technology 21
inspection, railroad inspection, food sorting, of expertise available, as line scan systems
wood inspection, and many more.’ are generally more difficult to set up and
The manoeuvrability of a line scan camera implement.’
also adds to its application areas. Robinet says: More specifically, for an application such
‘Surface inspection and metrology also benefit as surface inspection, both types of camera
from the camera positioned at angles other could fit the bill. Linkemann says: ‘For glass
than 90° to the scene.’ inspection, the whole substrate is scanned
Mark Butler, product manager at Dalsa, also with at least one line scan camera. If there
sees line scan cameras as having more dynamic is a microscopic defect [on the substrate] an
applications than their area scan counterparts. area scan camera (with a microscopic lens)
He says: ‘Line scan cameras are best suited could be moved to the location to get images
towards applications where the object you with higher resolution and more detailed
want to take images of is a continuously information.’
moving object. For example, to inspect mail, Butler also sees a potential applications
postal sorting machines use line scan cameras overlap: ‘In most cases, the choice between
to take the image on an envelope that is line scan and area scan is fairly obvious or
moving at more than 3m/s. Other line scan over time the best choice has already been
applications are flat panel display inspection, determined by system designers. However,
parcel sorting, and web inspection.’ both line scan and area scan may be used in
Despite line scan cameras’ advantages, it a production line. For example, in printed
seems area scan cameras are more commonplace circuit board inspection a bank of line scan
though. Linkemann says: ‘Area scan cameras cameras may be used for inspection of the
can be used within nearly every application bare board (i.e. unpopulated boards) and then
[and] are used in machine vision, intelligent the populated board is inspected by area scan
traffic systems (ITS), medical applications, cameras.’
face recognition, movies, and much more.’
Butler adds: ‘Area scan camera are best Industry trends
suited towards applications where the object is Over the years, the scanning camera industry
stopped, thus you can take a full image of the has altered with both line and area seeing
object for further analysis. Key applications technical improvements. Linkemann says:
include medical imaging, security, and printed ‘The quantum efficiency (how many electrons
circuit board automated optical inspection.’ are created from 100 photons) is getting much
According to Williamson, area scan cameras better. Microlenses are attached to the pixels to
are suited to a wide range of applications increase the fill factor and colour filters have
because of their ‘lower resolution and lower also been attached.’
cost applications’ meaning that they are simpler Linkemann adds: ‘The maximum in
sensitivity has also moved from the red to
‘Despite the differences,
green to have a very similar behaviour to the
human eye. Besides that cameras are getting
there is some overlap in the
much more intelligent; pre-processing is often
done inside the camera too, with synchronised
application areas between
cameras used for sports analysis and 3D re-
the two technologies’
construction.’
Protocols have altered the camera technology
too, as Williamson says: ‘[For line scan]the use
to set up and subsequently cause fewer issues of Camera Link has made interfacing to these
during operation. He adds: ‘Cameras can take cameras a lot easier and the frame grabbers
the 2D image in a few tens of microseconds, used have had a lot more control support to
whereas a line scan camera has to build the make implementation easier.’
image up as the product moves.’ The marketplace will continue to shift and
But despite the differences, there is some Butler is optimistic that the application areas
overlap in the application areas between for both cameras will continue to grow: ‘There
the two technologies. Hickman says: ‘There are a number of potential new applications
are many applications where either camera that are emerging. Solar panel inspection and
type can be used – main decision factors intelligent traffic systems are two areas that
include: how easy it will be to achieve the best hold promise.’
illumination; whether a scanning movement Williamson agrees that solar panel
can be sensibly implemented; and the level production will continue to drive the market:
IMVEfeb09 pp20-23 Lines.indd 21 17/2/09 17:11:37
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