Eye Tracking System Using Diffraction Polarizing Beam Splitter
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Solution Overview
Problem
Conventional polarizing beam splitter cubes in LCoS systems are heavy and restrictive, limiting the mechanical design and form factor of miniaturized reflective devices used in projection televisions and near-eye displays, and do not allow for efficient eye-tracking with broadband illumination.
Innovation Solution
The use of diffraction type polarizing beam splitters (DT-PBS) that are thin, lightweight, and flexible, enabling the redirection of polarized light and compensation for dispersion, allowing for compact and versatile optical assemblies in LCoS systems and eye-tracking applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polarizing beam splitter cubes are used in LCoS systems, then reliable polarization separation is achieved, but device weight increases and form factor is restricted
Solution Approach 1:
The patent replaces the mechanical cube-based polarizing beam splitter with a diffraction-type polarizing beam splitter that uses a thin film or plate structure. This substitution eliminates the need for bulky mechanical cube assemblies while maintaining the polarization separation function, thereby reducing weight and enabling miniaturization of the LCoS system.
Solution Approach 2:
The invention employs a thin film or plate structure for the diffraction-type polarizing beam splitter, replacing the traditional thick cube geometry. This thin-film approach maintains the essential polarization separation capability while dramatically reducing the optical assembly's form factor and weight, allowing integration into compact LCoS devices.
2Reliability
If conventional polarizing beam splitter cubes are used, then polarization separation is achieved, but mechanical design flexibility is limited
Solution Approach 1:
The diffraction-type polarizing beam splitter enables dynamic configuration of optical paths through its thin-film structure, allowing flexible mechanical design and assembly. The reduced size and simplified structure provide greater adaptability in integrating the polarization separation function into various LCoS system configurations, unlike the rigid cube-based approach.
3Reliability
If conventional polarizing beam splitter cubes are used, then polarization separation is achieved, but form factor is restricted
Solution Approach 1:
The patent implements a thin-film or plate-based diffraction-type polarizing beam splitter that maintains polarization separation capability while reducing the optical assembly volume by orders of magnitude compared to conventional cube structures. This enables miniaturization of the entire LCoS system.
Solution Approach 2:
By replacing the mechanical cube system with a thin-film diffraction-based system, the invention achieves the same polarization separation function in a much smaller volume, allowing compact integration into wearable and portable display devices.
4Reliability
If conventional polarizing beam splitter cubes are used, then polarization separation is achieved, but broadband illumination for eye tracking is not enabled
Solution Approach 1:
The diffraction-type polarizing beam splitter uses a thin-film structure that can be designed to work with broadband illumination sources. The diffraction grating structure and polarization-dependent phase modulation enable compatibility with various light wavelengths, facilitating the use of broadband LEDs and other illumination sources for eye tracking applications.
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
DT-PBS enables smaller form factors, broader optical illumination sources, and alternative projection paths in display systems, while providing effective solutions for eye-tracking systems by redirecting and compensating polarized light efficiently.
Implementation Method 1
diffraction type polarizing beam splitters (DT-PBS) that splits unpolarized light into two beams with orthogonal linear or circular polarizations and directs each beam in a different direction
Implementation Method 2
DT-PBS can extract a portion of light having a first polarization state and redirect it in transmission, for example into diffraction grating orders
Data Source
AI summary
An example eye-tracking optical assembly includes a light source for illuminating an eye, a first diffraction type polarizing beam splitter (DT-PBS), and a second DT-PBS, wherein the first DT-PBS is configured to direct, based on polarization, a first portion of light from the second DT-PBS towards an eye-tracking detector.