Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

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hans
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#91 Post by hans » Wed Aug 12, 2020 10:12 pm

MichaelG. wrote:
Wed Aug 12, 2020 9:32 pm
I find this patent quite difficult to follow [even for a patent], because it describes more than one ‘implementation’ ... without clear boundaries. The text sometimes seems like a ‘stream of consciousness’.
To add to the confusion, I just noticed, there appears to be a typo in table 1. I believe the halves of the splitter shoud labeled be IV' (right) and IV'' (left) which would be consistent with the convention everywhere else in the patent of single-primed labels in the right eye path and double-primed labels in the left eye path.
MichaelG. wrote:
Wed Aug 12, 2020 9:32 pm
I think, however, that the answer lies with the Prism IV and Mirrors V [see Figure.1 and the values in Table.I]
Assuming I am correct about the typo, the way I am interpreting that is, 24 mm path length through VI' (12 mm before and 12 mm after reflection) going to the right eye and 12 mm path length through VI'' (after passing straight through the half-silvered interface) going to the left eye. I believe the path length through VI' going to the left eye is unspecified, but presumed to be 12 mm. In person I can see that the splitter is very close to square with the 45 deg interface intersecting almost exactly at the corners.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#92 Post by Zuul » Mon Aug 17, 2020 4:21 am

Here’s how I chose to incorporate the CA correcting element. I trimmed the length, and mounted it in a circular plate. That plate was sized to sandwich securely between the segments of an old Nikon K extension tube. Now it can be assembled into the stack anywhere between the t-mount adapter and the camera. A short helicoid and wide assortment of sturdy threaded extension tubes makes for a very flexible arrangement.
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#93 Post by MichaelG. » Mon Aug 17, 2020 4:52 am

Zuul wrote:
Mon Aug 17, 2020 4:21 am
... makes for a very flexible arrangement.
.
In the good sense of the word, I hope !

Seriously though : That’s very tidy.

MichaelG.
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hans
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#94 Post by hans » Mon Aug 17, 2020 4:59 am

Zuul wrote:
Mon Aug 17, 2020 4:21 am
Here’s how I chose to incorporate the CA correcting element...
Very nice, so the thing with thumb screws is the T-mount adapter and clamps to the dovetail on top of the trinocular head? I still haven't decided what to do with the dovetail. Lacking appropriate machine tools and the skills to use them I was considering just leaving it off and attaching a plate, with matching three-hold pattern and hole drilled to clear the glass plug, on top of which I could employ some cruder means of attachment...

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#95 Post by Zuul » Mon Aug 17, 2020 5:26 pm

hans wrote:
Mon Aug 17, 2020 4:59 am
Very nice, so the thing with thumb screws is the T-mount adapter and clamps to the dovetail on top of the trinocular head? I still haven't decided what to do with the dovetail. Lacking appropriate machine tools and the skills to use them I was considering just leaving it off and attaching a plate, with matching three-hold pattern and hole drilled to clear the glass plug, on top of which I could employ some cruder means of attachment...
Yes, exactly. I like keeping the dovetail in place because it makes rotating the camera relative to the head trivial, and I didn't have to come up with yet another interface to remove the photo tube.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#96 Post by Zuul » Mon Aug 17, 2020 5:47 pm

I turned the collar, and bonded a t-mount (M42 x 0.75) eyepiece adapter into the bore. Threading is beyond my capacity atm.
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#97 Post by hans » Fri Aug 21, 2020 8:42 pm

I found some old "chlorinated" carburetor cleaner in the garage with ingredients: xylene, toluene, methlyene chloride. The doublet has been soaking for a few days now. No sign of loosening yet but I just noticed it looks like a curved internal interface has become visible. Maybe a sign that solvent invading the cement has changed the refractive index enough to get some total reflection?
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#98 Post by PeteM » Fri Aug 21, 2020 10:12 pm

Fascinating thread - thanks for all your work.

