Optics: Lens mounts
To attach a lens to a camera, there needs to be some type of mounting system. Both mechanical stability (a loose lens will deliver an out of focus image) and the distance to the sensor has to be defined. In order to guarantee compatibility between different lenses and cameras the following standard lens mounts are defined:
T-Mount
T-Mount is often also refered to as M42 mount.
Lenses with M42 mount (sometimes referred to as T-mount), or M58x0.75 and M72x1 mount are used as an alternative to F-mount for line scan cameras or high resolution sensors as it is considered more robust.
S-Mount
Extremly small lens mount system. Smaller lens mount systems such as S-mount are normally used for board level cameras and micro head cameras. These lenses only allow a minimum of adjustment.
C-Mount
The most common type of lens mount used in machine vision applications. It benefits from a very wide range of lenses and accessories.
The C-mount connection is described in the specification 1-32UN-2A. It is an imperial thread with a diameter of one inch and a pitch of 32 threads per inch. This means that it virtually corresponds to a metric thread M25.5 x 0.75 mm.
The back focal distance of a C-mount connector is 17.526 mm. This makes it exactly 5 mm longer than the back focal distance of the CS-mount connector. This means that a C-mount connector can be used on a camera with a CS-mount connector if a CS-mount adapter (5 mm spacer ring) is inserted between the lens and the camera.
Because of its relatively small diameter of 1 inch (25.4 mm), a C-mount connector is not suitable for larger sensors such as those used in high- resolution cameras or line scan cameras.
CS-Mount
The CS-mount is essentially the same as C-mount but with a 5mm shorter flange focal length. Commonly used in CCTV cost-sensitive applications. It is less common in machine vision.
The CS-mount connection is described in the specification 1-32UN-2A. It is an imperial thread with a diameter of one inch and a pitch of 32 threads per inch. This means that it virtually corresponds to a metric thread M25.5 x 0.75 mm.
The back focal distance of a CS-mount connector is 12.526 mm. This makes it 5 mm shorter than the back focal distance of the C-mount connector. For this reason, it is not possible to use a CS-mount lens on a C-mount camera, even with an adapter.
Because of its relatively small diameter of 1 inch (25.4 mm), a CS-mount connector is not suitable for larger sensors such as those used in high- resolution cameras or line scan cameras.
F-Mount
A lens connector used in imaging and machine vision particularly for high- resolution cameras or line scan cameras.
F-mount is the name for Nikon's SLR camera lens mount system. Due to its large format it is commonly used for line scan applications and large matrix sensors. Lenses can be easily exchanged thanks to the bayonet connection.
