Jadak Photo Research PR-810, Руководство пользователя

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PR-805/810/810
L
User Manual
19
T
HEORY OF
O
PERATION
P
HOTOMETER
In a photometer, light passes through a custom matched photopic V(

) filter to the highly sensitive
photomultiplier (PMT) detector. The Photopic filter trims the response of the PMT to the CIE 1931
photopic (daylight vision) response curve (see Figure 19). Photometers are especially useful when
photometric brightness (e.g. luminance) of low level sources is required in near real time.
FIGURE 19. V (Λ) CURVE.
The primary unit of visible light power (luminous flux) used in photometry is the lumen. One watt of
radiant energy at the peak sensitivity of the eye (555 nm) is equivalent to a luminous flux of 683 lumens.
Luminous flux (lumen) is radiant flux weighted by the CIE Standard Observer photopic function and is
calculated by the following formula:
where:
830
Luminous flux in lumen = 683

R
(

)
V
(

)
d
(

)
360
R(

) = Absolute spectral radiance flux in watts
V(

) = 1931 CIE Standard Observer for photopic vision
683 = Conversion factor from watts to lumens at the peak of V (

)
d(

) = Data increment (nm)