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01-09-2011, 05:19 PM   #16
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You may want to look up Thomas Shahan and his setup, this is the kind of magnification he is getting. However he is focus stacking his images. Which would be far easier on your setups, I don't expect any of your parts are just going to walk off.

01-09-2011, 06:31 PM   #17
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Your microscope image is excellent. Add some more dramatic lighting to enhance 3d aspects perhaps. Is it high enough magnification for your purposes?
01-09-2011, 07:09 PM   #18
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QuoteOriginally posted by newarts Quote
Your microscope image is excellent. Add some more dramatic lighting to enhance 3d aspects perhaps. Is it high enough magnification for your purposes?
Allas I no longer have this Nikon stereo microscope but will be trying to get back to this level image with my current cheap scope from China.
01-09-2011, 07:18 PM   #19
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Here is a example of what I'd like to achieve.

Name:  Cutting.jpg
Views: 1002
Size:  108.2 KB

This photo is nice enough but I need to be able to clearly show the laser cut edge. This tube is .180" in diameter and the laser cut wall is .010" thick. The actual appearance of the cut is a series of tiny vertical lines. This photo is too "cleaned up" to serve as a technical reference.

thanks again for all the suggestions
joe

01-10-2011, 02:46 AM   #20
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QuoteOriginally posted by joelovotti Quote
Here is a example of what I'd like to achieve.

Attachment 80319

This photo is nice enough but I need to be able to clearly show the laser cut edge. This tube is .180" in diameter and the laser cut wall is .010" thick. The actual appearance of the cut is a series of tiny vertical lines. This photo is too "cleaned up" to serve as a technical reference.
...
joe
The wall is .010" ~ .25mm thick, about the size of a single pixel on a computer display. I suppose the wall should be about 5mm thick on the computer display, for an overall magnification of 20X (your photo is about half that overall mag), but even that may not be big enough to show the laser cut lines (the pitch of the lines must be a few times larger than the pixel pitch of the display to be resolved.)

What is the approximate pitch of the parallel laser machining marks?

You may wonder why you can see the machining marks as you look through the microscope, but not on the computer display. I think there are two main reasons:
1) your eye's resolution is better than that of the computer display.
2) your eye is part of the microscope's optical system and unconsciously adjusts itself as you focus the microscope to construct a deeper mental image than actually shown by the optics.

Nikon says it this way...

QuoteOriginally posted by http://www.microscopyu.com/articles/formulas/formulasfielddepth.html:
The human eye can normally accommodate from infinity to about 25 centimeters, so that the depth of field can considerably greater than that given by the equation above when one observes the microscope image through the eyepieces...
So what can you do? You can increase the magnification to resolve the machining marks on the computer display, but this will decrease the depth of field so you may have to do some through focus stacking to recover the overall image. It is time consuming but not difficult.

Another solution is to use a Scanning Electron Microscope which inherently has a huge depth of field. Iowa State University has a free on-line SEM you might use to explore this option.

Dave
01-10-2011, 03:22 AM   #21
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As for focus stacking, these might be of use:

StackShot - Focus Stacking Macro Rail
Helicon Focus - extended depth of field, focus stacking, 3D visualization
01-10-2011, 04:56 AM   #22
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QuoteOriginally posted by newarts Quote
The wall is .010" ~ .25mm thick, about the size of a single pixel on a computer display. I suppose the wall should be about 5mm thick on the computer display, for an overall magnification of 20X (your photo is about half that overall mag), but even that may not be big enough to show the laser cut lines (the pitch of the lines must be a few times larger than the pixel pitch of the display to be resolved.)

What is the approximate pitch of the parallel laser machining marks?

You may wonder why you can see the machining marks as you look through the microscope, but not on the computer display. I think there are two main reasons:
1) your eye's resolution is better than that of the computer display.
2) your eye is part of the microscope's optical system and unconsciously adjusts itself as you focus the microscope to construct a deeper mental image than actually shown by the optics.

Nikon says it this way...



So what can you do? You can increase the magnification to resolve the machining marks on the computer display, but this will decrease the depth of field so you may have to do some through focus stacking to recover the overall image. It is time consuming but not difficult.

