Recommended Pillow Lens Prescriptions
Table 5.3 lists recommended pillow
prescriptions (Ah & Av) for different signal lamp
applications. The pitch can be changed to suit
by varying R as described in the previous
section.
case of the CHMSL, the desired output beam is
the same in the vertical and horizontal. In
addition, for applications where no collimating
secondary optic is used, the function of the
pillow is to break up the appearance of the
sources rather than spread the output beam.
In these cases, a weak, symmetric prescription
pillow was chosen.
Examining Table 5.3, we observe that for
CHMSL designs, a symmetric pillow
prescription was chosen (Ah = Av). However, for
the rear combination lamp/front turn signal
(RCL/FTS) application utilizing a collimating
optic, a non-symmetric pillow prescription was
used (Ah > Av). The desired output beam pattern
for the RCL/FTS applications is twice as wide in
the horizontal than in the vertical; whereas in the
The technique described above provides some
practical tools for designing pillow lenses. If
optical modeling software is available, along with
an accurate model of the LED source, these
tools should be utilized to aid in the design
process and provide more accurate models of
the final output beam.
Table 5.3
RECOMMENDED PILLOW LENS PRESCRIPTIONS
Collimating
Optic
Ah
(deg)
22
Av
(deg)
22
Rh
(mm)
5.3
Ph
(mm)
4
Rv
(mm)
5.3
Pv
(mm)
4
Application
CHMSL
LED Type
HPWA-MHOO
Fresnel Lens
(B = 5°)
CHMSL
RCL/FTS
RCL/FTS
HPWT-DHOO
HPWT-MxOO
HPWT-MxOO
None
5
30
5
5
20
5
17
4.0
17
3
4
3
17
8.9
17
3
5.7
3
(B = 20°)
Fresnel Lens
(B = 7°)
Reflector
Cavity
(B = 20°)
Figure 5.20 Geometry of a single pillow.
12
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