Granted Patent B2

US 7,619,197 · App. 12/025,086 · Granted Nov 17, 2009

Abstract

Claims (50)

1. A light sensing array comprising:

a plurality of electrically isolated photo sensors, each photosensor comprising a first terminal and a second terminal, each of the terminals of each photosensor being isolated from the terminals of the other photosensors, wherein each photosensor responds to an incident light level by producing a charge difference between the first and second terminal; and

a differential circuit selectively coupled to the first and second terminals of one of the photosensors for producing an output signal related to the charge difference between the first and second terminals.

2. The light sensing array of claim 1 further comprising a charge readout circuit corresponding to each photosensor, wherein the charge readout circuit comprises:

a first switching element responsive to a scan signal by connecting the first terminal to a first data line; and

a second switching element responsive to the scan signal by connecting the second terminal to a second data line.

3. The light sensing array of claim 2 , in which switching signals applied to the first and second switching elements combine with signals from the photosensor during readout, and the differential charge sensing circuit discriminates between these signals and the charge level.

4. The light sensing array of claim 2 , further comprising a differential charge amplifier that produces an output signal in response to a difference in charge between the first and second data lines.

5. The light sensing array of claim 4 , wherein the differential charge amplifier further comprises a circuitry to apply a difference in voltage between the first data line and the second data line.

6. The light sensing array according to claim 2 further comprising a scan terminal capacitively coupled to at least one of the first data line and the second data line.

7. The light sensing array of claim 6 , further comprising first and second scan terminals capacitively coupled to the first data line and the second data line, wherein signals on the first and second scan terminals are coupled to the data lines in substantially the same manner such that the differential readout substantially eliminates a switching signal from outputs of the first data line and the second data line.

8. The array of claim 2 , wherein at least one of the first switching element and the second switching element comprises a thin film transistor.

9. The light sensing array of claim 1 wherein each of the plurality of photosensors is selected from the group consisting of p-n junction photodiodes, p-i-n photodiodes, MOS photocapacitors, MIS photosensors, and photoconductors.

10. The light sensing array of claim 9 wherein at least one of the photosensors comprises one or more of amorphous silicon, amorphous silicon-carbide, polycrystalline silicon, silicon-germanium, organic semiconductor material, or crystalline silicon.

11. The light sensing array of claim 1 wherein the first and second terminals of a first photo sensor and the first and second terminals of a second photosensor are selectively coupled to a single pair of data lines.

12. The light sensing array of claim 11 further comprising a charge readout circuit for the first and second photo sensors, the charge readout circuit selectively coupling a selected one of the first and second photosensors to the data lines at a time.

13. The light sensing array of claim 12 wherein the charge readout circuit comprises:

first and second switching elements responsive to a first scan signal to respectively connect the first and second terminals of the first photosensor to the first and second data lines; and

third and fourth switching elements responsive to a second scan signal to respectively connect the first and second terminals of the second photosensor to the first and second data lines.

14. A light sensing array comprising:

a plurality of photosensors, each photosensor comprising a first terminal and a second terminal,

a signal sensing circuit corresponding to each photo sensor, wherein the signal sensing circuit comprises:

(i) a first amplifier connected to the first terminal;

(ii) a first switch responsive to a scan signal to connect the first amplifier to a first data line;

(iii) a second amplifier connected to the second terminal; and

(iv) a second switching element responsive to a scan signal to connect the second amplifier signal to a second data line; and

a differential circuit for sensing the difference between signal levels on the first data line and the second data line.

15. The light sensing array of claim 14 further comprising a first reset switching element for switching the first terminal to a first reset voltage level and a second reset switching element for switching the second terminal to a second reset voltage level.

16. The light sensing array of claim 15 wherein the first reset switching element and the second reset switching element are connected to the first data line and the second data line.

17. The light sensing array of claim 14 , wherein the signal sensing circuit is responsive to first and second voltages on the first and second terminals and the first and second amplifiers convert the first and second voltages to first and second currents respectively.

18. The light sensing array of claim 14 , wherein the differential circuit for sensing the difference between signal levels on the first data line and the second data line comprises a first current sensitive amplifier and a second current sensitive amplifier connected to the first data line and the second data line.

19. The light sensing array of claim 14 , wherein the differential circuit for sensing the difference between signal levels on the first data line and the second data line comprises charge amplifiers.

20. The light sensing array of claim 14 , wherein at least one of the first amplifier and the second amplifier comprises a thin film transistor.

21. The light sensing array of claim 14 , wherein the differential circuit for sensing the difference between signal levels on the first data line and the second data line comprises a thin film transistor.

22. The light sensing array of claim 14 , in which the first and second amplifiers of first and second photo sensors are selectively coupled to a single pair of data lines.

23. The light sensing array of claim 22 , further comprising a charge readout circuit for each of the first and second photosensors, the charge readout circuit selectively coupling a selected one of the first and second amplifiers of the first and second photosensors to the first data line and the second data line at a time.

24. A light sensing array comprising:

a front plane comprising a plurality of photosensor pairs, each photosensor in the photosensor pair comprising a first terminal and a second terminal, wherein each photosensor corresponds to an image pixel and wherein each photosensor responds to an incident light level by forming a charge between the first and second terminal according to the incident light level;

a differential amplifier corresponding to each photosensor pair, wherein the differential amplifier has first and second data lines; and

first and second charge sensing circuits corresponding to each differential amplifier, wherein each charge sensing circuit comprises:

(i) a first amplifier providing a first output signal varying with the charge level at the first terminal;

(ii) a first switch responsive to a scan signal to couple the first output signal to the first data line;

(iii) a first reset switch for switching the first terminal to a first reset voltage level;

(iv) a second amplifier providing a second output signal varying with the charge level at the second terminal;

(v) a second switch responsive to a scan signal to couple the second output signal to the second data line; and

(vi) a second reset switch for switching the second terminal to a reset voltage level.

25. A method of operation of the light sensing array of claim 24 , comprising, for each of the scan lines:

obtaining a first sample of the output signal of the differential charge amplifier prior to the start of the scan signal connecting the first and second terminals of the photosensor to the first and second data lines;

obtaining a second sample of the output signal of the differential charge amplifier after the scan signal connects the first and second terminals of the photosensor to the first and second data lines; and

subtracting the first and second samples.

Assignments (12)