Relay lenses are used in image intensifiers to collect an image and transfer it from one place to another. An image intensifier typically has an image plane that is on the back of a piece of glass or on a fibre plate. In both cases it is not possible for a sensor to be positioned so that it can pick up that image plane. To solve this problem – you need a specialist lens that can pick up the intensifier image and relay (transfer) that image to the image plane of the sensor. Working closely with instrument manufacturers – Resolve Optics designs and builds optimized custom relay lenses for imaging applications including microscopy, inspection and electronic imaging.
Further Information: https://www.resolveoptics.com/2018/12/bespoke-mounted-relay-lenses/