WORLD OF INDUSTRIES 5/2019
WORLD OF INDUSTRIES 5/2019
WORLD OF INDUSTRIES 5/2019
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Colorful challenge for<br />
measurement technologies<br />
AUTOMATION<br />
Determination, measurement and detection of colors<br />
in industrial applications are complex measurement<br />
tasks. Compared to other physical quantities, it is<br />
difficult to define color: what exactly is color?<br />
State-of-the-art color measurement technology does<br />
not only answer this question but also offers solutions<br />
for industrial applications.<br />
Author: Dipl.-Ing. (FH) Joachim Hueber, MICRO-EPSILON Eltrotec GmbH,<br />
Uhingen, Germany<br />
Color is a great challenge for industrial measurement technology<br />
since it is an individual, visual sensation elicited by light.<br />
When measuring colors, everything is about comparing the measured<br />
color with the actual color perceived by the human eye. The<br />
crux of the matter in most applications is to detect very slight deviations<br />
in color as even these can be perceived be the human eye.<br />
Painted car parts, printing matter or facade panels are just some<br />
examples of the many products whose color must be inspected<br />
during production.<br />
Human color perception<br />
Color inspection in industrial applications requires suitable sensor<br />
technology that corresponds to the color perception of the human<br />
eye. The latter is invoked by light in the wavelength range of 380 nm<br />
to 780 nm. The human eye has different sensor cells: 120 million<br />
rods for light/dark differentiation and 6 million cones for color perception.<br />
There are three different types of cones, of which each is<br />
receptive to a different wavelength range of the visible spectrum.<br />
Rods are much more sensitive than cones which is why color vision<br />
depends on illumination. Based on human color impression, colors<br />
can be described differently. As there are three different cone types,<br />
the color space consists of three dimensions. Since 1931, the CIE<br />
24 <strong>WORLD</strong> <strong>OF</strong> <strong>INDUSTRIES</strong> 5/<strong>2019</strong>