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.