Polarized IR Eye Camera Optics for Glare-Free Iris Imaging
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Solution Overview
Problem
Conventional eye camera systems using non-polarized light face challenges such as reflections from eyelashes and eyelids, saturation due to glints, and low contrast in iris patterns, which hinder iris recognition and eye/gaze tracking, especially for users with contact lenses or smooth corneas.
Innovation Solution
The use of polarized infrared light in eye camera systems, achieved through LED packages with optical filters and polarizing elements, reduces reflections and enhances contrast, improving iris recognition and eye/gaze tracking by illuminating the user's eyes with polarized IR light and capturing images with polarized cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-polarized light is used for illumination, then the eye camera system can capture images of the user's eye, but reflections from eyelashes and eyelids are captured in the images making iris recognition and eye/gaze tracking more difficult
Solution Approach 1:
The patent changes the polarization state parameter of the illumination light from non-polarized to polarized. By using polarized IR light for illumination and placing a polarizer in the camera optical path, the system selectively blocks reflected light from eyelashes and eyelids while allowing light from the iris to pass through, thereby improving iris recognition accuracy
Solution Approach 2:
The patent introduces a polarizer as an intermediary optical element in the camera light path. This polarizer acts as a mediator that selectively transmits or blocks light based on its polarization state, separating the desired iris signal from unwanted reflections off eyelashes and eyelids
2Reliability
If non-polarized illumination sources are used, then the eye can be illuminated, but glints from the illumination sources fall into the iris region causing saturation making the region not useful for iris recognition
Solution Approach 1:
The patent changes the polarization state of the illumination light from non-polarized to polarized. The polarized illumination combined with a polarizer in the camera path creates a polarization filter effect that eliminates specular glints from the iris region while maintaining sufficient illumination for capturing iris patterns, preventing saturation
Solution Approach 2:
The patent converts the harmful effect of illumination glints into a beneficial filtering mechanism. By using polarized light, the system causes glints to become polarized in a specific direction that can be blocked by the camera polarizer, transforming the harmful saturation effect into a useful signal rejection mechanism
3Measurement precision
If non-polarized light is used for illumination, then the eye camera system can capture images, but the contrast of iris patterns is low for some eyes
Solution Approach 1:
The patent changes the polarization state of illumination light to polarized. This parameter change enhances the contrast of iris patterns by selectively transmitting light that reflects off the iris tissue while blocking light that reflects off surrounding structures, thereby improving measurement precision for iris recognition
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 polarized light significantly reduces reflections and improves contrast, enhancing the performance of iris recognition and eye/gaze tracking functions by minimizing glare and improving image quality.
Implementation Method 1
at least one light polarizing element may be located in the path of the light which is used to capture images of the user's eye
Implementation Method 2
Using polarized light in the eye camera system may overcome these and other limitations of using non-polarized light by reducing or eliminating reflections
Data Source
AI summary
Methods and apparatus for using polarized light (e.g., infrared (IR) light) to improve eye-related functions such as iris recognition. An eye camera system includes one or more IR cameras that capture images of the user's eyes that are processed to perform iris recognition, gaze tracking, or other functions. At least one polarizing element may be located in the path of the light which is used to capture images of the user's eye. The user's eye may be illuminated by IR light emitted by one or more LEDs. At least one of the LEDs may be an LED with a polarizing filter. Instead or in addition, at least one polarizer may be located at the eye camera sensor, in the eye camera optics, or as or in an additional optical element located on the light path between the eye camera and the user's eye.