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MEASUREMENT matters
Video measurement: lights, camera—progress
16 | MAY/JUNE 2012 | MICROmanufacturing
Having been in the manufacturing
industry for almost 20 years, specializing
in metrology, I have seen many changes
in video-measurement systems. The technology
has made great strides in recent years.
The addition of new system features has
changed how inspection personnel capture,
display and use images.
When I first joined the industry, videomeasurement
units (VMUs) ran on the
DOS operating system and system lighting
left much to be desired. Today, the systems
incorporate much better cameras, run on the
latest Windows operating systems and offer
LED-based lighting that is controllable and
repeatable.
Brighter picture today
Comparing today’s VMUs with their
predecessors, the most noticeable difference
is image size and clarity of the display.
All images: Scienscope
Out with the old, in with the new. Video
measurement began with units such as the one
at right with 9" monitors, metrology boxes and
black-and-white cameras. Modern VMUs (left)
come with touch screens, large monitors and
sophisticated software that improves accuracy and
ease of use.
Digital cameras that offer vibrant and bold
four-color images have replaced outdated
black-and-white cameras. Where once 9"
monitors were the largest that could be used,
today the only limit to monitor size is the
workspace available for it.
Cameras of the past had many weaknesses,
the biggest being the connector.
BNC (bayonet-style) connectors offered only
a mono signal. Then came RCA (phono)
connectors, where the image was split, then
put back together. (Something was always
lost in translation with these connectors.)
Today, USB connectors enable a direct
connection from the camera to the computer.
The downside to USB connectors is the
refresh rate isn’t as fast as when using highdefinition
multimedia interface (HDMI)
connectors, and neither is the clarity.
The next generation of video-measurement
machines will offer full HD images.
Using an HDMI connector, the user will
be able to transfer images directly from the
camera to a “frame grabber” card on the
measurement machine, allowing for the
clearest possible digital image to be displayed.
This will allow parts on the screen to be
seen as clearly as the images from a Blu-ray
disc player in a home theater system, and
will prove particularly advantageous for
inspecting microparts that might otherwise
be difficult to see.
Increasingly powerful computers and
monitors are now more affordable, which
has led to major improvements in videomeasurement
equipment. New systems have
touch screens. There are edge-detection
tools available that find features—and allow
users to measure them just by sliding a finger
across the screen. Also, users can choose a
one-button tool that allows them to measure
the contents of a circle on the screen.
The ability to measure parts accurately on
the display is a major innovation. With older
VMUs, a model of the part would be built in
a separate, geometric screen, where features
such as hole-to-hole locations, angles and
distances would be measured. In on-display
measurement, all the measurements are
listed right on the picture of the part. This is
a useful feature because the picture can be