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Chapter 4. Combined first and second difference edge sensing. 4.1. INTRODUCTION.
For many years, as discussed in Chapter 2, it has been postulated at B.Ae. that biological vision systems, by and large, are organised to sense 1st differences of scene luminance in space and time. Such a hypothesis has proved to be very robust in multi-dimensional parameter space for human visual threshold modelling. On the other hand, as discussed in Chapter 3, it has to be admitted that the early processes of vision appear to behave like Laplacian operators, thereby providing, it would seem, second differences of scene luminance. When we first attempted to set up a simulation of
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