Industrial camera systems include a high-quality lens to focus the necessary information on the sensor. The choice of the right lens depends on the one hand on the measuring task and the image field size, and on the other hand on the desired resolution. Industrial lenses are available in different versions. A frequently used lens, for example, is the entocentric lens, which has a fixed focal length. It depicts objects of the same size at different distances and in different sizes: smaller in the distance and larger in the vicinity. Normal lenses are therefore not suitable for applications in the measuring range, but the fixed focal length allows the object area to be captured to be adjusted very well. The areas of application for entocentric lenses are, for example, assembly checks or the reading of barcodes. There are also lenses with which the focal lengths can be adjusted within a fixed range by means of a manual or motorized zoom function, as can the aperture or autofocus function. These zoom lenses are used for strongly changing distances.
Another frequently used lens is the telecentric lens. This has the particular advantage that objects viewed at different distances have the same image size. Since the main beams in the object and image space are guided parallel to the optical axis, the objects of different distances imaged on the image plane are of the same size. This advantage can be used for objects to be measured on conveyor belts, e.g. if they are not exactly positioned. Telecentric lenses are particularly suitable for more demanding optical inspection procedures.