One hopes there is a happy ending, with a better corrected optical solution for Microstar IV trinocular heads.

hans
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#99 Post by hans » Sat Aug 22, 2020 4:14 am

Thanks, Pete. I just put in a McMaster order with some pieces of aluminum stock. Hope to have something a bit more rigid and precise to mount the eye tubes and do some more photo tests in a week or two.

wabutter
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#100 Post by wabutter » Tue Aug 25, 2020 11:22 pm

Hans,
Do you have access to the 1762Y 2.8x adapter or the 1763Y 5x adapter from the PhotoStar camera system. These are equipped with a Tmount for the Konica SLR. It might be interesting to engineer a Nikon Tmount in it place. Then your DSLR could be mounted directly to the trinoc with optics that should eliminate the CA.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#101 Post by hans » Wed Aug 26, 2020 1:32 am

wabutter wrote:
Tue Aug 25, 2020 11:22 pm
Do you have access to the 1762Y 2.8x adapter or the 1763Y 5x adapter from the PhotoStar camera system.
I do not, unfortunately. The shutter assemblies and relay lenses appear to be fairly rare and probably worth more than I want to pay. (Compared to the trinocular heads which are inexpensive and readily available.) I had not seen any complete systems for sale since I started looking at 410s early this year until this one was posted a couple weeks ago: https://www.ebay.com/itm/143679469748

I am also hesitant to to buy a relay lens alone, not being sure whether there is anything optically significant in the shutter assembly other than the shutter. I had speculated earlier that "color correcting doublet X" (drawing attached) from the patent might be in the shutter assembly. Someone told me they did not think so (perhaps the function is performs was integrated directly into the relay lenses) but even if not it I think it could theoretically be necessary to replicate the thickness/position of glass windows for optimal performance, since this stuff comes after the telelens?

By mounting the complete eye tube and eyepiece over the camera port I was just hoping to get image quality comparable to photographing through one of the binocular eyepieces while taking advantage of the convenience of the trinocular head, and without waiting a long time or paying a lot of money for the other Photostar components. I have not found high quality example photos taken with a complete Photostar system adapted to a digital camera but would be interested to see some. (Searching academic papers for "reichert photostar" brings up some results but all I saw were low resolution images embedded in PDFs, poor quality scans from film, etc.) It would be reasonable to expect image quality better than afocal through a binocular eyepieces, probably?
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#102 Post by apochronaut » Wed Aug 26, 2020 4:44 pm

I did use a Reichert Photostar camera adapter for a bit but came away a bit disappointed with it. The principal problem I had was that at parfocality it captured too small a frame. Tried out various eyepieces. The 181 briefly and then a 1054 but both were not at parfocality perfectly corrected. They are useful in lieu of having another functional eyepiece to establish a psrfocal distance. I cycled through a few other optics, even 30mm bore Chinese eyepieces that are corrected for a similar system to AO's but settled on the cat. # 145 eyepiece that was used with the more advanced Stereostar optics. When set at parfocal distance, the peripheral ca is very minimal with the planachros and close to non-existent with the planfluors.

