Model 335 Supplement 9
Figure 1. Model 335 Xenon Arc Lamp Housing Assembly (Lamphouse)
3. Verify that the condensing (collimating) lens assembly has not
moved (see Figure 2-2 in the Series 300 Operator’s Manual).
Check to see if the assembly is loose. It should be unmovable in
any direction. The barrel of the lens assembly should be no more
than 1 1/2 inches (usually much closer) from the blue dichroic
mirror. If it needs to be moved closer, first loosen the 3mm set
screw located at the top of the mounting ring that the barrel sets
in, then move the lens closer to the blue dichroic mirror. This will
increase the center brightness but the roll-off may not be
acceptable if the barrel is moved too far forward. Roll-off is the
gradual difference in brightness on the screen from the center to
the edges.
NOTE ON ROLL-OFF: In these illumination optics (arc lamp and
condensing lens) adjustments, be careful to maintain proper roll-
off. It is possible to get very high brightness values at the screen
center at the expense of proper roll-off. Try to keep the ratio
between center brightness and edge brightness at no more than
2:1 (e.g. if the center brightness is 20 foot-candles, the edge
brightness should be at least 10 foot-candles). Use a light meter
to determine if the roll-off is appropriate.