Line Scan -
Area Scan -
Comparing Line Scan and Area Scan Technologies
Newton Labs has extensive experience in developing
machine vision solutions using both line scan
and area scan technology.
In this diagram pair of line scan cameras inspect
a fast-moving continuous production line of material such as fabrics
or paper, often called a web.Any defects can be precisely located
on the web according to the time they passed the imaging line.
Line scan cameras contain a single row of pixels used to capture data very quickly. As the object moves past the camera, a complete image can be reconstructed in software line by line. Line scan systems are best employed in high-speed processing or fast-moving conveyor line applications.
- With a single row of pixels, line scan cameras can build continuous images not limited to a specific vertical resolution. This allows for much higher resolutions than with area scan cameras.
- Unlike area scan cameras, a line scan camera can expose a new image while the previous image is still transferring its data. This is because the pixel readout is faster than the camera exposure.
- When building a composite image, the line scan camera can either move over an object or have moving objects presented to it.
- Coordination of production/camera motion and image acquisition timing are critical for line scan cameras, but they require only simple illumination.
In this diagram looking down from above, four area
scan cameras placed 90 degrees apart can capture a complete 360
degree inspection of a single product unit as it travels down a
conveyor. Strobe illumination from overhead, or the side(s),"freezes" the
Area scan cameras contain a matrix of pixels that capture an image of a given scene. They are more general purpose than line scan cameras, and offer easier setup and alignment. Area scan cameras are best suited towards applications where the object is stationary, even if only momentarily.
- Area scan cameras provide a fixed resolution, allowing for simplified installation where moving cameras or objects are not desired or practical.
- Area scan cameras can image a defined area quickly, whereas a line scan camera must be moved over the area to produce a similar image.
- Greater flexibility can be had with area scan cameras, as a single image can be segmented into multiple regions-of-interest to look for specific objects rather than having to process the entire image.