Occlusion-Based Height Estimation for Projection Touch
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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 estimate height, even with high accuracy errors in measured quantities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If optical time-of-flight measurement is used for range sensing, then medium-long range depth imaging is achieved, but resolution at close distances deteriorates due to limitations in electronic circuitry to accurately measure short time scales
Solution Approach 1:
The patent transitions from measuring only time-of-flight (1D temporal measurement) to measuring both time-of-flight and pulse amplitude (adding spatial/dimensional information). This dual measurement approach enables the system to distinguish between close objects and distant objects based on amplitude attenuation, thereby improving resolution at close distances while maintaining medium-long range capability.
Solution Approach 2:
The patent changes the measurement parameters from solely time-based (ToF) to include amplitude-based measurements as well. By monitoring pulse amplitude variations, the system can compensate for the limitations of time measurement at short distances, effectively resolving the contradiction between range and close-distance resolution.
2Ease of operation
If infrared light plane is projected just above and parallel to projection surface, then touch detection is enabled, but mid-air gestures are not recognized because they are above the IR light plane
Solution Approach 1:
The patent extends the detection capability from the 2D projection surface to the 3D space above it by utilizing amplitude attenuation information. This allows the system to detect objects at various heights (z-axis dimension) while maintaining accurate touch detection on the surface, thereby enabling mid-air gesture recognition without sacrificing touch sensitivity.
Solution Approach 2:
The patent introduces pulse amplitude as an intermediary parameter that mediates between the infrared light plane and objects in 3D space. By using amplitude attenuation as a cue, the system can infer the presence and position of objects above the projection surface, enabling gesture recognition while maintaining touch detection accuracy.
3Ease of operation
If infrared light plane is used for touch detection, then touch interaction is enabled, but sensitivity to anomalies in projection surface deteriorates causing false detections
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors both time-of-flight and pulse amplitude information. By comparing amplitude variations with expected patterns, the system can distinguish between legitimate touch interactions and anomalies in the projection surface, reducing false detections while maintaining touch interaction capability.
Solution Approach 2:
The patent changes the detection parameter from binary presence/absence (based solely on IR light plane interruption) to amplitude-based detection. This parameter change enables the system to filter out false signals caused by projection surface anomalies, improving reliability while preserving touch interaction sensitivity.
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 recognition of touch and gesture interactions in 3D space, distinguishing between contact and hovering with high accuracy, even with large errors in measured data, 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
measuring the flight time of an emitted light signal which reflects off a point in the field of view
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.