Abstract: A signal processing circuit for processing in real time output signals from a radiation sensing assembly which generates for successive sampling periods output signals representing respectively a reference level and a radiation level related to the radiation incident on a sensor of the assembly during each sampling period. The circuit comprises a low pass filter for receiving the output signals and for filtering a plurality of reference level signals and a corresponding plurality of radiation level signals associated with the plurality of reference level signals to minimize high frequency noise effects on the signals and to generate filtered and averaged reference level and radiation level signals; and a difference circuit for generating a signal related to the difference between the filtered reference level and filtered radiation level signals.

Abstract: A method of recording an image on a record medium in which the image comprises a number of interleaved first patterns (FIG. 1A) comprises deriving a second pattern (17) formed by a complete first pattern and portions of other first patterns whereby the image comprises a plurality of the second patterns in the same orientation and which are not interleaved, and causing relative movement between the record medium (32) and an exposing beam such that the beam scans the record medium and is repeatedly controlled to reproduce the second pattern and thus the image on the record medium.