Olympus CHA Buku Petunjuk - Halaman 11

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F. Aperture Iris Diaphragm

An aperture iris diaphragm is provided on the condenser,

the opening of which can be adjusted to match with the

numerical aperture of the objective in use, in order to

70-80%

achieve optimum objective performance, as depth of

focus, image contrast and resolution.

However, since microscopic specimens generally are low

in contrast, their image lacks contrast jf the objective is

used with its full numerical aperture. Therefore, it is

often preferable to stop down the aperture diaphragm

slightly more than indicated by the objective N.A. An

aperture setting at 70% to 80% of the objective N.A. is recommended. If necessary, remove

the eyepiece and, looking at the exit pupil of the objective, adjust the opening of the

diaphragm.

G. Immersion Objectives

To utilize the full numerical aperture of an immersion objective (with engraving "HI" for

homogeneous immersion). the objective, specimen and condenser are immersed in an immer-

sion oil.

Care should be taken to prevent oil bubbles from forming in the oil film between condenser,

specimen sl ide or objective.

After use, carefully wipe off the immersion oil deposited on the lens surfaces

with gauze moistened with xylene.

Never leave oil on lens surfaces after use as oil remnants will seriously impair the

performance of the lens systems. It is recommended to use Olympus immersion

oil for immersion objectives.