Encoder and Rate Conversion
Instead of constraining the encoder to adapt its performance to the aspect ratio requirements, it is possible to use a built-in feature of the Grablink frame grabber.
Recall that we have to achieve the following:
Suppose that we have a non adjustable encoder, happening to have a characteristic pitch of 0.75 mm. We still want the line pitch to be 0.39 mm.
This means that we want the following relation to hold true:
The rate converter makes possible to achieve a frequency multiplication by a non integer ratio with an extremely high accuracy. The ratio can be smaller or larger than the unity.
It can be seen that the rate converter feature provides a smart way to solve the problem of maintaining a constant aspect ratio in line scan inspection systems with varying web speed.