Monocular Camera Position Detection Using Shadow Segmentation
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Solution Overview
Problem
Existing interactive projector systems face challenges in accurately detecting the position of a pointing element due to the influence of shadows, which affects the detection accuracy of the pointing element with respect to the operation surface.
Innovation Solution
A method involving a monocular camera that captures two images of the pointing element with different illumination settings, one without shadows and one with shadows, allowing for the extraction of the pointing element area and shadow area, and determining the position of the pointing element based on their relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a monocular camera is used to detect the position of the pointing element, then the device complexity is reduced, but the detection accuracy deteriorates due to shadow interference
Solution Approach 1:
The patent divides the imaging process into two separate illumination conditions: one where the illumination section illuminates both the pointing element and operation surface, and another where it illuminates only the pointing element. This segmentation allows the system to separate the shadow information from the pointing element information, enabling accurate position detection using a simple monocular camera without requiring complex multi-camera setups.
Solution Approach 2:
The patent introduces shadow as an intermediary element to detect contact. By analyzing the shadow of the pointing element on the operation surface, the system can indirectly determine whether the pointing element is in contact with the surface. The shadow serves as a mediator that provides contact information without requiring direct measurement of the pointing element's position, thus maintaining high detection accuracy with simple hardware.
2Measurement precision
If triangulation using multiple cameras is used to detect the position of the pointing element, then the detection accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent extracts shadow information from the imaging process to serve as a separate detection channel. Instead of relying on multiple cameras to provide multiple viewing angles for triangulation, the system extracts shadow characteristics (presence, position, shape) from a single camera's image under controlled illumination conditions. This extraction approach provides contact detection information without requiring the complexity of multiple cameras and triangulation calculations.
Solution Approach 2:
The patent uses the shadow as a copy or representation of the pointing element's contact state. The shadow on the operation surface serves as a two-dimensional copy that contains sufficient information to determine contact, eliminating the need for three-dimensional measurement through triangulation. This copying approach simplifies the hardware while maintaining detection accuracy.
3Illumination intensity
If the illumination section illuminates both the pointing element and operation surface, then the visibility of the operation surface is improved, but the shadow of the pointing element interferes with detection accuracy
Solution Approach 1:
The patent employs periodic switching of illumination modes: first illuminating both the pointing element and operation surface to capture the operation surface image, then illuminating only the pointing element to capture the shadow image. This periodic action allows the system to collect both visibility information and shadow information at different time points, eliminating the interference between illumination and shadow detection while maintaining both functions.
Solution Approach 2:
The patent performs preliminary separation of illumination functions by configuring the illumination section to selectively illuminate different targets. Before detecting the pointing element position, the system preliminarily captures the operation surface image under full illumination, then switches to shadow-only illumination to capture contact information. This preliminary action prevents shadow interference during operation surface visualization while ensuring accurate contact detection.
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 accurate detection of the pointing element's position without the need for three-dimensional measurement, improving detection accuracy by distinguishing between the pointing element and its shadow.
Implementation Method 1
an illumination section (400) configured to perform illumination with at least one of a plurality of illumination devices (410, 420)
Data Source
AI summary
A position detection method of detecting a position of a pointing element with respect to an operation surface includes: obtaining a first taken image by imaging the pointing element with the operation surface as a background using a monocular camera while performing illumination with a first illumination section without performing the illumination with a second illumination section at a position different from a position of the first illumination section; obtaining a second taken image by imaging the pointing element with the operation surface as the background using the camera while performing the illumination with the second illumination section without performing the illumination with the first illumination section; extracting pointing element and shadow areas from the first taken image and the second taken image; detecting a position of the pointing element with respect to the operation surface using a relationship between the pointing element area and the shadow area.