Autofocus Control Synchronizing Illumination With Imaging Frame Rate
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Solution Overview
Problem
Vision measuring devices face challenges in achieving accurate and high-speed auto-focusing due to issues like flicker-induced uneven brightness, external diffused light, and prolonged focusing times, which affect the reliability of contrast-based focusing methods.
Innovation Solution
The solution involves adjusting the light volume of the illumination device based on calculated frame rates and synchronizing it with the imaging device's vertical synchronization signal, while also adjusting the gain of the imaging device and using software to detect and compensate for flicker frequencies, ensuring consistent illumination and high-speed focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the frame rate of the imaging device is increased to improve auto-focusing speed, then the auto-focusing speed is improved, but flicker-induced brightness unevenness becomes more severe
Solution Approach 1:
The illumination device emits light in periodic pulses synchronized with the imaging device's frame rate. By coordinating the illumination cycle with the imaging cycle, the system ensures that each captured image receives consistent illumination intensity, eliminating flicker-induced brightness variations while maintaining high frame rates for rapid auto-focusing
Solution Approach 2:
The control device monitors the frame rate of the imaging device and dynamically adjusts the illumination emission frequency accordingly. This feedback mechanism ensures that the illumination timing is continuously synchronized with the imaging timing, preventing flicker effects even when frame rate changes during auto-focusing operations
2Stability of the object's composition
If the illumination emission frequency is increased to improve brightness consistency, then brightness uniformity is improved, but the complexity of coordinating with imaging frame rate increases
Solution Approach 1:
The control device receives frame rate information from the imaging device and automatically adjusts the illumination emission frequency to match. This feedback-based synchronization eliminates the need for complex manual coordination, reducing control complexity while maintaining brightness consistency
Solution Approach 2:
The system dynamically changes the illumination emission frequency parameter to match the imaging frame rate parameter. By synchronizing these two parameters, the system achieves brightness consistency without requiring complex fixed-frequency coordination mechanisms
3Loss of time
If the imaging device moves at high speed to reduce auto-focusing time, then the auto-focusing time is reduced, but the image acquiring pitch becomes rough and in-focus position detection becomes inaccurate
Solution Approach 1:
The synchronized illumination and imaging cycles create periodic, consistently bright images at each focal plane position. This periodic illumination pattern enables the detection device to reliably identify in-focus positions even when the imaging device moves rapidly, maintaining measurement precision while reducing overall focusing time
Data Source
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AI summary
A vision measuring device, comprising an imaging device which images a workpiece, and of which frame rate is variable; an illumination device which irradiates the workpiece with light; a position control system which controls an in-focus position of the imaging device and outputs the in-focus position as information representing a position in an in-focus axis direction; and a control device which, when the position control system controls the in-focus position, controls the frame rate of the imaging device and adjusts a light volume of the illumination device in accordance with the frame rate of the imaging device.