Appendix D: Optical port dimensions
forHSDL-3203:
from the HSDL-3203 to the back
of the window. The distance from
the center of the LED lens to the
center of the photodiode lens, K,
is 5.1 mm. The equations for
computing the window dimen-
sions are as follows:
the above equation. Z' is defined
as:
To ensure IrDA compliance, some
constraints on the height and
width of the window exist. The
minimum dimensions ensure that
the IrDA cone angles are met
without vignetting. The maximum
dimensions minimize the effects
of stray light. The minimum size
corresponds to a cone angle of
30˚ and the maximum size corre-
sponds to a cone angle of 60˚.
Z' = Z + t/n
where ‘t’ is the thickness of the
window and ‘n’ is the refractive
index of the window material.
X = K + 2*(Z + D)*tanA
Y = 2*(Z + D)*tanA
The depth of the LED image in-
side the HSDL-3203, D, is
The above equations assume that
the thickness of the window is
negligible compared to the dis-
tance of the module from the
back of the window (Z). If they
are comparable, Z' replaces Z in
3.17 mm. ‘A’ is the required half
angle for viewing. For IrDA com-
pliance, the minimum is 15˚ and
the maximum is 30˚. Assuming
the thickness of the window to be
negligible, the equations result in
the following tables and graphs.
In the figure below, X is the width
of the window, Y is the height of
the window, and Z is the distance
OPAQUE
IR TRANSPARENT WINDOW
MATERIAL
Z
X
K
IR TRANSPARENT
WINDOW
OPAQUE
MATERIAL
Z
A
D
1 6
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