HSDL-3202 Datasheet, PDF (14/16 Pages) Agilent(Hewlett-Packard) – IrDA® Data 1.3 Low Power Compliant 115.2 Kb/s Infrared Transceiver

Shape of the Window
From an optics standpoint, the
window should be flat. This en-
sures that the window will not
alter either the radiation pattern
of the LED, or the receive pattern
of the photodiode.
Flat Window
If the window must be curved for
mechanical design reasons, place
a curve on the back side of the
window that has the same radius
as the front side. While this will
not completely eliminate the lens
effect of the front curved surface,
it will reduce the effects. The
amount of change in the radiation
pattern is dependent upon the
material chosen for the window,
the radius of the front and back
curves, and the distance from the
back surface to the transceiver.
Once these items are known, a
lens design can be made which
will eliminate the effect of the
front surface curve.
The following drawings show the
effects of a curved window on the
radiation pattern. In all cases,
the center thickness of the win-
dow is 1.5 mm, the window is
made of polycarbonate plastic,
and the distance from the trans-
ceiver to the back surface of the
window is 3 mm.
Curved Front, Flat Back
(This option is not recommended
and should not be used.)
Curved Front and Back
(This option can be used if neces-
sary for application purpose. A
large radius of curvature is
recommended and both front and
back should have the same
radius.)
14