Afocal through stereo mic eyepiece test.

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apochronaut
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Afocal through stereo mic eyepiece test.

#1 Post by apochronaut » Tue May 22, 2018 10:38 pm

I went looking for an eyepiece, for a member recently and decided to take the opportunity to test a couple for afocal photography with an older stereo, that I do not have a trinocular for. I had been looking for an opportunity to do this, since I have been considering investing in a trino. The eyepiece was pretty dirty and the cleaning didn't get everything, so there are a few chunks of debris showing up. It's an old Olympus FK 5X, mounted on an AO Cycloptic . The pictures are all attached pedicel remnants on fruit, plus one crown on a root vegetable.
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Empire apple
Empire apple
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Greenhouse grown Beefsteak type tomato
Greenhouse grown Beefsteak type tomato
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Navel orange
Navel orange
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Ataulfo mango
Ataulfo mango
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Greenhouse grown English type cuke.
Greenhouse grown English type cuke.
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apochronaut
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Re: Afocal through stereo mic eyepiece test.

#2 Post by apochronaut » Tue May 22, 2018 10:46 pm

5 more.
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Hayward Kiwi
Hayward Kiwi
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Hass avocado
Hass avocado
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Red cherry tomato
Red cherry tomato
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Apricot
Apricot
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Nantes type carrot.
Nantes type carrot.
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desertrat
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Re: Afocal through stereo mic eyepiece test.

#3 Post by desertrat » Tue May 22, 2018 10:57 pm

I think those are pretty decent images for a stereo. I have an old A/O Cycloptic, and your images encourage me to try something similar with mine.
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition

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Re: Afocal through stereo mic eyepiece test.

#4 Post by MichaelG. » Wed May 23, 2018 12:26 am

Those are very encouraging results.

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Re: Afocal through stereo mic eyepiece test.

#5 Post by einman » Wed May 23, 2018 1:04 am

Very Nice.

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Re: Afocal through stereo mic eyepiece test.

#6 Post by Charles » Wed May 23, 2018 11:17 am

Very nice indeed. I never look at food under a scope, because what you see could make it unappetizing.

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Re: Afocal through stereo mic eyepiece test.

#7 Post by apochronaut » Wed May 23, 2018 1:13 pm

The apricot had a mite running around in the stem end.... had been washed too. The apple, which originated here, spent 4 months in controlled atmosphere storage and then 2 more months in cold storage, has an unbelievable amount of dirt in the stem end , which is quite sunken and a virtual trap for airborne debris. It also has some pollen in there. It had been washed too. Oddly, with both eyepieces that cavity looks really deep , like a big open pit with the trunk of a broken off tree emanating from the bottom. When the image is captured with the camera from one eyepiece, it looks reversed, as though the stem is actually raised and sitting on a hill. Probably, more attention to lighting would ameliorate that. I used a very simple, Japanese hobby type microscope lamp, retrofitted with an led bulb that screwed in and was short enough to fit in the metal sleeve housing. The quality is excessively blue and somewhat flat in contrast. You can see the blue reflections from the lamp in some of the more viscous substances and sometimes specular highlights
I would use halogen in future and most certainly some fill lighting.

I'm guessing that the trinocular adapter, would yield an image more truthful to the actual depth of the subject but not necessarily any better in resolution. Probably the fact that the image forming beam would not have to travel through the roof prism, might improve the contrast somewhat too. Those are not BAK 4 prisms but they are roof prisms, so pretty good. However, there also would be optics in the trino, so the net benefit in terms of contrast might not be that noticeable.

Thanks to all. Now, to dig up a trino.

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Re: Afocal through stereo mic eyepiece test.

#8 Post by apochronaut » Wed May 23, 2018 1:30 pm

desertrat wrote:I think those are pretty decent images for a stereo. I have an old A/O Cycloptic, and your images encourage me to try something similar with mine.
Desertrat
I tried using the Cycloptic eyepieces, as well as various versions of 5X I had and a few 4X. With the adapters available to me, I had trouble getting the 10x eyepieces to fill the camera frame with the low power objectives and the low power eyepieces were too long, sticking out of the ocular tubes, placing the eyelens too close to the sensor. The Olympus 5x FK is short, so it sits in the ocular tube in a normal position. I was just barely able to focus with the .7X objective. I'm thinking a lower power eyepiece would even be better: 3.5X or so but it probably would need to be a photo type, due to length considerations. Just some experiences I had, that might help your set up.

