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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/19/2008 at 22:08
littlevineyard1 View Drop Down
Optics GrassHopper
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 i am confused on the subject of "phase corrected binocular lenses. can anyone explain what this terms means and its application for binocular use? thank-you
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/20/2008 at 09:46
Klamath View Drop Down
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As I understand it, as the light beam passes through a roof prism binocular as it leaves the second of the three prisms, the light is split into  bands of color.  As I understand it, this condition of the light beam is "out of phase".  The third prism has the  duty of putting the light beam back "in phase" by reassembling the bands into a visible image.  This was the weak point in roof prism optics for a long time.  In early models, this forcing of the light back into phase caused a loss of optical quality and light transmission.  Only so much could be done with improved glass, engineering, and workmanship.  Eventually (1988 I think) Zeiss, then Leica discovered how to coat the prisms to largely eliminate the out-of-phase-back-into-phase problems.  The process was at that time technically demanding, time consuming, and thus expensive.  In 1995-96 Pentax offered the first mid-priced phase coated binocular and within a year or two mid priced phase coated binoculars were pretty common.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/20/2008 at 09:58
Klamath View Drop Down
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As the light passes through a roof prism binocular, the second of the three prisms splits the light into a rainbow like beam of the various light spectra.  The third prism has to force this "out of phase" beam back into a visible image.  This was the weak point in roof prism image quality for a long time.  In about 1988 Zeiss and then Leica figured out how to coat the prism to drastically reduce the image quality loss in the "put it back into phase" operation.  Hence the term phase corrected or phase coating.  The human eye had to play a large part in the final image correction process in non coated binoculars, so, if you use a non coated binocular for much time, you will eventually notice that the image won't focus right and that you can even get a headache.  By 1995-96, Pentax introduced the first phase corrected mid priced binocular.  They sold a bunch of those.  In a year or so phase corrected mid priced binoculars were common.  This phenonenon does not occur in a porro prism glass, so phase coating is not needed there.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/25/2008 at 15:14
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