Chapter 3 Detailed Explanation
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3.5 Focusing
Operations
3.5.1 Focusing on a Specimen
This procedure is to operate the fine and coarse focus
knobs to raise and lower the stage so that the specimen to
be observed can be seen most clearly.
The UP and DOWN indications on the sides of the
microscope base indicate the direction in which the stage
moves by rotation of the focus knobs. For both the fine and
coarse focus knobs, turning in the UP direction raises the
stage, and turning in the DOWN direction lowers the stage.
Fine scale
One rotation of the fine focus knob moves the stage
vertically by 0.2 mm. Fine tick marks are placed at 2-
μ
m
intervals of stage travel.
Standard procedure
(1) Swing the 10x (or 4x) objective into the optical
path.
(2) Rotate the coarse focus knob to raise the stage to
its upper limit.
Since the working distances of 4x and 10x objectives
are long, these objectives do not touch the specimen
even when the stage is raised to its upper limit
provided that the slide and coverglasses of a
standard thickness are used. (The standard
thickness for slide is 1.2 mm and that for coverglass
is 0.17 mm.)
(3) While looking into the eyepiece, slowly turn the
coarse focus knob to lower the stage. When you
find a position where the specimen is roughly in
focus, let go of the coarse focus knob.
When rotating the coarse focus knob while
looking into the eyepiece, be sure to rotate it in
the direction that lowers the stage.
When the focal point cannot be found
To find the focal point, rotate the stage vertical
movement stopper counterclockwise to unlock the
limit.
(4) Rotate the fine focus knob and precisely focus on
the image.
Left side
Right side
Fine scale
UP/DOWN marks
