Osram Opto Semiconductors has developed an infrared light-emitting
diode (IRED) for use in very thin optical touchscreens. Called the SFH
4053, the small new lamps are housed in a frame surrounding a display.
The lamps create a veritable web of light that overlays the display. If
a user touches the screen, the motion interferes with the light grid at
that particular location, enabling the system to recognize that it is
being touched. The new system takes up only 0.45 millimeters of the
frame’s height and can be easily incorporated into a tablet PC.
Despite its small size, the diode is powerful enough to light up a
laptop display, for example.
An optical touchscreen’s components are mounted in a frame known
as a “bezel,” which surrounds the display and is between
0.5 and one millimeter thick. Rows of IREDs and detectors located
opposite to each other create an invisible, infrared grid. If a user
taps the display, his or her finger will interrupt the light ray and
the signal to the corresponding receptors will cease. Larger displays,
such as those used in notebook and all-in-one (AiO) computers are
flooded with infrared light from two corners. Camera sensors located
next to the IREDs only receive a signal if a finger reflects the light
emitted on the display. Although this method requires few components,
it does need IREDs with a very high radiant flux. The stronger an
infrared LED is, the larger a touchscreen can be made with the same
number of components.
Osram Opto Semiconductors is a division of the Siemens subsidiary
Osram. For the new IRED, the company uses a small chip LED housing that
measures only 0.5 x 1 millimeter, making it one of the thinnest on the
market. The LED emits light at a wavelength of 850 nanometers, which is
invisible to the human eye but can be easily detected by infrared
receptors and camera sensors. Due to the use of highly efficient
thin-film chip technology, the IRED needs little electricity to emit
lots of light and therefore helps to prolong the intervals between
battery-charging for portable devices. The lamp has a radiant flux of
35 mW during continuous operation with a current of 70 mA. The output
can be several times higher in pulse mode.
More information at http://www.osram-os.com/