Distance detection method and system

• US RE46,930 E1
• Filed: 12/30/2015
• Issued: 07/03/2018
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: LeddarTech, Inc.
• Original Assignee: LeddarTech, Inc.
• Inventors: Mimeault, Yvan
• Primary Examiner(s): Lee, Christopher E.
• Application Number:
  US14/984,704
• Time in Patent Office: 916 Days
• Field of Search: 180167, 180169, 2502081, 25055938, 327 1, 327 401, 327 406, 327 501, 327 503, 327 506, 327 28, 327 72, 327149, 342 70, 342110, 342118, 342135, 342137
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• 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 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• 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

There is provided a system and method for detecting a distance to an object. The method comprises providing a lighting system having at least one pulse width modulated visible-light source for illumination of a field of view; emitting an illumination signal for illuminating the field of view for a duration of time y using the visible-light source at a time t; integrating a reflection energy for a first time period from a time t−x to a time t+x; determining a first integration value for the first time period; integrating the reflection energy for a second time period from a time t+y−x to a time t+y+x; determining a second integration value for the second time period; calculating a difference value between the first integration value and the second integration value; determining a propagation delay value proportional to the difference value; determining the distance to the object from the propagation delay value.

Claims

1. A method for detecting a distance to an object, comprising:

providing a lighting system having at least one pulse width modulated visible-light source for illumination of a field of view;

emitting an illumination signal for illuminating said field of view for a duration of time y using said visible-light source at a time t, said time t being a center of a transition from a non-illuminated state to an illuminated state of said field of view, for at least one pulse;

starting an optical sensor for integrating a reflection energy captured by said visible-light source optical sensor, of a reflection of said illumination signal, for a first time period at a time t−

x of a first one of said at least one pulse;

stopping said optical sensor for said first time period at a time t+x for said first one of said at least one pulse and determining a first integration value for said first time period;

starting said optical sensor for integrating said reflection energy captured by said visible-light source optical sensor, of said reflection of said illumination signal, for a second time period at a time t+y−

x for a second one of said at least one pulse, said second one being one of said first one and another one of said at least one pulse, y being greater than x;

stopping said optical sensor for said second time period at a time t+y+x for said second one of said at least one pulse and determining a second integration value for said second time period;

measuring a background integration value for non-negligible illumination background from other lighting sources during an integration time 2x when said visible-light source is not emitting;

subtracting from each said first integration value and said second integration value said background integration value to obtain background compensated first integration value and second integration value;

calculating a difference value between said background compensated first integration value and said background compensated second integration value;

determining a propagation delay value proportional to said difference value;

determining said distance to said object from said propagation delay value.

2. A method as claimed in claim 1, further comprising:

providing a threshold distance to a pre-identified object;

comparing said distance to said object with said threshold distance;

determining said object to be said pre-identified object if said comparison is positive.

3. A method as claimed in claim 1, further comprising, when said x is greater than said y, said integrating being larger than a width of the pulse,

switching a synchronisation of said illumination signal with said starting said optical sensor.