Patent ID: 8619241

Claim:
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, of a reflection of said illumination signal, for a first time period at a time tâˆ’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, of said reflection of said illumination signal, for a second time period at a time t+yâˆ’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.