Coherent LADAR using intra-pixel quadrature detection

Patent metadata

Field	Value
Publication number	US-10000000-B2
Application number	US-201514643719-A
Country	US
Kind code	B2
Filing date	Mar 10, 2015
Priority date	Mar 10, 2015
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A frequency modulated (coherent) laser detection and ranging system includes a read-out integrated circuit formed with a two-dimensional array of detector elements each including a photosensitive region receiving both return light reflected from a target and light from a local oscillator, and local processing circuitry sampling the output of the photosensitive region four times during each sample period clock cycle to obtain quadrature components. A data bus coupled to one or more outputs of each of the detector elements receives the quadrature components from each of the detector elements for each sample period and serializes the received quadrature components. A processor coupled to the data bus receives the serialized quadrature components and determines an amplitude and a phase for at least one interfering frequency corresponding to interference between the return light and the local oscillator light using the quadrature components.

First claim

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-dimens

Assignees

• Raytheon Co

Inventors

• Marron Joseph

Classifications

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title

• G01S7/4914

  of detector arrays, e.g. charge-transfer gates · CPC title

• G01S7/4917

  superposing optical signals in a photodetector, e.g. optical heterodyne detection · CPC title

• G01S7/4865

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• G01S7/4863 Primary

  Detector arrays, e.g. charge-transfer gates · CPC title