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Re: Afocal through stereo mic eyepiece test.

#9 Post by wporter » Fri May 25, 2018 11:14 pm

Below are some test shots of a steel ruler, taken with my AO Cycloptic fitted with the Cycloptic phototube attachment, for the thread followers here who may be interested.

First, though, I decided to clean the optics prior to the test shots, for the first time in the 30 years I've had the scope; the optics inside the head were beginning to get a little filmy.

So, here are some images of the phototube attachment and eyepiece head internals. Cleaning was very easy, using only canned air, bent Q-tips, and Zeiss cleaning solution.

#1: the scope top showing the phototube attachment installed.

#2: a top view of the phototube attachment after the bino heads were removed.

#3: a partial disassembly of the phototube to facilitate cleaning the fixed mirror and the relay lenses.

#4: the camera adapter/mount that I made up to fit over the aluminum phototube riser (see #1).

#5: A view of the top of the scope after the phototube attachment had been removed; one can see the twin lenses that are in the up position & ready to be cleaned. To clean the others in the magnification drum, the drum is just rotated to the other mag settings. The drum is not disassembled; the inside of the lenses were not dirty (AO cautioned users not to disassemble the drum since it's aligned and so forth in the factory, but that's not to say it is not possible if necessary).

#6: the left and right bino head halves.

#7: the right half has been opened up for cleaning.

#8: image taken with the camera mounted on the reassembled scope, 7x mag, no auxiliary objective lens; note the narrower FOV (first mm figure) compared to the visual 10x eyepiece FOV (the larger number); this is from the length of the camera coupler; if a more close-coupled arrangement could be effected, the FOV would have been closer to that of the eyepiece. The aluminum tube phototube riser and the T-adapter arrangement altogether are rather long. Apologies for the imperfect illumination, it was from an LED flashlight moved around freehand to light the subject.

#9-#12: more images at different mags.

#13: I put in a photo eyepiece inside the riser tube to see what the image would be like, even though the relay lenses of the phototube attachment obviously comprise a projection lens themselves. The result was bad, much pincushion distortion & chromatic aberration.
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Re: Afocal through stereo mic eyepiece test.

#10 Post by wporter » Fri May 25, 2018 11:16 pm

More of the images:
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Re: Afocal through stereo mic eyepiece test.

#11 Post by wporter » Fri May 25, 2018 11:21 pm

Last images:
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Re: Afocal through stereo mic eyepiece test.

#12 Post by wporter » Fri May 25, 2018 11:34 pm

I noticed the focus quality isn't the best; my fault: the scope does not have a fine-focus; I focused peering at the lcd screen on the back of the camera, not the best way (i.e., the view was not relayed to my large monitor); the steel ruler was very reflective, getting the illumination w/o glare spots, while trying to focus, was very difficult. A couple of extra hands would have been helpful, lol.

Some caveats for those looking for an old AO phototube: the camera and the eyepiece view are not parfocal. In fact, sometimes I had to raise the subject up a couple of inches due to lack of travel in the focusing rack of the scope. I consider this only a minor inconvenience, however.

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Re: Afocal through stereo mic eyepiece test.

#13 Post by MichaelG. » Sat May 26, 2018 7:19 pm

#10 and #11 both look superb from here.

Thanks for sharing the details.

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apochronaut
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Re: Afocal through stereo mic eyepiece test.

#14 Post by apochronaut » Sun May 27, 2018 2:46 pm

wporter wrote:I noticed the focus quality isn't the best; my fault: the scope does not have a fine-focus; I focused peering at the lcd screen on the back of the camera, not the best way (i.e., the view was not relayed to my large monitor); the steel ruler was very reflective, getting the illumination w/o glare spots, while trying to focus, was very difficult. A couple of extra hands would have been helpful, lol.

