Active night vision system for vehicles employing short-pulse laser illumination and a gated camera for image capture

• US 6,730,913 B2
• Filed: 02/21/2002
• Issued: 05/04/2004
• Est. Priority Date: 02/21/2002
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Weber, Willes H., Remillard, Jeffrey Thomas
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US09/683,838
• Publication Number:
  US 20030155513A1
• Time in Patent Office: 803 Days
• Field of Search: 250/330, 250/332, 250/341.8, 250/333
• US Class Current: 250/341.8
• CPC Class Codes: G01J 1/08 Arrangements of light sources specially adapted for photometry standard sources, also using luminescent or radioactive material
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/489 Gain of receiver varied automatically during pulse-recurrence period
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification
• CPC Class Codes: H04N 23/75 by influencing optical camera components
• CPC Class Codes: H04N 25/71 Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A method of detecting objects with a night vision system is provided. The night vision system includes a light source and a camera. The method includes activating the light source as a sequence of light pulses wherein each light pulse is increasing in intensity for a predetermined number of pulses to form a pulse train. The camera is activated as a corresponding sequence of detection windows wherein each of the windows corresponds to one of the light pulses for receiving reflected light resulting from the corresponding light pulse. The light pulses and detection windows are configured such that a time delay between each corresponding light pulse and detection window is increasing throughout the pulse train. In another variation, the camera gain is increased throughout the pulse train. In yet another variation, the light pulses have constant amplitude, the camera gain is constant for all pulses, and the number of camera gain windows increases as the delay increases. In all cases, objects nearer the night vision system are imaged with lower intensity light, less camera gain, and/or fewer laser pulses than objects further away to provide a composite image in which the apparent brightness of near and far objects can be controlled.

Claims

1. A method of detecting objects with a night vision system having a near infrared light source and a camera, the method comprising:

activating said light source in the form of a sequence of light pulses wherein each light pulse is increasing in intensity for a predetermined number of pulses to form a pulse train; and

activating said camera in the form of a corresponding sequence of non-overlapping detection windows wherein each of said windows corresponds to one of said light pulses for receiving reflected light resulting from said corresponding light pulse and a time delay between each corresponding light pulse and detection window is increasing throughout said pulse train, said light pulse intensity and said corresponding time delay being selected to result in a substantially constant reflected image signal.

2. A method according to claim 1 further comprising summing all reflected light signals in said pulse train to form a composite image of detected objects within a field of view of said night vision system.

3. A method according to claim 1 further comprising generating a video image from said reflected light signals in a plurality of pulse trains and displaying said video image on an operator display.

4. A method according to claim 1 wherein each light pulse and each detection window has a constant duration.

5. A method according to claim 4 wherein the duration of each detection window is approximately twice as long as the duration of each light pulse.

6. A method according to claim 1 wherein the time delay between each subsequent corresponding light pulse and detection window increases by approximately 50 ns.

7. A method according to claim 6 wherein said pulse train is approximately 40 corresponding light pulses and detection windows.

8. A method according to claim 1 wherein a gain of each detection window is increasing throughout said pulse train.

9. A method according to claim 1 wherein said light source is a NIR diode laser and said camera is a high speed NIR-sensitive camera.

10. A method of detecting objects with a night vision system having a near infrared light source and a camera, the method comprising:

activating said light source in the form of a sequence of constant intensity light pulses to form a pulse train; and

activating said camera in the form of a corresponding sequence of non-overlapping detection windows wherein each of said windows corresponds to one of said light pulses for receiving reflected light resulting from said corresponding light pulse and wherein each detection window has an increasing gain throughout said pulse train and a time delay between each corresponding light pulse and detection window is increasing throughout said pulse train, said detection window gain and said corresponding time delay being selected to result in a substantially constant reflected image signal.

11. A method according to claim 10 further comprising summing all reflected light signals in said pulse train to form a composite image of detected objects within said night vision system field of view.

12. A method according to claim 10 further comprising generating a video image from said reflected light signals in a plurality of pulse trains and displaying said video image on an operator display.

13. A method according to claim 10 wherein each light pulse and each detection window has a constant duration.

14. A method according to claim 13 wherein the duration of each detection window is approximately twice as long as the duration of each light pulse.

15. A method according to claim 10 wherein the time delay between each subsequent corresponding light pulse and detection window increases by approximately 50 ns.

16. A method according to claim 10 wherein said light source is a NIR diode laser and said camera is a high-speed NIR-sensitive camera.

17. A method of detecting objects with a night vision system having a near infrared light source and a camera, the method comprising:

activating said light source in the form of a plurality of constant intensity light pulses to form a pulse train; and

activating said camera in the form of a plurality of non-overlapping detection windows throughout said pulse train for receiving reflected light resulting from said corresponding light pulses and wherein a time delay between each subsequent detection window and a window length is increasing throughout said pulse train, said light pulses and detection windows being configured such that objects nearer the night vision system are imaged by fewer light pulses than objects further away from said night vision system.

18. A method according to claim 17 wherein a duration of each detection window is longer than a duration of each light pulse.

19. A method according to claim 17 further comprising summing all reflected light signals in said pulse train to form a composite image of detected objects within said night vision system field of view.