CMOS readout architecture and method for photon-counting arrays
First Claim
1. An apparatus for detecting and counting photons, comprising:
- sensing elements, each sensing element including;
a photon-counting detector to provide signals representative of detected photons;
a digital counter operably coupled to the photon-counting detector and configured to change a count responsive to the signals from the photon-counting detector and to continue changing the count after the number of detected photons has exceeded a certain number;
an overflow bit operably coupled to the digital counter and responsive to an indication that the count in the digital counter has reached the certain number; and
a rolling readout system operably coupled to each sensing element and configured to poll the overflow bit.
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Abstract
Embodiments of the present invention include complementary metal-oxide-semiconductor (CMOS) readout architectures for photon-counting arrays with a photon-counting detector, a digital counter, and an overflow bit in each of the sensing elements in the array. Typically, the photon-counting detector is a Geiger-mode avalanche photodiode (APD) that emits brief pulses every time it detects a photon. The pulse increments the digital counters, which, in turn, sets the overflow bit once it reaches a given count. A rolling readout system operably coupled to each sensing element polls the overflow bit, and, if the overflow bit is high, initiates a data transfer from the overflow bit to a frame store. Compared to other photo-counting imagers, photon-counting imagers with counters and overflow bits operate with decreased transfer bandwidth, high dynamic range, and fine spatial resolution.
34 Citations
35 Claims
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1. An apparatus for detecting and counting photons, comprising:
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sensing elements, each sensing element including; a photon-counting detector to provide signals representative of detected photons; a digital counter operably coupled to the photon-counting detector and configured to change a count responsive to the signals from the photon-counting detector and to continue changing the count after the number of detected photons has exceeded a certain number; an overflow bit operably coupled to the digital counter and responsive to an indication that the count in the digital counter has reached the certain number; and a rolling readout system operably coupled to each sensing element and configured to poll the overflow bit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for detecting and counting photons, comprising:
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sensing elements, each sensing element including; a photon-counting detector; a digital counter operably coupled to the photon-counting detector and responsive to signals from the photon-counting detector; an overflow bit operably coupled to the digital counter and responsive to the digital counter; and a rolling readout system operably coupled to each sensing element and configured to poll the overflow bit, wherein the overflow bit is a most-significant bit in the digital counter.
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18. An apparatus for detecting and counting photons, comprising:
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sensing elements, each sensing element including; a photon-counting detector; a digital counter operably coupled to the photon-counting detector and responsive to signals from the photon-counting detector; an overflow bit operably coupled to the digital counter and responsive to the digital counter; a rolling readout system operably coupled to each sensing element and configured to poll the overflow bit; and an external processor or external memory operably coupled to the overflow bit and configured to store or process data from the overflow bit.
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19. A method of detecting and counting photons, comprising:
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detecting photons at a particular sensing element in an array of sensing elements; incrementing a count in a digital counter in the particular sensing element in response to detection of each photon by the sensing element; setting an overflow bit in the particular sensing element responsive to the digital counter'"'"'s indicating that a certain number of photons has been counted; changing the count in the digital counter, after setting the overflow bit, in response to detection of additional photons by the sensing element; and polling the overflow bit to yield an indication that the certain number of photons has been counted. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A method of detecting and counting photons, comprising:
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detecting photons at a particular sensing element in an array of sensing elements; incrementing a digital counter in the particular sensing element in response to detection of each photon by the sensing element; setting an overflow bit in the particular sensing element responsive to the digital counter'"'"'s indicating that a certain number of photons has been counted; and polling the overflow bit to yield an indication that the certain number of photons has been counted, wherein the overflow bit is a most-significant bit in the digital counter.
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33. A method of detecting and counting photons, comprising:
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detecting photons at a particular sensing element in an array of sensing elements; incrementing a digital counter in the particular sensing element in response to detection of each photon by the sensing element; setting an overflow bit in the particular sensing element responsive to the digital counter'"'"'s indicating that a certain number of photons has been counted; polling the overflow bit to yield an indication that the certain number of photons has been counted; and interrogating the digital counter less frequently than the polling of the overflow bit.
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34. A method of detecting and counting photons, comprising:
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detecting photons at a particular sensing element in an array of sensing elements; incrementing a digital counter in the particular sensing element in response to detection of each photon by the sensing element; setting an overflow bit in the particular sensing element responsive to the digital counter'"'"'s indicating that a certain number of photons has been counted; polling the overflow bit to yield an indication that the certain number of photons has been counted; transferring data from the overflow bit to an off-chip processor or off-chip memory; and processing the overflow bit with the off-chip processor or storing the overflow bit with the off-chip memory.
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35. A sensing element, comprising:
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a photon-counting detector to provide signals representative of detected photons; a digital counter operably coupled to the photon-counting detector and configured to change a count responsive to the signals from the photon-counting detector and to continue changing the count after the number of detected photons has exceeded a certain number; and an overflow bit operably coupled to the digital counter and responsive to an indication that the count in the digital counter has reached the certain number.
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Specification