Bosch KCU-40 The inside view of the tube side with the scanning yokes.

The White tube is the top one, then Red and Blue at the bottom.
The prismatic light splitter is at the front with the diascope lamp projector unit immediately behind it, This projects a pattern onto the tubes for registration and line up. There is a relay lens to carry the light to the blue tube.

This picture is courtesy of M. Van der Smeede and is of his restored camera.