Directionally-Sensitive Optical Element for SAW 3D Display Contrast
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Solution Overview
Problem
Surface acoustic wave (SAW) modulator-based three-dimensional display systems suffer from undesired spurious light projection along unintended axes, leading to reduced contrast in horizontal parallax-only light field projection systems due to the directional diffuser's inability to effectively block stray light components.
Innovation Solution
Incorporating a directionally-sensitive optical element, such as an aperture grille or microlouver material, in front of the two-dimensional emitter array to block stray light along specific axes, thereby improving contrast by masking unwanted light before it reaches the diffuser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a directional diffuser is used to broaden the vertical extent of the exit pupil, then the vertical viewing angle is improved, but stray light from unintended axes is spread and contrast deteriorates
Solution Approach 1:
The directional diffuser is segmented into multiple sections, each with different diffusion characteristics. The first section has a diffusion angle optimized for blocking stray light from the first axis, while the second section has a diffusion angle optimized for blocking stray light from the second axis. This segmentation allows each section to selectively manage stray light from specific directions while preserving the desired light field expansion.
Solution Approach 2:
Different sections of the directional diffuser are assigned different local optical properties. Specifically, the diffusion angles and transmission characteristics are locally optimized for each section to address the stray light problem from different axes. This local quality differentiation enables the system to maintain high contrast in the desired viewing direction while effectively blocking stray light from unintended axes.
2Manufacturing precision
If many SAW modulators are integrated to construct a smooth light field, then the light field quality is improved, but the system complexity and stray light generation increase
Solution Approach 1:
The directional diffuser acts as an intermediary element positioned between the SAW modulator array and the viewer. It mediates the light field by selectively diffusing desired light to broaden the exit pupil while simultaneously blocking stray light from unintended axes. This intermediary function allows the system to maintain high light field quality from multiple modulators while filtering out the spurious light they generate.
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
The implementation of a directionally-sensitive optical element significantly enhances image contrast by selectively blocking stray light, improving the vertical extent of the light field projection while preserving horizontal perspective information.
Implementation Method 1
a surface acoustic wave diffracts light propagating in a waveguide and causes at least some of the light to change from a guided mode to a leaky mode that exits the waveguide
Implementation Method 2
Surface acoustic wave (SAW) optical modulator systems are being proposed as an optical engine for three dimensional (3D) display systems
Implementation Method 3
a directionally-sensitive optical element, such as an aperture grille, with the pitch between apertures of the aperture grille matching a pitch between rows of emitters of the emitter array
Data Source
AI summary
A light field generation system includes a two dimensional emitter array for projecting light and a directionally-sensitive optical element in front of the emitter array but before a directional diffuser. Certain classes of emitters are intended to project information principally along one axis (e.g. amplitude modulated in the horizontal plane, i.e. so that each eye sees a potentially different image) and are the basis of horizontal-parallax-only (HPO) displays. Examples include surface acoustic wave (SAW) modulators, such as edge-emitting or surface-emitting modulators. They often project undesired or stray light along directions along a different axis (e.g. vertically) and the diffuser will also spread the visibility of the stray light field components. Thus, the directionally-sensitive optical element will improve contrast in this scenario.