Illumination Assembly for Accurate Pointer Tracking
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Solution Overview
Problem
Interactive input systems employing retro-reflective materials to detect pointer contacts can inadvertently detect shadows as pointer contacts, leading to false detection and inaccurate tracking.
Innovation Solution
The system employs a specific illumination arrangement with IR LEDs positioned vertically and to the sides of imaging devices, capturing image frames with and without illumination sources to cancel out ambient light and reduce shadow effects, allowing for accurate detection of pointer edges and contact status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If retro-reflective materials are used to detect pointer contacts, then the detection range is extended, but shadow artifacts are generated causing false detection
Solution Approach 1:
The illumination system is segmented into multiple independent light sources positioned at different locations (above and to the sides of the imaging device). Each light source illuminates from a different angle, allowing the system to capture multiple views of the pointer and distinguish the actual pointer contact from shadow artifacts by analyzing the segmented illumination patterns.
Solution Approach 2:
Different regions of the imaging field receive illumination with different qualities and intensities based on their local position relative to the light sources. The pointer and its shadow exhibit different local illumination characteristics - the pointer directly blocks light from above while its shadow is illuminated from the sides, enabling differentiation through local quality analysis.
2Measurement precision
If multiple illumination sources are used to reduce shadow effects, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
Multiple illumination sources that are spatially separated are merged into a single integrated illumination assembly. The light sources are positioned in close proximity to the imaging device and work together as a unified system, reducing the overall complexity compared to having completely separate illumination systems while still providing multi-angle illumination for accurate pointer tracking.
Solution Approach 2:
The retro-reflective material serves as an intermediary that redirects light from multiple sources back toward the imaging device. This intermediary element allows the system to utilize multiple illumination sources effectively while simplifying the optical path design, as the retro-reflective material automatically returns the light without requiring complex additional optical components.
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
This approach enhances the accuracy of pointer tracking and contact detection by minimizing the impact of shadows and ambient light artifacts, improving the reliability of interactive input systems.
Implementation Method 1
retro-reflective materials to detect pointer contacts
Implementation Method 2
an array of infrared (IR) light emitting diodes (LEDs)
Implementation Method 3
the pointer occludes the infrared illumination and therefore appears as a high-contrast dark region
Data Source
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AI summary
An illumination assembly for an interactive input system (20), comprises at least one imaging device (60) capturing image frames of a region of interest; a plurality of illumination sources (84a, 84b, 84c) associated with the imaging device and being located at different positions relative to the imaging device, the illumination sources providing illumination to the region of interest; and a controller (72) communicating with the illumination sources, the controller conditioning the illumination sources so that the illumination sources provide illumination to the region of interest in succession, the timing of image frame capture by the imaging device being coordinated with the illumination pattern of the illumination sources.