Re: Köhler illumination question...

Hi Gregor,

Yes the my M420 has the Leica barnd mark.

Aaron

On Mon, 02 May 2005 05:42:05 GMT, "GTO" <gregor_o@xxxxxxxxxxxxxxx>
wrote:

>Hello, Aaron:
>
>Thanks for the more detailed explanation. I first thought that the
>"uncolored glass" filter you mentioned was actually just a regular filter
>and not something that appears to the eye like the one depicted in
>etched.jpg. - Quite remarkable microscopic difference at 60x magnification,
>I must say.
>
>The Wild M420 is a truly magnificent photomacroscope. I remember when you
>purchased this one. BTW, is it now known as a Leica M420?
>
>Gregor
>
>"Aaron" <nghy@xxxxxxxxxxx> wrote in message
>news:v74b71pbhdca47j00sgk0cgmnolkfo9oev@xxxxxxxxxx
>> Hi Gregor,
>>
>> Both "etched.jpg" and "other.jpg" were recorded with a Nikon Coolpix
>> 5000 mounted on a Leica M420 with a 2X suplemental objective. I used
>> oblique incident illumination from a single fiber optic cable. The
>> nominal magnification at the camera is about 60X. but that is not
>> valid once it is displayed on a computer screen.
>>
>> The point is that both of these "filters" appear similar to the eye;
>> what we describe as "frosted filters". I agree that the surface of
>> the "fliter" ought to have bearing on the character of the lighting.
>>
>> Etched.jpg is the image of the element just in front of the halogen
>> lamp in the Zeiss 100W lamphouse. This is the element that is swung
>> into place after the procedure for Kohler illumination is performed.
>>
>> Other.jpg is an image of a 32mm filter that might be placed in the
>> well over the field diaphragm or in a filter tray below the condenser
>> on a Zeiss Standard series microscope.
>>
>> I have since located some ground surface filters and a sandblasted
>> glass slide. These are different still. I will try to collect some
>> more examples. I have much more sophisticated equipment to examing
>> the surfaces. If this becomes a matter of greater curiosity I may
>> image these and post them.
>>
>> Aaron
>>
>> On Mon, 02 May 2005 01:23:54 GMT, "GTO" <gregor_o@xxxxxxxxxxxxxxx>
>> wrote:
>>
>>>Hello, Aaron:
>>>
>>>Thanks a lot for these images. This is really interesting stuff!
>>>
>>>Your image from an uncolored glass filter reminds me of investigations of
>>>amorphous materials with AFM (such as amorphous metals). The features on
>>>this glass filter might be so small that their impact is negligible for
>>>light microscopy applications.
>>>
>>>However these structures of approx 0.01-0.05 mm in diameter on the element
>>>in your 100W Zeiss lamp most certainly impact the light that passes
>>>through
>>>them. What is the technique you used to obtain this very informative
>>>image?
>>>
>>>Great work! I think that we just started to find an interesting aspect,
>>>which is very important for the implementation of a well working
>>>illumination.
>>>
>>>We most certainly should more clearly define "frosted" vs. "edged" vs.
>>>other
>>>surface treatments that might appear like "frosted".
>>>
>>>What would be interesting to see, is an image of a frosted glass.
>>>
>>>Thanks,
>>>
>>>Gregor
>>>
>>>
>>>"Aaron" <nghy@xxxxxxxxxxx> wrote in message
>>>news:qlna71p6ema6tb9cg2poa5c0345q7hp0qc@xxxxxxxxxx
>>>> Hi Gregor,
>>>>
>>>> It sure looks like it. I just posted a response to Klaus which I will
>>>> tag on here so you don't have to hunt for it.
>>>>
>>>> Hello Klaus and friends,
>>>>
>>>> The minute I read your post, I could not wait to see the "frosted
>>>> element" under magnification.. Indeed I found things as you said.
>>>> I started to look at other Zeiss filters. They are not what might be
>>>> expected either. We need to review and define the terms "diffuser"
>>>> and "frosted element".
>>>>
>>>> The "element" in the Zeiss 100W lamp house has the little lenses
>>>> etched into the surface. These are approx 0.01-0.05 mm in diameter
>>>>
>>>> http://home.comcast.net/~nghy/mywebpages/test/etched.jpg
>>>>
>>>> In comparison I imaged an "uncolored glass" filter. The pattern has
>>>> recular undulations, minute bubbles and wrinkles. Toatally
>>>> unexpected.
>>>>
>>>> http://home.comcast.net/~nghy//mywebpages/test/other.jpg
>>>>
>>>> I expected to see something similar to the sand blasted edge found on
>>>> slides that have a random faceted appearance.
>>>>
>>>> Aaron
>>>>
>>>>
>>>>
>>>>
>>>> On Sun, 01 May 2005 05:28:57 GMT, "GTO" <gregor_o@xxxxxxxxxxxxxxx>
>>>> wrote:
>>>>
>>>>>Einen schönen guten Morgen!
>>>>>
>>>>>
>>>>>
>>>>>Excellent point! This could explain some new designs that are recently
>>>>>sold.
>>>>>One example is the fly-eye optics design by Nikon (see Eclipse 80i),
>>>>>which
>>>>>are used to ensure even illumination.
>>>>>
>>>>>
>>>>>
>>>>>I just looked at the Leitz Ortholux lens in the illuminator, and
>>>>>although
>>>>>it
>>>>>looks like a "frosted" lens at first sight, it is possible that also
>>>>>Leitz
>>>>>created the mat surface using a similar process (?). How big are these
>>>>>bowl-like concave hollows in the lens-surface?
>>>>>
>>>>>
>>>>>
>>>>>Nette Grüsse aus Kalifornien,
>>>>>
>>>>>
>>>>>
>>>>>Gregor
>>>>>
>>>>>
>>>>>
>>>>>...
>>>>>> reading your qestions to Andy Resnick and earlier contributions in
>>>>>> this thread, it seems to me, the term "frosted" does not take into
>>>>>> account properly, that the first lens-surface of some Zeiss
>>>>>> lamp-collectors ist not ground. Its mat surface is achieved by
>>>>>> hydrofluoric acid, which leaves thousands of little bowl-like concave
>>>>>> hollows in the lens-surface. They are of different diameters, but all
>>>>>> of the same focus-width - tiny concave lenses on the surface of a
>>>>>> concave lens.
>>>>>>
>>>>>> The result is, that light-rays are not being scattered in all
>>>>>> directions, as would be the result of a simple ground glass, but the
>>>>>> light beams entering the first collector lens, are just "widened" and
>>>>>> defocussed, changing the image of the lamp filament into a homogeneous
>>>>>> image, mixed together out of thousands of little lenses. This design
>>>>>> does not fully destroy the definition of the field diaphragm.
>>>>>>
>>>>>> Frosted in that special way the lighting force is reduced about
>>>>>> 20-40%; that is not much, compared with reduction of 60-80% through a
>>>>>> normal ground glass.
>>>>>>
>>>>>...
>>>>>
>>>>
>>>
>>
>

.

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