Optical method and device for measuring a distance from an obstacle

• US 7,495,746 B2
• Filed: 09/18/2007
• Issued: 02/24/2009
• Est. Priority Date: 10/24/2006
• Status: Expired due to Fees

• Current Assignee: C.R.F. Societa Consortile Per Azioni
• Original Assignee: C.R.F. Societa Consortile Per Azioni
• Inventors: Repetto, Piermario, Bernard, Stefano, Pallaro, Nereo
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Ratcliffe; Luke D
• Application Number:
  US11/898,965
• Publication Number:
  US 20080094607A1
• Time in Patent Office: 525 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 515, 356 6- 22
• US Class Current: 356/4.07
• CPC Class Codes: G01S 17/46 Indirect determination of position data

Abstract

An optical device to measure the distance between the device itself and an obstacle/object comprising a unit to emit radiation including an aligned series of sources of radiation coupled to a series of arrangements of lenses to guide the radiation emitted by the sources. An optical acquisition unit comprising a matrix of photodetectors has a field of view including the scene in front of the optical device and including the obstacle. The signals leaving the acquisition unit are sent to a control and processing unit for calculation of the distance from the obstacle. The unit for the emission and conformation of the radiation emits a beam having a transverse section of a form elongated along an axis that is progressively rotated for transverse sections of the beam progressively more distant from the emission unit. In this manner, the distance of the obstacle may be calculated on the basis of the angular position of the section of the beam intercepted by the obstacle, as acquired by said acquisition unit.

Claims

1. Optical device for measuring the distance from an obstacle, including:

a unit to emit a radiation and to conform the irradiated beam,

an acquisition unit to acquire information relating to the image of the scene situated in front of said optical device,

an electronic control and processing unit to receive signals leaving said acquisition unit in order to determine the distance between said optical device and an obstacle which is part of the scene in front of the optical device,

wherein said emission unit is predisposed to emit a beam having a transverse section of a form elongated along an axis, said axis being progressively rotated for transverse sections of the beam progressively more distant from the emission unit, in such a manner that the distance of the optical device from one or more obstacles illuminated by the beam is calculated by said electronic control and processing unit as a function of the angular position of said axis on the section of the beam intercepted by the obstacle, as acquired by said means of acquisition.

2. Optical device according to claim 1, wherein said unit for the emission of radiation consists of a linear matrix of sources arranged along a predetermined axis.

3. Optical device according to claim 2, wherein the sources are laser diodes.

4. Optical device according to claim 3, wherein said laser diodes have emission peak in the region of the spectrum of the near infrared.

5. Optical device according to claim 2, wherein said sources are light emitting diodes (LEDs).

6. Optical device according to claim 5, wherein said light emitting diodes have emission peak in the region of the spectrum of the near infrared.

7. Optical device according to claim 1, wherein said unit for the emission of radiation comprises a single source extended in one direction, for example a horizontal or a vertical direction.

8. Optical device according to claim 7, wherein said single extended source has emission peak in the region of the spectrum of the near infrared.

9. Optical device according to claim 1, wherein said unit for emission and conformation of the beam comprises a plurality of arrangements of lenses, each of said arrangements of lenses being combined with a single light source, said arrangements of lenses being capable of collimating and guiding a beam having a transverse section of a form elongated along an axis, said axis being progressively rotated for transverse sections of the beam that are progressively more distant from the emission unit.

10. Optical device according to claim 1, wherein said unit for emission and conformation of the beam comprises a plurality of lenses, each of said lenses being combined to a single light source, said lenses being capable of coordinating and guiding a beam having a transverse section of a form elongated along an axis, said axis being progressively rotated for transverse sections of the beam progressively at a greater distance from the emission unit.

11. Optical device according to claim 1, wherein unit for emission of radiation comprises a single source of radiation of the point-form type coupled to optical means, capable of extending the dimension of the source along a predetermined axis and of collimating the light emitted by said source in a direction substantially perpendicular to said linear dimension, and to further optical means capable of forming an outgoing beam according to the characteristics of claim 1.

12. Optical device according to claim 1, wherein said unit for the emission of radiation comprises a single source of radiation of the point-form type coupled to optical means capable of extending the dimension of the source along a predetermined axis and of forming an outgoing beam (6) according to the characteristics of claim 1.

