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Focus Stacking using Variable focus lens (VFL), anyone ?

 
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Vish_007



Joined: 11 Feb 2011
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Location: Birmingham, Alabama - USA

PostPosted: Fri Jul 24, 2015 7:51 am    Post subject: Focus Stacking using Variable focus lens (VFL), anyone ? Reply with quote

Came across this interesting article in the current issue of Microscopy Today, vol 13, # 4, July 2015., pages 18-24 (www.microscopy-today.com)

Authors describes a very rapid method of obtaining images with extended depth of focus (DOF) using variable focus lens (VLF), full link to the article;
http://paedia.com/Photomontage_microscopy.html
http://paedia.com/Docs/MT0701151.pdf

Interested to know if anyone the posters have used this method ?

Best,
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g4lab



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PostPosted: Fri Jul 24, 2015 10:34 am    Post subject: Reply with quote

Very interesting web site. Look at the Diabloc too. Probably converted a little LCD screen to a light source filter controller. Very clever!

Didn't Rik post a very similar technique utilizing a factory internal focus lens not too long back to accomplish the same thing.

The only thing about that website is all the stuff is cool and custom made and kind makes my little mind think, "if you have to ask, you can't afford it!" Laughing
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g4lab



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PostPosted: Fri Jul 24, 2015 10:37 am    Post subject: Reply with quote

g4lab wrote:
Very interesting web site. Look at the Diabloc too. Probably converted a little LCD screen to a light source filter controller. Very clever!

Didn't Rik post a very similar technique utilizing a factory internal focus lens not too long back to accomplish the same thing.

The only thing about that website is all the stuff is cool and custom made and kind makes my little mind think, "if you have to ask, you can't afford it!" Laughing



http://www.photomacrography.net/forum/viewtopic.php?t=14569&highlight=stacking+internal+focus
Here's a start. Seems like you could also mount a camera and lens over a trinoc and have similar results.
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rjlittlefield
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PostPosted: Fri Jul 24, 2015 11:08 am    Post subject: Re: Focus Stacking using Variable focus lens (VFL), anyone ? Reply with quote

Vish_007 wrote:
Interested to know if anyone the posters have used this method ?

Sure. The reference that g4lab gave is a good one, because it also addresses fundamental limitations of the technique regarding stack depth and aberrations. The technique of adjusting focus in back of the objective is a good one at low magnification and becomes not nearly so good at high magnification, as discussed at http://www.photomacrography.net/forum/viewtopic.php?p=92144#92144 in that thread.

--Rik
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rjlittlefield
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PostPosted: Fri Jul 24, 2015 11:17 am    Post subject: Reply with quote

Forgot to mention...

The issue of acquiring as video rather than as separate still exposures is completely independent of how you focus. For an early reference on that, here in this forum, see http://www.photomacrography.net/forum/viewtopic.php?t=1664. There's a possibly amusing later escapade at http://www.photomacrography.net/forum/viewtopic.php?t=11130.

The first time that I ever stacked from video was back in about 1997, before consumer-class technology was really up for it. In that case, I ended up using a quick-but-sleazy stacking algorithm to process on the fly, never storing more than a single frame of the video. Given that this was being done on a single-processor laptop, you can probably imagine that the images weren't very good. Life is better now...

--Rik
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Pau
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PostPosted: Fri Jul 24, 2015 11:32 am    Post subject: Reply with quote

I don't understand well the article, but i think that they are focusing the lens more than altering the FL like in a zoom. Maybe they are changing the focus of a relay lens in an afocal microscope setup (?)

In any case I don't see the convenience over moving the microscope focus knob.

The fast image adquisition seems due to the video signal use in place of the photo outut.The syncrhonisation they do could be the most interesting aspect.

But video output has lower resolution and less flexibility than good RAW frames. Maybe with a modern 4k camera...

Their system seems more oriented to speed than towards quality.

(Please correct my interpretation mistakes)
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Vish_007



Joined: 11 Feb 2011
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PostPosted: Fri Jul 24, 2015 3:45 pm    Post subject: Reply with quote

Thank you g4ab, Rik and Pau for the previous postings;

Agree, appear to be more suited for low magnification work.

VFL manufacturer site lists more applications e.g. machine vision, Laser processing in 3 dimensions(3D printing?) and low power microscopy. One application intrigued me the most was VFL use for optical coherence tomography (OCT) , 3D imaging of skin surface? More mind boggling possibilities than I thought.

