When it comes to inspection and evaluation of spatially extended objects, standard (endocentric) lenses and also conventional telecentric lenses quickly reach their limits. Problems of this kind can be solved by using telecentric large-field lenses with Fresnel technology.
The advantage of telecentric lenses, i.e. perspective-free imaging, has so far been contrasted by the disadvantage that they are severely constrained in their use by limited field of view sizes and also expensive. Due to the principle of using the parallel main beam path for imaging, the front lens must be larger than the object to be inspected.
As a result of this, the larger the component size, the greater the manufacturing work required to produce the optical components of telecentric lenses made of glass, which is reflected in their price. Moreover, lenses of this type are heavy, long and sensitive to mechanical damage.
This is exactly where the considerations for telecentric large field lenses come in. By replacing the glass front lens with a very finely structured plastic stepped lens (10 zones / mm), considerably larger fields of view can be achieved with telecentric lenses. The use of Fresnel lenses improves the diameter-to-mass ratio and the diameter-to-length ratio enormously. In this way, telecentric lenses with diameters of up to 600 mm are possible.
The applications for telecentric wide-field lenses are the inspection of large parts with wide spatial dimensions and holes, openings, notches, magazined parts as well as assembly and mounting inspection. Telecentric large field lenses prove their strength in these applications, as they are the unique solution for these inspection tasks.
