ENGINEERING ASPECTS OF NIGHT VISION SYSTEMS
The night sights were designed to achieve the maximum performance with minimum
size and cost. The other essential requirement was for the military night-sight to be
robust, protected from the environment and easy to maintain.
The problems that were overcome were the result of having to mount the night
sight in a vehicle. In most cases the objective assembly was mounted remotely from a
convenient viewing position to ensure armoured protection. Optical relay techniques were
used including biocular viewing of the image by means of a beam splitting prism. It was
found too difficult to seal the usual commercial ring arrangement used for iris and focus
control under all climatic conditions whilst maintaining the operating torque within
reasonable limits. A solution to the problem was to use knob operation with seals on the
small diameter shafts leading from the knobs to the operating mechanism. To maintain the optical transfer function within
acceptable limits, the centering error of each optical element was restricted to the order
of 0.05mm. Because as many as four components could contribute to the error,
bore-on-assembly techniques were used.
SRDE worked with the development contractor making him aware of the military
requirements for the equipment. The development and production of night viewing equipment
with large diameter and fast optics posed new problems for the UK optical industry.