Page 70 - Sensors and Control Systems in Manufacturing

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Cha p te r

4000 O n e
Master
3000
Intensity (counts) 2000

1000

0
400 500 600 700 800 900
Wavelength (nm)
FIGURE 1.15 Spectrographic analysis of a non-phosphor white LED at 19.28 mA.

4000
Master
3000
Intensity (counts) 2000

1000

0
400 500 600 700 800 900
Wavelength (nm)
FIGURE 1.16 Spectrographic analysis of a non-phosphor white LED at ~1.8 mA.

1.15 Luminous Intensity (Candlepower)
The luminous intensity, or candlepower, is the light density within a
very small solid angle, in a specified direction. In other words, this is
the total number of lumens from a surface emitted in a given direc-
tion. The unit of measure is candela. In modern standards, the candela
is the basic of all measurements of light, and all other units are derived
from it. Candlepower measurements are often taken at various angles
around the source, and the results are then plotted to give a candle-
power distribution curve. Such a curve shows luminous intensity (how
“bright” the source seems) in any direction.