NIR-Transparent OLED Coating for Behind-Display Eye Tracking
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Solution Overview
Problem
Existing organic light emitting diode (OLED) displays in head-mounted displays (HMDs) face challenges in eye tracking due to camera placement issues, where cameras either block the display or are obstructed by the opaque coating, hindering optimal pupil image capture for augmented and virtual reality applications.
Innovation Solution
Incorporating a substrate coating made of IR-transparent materials like Zinc Selenide or Zinc Sulfide that allows a pupil tracking camera to be mounted behind the display, enabling IR light transmission while blocking visible light, along with IR illumination lamps and controlled camera activation during null periods to capture pupil images without interfering with active frame rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the camera is placed between the substrate and the eye, then eye tracking can be performed, but the camera blocks the display
Solution Approach 1:
The coating on the substrate has different optical properties for different wavelengths: it is opaque to visible light (blocking display light from reaching the camera) but transparent to near-infrared light (allowing pupil images to reach the camera). This local quality differentiation resolves the contradiction by making the coating selectively transparent based on wavelength.
Solution Approach 2:
The IR-transparent coating acts as an intermediary between the display and the camera. It mediates the interaction by blocking visible light from reaching the camera while allowing IR light to pass through, thus enabling the camera to capture pupil images without being blocked by the coating and without the camera blocking the visible display.
2Illumination intensity
If the camera is placed on the outside of the display, then the display is not blocked, but the opaque coating blocks pupil images from reaching the camera
Solution Approach 1:
The coating is designed with wavelength-selective transparency: opaque to visible light (maintaining display appearance) and transparent to near-infrared light (allowing pupil images to pass through to the externally placed camera).
Solution Approach 2:
The coating effectively changes its optical transparency based on the wavelength of light, being opaque to visible wavelengths (maintaining the black appearance when pixels are inactive) and transparent to infrared wavelengths (allowing pupil tracking).
3Duration of action of moving object
If the camera is active during image rendering, then continuous eye tracking is possible, but interference with image rendering occurs
Solution Approach 1:
The camera is activated periodically during null periods between frame renders rather than continuously. This periodic activation allows eye tracking to occur during intervals when the display is not updating, eliminating interference with image rendering while maintaining sufficient tracking continuity through high-frequency periodic sampling.
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
Enables effective eye tracking by allowing IR light to pass through the coating for pupil imaging while maintaining display functionality, improving the accuracy and efficiency of eye tracking in HMDs for extended reality applications.
Implementation Method 1
The coating has infrared (IR)-transparent material that is transparent to at least near infrared (NIR) radiation but opaque to visible light
Implementation Method 2
organic light emitting diode (OLED) display
Implementation Method 3
at least one IR illumination lamp is configured to emit IR toward an eye of a wearer of the apparatus
Data Source
AI summary
A micro-OLED display includes a substrate with a coating made of IR-transparent material such as Zinc Selenide or Zinc Sulfide to allow a pupil tracking camera, which may include photodiodes, to be mounted directly behind the display. The coating is transparent to near infrared (NIR) radiation but opaque to visible light.