Signal acquisition in a SPAD detector

• US 10,656,251 B1
• Filed: 01/24/2018
• Issued: 05/19/2020
• Est. Priority Date: 01/25/2017
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Mandai, Shingo, Niclass, Cristiano L.
• Primary Examiner(s): Sohn, Seung C
• Application Number:
  US15/879,350
• Time in Patent Office: 846 Days
• Field of Search: 2502141
• CPC Class Codes: G01J 1/0228 Control of working procedures; Failure detection; Spectral bandwidth calculation
• CPC Class Codes: G01J 1/0233 Handheld
• 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 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes

Abstract

A single-photon avalanche diode (SPAD) detector includes a pixel array comprising multiple pixels and a memory operably connected to the pixel array. Each pixel includes a SPAD. Various techniques for accumulating signals received from the same SPAD over multiple scans and storing the accumulated signals in the memory are disclosed.

Claims

1. A method for operating a single-photon avalanche diode (SPAD) detector that includes an array of SPAD pixels, the method comprising:

enabling an operation of a SPAD of a SPAD pixel in a selected first set of SPAD pixels such that the SPAD detects photons;

receiving first output signals from the SPAD over a first time period;

constructing a histogram for the SPAD in a histogram memory of the SPAD detector based on the first output signals received over the first time period;

receiving second output signals from the SPAD over a second time period, wherein the SPAD is included in a selected second set of SPAD pixels;

updating the histogram in the histogram memory based on the second output signals received over the second time period; and

reading the updated histogram out of the histogram memory.

2. The method of claim 1, wherein:

the SPAD is a first SPAD;

the histogram is a first histogram; and

the histogram memory is a first histogram memory; and

the method further comprises;

enabling an operation of a second SPAD in the selected first set of pixels such that the second SPAD detects photons when the first SPAD is enabled;

receiving third output signals from the second SPAD over the first time period;

constructing a second histogram for the second SPAD in a second histogram memory based on the third output signals received over the first time period;

receiving fourth output signals from the second SPAD over the second time period, wherein the second SPAD is included in the selected second set of pixels;

updating the second histogram in the second histogram memory based on the fourth output signals received over the second time period; and

reading the updated second histogram out of the second histogram memory.

3. The method of claim 2, wherein the first histogram is read out of the first histogram memory during the second time period and the second histogram is read out of the second histogram memory during a third time period that is after the second time period.

4. The method of claim 2, wherein the first histogram is read out of the first histogram memory during a third time period occurring after the second time period and the second histogram is read out of the second histogram memory during a fourth time period occurring after the third time period.

5. The method of claim 1, wherein the histogram stores counts of time-of-flight values of photons detected by the SPAD.

6. A method for operating a single-photon avalanche diode (SPAD) detector, the method comprising:

enabling a respective SPAD in N pixels, the N pixels comprising a subset of the pixels in a pixel array;

simultaneously receiving output signals from the respective SPADs in the N pixels;

selecting a respective histogram memory for each enabled SPAD from a group of N+1 histogram memories;

and

accumulating output values based on the output signals received from each enabled SPAD over multiple scans of the N pixels in the respective selected histogram memories.

7. The method of claim 6, wherein the N pixels are included in a same line of pixels in the pixel array.

8. The method of claim 7, wherein the same line of pixels comprises one of a column of pixels or a row of pixels in the pixel array.

9. The method of claim 6, wherein the N pixels are arranged in a non-linear arrangement.

10. A method for operating a single-photon avalanche diode (SPAD) detector, the method comprising:

simultaneously receiving output signals from a SPAD in each of N pixels, the N pixels comprising a subset of the pixels in a pixel array;

constructing a histogram for each SPAD in a respective one of M histogram memories, where M is greater than N; and

accumulating output values based on output signals received from each SPAD over multiple scans of the N pixels in the respective M histogram memories.

11. The method of claim 10, wherein the N pixels are included in a same line of pixels in the pixel array.

12. The method of claim 11, wherein the same line of pixels comprises one of a column of pixels or a row of pixels in the pixel array.

13. The method of claim 10, wherein the N pixels are arranged in a non-linear arrangement.

14. A method of operating a single-photon avalanche diode (SPAD) detector, comprising:

performing multiple line scan operations on at least a section of a pixel array comprising multiple SPAD pixels, each SPAD pixel having a respective SPAD;

producing, using a time-to-digital converter (TDC) array circuit operably connected to the pixel array, first output values based on first output signals of a SPAD of a first pixel of the section of the pixel array; and

accumulating the first output values produced by the TDC array circuit in a first histogram stored in a memory;

wherein,

the first output values of the TDC array circuit are produced over the multiple line scan operations.

15. The method of operating a SPAD detector of claim 14, further comprising:

producing, by the TDC array circuit, second output values based on second output signals of a SPAD of a second pixel; and

accumulating, in a second histogram stored in the memory, the second output values.

16. The method of operating a SPAD detector of claim 15, further comprising:

enabling a first operation of the SPAD of the first pixel using a first gating transistor operably connected to a first node and a reference voltage;

enabling a first operation of the SPAD of the second pixel using a second gating transistor operably connected to a second node and the reference voltage;

disabling a second operation of the SPAD of the first pixel using the first gating transistor; and

disabling a second operation of the SPAD of the second pixel using the second gating transistor.

17. The method of operating a SPAD detector of claim 16, further comprising enabling the first operation of the first SPAD and the first operation of the second SPAD simultaneously.

18. The method of operating a SPAD detector of claim 16, wherein the first pixel and the second pixel are included in a same line of pixels in the pixel array.

19. The method of operating a SPAD detector of claim 16, wherein the first pixel is connected to a first output line in the pixel array and the second pixel is connected to a second output line in the pixel array, the second output line being different from the first output line.

20. The method of operating a SPAD detector of claim 16, wherein the multiple SPAD pixels in the pixel array are configured in rows and columns, the method further comprising:

applying, by a column decoder of the SPAD detector, a gating signal to the first gating transistor to;

enable the first operation of the SPAD of the first pixel; and

disable the second operation of the SPAD of the first pixel.

21. The method of operating a SPAD detector of claim 15, wherein the SPAD detector is included in a line-scan system.