Counting and integrating pixels, detectors, and methods

1. A device, comprising:

a first column line;

a second column line;

a plurality of pixels configured to capture energy from photons; each pixel coupled to the first column line and the second column line and comprising:

a node;

a first transistor;

a photoelectric conversion device coupled to the node through the first transistor;

a buffer coupled between the node and the first column line; and

an integrator coupled between the node and the second column line;

a comparator having an input coupled to the first column line and configured to compare a signal from the first column line to a threshold; and

control logic coupled to the pixels and configured to selectively couple each pixel to the first column line after a sampling period for each pixel.

2. The device of claim 1 , wherein:

the comparator is one of a plurality of comparators or an analog-to-digital converter (ADC) coupled to the first column line and configured to compare the signal from the first column line to a corresponding threshold; and

the device further comprises a plurality of counters, each counter coupled to an output of a corresponding one of the comparators or the analog-to digital converter.

3. The device of claim 1 , wherein for each pixel, the integrator comprises a variable capacitor having a capacitance selectable from among a plurality of values.

4. The device of claim 1 , wherein each pixel further comprises:

a second transistor coupled between the node and an input of the integrator.

5. The device of claim 4 , further comprising a capacitor coupled in parallel with the photoelectric conversion device wherein the first transistor is coupled between the capacitor and the photoelectric conversion device.

6. The device of claim 4 , wherein:

each pixel further comprises a third transistor and a fourth transistor; and

for each pixel:

the integrator comprises an amplifier having an input coupled to the node through the second transistor and an output coupled to the second column line through the third transistor;

the buffer comprises a source follower having an input coupled to the node and an output coupled to the first column line through the fourth transistor.

7. The device of claim 1 , wherein the device is a monolithic integrated circuit.

8. The device of claim 1 , further comprising:

a scintillator having a front surface configured to receive incoming photons and a back surface opposite the front surface;

wherein the pixels are disposed on the front surface.

9. The device of claim 8 , wherein:

the pixels are first pixels of a first pixel array; and

the device further comprises a second pixel array disposed on the back surface of the scintillator.

10. The device of claim 1 , wherein for each pixel:

the integrator is configured to output an integrated signal to the second column line.

11. A method, comprising:

acquiring a signal from a photoelectric conversion device of a pixel during a sampling time period;

incrementing a counter based on the signal;

resetting the acquiring of the signal after the sampling time period; and

integrating the signal over multiple sampling time periods into a single integrated signal.

12. The method of claim 11 , wherein integrating the signal comprises integrating the signal only if the counter is incremented.

13. The method of claim 11 , wherein:

acquiring the signal comprises acquiring the signal to a node; and

the method further comprises destructively resetting the node when the counter is not incremented.

14. The method of claim 11 , further comprising combining the integrated signal and an output of the counter.

15. The method of claim 11 , further comprising:

acquiring a second signal from the photoelectric conversion device during a second sampling time period; and

incrementing the counter based on the second signal.

16. The method of claim 11 , further comprising:

buffering the signal during the sampling time period;

wherein incrementing the counter comprises incrementing the counter based on the buffered signal.

17. The method of claim 11 , wherein incrementing the counter comprises incrementing at least one of a plurality of counters associated with the photoelectric conversion device based on the signal.

18. A device, comprising:

means for integrating a signal from a photoelectric conversion device of a pixel over a first time period to generate a first integrated signal;

means for integrating the first integrated signal over a second time period to generate a second integrated signal; and

means for controlling the first and second time periods such the second time period spans multiple first time periods.

19. The device of claim 18 , further comprising:

means for integrating a second signal from a second photoelectric conversion device of a second pixel during the first time period; and

means for counting based on the first integrated signal and the second integrated signal.

20. The device of claim 18 , further comprising:

means for counting based on a comparison of the first integrated signal and a first threshold; and

means for counting based on a comparison of the first integrated signal and a second threshold different from the first threshold.