Fiber-based ladar transceiver for range/doppler imaging with frequency comb generator
First Claim
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1. Ladar apparatus, comprising:
- a generator of light pulses that have finite duration and temporal waveforms comprising multiple, simultaneous frequency components with varying phase relationships between the frequency components and incommensurate spectral frequency spacing;
a transmitter positioned in the light pulses in a manner that promulgates the light pulses toward a target;
a transmitted waveform detector positioned to receive and record a temporal waveform in the duration of a pulse that is promulgated by the transmitter;
a received waveform detector positioned to receive and record a temporal waveform of a pulse that is reflected by the target;
a matched-filter correlator that modifies a recorded waveform with a sequence of phase shifts that correspond to a sequence of hypothesized target velocities for matched-filters and that performs matched-filter cross-correlations between the modified waveforms and the reflected waveform until a match is found; and
a timer that measures time elapsed between transmission of a pulse and reception of the reflected pulse that matches one of the matched-filters in the cross-correlations.
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Abstract
The present invention provides a laser radar (ladar) imaging system in which both the range of an object being imaged and the velocity of the object can be measured simultaneously and accurately with superior range resolution and with minimal ambiguity. Use is made of a ladar system based on matched-filter cross-correlation of light pulse waveforms that have multiple, simultaneous frequency components with phase variation and incommensurate spectral frequency spacing between frequency components.
316 Citations
64 Claims
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1. Ladar apparatus, comprising:
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a generator of light pulses that have finite duration and temporal waveforms comprising multiple, simultaneous frequency components with varying phase relationships between the frequency components and incommensurate spectral frequency spacing; a transmitter positioned in the light pulses in a manner that promulgates the light pulses toward a target; a transmitted waveform detector positioned to receive and record a temporal waveform in the duration of a pulse that is promulgated by the transmitter; a received waveform detector positioned to receive and record a temporal waveform of a pulse that is reflected by the target; a matched-filter correlator that modifies a recorded waveform with a sequence of phase shifts that correspond to a sequence of hypothesized target velocities for matched-filters and that performs matched-filter cross-correlations between the modified waveforms and the reflected waveform until a match is found; and a timer that measures time elapsed between transmission of a pulse and reception of the reflected pulse that matches one of the matched-filters in the cross-correlations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A method of Doppler range and velocity imaging of a target in relation to a platform, comprising the steps of:
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transmitting from the platform a pulse of light having a definite duration and a temporal waveform comprising multiple, simultaneous frequency components with varying phase relationships between the frequency components and incommensurate spectral frequency spacing; recording the temporal waveform in the duration of the pulse while transmitting the pulse; detecting at the platform and recording a reflection of the pulse waveform from the target; modifying the recorded transmitted waveform with a sequence of phase shifts that correspond to a sequence of hypothesized target velocities in relation to the platform to obtain a sequence of modified waveforms and performing a sequence of matched-filter cross-correlations between the modified waveforms and the reflection pulse waveform until a match is found between the reflection pulse waveform and a modified waveform. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64)
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Specification