Another solution is to use a Scanning Electron Microscope which inherently has a huge depth of field. Iowa State University has a free on-line SEM you might use to explore this option.

Dave
You have the math right. I most likely won't get everything I'm looking for but I'm sure with the ideas presented here and possibly some focus stacking I'll get something much better.

Last edited by joelovotti; 01-10-2011 at 04:51 PM.
01-10-2011, 08:00 AM   #23
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To give you a sample of what the binocular lens rig will do, I have a guitar with a .022 string, took a picture last night. I didn't quite peg the focus good enough, tired eyes, but this shot will give you an idea what the rig will do, since the string is the same diameter you're dealing with. I don't know what diameter the smaller wraps around the string are, but the .011 string shows up just this good too. Just not quite as large. This was taken with onboard flash and paper diffuser, at f11, at a distance of about 4 inches under low light in my bedroom. This is as close as it will focus, and maximum magnification.

I also found out something, a pinhead is .065". I didn't know that until I got curious last night while measuring strings and remembering telling you the flower was about .030-.040...so I got out my micrometer and learned something new. Never dreamed one day I'd be measuring the head of a pin...

Guitar Tuning Head - Pentax User Photo Gallery

01-16-2011, 01:37 PM   #24
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First Attempt at Solution

I ran through some quick tests with the equipment I had.

Test shots were taken with:

28A with Reversing Ring and Extension Tubes
50A with Reversing Ring and Extension Tubes
DA35 Limited
DA35 with Tiffen to Close Up Lenses

I didn't try the light table since I would lose my ability to creatively frame and angle the part.

I didn't try the binocular since it would require too much work for a first round try.

I didn't try reversing the 28 on my 100 macro because I don't have that adapter yet but I will go out and purchase the ring I need this week.

The best result was the Pentax 28mm A series F2.8 reversed and mounted on my K5 with Extension Tubes. The photo is below:

View Picture EXIF
Name:  Reversed 28A.jpg
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This is a 10 minute quick setup. No thought to proper lighting or superfine focus. No focus stacking. It's not bad. If I had to live with this I could.

The part is .065 inches in diameter and the cut wall is .006 inches thick.

It is cropped about 30% from the original.

Any thoughts to proper aperture for best depth of field without losing sharpness?

What would be the difference in magnification and quality of the 28 reversed and mounted on my 100 macro?
01-16-2011, 02:23 PM   #25
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I don't see the fine parallel laser machining marks you mentioned. Were they present in this part?

In what ways is this photo better than those taken with other setups? Enlargement? Contrast/sharpness? I'm wondering what directions you'd like to see improvements?

Theory is straightforward.
DOF=2CN(1+m)/m^2 where C is allowable spot size on sensor, N is f-number, and m is magnification
Diffraction spot maximum ~C => 1.3N(1+m)/1000 millimeters

I'll set the diffraction spot size equal to the spot size used to define depth of field (by definition, an image spot larger is fuzzy); C= 0.019mm (common for APS-C sensors). This results in a maximum f-number

Nmax=19(1+m)/1.3 or Nmax=14.6(1+m)

This is reasonable for crop sensors; ie, diffraction sets in at about f15 for normal photography. It also means that for macro work, as magnification increases the nominal f=number (ie, set on the lens barrel or with a camera adjustment should be decreased as magnification increases) according to (I'll round up to F:16 for convenience):

N_nominal_diffraction_limit ~ 16/(1+m) [i]for m=1, this implies that diffraction softening should be visible above f:8 etc.

Using this result in the DOF equation gives (1+m) factors cancel:

(DOF )max~ 2CN_nominal_diffraction_limit/m^2

It is convenient to express magnification as field_width divided by sensor_width because that allow us to write things in a convenient, non dimensional form:

(Depth_Of_Field/Width_Of_Field)max ~ 2CN_nominal/(Width_of_Sensor *m)

For a 1.5 crop sensor this is about:

(DoF/WoF)max = N_nominal_diffraction_limit/630m or about 0.025/m, ie 2.5%/m

Dave
EDIT this is an updated version. The original was off by a factor of m.

This result implies that when diffraction softening is taken into account, maximum useful field depth as a fraction of field width varies inversely with magnification.

