Chapter 4---Optical
19.Retighten the two wing nuts and tighten the two hex nuts.
20.Reset the ILA® biases to their previous levels from Step 2. ILA® Back Focus Adjustment
The ILA® Back Focus adjustment moves the ILA® /Relay Lens/CRT assemblies forward or backward as one unit to focus the ILA® output on the screen. When using a zoom lens this adjustment allows the zoom lens’ tracking to remain focused on the screen throughout the entire zoom range. Use the Focus Pattern (Test Pattern #6) to perform this adjustment one color at a time. The procedures below perform the ILA® Back Focus for the Green lens. The first procedure is for a zoom lens. The second procedure is for a fixed lens.
For best results, perform ILA® Back Focus procedure with two people: One person to stand in front of the screen to observe Spacer Balls and the other to move the ILA® /Relay Lens/CRT assemblies back and forth. This is a
Tools Needed
Parts Needed
No parts are needed
To adjust the ILA® Back Focus for a Zoom Lens:
1.Power the projector ON and allow to stabilize for at least 15 minutes
2.Remove the Rear Cover and tilt up the Electronic Module.
3.Hide Red and Blue. View Green.
4.Select the Focus Pattern (Test Pattern #6).
5.Select Projection Lens from the menu.
6.Use the up/down arrow keys to zoom the Projection Lens to full telephoto position (smallest image).
7.Use left and right arrows to focus the projection lens to get sharply focused spacer balls.
NOTE: Spacer balls separate the layers inside the ILA® Assembly. They are tiny, random, irregularly shaped spots that are visible throughout the image. Stand directly in front of the screen and look in the lighter areas of the image to see the Spacer balls. From throw distances shorter than 4 meters, spacer balls are difficult to see.
8.Zoom the lens to a
9.Loosen the wing nut on the Green Relay Lens (or whichever lens is being focused).
Model 250 Service Manual |
