MicrobeHunter.com Microscopy Forum

Update: this objective weighs 309 grams

That's amazing. Hopefully weighed down by tons of image quality.

That is my hope as well Apparently it takes a lot of glass to build a Plan low mag lens. In comparison the high mag Plan Apo IK Iris lenses on the Polyvar seem almost weightless.

I do like the prospect of having this low mag option on board. Who knows, after some years maybe I'll have a second, low mag revolver separately from a high mag one (with the oil immersion objectives). With a 1.25x, 2x, 4x, 10x and a 25x plus the Polyvar mag changer, one is pretty close to having a zoom from 10x to 312.5x

I have heard that some Polyvar objectives for reflected light EPI actually are DIC compatible even though they don't have the 'IK' marking. Nevertheless, I assume none of the low mag objectives for transmitted light that lack the 'IK' marking will be of any use for DIC. But perhaps they will all be useful for reflected fluorescence.

Rorschach wrote: ↑

Wed May 24, 2023 5:03 pm

I assume none of the low mag objectives for transmitted light that lack the 'IK' marking will be of any use for DIC.

My understanding for suitable DIC objectives

• low strain (e.g pol)

• back focal plane available for Nomarski prism

• matching condenser prism

• patience to sort prism alignment and matching

Unsuitable objectives either have back focal planes inside threads or strain distorting polarization.

All Reichert objective were built to a strain free standard so they were conditionally strain free. Those marked suitable for IK were selected as the most strain free and optimized for work in POL applications. . Keep in mind, that strain can be introduced simply be overtightening an objective in the nosepiece.

wabutter wrote: ↑

Thu May 25, 2023 11:27 pm

All Reichert objective were built to a strain free standard so they were conditionally strain free. Those marked suitable for IK were selected as the most strain free and optimized for work in POL applications. . Keep in mind, that strain can be introduced simply be overtightening an objective in the nosepiece.

That is very interesting and useful to know! Seems like the Reichert philosophy really was to offer 'universal' objectives that would work with most contrast methods. That is a big difference from most other quality brands of that time who offered specialized sets for almost all different uses.

I guess the limiting factors then would be the condenser prism compatibility and the location of the back focal plane.

Keep in mind that the back focal plane was not a big issue because even in the era of finite optics, Reichert upper prisms for DIC had the ability to move the prism vertically relative to the back aperture. Meaning only one prism was used for all magnifications

wabutter wrote: ↑

Fri May 26, 2023 9:32 pm

Keep in mind that the back focal plane was not a big issue because even in the era of finite optics, Reichert upper prisms for DIC had the ability to move the prism vertically relative to the back aperture. Meaning only one prism was used for all magnifications

Even better then! I like the prospect of having the possibility for a very low magnification DIC, in this case 10x or even lower (with lower mag eyepieces). Obviously it opens up possibilities Especially if it's possible to use different contrast techniques simultaneously on the Polyvar, i.e. DIC + polarization, DIC+fluorescence etc.

This thought led to the question: which are the possible and impossible combination of simultaneously usable contrast techniques on the Polyvar for transmitted light (and for reflected light, respectively)?

The fact that DIC is a polarized light technique, it would stand to reason that POL and DIC would be used simultaneously. Combining RL and TL contrast methods are certainly possible. RL Fluorescence with TL DIC or Phase or even simple POL is often done and certainly was one of the advantages of the Polyvar using the universal objectives. The Univar simplified this even more, by not needed a phase objective and offering the various phase contrast range for dark contrast, bright contrast, b- and anoptral phase objective rings. Of course the need to combine these methods is highly dependent on the optical characteristics of the sample

Interesting and verifies what I thought. Regarding pol, I only have the basic pol cube that goes above the revolver (the one that does not have any dials, levers etc.). If I could find the polarizer unit that goes on the outlet of transmitted light, under the condenser, that would give simple transmitted pol, I assume? Perhaps a DIY polarizer could do down there as well, as long as it can be rotated. Or am I completely in the woods here? Maybe one of those pol sliders (and which?) would be needed in addition to the pol cube? Regarding simple reflected pol, I am not sure which parts would be needed.