Here is the thing about that correcting optic. Way back in this thread I suggested that it was the distance or tube length that needed to be adjusted in order to rid the 181 eyepiece of it's ca. You tested that theory by testing at various projection distances not reference lengths. There seems to be a fixed attitude or maybe theory of design out there in some circles that postulates that the photo lens be close, as though having a short photo tube is somehow better. The photo lens needs to be where it needs to be and any ideology about the length of the photo tube is irrelevant.
It turns out that the correcting optic/optical window adjusts the reference length and thus the peripheral ca of the 181 eyepieces at the reference length of the system. If you measure the distance in the head from the telan lens to the lip of the optical tube you will get something like 230mm or maybe even more. The reference length of the system is theoretically just over 180mm. Those 181 eyepieces are designed to be used at around 230 mm from the telan lens. Why? Here's a guess. If they had used a 180mm reference length, the head would have been tiny. They did the same thing with the series 4 in order to have an adequately sized , ergonomic stand. The tube length of the optics are actually 160mm but the compensating optic allows the head to be extended physically , bringing the actual length to around 200mm.
Whatever the theory, I tend to work with results and the 145 works for me. At the same distance the 181 does too but it doesn't quite as well with the older Austrian objectives, so I am sticking with the cat. # 145 for now.
Placing a # 145 eyepiece at about 325mm + - above the objective shoulder yields minimal ca. , so that is about 230mm above the telan lens. The image circle is the same as the eyepiece view and placing an APS-C sensor about 50mm above the eyepiece matches the maximum possible rectangular portion of the 20mm field to the sensor border. At 230mm the eyepiece is parfocal to the eye but not to the sensor. The focus needs to be raised about 200 microns. I find that I always like to check the focus for detail with the focus magnifier anyway, so I refocus before exposure as a routine. Parfocality isn't that important to me but corrections and field coverage are.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#103 Post by MichaelG. » Wed Aug 26, 2020 4:49 pm

Hans,

In my relentless pursuit of insanity ... I’ve had another look at that patent

Aside from some fairly obvious typos; the three instances of Tables I and II are essentially the same.
What interests me, therefore, is the short note about FIG. 7
[ commencing column 7, line 63 and ending column 8 line 18 ]

... which includes this little gem:
.
... In this embodiment, the glass plug is preferably longer in order to compensate for the difference in optical length ...
.
But nowhere can I find a suggested dimension for this ‘preferably longer’ glass plug.

MichaelG.
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hans
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#104 Post by hans » Wed Aug 26, 2020 8:07 pm

apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
Way back in this thread I suggested that it was the distance or tube length that needed to be adjusted in order to rid the 181 eyepiece of it's ca. You tested that theory by testing at various projection distances not reference lengths.
Correct, I only careful tested projection through the 181 with the objective working distance set as usual by focusing visually through the binocular eyepieces first. I did mess around a bit with reference length during other experimentation but my impression was that moving the objective away from the normal working distance was quickly increasing spherical aberration while having only weak effect on the transverse CA. Once I have a more stable setup constructed I plan to do further experimentation along these lines.
apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
It turns out that the correcting optic/optical window adjusts the reference length and thus the peripheral ca of the 181 eyepieces at the reference length of the system.
I don't think I agree with this conclusion but I am going to refrain from further speculation about the function and design intent until I have done some more experiments.
apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
The reference length of the system is theoretically just over 180mm.
Regarding figure 2 I just posted the patent says: "Distance from the upper surface of Lens II to the camera focal plane is 193.725 millimeters." But it seems like "reference length" is not a precisely defined concept? When you are talking about reference length is that considering the behavior of the telelens pair alone, or is it including the effect of flat glass elements like the prism/splitter in the binocular path and corresponding glass plug in the camera port?

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#105 Post by apochronaut » Wed Aug 26, 2020 9:23 pm

I have used patents a lot to figure out designs and that process is usually very helpfull and often successfull but patents only reveal what the patent office requires in order to secure the patent. Many details are concealed or if not directly related to the nature of the patent , can be changed in actual production

All I am saying is that the cat# 145 eyepiece provides as close to complete correction and field coverage for an APS-C sensor and is visually parfocal with the # 181 eyepieces in the binocular tubes, when it is situated so that the top of it's eyelens is about 230mm from the telan lens. I measured with a 300mm ruler, so it might be 220 or even 210, since the telan lens is about 15mm thick. It doesn't really matter because I adjust it with a helical link. At that point , although visually parfocal with the eyepieces , it does require focusing on the sensor

Here are a few of the last images I took through the system probably about 3 years ago but at that time I had located the 145 eyepiece in a convenient location with the hardware at hand. I have since moved it to the current visually parfocal location and it might be more friendly, there. I haven't made photos through it much lately. There is a tiny amount of ca in these but some of that is being sample generated since these are high N.A. DF and overly thick too because it is a live mould culture. You can tell that from some of the spherical aberration in some of the images. The diagonal coverage is pretty much right across a 20mm field. A couple are cropped some.

