I haven't purchased any lenses yet. I've been looking on eBay and
http://www.surplusshed.com/lens.cfm Cost is a major concern. Surplus shed has better specs on the lens but they are $3.50 apiece with a minimum of 10 lens. Multiply by 45 lens then more then I originally wanted to spend. The ones on eBay are under $15 for 50 lens but nothing stated about focal length just the size of the lens.
From the ETF site
http://www.earlytelevision.org/weste...storation.html
"The scanning disc used with the new motor was aluminum and about 8 inches in diameter. Forty five lenses about I cm. in diameter and having a focal-length of 1 inch were arranged in three interlaced spirals. It was important that the optical centers of the lenses be accurately located to provide a uniform scanning field without dark lines."