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Objective lenses may have slight magnification
errors. A stage micrometer is used to check these
errors in advance, so that microscope measurements can
be corrected more precisely.
Example of Magnification Error Measurement for Objective
Lenses
-
Position the micrometers so that the ocular and stage
micrometer scales appear parallel when viewed through
the eyepiece. This allows for precise magnification
error calculation.
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The figure below shows an example using a
stage micrometer NOB1
(1 mm / 100 div / pitch = 10 μm) and an
ocular micrometer S11
(10 mm / 100 div / pitch = 100 μm) under a
20x objective lens.
[Expected Measurement]
If the magnification
is accurate,
10 pitches
on the stage micrometer
should match
20 pitches
on the ocular micrometer:
2000 μm = 10 μm (1 pitch of stage micrometer) × 10
pitches × 20x objective
[Observed Measurement]
However,
as seen in this example, if the ocular micrometer reads
21 pitches
instead of
20, the actual magnification is slightly higher than 20x,
indicating a magnification error.
[Correcting Measurement Values]
To obtain more accurate measurements, multiply
the ocular micrometer reading by the error correction
factor:
0.95 (= 20 ÷ 21).
Thus, the actual measurement value = ocular
micrometer reading × 0.95,
ensuring more precise
results.
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