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US 7,742,152 B2Granted
Coherent detection scheme for FM chirped laser radar
AssigneeUniversity of Kansas
InventorsRongqing Hui, Christopher T. Allen, Peter Adany
Life of this patent
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Abstract
An optical homodyne detection scheme for FM chirped lidar is described. The system performs de-chirping within a photodetector, and it does not require high-speed photo-detection or RF mixing. Embodiments are also described for dealing with phase noise.
Claims20
A method for determining the distance to an object, comprising:
- intensity modulating a laser pulse with a chirp waveform u(t) having a frequency that varies linearly with time;
- splitting the modulated laser pulse into an optical transmit signal that is transmitted to the object and an optical local oscillator signal;
- receiving the optical transmit signal backscattered from the object;
- and,
- mixing the backscattered optical transmit signal and the optical local oscillator signal and detecting the difference in frequency between the modulating chirp waveform u(t) of the optical local oscillator signal and the modulating chirp waveform u(t−Δ) of the backscattered optical transmit signal as delayed by the transit time Δ in traveling to and from the object;
- and
- deriving the value of the transit time Δ of the backscattered optical transmit signal from the detected frequency difference and computing the distance to the object therefrom.
4 more elements
An apparatus for determining the distance to an object, comprising:
- a laser;
- a modulator for intensity modulating the output of the laser into one or more laser pulses and modulating each laser pulse with a chirp waveform u(t) having a frequency that varies linearly with time;
- a beamsplitter for splitting the modulated laser pulse into an optical transmit signal that is transmitted to the object and an optical local oscillator signal;
- an optical receiver for receiving the optical transmit signal backscattered from the object;
- and,
- means for mixing the backscattered optical transmit signal and the optical local oscillator signal and detecting the difference in frequency between the modulating chirp waveform u(t) of the optical local oscillator signal and the modulating chirp waveform u(t−Δ) of the backscattered optical transmit signal as delayed by the transit time Δ in traveling to and from the object;
- and
- processing circuitry for deriving the value of the transit time Δ of the backscattered optical transmit signal from the detected frequency difference and computing the distance to the object therefrom.
5 more elements
Dependencies are inferred from the claim text.