ISL29001 Datasheet, PDF (9/11 Pages) Intersil Corporation – Light-to-Digital Sensor

ISL29001
k = 7.5. This is a scaling factor for the IR sensitive Diode 2.
Flat Window Lens Design
A window lens will surely limit the viewing angle of the
ISL29001. The window lens should be placed directly on top
of the ISL29001. The thickness of the lens should be kept at
minimum to minimize loss of power due to reflection and
also to minimize loss of loss due to absorption of energy in
the plastic material. A thickness of t = 1mm is recommended
for a window lens design. The bigger the diameter of the
window lens the wider the viewing angle is of the ISL29001.
Table 4 shows the recommended dimensions of the optical
window to ensure both 35° and 45° viewing angle. These
dimensions are based on a window lens thickness of 1.0mm
and a refractive index of 1.59.
WINDOW LENS
t
∅
D_TOTAL
D1
ISL29001
D_LENS
∅ = Viewing angle
FIGURE 12. FLAT WINDOW LENS
TABLE 4. RECOMMENDED DIMENSIONS FOR A FLAT
WINDOW DESIGN
D_TOTAL
1.5
D_LENS @ 35°
D_LENS @ 45°
D1
VIEWING ANGLE VIEWING ANGLE
0.50
2.25
3.75
2.0
1.00
3.00
4.75
2.5
1.50
3.75
5.75
3.0
2.00
4.30
6.75
3.5
2.50
5.00
7.75
t=1
D1
D_LENS
D_TOTAL
Thickness of lens
Distance between ISL29001 and inner edge of lens
Diameter of lens
Distance constraint between the ISL29001 and lens
outer edge
* All dimensions are in mm.
Window with Light Guide Design
If a smaller window is desired while maintaining a wide
effective viewing angle of the ISL29001, a cylindrical piece of
transparent plastic is needed to trap the light and then focus
and guide the light on to the ISL29001. Hence the name light
guide is also known as light pipe. The pipe should be placed
directly on top of the ISL29001 with a distance of D1 = 0.5mm
to achieve peak performance. The light pipe should have
minimum of 1.5mm in diameter to ensure that whole area of
the sensor will be exposed. See Figure 13.
D_LENS
D₂ > 1.5mm
LIGHT PIPE
t
L
D₂
D_LENS
ISL29001
FIGURE 13. WINDOW WITH LIGHT GUIDE/PIPE
9
FN6166.6
December 10, 2008