How lenses are made...in Leicester!

Author: Dennis Lennie

Published 1st April 2009


How lenses are made...in Leicester!
A tour of the factory is a wonderful insight into the production of these instruments.
We start with the raw material. With over 100 types of glass to choose from Cooke select a pre moulding depending on the lens model.
Grinding
We move into the main building now and are greeted by the industrial sound of machines at work. The first stop for our glass is the CNC (Computer Numerically Controlled) machines. These are high precision machines which grind the glass establishing the optical requirements for the lens.
Polishing
From here it’s a short journey next door to the polishing area. The glass elements are held on the base of the polisher and are slowly polished by a rotating robotic arm. One element at a time is held although due to the design of the polishing mount several elements can be held at once if needed.
There is a rack full of polishing moulds for the many different shapes of Cooke lenses, the skilled craftsmen select the shape depending on the curvature required.
Aspherical lens, with their different geometry, take a different route through this area.
At all times throughout the factory you are faced with state of the art technology working in perfect synergy with Victorian aged machines from the early 20th century.
Coating
Coatings are applied before the final grinding takes place, at all times throughout the process the elements are constantly measured, monitored and cleaned.
Edging
The edges of the elements are sprayed with black epoxy paint, if they were left clear then light would create reflections and ghosting between the elements.
Assembly
With the element completed it’s now time to assemble the lens. The metal work and on average the 12 elements required for an S4 lens are assembled in the “fitting” room. It’s a quiet calm atmosphere in here, no industrial noise with a very “hand built” feel to it all.
Once assembled it is taken apart, totally stripped down, for cleaning and washing before being carefully reassembled in a dust free room.
The focus is checked for each increment with the scales then engraved specifically for that lens. Cooke /i lenses (we’ll come on to those later) are computer soak tested to continuously monitor readouts of metadata that will be used in post production.
After around 3 month (given normal assembly schedules) from leaving the raw moulding store the finished hand crafted lens is ready for packaging, shipping and production!

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