Resolution and frequency of line scan cameras
These calculations serve to determine the correct resolution and line scan frequency of a line scan camera. Both specifications are important in order to buy the correct line scan camera.
Tip:
An online wizard for the calculation of the line scan frequency can be found in the "Service" area.
Exemplary calculation for a line scan camera
Using a conveyor width of 550 mm (camera image field in X-direction) and a conveyor speed of 4 metres per second, an accuracy of 0.3 mm per pixel should be achieved.
Calculation of the resolution in lateral direction:
- Conveyor width = 550 mm
- Resolution X = 0.3 pixel / mm
- Required pixels = 550 mm / (0.3 mm/pixel) = 1833 pixels
At least 1833 pixels are necessary in order to meet the requirements. Typical resolutions of line scan cameras in machine vision are 1024, 2048, 4096, 8192 or 12288 pixels. When using a 2k line scan camera, our requirement is even slightly over-fulfilled with an accuracy of 0.27 mm per pixel.
Line scan frequency calculation:
For software-related reasons, the image should be generated without any distortions. Of course it would also be possible to achieve a much higher resolution in transport direction. This is solely determined by the image capture frequency of the individual lines.
- Undistorted image: resolution A in X-direction = resolution A in Y-direction
- Resolution = 0.27 pixels
- Transport speed T = 4000 mm/sec
- Sampling rate F = T / A = 14800 Hz
In our sample calculation, a line scan camera with 2k resolution and a line scan frequency of approximately 14.8 kHz can fulfil the task.
Important: Please use an incremental encoder on the conveyor. Only in this way it is guaranteed that a distortion-free image can be captured despite the varying conveyor speeds (start, breaking, speed droop), which always has the same resolution in transport direction.
