What do „fixed focus“ and „adjustable“ mean?

Fixed focus: the optics are set at the factory to a fixed distance and cannot be changed – typically a point in the range 1–5 m. Benefit: no accidental adjustment possible, stable over the entire service life. Trade-off: cannot be adapted to other distances. Adjustable: the optics sit in an adjustable brass ring at the front of the module and can be focused by the user to any desired distance (5 cm to infinity). After adjustment the optics are secured with thread-locking varnish in the thread. Which variant? Fixed focus for defined series production with constant distance, adjustable for flexible applications and one-off setups.