The construction of a lens system (lens radii, distances between lenses), the distance between object and lens (working distance), as well as the distance between the lens and the sensor have an impact on the image. The ratio between object reproduction (image) and object is called magnification.
The following diagram explains the function of a lens.
The focal length of a lens defines its magnification. Lenses with fixed elements have a fixed working distance and fixed magnification, these are called fixed focal lenses. Lenses with a movable focusing unit allow the working distance to be changed. Zoom lenses also have a variable focal length (which means a variable magnification). Most machine vision lenses have a fixed focal length. The use of zoom lenses is much less prevalent in machine vision applications. These lenses change their focal length by moving lens elements which can make them mechanically unstable and less suitable for making accurate, repeatable measurements.
Most lenses used in machine vision applications are manufactured with metal housings and focus mechanisms which guarantee the stability of the lens providing robust and repeatable measurements. In addition some lenses are available with high shock and vibration characteristics which are suitable for even the harshest environments. It is possible to improve stability through the use of glued lenses and locking screws.
In order to be able to offer the optimum lens for the widest range of vision applications, we cooperate with a vast range of manufacturers and are thus able to offer a comprehensive product portfolio, ranging from standard lenses to customer specific solutions. Please note that due to the wide range available not all options can be shown in this handbook, so please contact our experts if you have specific requirements not shown here.