Detector characteristics pixel sizes

The size of the detector is a fundamental way to describe the detector s spatial characteristics, just as the size of your paintbrush limits the detail you can achieve in a portrait. In the 1960s, you could buy a 4mmx4mm Ge detector, or, for better resolution you could select a 1 mmx 1 mm detector. Now arrays with 15 pm pixels are available. In addition to the size, we need to know whether the responsivity varies across the active area, and if so, by how much. We talk about that briefly in Section 10.5.2 (Spatial Measurements). 

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