Background Differential Extraction for Movable Camera Tracking
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Solution Overview
Problem
Existing camera systems with movable viewpoints face challenges in extracting background differentials effectively, making it difficult to track moving objects in real-time due to delays in line of sight control and limitations of conventional background differencing methods.
Innovation Solution
A background differential extraction device that converts pixel positional information from movable camera images to polar coordinate information, allowing for comparison and differential extraction between actual and target backgrounds, even when the camera's line of sight and viewpoint are changing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed viewpoint camera is used for background differencing, then high-speed physical object identification is possible, but the technique cannot be directly applied to cameras with movable viewpoints
Solution Approach 1:
The patent transforms the coordinate system from Cartesian (fixed viewpoint) to polar coordinates (movable viewpoint). By converting pixel positions to polar coordinates (radius and angle) and using the camera's pan and tilt angles, the system adapts background differencing to work with movable cameras. This dimensional transformation allows the background model to account for viewpoint changes while maintaining extraction accuracy.
2Productivity
If the camera line of sight is moved to track high-speed objects, then tracking capability is improved, but response speed delay occurs due to mechanical movement limitations
Solution Approach 1:
The patent uses a Saccade Mirror system that creates an optical copy of the camera's field of view. By using galvanometer mirrors to reflect and redirect light paths, the system achieves instantaneous line of sight changes without physically moving the entire camera. This optical copying mechanism eliminates mechanical inertia delays while maintaining tracking capability.
3Ease of operation
If conventional background differencing is applied to movable cameras, then viewpoint flexibility is gained, but extraction accuracy deteriorates due to viewpoint changes
Solution Approach 1:
The patent implements a dynamic background model that updates in real-time based on camera movement. The system continuously adjusts the background representation by incorporating current pan and tilt angles, allowing the background model to adapt dynamically to viewpoint changes. This dynamic adjustment maintains extraction precision even as the camera moves freely to track objects.
Data Source
AI summary
This invention provides a technology that allows the acquisition of background differentials using images acquired by a camera, the viewpoint of which moves. First, said camera acquires a background image, i.e. an image that does not contain a target object. Using information on the line-of-sight direction and viewpoint position of the camera, position information for pixels in the background image is transformed to polar-coordinate information Next, the camera acquires an object image. Using information on the line-of-sight direction and viewpoint position of the camera, position information for pixels in the object image is transformed to polar-coordinate information. The polar-coordinate information for the pixels in the object image is used to identify a target background, said target background being the part of the background image in an angle region corresponding to the object image. By comparing the object image and the target background, the differential therebetween is extracted.