Microscopy Forum

Oliver said

Hello,

I think that I will soon write a separate post on this, because the question of infinity corected objectives has already appeared several times. I'll therefore keep myself short in this answer.

1. No, it is not possible to use infinity corrected objectives on the "traditional" DIN microscopes (which have a tube length of 160 mm). The DIN standard is very common and allows for an exchange of objectives from different manufacturers. The threading is even different, so they won't fit.

2. It is also not possible to exchange inifinity objectives between different manufacturers. The tube lens is responsible for not only converging the light of the objective but also correcting lens errors as well and this depends from manufactuerer to manufacturer on how this is done.

3. Many low cost microscopes (as in the use of schools) use traditional DIN objectives becasue of exchangability.

So, what's the whole idea behind infinity objectives? These objectives require an additional lens inside (tube lens) the tube of the microscope. Infinity corrected objectives alone create a parallel light beam (in contrast to DIN objectives, which create a real image). It is therefore possible to introduce filters into the light beam without changing the focus (filters will not change focus of parallel light).

The term "infinity" refers to the fact that these objectives create an image (without the tube lens) in infinite distance, this means never. The light beam does not converge and is parallel.

Oliver.

Hi,

Sorry to bump an old thread.

Oliver, I disagree with the first sentence in item 1 of your post.

I have experimented with infinity corrected objectives on a 'traditional' 160mm DIN microscope, the objectives mentioned being a Meiji S Plan M 5x, 10x and 20x metallurgical objectives.

The 5x didn't work, I couldn't get it to focus at all but the 10x and 20x worked very well. Having said that, the images obtained were low on contrast, less punchy than, say, a generic no name standard achromatic but still acceptable for casual observation and they focused at a longer working distance to an equivalent magnification standard achromatic. All three lenses are standard RMS fit.

Rob.