Nomarski Differential Interference Contrast
adapted to a
Bausch & Lomb Research (I) metallograph
by George Langford

Cast iron - 25X Reichert objective in B&L Research I metallograph
Cast iron,unetched microstructure of graphite flakes in a ferrite matrix.

Reichert Nomarski DIC attachment on a Bausch & Lomb Research I metallograph, 25X Reichert objective, 4X Zeiss projection eyepiece, green interference filter, greyscale image; Leaf DCB-II digital back on Hasselblad 500 EC/M camera, image saved in 16-bit format and
processed with Adobe PhotoShop Elements in a WinXP laptop.  Mac PowerPC operating system runs the Leaf DCB-II.  Right click on image and select View Image to see it at 2048 by 2048 bit resolution.

The shutter on the Hasselblad doesn't trip reliably, so I used a time exposure initiated manually after starting the exposure with the Leaf Systems software and then opening a Compur shutter that's situated in the filter holders ahead of the aperture diaphragm.  This three-step sequence works OK about fifty percent of the time.  No film was wasted ...

Focus is by viewing the aerial image inside the 45-degree viewfinder of the single-lens-reflex Hasselblad camera body.  Without any ground glass, all that can be viewed is the central portion of the aerial image, and that only by holding one's eye about six inches above the lens of the viewing prism.  The image is crystal clear and can be made critically sharp as though viewed through the metallograph's eyepieces.
Cast iron 40X objective, Nomarski DIC
As above, but using a Reichert 40X objective.

The camera hasn't yet been centered exactly; my setup does permit centering as well as changing the bellows draw of the oprtical bench of the Research I metallograph.

The Leaf DCB-II digital back dates from around 1995 and originallu cost upwards of five figures in 1995 dollars.  It was obtained from its original owner, a New York professional photogapher, at less than 1/100th of the original cost.

The light source is a less-than-1-watt white light-emitting diode disigned as a replacement bulb for two-to-six-cell flashlights.  Exposure times were 1/5th to 1/2 second even with the green interference filter.  I made the condensing setup myself from a 20mm focal length Anchor Optics duoble-convex lens located close enough to the LED to bring an enlarged image of the LED die onto the aperture diaphragm of the metallograph.  Illumination is easily adjusted to be quite uniform, much more easily than with the metallograph's original 100 watt incandescent bulb.

The Leaf DCB-II has 14 bits of dynamic resolution.  One can see the result at left: The microstructure of the graphite flakes is seen just as clearly as microstructural details on the spectrally reflecting surface of the ferrite.  The gretscale image is just as detailed as what can be seen through the microscope's eyepieces.

The image is sized to just cover the 31mm square CCD sensor of the digital back, so one can see some image degredation at the extreme lower right corner of the field. here limited by the internal optics of the metallograph.

Comparison of the two images will reveal a large number of dust particles on the uncleaned image sensor.