KBF-LQC (E5.2) 12/2010
page 77/106
Radiation in a range of +/- 100° around the 90° axis of incidence is weighted almost equally with a factor
between 1.0 and 0.9. Only with greater angles, weighting of the radiation decreases, technically caused
by the sensor foot.
Comparison of different sensor types
Planar sensor
Spherical sensor
(sensor foot at 270°)
Ideal spherical sensitivity characteristics
Figure 30: Comparison of the spatial sensitivity characteristics
of planar and spherical sensors
Deviation from the vertical: 0°
If a sample is exposed to light with an angle of incidence of 45°, the
spherical sensor assumes the impinging light quantity as equal as the
light quantity that would impinge at vertical irradiation (factor 1). This is
true for a sample with spatial extension, so there is no error in this
case.
A planar sensor instead would consider the cosine of the angle of
incidence: cos 45 = 0.71. Due to the spatial extension of the sample
this correction is not necessary. The planar sensor therefore calcu-
lates the light quantity impinging on the sample by a factor of 0.71
smaller than the light quantity that would impinge at vertical irradiation.
The light really impinging on the sample surface is thus calculated only
to 71% of the real value.
Light
source
In case of exclusive use of entirely flat samples without spatial extension (e.g. spreaded sam-
ples, films), overrating of the light really impinging on the plane surface is possible. Please
contact BINDER Individual for a solution.
If an independent reference measuring device shall be used to directly compare the light in-
tensities, it must bear the same spatial sensitivity characteristics (spherical) as the sensors of
the BINDER system.
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