by Joe Farina » Fri Jan 17, 2014 5:39 pm
Thank you Dinesh. As always, your help is appreciated. I made a mistake saying "convex" lens instead of "concave" but by suggesting the negative lens, you corrected it. My negative lenses don't provide a lot of expansion, that's probably the main problem.
I have a very tiny ball lens, maybe around 1.5mm diameter, but always had trouble using it, due to the small size. But since you mentioned it, I now remember that I have some Pyrex balls which are bigger, 5/32 and 1/4 inch in diameter. These are definitely worth a try, thanks for the reminder.
By the way, in case anyone is interested, they have a surprising amount of Pyrex items at McMaster-Carr, and they are quite cheap. These are a good alternative to the much more expensive items from optics suppliers. I've recently bought balls (optical quality), plates up to 3/4 inch thick made using the Borofloat process, tubes, and rods.
Thanks also for the focal length formula, and the suggestion of the swizzle stick as a cylindrical lens. Also, as you mentioned, I'm finding that multiple lenses seem to mess up my fringes, much cleaner fringes were obtained with one or two lenses. That's a good point about the importance of the interbeam angle, it's something which needs to be kept in mind.
Thank you Dinesh. As always, your help is appreciated. I made a mistake saying "convex" lens instead of "concave" but by suggesting the negative lens, you corrected it. My negative lenses don't provide a lot of expansion, that's probably the main problem.
I have a very tiny ball lens, maybe around 1.5mm diameter, but always had trouble using it, due to the small size. But since you mentioned it, I now remember that I have some Pyrex balls which are bigger, 5/32 and 1/4 inch in diameter. These are definitely worth a try, thanks for the reminder.
By the way, in case anyone is interested, they have a surprising amount of Pyrex items at McMaster-Carr, and they are quite cheap. These are a good alternative to the much more expensive items from optics suppliers. I've recently bought balls (optical quality), plates up to 3/4 inch thick made using the Borofloat process, tubes, and rods.
Thanks also for the focal length formula, and the suggestion of the swizzle stick as a cylindrical lens. Also, as you mentioned, I'm finding that multiple lenses seem to mess up my fringes, much cleaner fringes were obtained with one or two lenses. That's a good point about the importance of the interbeam angle, it's something which needs to be kept in mind.