Waveguide Incoupler Alignment to Minimize Double-Bounce Loss
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Solution Overview
Problem
In wearable heads-up displays (WHUDs), light loss due to double-bounce effects and varying bounce separation spacing within waveguides leads to reduced brightness and non-uniform color saturation in displayed images, caused by different diffraction angles of light wavelengths.
Innovation Solution
Aligning the edges of laser light beams emitted by laser diodes at a tangent with the edge of the waveguide incoupler to minimize double-bounces and bounce separation spacing, using a beam combiner with reflective surfaces to direct light beams into the waveguide without overlapping paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light is transmitted through the waveguide using conventional alignment, then the light path is established, but light loss occurs due to double-bounce effects and varying bounce separation spacing
Solution Approach 1:
The patent applies asymmetry by offsetting the laser light beams from a concentric arrangement to a non-concentric arrangement. Specifically, the beams are positioned such that their edges are tangent to the incoupler edge, creating an asymmetric configuration that minimizes double-bounce effects. This asymmetric alignment reduces light loss while maintaining proper optical coupling into the waveguide.
Solution Approach 2:
The patent applies local quality by optimizing the alignment of specific regions of the light beams rather than treating them uniformly. The edges of the laser light beams are specifically aligned to be tangent with the incoupler edge, while the centers of the beams are offset. This localized optimization at the beam edges minimizes bounce separation spacing and double-bounce effects in critical regions.
2Productivity
If multiple laser light beams are combined using a beam combiner, then light efficiency improves, but color uniformity deteriorates due to varying bounce separation spacing
Solution Approach 1:
The patent uses asymmetric positioning of multiple laser light beams relative to each other and to the incoupler. Instead of concentric alignment, the beams are offset and arranged so their edges are tangent to the incoupler edge. This asymmetric configuration equalizes the bounce separation spacing for different wavelengths, improving color uniformity while maintaining high light efficiency through effective beam combining.
3Device complexity
If the laser light beams are aligned concentrically, then the optical path is simplified, but double-bounce effects increase causing light loss
Solution Approach 1:
The patent deliberately introduces asymmetry into the optical path by offsetting the laser light beams from concentric alignment. The beams are positioned in a non-concentric arrangement where their edges are tangent to the incoupler edge, creating an asymmetric configuration that reduces double-bounce effects. Although this increases optical path complexity slightly, it significantly reduces light loss and improves overall system efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces light loss and enhances color uniformity in displayed images by minimizing double-bounces and bounce separation spacing, improving the overall image quality in WHUDs.
Implementation Method 1
using a beam combiner with reflective surfaces to direct light beams into the waveguide
Implementation Method 2
a waveguide having an incoupler to direct light into the waveguide and an outcoupler to direct light from the waveguide
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Systems and methods to reduce diffraction-angle effects, such as instances of double-bounces and bounce separation spacing effects in a laser projection system (200) including an optical engine (202) with laser diodes (418) configured to emit light beams of different wavelengths and a beam combiner (224) having reflective surfaces (504) each configured to receive one of the light beams from one of the laser diodes and to reflect the received light beam such that an edge of the reflected light beam lies on a tangent (502] common to the other light beams reflected from the other reflective surfaces. The laser projection system may be implemented in head-mounted display (HMD) including a waveguide (205) having an incoupler (212) to receive the combined light beam, where an edge of the incoupler corresponds to the tangent on which the edges of the plurality of light beams are aligned.