Some caveats for those looking for an old AO phototube: the camera and the eyepiece view are not parfocal. In fact, sometimes I had to raise the subject up a couple of inches due to lack of travel in the focusing rack of the scope. I consider this only a minor inconvenience, however.
Thanks for all that info , Bill. So, the captured field with the photo tube is about 50% linear of the actual field, when used without a relay lens?

The other question I have , related to pictures 8,9 and 13, is what do you think the cause of the chromatic aberration , over to the left side of those images is caused by? It seems to be associated with an area of glare in each case but glare in itself, should not elicit that kind of optical effect.

It doesn't seem to be in all the images and inconsistent with the usual image quality through one of those.

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Re: Afocal through stereo mic eyepiece test.

#15 Post by wporter » Sun May 27, 2018 5:27 pm

Phil:
No, the FOVs are the same. That is, if you put a 10x eyepiece in the riser of the phototube, and flip the mirror to direct the light there (from the left bino half), the view through the phototube eyepiece will be parfocal with, and exactly the same as, the view through the 10x eyepiece in the right bino half. Sorry, I should have made this clear.

The images just reflect what shows up in my camera's viewfinder & sensor screen. This would be a function of the size of the sensor (Micro 4/3) and the distance it is from the last relay lens in the phototube attachment. So, basically the camera is just capturing the center portion of the real available microscope FOV.

I don't see any CA, except for that yellowish tinge in the #13. The colors in 8 & 9 are oil stains on the ruler and dispersion from the scratches on the ruler, and the changes in this and in the light quality from different angles of reflection. No CA was visually apparent, either through the bino eyepiece or through one placed in the phototube riser. No fringe coloring at the eyepiece field-edge, even. As far as CA goes, this is one of the best stereomicroscopes I have used, though I don't have the experience of a wide variety of more modern stereo scopes that some in this forum have. (I should have used a different ruler, I guess!)

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Re: Afocal through stereo mic eyepiece test.

#16 Post by PeteM » Sun May 27, 2018 7:00 pm

wporter wrote: . . . Some caveats for those looking for an old AO phototube: the camera and the eyepiece view are not parfocal. In fact, sometimes I had to raise the subject up a couple of inches due to lack of travel in the focusing rack of the scope. I consider this only a minor inconvenience, however.
Bill, do you know if the camera and eyepieces could be made parfocal, simply by shortening the trinocular tube and adapter length? I have one of these scopes but haven't gotten around to making a camera adapter for it.

I'm right now in the midst of making photo tubes for a dozen+ microscopes used in a kids' program and eventually want to equip the Cycloptic with an HDMI camera (likely C-mount). I can make the tube most any length (and will eventually try to figure that) -- but if there is some reason that the existing path is already too long for parfocal imaging, would be good to know.

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Re: Afocal through stereo mic eyepiece test.

#17 Post by wporter » Sun May 27, 2018 8:04 pm

PeteM:

Yes, it can be made parfocal. If I unscrew the phototube riser tube, and get my camera's ccd sensor about an inch away from the exposed phototube lens, it's all parfocal then. If you had a camera small enough in width to where it would not run into the left bino half, it could be made to work.


Phil:

I'll post another image of some sort, in the next day or so, to better illustrate the (lack of) CA. Got any subjects in mind?

(The steel ruler I used is basically a reflective diffraction grating, also having different glare tints depending on the angle of the LED flashlight.)

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Re: Afocal through stereo mic eyepiece test.

#18 Post by PeteM » Sun May 27, 2018 8:29 pm

Thanks, Bill. Looks like a small HDMI camera might work.

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Re: Afocal through stereo mic eyepiece test.

#19 Post by apochronaut » Sun May 27, 2018 9:59 pm

wporter wrote:Phil:
No, the FOVs are the same. That is, if you put a 10x eyepiece in the riser of the phototube, and flip the mirror to direct the light there (from the left bino half), the view through the phototube eyepiece will be parfocal with, and exactly the same as, the view through the 10x eyepiece in the right bino half. Sorry, I should have made this clear.

The images just reflect what shows up in my camera's viewfinder & sensor screen. This would be a function of the size of the sensor (Micro 4/3) and the distance it is from the last relay lens in the phototube attachment. So, basically the camera is just capturing the center portion of the real available microscope FOV.

