Thanks, Pau. I'm pretty familiar with the uses and benefits of cross pol lighting, and am working on implementing it in my rig. This why your approach is of strong interest to me--seeing how other people do things, and especially, hearing what went wrong (like the holes burning through your polarizers) is very helpful.
Pau wrote:In my setups I use a high quality microscope analyzer (Nikon) and plastic inexpensive polarizers at the fiber optic ends. With better ones the effect would be a little better.
I have an Olympus analyzer on order. I'm not sure yet how I'll mount it in the optical path of my horizontal rig. The easiest way would be to place it in a small lens tube with appropriate mounts on the front and back, and place this between bellows and objective. But more ideally, I'd like to be able to remove the analyzer for brighter focusing, and then put it in place without affecting the focus or position--which means not having to remove the objective. I'd love to put the analyzer between bellows and camera, but suspect that such a small polarizer would cause vignetting if placed there. Larger polarizing filters are of course widely available, but using an analyzer from a microscope assures me of appropriate quality for this purpose.
In your setup, you apparently remove the objective mount to place your analyzer between objective and zoom lens. Does the analyzer simply fit in between and gravity holds it in place, or do you have some sort of mount for your analyzer?
Usually I don't use focusing lenses, but one time I placed them over the polarizers. The internal lens surface focused reflected ligth on the filter, and now I have a burned spot in the center of each one. To prevent it in the future I placed a heat (IR) cut filter (form a salvaged slide projector) between the bulb and the fiber optic inside the illuminator, and I'm going to order 2 new polarizers (likely form Edmund Optics), and the focusing lenses will be rear the filters.
Interesting. I thought most illuminators already had pretty good IR filtration? What kind do you have? I have an old slide projector that I'll likely cannibalize for things like the IR filter for an illuminator that I'm making, but wouldn't have thought it necessary to add one to a factory-made unit.
Any idea how you will mount the Edmund polarizers in front of the focusing lenses? I'm thinking of using Edmunds as well, with a bit of epoxy to affix each to a slightly oversized tube, and adding a thumb screw for tightening--rather like what you have apparently done here. Of course, that would mean loosening the screw for filter rotation, which I'd rather avoid.
The adapters were made with a plastic plumbing tube, an old microscope filter holder and a screw.
This is the part that most interests me, and any more details you care to provide may save me time when making my own. Your detail shot of the fiber optic ends with polarizers certainly doesn't look anything like something made from plastic plumbing pipe--nice work indeed. They looked like something purchased off-the shelf, and if so, I'd consider buying a set myself.
Thanks much,
--Chris