20 prtechnolofile ogy
Scanning the market
Area scan and line scan
cameras offer two very different
options to integrators.
Gemma Church explores these
differences and discovers which
cameras are best suited to
particular applications
Line and area scan cameras are two very
different beasts. While line scan cameras rely on
the camera moving to produce an image built
up line by line, similar to how a photocopier
works, an area scan camera moves this up to
the 2D and is, for all intents and purposes, a
conventional camera.
A line scan camera works in 1D, scanning
the object to be imaged using a line sensor
and putting these lines together to build up Multiple GigE area scan cameras can be easily integrated and operated.
a picture, or just scanning an object in 1D to
check everything on that line appears as it the sensitive area, offering a 100 per cent fill scan is limited by the number of pixels on a
is supposed to. The line itself is an array of factor [the photosensitive area divided by the 2D sensor, which is typically up to 2k x 2k
pixels, with resolutions covering anything pixel size]. Area scan sensors feature a frame of (4 Megapixel) and beyond this they get very
from 512 to 16,000 pixels. pixels, each of them embeds some shutter and expensive. As a line scan camera only has 1D
For an area scan camera it, again, builds up possibly local circuitry, thus having a fill factor pixels, an 8k line scan camera is cheaper than
an image using an array of sensitive pixels, of 80 per cent or less.’ a 4-Megapixel area scan camera. This could
but the area scan camera uses a square or Exposure time between the two types of acquire an 8k x 8k 64 Megapixel image. So
rectangular shaped sensor to capture an cameras differs too. Dr Joachim Linkemann, line scan is good for very high resolution and
om
image all in one go. Simon Hickman, OEM product manager at Basler Vision Technologies, continuous product inspection where the
ope.c
sales manager at Multipix Imaging, says: explains line scan cameras: ‘The lines are taken product is moving continuously.’
eur
‘The resulting image has a width and height one after the other. This means the exposure
.imv
corresponding to the number of pixels on the time is short. To take an image of 1,000 lines Different lives
www sensor – this gives different aspect ratios for (at 1,024 pixels per line) within 100ms, will As Williamson hints, the application areas for
differently-shaped sensors.’ give an exposure time per line of only 100µm. both line and area scan cameras can vary due
 
2009 
ch
Whereas an area scan camera with 1,000 x to the nature of how they take images. For
Breeds apart 1,024 pixels will have the 100ms exposure example, line scan cameras are suited to very
The scanning boundaries of the two differ. time for all pixels. high resolution imaging at very high speeds.
Hickman says: ‘The main differences between ‘A further difference is that the exposure Hickman says: ‘Line scan cameras are best
 
f
ebruary/mar
area and line scan cameras are the shape of the time for an area scan camera will expose all suited to so called “web” applications – this
ope sensor and how it is used to capture an image. pixels, where a line scan camera will grab the is a continuous process that has no discrete
A line scan camera can capture images of lines sequentially to get a full image. Therefore, beginning or end such as paper, textile or glass
fixed width and infinite length. An area scan line scan cameras must be more sensitive than manufacturing. Line scan cameras are also
camera captures images of fixed resolution in area scan cameras.’ very suited to applications where very high
both directions.’ This fixed resolution of an area scan resolution images are required – a single line
Christophe Robinet, strategic marketing camera has direct implications on its cost of up to 12k pixels can be used to create huge
manager for machine vision at e2v, adds: ‘As a and applications, as Mark Williamson, images in one pass.’
typical line scan sensor features pixels in one sales and marketing director for Stemmer And, for line scan cameras, Linkemann
row, registers can be located on each side of Imaging, explains: ‘The resolution of an area adds: ‘Other applications include glass
imaging and machine vision eur
IMVEfeb09 pp20-23 Lines.indd 20 17/2/09 17:11:36
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36