viewtopic.php?f=6&t=5026&hilit=wallemia

I'm not putting these forward as the world's best photomicrographs, just that if you are on a quest to find a workable photo optic , you might try one that seems to work.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#106 Post by hans » Wed Aug 26, 2020 11:40 pm

apochronaut wrote:
Wed Aug 26, 2020 9:23 pm
I'm not putting these forward as the world's best photomicrographs, just that if you are on a quest to find a workable photo optic , you might try one that seems to work.
I believe you about the 145 in your setup. (And of course the photos from that thread as well as others of yours I have seen are hard to argue with.) There actually is a reasonable-looking single 145 on eBay right now I had been considering buying. A few reasons I have not tried a 145 yet:
  • You have it on top of a Photostar shutter assembly, correct? In that case there is the same issue I just mentioned to Wayne regarding the possibility of getting a Photostart relay lens separately from the rest of the system -- I am not convinced the shutter assembly is unimportant optically.
  • Relatively high cost of buying components like eyepieces individually. Competent sellers need to cover their per-transaction overhead and I don't think the prices are generally unreasonable, but when the hobby is tinkering with old junk, buying mostly-complete microscopes is much more attractive in terms of junk/dollar.
  • Since I want to come up with a more stable way to mount an eyepiece over the camera port in any case I might as well wait and experiment more with the 181 first.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#107 Post by hans » Thu Aug 27, 2020 12:28 am

MichaelG. wrote:
Wed Aug 26, 2020 4:49 pm
But nowhere can I find a suggested dimension for this ‘preferably longer’ glass plug.
I also did not see any dimensions given for the consolidated glass plug IX as shown in figures 3-5 and 7, but I did measure mine in post #86 above. (It is possible to get calipers directly across the length of the plug with the head fully disassembled so the 58.4 mm measurement should be pretty accurate.)

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#108 Post by hans » Thu Aug 27, 2020 4:56 am

Sorry, I know I just said I was going to refrain from further speculation until I did a few more experiments, but I am still clinging to this theory that color correcting doublet ("CCD") X or something similar could be in the Photostar shutter assembly. I think it would explain our very different observations regarding reference length:
apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
Here is the thing about that correcting optic. Way back in this thread I suggested that it was the distance or tube length that needed to be adjusted in order to rid the 181 eyepiece of it's ca. You tested that theory by testing at various projection distances not reference lengths. There seems to be a fixed attitude or maybe theory of design out there in some circles that postulates that the photo lens be close, as though having a short photo tube is somehow better. The photo lens needs to be where it needs to be and any ideology about the length of the photo tube is irrelevant.
As I mentioned, by far the most obvious effect I noticed changing reference length was spherical aberration. In all cases that was either without the CCD or moving the CCD together with the eyepiece while maintaining the normal ~30 mm distance between the CCD and intermediate image plane ("IIP"). Theoretically, I believe that as long as the CCD is relatively close to the IIP (small fraction of the reference length) the effect should be mainly to introduce chromatic difference of magnification proportional to the distance to the IIP. If your setup somehow included a CCD fixed relative to the telelens (top window of the shutter assembly, for example) then when you change reference length and moved the eyepiece you would also be changing CCD-IIP distance at the same time and a small percentage (out of 200 mm) change in reference length would cause a much larger percentage (out of ~30 mm, or whatever it is in your setup) change in CCD-IIP distance.
Last edited by hans on Thu Aug 27, 2020 5:09 am, edited 1 time in total.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#109 Post by hans » Thu Aug 27, 2020 5:06 am

apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
...cat. # 145 eyepiece that was used with the more advanced Stereostar optics.
Do you know what the basic design of the 145 is? Does it have a singlet field lens and doublet eye lens (Kellner?) like the 181?

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#110 Post by apochronaut » Thu Aug 27, 2020 1:20 pm

It is easy to become enmeshed in theory and not see the forest for the trees.
Personally, I like the trees in my forest a lot. I have never cut a live one down for firewood, even in former times when we would use about 6 bush cords a year. I always use dead wood. I have never culled a live tree..... and the forest is healthy. The forest is maintaining itself in a state of graceful flux. When you drive the river road , where all the woodlots at the back of adjoining farms are merged along the far side of the river, one chunk, suddenly leaps 30 feet above those on either side if it. 142 years and counting since the last commercial cut through the county. 29 species are the trees but it is a forest. I use a Diastar microscope to look at the burgeoning mycorrhizal fungi. I was told 39 years years ago by a ministry of natural resources dendrologist/arborist to cull certain species out and open up the canopy so better species could thrive. He wasn't obviously an ecologist.

The use of the Photostar shutter box was entirely as a distance piece, for the proper dovetails and because it's internal baffle diameter easily held the eyepiece in place. There are no optics, blanks or physically altering devices in it whatsoever,
so it has no optical effect on the light bundle between the glass column and the bottom triplet of the eyepiece. There are a bunch of other AO photo distance pieces that can be used too. The extension collar for the 5X to the polaroid back for the series 100 shows up sometimes. I bought one for 12.00 out of the Ukraine a while ago. These are all just physical aids to put the eyepiece where it wants to be.
145 eyepieces are cheap. 30.00 at most.
as far as making a stable mount? What can be more stable than using factory made machined dovetail couplers and a helical T2 distance piece to locate an eyepiece fitted into a collar? The blank photo star body plays an integral role.

The 145 is a compensating eyepiece. It is a concave/convex singlet eyelens with an assymetrical convex/convex triplet field lens. Did not measure for assymetry but if it is, it is very little, with the greater curvature uppermost.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#111 Post by hans » Thu Aug 27, 2020 8:30 pm

Sometimes theory is the trees. But can theory not also be the forest? Whichever way the analogy goes, I think we agree, trees and forests are nice.
apochronaut wrote:
Thu Aug 27, 2020 1:20 pm
The use of the Photostar shutter box was entirely as a distance piece, for the proper dovetails and because it's internal baffle diameter easily held the eyepiece in place. There are no optics, blanks or physically altering devices in it whatsoever, so it has no optical effect on the light bundle between the glass column and the bottom triplet of the eyepiece.
Good to know, was it that way originally, or did you remove stuff? (I thought I remembered someone telling me there was a glass window in the top of it?)
apochronaut wrote:
Thu Aug 27, 2020 1:20 pm
as far as making a stable mount? What can be more stable than using factory made machined dovetail couplers and a helical T2 distance piece to locate an eyepiece fitted into a collar? The blank photo star body plays an integral role.
If those Photostar parts were cheap and readily available I would use them. I want to be able to mount a complete eye tube with color correcting doublet, not necessarily just an eyepiece. What I have decided to do is drill/tap the square 4-hole pattern at the base of the eye tube into the end of a piece of square aluminum tubing. That square tube will then nest into a larger square tube that is attached the camera port and clamp in place with two thumb screws to allow height adjustment. Then I can also easily mount an eyepiece alone (if I end up getting a 145, for example) by using the empty eye tube I blow-torched the doublet out of.
apochronaut wrote:
Thu Aug 27, 2020 1:20 pm
The 145 is a compensating eyepiece. It is a concave/convex singlet eyelens with an assymetrical convex/convex triplet field lens. Did not measure for assymetry but if it is, it is very little, with the greater curvature uppermost.
So likely the very different design of the 145 vs. the 181 explains the greater sensitivity of lateral CA to reference length? Now I probably just have to go ahead and buy one out of curiousity...

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#112 Post by apochronaut » Fri Aug 28, 2020 1:18 am

If parfocality is not important, I think you will find the cat. # 145 eyepiece will perform well, in the location I am using it at . The sensor is a whole other issue. APS-C works at about 50mm as advised. Good luck with further pursuits.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#113 Post by hans » Fri Aug 28, 2020 1:48 am

Thanks for all the input. I do have APS-C for now but the camera is a fairly old Nikon D5100 which is not very good for live view or video recording. On the other hand the DX 35mm 1:1.8G I have seems to work well afocal with the 181 if I end up doing that. May look into getting something a bit more modern, mirrorless, like micro four thirds or similar, before finalizing the setup.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#114 Post by hans » Fri Aug 28, 2020 5:13 am

hans wrote:
Fri Aug 28, 2020 1:48 am
If parfocality is not important...
One more question if you don't mind, just to rule out other possible differences between our setups if I am going to try a 145... do you have any accessories installed in the infinity space? I wonder because moving the objective away from the intended working distance in order to change reference length means infinity space is no longer really infinity space, right? So accessories that normally would have negligible effect, could become important?

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#115 Post by apochronaut » Fri Aug 28, 2020 11:09 am

no accessories for BF, no accessories for DF, fluorescence head for fluorescence and only the bertrand lens for phase. This doesn' t alter the infinity space , else the whole system downstream would get thrown out in normal use of those accessories. That is one of the basic benefits of infinity optics.

It's possible that you are over analyzing my numbers. That's why I use a helical focuser (25.00 with free shipping ). It doesn't matter to me what the reference length is as long as the photo optic gets put into the proper image plane . The assessment of that isn't determinable by what it is supposed to be because there is not enough data in order to make that determination. It is determined by empirical evidence. I did see way back that the reference length for the series 400 seemed longer than that for the earlier 34mm parfocal systems but only when I measured it did I realize it was . Numbers get thrown around but I saw 200mm and have previously quoted that but then the number 183 (182.77) seems to be the case based on data and professional information. If you take a series 10/20 photo tube, in fact I have a brand new dedicated photo tube, and measure it's reference length , it comes out right around 180mm to the lip of the tube . That is hard to get perfectly accurate because you are measuring from the outside but with a 15mm thick telan lens, 180 is pretty close. It is probably 183 to the median line in the lens. If I measure the series 400 to where I have established the eyepiece location by empirical evidence, I get around 230mm measured to the top of the eyelens. The reason I measured to there is that the eyepiece is in a depression...hard to get at the top of the ocular tube but deducting the length of the lens section of the eyepiece, 27mm, it comes to just around 200mm, which curiously is the reference length that Leica adopted for their Delta optics. At that point, the eyepiece seems as perfectly corrected as possible and it is visually parfocal and it projects exactly the same field if view as the eyepieces in the head. Parfocality to the sensor is not part of that set up.
If you want a condition where parfocality to the sensor is, you may need a different compensating optic. I tried a few but the field capture was limited.

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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#116 Post by hans » Fri Aug 28, 2020 8:00 pm

apochronaut wrote:
Fri Aug 28, 2020 11:09 am
no accessories for BF, no accessories for DF, fluorescence head for fluorescence and only the bertrand lens for phase. This doesn' t alter the infinity space , else the whole system downstream would get thrown out in normal use of those accessories. That is one of the basic benefits of infinity optics.
But this is only true as long as infinity space is actually infinity-focused, right? I brought it up because I have been interpreting some of your other suggestions (see below) as involving moving the objective away from the designed working distance and in that case the space between the objective and telelens is no longer really infinity space and the behavior (in terms of what sort of aberrations appear) could depend on what is in between, I think?
apochronaut wrote:
Fri Aug 28, 2020 11:09 am
It's possible that you are over analyzing my numbers.
The numbers are fine and it sound like you have actually measured more carefully than I have. I am also mainly positioning things empirically based on focus. 193.725 mm from the patent I mentioned just out of general interest and I have not been trying to use that number to actually set positions of stuff.

