cataracts, bandpass filters

John Larkin · 2012-11-25T21:28:40+00:00

It's time for me to get cataract surgery. I think I'll go for the fixed-focal-length lenses, maybe with astig correction. I've always been nearsighted, which suits me fine, since I read a lot, compute a lot, and work with tiny parts on PC boards. I can wear glasses to drive or ski or whatever. So, what should the focal lengths be? I've noticed that two eyes have a lot better resolution than one, even if one isn't well focussed. Brains integrate the images somehow. Some people go for one eye close-focussed, and one at distance, so they don't use glasses at all, but I have another idea: Focus one eye really close, like 10" maybe, and the other at computer distance, 20" maybe. Ideally, that will give me good resolution from, say, 8 to 24 inches. Something like this: There would be a box that defines a minimum resolution over some range of distances. This is starting to look a lot like a Chebychev bandpass filter, and I guess the math is similar. I could also get a flat Butterworth looking curve if I moved the peaks closer together, but that would reduce the working range. The complications are: Pupil size changes with illumination, so the two peaks get narrower in dim light. I don't know how well a brain combines two inputs; probably better than just summing amplitudes. So the peaks could be farther apart than simple math suggests. And, of course, I have to convince the doctor that I'm not crazy.

Nov 25, 2012 61 Replies

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Spehro Pefhany 13 years ago

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(shorter version of above)

Best regards, Spehro Pefhany

"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

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dagmargoodboat 13 years ago

I can look at you straight with either eye, and make the other wander sideways. Good circus trick.

I also learned in 2nd grade that you can lift your tongue, tense the root of it, and squirt streams of saliva several feet, like a spitting cobra. Handy. Suppose, for example, you met a hot spitting cobra and wanted to impress her...

Cheers, James Arthur

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