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Author Topic: Leica FSC coaxial illumination  (Read 28729 times)

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Jerryp

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Leica FSC coaxial illumination
« on: May 24, 2007, 10:35:30 PM »
At our lab we have been using our new Leica FSC for about a month now. We ordered it with 4 different lighting options.   One of the lighting options that tend to draw controversy is the “coaxial” lighting feature. The controversy comes when considering the cost of the feature and how useful it is.  (It’s expensive)

The coaxial feature generates illumination through the objective lens so it illuminates the specimen at a 90 degree angle (unlike oblique lighting that illuminates from 1 to 89 degree angle). Additionally, with the use of polarizing filters and ¼ wave plates the light can be circularly polarized ( as opposed to linear polarized). Manipulation of the polarizing filters allows the user to adjust for brightness and glare.  This illumination feature and filters are best utilized when viewing firing pin impressions.

Gerard Dutton published two articles in the AFTE journal regarding the Leica comparison microscope in which he commented on the coaxial lighting feature.

I have attached some images of a firing pin impression from a Smith and Wesson model 29 in 44 mag seen with both oblique and coaxial illumination at 10X and 60X.

Assuming there were insufficient breech and chamber marks for identification, would you make an identification based on the firing pin and did the images created using the coaxial illumination feature factor in to your decision.

Thanks in advance for your replies

« Last Edit: May 24, 2007, 10:39:16 PM by Jerry Petillo »

Offline Erik Brown

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Re: Leica FSC coaxial illumination
« Reply #1 on: May 25, 2007, 01:36:05 AM »
Assuming there were insufficient breech and chamber marks for identification, would you make an identification based on the firing pin and did the images created using the coaxial illumination feature factor in to your decision.

I had this scenario come up in a couple of different NIBIN verification cases.  The breechface, ejector, extractor, and chamber marks weren't cutting it.  But the firing pin impression with the coaxial illumination with the wave plates had sufficient reproducible detail for an identification (which was second chaired).

It doesn't happen often, and I find the coaxial lighting setup on the FSC a little cumbersome, but it can help in some cases.

Jerryp

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Re: Leica FSC coaxial illumination
« Reply #2 on: May 25, 2007, 10:38:03 AM »
Thanks Erik.


Offline Mitch Rector

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Re: Leica FSC coaxial illumination
« Reply #3 on: May 25, 2007, 01:53:16 PM »
I have found it to be useful our our Leeds 'scope.
Mitch Rector
Tuscaloosa Police Department
3801 Trevor Phillips Avenue
Tuscaloosa, Alabama  35401

Online Cole

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Re: Leica FSC coaxial illumination
« Reply #4 on: May 25, 2007, 02:01:19 PM »
We have it on one of ours.  Haven't yet been able to get it to do anything worthwhile.
The views expressed here do not necessarily reflect the views of anyone, anywhere, ever - including the author.

Jerryp

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Re: Leica FSC coaxial illumination
« Reply #5 on: May 25, 2007, 03:00:36 PM »
Thanks for your replies

Offline Michelle Dilbeck

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Re: Leica FSC coaxial illumination
« Reply #6 on: May 25, 2007, 03:05:31 PM »
I've found coaxial lighting very useful on our DMCs.  And easy to use.  Flip a switch for each side and VOILA!   :)
Alameda County Sheriff's Office Crime Laboratory

Jerryp

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Re: Leica FSC coaxial illumination
« Reply #7 on: May 25, 2007, 03:27:51 PM »
The light source that we use for the coaxial feature is shared with our cold light source. I have to remove the fiber optic cord from the cold light source and put it in the coaxial adapter. it takes about 20 seconds.


Offline Erik Brown

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Re: Leica FSC coaxial illumination
« Reply #8 on: May 25, 2007, 05:11:30 PM »
I've found coaxial lighting very useful on our DMCs.  And easy to use.  Flip a switch for each side and VOILA!   :)

The set up on the DMC is much better than the FSC, for the reason Jerry posted above.  Also when the fiber optic cord was inserted into the coaxial adapter, I found that the cords had to be "jiggled" to get them to point straight down into the firing pin impression, or they would sometimes be out of the field of view at higher magnifications.

 

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