Olympus BHTU Manuale di istruzioni - Pagina 14

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1. Troubleshooting Guide

Condenser Adjustment

Fig. 14

Fig. 15

Condenser Centration

1) Stop down the field iris diaphragm with

knurled ring

by rotating in the direc-

tion of the arrow. (Fig. 14)

2) Use the condenser height adjustment

knob

to move the condenser up and

down until an image of the field dia-

phragm can be seen clearly in the eye-

pieces. The rotation of the knob in the

direction of the arrow lowers the con-

denser.

Field iris

diaphragm image

Field of view

3) Bring the field iris diaphragm image into the center of the field of view with the two con-

denser centering knobs

®.

(Fig. 14)

4) Widen the diameter of the iris diaphragm progressively. If the polygonal image of the iris

diaphragm becomes inscribed in the field it means that the field diaphragm is centered.

(Fig. 15)

Field Iris Diaphragm

•

The field iris diaphragm controls the diameter of the ray bundle impining on the speci-

men surface and therefore, by stopping down the field diaphragm until it is slightly

larger than the field of view, it can reduce stray light, which in turn increases image defi-

nition and contrast.

70-80%

20 - 30","

Fig. 16

Opening of the

aperture diaphragm

Objective exit pupil

Aperture Iris Diaphragm

•

In order to achieve opTimum objective performance, the opening of the aperture iris

diaphragm should be matched to the numerical aperture of the objective in use. It is

often preferable, however, to stop down the aperture diaphragm slightly more than in-

dicated by the objective N.A. This will result in better image contrast, increased depth of

focus and a flatter field.

•

After completing focus adjustment, re-

move one of the eyepieces from the ob-

servation tube and look into the empty

eyepiece tube.

As you stop down the

aperture iris diaphragm, the image of the

iris diaphragm can be seen in the object-

ive pupil.

Adjust the opening of the

diaphragm to match the N.A. of the ob-

jective in use. If the specimen is low in

contrast, it is recommended to stop down

70% - 80%

of the objective N.A. (Fig.

161