Alternating Pattern Calibration for Projector-Camera Mapping
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Solution Overview
Problem
The process of projection mapping is complex due to the time-consuming calibration of projectors onto three-dimensional surfaces, which requires precise alignment and synchronization of structured light patterns, often hindered by camera rolling shutters and projector color wheels, leading to prolonged calibration times.
Innovation Solution
A method that uses alternating patterns projected by the projector, synchronized with camera frame acquisition, to generate functions relating camera frame indices with pattern indices, allowing for the rapid determination of structured light pattern indices and subsequent mapping of projector pixels to camera pixels and object positions, thereby reducing calibration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional structured light patterns are projected and captured for calibration, then mapping accuracy is achieved, but calibration time becomes excessively long
Solution Approach 1:
The patent applies periodic action by projecting alternating binary patterns (black/white sequences) in rapid succession instead of using traditional complex structured light patterns. This periodic projection of simple alternating patterns enables the camera to capture synchronized frames that can be processed to generate the mapping, significantly reducing calibration time while maintaining accuracy through the functional relationship analysis between camera frames and projector patterns
Solution Approach 2:
The patent implements preliminary action by establishing a functional relationship between camera frame indices and projector pattern indices through the alternating patterns calibration first. This preliminary functional mapping allows the system to quickly determine correspondence without requiring time-consuming traditional structured light projection and capture sequences, thus reducing overall calibration time while preserving mapping precision
2Measurement precision
If synchronized projection and capture is implemented for accurate mapping, then mapping precision is improved, but process complexity increases due to coordination requirements
Solution Approach 1:
The patent applies self-service by designing a system where the alternating binary patterns inherently encode temporal and spatial information that automatically enables synchronization. The camera captures frames during the projection sequence, and the functional relationship between frame indices and pattern indices is derived automatically from the captured data without requiring complex external synchronization hardware or protocols, thus reducing device complexity while maintaining mapping precision
3Productivity
If rolling shutter camera is used for capture, then frame acquisition is continuous, but frame-blending occurs causing measurement errors
Solution Approach 1:
The patent introduces an intermediary approach by using the functional relationship between camera frame indices and projector pattern indices as a mediator to resolve the frame-blending issue. Instead of trying to prevent blending or use complex deblending algorithms, the system establishes a mathematical relationship that maps camera pixels to projector pixels through the alternating patterns calibration, allowing accurate pattern identification even when frames contain blended content from multiple projection states
Data Source
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AI summary
A device, system and method for generating a mapping of projector pixels to camera pixels and/or object positions using alternating patterns is provided. A device controls a projector to project, while a camera acquires frames thereof, in a sequence: alternating patterns; and structured light patterns, the alternating patterns comprising first and second predetermined patterns projected before and/or after the structured light patterns. The device determines, using the frames as coordinated with the alternating patterns, one or more functions relating respective indices of the alternating patterns and the frames, on one or more of a camera pixel-by-pixel basis and a camera scan-line-by-scan-line basis. The device generates, and stores at a memory, a mapping of projector pixels to one or more of camera pixels and positions on an object in the overlapping fields-of-view, based on relating the frames with the structured light patterns using the one or more functions.