Center readout intra-oral image sensor

A method for operating an image sensor to record illumination resulting from an X-ray exposure, comprising the steps of:

• providing an array of radiation sensors comprising a plurality of parallel register rows of first photo-responsive pixels that are optically coupled to an X-ray responsive light source, the array further comprising a centrally disposed read-out register comprised of second photo-responsive pixels that are optically coupled to the X-ray responsive light source, the centrally disposed read-out register being orthogonally oriented to the parallel register rows for dividing said array into a first half and a second half, each comprised of a plurality of parallel register half rows, the read-out register being coupled to individual ones of the half rows for receiving photo-induced charge packets therefrom;
• initiating an X-ray exposure having an initial estimated exposure time;
• during the X-ray exposure, accumulating photo-induced charge within individual ones of the first and second photo-responsive pixels;
• at a time prior to a termination of the predetermined exposure time, reading out first accumulated photo-induced charge from the second pixels of the centrally disposed read-out register;
• and
• modifying, if appropriate, the initial estimated exposure time in accordance with a magnitude of the first accumulated photo-induced charge that is read out from the second pixels.

A method for operating an image sensor to record illumination resulting from an X-ray exposure, comprising the steps of:

• providing an array of radiation sensors comprising a plurality of parallel register rows of first photo-responsive pixels that are optically coupled to an X-ray responsive light source, the array further comprising a centrally disposed read-out register comprised of second photo-responsive pixels that are optically coupled to the X-ray responsive light source, the centrally disposed read-out register being orthogonally oriented to the parallel register rows for dividing said array into a first half and a second half, each comprised of a plurality of parallel register half rows, the read-out register being coupled to individual ones of the half rows for receiving photo-induced charge packets therefrom;
• initiating an X-ray exposure having an initial X-ray flux density;
• during the X-ray exposure, accumulating photo-induced charge within individual ones of the first and second photo-responsive pixels;
• at a time prior to a termination of the X-ray exposure, reading out first accumulated photo-induced charge from the second pixels of the centrally disposed read-out register;
• and
• modifying, if appropriate, the initial X-ray flux density in accordance with a magnitude of the first accumulated photo-induced charge that is read out from the second pixels.

A method for operating an image sensor to record illumination resulting from an X-ray exposure, comprising the steps of:

• providing an array of radiation sensors comprising a plurality of parallel register rows of first photo-responsive pixels that are optically coupled to an X-ray responsive light source, the array further comprising a centrally disposed read-out register comprised of second photo-responsive pixels that are optically coupled to the X-ray responsive light source, the centrally disposed read-out register being orthogonally oriented to the parallel register rows for dividing said array into a first half and a second half, each comprised of a plurality of parallel register half rows, the read-out register being coupled to individual ones of the half rows for receiving photo-induced charge packets therefrom;
• prior to initiating an X-ray exposure,
• operating array clocking signals to read out charge packets at least from the second pixels of the centrally disposed read-out register;
• comparing a magnitude of the charge packets to a first threshold magnitude;
• when the first threshold magnitude is exceeded, determining that an X-ray exposure has been initiated;
• terminating the operation of the array clocking signals;
• and
• during the X-ray exposure accumulating photo-induced charge within individual ones of the first and second photo-responsive pixels.

An intra-oral CCD X-ray image sensor, comprising:

• an enclosure having a size that fits within a patient's mouth during an X-ray exposure, said enclosure having a plurality of chamfered corners;
• a region of X-ray responsive light emitting material contained within said enclosure;
• an uncooled CCD array that is optically coupled to said region of X-ray responsive light emitting material and that is contained within said enclosure, said array comprising first photo-responsive elements comprising a plurality of rows, the first photo-responsive elements being responsive to first multi-phase clock signals for shifting photo-induced charge packets along said rows;
• said array further comprising a centrally disposed read-out register comprised of second photo-responsive elements and disposed orthogonally to said rows for dividing said array into a first half and a second half each comprised of a plurality of half rows, said read-out register being coupled to individual ones of said half rows of said first and second halves of said array by first and second transfer gates, respectively, and responsive to at least one second clock for serially shifting, to an output port, charge packets received from said half rows through said first and second transfer gates;
• a charge-sensing amplifier located at said output port for generating output voltages proportional in size to a magnitude of said charge packets, said charge-sensing amplifier being located adjacent to an edge of said array and away from a corner of said array;
• and
• means for coupling clock signals to said array from an external clock signal source and for coupling the output voltages to an external image processing means.