Method for viewing a laser spot

Patent metadata

Field	Value
Publication number	US-10600200-B2
Application number	US-201615745881-A
Country	US
Kind code	B2
Filing date	Jul 11, 2016
Priority date	Jul 21, 2015
Publication date	Mar 24, 2020
Grant date	Mar 24, 2020

Abstract

Method for viewing a laser spot included in a multispectral image representing an optical field composed of pixels including a plurality of components, the laser spot being produced by a laser pointer and having a wavelength taking values in a range of wavelengths dependent on operating temperatures of the laser pointer. The method includes: obtaining a multispectral image in which each component corresponds to the same instant of acquisition and represents a spectral band in a plurality of spectral bands covering continuously a spectral domain comprising said range of wavelengths; applying a contrast-accentuation procedure to a subpart of the multispectral image comprising the laser spot in order to obtain a subpart in which a contrast between the laser spot and a background is improved; and generating an image allowing display of the laser spot using information obtained following the application of said procedure.

First claim

The invention claimed is:

1. A method for viewing a laser spot included in a multispectral image, comprising a plurality of components and representing an optical field, the laser spot being produced by a laser device and having a wavelength taking values in a range of wavelengths dependent on operating temperatures of the laser device, wherein the method comprises:
obtaining a multispectral image in which each component corresponds to the same instant of acquisition and represents a spectral band in a plurality of spectral bands covering continuously a spectral domain comprising said range of wavelengths;
applying a contrast-accentuation procedure to a first window corresponding to a subpart of the multispectral image comprising the laser spot, the contrast-accentuation procedure comprising:
defining in the first window a first mask suitable for containing pixels of the multispectral image corresponding to the laser spot and a second mask suitable for containing pixels of the multispectral image not corresponding to the laser spot; and
determining a vector representing a Fischer projection direction making it possible to accentuate a contrast between the pixels of the first and second masks and applying a projection according to said vector to the first window in order to obtain a second window;
if the laser spot appears in the second window, selecting a first spectral band offering the best contrast between the pixels of the first and second masks using at least one result of the contrast-accentuation procedure and forming a third window from a component of the first window corresponding to the first spectral band selected;
generating an image allowing display of the laser spot by inserting the third window at a position corresponding to the first window in a receiving image representing the optical field.

2. The method according to claim 1 , wherein a comparison of a value representing a contrast between the pixels of the first and second masks in the second window with a first threshold makes it possible to determine whether the laser spot appears in the second window.

3. The method according to claim 1 , wherein the values of coordinates of said vector are values of coordinates normalized over a predefined range of values.

4. The method according to claim 1 , further comprising selecting a second spectral band, said second spectral band being associated with a contrast value between the pixels of the first and second masks lower than a second threshold and forming a fourth window from a component of the first window corresponding to the second spectral band selected, the image allowing viewing of the laser spot being generated by inserting the third or fourth window in a receiving image representing the optical field.

5. The method according to claim 1 , wherein characteristics of the first spectral band allow to determine a laser device type.

6. A computer program product embodied in a non-transitory computer readable medium, the computer program product comprising instructions for the implementation, by a device, of the method according to claim 1 , when said program is executed by a processor of said device.

7. A non-transitory storage medium storing a computer program comprising instructions for the implementation, by a device, of the method according to claim 1 , when said program is executed by a processor of said device.

8. A non-transitory storage medium storing a computer program comprising instructions for the implementation, by a device, of the method according to claim 1 , when said program is executed by a processor of said device.

9. The method according to claim 1 , wherein the multispectral image is generated from a plurality of thumbnails representing the optical field having the same acquisition instant and harmonised spatially, each thumbnail corresponding to a spectral band from the plurality of spectral sub-bands.

10. The method according to claim 9 , wherein at least two thumbnails from the plurality of thumbnails correspond to the same spectral band and represent a light beam corresponding to said spectral band polarised according to a different polarisation, so that, when the first spectral band offering the best contrast between the pixels of the first and second masks is selected, the polarisation offering the best contrasts between the pixels of the first and second masks is also selected.

11. A method for viewing a laser spot included in multispectral images acquired with a predefined image frequency, wherein the method comprises:
executing the method according to claim 1 for each multispectral image.

12. A computer program product embodied in a non-transitory computer readable medium, the computer program product comprising instructions for the implementation, by a device, of the method according to claim 11 , when said program is executed by a processor of said device.

13. The method according to claim 1 , wherein values representing a contrast between the pixels of the first and second masks in each spectral band are used for selecting the spectral band offering the best contrast between the pixels of the first and second masks, said values representing a contrast comprising values of coordinates of said vector.

14. The method according to claim 13 , wherein said values representing a contrast further comprise signal-to-noise ratio values calculated for each spectral band.

15. The method according to claim 13 , wherein a selection value is calculated for each spectral band from each value representing a contrast corresponding to said spectral band, the first spectral band being selected by taking a spectral band from the plurality of spectral bands associated with the highest selection value among the selection values calculated.

16. The method according to claim 1 , wherein the contrast-accentuation procedure is applied to a plurality of first windows corresponding to different subparts of the multispectral image, at least one first window from said plurality comprising the laser spot, and in that a second window is selected in accordance with a predefined criterion from the second windows obtained during each application of the contrast-accentuation procedure, the second window selected being used for selecting the first spectral band.

17. The method according to claim 16 , wherein a position of at least one first window is defined in a multispectral image, referred to as the current image, according to a position of a second window in which the laser spot appears in a multispectral image preceding the current image.

18. The method according to claim 17 , wherein a frequency of the laser spot is determined over a plurality of successive multispectral images, the frequency of the laser spot being used for determining the type of laser device.

19. The method according to claim 17 , wherein the image allowing viewing of the laser spot is generated by alternating an insertion of the third or fourth window in a receiving image representing the optical field with a predefined alternation frequency less than or equal to the predefined image frequency.

20. A device allowing viewing of a laser spot included in a multispectral image, comprising a plurality of components and representing an optical field, the laser spot being produced by a laser device and having a wavelength taking values in a range of wavelengths dependent on operating temperatures of the laser device, wherein the device comprises circuitry adapted for:
obtaining a multispectral image in which each component corresponds to the same

Assignees

• Safran Electronics & Defense

Inventors

• Roux Nicolas
• Foubert Philippe
• Patry Philippe
• Guiset Pierrick
• Touati Thierry

Classifications

• G06T2207/30212

  Military · CPC title

• G06T2207/20212

  Image combination · CPC title

• G06T2207/10036

  Multispectral image; Hyperspectral image · CPC title

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title

• G06T5/20

  using local operators · CPC title