Optical Illumination Switching for Stray Light Mitigation
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Solution Overview
Problem
Optical systems, particularly eye tracking systems, suffer from stray light and reflection artifacts caused by illumination sources, leading to occlusions and reduced accuracy in gaze tracking algorithms.
Innovation Solution
Implementing multiple illumination sources and using methods such as image merging, occlusion masks, and rolling shutter sensors to capture and process images with different illumination source configurations, mitigating stray light artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple illumination sources are used to illuminate the object, then the object is sufficiently illuminated for imaging, but stray light reflections and occlusions occur in the captured images
Solution Approach 1:
The set of illumination sources is divided into multiple groups (first group and second group). Different groups are activated in different image captures, allowing the system to segment the illumination function to avoid simultaneous activation of all sources that causes stray light reflections.
Solution Approach 2:
The illumination sources are activated in periodic alternating fashion - first group then second group, rather than continuously all together. This periodic activation pattern allows capturing multiple images with different illumination configurations to eliminate stray light artifacts.
2Object-affected harmful factors
If multiple images are captured with different illumination source groups to eliminate stray light, then stray light artifacts are mitigated, but the imaging process becomes more complex and time-consuming
Solution Approach 1:
Occlusion masks are generated in advance during factory calibration or startup process by capturing images with different illumination groups activated. These pre-computed masks are stored and applied during normal operation, avoiding the need to perform complex multi-image processing in real-time.
Solution Approach 2:
Instead of processing multiple raw images to eliminate stray light in real-time, the system creates occlusion masks that copy and represent the stray light patterns. These masks are then applied to subtract or remove the artifacts, simplifying the real-time processing burden.
3Productivity
If occlusion masks are generated during factory calibration or startup, then stray light artifacts are eliminated in real-time operation, but the initial setup process becomes more complex
Solution Approach 1:
The system performs self-calibration by automatically capturing images with different illumination groups activated and generating the appropriate occlusion masks without requiring manual intervention. This self-service approach simplifies the manufacturing and setup process while maintaining real-time processing efficiency.
4Object-affected harmful factors
If a rolling shutter sensor is used in interleave mode to capture images with alternating rows, then stray light reflections are reduced, but the sensor complexity and processing requirements increase
Solution Approach 1:
The sensor captures image data by segmenting it into alternating rows (odd rows from one illumination group, even rows from another). This row-level segmentation allows the system to separate and process different illumination contributions, reducing stray light artifacts while using standard rolling shutter sensor hardware.
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
Effectively eliminates stray light occlusions and artifacts, enhancing the accuracy of gaze tracking systems by maintaining feature visibility and improving algorithm performance.
Implementation Method 1
two or more illumination sources (e.g., point light sources such as light-emitting diodes (LEDs)) that illuminate an object to be imaged
Implementation Method 2
a camera configured to capture images of light from the point light sources reflected by the object when illuminated
Data Source
AI summary
Methods and apparatus for stray light mitigation in optical systems that include two or more illumination sources (e.g., point light sources such as light-emitting diodes (LEDs)) that illuminate an object to be imaged, and a camera configured to capture images of light from the point light sources reflected by the object when illuminated. To mitigate “occlusions” or artifacts caused by, for example, stray light or reflections of the illumination sources off of other components of the system, multiple images of the object are captured with different groups of the illumination sources enabled. The captured images can then be processed and merged to generate an output image with the occlusions or artifacts caused by stray light or reflections mitigated or eliminated.