A line-scan camera repeatedly captures a narrow strip and builds a two-dimensional image as the target or camera moves. It is used for inspecting continuous surfaces such as sheets, films and metal plates.
Build an area image from individual lines
The sensor pixels capture the width; repeated acquisitions capture the transport direction. Choose the pixel count from the required field of view and the size of the feature you need to detect.
Line scan does not automatically mean better image quality. The lens, lighting, stable motion and selected resolution must work together to produce an image suitable for inspection.
Match acquisition timing to transport speed
Pixel spacing in the transport direction depends on speed and lines captured per second. When speed varies, coordinate acquisition with position information, for example through an appropriate trigger. Incorrect synchronization can stretch or compress the image.
If speed increases while the desired sampling spacing stays the same, the line acquisition frequency must also increase. Check the available line rate, exposure time and transfer bandwidth together.
Deliver sufficient light during a short exposure
The approximate sampling distance in the transport direction is transport speed divided by line rate. For example, 500 mm/s at 0.05 mm per line requires 10,000 lines/s. This is an illustrative calculation, not an OptTech product performance specification. Exposure, readout time and synchronization accuracy must be checked separately.
Short exposures help reduce motion blur but collect less light. Illuminate the narrow capture region sufficiently and check uniformity across its width.
For reflective metals, more light alone may not reveal scratches. Compare contrast by direction using the principles in multi-angle illumination and the hybrid lighting examples.
Four conditions to define before selection
- Capture width and the size of scratches or contaminants to detect
- Transport speed and its variation
- Variation in height or orientation, and vibration
- Available distances and space for the camera, lens and lighting
If you want to capture a stationary target as a complete area, also consider area scan. See the comparison of camera types.
Reference: Basler — Line Scan Cameras. General principles inform this explanation; the selection checks reflect our planning process.
