[ATMoB-discuss] Canon internet Optical Mfg. Video

[Paul Valleli]

An STM member has announced an interesting web video about the latest 
technology that Canon
is using to make camera lenses (relatively) cheaply.

It is located at:

http://web1.canon.jp/camera-museum/tech/l_plant/index.html


The 500mm F/4 lens shown in the Canon Video sells for $5500 at B& H 
Photo-Video in NY.
It is designed for DSLR applications and has Ultrasonic Motors for 
autofocus and Image Stabilization.
I estimate the same lens made in America would cost around $50,000 in 
limited production.

I have the 400mm F/5.6 without Stabilization for astrophotography. It 
cost only $1050 for a 77mm diam. semi-Apochromat.
It is an APO from a photographic standpoint but there is a tiny 
amount of purple flare when used visually at high power.

The mechanized processes Canon uses include LN2 chilling of the glass 
to obtain small chunks with all the same melt data. Schott uses small 
pots which make it difficult to re-order the same type of glass.

Canon show's acetylene flame cutting followed by air chilling, which 
allows  large slabs to be "snapped off" with squared edges.
It can also be done using a high power laser.

Polishing of spherical lens surfaces is done using toroidal laps of 
polurethane. The method was invented by George Fabich while working 
at United technologies. George used to work at Itek, a long time ago.

The lens must be driven in rotation to prevent astigmatism. This 
process is difficult to get the lap in shape, but once there, it 
holds figure for many days and many lenses.

It works even better if a "bruising tool" is used as a lap conditioner.

I like the rimless finger cots shown - it eliminates the problem of 
some assemblers suffering loss of circulation and blood clots.
I wonder if anyone makes them in the USA?

I suspect that all the white tooling used for lens handling is not 
Teflon, which is unstable and difficult to machine accurately, but a 
similar polymer which is not prone to scratch and is hard enough to 
be diamond machined to a polished surface.

They did not cover the process of high precision optical cementing - 
that is a real craft.

Paul