LOW PHOTON COUNT TIMING

• US 20170234973A1
• Filed: 02/15/2017
• Published: 08/17/2017
• Est. Priority Date: 02/15/2016
• Status: Active Grant

• Current Assignee: Airborne Hydrography AB (Hexagon AB)
• Original Assignee: Airborne Hydrography AB (Hexagon AB)
• Inventors: AXELSSON, Andreas
• Granted Patent: US 10,845,467 B2
• Time in Patent Office: Days
• 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 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• 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 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• 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

Abstract

The invention relates to a method and a device for determining a return time of a returning light pulse by a Single Photon (SPL) LiDAR scanner, the SPL scanner comprising of a low photon count detector for converting low amounts of photons or single photons to electrical signals, and a control and processing unit for processing the data and for determining the return time of the returning light pulse. The control and processing unit identify detected photons potentially representing a return pulse event and create a return pulse signal based on a criterion involving a temporal probability distribution for the detected photons, identify a rising edge and a falling edge of the return pulse signal, and determine the return time for each return pulse event based on the rising edge and the falling edge of the return pulse signal.

Claims

1. A method for determining a return time of a returning light pulse by a Single Photon LiDAR (SPL) scanner for measuring the time between an outgoing pulse event and a return pulse event, the SPL scanner comprising:

a low photon count detector for converting low amounts of photons or single photons to electrical signals, and

a control and processing unit for processing the data and for determining the return time of the returning light pulse,

wherein the control and processing unit is configured to;

identify a group of detected photons potentially representing a return pulse event and create a return pulse signal based on a criterion involving a temporal probability distribution for the detected photons,

identify a rising edge and a falling edge of the return pulse signal based on the identified group of detected photons potentially representing a return pulse event, and

determine the return time for the return pulse event based on the rising edge and the falling edge of the return pulse signal.

2. The method of claim 1,

wherein the detector of the SPL scanner is adapted to convert a single photon or a photon package to an electrical signal, the electrical signal being proportional to the number of photons detected in the package, the detector being a single-element detector, a multi-element detector, or a detector array.

3. The method of claim 1, wherein the detector of the SPL scanner is adapted to convert a single photon or a photon package to an electrical signal representing one event, the detector being a single-element detector, a multi-element detector, or a detector array.

4. The method of claim 1, wherein the SPL scanner is adapted for creating a multiplicity of return pulse signals based on a multiplicity of different probability thresholds for a photon creating a photoelectron to be converted into an electrical signal, the thresholds respectively being defined as different low amounts of photons in amplitude.

5. The method of claim 1, wherein the control and processing unit is adapted to determine an amplitude information for the return pulse event based on a time difference between the falling edge and the rising edge of the return pulse signal.

6. The method of claim 1, wherein the SPL scanner is adapted for scanning with a single lidar beam or for simultaneously scanning with multiple lidar beams, the multiple lidar beams being produced from a single transmitted laser pulse.

15. A computer program product to be used within a method of claim 1, the computer program product being stored on the control and processing unit, and comprising program code configured such that when executed causes the controlling and processing unit to perform the following steps:

identify a group of detected photons potentially representing a return pulse event and creating a return pulse signal based on a criterion involving a temporal probability distribution for the detected photons,

identify a rising edge and a falling edge of the return pulse signal based on the identified group of detected photons potentially representing a return pulse event, and

determine the return time for each return pulse event based on the rising edge and the falling edge of the return pulse signal.

7. A Single Photon LiDAR (SPL) scanner comprising:

a transmitter for transmitting a light pulse;

a low photon count detector for detecting a returning light pulse, the low photon count detection being adapted for converting low amounts of photons or single photons to electrical signals; and

a control and processing unit for processing the data and for determining the return time of the returning light pulse,

wherein the control and processing unit is configured to;

identify a group of detected photons potentially representing a return pulse event and create a return pulse signal based on a criterion involving a temporal probability distribution for the detected photons,

identify a rising edge and a falling edge of the return pulse signal based on the identified group of detected photons potentially representing a return pulse event, and

determine the return time for the return pulse event based on the rising edge and the falling edge of the return pulse signal.

8. The SPL scanner of claim 7, wherein the detector of the SPL scanner is adapted to convert a single photon or a photon package to an electrical signal, the electrical signal being proportional to the number of photons detected in the package, the detector being a single-element detector, a multi-element detector, or a detector array.

9. The SPL scanner of claim 7, wherein the detector of the SPL scanner is adapted to convert a single photon or a photon package to an electrical signal representing one event, the detector being a single-element detector, a multi-element detector, or a detector array.

10. The SPL scanner of claim 7, wherein the SPL scanner comprises a time to digital converter (TDC) with a high speed comparator.

11. The SPL scanner of claim 7, wherein the SPL scanner is adapted for creating a multiplicity of return pulse signals based on a multiplicity of different probability thresholds for a photon, creating a photoelectron to be converted into an electrical signal.

12. The SPL scanner claim 7, wherein the control and processing unit is configured to determine an amplitude information for the return pulse event based on a time difference between the falling edge and the rising edge of the return pulse signal.

13. The SPL scanner of claim 7, wherein the SPL scanner is configured for scanning with a single lidar beam or for simultaneously scanning with multiple lidar beams.

14. The SPL scanner of claim 7, the TDC being implemented using a field programmable gate array as a high resolution timing device.