Autofocus Searching Method with Adaptive Step Size
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Solution Overview
Problem
Current autofocus methods in optical inspection technologies are inefficient and prone to human error, with manual focusing being slow and inconsistent, and existing automatic focusing techniques are limited by fixed step sizes and reference focal depth, making it difficult to achieve high-speed and accurate autofocusing, especially for objects far from the focal depth.
Innovation Solution
An autofocus searching method that calculates focus values based on image intensity, contrast, and definition, using a self-adaptive step size and direction, allowing for longer travel focusing without sectional searches, by adjusting the focus-searching step size inversely proportional to the focus value, and changing direction when approaching the peak focus value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If stepwise focus searching with fixed step size is used, then the searching process is simple, but the focusing speed is slow and efficiency is reduced
Solution Approach 1:
The patent implements dynamic step size adjustment in focus searching, where the step size changes automatically based on the current focus state and distance from the optimal focus point. This allows large steps when far from focus and small steps when near focus, resolving the contradiction between simple process and fast speed.
Solution Approach 2:
The patent changes the searching parameter (step size) dynamically during the focus searching process. By adjusting the step size parameter based on focus evaluation results, the system achieves both simplicity and high speed without requiring complex multi-stage processes.
2Productivity
If variable step focus searching is used, then the searching speed is improved, but the reference information is limited and searching performance is constrained
Solution Approach 1:
The patent employs feedback mechanisms where the focus evaluation result at each step informs the next step's direction and size. This continuous feedback loop provides rich reference information that guides the searching process, overcoming the limitation of conventional variable step methods while maintaining high speed.
Solution Approach 2:
The patent performs preliminary focus evaluation and step size calculation before each searching step, preparing optimal parameters in advance. This preliminary action ensures that each step uses the best available reference information, improving both speed and accuracy without additional hardware.
3Reliability
If focal depth is used as reference for focus-searching step, then the searching can be performed within limited scope, but the searching speed cannot be increased through large step manner and autofocusing is limited to short travel range
Solution Approach 1:
The patent dynamically adapts the step size to the current distance from the optimal focus point and the evaluated focus quality. This allows the system to take large steps when traveling long distances and small steps when approaching the final focus, achieving both long travel range and high accuracy without being constrained by fixed focal depth references.
Data Source
AI summary
An autofocus searching method includes the following procedures. First, focus values of images, which are acquired during the movement of the object lens, are calculated, in which the focus value includes at least the intensity value of the image derived from the intensities of the pixels of the image. Next, focus searching is based on a first focus-searching step constant and a first focus-searching direction, in which the first focus-searching step constant is a function, e.g., the multiplication, of the focus value and a focus-searching step size. If the focus searching position moves across a peak of the focus values, it is then amended to be based on a second focus-searching direction and a second focus-searching step constant, in which the second focus-searching step constant is smaller than the first focus-searching step constant, and the second focus-searching direction is opposite to the first focus-searching direction.