BFP1 latch on the Olympus DIC slider(s)

[Macro_Cosmos]

I have a UApo N 40x objective that asks for the BFP1 latch, thus officially incompatible with the normal U-DICT sliders. People often claim there is no difference between DICT and DICTS, I will demonstrate the opposite.
BFP stands for back focal plane. Most UIS2 objectives have a BFP of either -19.1 or -25. There are several exceptions and they require special condenser prisms, usually. I will ignore those. Olympus' objective selector will show this if you are interested.


Full resolution: https://live.staticflickr.com/65535/526 ... d562_o.png
- Normal position appears darker but background is uneven
- Colour variance
- Intensity variance
- With the BFP1 latch engaged, the image can be made very dark by engaging the translation knob. The normal position will always showcase a weird bright spot.
- Only applicable to this specific objective/prism combination. Others may see a more/less prone effect.

Boosted...

Full resolution: https://live.staticflickr.com/65535/526 ... 7745_o.png

Here is an animated illustration for the valve.

The BFP1 slider ensures that the extraordinary and ordinary waves split by the condenser prism gets combined correctly. It lowers the prism by around 6mm.
Is there a difference? Clearly, yes.
Does it matter? Probably not, background can be replaced/cleaned. The minute intensity difference/unevenness is hardly noticeable.
Does it depend on the objective? Likely, the effect could be more or less prone, but this is just a guess.

Enjoy.

[Pau]

Interesting comparison, thanks for posting it.

The difference is small -much smaller than I would had guessed.

The BFP1 slider ensures that the extraordinary and ordinary waves split by the condenser prism gets combined correctly. It lowers the prism by around 6mm.

Nice to know. I'm able to move the U-DICT vertically and even to tilt it in my DIC frankenscope but I haven't see any advantage doing it. Next time I mount the system I'll try again.

Most UIS2 objectives have a BFP of either -19.1 or -25

mm?
from the objective shoulder? Seems quite a lot being 45mm parfocal objectives. or...?
how is it measured?

[Macro_Cosmos]

Most UIS2 objectives have a BFP of either -19.1 or -25

mm?
from the objective shoulder? Seems quite a lot being 45mm parfocal objectives. or...?
how is it measured?

Yes, mm.
No idea how it is measured because the numbers do not seem to make much sense, perhaps it's DIC specific rather than the BFP of the objective.
Different magnification and NA objectives should have different BFP.

[rjlittlefield]

Here is an animated illustration for the valve.

My eyes are attracted by the obvious difference in geometry in these two images.

If these are stacked, then I worry that the geometry difference is an artifact introduced by the alignment process making slightly different decisions in the two stacks.

Are these stacked? If so, can you show crops of single frames with same focus?

--Rik

[Macro_Cosmos]

Here is an animated illustration for the valve.

My eyes are attracted by the obvious difference in geometry in these two images.

If these are stacked, then I worry that the geometry difference is an artifact introduced by the alignment process making slightly different decisions in the two stacks.

Are these stacked? If so, can you show crops of single frames with same focus?

--Rik

Single frame, zero stacking, same focal point. That slider combines the two rays so the difference could just be a matter of the rays being combined correctly by the prism.

[rjlittlefield]

Single frame, zero stacking, same focal point. That slider combines the two rays so the difference could just be a matter of the rays being combined correctly by the prism.

Fascinating -- I know a little about DIC, but I did not expect that effect in a single image!

--Rik

[abednego1995]

How does the interference fringe look like in the BFP with either slider position?