B&K Precision 1253 - Manual - Manual (Page 22)

14: Overscan-Bounce (Regulate)
Description: Sometimes called "Regulate", this pattern consists or 4 horizontal and vertical lines at the
edges of the screen, marking 2.5%, 5%, 7.5% and 10% of the width and height of the screen. The center
of the screen flashes between full white and black every 1 1/3 seconds.
Pattern Usage:
Used to test the amount of overscan of a monitor (usually a CRT type), and to check the regulation of a
CRT monitor's high-voltage and deflection power supply circuits. The pattern alternately produces
maximum and minimum CRT beam current. Ideally, these current extremes should not cause the picture
size to change. This can be judged by observing how much the line moves.
A one to two pixel shift is not noticeable in most picture material to a typical viewer.
Also used to check and adjust for the proper geometry of a display, including picture centering, size,
trapezoid (keystone) correction, pincushion (bow) correction, and linearity. The 4 lines at each of the four
edges make it particularly easy to see whether there is equal amount of overscan at the sides or at the top
and bottom of the pattern.
The horizontal and vertical size controls should then be adjusted for the desired amount of either overscan
or underscan. If overscan is desired, a display should usually be adjusted for slightly less than 5%
overscan. The horizontal and vertical overscan should be adjusted to be an equal percentage, as judged by
the overscan percentage lines.
Trapezoid correction control(s) should be adjusted to make the pattern’s edges parallel to the edges of the
display screen. Pincushion correction controls should be adjusted to straighten the lines on the edge of the
display. Use the edge of the display screen or a flexible straightedge, such as a yardstick, to judge the
straightness of the lines.
Examples of Uncalibrated Displays: The following image indicates a TV having too much overscan.
Only 2 of the four lines are visible at the edges of the screen, indicating an overscan of between 5% and
7.5%.