Appendix C: Optical Port
Dimensions for HSDL-3612:
To ensure IrDA compliance,
the back of the window. The
distance from the center of the
LED lens to the center of the
photodiode lens, K, is 7.08mm.
The equations for computing the
window dimensions are as
follows:
Z'=Z+t/n
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
where ‘t’ is the thickness of the
window and ‘n’ is the refractive
index of the window material.
The depth of the LED image
inside the HSDL-3612, D, is
8mm. ‘A’ is the required half
angle for viewing. For IrDA
compliance, the minimum is 15
and the maximum is 30 .
Assuming the thickness of the
window to be negligible, the
X = K + 2*(Z+D)*tanA
Y = 2*(Z+D)*tanA
0
30 and the maximum size
corresponds to a cone angle of
The above equations assume that
the thickness of the window is
negligible compared to the
distance of the module from the
back of the window (Z). If they are
comparable, Z' replaces Z in the
0
º
60 .
0
In the figure below, X is the
width of the window, Y is the
height of the window and Z is the
distance from the HSDL-3612 to
equations result in the following
tables and graphs:
above equation. Z' is defined as
OPAQUE
IR TRANSPARENT WINDOW
MATERIAL
Y
X
K
IR TRANSPARENT
WINDOW
OPAQUE
MATERIAL
Z
A
D
Section of a castellation in Y-axis.
22
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