Last edited by newarts; 01-16-2011 at 06:10 PM.
01-16-2011, 03:20 PM   #26
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QuoteOriginally posted by newarts Quote
I don't see the fine parallel laser machining marks you mentioned. Were they present in this part?

In what ways is this photo better than those taken with other setups? Enlargement? Contrast/sharpness? I'm wondering what directions you'd like to see improvement.
Name:  CutLines.jpg
Views: 504
Size:  44.1 KB

I have circled the cut lines in the photo. You don't see them in the point cut because the laser is moving in 4 axes simultaneously and that blurs the lines.

The tube in this photo is 1/3 the diameter of the tube photo in my post. So the enlargement is much better and finer details of the cut are becoming apparent. In the original post the focus is softer and the lines don't come through.

It's not fair to you guys as I know what I'm looking for and you don't but I really appreciate the technical photography help.

Where do I want to go from here?

I'd like to take this photo and with setup, lighting and PP maximize the resolution and sharpness. If I can accomplish that I would have 90% of all I could ask for.
01-16-2011, 04:06 PM   #27
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I think you'd want to figure out where the dust spots in the centre of the frame are coming from, and the "soft glow" in that area as well... though perhaps the latter could be improved with more DOF?
01-16-2011, 04:24 PM   #28
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Had a bit more thought about this -
because you are dealing with very small objects
then depth of field for scanning may not be such an issue.

As mentioned I have a cheapo (and I mean cheap @$32 from WalMart) Canon Pixma MP250 all-in-one printer/scanner -
that uses the cheapest CIS technology with LED lighting -
as far as I am concerned the worst of both worlds -
BUT I scanned a couple of needles at the full 600dpi scanning resolution -
without any concerns about the usual focus, lighting, exposure, apertures, tripods -
I just scanned at default settings (literally as I was composing this post) and got:



This is at the very bottom end of the budget for scanners.
As I have mentioned there are scanners that can do 4800dpi
which is 8x higher linear magnification than this result I got.

The DoF is narrow, note the backing paper is OOF -
but the DoF seems adequate for the needle.......

Last edited by UnknownVT; 01-16-2011 at 04:34 PM.
01-16-2011, 04:27 PM   #29
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QuoteOriginally posted by UnknownVT Quote
Had a bit more thought about this -
because you are dealing with very small objects
then depth of field for scanning may not be such an issue.
This is at the very bottom end of the budget for scanners. As I have mentioned there are scanners that can do 4800dpi which is 6x high magnification than this result I got.
OK, you convinced me. I'll try my scanner. Truth be told, it just doesn't feel like photography but it may very well be the best solution to my technical issues.
01-16-2011, 04:44 PM   #30
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QuoteOriginally posted by joelovotti Quote
OK, you convinced me. I'll try my scanner. Truth be told, it just doesn't feel like photography but it may very well be the best solution to my technical issues.
I know - but I have thousands of photos of knives, flashlights and associated small objects, all done with the scanner in my reviews over the years - then I blew up my old HP ScanJet 2100C cheapo scanner - and just could not find one to be able to replace it - that's why I gave the long tedious dissertation previously about DoF - but watching your examples and finally getting it through my thick head DoF probably is not a problem if the tiny object is in contact with the glass platen - viola! - it'd be easy to scan the object - I mean even a 4800dpi CanoScan LiDE210 is only $89 retail, which has to be cheaper than any lens or digicam......
The CanoScan 9000F is about $160 street and that does 9600dpi 16x linear magnification of my scan.
BUT if you're buying then try it first to make sure the results are satisfactory (practice on you existing scanner)

and since you already have a scanner - why not try it - my scan took me less than 5 minutes including cropping and posting to PhotoBucket - probably it's taking me longer to type this!

Creativity is limited only by one's imagination -
eg: try different orientation (as the light either leads or trails the scanning element so you know the direction of lighting - cross lighting obviously emphasizes the details - that's why to be on the safe side I scanned on the diagonal - backing is also limited only by imagination - leave the scanner lid open and lights off - to get deep black background - and one can always add whatever background via the editor....... I think you get the picture.

Last edited by UnknownVT; 01-16-2011 at 04:53 PM.
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