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Canon L lens factory tour

Cankin

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From 2017 Dpreview and Imaging Resources.

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From Imaging Resources:

Takumi Toshi Saito demonstrates the process of hand-shaping a master template used to make the diamond-grit grinding tools for lenses. The piece in his hand is a heavy polishing jig, this particular one weighing around 30 pounds (15kg), with diamond grit on the inside. The little plugs on the jig that he's grinding define the surface that the final tool will have. They have to be ground to within a tolerance of 30 nanometers (30 millionths of a millimeter). The tool he's using to do the hand-grinding doesn't exactly match the final target profile; Saito-san tweaks and adjusts the shape of the forming jig by adjusting the pressure as he slides the grinding tool over the jig. Normally, the jig is rotating while he does this, requiring a complex dance of pressure, angle, distance and timing. It was mind-boggling to us that someone could hand-grind something to tolerances in the millionths of millimeters.
 

restorer-john

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Well, I don't feel so bad now about the price of the 'L' lenses. Thanks for sharing.
 

Wombat

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This man should have been employed in the Hubble Telescope project. o_O
 

Blumlein 88

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Not to minimize the skill of these people. They in principle are doing what amateur telescope makers regularly do. Same basic process by hand. I'm sure they are good at it, and experience probably has made them fast with few mistakes. The general principles to grinding to such precision go way back in hand made lenses and mirrors. You get the basic shape, follow the procedure and do optical testing along the way and surfaces of incredibly small tolerances result.

Mentioning the Hubble as I recall it was a mistake in their formula that let it get made to the wrong shape. I also recall some wanted to do more traditional testing of the lens, but that was thought to be not good enough and time consuming. Yet a very simple Foucalt knife edge test would have revealed the problem had such a simple thing been done. The test was credited to Leon Foucalt in 1858. You can measure shapes in fractions of a wavelength in light this way. Which is in the nanometers range.

https://en.wikipedia.org/wiki/Foucault_knife-edge_test
 

JJB70

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Practice makes perfect as they say, the issue of organisations showing disdain to older techniques seen as old hat despite them remaining valid goes a lot further than the Hubble telescope. I used to do shaftline alignment for big (very big) power systems and some of the people who do that job still prefer taut piano wire to laser alignment tools and do the job quickly and to the required tolerances.
 
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