Elo TouchSystems DOS and Windows Driver Disk, Руководство пользователя

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12 Chapter 2 - Installation
S
TEP
4 - C
ALIBRATING THE
T
OUCHSCREEN
The final installation step is calibrating the touchscreen. Type "GO" when
instructed to begin the calibration sequence.
You will be prompted to touch three calibration points on the screen. Before you
do so, position yourself in front of the screen in normal sitting (or standing)
position, with normal height and reach.
Using your finger as accurately as possible, touch each of the three points as they
appear in the corners of the screen. The program responds with a beep as you lift
your finger from each point.
Calibration is performed in four common video modes: 80x25 text mode, CGA
320x200 graphics, VGA 320x200 graphics, and VGA 640x480. If your DOS
application runs in another video mode, see Chapter 4 for additional information
on ELOCALIB. If you are running Windows in another video mode such as super
VGA, see Chapter 6 for information on calibrating the touchscreen in Windows
with the Touchscreen Control Panel.
The numerical values for the calibration points for the last video mode are
displayed. X or Y axis inversion is normal.
If the calibration program does not respond to a touch, check the cabling, the
switch and/or jumper settings on the controller, and the configuration you selected
when installing the software. Run SETUP to change the configuration (see page
14). See Appendix B, page 93 for additional troubleshooting information.
Why Calibration is Necessary
The need for calibration is unique to the touchscreen. Unlike mouse or keyboard
applications where the cursor is part of the image, a touchscreen is a physical
overlay with an independent coordinate system. Only by knowing the position of
the image can the PC software convert touchscreen coordinates into image
coordinates.
Besides the differences among touchscreens and controllers, calibration also
compensates for the variation in video image among displays. The image is
affected by horizontal and vertical adjustments on the monitor and by the physical
mounting of the touchscreen.
Additional calibration complications include image blooming, where bright
colored images expand, and the "pin cushion" effect, which causes the corners of
the display to be stretched. Poor display linearity can cause similarly sized boxes
to be larger at the edges of the screen than they are in the middle, or vice versa.