Occlusion-Based Height Estimation for Gesture Recognition
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Solution Overview
Problem
Current projection and 3D measurement systems, such as those using infrared light planes and optical time-of-flight methods, struggle to accurately recognize mid-air gestures and distinguish between true contact and hovering due to limitations in resolution and sensitivity to anomalies in the projection surface.
Innovation Solution
The system employs occlusion-based height estimation by analyzing the positional disparity between a transmitter and receiver to determine the height of foreground objects above a background surface, using returned illumination data to differentiate between occlusion regions and accurately calculate the distance, even with large accuracy errors in measured quantities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared light plane is projected just above and parallel to projection surface, then objects near the plane can be detected, but mid-air gestures above the plane cannot be recognized
Solution Approach 1:
The patent transitions from 2D plane detection to 3D depth measurement by introducing time-of-flight measurement. The system measures the time for light to travel to and from objects, enabling detection of objects at various heights above the projection surface, not just those breaking a specific plane.
Solution Approach 2:
The patent changes the measurement parameter from binary occlusion detection to continuous time-of-flight measurement. By measuring the flight time of light pulses, the system can determine distance to objects at any height, transforming the detection capability from surface-near only to multi-level spatial detection.
2Length of stationary object
If optical time-of-flight measurement is used for medium-long range depth imaging, then range sensing capability is improved, but resolution at close distances deteriorates due to electronic circuitry limitations
Solution Approach 1:
The patent combines two measurement approaches: time-of-flight measurement for medium-long range and occlusion-based height estimation for close distances. The occlusion method uses the transmitter-receiver disparity to calculate height from the area of occluded surface illumination, providing high resolution at close ranges where ToF struggles.
Solution Approach 2:
The patent introduces an intermediary measurement method (occlusion-based estimation) that bridges the gap between surface contact detection and medium-range ToF measurement. This intermediary approach uses geometric relationships and light occlusion patterns to provide accurate close-distance measurements without the electronic circuitry limitations of direct ToF.
3Measurement precision
If infrared light plane detection is used, then touch detection is achieved, but the system becomes sensitive to anomalies in the projection surface that break or distort the light plane
Solution Approach 1:
The patent extracts the height measurement information from the light plane breaking method and reformulates it as occlusion-based estimation using transmitter-receiver disparity. Instead of detecting broken light planes, the system measures the area of occluded surface illumination and calculates height from this occlusion pattern, making the measurement independent of projection surface anomalies.
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 enables precise distinction between touch and hover events to a few millimeters, improving the accuracy of gesture recognition and touch detection by combining 2D image processing with z-axis triangulation using surface occlusion information.
Implementation Method 1
Optical time-of-flight (ToF) measurement is a proven method of range sensing that works by measuring the flight time of an emitted light signal which reflects off a point in the field of view
Implementation Method 2
When the transmitter and receiver are not co-located, a positional disparity exists that causes some projected light to not be received by the receiver after reflection. This results in occlusion regions that can be used to determine height above the surface
Data Source
AI summary
A projection system emits light pulses in a field of view and measures properties of reflections. Properties may include time of flight and return amplitude. Foreground objects and background surfaces are distinguished, distances between foreground objects and background surfaces are determined based on reflections that are occluded by the foreground objects and other properties of the projection system.