Often we are asked about the cameras we commonly use for web and sheet inspection. Line scan cameras are perfect for web inspection but are not well understood. This post looks at Line scan cameras, how they work and why we use them.
How do Line Scan Cameras work?
Line scan cameras are based on building-up an image, one line at a time, using a line sensor which passes in a linear motion over an object, or more often when the object passes in a linear motion under the sensor. As the conveyor or web moves, the image forms but for it to do so the movement must be uniform. This can be technically hard to achieve so the feed must be synchronised by means of an encoder in order to avoid image distortions.
If there are individual objects on a conveyor, an image can also be captured based on the activation of a photoelectric barrier only then the lines are transmitted and it is possible to avoid that the test object spreads over two image blocks. Where the web is a continuous product like paper/print and textiles these are referred to as web-based vision applications.
Why use line scan cameras:
- Can check longer objects and continuous materials.
- Can inspect round bodies without perspective distortion.
- The cost-benefit ratio.
- Ideal in high-speed processing or fast-moving conveyor line applications.
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