Lens Trivia Question (15 Points)

A trivia question, hopefully to be answered by someone who really knows the answer: were the aspheric lens elements in Kodak Disc Cameras (the last lenses in which Rudolf Kingslake had a hand, I believe) glass, or plastic, or hybrid? My memory is they were press-moulded, but made of some sort of optical plastic or resin, although the spherical elements were glass.

Anyone know for sure? IMWTK.

Mike

ANSWERS: Kevin Purcell tracked this down, from Geometrical and Instrumental Optics by Daniel Malacara, Academic Press, 1988, p. 94, Chapter 3.4.11, "Aspheric Surfaces in Camera Lenses":

And this from Applied photographic optics: lenses and optical systems for photography, film, video, electronic and digital imaging by Sidney F. Ray, Focal Press 2002, p. 173, Chapter 18.4.4, "Design, manufacture and testing of a lens":

Oren Grad notes that the Wikipedia entry cites an article in the April 1982 Modern Photography magazine as a source. He didn't have that within easy reach, but pulled the 4/82 Popular Photography and found this in an article introducing the disc system:

"The lenses are made out of four separate coated glass elements, including one aspheric element to get the maximum sharpness and minimize lens aberration. As my colleague Norman Goldberg pointed out, the disk camera lens is in effect a high-quality microscope objective."

He says there's also a little comment directly from Norman Goldberg, including the following:

"Kodak's disk-camera lens may be the best ever made for an amateur snapshot camera.  It's a 12.5mm ƒ/2.8 all-glass, air-spaced triplet with a field-flattening fourth element.  The third surface from the front is aspherical, until now something that was possible in large numbers only when molded from plastic...."

I'd say Kevin gets 8 points and Oren 7, meaning that they only have 7,992 and 7,993 points to go, respectively, and they each win a Porsche!

But seriously, thanks to Kevin and Oren.

P.S. Ctein was right (see the Comments Section).

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Featured Comment by Tim Wilson: "They were all glass, including the aspheric lens. Kodak developed the process of Precision Glass Molding (PGM) which could mold the glass aspheres. While I was not directly involved in the PGM process, my department would often make thousands of the precision glass blanks (nubbins) that went into the machines, especially as the project was just getting started. The PGM process (along with the rest of Kodak's commercial optics fabrication capability) was sold to an investor who formed Rochester Precision Optics, where the PGM process lives today."

Comments

[James B]

"Kodak’s high quality disc camera lens, used in their earlier disc cameras, consisted of 4 glass elements with a focal length of 12.5mm at f/2.8, offering a 58° angle of view. Unlike conventional lenses the second element was an aspheric lens designed to correct spherical aberrations. An aspheric lens was required for its compact design and fast aperture. Without it, extra lens elements would have been needed, adding to the size."

...from http://disccameras.wordpress.com/ I have no idea at all if this is an authoritative source. There's also http://en.wikipedia.org/wiki/File:KodakDiscAspheric-text.svg which shows the lens arrangement and also claims it is glass.

Leica talk of a hybrid form (see digital p12, col 3, para 2 of the Leica lens catalogue at http://en.leica-camera.com/assets/file/download.php?filename=file_1750.pdf )

My guess is that Leica know what they are talking about.

[mark lacey]

Try the Rochester Optical Works website, proptics.com, search under 'Precision Glass Molded Aspheres'. That makes it quite clear it was glass not plastic, and they made them so they should know. I would post a link but I'm prehistoric with that sort of thing.
All the best, Mark

[James Powers]

Plastic, if I remember correctly.

[hugh crawford]

I remember that the Kodak Disc Cameras and the Olympus XA Cameras were interesting because they both had telephoto wide angle lenses. I suspect that some of the camera phones employ telephoto wide angle lenses but have not read anything about it. I remember trying to explain how a Olympus XA had a 35mm telephoto lens. It was almost as bad as trying to explain how the smallest size drink is a "large"

[Steven ralser]

Here's a link I found in google - it says glass

http://disccameras.wordpress.com/2011/08/20/remembering-the-1980s-kodak-disc-camera/

[David]

High quality glass paired with miniscule frame size. I don't remember ever seeing a picture from a disc camera that showed the quality of the lens. It may as well have been cheap plastic.

[JH]

The people we worked with on the fiber optic project said glass. The ones used in the fiber optic project were quite complicated glass moldings, cylindrical, about 4mm diameter and 10 mm long, with a inset lens on one end and an optical flat on the other end.

[Patrick Perez]

I see the answer was already provided, but the datum the question triggered in my brain was this: The single greatest contributor to the successful commercialization of molded aspherical lenses was the optical systems of Compact Disc players, during the 1980s. I doubt the Disc Cameras were even 1% of the unit volume of CD players in that decade (or, well, any decade). But Of course, the Disc format did give us advancements in film formulation (isn't T-Grain a result of that format's development?)

I don't know much about lens design, but I know LOTS of trivia about an astounding number of topics.

Patrick

[Pak-Ming Wan]

That's some serious crowdsourcing going on here! Well done everyone!

I remember handling one of those disc cameras when I was a kid and I always was amazed that it actually was a camera -- it looked nothing like anything I had seen before. But perhaps I was its only target audience: someone who cared more about a gimmicky camera than the photos.

Pak

[Bruno Masset]

U.S. Patent #4,139,677 seems related to the topic ;-)

[Bob Rosinsky]

Weird cameras, those Kodak disc contraptions. I remember the pictures always looked grainy.

[David Dyer-Bennet]

I remember the disc cameras saying they had designed the lenses to focus on the curve the film actually took in the cartridges, rather than on a theoretical flat plain. That seemed very advanced and daring at the time -- and still does, actually. In some sense this feels like an early outlier of the current practice of correcting some lens defects in hardware, rather than trying to build a lens without any defects.

[Eamon Hickey]

For those interested in how Kodak's original technology has been extended, there's a "behind the scenes" article on Nikon's Japanese web site that discusses the development of the 14-24mm f/2.8 and 24-70mm f/2.8 lenses, both of which use very large diameter, radically aspherical PGM lens elements.

The article has more than its share of the cringe-worthy "with joyful hearts, my colleagues and I strove for the glory of the company" sorts of commentary (forgive them; they know not what they do), but it has some interesting tidbits on the interplay between the design and manufacturing engineers over what could and could not be manufactured.

And it's got some interesting pictures of the elements themselves, which are quite visibly large and weirdly shaped. It's here:

http://imaging.nikon.com/history/scenes/25/index.htm

[Semilog]

Note also that the Kodak disc was not the first mass-market camera to use an aspherical element. That was the Polaroid SX-70, so far as I know -- a decade earlier.