Readout circuit and method for sparse readout of active and neighboring pixels in a multi-pixel sensor array

A readout circuit for reading active pixels in a sensor having at least one sensor segment each containing a plurality of addressable pixels, the readout circuit comprising:

• a sampling circuit coupled to each pixel in each of the segments, for sampling an energy level associated with at least one active pixel,
• a lookup table having a plurality of addressable locations each corresponding to a respective pixel in the sensor and storing addresses of predefined neighboring pixels associated with the respective pixel,
• an encoder having a plurality of input lines each for connecting to a respective trigger channel corresponding to each pixel in the sensor and responsive to one or more trigger signals for generating an address in said lookup table,
• a controller coupled to an output of the encoder for feeding the address generated by encoder to the lookup table and for feeding the addresses of the predefined neighboring pixels output by the lookup table to a respective channel of the sampling circuit for reading the energy level of the respective neighboring pixel,
• a threshold discriminator responsive to a pixel energy level for producing an output signal when the pixel energy level exceeds a threshold value,
• a resettable monostable responsive to the output signal of the threshold discriminator for generating said trigger signal,
• an accumulator for calculating cumulative energy read from the active pixels and successive neighboring pixels as the respective pixel energy of each successive neighboring pixel is read, and
• a reset circuit coupled to the accumulator and being responsive to the cumulative energy exceeding a predetermined value for resetting the encoder and the monostables.

A charge readout detector having at least one sensor segment each containing a plurality of addressable pixels, the charge readout detector including a readout circuit for reading active pixels, the readout circuit comprising:

• a sampling circuit coupled to each pixel in each of the segments, for sampling an energy level associated with at least one active pixel,
• a lookup table having a plurality of addressable locations each corresponding to a respective pixel in the sensor and storing addresses of predefined neighboring pixels associated with the respective pixel,
• an encoder having a plurality of input lines each for connecting to a respective trigger channel corresponding to each pixel in the sensor and responsive to one or more trigger signals for generating an address in said lookup table,
• a controller coupled to an output of the encoder for feeding the address generated by encoder to the lookup table and for feeding the addresses of the predefined neighboring pixels output by the lookup table to a respective channel of the sampling circuit for reading the energy level of the respective neighboring pixel,
• a threshold discriminator responsive to a pixel energy level for producing an output signal when the pixel energy level exceeds a threshold value,
• a resettable monostable responsive to the output signal of the threshold discriminator for generating said trigger signal,
• an accumulator for calculating cumulative energy read from the active pixels and successive neighboring pixels as the respective pixel energy of each successive neighboring pixel is read, and
• a reset circuit coupled to the accumulator and being responsive to the cumulative energy exceeding a predetermined value for resetting the encoder and the monostables.