my positioning stack: X, Y, yaw, pitch

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rjlittlefield
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my positioning stack: X, Y, yaw, pitch

Post by rjlittlefield »

Contributing to the discussion of subject positioning rigs, here is a snapshot of my positioner stack:

Image

Starting from the bottom, this consists of:

1. Block of wood with Arca rails screwed to it on several faces
2. Lift-type linear stage (Y axis for a camera in landscape orientation)
3. Horizontal linear stage (X axis for a camera in landscape orientation)
4. Goniometer, small angular travel with large radius
5. Rotary table with steel plate added on top
6. Several 1/4" magnets
7. L-bracket of steel, with balsa plates glued to it

As workflow, what I do is to pin my subject to the balsa plate so that the area of interest lies near the height of the rotational axis of the goniometer and is tilted close to what I want. Then I slide around the L bracket that is magnetically held to the rotary stage, until the area of interest lies near the axis of the rotary table. Working in live view, I then turn the controls of the positioning stack so as to center the area of interest and tweak up the angular alignment. Because the subject is located very near the centers of rotation, adjusting the angles has only a small affect on framing and focus.

Configured as shown here, the background for the subject would be mounted on the balsa plate, only a short distance behind the subject. If I want clear space behind the subject, then the rotary table gets spun 90 degrees so that the camera looks past it. Or maybe the L-bracket with balsa plate gets removed altogether, and some other subject holder gets stuck down with magnets instead.

The ability to slide holders around with magnets on the steel plate is surprisingly helpful. It reminds me a little of the "gliding stage" concept that I've seen used with stereo microscopes.

Note that this setup uses only one goniometer, not a matched pair. I don't think there's any loss of functionality, compared with using two goniometers. The two axes of rotation associated with getting the subject parallel with the sensor are provided by the goniometer and the rotary table. Rotation of the image within the frame is done by rotation of the tube assembly in its holding clamps, with the camera hanging off the back. (Tube and camera not shown here.)

As always, I make no representation that this is the best way to do things, only it works well for me. Hiding behind the diffuser shown above is a 50X objective, imaging a roughly 0.44 mm x 0.3 mm section of stink bug. Yesterday the same space was occupied by a 100X objective, imaging about 0.22 x 0.15 mm. Shooting at such high magnifications is close to impossible without some sort of fine mechanical control.

If I recall correctly, I bought the two linear stages and the rotary table new on eBay, and paired those with a used goniometer that I had picked up earlier. These are 60mm x 60mm bases.

I have not been able to find a new goniometer like this, made by any of the inexpensive Chinese manufacturers on eBay. Perhaps somebody else knows where they can be found?

--Rik

dhmiller
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Re: my positioning stack: X, Y, yaw, pitch

Post by dhmiller »

If Zerene Systems ever starts to sell these, please let me know. ;-)

rjlittlefield wrote:Contributing to the discussion of subject positioning rigs, here is a snapshot of my positioner stack:

<clip>

Starting from the bottom, this consists of:

1. Block of wood with Arca rails screwed to it on several faces
2. Lift-type linear stage (Y axis for a camera in landscape orientation)
3. Horizontal linear stage (X axis for a camera in landscape orientation)
4. Goniometer, small angular travel with large radius
5. Rotary table with steel plate added on top
6. Several 1/4" magnets
7. L-bracket of steel, with balsa plates glued to it

As workflow, what I do is to pin my subject to the balsa plate so that the area of interest lies near the height of the rotational axis of the goniometer and is tilted close to what I want. Then I slide around the L bracket that is magnetically held to the rotary stage, until the area of interest lies near the axis of the rotary table. Working in live view, I then turn the controls of the positioning stack so as to center the area of interest and tweak up the angular alignment. Because the subject is located very near the centers of rotation, adjusting the angles has only a small affect on framing and focus.

Configured as shown here, the background for the subject would be mounted on the balsa plate, only a short distance behind the subject. If I want clear space behind the subject, then the rotary table gets spun 90 degrees so that the camera looks past it. Or maybe the L-bracket with balsa plate gets removed altogether, and some other subject holder gets stuck down with magnets instead.

The ability to slide holders around with magnets on the steel plate is surprisingly helpful. It reminds me a little of the "gliding stage" concept that I've seen used with stereo microscopes.

Note that this setup uses only one goniometer, not a matched pair. I don't think there's any loss of functionality, compared with using two goniometers. The two axes of rotation associated with getting the subject parallel with the sensor are provided by the goniometer and the rotary table. Rotation of the image within the frame is done by rotation of the tube assembly in its holding clamps, with the camera hanging off the back. (Tube and camera not shown here.)

