Adaptive Autofocus Lens Positioning via Lookup Tables
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Solution Overview
Problem
Contemporary passive autofocus mechanisms require testing a substantial number of focusing lens positions, leading to longer autofocusing times and a risk of sub-optimal focus due to local sharpness maxima not being the highest.
Innovation Solution
The system uses historic and current focusing information to adaptively determine the best position of the focusing lens, reducing the number of positions that need to be tested by utilizing lookup tables and local searches with varying step sizes, based on parameters like aperture, shutter speed, and zoom position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed searching sequence is used to test multiple focusing lens positions, then focus accuracy is improved, but the time required for autofocusing increases
Solution Approach 1:
The system performs preliminary actions by storing focusing information from previous shots in a lookup table. Before conducting a full search, the system queries this table with current camera parameters (aperture, shutter speed, zoom position) to obtain a predicted best focus position, thereby avoiding the need to test all pre-determined positions and significantly reducing autofocus time while maintaining accuracy.
Solution Approach 2:
The patent replaces the mechanical trial-and-error search process with an information-based system. Instead of physically moving the lens through multiple positions and testing each one, the system uses stored focusing information and computer analysis to calculate and directly position the lens at the predicted optimal focus point, substituting computational logic for mechanical searching.
2Loss of time
If local searching is used to reduce the number of lens positions tested, then autofocusing time is reduced, but the risk of sub-optimal focus increases due to local sharpness maxima
Solution Approach 1:
The system incorporates feedback by continuously storing focusing information (sharpness measurements at different lens positions) from previous shots in a lookup table. This historical data provides feedback that helps predict the global maximum sharpness position, allowing the system to avoid local maxima while still using an efficient limited search approach rather than exhaustive testing.
Solution Approach 2:
The patent changes the parameters used for focusing determination by incorporating multiple camera parameters (aperture, shutter speed, zoom position) into the lookup table queries. By varying these parameters and storing corresponding best focus positions, the system adapts to different shooting conditions and avoids getting trapped in local maxima that may be optimal for one set of parameters but not another.
Data Source
AI summary
A method and system for effecting adaptive autofocusing, such as for a camera, are disclosed. The method can comprise obtaining focusing information, such as historic focusing information, storing the focusing information, and subsequently using the focusing information to facilitate a determination of a best position of a focusing lens during a focusing process. The use of such focusing information can result in a better choice for the next focusing lens position to be tested, such that the focusing process can be performed more rapidly.