Weak polarizing effect
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Weak polarizing effect
I started playing with polarizing filters on my microscope, but I'm getting very weak effect. What I'm doing wrong ?
For the retarder I'm using a cellophane - can it be crinkled or it should be perfectly flat/smooth ? Distances ? Thicknesses? Placement ? Polarizing filters (I think) are OK - at the right angle they are killing the light. Something else ? I'm using Mitutoyo objectives, AO and Nikon condensers.
For the retarder I'm using a cellophane - can it be crinkled or it should be perfectly flat/smooth ? Distances ? Thicknesses? Placement ? Polarizing filters (I think) are OK - at the right angle they are killing the light. Something else ? I'm using Mitutoyo objectives, AO and Nikon condensers.
With the same setup without compensators, does the field become dark when the pols are crossed?
If so, the issue is with your compensators. In principle they are to be used with the filters fully crossed (although later you can play with other configurations)
Cellophane can be OK, although maybe not all of them are equally adequate. Cello tape glued on a glass slide also works well, you can play with different thicknesses adding more layers
If so, the issue is with your compensators. In principle they are to be used with the filters fully crossed (although later you can play with other configurations)
In principle flat is the best, distance does not matter, they just need to be placed between both polarizers, of course if not of the highest quality is better to put them over the polarizer before the objective to avoid image degradation.For the retarder I'm using a cellophane - can it be crinkled or it should be perfectly flat/smooth ? Distances ? Thicknesses? Placement ?
Cellophane can be OK, although maybe not all of them are equally adequate. Cello tape glued on a glass slide also works well, you can play with different thicknesses adding more layers
Pau
Hi Pau, thank you for your quick reply !
Yes, field become darkWith the same setup without compensators, does the field become dark when the pols are crossed?
On the back side of the slide ? I tried to place between slide & condenser (but it was crinkled), nothing ...Cello tape glued on a glass slide also works well...
Interesting, I thought, that with the thinner cellophane effect will be stronger...you can play with different thicknesses adding more layers
No, I was referring to a blank slide. The ability to rotate the compensator is very important. Usually the stronger effect is produced when the plate optical direction is at 45 deg. of the polarizers.Saul wrote:On the back side of the slide ? I tried to place between slide & condenser (but it was crinkled), nothing ...Cello tape glued on a glass slide also works well...
If you use it like in a typical microscope the usual place will be between the polarizer and the condenser
If I recall well one layer of tape is like a 1/4 plate, two layers like a 1/2 plate and so, of course not well calibrated..it depends of its thickness and of the traction strength applied when gluing itInteresting, I thought, that with the thinner cellophane effect will be stronger...you can play with different thicknesses adding more layers
Pau
Saul,
I had good results with the clear cellophane from this package:
https://www.amazon.com/Hygloss-78548-Sh ... _in_o0_img
One sheet is 1/4 plate. I can try to find mine and send them your way, if I can find them (I just moved my house and have not been able to find everything from boxes).
I placed cellophane between two microscope slides (to hold them flat) and taped on the glass slides, instead of cellophane. I placed the DIY retarder in between condenser (bottom lens) and bottom polarizer (which is in turn placed on field iris of Optiphot). You have to rotate retarder to get best effects.
I had good results with the clear cellophane from this package:
https://www.amazon.com/Hygloss-78548-Sh ... _in_o0_img
One sheet is 1/4 plate. I can try to find mine and send them your way, if I can find them (I just moved my house and have not been able to find everything from boxes).
I placed cellophane between two microscope slides (to hold them flat) and taped on the glass slides, instead of cellophane. I placed the DIY retarder in between condenser (bottom lens) and bottom polarizer (which is in turn placed on field iris of Optiphot). You have to rotate retarder to get best effects.
Thanks Fan ! Don't go through you boxes yet
Before your message I tried one thing, using old aperture mount O-ring from the DIY AO-Nikon condenser, window sealing heat shrink film, double-stick tape and wife's hairdryer:
Initial quick test shows some signs of life (need to prepare a better slide).
I can rotate ~60 degrees, I hope it will be enough ...
Before your message I tried one thing, using old aperture mount O-ring from the DIY AO-Nikon condenser, window sealing heat shrink film, double-stick tape and wife's hairdryer:
Initial quick test shows some signs of life (need to prepare a better slide).
I can rotate ~60 degrees, I hope it will be enough ...
Do you have the same issue with different condensers?
Possible causes
1. Condenser is dirty (easy to see!)
2. condenser lenses have strain and alter the polarization of light. There are pol condensers meant to work with pol, although I've got good results even with cheap no name condensers.
You can try to put the polarizer over the condenser if you have enough room, optically it must work
What polarizer do you use?
An easy mistake is putting a circular pol with the plate wave facing the condenser, if they are camera filters they must be placed with the front side facing the condenser
Possible causes
1. Condenser is dirty (easy to see!)
2. condenser lenses have strain and alter the polarization of light. There are pol condensers meant to work with pol, although I've got good results even with cheap no name condensers.
You can try to put the polarizer over the condenser if you have enough room, optically it must work
What polarizer do you use?
An easy mistake is putting a circular pol with the plate wave facing the condenser, if they are camera filters they must be placed with the front side facing the condenser
Pau
Tried with the Nikon & AO only. Will try with Amscope & Quodmaster (this one has a rotatable filter changer, one of them (looks like, have to check) is pol, so should be ok option (only problem - to adapt to the Optiphot)Pau wrote:Do you have the same issue with different condensers?
Have a small pol, will try. But will be a problem with the retarder ...You can try to put the polarizer over the condenser if you have enough room, optically it must work
Yes. Field becomes dark when the pols are crossed. Bottom - circular pol, behind the objective - linearWhat polarizer do you use?
An easy mistake is putting a circular pol with the plate wave facing the condenser, if they are camera filters they must be placed with the front side facing the condenser
I have played with a type of tape which was found to be very good; the type which is completely transparent even when on the roll. Try
" AIEX Clear Sticky Tape Ultra Transparent Adhesive Tape ". About 300nm per layer.
Using a screen as a pol source and a handy analyser we made national flags by building up the colours with the retarder tape.
" AIEX Clear Sticky Tape Ultra Transparent Adhesive Tape ". About 300nm per layer.
Using a screen as a pol source and a handy analyser we made national flags by building up the colours with the retarder tape.
Chris R
The learning curve (for me) - not every cellophane is the same , not every objective is the same for cross-pol ... and not for the every specimen. Lot of variations.
Picture (quick test stack) with the same AO condenser, different retarder and (lost my patience keeping pol filter and falling patches of the cellophane from the illuminator) assembly, to keep and adjust polarizer/retarder on the Optiphot illuminator. Now I can rotate each one separately and everything together .
Assembled:
Picture (quick test stack) with the same AO condenser, different retarder and (lost my patience keeping pol filter and falling patches of the cellophane from the illuminator) assembly, to keep and adjust polarizer/retarder on the Optiphot illuminator. Now I can rotate each one separately and everything together .
Assembled:
Last edited by Saul on Mon Jan 07, 2019 10:31 am, edited 1 time in total.