Methods and systems for flash detection

• US 10,175,101 B2
• Filed: 12/21/2015
• Issued: 01/08/2019
• Est. Priority Date: 12/21/2014
• Status: Active Grant

• Current Assignee: ELTA Systems Limited (Government of Israel)
• Original Assignee: ELTA Systems Limited (Government of Israel)
• Inventors: Aphek, Ori
• Primary Examiner(s): Jo, Taeho
• Application Number:
  US14/976,215
• Publication Number:
  US 20160178433A1
• Time in Patent Office: 1,114 Days
• Field of Search: 2503381
• CPC Class Codes: F41G 3/147 based on detection of a firing weapon
• CPC Class Codes: G01J 1/0266 Field-of-view determination; Aiming or pointing of a photometer; Adjusting alignment; Encoding angular position; Size of the measurement area; Position tracking; Photodetection involving different fields of view for a single detector
• CPC Class Codes: G01J 1/1626 Arrangements with two photodetectors, the signals of which are compared
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 2003/2826 Multispectral imaging, e.g. filter imaging
• CPC Class Codes: G01J 3/0205 Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0216 using light concentrators or collectors or condensers
• CPC Class Codes: G01J 3/0289 Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01S 3/784 using a mosaic of detectors

Abstract

The present disclosure provides an optical system suitable for detecting muzzle flashes in a scene, the optical system comprising: a first optical module customized for detecting flashes at short range of the optical system by analyzing irradiance received on a first infrared sensor; a second optical module customized for detecting flashes at long range of the optical system by analyzing irradiance received on a second infrared sensor; wherein: the first and second optical modules are configured to share a common field of view and to operate independently of each other.

Claims

1. An optical system suitable for detecting muzzle flashes in a scene, the optical system comprising:

a first optical module customized for detecting flashes at short range of the optical system by analyzing irradiance received on a first infrared sensor;

a second optical module customized for detecting flashes at long range of the optical system by analyzing irradiance received on a second infrared sensor;

wherein;

the first and second optical modules are configured to share a common field of view, and

the first and second optical modules are configured so that a first maximum detection distance at which a predetermined flash is sensed by the first infrared sensor with a predetermined marginal signal to noise ratio is superior to a minimum detection distance of the second optical module at which the predetermined flash saturates the second infrared sensor so that a predetermined overlap occurs between first and second optical modules detection ranges,

wherein the optical system is configured to;

detect a flash at a short range based on detection results of the first optical module,

detect a flash at long range based on detection results of the second optical module, and

detect a flash at the predetermined overlap based on detection results of both the first and second optical modules.

2. The optical system according to claim 1, wherein the first and second optical modules are configured so that the first maximum detection distance at which the predetermined flash is sensed by the first infrared sensor with the predetermined marginal signal to noise ratio is significantly inferior to a second maximum detection distance at which the predetermined flash is sensed by the second infrared sensor with the predetermined marginal signal to noise ratio.

3. The optical system according to claim 1, wherein an instantaneous field of view of the first optical sensor is significantly superior to an instantaneous field of view of the second optical sensor.

4. The optical system according to claim 1, wherein a sampling rate of the first infrared sensor is significantly superior to a sampling rate of the second infrared sensor.

5. The optical system according to claim 1, wherein the first and second optical modules are configured so that the first and second optical modules exclusively operate concurrently.

6. The optical system according to claim 1, wherein the first and second optical modules both output detection results to an output module.

7. The optical system according to claim 6, wherein the output module is configured to:

discard the detection results of the second module for flash detection when the second infrared sensor is saturated by a flash occurring at short range of the optical system;

discard the detection results of the first module for flash detection when the signal to noise ratio of a signal produced by the first infrared sensor in response to a flash occurring at long range of the optical system is below a predetermined threshold; and

combine the detection results of the first and second modules for flash detection when a flash occurs at an overlapping range of detection of the first and second module so that a signal to noise ratio of the first module is above the predetermined threshold and the second infrared sensor is not saturated.

8. The optical system according to claim 1, wherein the first and/or second optical modules are configured for detecting flashes using one or more power threshold detection algorithms.

9. The optical system according to claim 8, wherein the one or more power threshold detection algorithms comprises either an absolute threshold detection or a adaptive average threshold detection.

10. The optical system according to claim 1, wherein the first optical module is configured for detecting flashes using one or more temporal pattern matching algorithm.

11. The optical system according to claim 10, wherein the one or more temporal pattern matching algorithms comprise correlating pre-stored target patterns to a signal produced by the first infrared sensor in response to infrared illumination.

12. The optical system according to claim 10, wherein the one or more temporal pattern matching algorithms comprise detecting a pulse shape in a signal produced by the first infrared sensor in response to infrared illumination and comparing a length of the detected pulse shape with a predetermined pulse length range.

13. The optical system according to claim 1, the first optical module and/or the second optical module are further configured to provide multi-spectral sensing of the common field of view and wherein said first and/or second optical modules are configured for detecting flashes using one or more spectral ratio algorithms.

14. The optical system according to claim 13, wherein the one or more spectral ratio algorithms comprise comparing an irradiance distribution received from one or more portions of the common field of view in several wavebands with pre-stored target irradiance distributions.

15. The optical system according to claim 1, the first infrared sensor and/or the second infrared sensor comprising a focal plane array and wherein said first and/or second optical modules are configured for discarding flashes based on a spatial extent of a flash on the focal plane array.

16. The optical system according to claim 15, wherein the second optical module is configured to discard flashes spanning over more than a predetermined number of adjacent pixels of the focal plane array.

17. The optical system according to claim 1, wherein the first infrared sensor is a first focal plane array and the first optical module further comprises first imaging optics to form an image on the first focal plane array of the common field of view.

18. The optical system according to claim 1, wherein the second infrared sensor is a second focal plane array and the second optical module further comprises second imaging optics to form an image on the second focal plane array of the common field of view.

19. The optical system according to claim 1, wherein the second infrared sensor comprises a two dimensional array of isolated sensors arranged in an insect eye configuration wherein each said sensor is associated with a collecting non imaging optics.