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 < Techniques > Zeiss  'Mikropolychromar'


Colorless objects are difficult for a microscopist as they exhibit little contrast and are therefore barely visible. The usual procedure is to chemically stain such objects, but this can be tedious and time consuming. Also, these stains do not always produce the desired color contrast and inevitably interfere with the structure of, including killing micro-organisms, any specimen under observation.

For such colorless objects the Zeiss Mikropolychromar provided a means of "staining" them, not chemically but optically. This optical staining has the effect of showing an otherwise colorless object brightly illuminated in one color (for example red) on a differently colored background (blue), as shown here.
With reference to the Mikropolychromar optical path diagram :
  Optical paths for the Mikropolychromar

  Ref:  Carl Zeiss publication O.XI.33
          ( www.science-info.net )
1.   Aperture diaphragm, with lever, for marginal rays (12)

2a. Aperture diaphragm for axial rays (11)

2.  Lever for adjusting diaphragm (2a)

3.  Auxilliary diaphragm with lever, for adjusting only the intensity of the axial rays (11).

4.  Colorless protective glass, which absorbs heat radiation

5.  Special frosted glass which destroys the image of the aperture (3) by scattering and also absorbs UV light which is harmful to the eyes

6.  Interchangeable colored glass ring which causes the marginal rays, and with them the object, to appear colored (red).

7.  Interchangeable color filter, which colors the axial rays (blue) of the illuminating beam differently from 6., and so causes the background against which the object is seen at the microscope ocular to appear of a different color from the object itself.

 8. Head, so that the filter assembly can be swung out sideways for convenience while changing filters (6) and (7). Further, a small displacement of the filter assembly to a slightly eccentric position effects a transition to an oblique semi-bright, semi-dark field illumination.

 9. Arrangement which permits rotation of the whole apparatus about the optic axis and which is used in conjunction with azimuth stops for the observation of directional effects.

10. Aplanatic condenser NA 1.4 into which the apparatus is fitted.

11. Axial rays for tinting the field of view (blue) by transmitted light

12. Marginal rays for the darkfield illumination of the object in a contrasting color (red)

The special feature of the Mikropolychromar is its universal adaptablity. An object can be examined in any one of
the following illumination modes:
  - in any desired color on a differently colored background
  - colored on a colorless background
  - colored on a black background
  - oblique semi-bright
  - oblique semi-dark
  - normal bright field

It is remarkable that all of these different modes of illumination are combined into a single apparatus, with easy interchange between modes during microscopical observation.

Unfortunately, it has not been in production for many years and is rarely seen by a modern day microscopist. A less complex Rheinberg illumination scheme (see below) is now used with customized color filters having a wide variety of illumination patterns.

Only the Leitz Heine phase condenser can be compared with the Mikropolychromar in terms of illumination flexibility. This condenser was the subject of an extensive  Microscope Group discussion  (2004)




The Zeiss Mikropolychromar, in conjunction with an aplanatic condenser, is described as a unique implementation of Rheinberg illumination (optical staining) on the Olympus website - along with a Java-based interactive demonstration.

For low contrast micro-organisms in their natural state, here are some high quality  images  obtained with Rheinberg illumination.