These lenses do not suffer from distortion problems, as they collimate the light that enters the lens. This results in equal magnification, independent of object distance and thus no perspective is encountered within the depth of field around the fixed operating distance. As a consequence of collimating the light, the aperture of the lens needs to be the same size as the FOV, thus lenses with a large FOV are physi-cally large and can be very expensive.
For the most demanding measurement applications it is also possible to get a double sided telecentric lens. This helps to maintain accurate measurements, even when the image starts to move out of focus, while increasing the depth of field further, and providing even lower distortion.