Polarization-Stabilized VCSEL Illuminator for Eye Tracking
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Solution Overview
Problem
Eye tracking systems face challenges with illuminators that emit light with undefined or fluctuating polarization states, leading to inconsistent optical power levels, which affect the accuracy of eye position and orientation tracking due to polarization-dependent optical elements and the eye's reflection characteristics.
Innovation Solution
Incorporating a semiconductor emitter chip with a polarization-selective element, such as a grating structure or polarization-selective resonators, coupled with a beam redirecting optic to stabilize the polarization state of the emitted light beam, ensuring constant optical power and accurate eye tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional illuminator without polarization control is used, then the device complexity is reduced, but the optical power level becomes inconsistent due to fluctuating polarization states
Solution Approach 1:
A polarization-selective element is introduced as an intermediary component between the light source and the optical system. This element selectively transmits or blocks specific polarization states, thereby stabilizing the polarization output and ensuring consistent optical power levels without requiring complex active control mechanisms.
Solution Approach 2:
The polarization state of the emitted light is controlled by changing the physical or chemical parameters of the polarization-selective element, such as its orientation, material properties, or structural configuration. This allows stable polarization output to be achieved through passive parameter optimization rather than active control.
2Measurement precision
If polarization-stabilizing components are added to the illuminator, then the accuracy of eye tracking improves, but the device complexity increases
Solution Approach 1:
The polarization-selective element acts as a mediator that prepares the light with stable polarization characteristics before it interacts with the eye and optical elements. This preprocessing of the light ensures that subsequent measurements are not affected by polarization variations, thereby improving tracking accuracy with minimal added complexity.
Solution Approach 2:
The illuminator is segmented into distinct functional modules: the light source, the polarization-selective element, and the beam-shaping optics. This modular segmentation allows each component to be optimized independently, with the polarization-selective element specifically addressing the polarization stability requirement without affecting other parts of the system.
3Ease of manufacture
If the illuminator emits light with undefined polarization state, then the manufacturing process is simpler, but the optical power level fluctuates due to polarization-dependent elements
Solution Approach 1:
The polarization-selective element is integrated into the manufacturing process as a standard component that can be aligned and secured during assembly. This approach maintains ease of manufacture by using off-the-shelf polarization elements while ensuring that the final product delivers stable optical power levels.
Solution Approach 2:
During manufacturing, the polarization-selective element is oriented at specific angles or configured with particular material properties to match the requirements of the optical system. This parameter optimization is performed once during fabrication, after which the system maintains stable polarization output without requiring further adjustments.
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 solution provides a stable polarization state for the light beam, maintaining consistent optical power and improving the accuracy of eye position and orientation tracking in eye tracking systems, even when encountering polarization-dependent optical elements and the eye's reflection.
Implementation Method 1
a polarization-selective element optically coupled to the semiconductor emitter chip for defining a polarization state of the light beam emitted thereby
Implementation Method 2
a beam redirecting optic coupled to the polarization-selective element for receiving and at least one of collimating or redirecting the light beam
Data Source
AI summary
An illuminator includes a semiconductor emitter chip, e.g. a VCSEL chip, configured for emitting a light beam. A polarization-selective element is optically coupled to the semiconductor emitter chip for defining a polarization state of the emitted light beam. A beam redirecting optic is coupled to the polarization-selective element for receiving and at least one of collimating or redirecting the emitted light beam. The polarization-selective element, e.g. a polarization-selective optical feedback element for VCSEL, defines a polarization state of the emitted light beam, thereby stabilizing output optical power of light beam propagated through the beam redirecting optic. A light beam of a constant optical power and a well-defined polarization state may be used as an illumination source for an eye-tracking system.