Whether in the camera of a smartphone, a microscope or an industrial vision system – auto-focus ensures that the image is automatically focused. But how exactly does this work? And which technologies are used in industrial image processing?
An auto-focus system automatically adjusts the focus of an optics to the desired image area. The aim is to always produce a sharp, high-contrast image with different object distances or movements.
This is particularly important in industrial image processing, where different object sizes, changing working heights or dynamic production conditions often occur.
Instead of manually readjusting the optics, auto-focus systems perform this task fully automatically – quickly, precisely and reproducibly.
Most auto-focus systems, both in classic photography and in industrial cameras, are based on contrast measurement in the image. The system searches for the lens position at which the image contrast is at its maximum – i.e. where the edges in the image appear sharpest.
This process takes place in real time:
The system automatically finds the optimum focal plane – without external sensors or manual intervention.
Two auto-focus methods have become established in industrial practice:
Both approaches are image-based, but differ in terms of structure, response time, service life and precision.
With mechanical focusing, the position of the lens is physically changed in order to adjust the focus. This is done using motors or actuators that move the lenses along the optical axis.
This method offers high precision and stability – ideal for applications where repetition accuracy and exact focus positions are crucial.
Liquid lens technology is a modern and wear-free principle. Here, no lens is moved mechanically – instead, a liquid inside the lens changes its surface curvature and thus the focal length.
This is achieved by applying an electrical voltage that changes the contact angle of the liquid to an elastic membrane. This physical phenomenon is known as electrowetting.
Advantages of liquid lens technology:
Please note:
Liquid lenses require electronic control and temperature compensation to keep the focus position stable. In addition, a warm-up time of approx. 5 minutes may be required before full performance is achieved.
Auto-focus is a central element of modern image processing systems.
While mechanical lens focusing systems impress with their precision and stability, liquid lenses offer a fast, wear-free and compact solution for dynamic applications.
In combination with powerful Image Processing Software, both technologies enable flexible, automated and high-precision focusing – a decisive advantage for modern industrial vision systems such as the Smart Cameras and Vision Sensors from wenglor.
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