WORLD OF INDUSTRIES 5/2019

Another functional principle is applied by color measurement systems
such as the colorControl ACS7000 from Micro-Epsilon Eltrotec.
This divides the spectrum of the incident light via a refraction
on a grid into 256 parts, which are imaged behind the grid onto a
CCD sensor line. This is how the complete visible spectrum can be
accurately measured with a spectral resolution of 5 nm. The color
measurement system not only compares the colors to reference values,
but also identifies and outputs these as coordinates in the color
space. As well as the sensor system, the white light LED is incorporated
into the housing of the system, enabling different sensor
heads to be connected via optical-fiber cables. In the ACS1 standard
sensor for conventional measurement tasks, illumination and
receiver are either arranged at an angle of 30°×:0° or 45°×:0°. This
leads to observation distances of 50 mm or 38 mm respectively. For
more complex measurement tasks e. g. with structured, highly reflective
or shiny metallic surfaces, the ACS2 circular sensor with
24 circular arranged lighting optics at a measuring angle of 45°c:0°
is used. This ensures continuous, homogeneous lighting for measurements,
regardless of the angular position of the target object.
Even with smaller measurement objects or on curved surfaces, reliable
color measurements are possible. For color measurements of
transparent objects such as film or glass, the ACS3 transmission
sensor is required where illumination and receiver are arranged at
an angle of 180°:0° to each other. This receiver sensor also measures
colors of self-luminous objects. No lighting unit is required.
Ease of use
AUTOMATION
02 The L*a*b color space has established itself in industrial
color inspection tasks and comprises all colors perceptible to the
human eye
03 The CFO100 color sensor can be
easily configured using the teach-in function
divide the light into long-wave (X), medium-wave (Y) and shortwave
(Z) parts. The individual signals are then transformed into
L*a*b* color values. This is how measurement values are generated
which enables the assignment of colors according to the color perception
of the human eye. Therefore, we refer to these as perceptive
color sensors or True Color sensors. They are ideal for recognition of
color deviations. A teach-in function enables the user to program
the desired color on the sensor and to determine the maximum permissible
color deviation. Next, the sensor compares the color of the
products during operation and can e. g. send a signal via a digital
output if the color of the specimen is within the tolerance limits.
Identification of colors as coordinates
in the color space
Although “color measurement” is a complex issue, color sensors
and color measurement systems from Micro-Epsilon Eltrotec are
easy to use. Color teaching is carried out using a teach-in button,
LEDs on the color sensor or the measurement system signify the
mode of operation. In most cases, configuration is performed via an
integrated web server. Settings such as illumination and measurement
frequency for perfect color recognition and measurements
can be set up easily. The output signals are also set up directly using
the web interface.
Measurement of color in numerous industrial
applications
In order to ensure high quality standards, measurement of color is
an invaluable technique in numerous industrial applications. A
typical example is the automotive industry: most bumpers, door
handles and exterior mirrors are painted the same color as the car
chassis. Furthermore, distance sensors and headlight cleaning systems
are integrated in the bumpers. These components are painted
separately but must precisely match the color of the body. During
the assembly process, the measurement system verifies if these colors
are identical because the human eye recognizes even the smallest
of deviations. Also, in the passenger compartment, the colors
must be correct. Here, structured, curved and reflecting surfaces
are additional challenges for color measurement technology. Another
example is in the production of facade panels made from zinc
whose surface color can change after being coated. During production,
the color must be inspected continuously in order to ensure
early recognition of any deviations. Otherwise, facade panels with
slightly deviating colors would stand out, particularly in large facade
areas. In tablet production, the slightest color deviations must
be detected. In transparent blister packs, different color shades
would give a poor impression.
For the above examples and in many other applications, Micro-
Epsilon Eltrotec offers the optimum solution in terms of perceptive
color sensors and color measurement systems. Depending on the
requirements, the user can also solve difficult color measurement
tasks. The products for color recognition and measurement enable
very small Delta-E values, high measurement frequencies and inline
(in-process) measurements. The user benefits from a measurement
system that easily integrates into their industrial control systems and
simple configuration and handling via the integrated web server.
Photographs: Micro Epsilon
www.micro-epsilon.com
26 WORLD OF INDUSTRIES 5/2019