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00050_Field_50.txt
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1997-10-29
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CALIBRATION OF THE VISUAL ACUITY CHART
If the size of the projected chart is
incorrect, the projector must be
adjusted. The procedure may vary
depending on the type of projector
used. The following is the procedure
for the most common projector.
The tube on the front of the projector
has 2 sleeves. They are held in place
by set screws. To adjust, loosen the
screws. Sliding the outer tube in and
out changes the size of the projected
letters while the inner tube focuses
the letters. With one person holding
the calibration letter (or mm rule) on
the 20/200 (6/60) letter on the chart, the
second individual varies the letter size
(then refocus) by adjusting the tubes
until the projected letter is the correct
size and in focus. Once correctly
adjusted, retighten the screws.