henry link
Well-known member
Ed,
Yes, I'm sure about the singlet focusing lenses in binoculars. I've seen cutaways of Nikon, Zeiss, Leica and Swarovski that all show the same thing. I recall seeing a doublet focusing lens in a binocular only once and that was the Kern Focalpin Porro of about twenty years ago. I expect the patent is referring to correcting CA for more critical high magnification uses, like telescopes.
Henry
BTW, there is a very obvious increase in spherical aberration visible in a star test when an astronomical refractor corrected for infinity is tested at a short distance. I noticed this again recently when using an artificial star at about 10m compared to the same telescope at infinity. Of course, those scopes don't use focusing lenses and are only really well corrected for distances beyond about 50 times the focal length of the objective.
Yes, I'm sure about the singlet focusing lenses in binoculars. I've seen cutaways of Nikon, Zeiss, Leica and Swarovski that all show the same thing. I recall seeing a doublet focusing lens in a binocular only once and that was the Kern Focalpin Porro of about twenty years ago. I expect the patent is referring to correcting CA for more critical high magnification uses, like telescopes.
Henry
BTW, there is a very obvious increase in spherical aberration visible in a star test when an astronomical refractor corrected for infinity is tested at a short distance. I noticed this again recently when using an artificial star at about 10m compared to the same telescope at infinity. Of course, those scopes don't use focusing lenses and are only really well corrected for distances beyond about 50 times the focal length of the objective.
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