APPARATUS FOR DETECTING ILLUMINATION LEVELS

• US 20180058924A1
• Filed: 03/21/2017
• Published: 03/01/2018
• Est. Priority Date: 08/25/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Storm, Graeme, Moore, John Kevin
• Granted Patent: US 10,641,653 B2
• Time in Patent Office: Days
• CPC Class Codes: G01J 1/0228 Control of working procedures; Failure detection; Spectral bandwidth calculation
• CPC Class Codes: G01J 1/4204 with determination of ambient light solar light G01J2001/4266
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 2001/442 Single-photon detection or photon counting
• CPC Class Codes: G01J 2001/4466 Avalanche
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: G01T 1/248 Silicon photomultipliers [SiPM], e.g. an avalanche photodiode [APD] array on a common Si substrate
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H04N 25/709 Circuitry for control of the power supply
• CPC Class Codes: H04N 25/773 comprising photon counting circuits, e.g. single photon detection [SPD] or single photon avalanche diodes [SPAD]
• CPC Class Codes: H04N 25/778 comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself

Abstract

An apparatus includes a single photon avalanche diode pixel that includes a single photon avalanche diode and an output transistor configured to provide an analog output current from the single photon avalanche diode. The single photon avalanche diode pixel is configured to operate in a first mode to output a digital single photon detection event. The single photon avalanche diode pixel is further configured to operate in a second mode to output the analog output current indicating a level of illumination of the pixel.

Claims

1. An apparatus comprising:

a single photon avalanche diode pixel comprising a single photon avalanche diode and output transistor circuitry configured to provide an analog output current from the single photon avalanche diode;

wherein the single photon avalanche diode pixel is configured to operate in a first mode to output a digital single photon detection event; and

wherein the single photon avalanche diode pixel is further configured to operate in a second mode to output the analog output current indicating a level of illumination of the pixel.

2. The apparatus as claimed in claim 1, wherein the single photon avalanche diode is configured to operate in the first mode and second mode at different times or at substantially the same time.

3. The apparatus as claimed in claim 1, wherein the output transistor circuitry is configured to provide the analog output current to an input of a trans-impedance amplifier.

4. The apparatus as claimed in claim 3, wherein the apparatus comprises a plurality of multiple single photon avalanche diode pixels, each single photon avalanche diode pixel configured to provide an analog output current from the single photon avalanche diode of that pixel to the input of the trans-impedance amplifier.

5. The apparatus as claimed in claim 1, further comprising a pulse conditioner coupled to receive a single photon detection event signal pulse and configured to control the output transistor circuitry to output the analog output current, which indicates the level of illumination of the pixel based on a modified length single photon detection event signal pulse.

6. The apparatus as claimed in claim 1, further comprising a current averager configured to determine an average analog output current, wherein the average analog output current indicates an ambient level of illumination of the pixel.

7. The apparatus as claimed in claim 1, wherein the single photon avalanche diode is configured to operate in a Geiger mode of operation in the first mode and in a photodiode mode of operation in the second mode.

8. The apparatus as claimed in claim 1, wherein the output transistor circuitry comprises one or more of:

a quench transistor coupled to an anode of the diode and configured to drain an avalanche current following a detection event;

a pull up transistor coupled to the anode of the diode and configured to enable the potential of the anode of the diode to be pulled up to an further supply voltage; and

an output transistor coupled to the anode of the diode and configured to enable an output of the digital single photon detection event.

9. The apparatus as claimed in claim 1, wherein the output transistor circuitry comprises a quench transistor coupled to an anode of the diode and configured to drain an avalanche current following a detection event, wherein the quench transistor is selectively enabled when the pixel is operated in the first mode.

10. The apparatus as claimed in claim 9, wherein the apparatus is configured so that a quench transistor gate terminal is operated at a high voltage to reduce the impedance of the output transistor when the quench transistor is selectively enabled.

11. The apparatus as claimed in claim 1, wherein the apparatus comprises a plurality of rows single photon avalanche diode pixels, wherein a first row is configured to operate in the first mode and a further row is configured to operate in the second mode at substantially the same time.

12. A method for operating a single photon avalanche diode pixel that comprises a single photon avalanche diode and output transistor circuitry, the method comprising:

configuring the single photon avalanche diode pixel to operate in a first mode to output a digital single photon detection event; and

configuring the single photon avalanche diode pixel to operate in a second mode by configuring the output transistor circuitry to provide an analog output current from the single photon avalanche diode indicating a level of illumination of the pixel.

13. The method as claimed in claim 12, wherein configuring the output transistor circuitry to provide an analog output current from the single photon avalanche diode comprises providing the analog output current from the output transistor circuitry to an input of a trans-impedance amplifier.

14. The method as claimed in claim 13, wherein providing the analog output current from the output transistor circuitry to the input of a trans-impedance amplifier comprises providing the analog output current from multiple single photon avalanche diode pixels to the input of the trans-impedance amplifier.

15. The method as claimed in claim 12, further comprising:

modifying a pulse length of a single photon detection event signal pulse; and

controlling the output transistor to output the analog output current indicating a level of illumination of the pixel based on the modified length single photon detection event signal pulse.

16. An apparatus for operating a single photon avalanche diode pixel that comprises a single photon avalanche diode and an output transistor, the apparatus comprising:

means for configuring the single photon avalanche diode pixel to operate in a first mode to output a digital single photon detection event; and

means for configuring the single photon avalanche diode pixel to operate in a second mode by configuring the output transistor to provide an analog output current from the single photon avalanche diode indicating a level of illumination of the pixel.

17. The apparatus of claim 16, further comprising:

means for modifying the pulse length of a single photon detection event signal pulse; and

means for controlling the output transistor to output the analog output current to indicate a level of illumination of the pixel based on the modified length single photon detection event signal pulse.

18. The apparatus of claim 16, further comprising means for compensating for an ambient level of illumination of the pixel by removing an average analog output current from the analog output current such that the level of illumination of the pixel is an indication of the level of illumination above the ambient level of illumination of the pixel.

19. An apparatus comprising:

a plurality of rows of single photon avalanche diode pixels, each single photon avalanche diode pixel comprising a single photon avalanche diode and an output transistor configured to provide an analog output current from the single photon avalanche diode, wherein the single photon avalanche diode pixels are arranged as sets of pixels, wherein the single photon avalanche diode pixel is configured to operate in a first mode to output a digital single photon detection event, and wherein the single photon avalanche diode pixel is further configured to operate in a second mode to output the analog output current indicating a level of illumination of the pixel; and

a plurality of trans-impedance amplifiers, each trans-impedance amplifier having an input coupled to receive an analog output current from each single photon avalanche diode pixel of a respective one of the sets of pixels.

20. The apparatus as claimed in claim 19, wherein a first set of the pixels is configured to operate in the first mode and a further set of the pixels is configured to operate in the second mode at substantially the same time.

21. The apparatus as claimed in claim 19, wherein a first row of the pixels is configured to operate in the first mode and a further row of the pixels is configured to operate in the second mode at substantially the same time.