Image processing for launch parameters measurement of objects in flight

• US 9,171,211 B2
• Filed: 09/20/2013
• Issued: 10/27/2015
• Est. Priority Date: 09/20/2013
• Status: Active Grant

• Current Assignee: Rapsodo Pte., Ltd.
• Original Assignee: Rapsodo Pte., Ltd.
• Inventors: Keat, Kelvin Yeo Soon, Okur, Batuhan
• Primary Examiner(s): Tabatabai, Abolfazl
• Application Number:
  US14/032,949
• Publication Number:
  US 20150262011A1
• Time in Patent Office: 767 Days
• Field of Search: 382/103, 382/107, 382/236, 348/135, 348139169-172, 348/352
• US Class Current: 1/1
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G01P 3/38 using photographic means
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: G06T 3/067 Reshaping or unfolding 3D tree structures onto 2D planes
• CPC Class Codes: G06T 3/40 Scaling of whole images or parts thereof, e.g. expanding or contracting
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51

Abstract

An example embodiment includes a method of measuring launch parameters of an object in flight. The method includes capturing images of an object in flight. A radius of the object and a center of the object are identified in each of the images. A velocity, an elevation angle, and an azimuth angle are calculated based on the radius of the object, the center of the object, and pre-measured camera alignment values. The method further includes cropping the images to a smallest square that bounds the object and flattening the images from spherical representations to Cartesian representations. The method also includes converting the Cartesian representations to polar coordinates with a range of candidate centers of rotations. Based on a fit of the polar image pair, the spin axis and spin rate are measured.

Claims

1. A method of measuring launch parameters of an object in flight, the method comprising:

capturing a plurality of images of an object in flight;

identifying a radius of the object and a center of the object in each of the plurality of images;

calculating a velocity, an elevation angle, and an azimuth angle based on the radius of the object, the center of the object, and pre-measured camera alignment values;

cropping the plurality of images to a smallest square that bounds the object;

flattening the plurality of images from spherical representations to Cartesian representations;

converting the Cartesian representations to polar coordinates with a range of candidate centers of rotation; and

based on a fit of the polar image pair, measuring the spin axis and spin rate.

2. The method of claim 1, wherein the identifying includes setting a contrast threshold selected to enable identification of the radius of the object.

3. The method of claim 2, wherein the contrast threshold is set such that the radius of the object is identifiable in bright conditions.

4. The method of claim 1, further comprising correcting one or more of the velocity, the elevation angle, and the azimuth angle based on a measured system tilt.

5. The method of claim 1, wherein the measuring includes correcting a first perspective bias by accommodating for camera displacement.

6. The method of claim 5, wherein the measuring includes correcting a second perspective bias by accommodating for azimuth angle.

7. The method of claim 1, further comprising extracting sufficient pixels from the plurality of images for marker matching.

8. The method of claim 7, wherein the marker matching includes identifying one or more natural markers on the object.

9. The method of claim 8, further comprising fitting a polar transform of an image pair in one dimension for measuring the spin axis.

10. The method of claim 1, further comprising performing a manufacture calibration.

11. The method of claim 10, further comprising performing an auto calibration while capturing the plurality of images.

12. A launch monitor system comprising:

two cameras; and

a processor configured to execute computer instructions to cause a computing system to perform operations for measuring launch parameters of an object in flight, the operations comprising;

capturing a plurality of images of an object in flight;

identifying a radius of the object and a center of the object in each of the plurality of images;

calculating a velocity, an elevation angle, and an azimuth angle based on the radius of the object, the center of the object, and pre-measured camera alignment values;

cropping the plurality of images to a smallest square that bounds the object;

flattening the plurality of images from spherical representations to Cartesian representations;

converting the Cartesian representations to polar coordinates with a range of candidate centers of rotation; and

based on a fit of the polar image pair, measuring the spin axis and spin rate.

13. The launch monitor system of claim 12, further comprising:

a field programmable gate array configured to interface with the two cameras;

a communication module configured to wirelessly transmit the plurality of images;

an optical triggering module configured to trigger the capturing of the images; and

an illumination source, the illumination source including a light emitting diode (LED) module configured to illuminate the object.

14. The launch monitor system of claim 12, wherein the identifying includes setting a contrast threshold selected to enable identification of the radius of the object.

15. The launch monitor system of claim 14, wherein the contrast threshold is set such that the radius of the object is identifiable in bright conditions.

16. The launch monitor system of claim 12, wherein the operations further comprise correcting one or more of the velocity, the elevation angle, and the azimuth angle based on a measured system tilt.

17. The launch monitor system of claim 12, wherein the measuring includes:

correcting a first perspective bias by accommodating for camera displacement; and

correcting a second perspective bias by accommodating for azimuth angle.

18. The launch monitor system of claim 12, wherein the operations further comprise extracting sufficient pixels from the plurality of images for marker matching, wherein the marker matching includes identifying one or more natural markers on the object.

19. The launch monitor system of claim 12, wherein the operations further comprise fitting a polar transform of an image pair in one dimension for measuring the spin axis.

20. The launch monitor system of claim 12, wherein the operations further comprise:

performing a manufacture calibration; and

performing an auto calibration while capturing the plurality of images.