We sometimes discuss how a Schmidt-Pechan prism is not totally internally reflective at all surfaces, and generally applaud the new dielectric coatings which give over 99% reflectivity, enabling the SP to compete with Porros and AKs for brightness.
But, isn't the reflectivity of a phase-altering coating, like on top roof prisms of either style, an issue too? Seems to me like the first layer next to the glass has to have an index just right, to coax the light through the glass boundary instead of total internal reflecting, into the layered coating region, and once that happens, you can lose some light, right? How reflective are these things?
I'm sorry this is so picayune that it's almost ridiculous. Please don't hate me, Brock and other right-brainers. I love birds too, honest. I've just been walking around in a daze around wondering about this, somebody help me.
Ron
You raise a good point.
It is a wonder that optics producers can tailor the physical properties of their coatings, including hardness and water shedding for the external surfaces of the lenses, without destroying the light transmission performance.
Any of our pros want to enlighten us a bit?
RonH,
You may find this a fair starting point. http://www.mellesgriot.com/products/optics/oc_2_4.htm
I envision the layers akin to elements of a Yagi TV antenna