Leica DM IRB manual Operation of phase contrast, Phase contrast observation

Operation of phase contrast

Phase contrast observation

Like transmitted light darkfield and transmitted light interference contrast, phase contrast is used to produce high-contrast images of un- stained specimens.

Setting phase contrast with condenser 0.30 S70

Phase contrast observation is possible with ob- jective magnifications from 5x to 40x.

Turn a phase contrast objective (engraving e. g. PH2) of the lowest magnification into the light path and focus the specimen. If it is difficult to find the focal plane: temporarily narrow the aperture diaphragm or use a stained specimen and switch the disc to pos. H (= brightfield).

Set the light ring (64.2) in the condenser disc that corresponds to the objective engraving (PH2). Open the aperture diaphragm (= pos. PH). Move the Bertrand lens into the light path = pos. B by turning the knurled knob and focus the annular structures with the lever (Fig. 64).

Insert the two supplied centring keys into the openings of the disc on the left and right of the label plate (e.g. 3) (Fig. 64.2) and turn them until the dark ring (phase ring in the objective) coincides with the slightly narrower ring (light ring in condenser).

Then repeat the centration process for the other objective/light ring combinations. Disengage the Bertrand lens, pos. 1x.

Fig.Ê 63ÊCentrationÊ for phase contrast, viewing with a Bertrand lensÊ

a Condenser in brightfield position (H), b Condenser in PH position, light ring LR not centred, c Light ring and phase ring centred

Fig.Ê 64ÊCentrationÊ process for phase contrast/DF 1 Centring keys in working position, 2 Disc

2

1 1

74