surface; and
an optical element supported by the light-emissive surface and configured to receive the light beam along a first direction and redirect the light beam along a second direction,
wherein:
the second direction is different from the first direction;
the optical element comprises a material that has a refractive index of greater than 2 at a wavelength of the light beam;
a deviation angle between the first direction and the second direction for each light source module of the plurality of light source modules is based on a location within the device and configured so that a target is illuminated by all light source modules of the plurality of light source modules;
the device is a wearable device;
the target includes an eye of a user when the user wears the device; and
each optical element of the plurality of light source modules has an aspheric surface configured to provide the deviation angle based on a lateral offset from a center of the eye.
2. The device of claim 1 , wherein the light source and the optical element are integrated into a monolithic light-emitting module.
3. The device of claim 1 , wherein the material comprises a semiconductor.
4. The device of claim 1 , wherein the material comprises at least one of an arsenide semiconductor, a phosphide semiconductor, or a nitride semiconductor.
5. The device of claim 1 , wherein the light source comprises a laser.
6. The device of claim 5 , wherein the laser is a vertical cavity surface-emissive laser.
7. The device of claim 5 , wherein the optical element is formed on the light-emissive surface of the laser.
8. The device of claim 1 , wherein:
the device is a head-mounted device;
the device comprises an eye tracker; and
the eye tracker comprises the light source.
9. The device of claim 8 , wherein the device further comprises a light sensor configured to detect a reflection of the light beam from the eye.
10. The device of claim 1 , wherein the device is an augmented reality device or a virtual reality device.
11. The device of claim 1 , wherein the optical element comprises a metamaterial layer.
12. The device of claim 11 , wherein the metamaterial layer comprises an arrangement of nanostructures.
13. The device of claim 12 , wherein each nanostructure of the arrangement of nanostructures has a nanostructure parameter, wherein the nanostructure parameter has a spatial variation as a function of position within the metamaterial layer, the spatial variation being configured to improve illumination uniformity of the target illuminated by the light beam.
14. The device of claim 13 , wherein the nanostructure parameter includes at least one of: a lateral dimension, a cross-sectional area, a length dimension, a composition, a nanostructure spacing, a cross-sectional shape, a cross-sectional shape anisotropy, a cross-sectional uniformity, a taper, a nanostructure refractive index, a nanostructure refractive index anisotropy, a coating thickness, a hollow core thickness, a volume fraction of at least one component, or an orientation.
15. The device of claim 13 , wherein the arrangement of nanostructures comprises nanopillars, and the nanostructure parameter is a nanopillar diameter.
16. The device of claim 13 , wherein the arrangement of nanostructures comprises polarization-sensitive nanostructures.
17. A method, comprising:
fabricating a laser having an emissive surface;
forming a layer on the emissive surface of the laser;
forming a resist layer on the layer, the resist layer having a shape determined by a spatially non-uniform thickness of the resist layer;
etching the shape of the resist layer into the layer to form an optical element having a shaped exit surface, thereby forming a light source module including the laser and the optical element; and
fabricating a device comprising a plurality of light source modules including the light source module,
wherein:
the optical element is supported by the emissive surface of the laser, receives light from the laser, and is configured to redirect the light through a deviation angle by refraction through the shaped exit surface to illuminate a target;
the deviation angle for each light source module of the plurality of light source modules is based on a location within the device and configured so that the target is illuminated by the plurality of light source modules;
the device is a wearable device;
the target includes an eye of a user when the user wears the device; and
each optical element of the plurality of light source modules has an aspheric surface configured to provide the deviation angle based on a lateral offset from a center of the eye.
18. The method of claim 17 , wherein the shaped exit surface is an oblique surface, and the optical element comprises a prism.
19. The method of claim 17 , wherein the shaped exit surface includes a curved exit surface.
20. The method of claim 17 , wherein forming the layer on the emissive surface of the laser comprises forming a passivation layer on the emissive surface and then forming the layer on the passivation layer.