Charge-coupled radiation sensing circuit with charge skim-off and reset

Claim 2

The combination in a radiation sensing array of: a radiation sensor for accumulating charge signal in response to radiation received thereby; a drain maintained at a potential suitable for receiving said charge signal; a register stage; means coupling said sensor to said register stage for transferring to said register stage only that portion of the charge Signal accumulated by said sensor of greater than a given charge signal level; and means coupling said sensor to said drain for forming a potential barrier between said sensor and said drain in response to one value of control signal and for forming a conduction channel between said sensor and said drain for transferring the remaining portion of the charge signal to said drain and resetting said sensor to a reference potential in the process, in response a second value of said control signal.

Claim 3

The combination as set forth in claim 1, wherein said means coupling said sensor to said register stage comprises means forming a potential barrier to the transfer of said charge signal in response to one value of a transfer signal, and forming a conduction path for transferring said portion of said charge signal of greater than said given value to said register stage in response to a second value of said transfer signal.

Claim 4

The combination as set forth in claim 2, wherein said register stage comprises a charge-coupled register stage.

Claim 5

The combination as set forth in claim 1, wherein said radiation sensor comprises a region of one conductivity type located in a substrate of different conductivity type.

Claim 6

The combination as set forth in claim 4, wherein said drain compirses a second region in said substrate of said one conductivity type, and wherein said means coupling said sensor to said drain comprises a gate electrode spaced and insulated from said substrate and from said two regions, and extending between said two regions.

Claim 7

A radiation sensing circuit comprising, in combination; a radiation sensor for accumulating charge signal in response to radiation received thereby; a drain maintained at a potential suitable for receiving said charge signal; a register stage; a conduction path between said radiation sensor and said register stage; means for controlled the conduction through said path to a relatively low level to permit only that portion of the charge signal accumulated by said sensor which exceeds a given relatively large fraction, more than at least half the storage capacity of said well, to pass through said conduction path to said register stage; a second conduction path, this one between said radiation sensor and said drain; and means for preventing conduction through said second conduction path during the transfer of charge from said radiation sensor to said register stage and for thereafter controlling the conduction through said second conduction path at a relatively high level to remove the charge remaining in said radiation sensor to said drain and for resetting the sensor to substantially the drain potential, in the process.

Claim 8

A radiation sensing circuit comprising, in combination; a radiation sensor for accumulating charge signal in response to radiation received thereby; a drain maintained at a potential suitable for receiving said charge signal; a register stage; a conduction path between said radiation sensor and said register stage; means for controlled the conduction through said path to a relatively low level to permit only that portion of the charge signal accumulated by said sensor which exceeds a given relatively large fraction, more than at least half the storage capacity of said well, to pass through said conduction path to said register stage; a second conduction path, this one between said radiation sensor and said drain; and means for preventing conduction through said second conduction path during the transfer of charge from said radiation sensor to said register stage and for thereafter controlling the conduction through said second conduction path at a relatively high level to remove the charge remaining in said radiation sensor to said drain and for resetting the sensor to substantially the drain potential, in the process.

Claim 9

A radiation sensing circuit as set forth in claim 6 wherein each conduction path comprises the source-to-drain path of a field effect transistor and wherein the means for controlling the first-named such path comprises means for applying to the gate electrode of the field effect transistor containing that path a relatively low level of voltage in the forward direction for establishing conduction at a relatively high impedance level through said path, and said means for controlling the second path comprises means for applying to the gate electrode of the field effect transistor containing that second conduction path a voltage which can be switched between a first level at which said conduction path is cut off and a second relatively high level of voltage in the forward direction for establishing conduction at a relatively low impedance level through said second path.