How useful are objectives with corrective collars?
How useful are objectives with corrective collars?
I see some Apo objectives with correction collars to correct of different cover slip thicknesses (0.11 - 0.23). How useful are these if you always use #1 coverslips with a 0.15-0.17 range? Are there any other uses for this correction?
Bill Tschumy
Leitz SM-D LUX
AO Spencer "Cycloptic" Stereo Microscope (Series 56C)
Leitz SM-D LUX
AO Spencer "Cycloptic" Stereo Microscope (Series 56C)
Re: How useful are objectives with corrective collars?
A cover slip thickness range of 0.15-0.17 is quite large.
Have a look at the links in the first post on this thread: viewtopic.php?f=5&t=2513&hilit
A micrometer with a range of 0.002 mm is a useful tool.
Have a look at the links in the first post on this thread: viewtopic.php?f=5&t=2513&hilit
A micrometer with a range of 0.002 mm is a useful tool.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)
Olympus E-P2 (Micro Four Thirds Camera)
Re: How useful are objectives with corrective collars?
For high NA dry objective coverslip thickness is very important, and even slight deviation from the expectation lead to surprisingly huge performance degradation. For example, just 0.02 mm deviation for NA 0.95 objective leads to 71% performance reduction (Table 1 at https://www.microscopyu.com/microscopy- ... correction).btschumy wrote:I see some Apo objectives with correction collars to correct of different cover slip thicknesses (0.11 - 0.23). How useful are these if you always use #1 coverslips with a 0.15-0.17 range? Are there any other uses for this correction?
So this correction collar is useful and maybe even necessary for high NA dry objectives even if you always use #1 coverslips (and you can also use the collar to correct for the sample depth). On the other hand, it's one more variable that needs to be adjusted.
Re: How useful are objectives with corrective collars?
I'm surprised to hear you think that is large. I think #1 coverslips are allowed to be between 0.13 and 0.16 mm and #1.5 are 0.16 to 0.19 mm. Seems like every batch of coverslips I see has some variation. Just in case you misunderstood me, the variation is between cover slips not within a given one.A cover slip thickness range of 0.15-0.17 is quite large.
Maybe I'm just buying crappy cover slips.
I do have a micrometer that measure to 0.01 accuracy which seems enough for this application.
Bill Tschumy
Leitz SM-D LUX
AO Spencer "Cycloptic" Stereo Microscope (Series 56C)
Leitz SM-D LUX
AO Spencer "Cycloptic" Stereo Microscope (Series 56C)
Re: How useful are objectives with corrective collars?
Very expensive coverslips are held to closer tolerances. However many professionals and hobbyists alike use a micrometer to separate their coverslips for exacting microscopy.
Re: How useful are objectives with corrective collars?
I suppose you could think of the bottom of a petri dish as being a coverslip. I have long working distance objectives with collars on my inverted scope. Here's looking up atcha!
Dale
Dale
B&L Stereozoom 4. Nikon E600. AO Biostar 1820.
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Re: How useful are objectives with corrective collars?
.02 or 3 ,on the coverslip isn't going to make much of a difference, especially with a water medium, where the thickness of the water is the most important factor. The collar only factors in when the sample is precise and absolute precision imaging is demanded. With the objectives I own, that have correction collars, I find that I do a light trim, while looking through the eyepieces and the effect is usually very slight, if any, with well prepared water based mounts and I usually choose a thinner, rather than thicker coverslip.
Also, not all objectives are created equal. I have examples here, of dry apos , fluorites and high N.A. achromats of 40x .70, 40x .80, 43x .85, 45x .85, 50x .85, 60x .80, 63x .85, 80x .90 and 80x .95 , none of which have correction collars and all of which produce excellent imaging over a range of sample thicknesses. These objectives, have clearly been designed to limit the longitudinal spherical aberration near the front of the objective , which is the major reason for a correction collar.
I even have one 50 .85 oil objective, that produces as good an image unoiled as most dry 40 .65 do, so spherical aberration is not always as predictable as just looking at the N.A. and knowing it will be evident or less so, based on the number. Each objective needs to be evaluated, in order to get an idea of it's preferences and how it will handle various mounting conditions.
Also, not all objectives are created equal. I have examples here, of dry apos , fluorites and high N.A. achromats of 40x .70, 40x .80, 43x .85, 45x .85, 50x .85, 60x .80, 63x .85, 80x .90 and 80x .95 , none of which have correction collars and all of which produce excellent imaging over a range of sample thicknesses. These objectives, have clearly been designed to limit the longitudinal spherical aberration near the front of the objective , which is the major reason for a correction collar.
I even have one 50 .85 oil objective, that produces as good an image unoiled as most dry 40 .65 do, so spherical aberration is not always as predictable as just looking at the N.A. and knowing it will be evident or less so, based on the number. Each objective needs to be evaluated, in order to get an idea of it's preferences and how it will handle various mounting conditions.
Re: How useful are objectives with corrective collars?
Apo, when viewing through the bottom of a flask with an inverted scope, that is when
longitudinal spherical abberation would benefit from the collars correction?
Dale.
longitudinal spherical abberation would benefit from the collars correction?
Dale.
B&L Stereozoom 4. Nikon E600. AO Biostar 1820.
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Re: How useful are objectives with corrective collars?
that is a bit of a different scenario because petri dishes and the like are usually very irregular and thick, unless you invest in expensive dishes with precision bottoms, some of which are graded coverslip thicknesses. Your microscope objectives had to be designed to accomodate a great range of possibilities, mm differences over a long w.d. in your case, the glass is a disproportionate percentage of the total sample thickness.
Re: How useful are objectives with corrective collars?
The petri dishes were ok til I added the mechanical stage, now I want to fabricate rectangular
slides with sides. Like a big well slide. I can't free hand a petri dish on high power.
Dale
slides with sides. Like a big well slide. I can't free hand a petri dish on high power.
Dale
B&L Stereozoom 4. Nikon E600. AO Biostar 1820.
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Re: How useful are objectives with corrective collars?
kind of like a little mini-aquarium with a good quality slide of known thickness for a bottom?
Re: How useful are objectives with corrective collars?
Exactly.
B&L Stereozoom 4. Nikon E600. AO Biostar 1820.
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Re: How useful are objectives with corrective collars?
That's a great project. If I was doing it, since the slide, is in effect your cover slip, I would invest in a couple of very high quality precision slides with which to make these. I would go for the lower range of your correction scale. LImiting the amount of glass you have to see through, can only be good with dry objectives.