Convergence Error (Red Is Misaligned); Convergence Adjustment - Barco Galaxy NH-12 Installation Manual

3. Engine replacement
3.4.5

Convergence adjustment

Overview
• Introduction
• Convergence controls of the red channel
• Convergence controls of the green channel
• Adjusting the convergence
• Example of convergence correction
3.4.5.1 Introduction
Convergence
An image is split into its three main colors: a red image, a green image and a blue image. Each main-color-image is
visualized by a separate DMD. This means that the red content of the image is visualized by the red DMD, the green
content by the green DMD and the blue content by the blue DMD. Each of these main-color-images must precisely
coincide on the screen to come to a good representation of the image. A main-color-image (e.g. the one with the green
content) not matching the position of the other two (e.g. red and blue) is called a convergence error. A convergence
error is visible on the full projected image.
What will be seen in case of a convergence error?
If the red formatter board (and thus the red DMD) is not well aligned and a white figure (e.g. the outline of a square with line thickness
= 1 pixel) is projected, the red part of this figure will be projected next to the green and the blue part of it. Instead of seeing the white
lines, cyan ones and red ones can be distinguished.
Image 3-75

Convergence error (red is misaligned)

Useful internal patterns
Various internal patterns are very useful to check the convergence. They can be accessed through the OSD:
• convergence pattern: red on blue
• convergence pattern: green on blue
• convergence pattern: red on green
• hatch pattern
Principle of adjusting the convergence
By slightly moving the position of the formatter boards, a convergence error can be corrected. Three adjustment points are available
on the mounting plate to which the formatter board is fixed, allowing to do some basic movements. By default, the convergence is
adjusted in the factory is the position of each formatter is secured by four screws.
Reference
Since the blue formatter board and its mounting plate are not accessible, the blue image is used as a reference. To correct for any
convergence error, the red image is aligned on the blue one first. In a next step, the green image is aligned to the blue one.
3.4.5.2 Convergence controls of the red channel
Securing screws
Prior to adjusting the position of the formatter, four securing screws must be released! The location of the screws can be seen in
the image below.
38 R59770591 ENGINE KIT 26/08/2010