Archived posting to the Leica Users Group, 1998/06/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 10:48 AM 6/10/98 , Frank Dernie wrote: heir swinging device? Also, on another tack what is a circular polariser? >If orhtogonality of polarised light is required for cancellation as I >understand it what is a circular polariser doing and how does it , for >example cancel a reflection? A circular polarised filter is simply a linear pol to filter the light based on the polarization, followed by a 1/4 wave plate, which randomizes the polarization of the transmitted light. (Warning: my recollection of what little optics I've learned is shaky. Maybe it's a half-wave plate, or something like that.) The basic upshot, though, is that it's a simple linear pol, followed by another filter which takes the polarized light which makes it through the first filter and randomizes the polarization. This only makes a difference if the stuff behind the filter is sensitive to the polarization of the light that reaches it. Two obvious candidates would be metering and autofocus sensors, often located behind half-silvered mirrors, etc. Doubtless I've screwed this description up somehow, especially since I'm suffering from a wicked headache. Perhaps this error will provoke one of the more optically expert to give us the complete story. - -Paul