Device and method for object illumination and imaging using light pulses

• US 20030193981A1
• Filed: 05/28/2003
• Published: 10/16/2003
• Est. Priority Date: 06/05/2001
• Status: Active Grant

• Current Assignee: University of Florida (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Matveev, Oleg
• Granted Patent: US 7,045,783 B2
• Time in Patent Office: Days
• US Class Current: 372/69
• CPC Class Codes: B60Q 1/14 having dimming means
• CPC Class Codes: B60Q 1/1415 Dimming circuits
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G01S 7/51 Display arrangements

Abstract

A reduced glare imaging system for motor vehicles which includes at least one light source capable of modulation. The system also includes a synchronization system which has structure for obtaining a time reference, and a trigger for modulating emissions from the light source. The trigger initiates emission of periodic light pulses from the light source at fixed times relative to the time reference. The fixed times can be randomly selected. The light pulses can have a wavelength in the range of 0.19 μm to 5 μm.

Claims

1. A reduced glare imaging system for motor vehicles, comprising:

at least one pulsed light source;

a synchronization system including structure for obtaining a time reference;

a trigger for modulating emissions from said light source, wherein said trigger initiates emission of periodic light pulses from said light source, said periodic light pulses emitted at fixed times relative to said time reference; and

an imaging device for receiving scattered light from objects being illuminated by said pulsed light source, wherein said imaging device is gated to receive said scattered light during defined gating periods.

2. The system of claim 1, wherein said light pulses have a wavelength in the spectrum range of 0.19 μ

m to 5 μ

m.

3. The system of claim 1, wherein said light pulses have a wavelength in the spectrum range of 400 nm to 750 nm.

4. The system of claim 3, wherein an average power of said light pulses is less than at least one value selected from the group consisting of 10 W, 1 W, 500 mW, 100 mW, 10 mW, 1 mW and 500 μ

W.

5. The system of claim 1, further comprising a display for displaying images contained in said received scattered light.

6. The system of claim 1, wherein said gating periods each have a duration approximately equal to the sum of (2D_S/c)+Δ

T_PULSE, where Δ

T_PULSE is a duration of at least one of said periodic light pulses, D_S is a maximum desired observation range, and c is the speed of light.

7. The system of claim 1, wherein said gating periods each have a duration approximately equal to the sum of 2(D_B−

D_L)/c+Δ

T_PULSE, where Δ

T_PULSE is a duration of at least one of said periodic light pulses, D_L is a distance correlating to a desired observation range minimum, D_B is a distance correlating to a desired observation range maximum, and c is the speed of light.

8. The system of claim 1, wherein each of said gating periods commences when a correlating one of said periodic light pulses begins.

9. The system of claim 1, wherein each of said gating periods commences at a time approximately equal to t_i+2D_L/c and finishes at a time approximately equal to 2D_B/c+Δ

T_PULSE, where t_i=a time when a correlating one of said periodic light pulses begins, D_L is a distance correlating to a desired observation range minimum, D_B is a distance correlating to a desired observation range maximum, and c is the speed of light.

10. The system of claim 1, wherein said imaging device comprises an imaging detector for obtaining object images, wherein said imaging detector detects object images during each of said defined gating periods.

11. The system of claim 10, wherein said imaging detector has a luminosity-resolving power product of at least 10⁴ cm² sr.

12. The system of claim 10, wherein said imaging detector is at least one item selected from the group consisting of an atomic vapor ultranarrowband imaging detector, a molecular vapor ultranarrowband imaging detector, an atomic magnetooptical filter, a molecular magnetooptical filter, a spectral hole burning filter, an image intensifier, an electron bombardment charged coupled device, and a resonance ionization imaging detector.

13. The system of claim 1, further comprising a light filter, wherein said light filter is at least one item selected from the group consisting of colored glass, an acousto-optic filter, a Liot type filter, an atomic resonance fluorescence imaging monochromator, a magneto-optical filter, and an interference filter.

14. The system of claim 1, wherein said fixed times are defined by time slots, each time slot having a duration equal to at least an amount of time selected from the group consisting of a gating period and a period between light pulses.

15. The system of claim 14, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 100 and said duration of said time slot.

16. The system of claim 14, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 1,000 and said duration of said time slot.

17. The system of claim 14, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 10,000 and said duration of said time slot.

18. The system of claim 1, wherein said fixed times are a arbitrarily selected.

19. The system of claim 1, wherein said fixed times are predetermined.

20. The system of claim 1, wherein a period between light pulses is constant for a plurality of vehicles.

21. The system of claim 1, wherein a period between light pulses is constant for all vehicles having imaging systems which are tuned to a light frequency which is common to all of said vehicles.

22. The system of claim 1, wherein a duration of said gating period is constant for a plurality of vehicles.

23. The system of claim 1, wherein said light source comprises at least one of a pulsed laser, a light emitting diode and an electrodeless radio frequency excited lamp.

