Projector Camera Calibration Semi-Transparent Screen
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Solution Overview
Problem
Conventional calibration methods are unsuitable for projector-camera systems with semi-transparent screens, as the calibration pattern blends with the background, making edge detection and corner detection ineffective.
Innovation Solution
The method involves temporally varying a calibration pattern during image capture to apply temporal correlation, allowing the pattern to be separated from the background, and using robust feature detection for automatic calibration of the projector-camera system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods (edge detection, corner detection) are used with semi-transparent screens, then the calibration process is simple, but the calibration pattern blends with the background making detection ineffective
Solution Approach 1:
The calibration pattern is temporally varied by alternating between displaying the calibration pattern and displaying a uniform field (or no pattern). This periodic action creates temporal contrast that allows the system to distinguish the calibration pattern from the background, enabling effective feature detection despite the semi-transparent screen blending effects.
Solution Approach 2:
The system performs preliminary temporal separation of the calibration pattern from the background by capturing multiple images at different temporal states (pattern displayed vs. uniform field displayed). This preliminary action creates distinct temporal correlation signals that make subsequent feature extraction effective.
2Loss of information
If the calibration pattern is displayed continuously on a semi-transparent screen, then the pattern is always visible, but it blends with the background reducing detectability
Solution Approach 1:
The calibration pattern is displayed periodically rather than continuously, alternating with uniform field displays. This periodic action creates temporal contrast that enables the imaging device to distinguish pattern features from background elements, preventing information loss while maintaining detectability.
Solution Approach 2:
The system dynamically switches between different display states (calibration pattern vs. uniform field) during the image capture sequence. This dynamic approach allows temporal correlation techniques to separate the stationary calibration pattern from the background, maintaining both visibility and detectability.
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 alignment of 2-dimensional coordinates, ensuring precise interaction between real-life users and projected images, even in systems with semi-transparent screens, by enhancing the visibility of the calibration pattern and extracting features effectively.
Implementation Method 1
an imaging device positioned behind the semi-transparent screen and operatively connected to the projector and the processor
Data Source
AI summary
An automatic calibration method for a projector-camera system including a semi-transparent screen is disclosed herein. An image sequence is caused to be captured from the semi-transparent screen and through the semi-transparent screen while a calibration pattern having features is displayed and not displayed in an alternating succession on the semi-transparent screen. A temporal correlation image is created from the image sequence and a discrete binary signal. Peaks are identified in a spatial cross correlation image generated from the temporal correlation image, where a pattern of the identified peaks corresponds to a pattern of the features in the calibration pattern. The peaks are transformed to coordinates of corrected feature points. A comparison of the corrected feature points and a ground truth set of coordinates for the features is used to determine whether the projector-camera system is calibrated.