ELECTRO-OPTIC SYSTEM FOR CROSSWIND MEASUREMENT

• US 20150345906A1
• Filed: 03/18/2015
• Published: 12/03/2015
• Est. Priority Date: 12/24/2013
• Status: Active Grant

• Current Assignee: Cubic Defense Applications Incorporated (Cubic Corporation), United States of America, As Represented by Defense Advanced Research Projects Agency
• Original Assignee: Deepak Varshneya
• Inventors: VARSHNEYA, Deepak, JEFFERS, Larry, LARSON, Samuel
• Granted Patent: US 9,347,742 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F41G 3/06 with rangefinder rangefinders per se G01C
• CPC Class Codes: F41G 3/08 with means for compensating for speed, direction, temperature, pressure, or humidity of the atmosphere measuring G01
• CPC Class Codes: F41G 3/165 using a TV-monitor
• CPC Class Codes: G01S 17/95 for meteorological use
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

An electro-optic system, e.g., mounted to a weapon, measures down range winds and a range-to-target for compensating the ballistic hit point. The system may include an optical light source, collimated to generate a laser spot on the target. The system may include a wind measurement receiver that captures laser light scattered from the target. The captured light may be modulated by atmospheric scintillation eddies, producing optical patterns which change in time and move with the crosswind. These patterns may be analyzed by a processor using covariance techniques in either the time-domain or the frequency-domain to determine path-integrated crosswinds and associated errors. Ranging is done by measuring the time of flight of the laser pulse to the target collecting the scattered signal from the target. Compensated ballistic hit point, measurement errors and other data may be displayed on a micro-display digital eyepiece, or projected onto the direct view optics (DVO) of a riflescope so as to be overlaid in real-time on the optical image of the target.

Claims

1. A system encased in a housing comprising:

an optical transmitter;

a single-aperture optical receiver including;

an objective lens that collects light, at the aperture of the optical receiver, which is scattered back from a laser spot illuminated on a target by the optical transmitter,

reimaging optics that generate a de-magnified image of an entrance pupil of the objective lens, and

an image sensor that detects the entrance pupil image;

a display device; and

a processor,

wherein;

the processor processes the detected image to obtain first and second signals, the first signal representing a summation of pixels from one region of the detected entrance pupil image as a function of time, the second signal representing a summation of pixels from the other region of the detected entrance pupil image as a function of time,

the processor processes the first and second signals to determine a time delay from which a path-weighted average crosswind toward the target is calculated, and

the processor calculates an offset aim point based on the path-weighted average crosswind, and

the offset aim point is displayed on the display device.

2. The system of claim 1, wherein each of the first and second signals represents a summation of pixels from a respective half of the detected entrance pupil image, and a central column of the detected entrance pupil image is filtered out in order to obtain the first and second signals that are free of crosstalk.

3. The system of claim 1, wherein the reimaging optics focuses a portion of the light collected by the objective lens onto the image sensor, the focused portion of the light being detected by the said image sensor as a field image separate from the detected pupil image.

4. The system of claim 3, wherein the processor uses the detected field image to perform a boresighting operation in which a laser beam of the optical transmitter is boresighted to a riflescope crosshair by first aligning an electronic crosshair with a laser spot generated by the optical transmitter, and then aligning electronic crosshair to the riflescope crosshair, the processor being able to determine an angular offset for adjusting reference coordinates of the offset aim point based on the boresighting operation.

5. The system of claim 3, wherein the processor uses the detected field image to measure a size of the laser spot illuminated on the target in real-time, wherein a frame rate used in measuring the size of the laser spot is lower than a frame rate applied to the detection of the entrance pupil image for purposes of obtaining the first and second signals.

6. The system of claim 5, wherein the processor uses the real-time measurement of the size of the laser spot to compensate the path-weighted average crosswind for environmental factors.

7. The system of claim 6, wherein the processor performs the compensation of the path-weighted average crosswind by using an empirically determined relationship between the real-time measurement of the size of the laser spot and a parameter representing an effective receiver separation, said parameter being used to calculate the path-weighted average crosswind.

8. The system of claim 6, wherein the processor performs the compensation of the path-weighted average crosswind by using an analytical equation that relates the real-time measurement of the size of the laser spot to a parameter representing an effective receiver separation, said parameter being used to calculate the path-weighted average crosswind.

9. A method employed by a system encased in a housing, comprising:

utilizing an optical transmitter in the system to illuminate a laser spot on a target;

utilizing an objective lens at an aperture of a single-aperture optical receiver in the system to collect light which is scattered back from the laser spot illuminated on the target;

utilizing reimaging optics in the single-aperture optical receiver to generate a de-magnified image of an entrance pupil of the objective lens, and

utilizing an image sensor in the single-aperture optical receiver to detect the entrance pupil image;

utilizing a processor in the system to;

process the detected image to obtain first and second signals, the first signal representing a summation of pixels from one region of the detected entrance pupil image as a function of time, the second signal representing a summation of pixels from the other region of the detected entrance pupil image as a function of time,

process the first and second signals to determine a time delay from which a path-weighted average crosswind toward the target is calculated, and

calculate an offset aim point based on the path-weighted average crosswind; and

displaying the offset aim point on a display device of the system.

10. The method of claim 9, wherein each of the first and second signals are obtained by summing pixels from a respective half of the detected entrance pupil image, and filtering out a central column of the detected entrance pupil image.

11. The method of claim 9, further comprising:

utilizing the reimaging optics are utilized to focus a portion of the light collected by the objective lens onto the image sensor, the focused portion of the light being detected by the said image sensor as a field image separate from the detected pupil image.

12. The method of claim 11, further comprising:

utilizing the processor to process to;

perform a boresighting operation based on the detected field image in which a laser beam of the optical transmitter is boresighted to a riflescope crosshair by first aligning an electronic crosshair with a laser spot generated by the optical transmitter, and then aligning electronic crosshair to the riflescope crosshair; and

determine an angular offset for adjusting reference coordinates of the offset aim point based on the boresighting operation.

13. The method of claim 11, further comprising:

utilizing the processor to measure a size of the laser spot illuminated on the target in real-time based on the detected field image, wherein a frame rate used in measuring the size of the laser spot is lower than a frame rate applied to the detection of the entrance pupil image for purposes of obtaining the first and second signals.

14. The method of claim 11, further comprising:

utilizing the processor to compensate the path-weighted average crosswind for environmental factors based on the real-time measurement of the size of the laser spot.

15. The method of claim 14, wherein the processor compensates the path-weighted average crosswind by using an empirically determined relationship between the real-time measurement of the size of the laser spot and a parameter representing an effective receiver separation, said parameter being used to calculate the path-weighted average crosswind.

16. The method of claim 14, wherein the processor compensates the path-weighted average crosswind by using an analytical equation that relates the real-time measurement of the size of the laser spot to a parameter representing an effective receiver separation, said parameter being used to calculate the path-weighted average crosswind.