TD2421 is an optical touch monitor which uses two CMOS cameras (optical sensors) placed in the corners at the top of the screen as well as three reflectors (light strips).
These cameras are used to look across the entire touch surface for touch events.
When an object touches the screen, it blocks some of the light being received by the sensors in the cameras.
The location of the touch is then calculated by using the information from both cameras and the mathematical principles of triangulation.
Pros of Optical Touch Screens
Entire screen including the corners is sensitive to touch
Images are crystal clear because no coating is used on the panel
Panels last for a long time as only a light touch is needed to register an input
Support multi-touch events and gestures
Scales with perimeter and not area
However, even with those pros, there’s also some limitation.
Performance may be interfered/affected by direct sunlight or reflections from wet or shiny surfaces.
That’s why it’s observed to receive touch signal randomly while exposed to sunlight.
Please avoid exposing the monitor to direct sunlight or glare reflection as mentioned in the user guide as below.