US-12619075-B2 - Fibre couple light engine

Abstract

A light engine includes multiple laser diodes, each configured to emit laser light, and a light source unit having multiple channels, each of the channels is associated with one of the laser diodes and configured to transmit the laser light emitted from the corresponding laser diode. The channels may be, for example, fiber optic strands or optical pathways within a channeled lightguide. The light engine further includes a ferrule coupled to the light source unit and configured to receive the laser light from the light source unit and to output a collimated beam of laser light comprising each wavelength of laser light emitted by the laser diodes.

Inventors

• Daniel J. Effinger
• Benjamin Wales

Assignees

• GOOGLE LLC

Dates

Publication Date

20260505

Application Date

20211109

Claims (20)

1. 1 . A light engine comprising: a plurality of laser diodes, each laser diode of the plurality of laser diodes configured to emit laser light representative of at least a portion of an image to be displayed; a light source unit comprising a plurality of structures formed in a substrate of a waveguide, the plurality of structures being formed from areas of the substrate having a higher index of refraction than at least a portion of the substrate outside the areas and the plurality of structures forming a plurality of channels with, each channel of the plurality of channels being associated with one of the plurality of laser diodes and configured to transmit the laser light emitted from the corresponding laser diode; and an output channel formed from a convergence of the plurality of channels and configured to receive the laser light from each channel of the plurality of channels.
2. 2 . The light engine of claim 1 , further comprising a fiber optic strand optically coupling the light source unit to a ferrule.
3. 3 . The light engine of claim 2 , wherein the ferrule comprises a collimating lens.
4. 4 . The light engine of claim 1 , wherein the light source unit is contained in a hermetic housing.
5. 5 . The light engine of claim 1 , further comprising: a fiber optic strand disposed between the output channel and a ferrule, the fiber optic strand configured to optically connect the output channel to the ferrule.
6. 6 . The light engine of claim 5 , further comprising: a ball lens configured to direct light from the output channel into the fiber optic strand.
7. 7 . The light engine of claim 1 , wherein a channel of the plurality of channels is configured to combine the laser light emitted from two or more laser diodes of the plurality of laser diodes.
8. 8 . A head-mounted display (HMD) system comprising: a support structure having a front portion and at least one arm; and a light engine, housed within the support structure, comprising: a light source unit comprising: a plurality of laser diodes with each laser diode of the plurality of laser diodes configured to emit laser light representative of at least a portion of an image to be displayed; a plurality of structures formed in a substrate of a waveguide, the plurality of structures being formed from areas of the substrate having a higher index of refraction than at least a portion of the substrate outside the areas and the plurality of structures forming a plurality of channels with; each channel of the plurality of channels being associated with one of the plurality of laser diodes and configured to transmit the laser light emitted from the corresponding laser diode; and an output channel formed from a convergence of the plurality of channels and configured to receive the laser light from each channel of the plurality of channels.
9. 9 . The HMD system of claim 8 , wherein the light source unit is housed within the at least one arm and a ferrule connected to the light engine is housed within the front portion of the support structure.
10. 10 . The HMD system of claim 8 , further comprising a fiber optic strand optically coupling the light source unit to a ferrule.
11. 11 . The HMD system of claim 10 , wherein the ferrule comprises a collimating lens.
12. 12 . The HMD system of claim 8 , wherein the light source unit is contained in a hermetic housing.
13. 13 . The HMD system of claim 10 , wherein the ferrule is positioned to transmit collimated light to an optical relay housed within the support structure.
14. 14 . The HMD of claim 8 , wherein the light engine further comprises a fiber optic strand disposed between the output channel and a ferrule, the fiber optic strand configured to optically connect the output channel to the ferrule.
15. 15 . The HMD of claim 14 , wherein the light engine further comprises a ball lens configured to direct light from the output channel into the fiber optic strand.
16. 16 . The HMD of claim 8 , wherein a channel of the plurality of channels is configured to combine the laser light emitted from two or more laser diodes of the plurality of laser diodes.
17. 17 . A method comprising: providing light emitted from each laser diode of a plurality of laser diodes of a light engine to a corresponding channel of a plurality of channels, the plurality of channels comprising a plurality of structures formed in a substrate of a waveguide, wherein the plurality of structures are formed from areas of the substrate having a higher index of refraction than a portion of the substrate outside the areas; and providing the light from each channel of the plurality of channels to an output channel formed from a convergence of the plurality of channels.
18. 18 . The method of claim 17 , further comprising: providing light from the output channel to a ball lens.
19. 19 . The method of claim 18 , further comprising: directing, via the ball lens, the light from the output channel to at least one fiber optic strand.
20. 20 . The method of claim 17 , wherein the plurality of laser diodes is disposed within a hermetic housing.