I don't see any CA, except for that yellowish tinge in the #13. The colors in 8 & 9 are oil stains on the ruler and dispersion from the scratches on the ruler, and the changes in this and in the light quality from different angles of reflection. No CA was visually apparent, either through the bino eyepiece or through one placed in the phototube riser. No fringe coloring at the eyepiece field-edge, even. As far as CA goes, this is one of the best stereomicroscopes I have used, though I don't have the experience of a wide variety of more modern stereo scopes that some in this forum have. (I should have used a different ruler, I guess!)
For sure they are very clean stereo mics. They did a lot of things right. Roof prisms, apochromat primary objectives. I'm pretty high on them right now, especially when you consider the extreme cost of the few competitive microscopes. The colour banding I am referring to is worst in 13. less so in 8 and only slightly in 9. In all cases it is in the upper left , where the focus is a little off. There is a pronounced blue banding on the left of the graduations ( peaks between the 3 4/16 and 6/16 mark) and yellow on the right. In picture 8 it is reversed surrounding the 3 left graduations, yellow on the left and blue on the right. What is the cause of that? It doesn't seem to be there with 1.5X, 2 and 2.5X objectives, only the .7X and 1.0X objectives and very pronounced with the 3.3X NFK eyepiece. Note that in the eyepiece tube pictures I took, I used an Olympus FK eyepiece and it elicited zero optical artifacts. NFK and FK eyepieces are very different beasts and have different optical corrections.

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Re: Afocal through stereo mic eyepiece test.

#20 Post by wporter » Sun May 27, 2018 11:56 pm

Hi Phil,

You're absolutely correct, there is some CA there. DIsregarding the setup with the NFK 3.3x (a weird setup if there ever was one), there is some very noticeable yellow and blue edging especially in #8. So much for me trying to pass it off as bad lighting (oh, well, I tried...)!

I just did some more checks & exposures trying to determine if it was an out-of-focus effect or due to off-axis (edge-of-field) aberrations; looks like off-axis, so far.

I will post some more pix of this later, and also some comparing the phototube attachment to afocal shots. We might be surprised, so don't anyone run out and buy one of these phototube attachments until the jury's out.

It is notable (for visual use of the scope) that the fringe coloring is insignificant when looking through the eyepiece. I've noticed the same phenomenon with my Univar, but put that down to all of the extra lenses in the optics train on the way to the camera (and the fact that the camera is mounted where the big ground-glass projection screen would normally go); the same thing may be at work here: throw in a couple of extra lenses and a couple of mirrors, and the aberrations get added or maybe even multiplied.

It probably comes down to, since many of these microscope camera add-ons were made for black-and-white film, low-end 35mm cameras, and Polaroid and 4x5 film backs, that the expectations were not that great, so they just did the best they could for the money. What's a little CA in a black and white image? Nada! If you look at a research journal from 50-60 years ago, a lot of the images are atrocious compared to what we see today. We're definitely spoiled. Every image has to have crisp, neon-like subjects, and the fantastic images some on this forum have taken aren't helping matters, lol.

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Re: Afocal through stereo mic eyepiece test.

#21 Post by apochronaut » Mon May 28, 2018 10:23 am

The thing is, that it is inconsistent between magnifications and limited to a specific area of the frame. . It looks to me like there is a bit of de-lamination or a component is loose, something of that nature. One of the Cycloptics I have , had a loose collector lens in the bottom of the prism housing. Every so often the image on one side would be slightly out of focus towards one edge and seemed slightly tipped. I had just cleaned it with swabs and had pushed it loose. I couldn't see any chroma but I also never took pictures. The camera will show it, when the eye can't see it. In your case it must be between the main objective triplet and the camera.

I can't see that it is a design flaw. The bulk of the imaging is first rate. Since it is most noticeable with the .7X and 1X objectives , it must be something that lies outside the optical path of the objective sets, when they are reversed.

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Re: Afocal through stereo mic eyepiece test.

#22 Post by wporter » Thu Jun 14, 2018 12:47 am

I fabricated a decent camera mount for my Cycloptic phototube accessory. The new one makes the camera body parfocal with the view through the eyepiece. There was barely enough room to effect this, but it works well. Much more convenient. See photo #1.

I also used that opportunity to check the scope for loose lenses, etc, per Apo's input, to see if that was the source of any of the chromatic aberration (CA) seen in my images of the steel ruler. I didn't find anything wrong, so the next step was to take some test images. CA is best seen at the borders of black objects against a white background, so I drew up a grid and had it printed out by laser printer at 300dpi on card-stock. The test pattern doesn't look that great close-up, but was cheap and worked pretty well. See photo #2 (it's sideways).

The test exposures were done by laying the pattern card-stock on the scope stage, held flat by a circular ring. Three shots were taken at each magnification, center-field in focus, halfway out to the edge of the field in focus, and extreme edge of the field in focus (the 'field' is the field visible in the camera viewfinder); so all that was moved between the three shots was the focus knob. The horizontal axis labels are C for center-of-field, M for 50% of the way from center to edge, and E for the field edge. The vertical axis labels are the microscope dial magnifications.

The results are in image #3. The large CA at the edge of the field at 7x and 10x, and a bit at 15x, is notable. Assuming nothing is wrong with the scope, this is perhaps expected, since the edges of the field-of-view (FOV) at 7x (for instance) are very much more off-axis (from the optical axis of the main objective) than the field edges at 25x (and many aberrations get progressively worse away from the axis, and are probably the biggest reason camera lenses these days use ED glass, aspheric grinds, etc.)

The image isn't the best; a lot was lost in resizing, cropping, scaling the stripes, etc., but the main goal was to look at the CA. The bars (the lines of the grid pattern) are about 120 microns wide, and the specks barely visible (and enlarged due to imperfect focus and processing) are the dots of the laser printer toner which are about 5-8 microns in diameter.

A better image of what the grid looks like at 25x is image #4.

The CA was virtually invisible at the higher mags, through the eyepiece; even at 7x at the field edge, you could tell something was there, but it was hard to put your finger on exactly what (or, I could just be getting old...)

It does seem to be true that digital cameras can record and 'exaggerate' chromatic fringes compared to what we see with the naked eye; which only makes sense, since our brains must filter out a lot of CA because our eyes are hardly apochromatic.
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Re: Afocal through stereo mic eyepiece test.

#23 Post by apochronaut » Thu Jun 14, 2018 3:24 pm

That seems a very accurate test. Interesting results.
There are 2 reversible intermediate objectives in the magnification changer and one open port for the 15X/20X/25X/40X or 1.5X magnification setting, so in the latter case, maintaining the integrity and bumping the magnification by .5X of the 1X apochromatic objective's image when viewed through the eyepieces, is being shouldered by the collecting lens in the prism housing and the corrective tube lens in advance of the eyepieces, plus the eyepieces themselves : 5 lenses minimum( depending on the design of the specific eyepiece), with several of them being achromatic doublets. Those lenses also must provide the proper corrections for the 2 reversible objectives as well. Since those lenses are not part of the optics when the trinocular tube is being used, there would need to be some corrective capacity in the trinocular unit itself, since that 1.5X setting is relatively clean. Perhaps there is a small amount of ca introduced by the optics in the trino. , which affects the low power optics of the reversible objectives more than the others? It doesn't seem to show as much through the eyepieces, whether visually or photographically with the Olympus photo eyepiece. For the higher magnification settings, 2X and 2.5X, which are the reverse settings of the 1X and .7X respectively, there must some further corrections introduced in the intermediate objectives as well, which are fairly sophisticated and fully designed to maintain the integrity of the apochromatic main objective's image. . In use with the trino port, none of the magnification changer settings have the advantage afforded by any further corrections provided by the visual optics, so it seems that a small tradeoff was necessary to yield a very clean 2X and 2.5X objective image , with a small amount of ca stemming from the same lens packs when reversed to the .7X or the 1X setting.

In photographing through the Olympus photo eyepiece, using the visual head, there didn't seem to be much in the way of difference between the ca of the various magnification settings, just some small difference in curvature of field.

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