Nikon DIC microscope problem

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Walter Piorkowski
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Joined: Mon Aug 14, 2006 6:42 pm
Location: South Beloit, Ill

Nikon DIC microscope problem

Post by Walter Piorkowski »

DIC Microscope Problem

I am using old 1970’s vintage black body Nikon S microscopes. Specifically the model L-KE and a later S-Kt. Nikon made available for these instruments a large variety of accessories including part number 76990 a Differential Interference Attachment Type T for transmitted light. This makes my microscope a DIC instrument. The design is not based on the Wollaston or Nomarski prism but on a device called a Savart plate. The light shearing principle of the modern DIC instruments is accomplished by 3 Savart plates each made special for 10, 20 and 40X objectives and housed in a turret under the condenser. As with the newer designs a polarizer and analyzer are used and a second Savart plate above the objective realigns the sheared light and is translatable to very the fringe color of the DIC affect.

When I purchased the unit off an eBay auction in Japan, the seller acknowledged that an auxiliary lens supplied with the attachment was missing. This would set atop the microscopes field lens and we surmised that it helped to concentrate or focus a brighter light into the DIC turret. The seller claimed to never having the lens himself and used the attachment successfully himself with all three objective settings. He proved this by sending 3 images by email at all 3 magnifications.

My problem with the attachment is the inability to get a DIC image with the 40X objective optical train. There is no problem with 10X or 20X objectives and their matching plates. In use with these, once the polarizer and analyzer are set to extinction it is a simple matter of getting the condenser turret at the right distance from the subject slide on the stage to create the DIC affect.

With the 40X objective however no point in the range of the condenser travel will produce the DIC affect. What is seen instead is the subject with a series of color bands or fringes superimposed in the same field. This is the same image that is seen when the turret is rotated to its fourth position of no Savart plate, only with less contrast. It is as if the 40X Savart plate has no affect at all. There seems to be no damage to the plate nor is there any sign of tinkering with its axis of rotation. The 40X objective I use is a good quality Unitron strain free achromat.

So my fellow experts, what do you think is wrong? Do you think I am wrong on the purpose and function of the auxiliary lens? Is there anyone else in the forum that owns one of these units? I would love to get this unit working at the higher magnification. The details that the DIC brings out in protozoa are astonishing.

I would also be interested in a discussion on Savart verses Nomarski DIC. The Nikon Microscopy U and Olympus Molecular Expressions data base discuss the Wollaston to Nomarski evolution but nothing about the Savart design. What would have lead Nikon optical engineers to go this route? Is there a difference in affect, manufacturing difficulty etc. Let me have your thoughts.

Walt

Charles Krebs
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Post by Charles Krebs »

Walt... is the 40X the same objective the previous owner used?

I know nothing about savart plates, but I do have an Olympus DIC set-up. I know for certain that I can't assume that, for example, all 10X objectives will work with the 10X prism. Some don't work at all. Even within Olympus brand objectives... the 10X S Plan works well with the prism specified for it, but the 10X D Apo works very poorly with that prism. When I finally located the proper prism for the Olympus D Apo the difference was like night and day. So it may be that even though your system is designated for 10X, 20X, and 40X there may be some significant variation if objectives other than those intended by Nikon are used. Don't know... just a guess.

Walter Piorkowski
Posts: 693
Joined: Mon Aug 14, 2006 6:42 pm
Location: South Beloit, Ill

Post by Walter Piorkowski »

Thank you for your reply Charles, and by the way I am an admirer of your astonishingly sharp photomicrographs. The objective used by the original owner is in Japan unfortunatly. I believe that he was using a Nikon plan achromat but I am not certain. I will respond with him on the chance that your idea of a specific objective type or design is required.

Walt

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