Capabilities Of The Handwriting Device; Ir Scanning System; Resolution - Pioneer 504CMX - PDP - 50" Plasma Panel Technical Manual

9. Capabilities of the Handwriting Device

9.1 IR Scanning System

The handwriting device scans IR rays in the horizontal and vertical directions to detect the coordinate positions.
There are 256 horizontal and 144 vertical sets of IR LEDs and sensors arranged on the panel.
The IR sensors for the horizontal direction are located above the scan device panel and the IR sensors for the vertical
direction are located on the left seen from the front.
IR sensors x 256
IR beam direction
IR LEDs x 256
If the conventional scanning method is used, it would be possible achieve resolution of only 256 x 144 as shown above.
However, the scan device also performs scanning in the oblique directions and computations for achieving high
resolution to match the plasma display monitor pixels (1280 x 768).

9.2 Resolution

This device uses infrared beams to scan the screen vertically and horizontally to detect obstructions. The scanning
pattern is automatically adjusted to improve response and accuracy of location detection.
a) Low scan mode
The entire panel is scanned while there is no light-shielding object (dedicated handwriting pen, etc.) on it. The Low Scan
mode scans the entire area horizontally from the left to the right and vertically from the top to the bottom to avoid
obstruction by the cuff (of a right-handed person).
The start timings of horizontal scanning and vertical scanning are synchronized and both of them start from the top left corner.
Vertical beam scanning direction
Horizontal beam
b) High scan mode
After a light-shielding object is detected, scanning is concentrated in the area around the detection position in order to
improve the response and positioning accuracy. In this mode, the IR sensors receive light from oblique directions as
well as the light from the IR LEDs located opposite to them. As interpolation is applied based on the position information
obtained in this way, the position information can be improved drastically in this mode. The High Scan area tracks the
movement of the light-shielding object.
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