Hybrid Autofocus System Using Laser Distance Correction
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Solution Overview
Problem
Autofocusing methods in cameras, particularly PTZ cameras, face challenges in maintaining focused images during panning, tilting, and zooming, leading to blurry images and inefficient focus acquisition due to lens deviations and environmental changes, which existing methods struggle to address effectively.
Innovation Solution
A method that involves measuring object distances using a distance measurement system, determining correction factors based on depth of field ratios, and continuously updating these factors to adjust focus positions, allowing for quicker and more accurate autofocusing even when lens behavior deviates from theoretical trace curves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive autofocus methods are used, then the system cost is reduced, but the autofocus performance deteriorates in low light conditions and scenes with low contrast
Solution Approach 1:
The patent combines passive autofocus (contrast detection) with active autofocus (laser distance measurement) into a hybrid system. The laser provides initial distance estimation to guide the contrast detection algorithm, enabling reliable autofocus in low light conditions while maintaining cost-effectiveness by using the simpler passive method when sufficient light is available.
Solution Approach 2:
The system dynamically changes operational parameters by switching between passive-only mode (good light conditions) and hybrid mode (low light conditions). The laser distance measurement is activated only when needed, changing the system's operational state based on environmental conditions to optimize both cost and performance.
2Measurement precision
If passive autofocus algorithms continuously search for maximum contrast, then focus accuracy is improved, but image wobbling increases during the search process
Solution Approach 1:
The laser distance measurement system performs preliminary action by providing an initial distance estimate before the contrast detection search begins. This allows the algorithm to start from a position closer to the optimal focus point, reducing the extent of the search needed and minimizing image wobbling while still achieving accurate focus.
Solution Approach 2:
The system uses feedback from the laser distance measurement to guide and constrain the contrast detection search. By incorporating the active measurement feedback into the passive search algorithm, the system reduces unnecessary focus motor movements and achieves faster convergence with less image instability.
3Productivity
If trace curves are used for autofocus during zooming, then focus speed is improved, but accuracy deteriorates due to lens deviations from theoretical characteristics
Solution Approach 1:
The system uses feedback from laser distance measurements taken during zooming operations to correct deviations from theoretical trace curves. By comparing actual measured distances with predicted distances from trace curves, the system dynamically adjusts focus positions to maintain accuracy while benefiting from the speed of trace curve-based autofocus.
Solution Approach 2:
The patent replaces reliance on purely mechanical/optical trace curve data with a hybrid approach that substitutes some theoretical calculations with actual laser distance measurements. This substitution corrects for lens variations and manufacturing tolerances, maintaining focus accuracy without sacrificing the speed advantage of trace curve methods.
4Adaptability or versatility
If autofocus is performed during panning and tilting operations, then focus on new objects is achieved, but image quality deteriorates due to motion blur and delayed focus response
Solution Approach 1:
The system performs preliminary distance measurement using the laser before and during panning/tilting operations. This allows the autofocus algorithm to be pre-positioned closer to the correct focus point when the camera movement completes, reducing the time needed for focus adjustment and minimizing motion blur while maintaining image quality.
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 ensures better focused images during camera movements and zooming operations, reducing wobbling and improving image quality by adapting to lens variations and environmental changes, thus providing more reliable visual information to operators.
Implementation Method 1
measuring a first object distance from the camera to an object on which to focus
Data Source
AI summary
Autofocusing a camera while zooming may include zooming the lens to a first zoom position, measuring a first object distance from the camera to an object on which to focus, determining a first focus start position using the first object distance, performing a first autofocus using the first focus start position as a starting point, thereby determining a first focus position. A first lookup object distance may be determined based on the first determined focus position. A first correction factor may be calculated as a ratio between the first lookup object distance and the first object distance. The lens may be zoomed to a second zoom position, and a second focus position may be determined using a second object distance based on the first object distance and a second correction factor based on depths of field at the second and first zoom positions.