24. The system of claim 23 wherein said laser is a Q-switched laser.

25. The system of claim 1, wherein said time reference is a wirelessly transmitted timing signal.

26. The system of claim 1, wherein said time reference is a signal transmitted from at least one of a global positioning satellite system, a global navigation satellite system and an earth based time station.

27. The system of claim 1, wherein said light source is configured as at least one device selected from the group consisting of a vehicle headlight and a head-mounted pulsed illuminator.

28. The system of claim 1, wherein said trigger provides a particular time interval for said fixed times, whereby said imaging system emits said light pulses during said time interval to signify an emergency condition.

29. The system of claim 28, whereby said emission of said light pulses during said particular time interval are detectable by an emergency service.

30. The system of claim 28, wherein said imaging system is mounted to a vehicle and said trigger provides said particular time interval for said fixed times upon said vehicle being operated while not being supplied a predetermined item.

31. The system of claim 30, wherein said predetermined item comprises a unique key or a password.

32. A reduced glare imaging system for motor vehicles, comprising:

at least one pulsed light source which generates light having a in the range of 0.19 μ

m to 5 μ

m;

a synchronization system including structure for obtaining a time reference;

a trigger for modulating emissions from said light source, wherein said trigger initiates emission of periodic light pulses from said light source, said periodic light pulses emitted at fixed times relative to said time reference; and

an imaging device for receiving light scattered from objects illuminated by periodic light pulses.

33. The reduced glare imaging system of claim 32, wherein said light is emitted in a visible light spectrum with an irradiance which is less than an irradiance of light emitted by a typical low beam headlight.

34. A motor vehicle, comprising:

an illumination system mounted to said vehicle, said illumination system including;

at least one light source capable of modulation;

a synchronizing system including structure for obtaining a time reference; and

a trigger for modulating emissions from said light source, wherein said trigger directs emission of periodic light pulses from said light source, said periodic light pulses emitted at fixed times relative to said time reference.

35. A method of providing reduced glare imaging for motor vehicles, comprising the steps:

receiving a time reference;

triggering a light source to emit periodic light pulses at fixed times relative to said time reference;

during gating periods correlating to said light pulses, receiving light scattered from objects illuminated by said periodic light pulses; and

displaying images contained in said scattered light.

36. The method of claim 35, wherein said light pulses have a wavelength in at least one of the ranges of 0.19 μ

m to 5 μ

m.

37. The method of claim 35, wherein said light pulses have a wavelength in the spectrum range of 400 nm to 750 nm.

38. The method of claim 37, wherein an average power of said light pulses is less than at least one value selected from the group consisting of 1 W, 500 mW, 100 mW, 10 mW, 1 mW and 500 μ

W.

39. The method of claim 35, further comprising the step of defining said gating periods to be approximately equal to the sum of (2D_S/c)+Δ

T_PULSE, where Δ

T_PULSE is a duration of at least one of said periodic light pulses, D_S is a desired illumination distance for the imaging system'"'"'s field of observation, and c is the speed of light.

40. The method of claim 35, wherein said gating periods each have a duration approximately equal to the sum of [2(D_B−

D_L)/c+Δ

T_PULSE], where Δ

T_PULSE is a duration of at least one of said periodic light pulses, D_L is a distance correlating to a desired observation range minimum, D_B is a distance correlating to a desired observation range maximum, and c is the speed of light.

41. The method of claim 35, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 100 and said duration of said time slot.

42. The method of claim 35, wherein each of said gating periods commences when a correlating one of said periodic light pulses begins.

43. The method of claim 35, wherein each of said gating periods commences at a time approximately equal to t_i+2D_L/c and finishes at a time approximately equal to 2D_B/c+Δ

T_PULSE, where t_i=a time when a correlating one of said periodic light pulses begins, D_L is a distance correlating to a desired observation range minimum, D_B is a distance correlating to a desired observation range maximum, and c is the speed of light.

44. The method of claim 35, wherein said fixed times are defined by time slots, each time slot having a duration equal to at least an amount of time selected from the group consisting of a gating period and a period between light pulses.

45. The method of claim 44, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 100 and said duration of said time slot.

46. The method of claim 44, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 1,000 and said duration of said time slot.

47. The method of claim 44, wherein a duration of time elapsing between a first one of said periodic light pulses and a next one of said periodic light pulses is greater than the product of 10,000 and said duration of said time slot.

48. The method of claim 35, wherein said fixed times are arbitrarily selected.

49. The method of claim 35, wherein said fixed times are predetermined.

50. The method of claim 35, wherein said time reference is a wirelessly transmitted timing signal.

51. The method of claim 35, wherein said time reference is a signal transmitted from at least one of a global positioning satellite system, a global navigation satellite system and an earth based time station.