Steps Toward Efficient Mosaic CCD System Design

The areas of available optical detectors are too small for large imaging formats, such as telescope focal planes. One way to obtain large detector areas is to assemble mosaics of CCDs. Parallel driving of many CCDs rules out the possibility of individual tuning; however, such optimization is important, when the ultimate low light-level performance is required, particularly for new, or mixed, devices. In this work, an entirely novel approach, where the drive waveforms are multiplexed and interleaved, is described. This method reduces the number of leadout connections and permits individual device optimization. The controller basically comprises one memory device plus one PLD (programmable logic device) where most of the logic is integrated, minimizing the chip count and improving the efficiency of the system greatly. The system software has a flexible architecture for tailoring to specific operation modes and readout modes. The controller design can handle a mixture of CCD types in any geometric format. The laboratory prototype has been integrated and demonstrated.