Lenses that are telecentric on both sides feature a parallel beam path on both the lens and the image side and they are used as part of measuring technology.
In comparison to entocentric standard lenses the opening angle is always zero in a certain area, based on the telecentric features on the lens side. Ideally, the beam path runs absolutely in parallel and the image does not feature distorted perspectives.

What’s more, this type of lens always uses almost the same representation scale in Z direction, i.e. along the visual axis, within the so-called telecentric range. As a result, the image is always roughly the same size.
The telecentric features on the image side cause the rays to come into contact with the image layer vertically, where digital cameras accommodate the image recording chip. This largely prevents pixel vignetting and enables to use the image layer for subsequent focussing.

• Measuring bore diameters
• Measuring gauge marks at different heights, such as on PCBs
• Measuring outlines regardless of the height
• Measuring certain characteristics at different work piece levels
• Checking notches
• Detecting errors on assembled PCBs