Quantum Data 881 User Manual page 954

LinFocus
Description
Test
Method
Test
Appendix B Image Reference
926
marks and a ruler or gauge to measure linearity over a small portion of the display.
Compare the number of tic marks per unit of measure with an adjacent or overlapping
area.
This image has several parts. The first part consists of a large circle in the center of the
screen. Its diameter equals the lesser of the video height or width of the display.
The second part is a 10x10 box crosshatch. The crosshatch is drawn in from the outside
edges, with any extra pixels in the boxes placed along the vertical and horizontal axis. The
vertical centerline is two pixels thick if the format has an even number of active pixels per
line. The horizontal centerline is two pixels thick if the format has an even number of active
lines per frame. A smaller box is added at the center of the image. The box is one-half the
height and two-fifths the width of one of the crosshatch boxes. Current format data is
shown in the lower left quadrant of the image. It shows the number of active pixels (H) and
lines (V) as well as the vertical and horizontal scan rates.
The primary version (shown below) consists of a white pattern on a black background. The
secondary version has a black pattern on a white background.
The image also includes blocks of focus-checking characters at various locations. The
blocks are positioned inside the crosshatch boxes and are up to 3x3 characters in size.
The size of the blocks is limited by the number of characters that can fit in one box.
Linearity adjustment
Please see the Linearity test image on
on measuring linearity.
Focus adjustment
"Linearty (Linearity)" on page 925 for information