PASSIVE ELECTRO-OPTICAL TRACKER
First Claim
1. A projectile tracking device comprising:
- detector apparatus for converting into electronic form images in at least two infrared wavebands;
optics for projecting onto the detector apparatus an image of a scene in the at least two infrared wavebands;
logic operative to obtain from the images in electronic form apparent brightnesses of the projectile at the optics in at least two infrared wavebands;
logic operative to estimate the speed of the projectile varying over time from the varying ratio at successive times of the measured apparent brightnesses in said at least two infrared wavebands;
logic operative to obtain from the images in electronic form an azimuth of the projectile from the optics at successive times; and
logic operative to estimate the direction of the trajectory of the projectile from the measured azimuths in combination with the ratio between the measured apparent brightnesses.
1 Assignment
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Accused Products
Abstract
A passive electro-optical tracker uses a two-band IR intensity ratio to discriminate high-speed projectiles and obtain a time-varying speed estimate from their time-varying temperature, as well as determining the trajectory back to the source of fire. In an omnidirectional system a hemispheric imager with an MWIR spectrum splitter forms two CCD images of the environment. Various methods are given to determine the azimuth and range of a projectile, both for clear atmospheric conditions and for nonhomogeneous atmospheric conditions. One approach uses the relative intensity of the image of the projectile on the pixels of a CCD camera to determine the azimuthal angle of trajectory with respect to the ground, and its range. A second uses a least squares optimization over multiple frames based on a triangle representation of the smeared image to yield a real-time trajectory estimate.
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Citations
20 Claims
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1. A projectile tracking device comprising:
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detector apparatus for converting into electronic form images in at least two infrared wavebands; optics for projecting onto the detector apparatus an image of a scene in the at least two infrared wavebands; logic operative to obtain from the images in electronic form apparent brightnesses of the projectile at the optics in at least two infrared wavebands; logic operative to estimate the speed of the projectile varying over time from the varying ratio at successive times of the measured apparent brightnesses in said at least two infrared wavebands; logic operative to obtain from the images in electronic form an azimuth of the projectile from the optics at successive times; and logic operative to estimate the direction of the trajectory of the projectile from the measured azimuths in combination with the ratio between the measured apparent brightnesses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A nontransitory computer readable storage medium carrying a computer program that will cause a suitable general purpose computer to carry out a method comprising:
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measuring apparent brightnesses of a projectile at an observing location in at least two infrared wavebands at successive times; estimating the speed of the projectile as a function of time from the ratio of the apparent brightnesses measured in at least two infrared wavebands at successive times; measuring an azimuth of the projectile from the observing location at successive times; and estimating the direction of the trajectory of the projectile from the measured azimuths in combination with the ratios at different times between the measured apparent brightnesses.
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13. A method of tracking a projectile in air, comprising:
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measuring apparent brightnesses of the projectile at an observing location in at least two infrared wavebands at successive times; estimating the speed of the projectile as a function of time from the ratio of the apparent brightnesses measured in the at least two infrared wavebands at successive times; measuring an azimuth of the projectile from the observing location at successive times; and estimating the direction of the trajectory of the projectile from the measured azimuths in combination with the ratios between the measured apparent brightnesses. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification