Method and device for optimizing the use of multiple emitters and a detector in an active remote sensing application

1. A method for remote sensing by means of a plurality of n src >1 independent diverging laser emitters comprising the steps of:

providing a laser source comprising an array of single laser sources having each a laser class and a nominal ocular hazard distance (NOHD);

setting a target time unit integration time t p ;

translating said time unit integration time into a reduced time τ p and its corresponding power increase factor η −1 so that the energy of the resulting pulse of duration τ p =η*t p remains below the acceptable eye-safety emission power of said laser at said NOHD without increasing the NOHD;

repeating for every emitter k of said plurality of n src emitters the steps of:

waiting for a given offset duration t offset,k ;

activating both the laser emitter k, with a power output corrected by η −1 , and the detector for a duration of τ p ;

deactivating said emitter k and detector after duration τ p ;

flagging emitter k to be kept off for the subsequent duration t off =t p −τ p ;

wherein the independence of the plurality of emitters is given by their geometrical arrangement around the detector such that their minimum distance from each other is at least x=2 L (restrict) tan(θ divergence /2), L (restrict) being the most restrictive distance from said emitters and θ divergence being the divergence of said emitters.

2. A method for remote sensing by means of a plurality of n src >1 independent emitters and at least one detector, comprising:

setting a target time unit integration time t p ;

translating said time unit integration time into a reduced time τ p and its corresponding power increase factor η −1 ;

repeating for every emitter k of said plurality of n src emitters the steps of:

waiting for a given offset duration t offset,k ;

activating both the laser emitter k, with a power output corrected by η −1 , and the detector for a duration of τ p ;

deactivating said emitter k and detector after duration τ p ;

flagging emitter k to be kept off for the subsequent duration t off =t p −τp;

wherein the method delays the activation of at least one of the laser emitters and the photo-sensitive detector by an additional amount of t delay =max[(η preceding −1)t p , 0], with η preceding being the inverse of the power increase factor of a preceding acquisition.

3. A method according to claim 2 in which said target integration time unit t p results from a target frame rate.

4. A method according to claim 2 wherein during the off-time t off =t p −τ p communication is exchanged with an external device ( 14 ).

5. A method according to claim 4 wherein said communication updates configurations.

6. A method according to claim 2 wherein the independence of the plurality of emitters is given by their geometrical arrangement around the detector such that their minimum distance from each other is at least x=2 L (restrict) tan(θ divergence /2), L (restrict) being the most restrictive distance from said emitters and θ divergence being the divergence of said emitters.

7. A method according to claim 2 wherein the translation of said time unit integration time t p into a reduced time τ p is obtained by means of a look-up-table (LUT) listing pre-calculated values.

8. A method according to claim 2 wherein the translation of said time unit integration time t p into a reduced time τ p is obtained by calculating it continuously according to the time domain and/or the spectral region.

9. A method according to claim 2 wherein the translation of said time unit integration time into a reduced time τ p is obtained by providing coarse steps from a look-up-table (LUT) listing pre-calculated values and by calculating interpolated value.

10. A method according to claim 2 wherein it operates in a continuous acquisition mode set up to acquire frames of t p integration time each in order to obtain a frame rate 1/t p .

11. A method according to claim 2 wherein it operates in such a way that it acquires a single acquisition following a trigger signal and then waits for a subsequent trigger signal.

12. A method according to claim 11 wherein, if the trigger signal arrives during the idle mode duration t off , said trigger signal is ignored or delayed until said duration has timed out.

13. A device for remote sensing by means of a plurality of n src ≥>1 independent emitters and at least one detector, comprising n src laser emitters, a photo-sensitive detector and a logic circuit controlling the n src laser emitters and the photo-sensitive detector and a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon executable by a processor to perform actions comprising:

setting a target time unit integration time t p ;

translating said time unit integration time into a reduced time τ p and its corresponding power increase factor η −1 ;

repeating for every emitter k of said plurality of n src emitters the steps of:

waiting for a given offset duration t offset,k ;

activating both the laser emitter k, with a power output corrected by η −1 , and the detector for a duration of τ p ;

deactivating said emitter k and detector after duration τ p ;

flagging emitter k to be kept off for the subsequent duration t off =t p −τ p ;

wherein the device comprises means for delaying the activation of at least one of the laser emitters and the photo-sensitive detector by an additional amount of t delay =max[(η preceding −η)t p , 0], with η preceding being the inverse of the power increase factor of a preceding acquisition.

14. A device according to claim 13 wherein said target integration time unit results from a target frame rate.

15. A device according to claim 13 wherein during the off-time t off =t p −τ p communication is exchanged with an external device ( 14 ).

16. A device according to claim 15 wherein said communication updates configurations.

17. A device according to claim 13 wherein the n src emitters are arranged around the photo-sensitive detector such that their minimum distance from each other is at least x=2 L (restrict) tan(θ divergence /2), L (restrict) being the most restrictive distance from said emitters and θ divergence being the divergence of said emitters.

18. A device according to claim 13 wherein the translation of said time unit integration time t p into a reduced time τ p is obtained by means of a look-up-table (LUT) listing pre-calculated values.

19. A device according to claim 13 wherein the translation of said time unit integration time t p into a reduced time τ p is obtained by calculating it continuously according to the time domain and/or the spectral region.

20. A device according to claim 13 wherein the translation of said time unit integration time t p into a reduced time τ p is obtained by providing coarse steps from a look-up-table (LUT) listing pre-calculated values and by calculating interpolated value.

21. A device according to claim 13 wherein it operates in a continuous acquisition mode set up to acquire frames of t p integration time each in order to obtain a frame rate 1/t p .

22. A device according to claim 13 wherein it operates in such a way that it acquires a single acquisition following a trigger signal and then waits for a subsequent trigger signal.

23. A device according to claim 22 wherein, if the trigger signal arrives during the idle mode duration t off , said trigger signal is ignored or delayed until said duration has timed out.

24. A device according to claim 22 wherein it further comprises an external device sending said trigger signal.

25. A device according to claim 24 wherein said external device is a screen, a projector, a computer, or a server.

26. A method for remote sensing by means of a plurality of n src >1 independent diverging laser emitters comprising the steps of:

providing a laser source comprising an array of single laser sources having each a laser class and a nominal ocular hazard distance (NOHD);

setting a target time unit integration time t p ;

translating said time unit integration time into a reduced time τ p and its corresponding power increase factor η −1 so that the energy of the resulting pulse of duration τ p =η*t p remains below the acceptable eye-safety emission power of said laser at said NOHD without increasing the NOHD;

repeating for every emitter k of said plurality of n src emitters the steps of:

waiting for a given offset duration t offset k ;

activating both the laser emitter k, with a power output corrected by η −1 , and the detector for a duration of τ p ;

deactivating said emitter k and detector after duration τ p ;

flagging emitter k to be kept off for the subsequent duration t off =t p −τp;

configured so that at least two emitted light beams overlap at least partially and at least one detector having a field of view that is the same as the total subtended angle of the overlap of said emitted light beams.