Lens having a fixed focal length and constant overall length for auto focus applications including five lens groups of ++--+, -++-+, -+++-, -++--, +-+--, +-++- or ++++- refractive powers

A lens system with a fixed focal length, comprising:

• five lens groups, wherein three lens groups are mounted in a stationary manner and two lens groups are mounted in a displaceable manner along an optical axis, wherein the lens system comprises the following lens groups in order from an object side of the lens system to an image side:
• a first lens group, as viewed from an object side, that is arranged in a stationary manner having a positive refractive power,
• a second lens group configured as a focusing front group that is arranged in a displaceable manner,
• a third lens group having a negative refractive power and containing a stationary iris diaphragm, an aperture of which is adjustable, the third lens group being arranged in a stationary manner,
• a fourth lens group configured as a focusing back group that is arranged in a displaceable manner, and
• a fifth lens group having a positive refractive power that is arranged in a stationary manner relative to an imaging plane in a lens barrel and both the focusing front group and the focusing back group are movable jointly relative to one another and to the lens groups arranged in a stationary manner in order to focus the fixed focus length lens system on objects at different object distances.