The Importance of CCD Readout Smear in Heterodyne Imaging Phase Detection Applications

The effects of CCD readout smear on images acquired with a Frame Transfer type sensor are well understood. Manufacturers try to minimise the problem with ever increasing readout clock rates, and consequently the smear effect is of level low enough as to not be visually noticeable. However, when images are acquired for scientific purposes, such as phase determination of a time varying image, this low level of readout smear can become a problem. This paper illustrates the extent of this problem for a heterodyne range imaging application and discusses possible solutions. Furthermore, the solution of de-smear post-processing algorithms has been implemented in the range imaging application, and results showing a substantial improvement in accuracy are presented.