Line Scan Systems (Part I) : PCB Inspection

An imaging technique that is not so common in machine vision is Line Scan Imaging. Instead of using an area or a matrix sensor, a line sensor has a linear sensor array capturing a single row of pixels.  Line scan systems are a great alternative (sometimes the only option) when:

  1. Required resolution is really high
  2. Where acquisition speed is a challenge
  3. For continuously moving objects (web)
  4. For round or cylindrical surfaces that need to be inspected
  5. Where uniform illumination is required over a large inspection area.

In these cases, Line Scan systems offer an excellent alternative. Line scan systems offer the best price per pixel, do not need complex lighting schemes, produce clear smear free images and have much better processing efficiencies compared to area scan systems. The trade offs of this technology are complexity in solution development and integration. But with the right integration support these challenges can be overcome. GigE and even USB line scan systems make integration a breeze and complex image acquisition hardware is becoming a thing of the past.

To showcase where image resolution can be improved, we have below two images of PCB’s.

In the Area Scan Image (taken using a Nikon D-90 8MP color camera), we are unable to read the text on the chips due to poor lighting and image quality. The Line Scan Image (using a 4K Color camera) is much more clearer and sharper even though ‘resolution’ is much smaller.

In the next part, we will explain how line scan can be used to achieve great results in the print industry. Thanks for reading!

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