US 9,213,085 B2 · System and method for measuring the phase of a modulated optical signal

Abstract

The invention is related to phase detection in lidar systems using single photon detectors (SPDs). The frequency at which the SPDs are time gated is related to but not an integer multiple of the frequency of the transmitted optical pulses. Each return optical pulse arrives with a particular temporal position with respect to the nearest gate, and thus is detected with a related detection efficiency. The SPD output can be segmented into multiple time-multiplexed signals whose relative detection efficiency reveals the phase of the optical return pulses, and no such phases have negligible detection efficiency for all the time-multiplexed signals. To mitigate the impact of afterpulsing and other saturation effects, when a first optical pulse is detected with high detection efficiency the next optical pulse that is detected with high detection efficiency is separated by a time period about equal to or greater than the detector dead time.

Claims15

Dependent claims

An apparatus for determining a range information from a transceiver to an object by measuring a phase of a modulated optical signal, comprising:

a transmitter transmitting the optical signal modulated with a modulation frequency fm and generating optical pulses of temporal half-width of τp towards the object;
a receiver receiving a reflected portion of the modulated optical signal, the receiver contains a single photon sensitive optical receiver with an optical detection efficiency that is modulated at a gate frequency fG with a gate creating a temporal optical detection efficiency half-width of τG, the frequency fG=M·fm where M=I2/I1 and I1 and I2 are relatively prime integers greater than one;
and whereas I2/fG is nearly equal to or larger than the dead time of the optical receiver;
and
a processor to determine the range information of the object.

2 more elements

Dependencies are inferred from the claim text.

System and method for measuring the phase of a modulated optical signal

Life of this patent

System and method for measuring the phase of a modulated optical signal

Life of this patent

Abstract

Claims15