As always, I make no representation that this is the best way to do things, only it works well for me. Hiding behind the diffuser shown above is a 50X objective, imaging a roughly 0.44 mm x 0.3 mm section of stink bug. Yesterday the same space was occupied by a 100X objective, imaging about 0.22 x 0.15 mm. Shooting at such high magnifications is close to impossible without some sort of fine mechanical control.

If I recall correctly, I bought the two linear stages and the rotary table new on eBay, and paired those with a used goniometer that I had picked up earlier. These are 60mm x 60mm bases.

I have not been able to find a new goniometer like this, made by any of the inexpensive Chinese manufacturers on eBay. Perhaps somebody else knows where they can be found?

--Rik

viktor j nilsson
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Post by viktor j nilsson »

Re: goniometers, I picked up a set of these:

https://www.ebay.com/itm/TOPTEK-X-Y-Gon ... SwBFlbyXFZ

I notice there's only one left now.
They are 40x40mm, which matches my other stages.

It's the cheapest matched pair I've come across (at least shipped to Sweden). I've never tried high quality goniometers from Newport etc. I'm sure they are nicer. But these work fine as far as I can tell.

I was a little surprised at first that you didn't care for sideways tilt, especially since many here swear by their matched goniometer pair. But if course it makes perfect sense to rotate the camera assembly instead. In my case, using finite objectives, it's actually probably easier to rotate the camera behind my bellows than reaching for the goniometer!

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Post by ray_parkhurst »

I have the same Opto-Sigma +/-8-deg goniometer. It perfectly complements the inexpensive 8-deg tilt adapters available for various mounts. They work well in concert to give variable tilt to coins to enhance color presentation by enabling "pseudo-axial" lighting. The tilt at camera fixes the DOF effect of tilting the coin, though of course there is still some perspective distortion.

That Opto-Sigma goniometer is a fine instrument. Unlike most, it is a crossed-roller bearing type, so is extremely stable and smooth. For manual use I don't like the geared drive, and so far have not found a good replacement knob for it, but oh well.

Macro_Cosmos
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Post by Macro_Cosmos »

I got this funky thingo for cheap.
https://www.ebay.com/itm/Elevation-Azim ... 2749.l2649

Seems like some DIY laser holder mount for astro positioning? It came with a thick tube clamped, I'm guessing it houses some kind of laser. Not sure, but it's very well made. It's obviously not as precise as optomechanical goniometers, but it offers steeper pitch and yaw adjustments.

My own positioning system features a heavy duty height stage from Thorlabs and a couple linear translation stages with rotation. I don't use goniometers as I mainly deal with flat stuff such as butterfly/moth wings or uncapsulated silicon chips.

I do recommend adding height adjustment even though the Wemacro/Stackshot systems have precise adjustments already, it makes stuff very convenient. This is speaking in terms of a vertical setup, the same applies to horizontal where height adjustment is vital (IMO) and back/forth isn't but I do still recommend having it.

I also bought this during China's celebration day for singles (11-11), which no doubt is why I'm single too :) :
Image

It's kind of like the arca-swiss L60 or Leofoto's version. The difference being this one offers +/- 3.5 deg adjustments, whereas the L60 offers 10deg. The L60 is also taller which I personally don't like, though centre of gravity won't matter if it's used for specimens.

It feels very well made, adjustments are smooth, no play. While Marsace states that this isn't a replacement of proper geared heads such as the arca swiss C1, it's still a good tool for positioning, assuming one owns a ballhead already.

At first glance, I dislike the built-in arca swiss dovetail, I want a way to mount it directly onto typical M6 or 1/4in systems, not through a clamp. It won't be difficult to DIY something though.

I'll report on the DW-4 when I get back on grid. It's been a week without power and I feel like a caveman.

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Post by rjlittlefield »

Ray, thanks for identifying that goniometer. It does not carry a name or model number, so I've never known exactly what it is. I can confirm that this unit does have crossed-roller bearings, since one roller is visible when the table is slid all the way to one end.

--Rik

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Post by ray_parkhurst »

rjlittlefield wrote:Ray, thanks for identifying that goniometer. It does not carry a name or model number, so I've never known exactly what it is. I can confirm that this unit does have crossed-roller bearings, since one roller is visible when the table is slid all the way to one end.

--Rik
No problem. That goniometer was marketed under both Sigma Koki and Opto Sigma brands, and its part number is VRB-046-CO in case you want to research it. Here's a link on LightGlass Optics:

http://www.lightglassoptics.com/OptoSig ... _1225.html

Edited to add: LGO describes these improperly as being 40x40mm

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Post by ray_parkhurst »

BTW, just saw this nice Newport GM-1 Tip/Tilt Gimbal Mount for an excellent price on LGO:

http://www.lightglassoptics.com/Newport ... _1191.html

Edited to add: hmm, they are cheaper on eBay...

rjlittlefield
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Post by rjlittlefield »

ray_parkhurst wrote:LGO describes these improperly as being 40x40mm
They have the travel wrong also, listed as +/-5 degrees instead of the actual +/-8.

