This leads to the finite resolution of a lens system described above. Some aberrations will be present in any lens system. The term can also mean the primary lens in a combination lens system. Hopkins patented his lens system in 1959. The GF3 is one of the world's smallest and lightest interchangeable lens system cameras. Careful design of the lens system for a particular application minimizes the aberration. Real images may also be inspected by a second lens or lens system. The centre of the diaphragm's aperture coincides with the optical axis of the lens system. The lens system was made by Chance Brothers. The electrons are then focused by a lens system onto the sample. The Pentax KP uses the Pentax K-mount interchangeable lens system. The actual lens system is rigidly integrated into the construction. These units have a clear lens system and light sensitive retina cells. An additional lens stack, the "intermediate/projector" lens system, is after the sample.