MULTIBAND FLASH DETECTION SYSTEM

• US 20150138534A1
• Filed: 11/05/2014
• Published: 05/21/2015
• Est. Priority Date: 11/18/2013
• Status: Active Grant

• Current Assignee: ELTA Systems Limited (Government of Israel)
• Original Assignee: ELTA Systems Limited (Government of Israel)
• Inventors: TIDHAR, Gil
• Granted Patent: US 9,612,089 B2
• Time in Patent Office: Days
• US Class Current: 356/51
• CPC Class Codes: F41G 3/147 based on detection of a firing weapon
• CPC Class Codes: G01J 3/0224 using polarising or depolarising elements
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01J 3/447 Polarisation spectrometry
• CPC Class Codes: G01S 3/784 using a mosaic of detectors
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths

Abstract

A multiband imaging system comprising: an optical module configured for acquiring simultaneously images from a common field-of-view (FOV) scene in a short wavelength spectral band and in a long wavelength spectral band, the optical module comprising a polarizer configured for applying polarization filtering to electromagnetic radiation of the long wavelength spectral band; and a processing module configured to analyze data indicative of received irradiance distribution between the short and long wavelength spectral bands.

Claims

1. A multiband imaging system comprising:

an optical module configured for acquiring simultaneously images from a common field-of-view (FOV) scene in a short wavelength spectral band and in a long wavelength spectral band, the optical module comprising a polarizer configured for applying polarization filtering to electromagnetic radiation of the long wavelength spectral band; and

a processing module configured to analyze data indicative of received irradiance distribution between the short and long wavelength spectral bands.

2. The system according to claim 1, wherein the processing module is further configured to detect a section of the common FOV scene in which a ratio between an irradiance in the long wavelength spectral band and an irradiance in the short wavelength spectral band exceeds a predetermined threshold.

3. The system according to claim 1, wherein the short wavelength spectral band is within a visible band or UV-visible-NIR and the long wavelength spectral band is within a shortwave infrared band.

4. The system according to claim 1, wherein the long wavelength spectral band and the short wavelength spectral band do not overlap.

5. The system according to claim 1, wherein the long wavelength spectral band is approximately 1.5 μ

m to 1.7 μ

m and the short wavelength spectral band is approximately 0.5 μ

m to 0.6 μ

m.

6. The system according to claim 1, wherein the optical module comprises:

a first channel comprising a first focal plane array configured to sense electromagnetic radiation in the long wavelength spectral band;

a second channel comprising a second focal plane array configured to sense electromagnetic radiation in the short wavelength spectral band;

wherein the first and second focal plane arrays are configured so that a defined mapping links corresponding pixels of the first and second focal plane arrays, the corresponding pixels imaging similar field directions in a field of view of the imaging system when the imaging system is operated; and

wherein the polarizer is arranged in the first channel upstream of the first focal plane array.

7. The system according to claim 6, wherein the processing module is configured to compute for at least some corresponding pixels, a ratio between corresponding pixels received irradiances.

8. The system according to claim 7, wherein the processing module is further configured to detect if the ratio crosses a predefined threshold thereby detecting a field direction in the field of view of the optical detection system in which muzzle flash or detonation took place.

9. The system according to claim 8, wherein the predefined ratio is adaptive so as to operate under the Neymann-Pearson detector regime.

10. The system according to claim 8, wherein the processing module is further configured to estimate a blackbody effective temperature matching the received irradiance distribution from a detected muzzle-flash/detonation field direction.

11. The system according to claim 1, wherein the polarizer is a polarizer configured to reject electromagnetic radiation of polarization different from a linear polarization of the polarizer.

12. The system according to claim 11, wherein the linear polarization of the polarizer is vertical.

13. The system according to claim 11, wherein the imaging system further comprises a housing defining a vertical orientation of the imaging system in standard condition and the polarizer is configured so that a linear polarization of the polarizer is parallel to said vertical orientation.

14. The system according to claim 11, wherein the polarizer is configured so that a linear polarization of the polarizer stays approximately collinear with a gravitational field direction.

15. The system according to claim 11, wherein the linear polarization of the polarizer is perpendicular to a plane containing the optical axes of the first and second channels.

16. The system according to claim 1, wherein the polarizer is mounted retractably.

17. The system according to claim 16, further configured to retract the polarizer at low ambient light condition and/or when sun-reflected light is not a significant part of the overall scene irradiance.

19. The detection method according to claim 17, wherein the predefined threshold is adaptive so as to operate under the Neymann-Pearson detector regime.

20. The method according to claim 17, wherein a polarization direction of the polarizer is oriented perpendicular to a horizontal plane.

18. A detection method comprising:

simultaneously acquiring images from a common FOV scene in a short wavelength spectral band and in a long wavelength spectral band, while applying polarization filtering to electromagnetic radiation of the long wavelength spectral band, and generating data indicative of the acquired images;

analyzing said data to determine a spectral irradiance distribution between the shortwave infrared and visible spectral bands;

detecting one or more sectors of the common FOV scene for which a ratio between an irradiance in the long wavelength spectral band and an irradiance in the short wavelength spectral band exceeds a predefined threshold.