What I am not following, I think, is what exactly you mean when you talk about changing reference length vs. projection length and what that implies about objective working distance:
apochronaut wrote:
Tue Aug 04, 2020 1:30 am
...using the optics at the correct reference length. I don't mean the correct projection length, which doesn't matter, except for the sensor size.
apochronaut wrote:
Wed Aug 26, 2020 4:44 pm
Here is the thing about that correcting optic. Way back in this thread I suggested that it was the distance or tube length that needed to be adjusted in order to rid the 181 eyepiece of it's ca. You tested that theory by testing at various projection distances not reference lengths.
apochronaut wrote:
Fri Aug 28, 2020 11:09 am
... At that point, the eyepiece seems as perfectly corrected as possible and it is visually parfocal and it projects exactly the same field if view as the eyepieces in the head. Parfocality to the sensor is not part of that set up...
If the objective is fixed at its normal working distance then unless I am missing something fundamental there is only one remaining degree of freedom to adjust things while maintaining focus -- the relay optic and sensor must be moved simultaneously and in opposing directions. This sort of adjustment is what I think you mean by projection length? (And it sets relay magnification going from the intermediate image plane to the sensor.)

So then what other adjustment is possible, while maintaining focus, that does not involve moving the objective away from the normal working distance?

And if we are actually talking about moving the objective relative to the specimen plane to maintain focus while "changing reference length", then that is why I brought up accessories in the infinity space as a possible confounding factor if I am going to try to replicate your 145 setup.

I put "changing reference length" in quotes because personally I find that phrasing a bit confusing. As far as I understand, reference length is a fixed property of the design that specifies the condition under which it was optimized to minimize aberrations. That is why I keep using other phrasing like "move the objective away from the designed working distance" and if we want to talk about the effect on the image side, maybe something like "moving the intermediate image away from the reference position" would make more sense? Is that what you mean by changing reference length?

Zuul
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#117 Post by Zuul » Fri Aug 28, 2020 9:07 pm

hans wrote:
Fri Aug 28, 2020 8:00 pm
I have been interpreting some of your other suggestions (see below) as involving moving the objective away from the designed working distance and in that case the space between the objective and telelens is no longer really infinity space and the behavior (in terms of what sort of aberrations appear) could depend on what is in between, I think?
"Infinity space" exist between the objective and tube lens. That is where accessories go, and, within reason, the added length is not a factor. After the tube lens, the optical packet is converging, just like every microscope. Moving an eyepiece doesn't have anything to do with the scope being infinity corrected.

hans
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#118 Post by hans » Fri Aug 28, 2020 9:27 pm

Zuul wrote:
Fri Aug 28, 2020 9:07 pm
Moving an eyepiece doesn't have anything to do with the scope being infinity corrected.
If you move an eyepiece then refocus by moving the objective relative to the specimen the space between the objective and telelens is no longer at infinity focus. That is why I am trying to pin down what exactly is meant by "changing reference length" and whether or not apochronaut is talking about moving the objective away from working distance it was designed for.

Zuul
Posts: 212
Joined: Fri May 01, 2020 9:01 pm
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Re: Reichert 410 "Microstar IV" head -- corrective element present in binocular path but not trinocular camera port

#119 Post by Zuul » Sat Aug 29, 2020 12:52 am

hans wrote:
Fri Aug 28, 2020 9:27 pm
Zuul wrote:
Fri Aug 28, 2020 9:07 pm
Moving an eyepiece doesn't have anything to do with the scope being infinity corrected.
If you move an eyepiece then refocus by moving the objective relative to the specimen the space between the objective and telelens is no longer at infinity focus. That is why I am trying to pin down what exactly is meant by "changing reference length" and whether or not apochronaut is talking about moving the objective away from working distance it was designed for.
That’s not the case. Infinity focus refers to the image being collimated to infinity rather than converging or diverging. It doesn’t have anything to do with the image sharpness. The light exiting the objective being focused to infinity has nothing to do with the point/plane of focus in front of the objective.


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