Auto-Focus Lens Control via Parabola Fitting
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Solution Overview
Problem
Existing auto-focus methods, such as global search, are inefficient as they take a long time to find the focus position in a camera, requiring extensive motor movements across the entire focus range.
Innovation Solution
An auto-focus method that uses a motor to drive a focusing lens to different positions within the focus range based on varying electric current values, analyzing images captured at these positions to determine resolution values and fitting parabolas through these points to quickly identify the focus position, thereby reducing the search time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If global search method is used to find focus position by moving motor across entire focus range, then focus position can be accurately found, but the searching time becomes too long and efficiency is low
Solution Approach 1:
The focus search range is divided into multiple segments by sampling different current values (first, second, and third current values) across the focus range. Each segment is evaluated independently to identify regions containing the focus position, transforming a single long search into multiple shorter targeted searches.
Solution Approach 2:
The system performs preliminary sampling at multiple current values before final focus acquisition. By capturing images at different current values and calculating resolution values in advance, the system identifies the focus region beforehand, allowing the motor to jump directly to the optimal region rather than searching sequentially through the entire range.
2Reliability
If the motor drives the focusing lens through the entire focus range to ensure accurate focus, then focus accuracy is achieved, but the device complexity and operation time increase
Solution Approach 1:
The system captures images at different current values, calculates resolution values for each image, and uses this feedback to determine which current value range contains the focus position. The resolution value serves as feedback signal that guides the motor to the optimal focus region, replacing complex sequential searching with a feedback-driven targeted approach.
Solution Approach 2:
The system changes the current value parameter systematically across different sampling points (first, second, third current values) to explore the focus range. By varying this electrical parameter and measuring its effect on image resolution, the system efficiently maps the focus characteristics without mechanical complexity.
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 method significantly reduces the time required to find the focus position by analyzing images and determining the optimal current values, leading to a more efficient auto-focus process.
Implementation Method 1
A focusing lens (11) is driven by a motor (12) to move within a focus range of the lens module (10)... The motor (12) drives the focusing lens (11) to different positions within the focus range according to different values of the electric current applied to the motor (12)
Data Source
AI summary
An auto-focus method controls a motor to drive an optical lens of a lens module to a focus point and includes steps of: describing a first parabola according to three coordinate points in a coordinate system; describing a second parabola according to a first highest point of the first parabola and two coordinate points selected from the three coordinate points in the coordinate system, wherein the resolution values of two selected coordinate points are greater than that of unselected coordinate point; comparing a difference between the electric current value of a second highest point of the second parabola and the electric current value of the first highest point with a preset value; wherein when the difference is less than the preset value, the second highest point is regarded as the focus point.