13. Optical device according to claim 1, in which said acquisition unit comprises one or more photodetectors whose field of view comprises the scene situated in front of the optical device.

14. Optical device according to claim 11, wherein said control and processing unit is predisposed to acquire the signals leaving said acquisition unit and to recognise the form of said section of the beam intercepted by said one or more obstacles through image recognition algorithms, as well as to calculate the distance between said optical device and said one or more obstacles included in the field of view of said acquisition unit.

15. Optical device according to claim 1, wherein said control and processing unit is predisposed to synchronise the emission of radiation from said emission unit with said acquisition unit in order to increase the ratio between useful signal and background signal, as well as the ratio between signal and noise.

16. Optical device according to claim 1, wherein said acquisition unit includes means to filter the radiation reflected from the obstacles and incident on said acquisition means so as to transmit only the components of the spectrum corresponding to the radiation emitted from said emission unit, in order to increase the ratio between useful signal and background signal, as well as that between signal and noise.

17. Optical device according to claim 13, wherein said acquisition unit comprises a single photodetector, a diaphragm and optics capable of forming an image of said section of the beam intercepted by said obstacle on said photo detector.

18. Optical device according to claim 13, wherein said acquisition unit comprises a matrix of photodetectors and optics (an arrangement of lenses) capable of forming an image of said section of the beam intercepted by said obstacle on said matrix of photodetectors.

19. Optical device according to claim 13, wherein said acquisition unit comprises a matrix of photodetectors, a diaphragm and optics (an arrangement of lenses) capable of forming an image of said section of the beam intercepted by said obstacle on said matrix of photodetectors.

20. Optical device according to claim 13, wherein said acquisition unit comprises a matrix of single photodetectors (pixels), to each of which is associated a diaphragm, said diaphragm consisting of a slit of a substantially linear form with axis arranged along a different predetermined direction for each of said pixels, and optics capable of forming an image of said section of the beam intercepted by said obstacle on the pixel associated to it.

21. Optical device according to claim 1, wherein said radiation unit is predisposed to emit a number of beams in different directions in space, each of said beams having a transverse section of a form elongated along an axis, said axis being progressively rotated for transverse sections of the beam progressively more distant from the emission unit.

22. Optical device according to claim 21, wherein to each of said beams is associated a photodetector or a matrix of photodetectors, according to any of the claims 17, 18, 20.

23. Optical device according to claim 1, in which the sensitive area of each of said detectors is of a linear form and extended along an axis oriented in a predetermined manner.

24. Optical device according to claim 18, wherein said control and processing unit is predisposed to calculate the distance of said obstacle by detecting the intensity of the signals associated to different pixels and comparing them one to another.

25. Optical device according to claim 18, wherein said matrix of photodetectors is a 2×

2 matrix.

26. Optical device according to claim 18, wherein said matrix of photodetectors is 3×

3 matrix.

27. Optical device according to claim 20, wherein said control and processing unit is predisposed to acquire the signal leaving said acquisition unit, to determine the pixel that generates the greatest light intensity and to associate to said determined pixel a distance value between said optical device and an obstacle.

28. Optical device according to claim 21, in which said unit to emit and conform the beam comprises optical means positioned downstream of the means to conform the beam and capable of multiplying the light distribution formed by said means to conform the beam.

29. Optical device according to claim 28, wherein said optical means comprises a diffraction grating.

30. Optical device according to claim 28, wherein said optical means is manufactured through optical holography.

31. Optical device according to claim 28, wherein said control and processing unit is predisposed to extrapolate the distance measurement on the basis of an a priori knowledge of the angle of inclination of the segment, determined by the conical diffraction effect.

32. Method to measure the distance of an obstacle, in which:

a unit is predisposed to emit radiation and to conform the irradiated beam,

the image in front of said emission unit is acquired,

the distance between said emission unit and an obstacles part of the scene thus acquired is calculated,

wherein the beam emitted by said emission unit is conformed in such a manner as to have a transverse section of a form elongated along an axis that is progressively rotated for transverse sections of the beam progressively more distant from the emission unit,

in such a manner that the distance of the emission unit from an obstacle illuminated by the beam is calculated as a function of the angular position of the section of beam intercepted by the obstacle.