Can't focus phase contrast kit

[littlethings]

I just bought a new MD827S30 with the A1PHD phase contrast kit, but I'm unable to get any kind of image whatsoever with the PH installed.
The manual is online here, and I followed it exactly. Matching ring plate 40x with PH40x, used CT to focus the dark ring. All the descriptions of the light ring are pretty far off though.
There's not just one, there's 0-3 light rings depending on the condenser focus height, and none of them match a single photoshopped white ring.
I gave up trying to match the manual, and started running through all the different condenser focus heights, combined with different stage heights, but still no luck. All I get is a bland yellowish image that has nothing but dust specks on it.
I tried to take a picture of the CT view, but it's pretty hard to capture it on a phone camera. I had it half covered with a paper to highlight the difference. https://imgur.com/a/WCYIIID

Any tips on what to try next?

[MicroBob]

Hi,
I would suggest this:
-10:1 objective, phase stop out of the way, light on, condenser full up, field stop wide open, condenser aperture wide open
-slide with object and coverslip on the table
-focus on object - do you have a clear image?

-bring in phase stop, install phase telescope
-adjust position of phase stop so the ring matches the ring in the objective
-replace normal eyepiece - do you get an image now?

Bob

[PeteM]

In addition to Bob's suggestions, a properly matched set of phase rings and phase objectives should match up when the condenser height (and image focus, as Bob says) are set for Kohler illumination. Your condenser top lens probably wants to be set fairly close to the top of the stage.

I assume you have a phase telescope to get the rings aligned?

[apochronaut]

You don't mention what the subject is you are focusing on. You need to focus on a subject in BF first without the phase insert installed. Don't touch the focus, when you install the phase annulus and go through the routine to focus the two rings and center the one in the condenser. There should be no oil on the condenser. Is it possible that the iris diaphragm is partially closed and off center, giving you a sort of oblique lighting condition?

[wporter]

As you, and the others here, have pointed out, the instructions in your manual leave something to be desired. To rehash the other good advice, if I was to re-write the manual, I'd make the following changes:



A) Go to manual page 15, section 8.1. Do steps 1) and 2).



B) Then, for manual step 3), substitute:

"Swing into place the 10x phase objective".



C) For manual step 4), substitute:

"Set the phase condenser turret on B; put the specimen slide on the stage, turn on the light, adjust the light brightness, and focus on the specimen. Place a card with a 1/8" pinhole on top of and centered on the light collector (part 8); raise or lower the condenser with knob 21 until the pinhole is in focus (as is the specimen, visible through the pinhole). Remove the pinhole card.
You should now see the focused specimen in normal brightfield appearance, only using the phase objective (not much different looking than with the 10x non-phase objective)."


D) rotate the condenser turret off of B to the 10 setting. You are now in phase observation; you should notice a significantly different appearance to the specimen; if necessary, you may now align the 10x condenser phase ring with the objective phase ring: insert the CT in place of one of the eyepieces, and go through the manual's steps 5a through 5e (skip g, you already did this).


E) to increase magnification, rotate in a different phase objective, and use the corresponding condenser turret setting. You probably will have to align the new phase rings for this higher mag. Once you align them all, they should be pretty close from then on.

[littlethings]

Thanks for the replies! I took the advice of going back to 10x to get the initial focus, then successfully moved back up to 40x and managed to find the focus. Successfully checked out some various molds, blood cells and other random critters!


Phase contrast focus seems quite fiddly, I accidentally put the 10x condenser with the 40x objective and it seemed to have better focus than the 40/40 for some slides.
I've read in multiple places that phase contrast is closer to art than science, so I'll keep on fiddling.

[Hobbyst46]

I've read in multiple places that phase contrast is closer to art than science, so I'll keep on fiddling.

Phase contrast is certainly science, since there exists an absolute theoretical maximum contrast. The "art" is how close to the maximum contrast can one reach with the equipment, given the interfering side effects.

[apochronaut]

Thanks for the replies! I took the advice of going back to 10x to get the initial focus, then successfully moved back up to 40x and managed to find the focus. Successfully checked out some various molds, blood cells and other random critters!


Phase contrast focus seems quite fiddly, I accidentally put the 10x condenser with the 40x objective and it seemed to have better focus than the 40/40 for some slides.
I've read in multiple places that phase contrast is closer to art than science, so I'll keep on fiddling.

Phase contrast requires a fairly precise slide and cover slip thickness in order to be optimized. Any deviation from the optimum will result in changes to the phase shift and therefore alter the results. Many prepared slides are very thick; as much as twice the optimal thickness, which will distort the image but also possibly create a circumstance for unusual combinations and results.You may have a low power objective( 4 or 5X). Using one of those with the large( 100X) annulus usually provides a good low power DF image.