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4-38 Chapter 4: Built-In Images
Model 801GC, 801GF & 801GX¥Rev. X1
Linearty (Linearity) — contd.
Test Linearity adjustment
Purpose In order to present an undistorted display, the
horizontal and vertical sweeps of the electron beam
across the face of the CRT should be at uniform
speeds. Any non-uniformity in the sweep causes
portions of an image to stretch while other portions
are compressed. Non-linearity in a monitor shows
up in several ways. It may be present across the
entire screen, in a large portion of the screen, or
localized in a very small area.
Method The circles in the image can be used to do a ball
park adjustment of a monitor’s linearity controls.
Adjust the controls to form perfectly round circles.
The crosshatch image can be used to measure
linearity and to make finer control adjustments.
All the full boxes in the crosshatch should be
identical in size. Measure them with a ruler or a
gauge made for the monitor you’re testing. Any
deviation should be within your spec limits. Use
the tic 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.
Detail showing
center of
linearity test
image. All
lines are one
pixel thick.