2.Mounting the Eyepieces
For mounting, simply drop the eyepiece into the eyepiece tube. It is recommended to leave an eyepiece in place even when it is not in use, in order to prevent the entrance of dust into the eyepiece tube. Or put on the eyepiece cap in place of the eyepiece removed.The inclined eyepiece body tube, trinocular, bino- cular or monocular,can be rotated after loosen- ing the clamp screw (Fig. 6) for conveni- ence in viewing from any desired direction without moving the
microscope stand. By further releasing the clamp screw the body tube can be removed and replaced with another type eyepiece body tube.
3.IVIounting the Condenser
To mount the condenser, unlock the lock screw, and insert the condenser beneath the condenser
holder as far as it will go. Then, tighten the lock screw. In this case locate the dia- phragm eccentering lever and its screw at a proper place so as to facilitate their manipulation with one hand (Fig. 7). The correct distance to re- tain immersion oil be- tween the lower sur- face of the slide and the top of condenser is secured when the
condenser is raised to the upper limit by turning the condenser focusing knob.
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ILLUMINATION
Resolution and contrast of image are greatly affected by the method of illumination.
1.Condenser Iris Diaphragm and Images
Stop down the condenser iris diaphragm and slide it in the radial direc- tion from center to edge. The farther the iris diaphragm is
(Fig. 8, a, b).
(a) Central illumination (b) Oblique illumination (c) Dark field illumination
When the iris diaphragm is positioned so as to let the light bundle enter into the object at an angle o'f incidence the same as the aperture angle of the objective the resolution reaches maximum and twice as much as the resolution by central illumination.
If the diaphragm is further eccentered to such an extent as not to introduce the light bundle directly into the objective, dark field illumi- nation will be obtained. If the iris diaphragm is widely opened, images by various angle illuminations are integrated. An illumination angle not favorable for the object may be included.
In the central illumination the maximum resolution is obtained when the opening of the iris diaphragm just corresponds to the aperture angle of the objective. In this case excessive outer rays to be used as dark field illumination are cut off and flare is minimized. If the opening is made smaller, the contrast is enhanced, though the resolution is lowered. But if the iris diaphragm is large enough to cover 6 0 - 7 0 % of the objective aperture, the decrease of resolution will not be remarkable.
If the diaphragm is stopped down to minimum for admitting only very
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