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#11
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Prism Diagonal Anti Chromatic Aberration Effect?
In article , optidud wrote:
Yes, I've realized the Spherochromatism is not the same as primary color error and I've consulted many references about this a while ago. But there is something that eludes me and I wonder if I'd figure it out by simply sketching on paper. They say that when spherochromatism is corrected for green light, it is undercorrected in red light and overcorrected in blue light, Which means that in red light, the outer rays focus closer to the lens than the paraxial rays, and the opposite is true in the blue. Spherical aberration is called spherical aberration because lenses and mirrors that have surfaces that are segments of a sphere have the unfortunate property that rays focused by the edges of the lens don't come to the same point as rays focused by the center of the lens. The lens designer can minimize the amount of spherical aberration by selecting the right curves for his lens. The lens curvatures for best correction of spherical aberration depend on the index of refraction of the glass, which changes with wavelength of light. With an ordinary achromatic lens the designer can get best correction for spherical aberration at one wavelength. At other wavelengths you get more spherical aberration. For visual telescopes they engineer the lens so the correction for spherical aberration is best at wavelengths where the human eye is most sensitive. |
#12
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Prism Diagonal Anti Chromatic Aberration Effect?
Hey, I know what is spherical aberrations and spherochromatism.
There's just something I can't figure out. Suppose an objective lens has spherical aberrations corrected on the color green. The author said it would be uncorrected in color red, meaning the red outer rays would focus closer to the lens than the center. If you will recall that in a thin lens, the red is the one farthest away from the lens while violet is the one nearest the lens. Now if you optimize a lens specifically the outer rays for the color green. If red light comes from the same lens. The red outer rays should be refracted and end up farther away from the lens, yet the author said it should be nearer the lens. I searched all the archives here but can't find the answer. So if anyone knows the answer to this, lemme know. Don't make me antagonize for days figuring out why Thanks. optidud William Hamblen wrote in message arthlink.net... In article , optidud wrote: Yes, I've realized the Spherochromatism is not the same as primary color error and I've consulted many references about this a while ago. But there is something that eludes me and I wonder if I'd figure it out by simply sketching on paper. They say that when spherochromatism is corrected for green light, it is undercorrected in red light and overcorrected in blue light, Which means that in red light, the outer rays focus closer to the lens than the paraxial rays, and the opposite is true in the blue. Spherical aberration is called spherical aberration because lenses and mirrors that have surfaces that are segments of a sphere have the unfortunate property that rays focused by the edges of the lens don't come to the same point as rays focused by the center of the lens. The lens designer can minimize the amount of spherical aberration by selecting the right curves for his lens. The lens curvatures for best correction of spherical aberration depend on the index of refraction of the glass, which changes with wavelength of light. With an ordinary achromatic lens the designer can get best correction for spherical aberration at one wavelength. At other wavelengths you get more spherical aberration. For visual telescopes they engineer the lens so the correction for spherical aberration is best at wavelengths where the human eye is most sensitive. |
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