Description

BACKGROUND In the field of optics, a combiner is an optical apparatus that combines two light sources, for example, environmental light from outside of the combiner and light transmitted from a micro-display and directed to the combiner via a waveguide. Optical combiners are used in wearable heads up displays (WHUDs), sometimes referred to as head-mounted displays (HMDs) or near-eye displays, which allow a user to view computer-generated content (e.g., text, images, or video content) superimposed over a user's environment viewed through the WHUD, creating what is known as augmented reality (AR) or mixed reality (MR). Some HMDs are designed to look like eyeglasses, with at least one combiner forming a lens of the eyeglasses, which are supported by a frame designed to be worn in front of a user's eyes to allow the user to view both their environment and computer-generated content projected from the combiner. Components which are necessary to the functioning of a typical HMD, such as, for example, a light engine to project computer-generated content, cameras to pinpoint physical location, cameras to track the movement of the user's eye(s), processors to power the light engine, and a power supply, are typically housed within the frame of the HMD. As an HMD frame has limited volume in which to accommodate these components, it is desirable that these components be as small as possible and configured to interact with the other components in very small volumes of space. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items. FIG. 1 shows an example display system employing a scanning-based optical system, in accordance with some embodiments. FIG. 2 illustrates a block diagram of a laser projection system that projects images directly onto the eye of a user via laser light and which can be implemented in a display system such as that shown in FIG. 1, in accordance with some embodiments. FIG. 3 shows a top view of a light engine including fiber optic strands optically coupled to laser diodes which can be employed in a laser projection system such as that shown in FIG. 2, in accordance with some embodiments. FIG. 4 shows a partial cut-away, perspective view of the light engine of FIG. 3, including in a hermetic housing, in accordance with some embodiments. FIG. 5 shows a top perspective view of a light engine employing a channeled waveguide optically coupled to laser diodes which can be employed in a laser projection system such as that shown in FIG. 2, in accordance with some embodiments. DETAILED DESCRIPTION In a conventional HMD light engine, light is emitted, collimated, and then combined by discrete components in an orthogonal manner requiring a cumbersome footprint (e.g., often at least 44 mm2). For example, a typical laser-based light engine includes at least three laser diodes, each of which provides laser light to separate collimating lenses, which then transmit the collimated laser light to a combiner component with multiple reflective surfaces positioned so as to combine the collimated laser light into one beam. The combined beam, sometimes referred to as a red-green-blue (RGB) beam, may then be directed to other components of the system, such as to an optical relay or scanning micro-electromechanical system (MEMS) mirror, in order to transmit the laser light into a combiner of the HMD and, ultimately, to a user's eye to be viewed as virtual content overlaying their environment. FIGS. 1-5 illustrate systems and methods of reducing the size and overall footprint of a light engine, for example a light engine of an HMD. The system includes a light source unit optically coupled to at least one light source, such as an edge-emitting laser diode, in order to transmit the light from the light source to a collimating lens element while reducing the overall footprint of the light engine. In an embodiment, the light source unit includes fiber optic strands, each of which is optically coupled to one light source. The fiber optic strands are bundled and terminate at a ferrule containing lens elements to combine the light from the individual fiber optic strands into a combined beam and to collimate the combined beam of light. In another embodiment, the light source unit is a lightguide having wavelength-specific channels (also referred to as a “channeled lightguide”), where each of the channels is optically coupled to a light source of the light engine in order to transmit the light from each light source to a region of the lightguide where the channels merge to combine the light from each light source into a combined beam before it is incident on a collimating lens element optically coupled to the lightguide. FIG. 1 illustrates an example display system 100 employing a scan