Wanted: 30x Microscope Objective

Jem · Post by **Jem** » Mon Jul 26, 2010 8:17 am

Hi

Does anyone have a 30x microscope objective laying around that they want to part with?

It *has* to be a 30x. I have plently of 20x, 40x and 60x, but this is for a specific job and only 30x will do

Must be in excellent condition and a reasonable price. Please PM me.

Thanks

Jem

BobH · Post by **BobH** » Tue Jul 27, 2010 1:19 am

The Holy Grail of microscope objectives!

I had one, but it was sold in the '90s with a bunch of my equipment. Wish I'd have kept it. Good luck with your search. They do exist.

Jem · Post by **Jem** » Tue Jul 27, 2010 2:39 pm

Thanks Bob

I'm sure there'll be one somewhere. I have an 8" f3 collimating mirror. 20x doesn't expand the beam quite enough & 40x wastes a lot of light from overspill. 30x would be about right for a perfectly collimated beam with no waste.

Cheers

Jem

dave battin · Post by **dave battin** » Tue Jul 27, 2010 4:32 pm

why not stick a weak meniscus lens in front of the SF and get it to expand a little faster? it needs to be good lens to work properly ...........

This is a earlier set-up i had doing DCG, you can see the lens in front of the Spatial Filter ..............

if this laser is a green one, just let the beam run further down stream before entering the spatial filter and then it will have a higher output spot diameter :think:

Jem · Post by **Jem** » Tue Jul 27, 2010 8:28 pm

Hi Dave

Yes, I had thought of putting a lens in front of the SF. The problem is that the whole purpose of using the SF is to get rid of artifacts in the beam. But, by putting a lens in front you just re-introduce the artifacts again.

If all else fails, that's the route i'll take, but I thought I would see if I could pick up a 30x objective as the first option

Cheers

Jem

dave battin · Post by **dave battin** » Tue Jul 27, 2010 11:26 pm

Jem wrote:Hi Dave

Yes, I had thought of putting a lens in front of the SF. The problem is that the whole purpose of using the SF is to get rid of artifacts in the beam. But, by putting a lens in front you just re-introduce the artifacts again.

Jem

by using a weak lens these artifacts wont come to a focus and should not be an issue. On the otherhand a powerful lens will focus and show these artifacts ................. try it and you will see

i dont really see these issues with this hologram?

Jem · Post by **Jem** » Wed Jul 28, 2010 11:33 am

dave battin wrote:by using a weak lens these artifacts wont come to a focus and should not be an issue. On the otherhand a powerful lens will focus and show these artifacts ................. try it and you will see

Interesting. I'll give it a go and see what happens. I was always under the illusion that anything optical after the SF was bad.

Cheers Dave

Jem

BobH · Post by **BobH** » Wed Jul 28, 2010 1:24 pm

you can also change the beam diameter going in to the spatial filter to get more or less spread from a given microscope objective. The pinhole will be the last component in line. Try a weak negative lens way upstream, or a beam expanding telescope (the best thing). You can be filling the input aperture of the objective, and typical laser beams don't (especially diode laser beams).

dave battin · Post by **dave battin** » Wed Jul 28, 2010 1:38 pm

BobH wrote:you can also change the beam diameter going in to the spatial filter to get more or less spread from a given microscope objective. The pinhole will be the last component in line. Try a weak negative lens way upstream, or a beam expanding telescope (the best thing). You can be filling the input aperture of the objective, and typical laser beams don't (especially diode laser beams).

these 315 and 215 lasers have a heavy divergence so just by allowing the beam to run a little longer, (as stated previously) before it hits the SF will acheave the same thing. Vintage holographers my not realise this, as they are spoiled by the narrow outputs via gas lasers. :whistle: