PHASE CONTRAST OBLIQUE LIGHTING

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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Greg Howald
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Joined: Tue Oct 20, 2020 6:44 am

PHASE CONTRAST OBLIQUE LIGHTING

#1 Post by Greg Howald » Wed Jun 16, 2021 2:28 pm

I HSVE BEEN PLAYING WITH OBLIQUE LIGHTING WHILE USING PHASE CONTRAST BY PLACING VARIOUS VSHAPES OF FILTERS ON TOP OF THE ILLUMINATOR. RESULTS HAVE BEEN INTERESTING AS I BEGIN TO CLOSE IN ON THE EXACT DESIRED EFFECT. IMAGES ARE OF A PREPARED SLIDE OF UTERUS SECTION AT 40X PHASE CONTRAST. I FOUND IT INTERESTING.
GREG
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UTERUS SEC 40X PHC OBLIQUE.jpg
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UTERUS SEC 40X PHC.jpg
UTERUS SEC 40X PHC.jpg (97.37 KiB) Viewed 204 times

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: PHASE CONTRAST OBLIQUE LIGHTING

#2 Post by apochronaut » Thu Jun 17, 2021 12:39 pm

This is something I have done a little with some fairly good results in certain cases. Some objectives, those with a higher contrast level seem to work better than others, giving a kind of phase contrast/DF quality especially if a larger phase diaphragm is used (40X objective with 100X annulus). The point of oblique at which I get an excellent result as opposed to a blah result is quite defined though, with even a small shift in either condenser direction, or diaphragm repositioning destroying the effect.
The most notable feature is the 3-D that can result, giving a kind of DF DIC effect . It is quite promising but there are only 2 objectives that I have gotten really good results with, with some others only fair. Both are quite odd in comparison to other objectives within their same series or made for their specific microscope and it makes me wonder whether they were specifically designed to be used in that way. There is no catalogue information avaiable right now, anyway.
Neither works very well when applied as a normal phase contrast objective but both work well in oblique and a carefully controlled illumination level and annulus overlap. Both are around 40X. One is a mid. to late 50's Spencer/AO 45X .66 Dark H phase achromat made for the AO series 4. If you peruse any extant lists of objectives made in that series, it doesn't show up. No Dark H objective does. In normal use, it produces way too much flare and seems like it might be defective.
The other is a Reichert 40X .70 planfluor. It has a very weird ultra narrow annulus and in normal use, it produces almost no phase effect. The standard 40X .66 planachro and 40X .75 planachro both have normal thicker phase rings and produce a rather conventional dark medium image. The planfluor produces a dark phase/field image with some relief in oblique, when used with the 100X phase diaphragm. The positioning of the annulus in the objective seems different too; lower in the lens column.
Phase is there to be played with for sure. It is anything but fully tapped.

Greg Howald
Posts: 639
Joined: Tue Oct 20, 2020 6:44 am

Re: PHASE CONTRAST OBLIQUE LIGHTING

#3 Post by Greg Howald » Thu Jun 17, 2021 2:57 pm

Gee thanks. I appreciate the added knowledge.
Greg

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