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Benefits of Controllers in Line Scan Systems
How Controllers Improve Line Scan Systems
Line scan imaging is used extensively for high speed continuous inspection of materials such as sheet steel, paper, textiles and packaging film. The use of trigger timing and lighting controllers can provide users with access to versatile imaging techniques and more. This new white paper looks at different ways a lighting controller can help by overcoming many of the shortcomings of traditional line scan configurations. Use of a lighting controller can result in:
- Lower cost systems
- Higher performance
- More reliable inspections
- Novel imaging configurations
- More compact systems
1. Optimising lighting intensity
Stable lighting is a crucial factor in all machine vision systems to ensure reliable, reproducible inspections. The deterioration in efficiency in LED lighting due to aging may become apparent more quickly in continuous inspection applications using line scan cameras. The ability of lighting controllers to compensate for this is of critical importance. Lighting controllers can also be used to ensure uniform illumination over the full length of the line sensor to compensate for geometric variations.
2. Reducing the number of camera stations
Since line scan cameras have higher line frequencies than ever before, there are more opportunities for changing the way they can be used. Applications that previously required two or more camera stations can now often be combined into a single camera station reducing costs and the overall size of the system. Typically this involves topologies where a controller drives multiple lights sequentially. Images from each light are acquired on consecutive lines using a single camera and each total image extracted in software. This opens up the potential for multispectral imaging and more. Accurate trigger timing can also be used to eliminate the possibility of random noise disrupting multi-light sequences.
3. High performance camera control
Line scan cameras require accurate high speed trigger signals. Dedicated timing controllers can output precision timing triggers to both the camera and lighting controller. This can be particularly useful when an encoder is used to generate the basic timing, since it is generally not possible to for the encoder to generate a single pulse to trigger each line of the camera.
4. Lighting control for line scan imaging
High frequency line scan cameras require consistent and accurate pulsing of the LED output synchronised with these line rates. Poor lighting control can give poor pulse shape which may result in overlapping pulses or not making use of the full exposure time. Timing repeatability is also an essential requirement.