Additional link to the manufactures of the VFL lens, Optotune AG, Dietikon Switzerland; http://www.optotune.com/products/focus-tunable-lenses/electrical-lens-el-10-30?task=view&id=18
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Chris S.
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PostPosted: Fri Jul 24, 2015 10:11 pm    Post subject: Reply with quote

Looking at the patent, my sense is that an examiner goofed and the patent should not have been granted. Zoom projection eyepieces are nothing new, and the use of one for focus stacking is obvious to anyone proficient in the art (to use the legal phrase). For a US patent to be granted, the claimed use cannot be obvious to someone proficient in the art. [This said, I can't blame the examiner too much; quite a few of us here at PMN are far more proficient in the art of focus stacking than could be reasonably expected of any patent examiner. However, our posts exist in the public domain, and represent adverse prior art (in patent law, if adverse prior art exists, a patent can not be awarded, as it is therefore not novel).]

As to how well the greater scheme will work (patented and unpatented elements taken together), I'm doubtful. If asked to build a rapid-acquisition microscope stacking system, I'd move hardware (our community's well-known and widely-used approach) quickly and with automation, rather than use a zoom or varifocal projection eyepiece.

I've had involved offline conversations with members of this forum about how to create high-throughput stacking systems. None of us has yet built one, because we don't need it, and there would be a cost in money and time. Should an institution ever approach me with such a need and the funds to cover costs, I'll jump at the opportunity with delight, and take great satisfaction in building the system. (Then document and post it here, if permitted--thus creating more adverse prior art. Very Happy)

Rapid focus adjustment and image acquisition are the easy nuts to crack. In a high-throughput scenario, a much tougher issue would be rapid and safe automated handling of subjects of different sizes and shapes. ("Safe" in the sense of minimizing risk to the subjects photographed, which are, in some cases, scientifically or industrially important specimens).

So I think the fellows behind this product are attacking the wrong problem in the wrong way. I also think they spent money obtaining a patent on something obvious. (If so, their patent might be quickly nullified in court, if anyone were to challenge it.)

Lest anyone think I oppose patent rights in general: No, I do not. Quite the contrary, I have great admiration for people who invent things truly novel and useful. And I hope that these geniuses benefit financially from their inventions, as they well deserve. This return to contribution represents the U.S. patent system at its best. But I also know that bad patent applications can squeak past even a solid examiner, and receive a United States patent--perhaps wrongly. I my opinion, such an error happened here.

--Chris
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g4lab



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PostPosted: Sat Jul 25, 2015 2:13 am    Post subject: Reply with quote

The lens that is used by the maker of this system seems to be one of those lenses that vary the vocal length by expanding or contracting the radius of a silicone transparent balloon. The lens seems to range from 10 -30mm a three to one zoom range. I would be interesting in seeing how the optic affects pixel peeping results. I suspect it might not be a top performer though it is made in Switzerland.

The owner of Surplus Shed has a patent related to such optics.
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Vish_007



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PostPosted: Sat Jul 25, 2015 9:18 am    Post subject: Reply with quote

Chris. S
Quote:
a rapid-acquisition microscope stacking system, I'd move hardware (our community's well-known and widely-used approach) quickly and with automation, rather than use a zoom or varifocal projection eyepiece

Such system will be helpful in bright-field or epifluorescence microscopy. Current limited DOF of 100x objective makes it difficult to document FISH probe results (chromosome loss, gain or translocation) in tissue sections / cytology smears. FISH and chromogen in-situ hybridization (CISH) studies are routinely performed on neoplastic tissue (carcinomas, lymphomas and leukemias).
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Chris S.
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PostPosted: Sat Jul 25, 2015 10:42 pm    Post subject: Reply with quote

Thanks, Vishnu, for your insights! Very Happy I've followed up via PM.

--Chris
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Pau
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PostPosted: Sun Jul 26, 2015 1:29 am    Post subject: Reply with quote

Vish_007 wrote:
Such system will be helpful in bright-field or epifluorescence microscopy. Current limited DOF of 100x objective makes it difficult to document FISH probe results (chromosome loss, gain or translocation) in tissue sections / cytology smears. FISH and chromogen in-situ hybridization (CISH) studies are routinely performed on neoplastic tissue (carcinomas, lymphomas and leukemias).


Again I dont see any relevant advantage over changing the lens to subject distance.
Some high grade research microscopes, mainly confocal, do this automatically by means of computer controlled piezoelectric focusers placed between objective and nosepiece or at the nosepiece construction itself. They are fast and extremely acurate (and of course expensive!)
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Vish_007



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PostPosted: Sun Jul 26, 2015 11:36 am    Post subject: Reply with quote

Pau
Quote:
Some high grade research microscopes, mainly confocal, do this automatically by means of computer controlled piezoelectric focusers placed between objective and nosepiece or at the nosepiece construction itself. They are fast and extremely acurate (and of course expensive!)


Totally concur, Confocal microscopes are intended for research use mostly. But it is not possible to use Confocal microscopy in routine FISH/CISH laboratories due to short turnaround times (TAT) requirements, work-flow and costs etc.
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