The spectral response of the human eye changes with
light intensity. The eye has two distinctive spectral responses, which are
defined according to the brightness of the light entering the eye. The
first spectral response of the eye occurs under typical daytime lighting
conditions (photopic) defined for light intensity greater than 0.1 Lux.
The second spectral response occurs under low light conditions (scotopic)
defined for light intensity between 0.01 and 0.0001 Lux. Light intensity
less than 0.0001 Lux is undetectable by the human eye. The eye's shift
from the photopic response to the scotopic response is know as the
Purkinje shift. See figure 1 for spectral response. This detector is ideal for
measuring flash lamps used in the curing industry.
The peak intensity of a flashed
source is much higher then continuous sources. The PMA2135 Photopic flash detector
captures the peak intensity and displays it on the PMA2100 for a period of 5 seconds. In
addition to the peak intensity, the PMA2135 also integrates and holds the dose of a single
pulse.
The peak intensity of the radiation is measured in mW/cm2
or W/cm2. The full scale is specified by the user when ordred.
The dose has a full scale in mJ/cm2 or J/cm2.
The photodetector has an active area of 0.474 inches
The Teflon hemisphere results in the photopic detector having an exceptionally good
cosine response. This response allows for accurate measurements of both point and extended
light sources.
