Waveguide illumination system

Abstract

An illumination system employing a waveguide. Light received from an edge or an end of a waveguide is propagated in response to transmission and total internal reflection. Light deflecting elements distributed along the propagation path of light continuously change the out-of-plane propagation angle of light rays and cause decoupling of portions of the propagated light from the core of the waveguide at different distances from the light input edge or end. Light escapes from the waveguide into an intermediate layer at low out-of-plane angles and is further redirected by light extraction features out of the system. In one embodiment, the illumination system is configured to emit collimated light. In one embodiment, the illumination system includes shallow surface relief features. In one embodiment, the light deflecting elements include forward-scattering particles distributed throughout the volume of the waveguide. Additional collimating and non-collimating illumination units and methods are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from U.S. provisional application Ser. No. 61 / 563,018 filed on Nov. 22, 2011, incorporated herein by reference in its entirety, and from U.S. provisional application Ser. No. 61 / 648,236 filed on May 17, 2012, incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not ApplicableINCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC[0003]Not ApplicableNOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION[0004]A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright right...

AI Technical Summary

Benefits of technology

[0019]An advantage of the present system is to provide controlled light extraction through a designated surface of the waveguide while minimizing light loss and controlling the angular distribution of the extracted light. Light is extracted from the waveguide into an intermediate layer by means of incremental deflections from the prevailing propagation direction after which it is further redirected out of the waveguide. A two-stage light extraction process enables the directionality of the emitted light and minimizes light spillage into non-functional directions.

[0033]In at least one embodiment, the waveguide illumination system of this invention is configured as an edge-lit front light for an image screen which provides high optical transparency and image fidelity while efficiently illuminating the underlying image.

[0035]In at least one embodiment, the waveguide illumination system of this invention is incorporated into a lighting luminaire with improved beam directionality. According to an aspect, the edge-lit waveguide panel distributes and emits light from a broad-area surface of the panel in the form of a collimated beam.

Problems solved by technology

In this case, TIR will not occur and the respective rays may exit from the waveguide through the unwanted face (see FIG. 4), resulting in light loss and reduced system efficiency.

However, doing so will introduce reflection losses at the mirrored surface compared to the lossless TIR and will also add fabrication steps, such as fabricating a mask, applying the mask to the waveguide surface with precision alignment, vacuum metallization, etc.

The lack of beam directionality hampers the utility of conventional waveguide illumination systems in the applications requiring at least some degree of light collimation.

This makes the conventional devices ill suited for the front light applications in which an edge-lit lighting panel is positioned in front of a viewable screen or image print.

As a result, the visual appearance and resolution of the print may deteriorate.

Since such light has about equal chance to escape through either front or rear surface, at least a substantial portion of it will exit from the unwanted side of the waveguide resulting in energy loss and considerable glare.

The prior-art lighting panels employing light extraction features based on light scattering rather than on reflection typically introduce even more unwanted glare and light spillage due to the uncontrolled nature of light scattering mechanism.

Additionally, such lighting panels are usually characterized by a relatively high level of opacity and either substantially opaque or can be translucent at best, but not fully transparent, which inhibits the basic light guiding function of the panel.

Yet further, when the conventional planar waveguide employing light extracting features (such as surface microstructure or scattering elements) is lit from an edge, at least a portion of light extracted by these features is emitted towards the viewer which substantially degrades the contrast and visibility of the bodies or images disposed behind the waveguide.

Besides sometimes being characterized by reduced optical qualities or light spillage, the conventional systems employing relatively deep cuts, notches or grooves may also be affected by at least some loss of structural strength and rigidity compared to a smooth-surface panel having no such microstructures.

Images