PTZ Camera Focus Control Using Trace Curves
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Solution Overview
Problem
PTZ camera systems face challenges in maintaining focus under low light conditions, bright elements, and moving objects, as existing auto-focus methods are inefficient and often fail to lock onto the correct focus position, especially when zooming, panning, or tilting, leading to frequent focus hunting cycles.
Innovation Solution
The system employs a method of identifying and selecting trace curves that specify relationships between focus lens positions and zoom lens positions, using pan angle, tilt angle, and installation height to determine the optimal focus lens position, reducing the need for excessive auto-focus cycles by building a lookup table and interpolating focus positions based on these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional auto-focus methods are used in PTZ camera systems, then the system can attempt to lock onto focus positions, but the system experiences frequent focus hunting cycles and fails to maintain focus during zooming, panning, or tilting operations
Solution Approach 1:
The system pre-calculates and stores optimal focus lens positions corresponding to different zoom lens positions in trace curves before actual camera operation. When zooming occurs, the system retrieves the pre-determined focus position from the trace curve corresponding to the current zoom position, eliminating the need for real-time focus hunting and maintaining continuous focus during PTZ operations.
Solution Approach 2:
The patent introduces trace curves as an intermediary data structure that maps the relationship between zoom lens positions and focus lens positions. This intermediary allows the system to determine the correct focus position indirectly through lookup in the pre-computed trace curves, rather than directly searching for focus through trial and error methods.
2Illumination intensity
If the aperture is widened to capture more light in low light conditions, then more light is gathered, but the depth of field becomes narrower and focus becomes more sensitive to focus lens position
Solution Approach 1:
The system replaces manual or trial-and-error focus adjustment mechanisms with an automated control system that uses pre-computed trace curves. The controller automatically adjusts the focus lens to the precise position specified by the trace curve corresponding to the current zoom position, eliminating the need for mechanical focus hunting and ensuring accurate focus even with narrow depth of field.
3Adaptability or versatility
If a varifocal lens is used instead of a parfocal zoom lens, then the camera can zoom with variable focal length, but focus changes as focal length changes requiring continuous focus adjustment
Solution Approach 1:
The patent segments the zoom range into discrete zoom positions, with pre-computed focus positions stored in trace curves for each segment. This segmentation allows the system to handle the complex focus adjustment required by varifocal lenses by breaking it down into manageable discrete steps, simplifying the control logic while maintaining continuous focus during zoom operations.
Data Source
AI summary
Systems and methods for focus control in a pan-tilt-zoom (PTZ) camera system are described herein. An example of a method described herein includes identifying a set of trace curves associated with the camera system, each of the trace curves specifying relationships between focus lens positions and zoom lens positions for a corresponding camera position, selecting a trace curve using the set of trace curves and one or more of pan angle, tilt angle or installation height of the camera system, and identifying a focus lens position for a current zooming factor of the camera system based on the selected trace curve.