Patent ID: 11933923
Assignee: PAUL SCHERRER INSTITUT
Field: Environmental technology (Chemistry)
Classification: CPC G | IPC G

Claim 3:
4. A dual mode detector system for photon detection that is configured for operation either in single photon counting mode or in charge integrating mode with or without gain switching, the detector system comprising:
a) a layer of photosensitive material;
b) an N×M array of photo-detector diodes arranged in said layer of photosensitive material, each of said photo-detector diodes having a bias potential interface connected to a bias potential and a diode output interface;
c) a N×M array of high gain, low noise readout unit cells, one readout unit cell for each photo-detector diode; and
d) each readout unit cell having:
d1) an input interface connecting said diode output interface to a high-gain charge-to-voltage amplifier;
d2) said high-gain charge-to-voltage amplifier having a feedback network between input and output comprising:
d21) a number of feedback capacitors which can be switched in or out from said feedback network;
d22) a fixed or controllable feedback resistance, using a preamp voltage, which can be switched in or out from said feedback network, needed in single photon counting mode;
d23) a preamp reset switch, needed to reset the feedback capacitors to a voltage of zero between their terminals in charge integrating mode;

d3) said high-gain charge-to-voltage amplifier being connected to a shaper/CDS having a feedback network between input and output;
d4) said shaper having a feedback network between input and output, comprising:
d41) a number of feedback capacitors which can be switched in or out from said feedback network;
d42) a fixed or controllable feedback resistance, needed in single photon counting mode, using a shaper voltage, which can be switched in or out from the feedback network;
d43) a CDS reset switch, needed to reset the feedback capacitors to a voltage of zero between their terminals in charge integrating mode;

d5) a discriminator trimming circuitry bloc, receiving as an input a set of trim bits and providing needed adjustment biases to the discriminator to reduce channel-to-channel dispersion;
d6) a discriminator receiving as an input the biases generated by said discriminator trimming circuitry, the output voltage of the high-gain charge-to-voltage amplifier in charge integrating mode and the output of the shaper in single photon counting mode, thus detecting when the preamplifier reaches saturation in charge integrating mode or when a photon was impinging on the photo detector diode in single photon counting mode;
d7) a counter connected to said discriminator in single photon counting mode, needed to count the number of photons;
d8) a number of switches, said switches being controlled to enable the use of the high-gain charge-to-voltage amplifier, the shaper and the discriminator in both modes;
d9) a channel status register receiving control signals from the chip periphery, such that every CSR can be loaded with specific values, and allows every channel to behave differently;
d10) a control logic receiving input from the CSR and connected to the output of the discriminator and to control signals coming from the chip periphery, generating the necessary steering signals for the preamplifier feedback network, the shaper feedback network, the counter and the discriminator fine tuning;
d11) a counter readout comprising the required digital circuitry needed to readout said counter;
d12) an analog readout, comprising the required analog circuitry needed to readout the voltage of said sample and hold circuit; and

e) a channel readout architecture having:
e1) one or more analog multiplexers connected to the analog readout circuitry of all channels and configured to, according to the channel selection and MUX control signals, route the selected channels to one or more analog outputs; and
e2) one or more digital multiplexers being connected to the counter readout circuitry of all channels and configured to, according to the channel selection and MUX control signals, route the selected channels to one or more digital outputs.