MicrobeHunter.com Microscopy Forum

Yeah, I figured it out in the previous post, including for the case in which L is infinite. The key was to recognize that increasing L results in a decrease in the angle of attack of light at the tube-lens periphery, hence causing the image circle to shrink. If L is infinity, the divergence of the p...

OK, I figured it out. When L is made larger to the point that vignetting starts to happen, the parallel bundles that still do strike the edge of the tube-lens come in at a shallower angle . This means that the tube lens bends the resulting point of light not straight out parallel to the optics, but ...

Doesn't increasing L create a larger image at the tube lens as well as at the sensor plane? No, it does not. Peripheral light is lost but the magnification does not change. If we look at the geometry of the figure on the tube-lens calculation page, we see that light from a given single point of the...

No, the image size does not change. Well, why then? Doesn't increasing L create a larger image at the tube lens as well as at the sensor plane? Otherwise, vignetting at the tube lens would not occur when L is very large, right? That's the sense in which I mean "magnification." (Not "zooming in" to ...

L is not a "required" distance, just the longest that can be used without vignetting. With a smaller sensor the angular deviation of the rays in the infinity space that hit the corner of the sensor is proportionally smaller, therefore the tube lens can be moved further away before useful ray start ...

OK, I'm confused about the results of that calculator. It and the formulas (the results match) are showing that a small sensor requires a long objective to tube-lens distance ("L") and a large sensor requires a small one. This feels backwards to me. To provide the magnification required to fill a la...

Yes, I found that link and other discussions while surfing around too. This one in particular presents math to determine the maximum length before vignetting occurs: https://www.edmundoptics.com/knowledge-center/application-notes/microscopy/using-tube-lenses-with-infinity-corrected-objectives/ To an...

(Not arguing, just trying to figure it out:) Would increasing the distance necessarily shrink the image circle? If the light is truly "infinite", i.e. completely parallel, then the distance should not matter. Of course, the objective's optics are probably not perfect, and hence not actually complete...

Hello All,

For infinity optics, is the distance between the objective and the tube lens substantially irrelevant (within reason, other than leaving room for any other optical components), or what other factors are in play?

Thank you.

Hello All, Children born of the Apollo space age with an inclination towards science, as I was, all wanted a microscope, a telescope and a chemistry set. My microscope was by Lafeyette Radio Electronics. It was a lower-end model, in black-painted cast iron, with four objectives and no fine focus kno...

Can anyone provide a clear mathematical argument showing that the resolution of a simple condenser plus objective scenario (with no subject to confound matters) is not strictly limited to Min(NAcd, NAobj)? Until then, the confounding factor causing all the debate is the object being imaged. That can...

… Is there still more to it than this? I think the “more to it” is probably Modulation Transfer Function MichaelG. MTF is a way to characterize lens performance as seen in the image plane vs. distance off-axis from the center. I.e., the corners of a photo are generally less sharp and more distorted...

Figure's 58 and 59 in the volume cited above illustrates why a glass-air interface strictly limits the NA to a theoretical maximum of 1, and how oil (with approximately the same index of refraction as glass) allows up to about NA=1.5: https://archive.org/details/microscope02beckuoft/page/70/mode/2up...

The common equation for resolution of a condenser+objective combination, as seen in the Thor Labs link, is highly idealized, containing only 3 variables (wavelength and the NA's), and hence seems more like a simple rule-of-thumb than one that can deal with real-life complexities (such as the subject...

Oil is commonly used with microscopes at optical interfaces because its refractive index (RI) is higher than air (~1.5 vs. ~1). This allows light to be bent at a sharper angle than at glass-air interfaces (otherwise the rest of the light would be reflected internally). The sharper angle allows a bro...

Adding in the characteristics of a subject confounds the situation beyond the usual equations and into the realm of ruminations, but sure. Anyway, I'd suggest that the improvement some people find when using very expensive elite-quality objectives in the discussed situation has more to do with them ...

Thinking about the last point I made a bit more: Yes, provided that the sample radiates light broadly enough to fill the acceptance cone of the objective, some improved resolution can be obtained. But of course many or most biological samples requiring high magnification are nearly entirely transpar...

The result of those equations is the minimum distance between two points before they can be individually resolved - the "resolution." So if the NAcd is less than NAobj, then from the second equation the result is a greater distance (a worse resolution) than if the condenser's NA matched that of the ...

A dry (air-gapped) condenser will strictly limit the effective NA of any subsequent objective to a theoretical maximum of 1 (meaning somewhat less than 1 in practical terms). I've heard "an average of the condenser and the objective's NA" here more than once, but that's nonsense. The net, in fact, c...

On forums such as this, it's common to extol the (frequently genuine) benefits of buying used, but there are some benefits to buying new too. I have a Zeiss 508, bought new along with their Apo 0.63x auxiliary lens, stand and LED illumination. The optical quality is magnificent! Zero regrets. Anyway...

Thank you. The originals are reputed to be extremely difficult to use. One person commented that using one (an accurate replica) seemed almost impossible. In this, the eye relief is about 3mm. That's very close, but after a few seconds you figure out how to hold it comfortably. The flat body around ...

Hello forum members, I made a Leeuwenhoek homage microscope, and thought some of you might be interested. My goal was not to create a strict replica. Instead, it's an interpretation of one with a few modern twists. I did want it to remain recognizable - to those in the know - as descended from his c...

A little follow-up: I nicked myself shaving this morning, so I put a tiny smear of blood on my little 10mm "slide." At ~55x, yes, I could see blood cells as pale, basically featureless dots. I'm not sure anyone would guess what it was without a prompt, but I'll leave that slide as-is for now. Thanks...

Southern California is very dry, which really cuts down on them. I wouldn't call it paradise, but it's a big bonus. That tiny whine immediately launches a DefCon-5 seek-and-destroy mission, with no possibility of sleep until it's terminated. Yes, I agree an insect wing would be a very good subject! ...

Thanks, the "seed parachute" idea seems quite interesting. I'll scan the area around my home for possibilities. There are very few mosquitos where I live, thankfully, but I'll look around my residence for a dead spider or something like that. My "slide" is actually a 10mm optical window of borosilic...

Thanks. Important point that bears repeating: The view will be at 50X total magnification only. No possibility of any other magnification. Also, no possibility of using a cover slip or to scan the surface for something interesting. For testing purposes, I am currently using a streak of dry marker on...

Dear forum members, I need suggestions for one or two interesting and pretty subjects to view, and advice about mounting them. * Needs to be a dry subject that won't decay. * Should be a broad or continuous subject that doesn't need to be searched for. * Should be thin and transparent enough for goo...

Evidently, I'm forced to give up on "Evident," since I'm just being ghosted now. I'm also ghosted by two used-scope dealers that I've contacted. One asked what my budget was, and I responded with a more-than-adequate 5-figure sum. But apparently not adequate enough to bother hitting "respond." Such ...

Thanks for the feedback. Your suggestion for an inverted stand is particularly thought-provoking. I think I've felt reticent about that due to the greater possibility of damage to the objectives, etc. But maybe it's worth the risk. Future compatibility for DIC can be a problem in that many systems s...

Oh dear, those sharks, Bain Capital!? A grim prediction: A hollowing out for quick, short term profits will likely ensue, leaving behind little more than a zombie corpse. Reminds me a little of H.P. spinning off their famed instrument division (so they could focus on ... Compaq!? How did that work o...