Active pixel sensors for photon counting X-ray detectors
A photon counting detector includes a plurality of detector sub-modules. Each detector sub-module includes a semiconductor substrate. Each detector sub-module also includes a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate. Each detector sub-module further includes a plurality of traces extending from the plurality of active pixels to readout circuitry. Each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces. Each active pixel includes an amplification stage configured to generate an output signal based on a current pulse output generated by the active pixel. The photon counting detector also includes the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the plurality of detector sub-modules.
1 . A photon counting detector, comprising:
a plurality of detector sub-modules, wherein each detector sub-module of the plurality of detector sub-modules comprises:
a semiconductor substrate; and
a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate; and
a plurality of traces extending from the plurality of active pixels to readout circuitry, wherein each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces, and each active pixel comprises an amplification stage configured to generate an output signal based on a current pulse output generated by the active pixel; and
the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the plurality of detector sub-modules in that the readout circuitry is not located on the semiconductor substrate.
2 . The photon counting detector of claim 1 , wherein the amplification stage is configured to generate the output signal having a higher gain than the current pulse output to increase a signal-to-noise ratio.
3 . The photon counting detector of claim 1 , wherein each active pixel is configured to act as a passive integrator.
4 . The photon counting detector of claim 3 , wherein the amplification stage of each active pixel comprises a transconductance amplifier.
5 . The photon counting detector of claim 4 , wherein the amplification stage of each active pixel comprises a single transistor.
6 . The photon counting detector of claim 5 , wherein each active pixel comprises a pixel capacitor and a bias and reset circuit, wherein the bias and reset circuit is configured to provide a reset path for the pixel capacitor and to keep bias from being provided to the readout circuitry.
7 . The photon counting detector of claim 1 , wherein the amplification stage of each active pixel comprises a charge sensitive amplifier.
8 . The photon counting detector of claim 7 , wherein the amplification stage of each active pixel comprises a first transistor and a second transistor, wherein the first transistor is the charge sensitive amplifier and the second transistor is configured to convert a voltage output to current.
9 . The photon counting detector of claim 8 , wherein each active pixel comprises a current source.
10 . A computed tomography (CT) imaging system, comprising:
a photon counting detector, comprising:
at least one detector sub-module, wherein the at least one detector sub-module comprises:
a semiconductor substrate; and
a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate; and
a plurality of traces extending from the plurality of active pixels to readout circuitry, wherein each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces, and each active pixel comprises an amplification stage configured to generate an output signal based on a current pulse output generated by the active pixel; and
the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the at least one detector sub-module in that the readout circuitry is not located on the semiconductor substrate.
11 . The CT imaging system of claim 10 , wherein each active pixel is configured to act as a passive integrator.
12 . The CT imaging system of claim 11 , wherein the amplification stage of each active pixel comprises a transconductance amplifier.
13 . The CT imaging system of claim 12 , wherein the amplification stage of each active pixel comprises a single transistor.
14 . The CT imaging system of claim 13 , wherein each active pixel comprises a pixel capacitor and a bias and reset circuit, wherein the bias and reset circuit is configured to provide a reset path for the pixel capacitor and to keep bias from being provided to the readout circuitry.
15 . The CT imaging system of claim 13 , comprising a current source located in the readout circuitry, wherein the current source is biased to the single transistor.
16 . The CT imaging system of claim 10 , wherein the amplification stage of each active pixel comprises a charge sensitive amplifier, and the amplification stage of each active pixel comprises a first transistor and a second transistor, wherein the first transistor is the charge sensitive amplifier and the second transistor is configured to convert a voltage output to current.
17 . The CT imaging system of claim 16 , wherein each active pixel comprises a current source.
18 . A photon counting detector, comprising:
at least one detector sub-module, wherein the at least one detector sub-module comprises:
a semiconductor substrate; and
a plurality of active pixels configured to act as detector elements disposed on the semiconductor substrate; and
a plurality of traces extending from the plurality of active pixels to readout circuitry, wherein each active pixel of the plurality of active pixels is coupled to a respective trace of the plurality of traces, wherein each active pixel is configured to act as a passive integrator, and wherein each active pixel comprises a transconductance amplifier comprising a single transistor configured to generate an output signal based on a current pulse output generated by the active pixel; and
the readout circuitry configured to directly read out the output signals from the plurality of active pixels, wherein the readout circuitry is separate from the at least one detector sub-module in that the readout circuitry is not located on the semiconductor substrate, and wherein the readout circuitry comprises a current source biased to the single transistor.