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U.S. Patent No. 10,000,000 – June 19, 2018

Posted in General Commentary by Jake Ward on June 19, 2018

U.S. Pat. No. 10,000,000: Coherent LADAR using intra-pixel quadrature detection

LADAR
What is claimed is:

1. A laser detection and ranging (LADAR) system, comprising: a two-dimensional array of detector elements, each detector element within the array including: a photosensitive region configured to receive return light reflected from a target and oscillating local light from a local light source, and local processing circuitry coupled to an output of the respective photosensitive region and configured to receive an analog signal on the output and to sample the analog signal a plurality of times during each sample period clock cycle to obtain a plurality of components for a sample during each sample period clock cycle; a data bus coupled to one or more outputs of each of the detector elements and configured to receive the plurality of sample components from each of the detector elements for each sample period clock cycle; and a processor coupled to the data bus and configured to receive, from the data bus, the plurality of sample components from each of the detector elements for each sample period clock cycle and to determine an amplitude and a phase for an interfering frequency corresponding to interference between the return light and the oscillating local light using the plurality of sample components.

2. The system according to claim 1, wherein the two-dimensional array of detector elements comprises a large format array.

3. The system according to claim 1, wherein the plurality of sample components are quadrature components and wherein the quadrature components are employed to determine an amplitude and a phase for each of a plurality of interfering frequencies corresponding to interference between the return light and the oscillating local light.

4. The system according to claim 1, wherein each detector element within the array includes sample component signal line connections to the data bus.

5. The system according to claim 1, wherein each detector element within the array is configured to receive a clock signal from the data bus.

6. The system according to claim 1, wherein the data bus is configured to serialize the plurality of sample components from each of the detector elements for each sample period clock cycle for transmission to the processor.

7. The system according to claim 1, wherein the two-dimensional array of detector elements and the data bus are contained within a read-out integrated circuit (ROIC).

8. The system according to claim 1, further comprising: a laser source configured to emit both light illuminating the target and the oscillating local light; and an imaging telescope positioned between the target and the two-dimensional array of detector elements and configured to focus the return light reflected from the target onto the two-dimensional array of detector elements.

9. A laser detection and ranging (LADAR) system, comprising: a two-dimensional array of detector elements, each detector element within the array including: a photosensitive region configured to receive return light reflected from a target and oscillating local light from a local light source, and local processing circuitry coupled to an output of the respective photosensitive region and configured to receive an analog signal on the output and to sample the analog signal a plurality of times during each sample period clock cycle to obtain components for a sample during each sample period clock cycle; a data bus coupled to one or more outputs of each of the detector elements and configured to receive the plurality of sample components from each of the detector elements for each sample period clock cycle; a processor coupled to the data bus and configured to receive, from the data bus, the plurality of sample components from each of the detector elements for each sample period clock cycle and to determine an amplitude and a phase for an interfering frequency corresponding to interference between the return light and the oscillating local light using the plurality of sample components; a laser source configured to emit both light illuminating the target and the oscillating local light, wherein the laser source comprises: a master oscillator, a first frequency modulator coupled to the master oscillator and configured to modulate a frequency of a signal output by the master oscillator used to generate a signal corresponding to the emitted light illuminating the target, and a second frequency modulator coupled to the master oscillator and configured to modulate the frequency of the signal output by the master oscillator used to generate a signal corresponding to the emitted oscillating local light; and an imaging telescope positioned between the target and the two-dimensional array of detector elements and configured to focus the return light reflected from the target onto the two-dimensional array of detector elements.

10. The system according to claim 9, wherein the laser source further comprises: an amplifier coupled between the first frequency modulator and a light source emitting the light illuminating the target; and a local oscillator coupled between the second frequency modulator and the local light source emitting the oscillating local light, the local oscillator configured to respond to a signal output by the second frequency modulator.

11. A laser detection and ranging (LADAR) method, comprising: receiving, at a two-dimensional array of detector elements, return light reflected from a target, each detector element within the array including: a photosensitive region configured to receive the return light reflected from the target and oscillating local light from a local light source, and local processing circuitry coupled to an output of the respective photosensitive region and configured to receive an analog signal on the output and to sample the analog signal a plurality of times during each sample period clock cycle to obtain a plurality of components for a sample during each sample period clock cycle; receiving, on a data bus coupled to one or more outputs of each of the detector elements, the plurality of sample components from each of the detector elements for each sample period clock cycle; transmitting, to a processor coupled to the data bus, the plurality of sample components from each of the detector elements for each sample period clock cycle; and determining, with the processor, an amplitude and a phase for an interfering frequency corresponding to interference between the return light and the oscillating local light using the plurality of sample components.

12. The method according to claim 11, wherein the two-dimensional array of detector elements comprises a large format array.

13. The method according to claim 11, wherein the plurality of sample components comprise quadrature components, the method further comprising: employing the quadrature components to determine an amplitude and a phase for each of a plurality of interfering frequencies corresponding to interference between the return light and the oscillating local light.

14. The method according to claim 11, wherein each detector element within the array includes sample component signal line connections to the data bus.

15. The method according to claim 11, wherein each detector element within the array is configured to receive a clock signal from the data bus.

16. The method according to claim 11, further comprising: serializing, in the data bus, the plurality of sample components from each of the detector elements for each sample period clock cycle for transmission to the processor.

17. The method according to claim 11, wherein the two-dimensional array of detector elements and the data bus are contained within a read-out integrated circuit (ROIC).

18. The method according to claim 11, further comprising: emitting both light illuminating the target and the oscillating local light from a laser source; and positioning an imaging telescope between the target and the two-dimensional array of detector elements to focus the return light reflected from the target onto the two-dimensional array of detector elements.

19. The method according to claim 18, further comprising: employing a first frequency modulator coupled to a master oscillator to modulate a frequency of a signal output by the master oscillator used to generate a signal corresponding to the emitted light illuminating the target; and employing a second frequency modulator coupled to the master oscillator to modulate the frequency of the signal output by the master oscillator used to generate a signal corresponding to the emitted oscillating local light.

20. The method according to claim 19, further comprising: amplifying an output of the first frequency modulator to drive the light source emitting the light illuminating the target; and receiving an output of the second frequency modulator at a local oscillator driving the light source emitting the oscillating local light, the local oscillator configured to respond to a signal output by the second frequency modulator.

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