I find it highly amusing that LGO lists the price as $850. The one used in my stack is half of a mated but unmatched pair that I purchased on eBay in 2013 for $200. This may be the best deal I've ever gotten, and I didn't even know it! Of course a flimsy look-alike with plastic slides would work fine for my application, since it doesn't require carrying any load or any large number of cycles.

--Rik

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Post by Macro_Cosmos »

ray_parkhurst wrote:BTW, just saw this nice Newport GM-1 Tip/Tilt Gimbal Mount for an excellent price on LGO:

http://www.lightglassoptics.com/Newport ... _1191.html

Edited to add: hmm, they are cheaper on eBay...
Gimbal mounts for optics range from $10 a piece all the way to $100 used. I've bought some Thorlabs ones for $12 (KM100) a piece before. Not sure how useful it would be for specimens though, I bought them for some experiments.

I'll share the two good listing I have saved. They are on fleabay.
"MMT" $300 including XYZR: 202829880928
Generic Goniometers, $49 a piece: 223495253386

ray_parkhurst
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Post by ray_parkhurst »

Macro_Cosmos wrote:
ray_parkhurst wrote:BTW, just saw this nice Newport GM-1 Tip/Tilt Gimbal Mount for an excellent price on LGO:

http://www.lightglassoptics.com/Newport ... _1191.html

Edited to add: hmm, they are cheaper on eBay...
Gimbal mounts for optics range from $10 a piece all the way to $100 used. I've bought some Thorlabs ones for $12 (KM100) a piece before. Not sure how useful it would be for specimens though, I bought them for some experiments.

I'll share the two good listing I have saved. They are on fleabay.
"MMT" $300 including XYZR: 202829880928
Generic Goniometers, $49 a piece: 223495253386
For macro purposes, the tip/tilt or gimbal mounts are most useful for ensuring the specimen stage is perfectly flat vs the sensor, when shooting flat subjects, to minimize DOF requirements. I don't currently have a tip-tilt integrated but plan to do so in my next system build. They can be invaluable when doing tests using wafers, and similarly when photographing coins. It's much easier to point the camera at the stage and adjust the tip-tilt for flatness, than to adjust the camera pitch/yaw. The drawback is that if you are also stacking, then it's beneficial to have the optical axis aligned to the linear stage axis, epecially for deeper stacks. So I guess ultimately the process is to align the camera to the linear stage, then move the subject stage under the camera axis and adjust tip/tilt for flatness.

viktor j nilsson
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Post by viktor j nilsson »

Macro_Cosmos wrote:
ray_parkhurst wrote:BTW, just saw this nice Newport GM-1 Tip/Tilt Gimbal Mount for an excellent price on LGO:

http://www.lightglassoptics.com/Newport ... _1191.html

Edited to add: hmm, they are cheaper on eBay...
Gimbal mounts for optics range from $10 a piece all the way to $100 used. I've bought some Thorlabs ones for $12 (KM100) a piece before. Not sure how useful it would be for specimens though, I bought them for some experiments.

I'll share the two good listing I have saved. They are on fleabay.
"MMT" $300 including XYZR: 202829880928
Generic Goniometers, $49 a piece: 223495253386
The screw-fed one in the 223495253386 listing looks pretty much identical to the ones I linked to above. But note that in the listing I linked above, you get a matched pair for $99. Wider radius on the lower one, smaller radius on the upper.

viktor j nilsson
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Joined: Fri Mar 01, 2013 1:43 am
Location: Lund, Sweden

Post by viktor j nilsson »

Although I just noticed that the item I linked is now sold out, so that point is moot...

rjlittlefield
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Post by rjlittlefield »

Adding some more context to the positioning stack, here is the way that I use it in both horizontal and vertical configurations.

Image

Image

The support rod is Newport Model 70 mounted on a Newport VPB base, that pair fastened to the optical table by four bolts with DIY wingnut heads so I don't have to hunt down a tool to move it around. Sliding on the optical rod is a Newport 370-RC rack-and-pinion rod clamp, on which is mounted a Arca-Swiss clamp. The rod, base, and clamp all came from eBay as a single buy. The optical breadboard I bought new, because I got tired of waiting for something the right size to turn up on eBay.

As always, no claim that this is the best approach. It's just a place I've gotten to by iteratively improving stuff that obviously needed it.

--Rik

ray_parkhurst
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Post by ray_parkhurst »

I see you're a Harley man. I've got a few of those waiting to be built into a system.

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