Macro focussing rails

Started 5 months ago | Questions
mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Thorlabs Piezo stage for a Stack&Stitch system

Guito55 wrote:

Hi Mike, thanks for correcting me and for your fascinating work! I called up my friend, an engineer, who I took the photos for. I have little science/engineering formal knowledge, He couldn't stop laughing. He explained that it wasn't a piezoelectric stage, that the steps were in micrometers not nanometers and that it wasn't a microprosser at all. I blame it on old age and reading your posts thinking I was doing what you were doing. :}
So in answer to your question: I didn't. I am interested how to get nm steps without a stepper motor, though. My microscopy hasn't reached that level yet, but maybe one day.

Your work is super inspiring.

Thanks.

The DoF follows as DoF = lambda/(NA^2), where lambda is light wavelength (~.550um for green), NA is lens numerical aperture. At 20X with NA of 0.42 the DoF is just ~3um, so you need to make focus steps smaller than 3um, so maybe 1.5um. At higher magnifications the DoF is even smaller and the step size thus smaller.

As you can imagine accurately taking steps this small requires special equipment, thus the development of the piezo stages for focus stepping.

Best,

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Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

Guito55 Regular Member • Posts: 164
Re: Thorlabs Piezo stage for a Stack&Stitch system

Thanks for the explanation Mike! I suspect this is a large part of why my microscopy (rocks, not cells) hasn't produced any good images with stacking. The single image has always been best, even with a low DoF

I love following your work and one day hope to understand it.

vd Berg Forum Member • Posts: 87
Re: Thorlabs Piezo stage for a Stack&Stitch system

Hi Mike,

If I understand correctly you’re into focus stepping DIY controller+stacking rails+software for realizing your own vision and for costs reasons. There is interest, you’re followed, but DIY is difficult, even with (moderate) electronic knowledge. So can you tell (maybe a setup to start with, which later on can be expanded), which (of-the-shelf) (closed loop) piezo stage(s), controller(s), software for focus stepping are (as much as possible) plug-and-play?

Regards,

mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Thorlabs Piezo stage for a Stack&Stitch system

Guito55 wrote:

Thanks for the explanation Mike! I suspect this is a large part of why my microscopy (rocks, not cells) hasn't produced any good images with stacking. The single image has always been best, even with a low DoF

I love following your work and one day hope to understand it.

My work is more into semiconductor chips and thus requires moderately high magnifications (usefully below 20X) but extreme sharpness. Many images are displayed and viewed in very large areas, and many are "zoomed" in so the individual features can be observed.

For getting started into focus stacking the Wemacro focus rail system is very nice and reasonable.

Best,

-- hide signature --

Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Thorlabs Piezo stage for a Stack&Stitch system

vd Berg wrote:

Hi Mike,

If I understand correctly you’re into focus stepping DIY controller+stacking rails+software for realizing your own vision and for costs reasons. There is interest, you’re followed, but DIY is difficult, even with (moderate) electronic knowledge. So can you tell (maybe a setup to start with, which later on can be expanded), which (of-the-shelf) (closed loop) piezo stage(s), controller(s), software for focus stepping are (as much as possible) plug-and-play?

Regards,

I don't know of any type piezo stage that's PnP. These piezo electric stages and controllers are usually developed for industrial applications including semiconductor processing, and usually very costly. They aren't intended for focus stacking either, so the devices and software are for the mentioned industrial applications.

Because of the lack of piezo stages for focus stacking, and the cost, when some precision Physik Instrumente devices (P601K and P603K) came available on eBay we purchased a few. This began the development cycle, starting with an open loop system then a closed loop system for both the P601K and P603K stages.

So we've developed our own piezo stage controllers, setups and software specifically for focus stacking.

A per above the Wemacro (or Stackshot) is a good means to get into automated focus stacking, then migrate to the custom Trinamic stepper motor controllers & software we've developed. Add the THK KR20 rails with a 400 step motor and you have the best possible stepper motor based focus stacking rail system at any cost IMO, they are superb!! These also can do multi-axis control up to 4 axis (XYZR) from a single controller.

Some have skipped and jumped directly into the Trinamic based controllers with THK KR20 rails like this note I just received.

"I'm not sure if you remember me or not, but I purchased an XYZ controller from you a few months back and had the intention to modify for a rotational axis as well for stacked rotation videos. I just wanted to say thanks, it has been working great and I've had no problems. Coupled with the kr20 and a nema14 on a rotation stage the motion is buttery smooth fresh out of the camera, it's really been amazing! I've probably put a good 200k frames on the controller usually 10-20k at a time since December with no issues"

If you move to very high magnifications well beyond 20X, then consider the piezo stages, which are at another level of complexity.

Best,

-- hide signature --

Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

vd Berg Forum Member • Posts: 87
Re: Macro focussing rails

Hi,

I raise this issue because a motorized stage, like StackShot with good references, gave the impression not to be fully specified (parameters) by the manufacturer, in a way that other motorized stages, like Thorlabs, Physike Instrumente (PI), seemed to be specified (parameters).

Are there other (fully) specified (plug-and-play, P&P) motorized stages in between the (P&P) StackShot and (Do-It-Yourself) Thorlabs, PI?

Features for a motorized stage (parameters) like e.q. travel range, velocity (max, min). acceleration (max, min, at a load), resolution, bidirectional repeatability, flatness and straightness over full travel range, horizontal and vertical load capacity (max), min achievable incremental movement, home location accuracy, absolute on-axis accuracy, backlash, etc.

Regards,

mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Macro focussing rails

Not aware of any more info than already mentioned and  posted. If that's not enough best you get a setup and make your own detailed measurements and be sure to post your findings back here so we all can benefit.

Best,

-- hide signature --

Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

GSWayne
GSWayne Regular Member • Posts: 154
Re: Macro focussing rails

I recently got a We Macro rail and it was very much a plug and play arrangement with a Sony A7Rii camera and a Samsung phone.  I am only using if for 5X macro so I am not concerned with micron tolerances.  It seems to do fine with 50 to 200 micron steps that are appropriate for that level of magnification.

It works fine for watch parts

or old ICs, back when the components were microns not angstroms

 GSWayne's gear list:GSWayne's gear list
Sony a7R II Sony FE 90mm F2.8 macro Sony FE 70-300mm F4.5-5.6 G OSS Sony FE 24-105mm F4 Tokina Firin 20mm F2 FE AF +1 more
mawyatt2002
mawyatt2002 Contributing Member • Posts: 502
Re: Macro focussing rails

The Wemacro is fine and the best value in a automated focus rail for general purpose use. I have one and used it often.

Here's an example of how DoF plays: With an Effective Aperture (EA= Aperture(1+M) ) of 24 (Aperture =4), the DoF is ~51um (DoF = Lambda/NA^2, Numerical Aperture =M/(2EA) with a resolution of ~2.64um (R= Lambda/2NA), all valid for small Numerical Aperture. Remember most cameras (except Nikon) report only Lens Aperture not Effective Aperture, so a F4 at 5X is actually F24

So you want your step size to be smaller than the DoF otherwise focus banding will occur, in the example a good choice would be ~30um.

Note that resolution is inversely proportional to NA, but DoF is inversely proportional to NA^2. So a 2 times increase in aperture (larger NA) causes 2X improvement in resolution but a 4X reduction in DoF. You want large NA for high resolution but eventually the wavelength of light becomes a barrier (Lambda is 0.55um for green), but the DoF quickly diminishes with larger NA and this is where small focus step sizes come into play. Tradeoffs everywhere you turn!!

Best,

-- hide signature --

Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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