Optical highway line detector

• US 6,498,570 B2
• Filed: 05/24/2001
• Issued: 12/24/2002
• Est. Priority Date: 05/24/2001
• Status: Expired due to Term

• Current Assignee: Aurora Operations Incorporated (Aurora Innovation, Inc.)
• Original Assignee: Philip N. Ross
• Inventors: Ross, Phillip N.
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US09/865,070
• Publication Number:
  US 20020175813A1
• Time in Patent Office: 579 Days
• Field of Search: 340/901, 340/904, 340/905, 340/933, 340/942, 340/438, 340/439, 250/239, 250/397, 180/167, 180/169
• US Class Current: 340/901
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 3/781 Details
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A highway lane position detector including a photodetector for determining the existence of highway lines, wherein the detection circuitry maintains its detection ability over a wide range of ambient light conditions from bright sunlight to dim artificial light in ambient darkness, by providing a dynamic resistance element in series with the photodetector wherein the dynamic resistance element compensates for changes in the photodetector due to changes in ambient light conditions to maintain the photodetector in a detection condition (avoiding saturation) regardless of the ambient light condition. In the preferred embodiment of the detector, the dynamic resistance element is at least one reversed biased zener diode. In currently preferred circuitry of the invention, the detector detects the presence of intermittent lane dividing lines and provides an alarm when such lines are no longer detected.

Claims

1. A detector for detecting light reflected from a light area on a surface, comprising:

a photodetector positioned to receive light from a portion of the surface; and

a dynamic impedance element connected electrically in series with the photodetector to maintain the photodetector in condition to detect light reflected from a light area on the surface regardless of the ambient illumination of the surface.

2. A detector for detecting light reflected from a light area on a surf ace according to claim 1, wherein the dynamic impedance element is at least one reversed biased zener diode.

3. A detector for detecting light reflected from a light area on a surface according to claim 2, wherein the at least one zener diode has a breakdown zener voltage, and the maximum expected voltage produced across the photodetector as connected with the zener diode in detecting ambient light reflected from the surface is less than the zener breakdown voltage.

4. A detector for detecting light reflected from a light area on a surface according to claim 3, wherein the photodetector is a phototransistor.

5. A detector for detecting light reflected from a light area on a surface according to claim 2, wherein the at least one zener diode is a series connection of two zener diodes.

6. A detector for detecting light reflected from a light area on a surface according to claim 5, wherein the detector additionally includes a plurality of photodetectors and associated series zener diodes.

7. A detector for detecting light reflected from a light area on a surface according to claim 6, wherein differences in light detected by different photodetectors indicate detection of the light area and position of the light area relative to the detector.

8. A detector for detecting light reflected from a light area on a surface according to claim 1, wherein the detector additionally includes a plurality of photodetectors and associated series dynamic impedance elements.

9. A detector for detecting light reflected from a light area on a surface according to claim 8, wherein differences in light detected by different photodetectors indicate detection of the light area and position of the light area relative to the detector.

10. A detector for detecting light reflected from lines on a highway surface from a moving motor vehicle, comprising:

a photodetector mounted to receive light reflected from the lines in a predetermined manner when the vehicle is properly within a lane but not otherwise;

an alarm to, once enabled, provide an indication when light is received by the photodetector in other than the predetermined manner; and

a dynamic impedance element electrically connected in series with the photodetector to maintain the photodetector in condition to detect light reflected from a line regardless of ambient illumination of the highway and line.

11. A detector according to claim 10, wherein said dynamic impedance element includes a reverse biased zener diode.

12. A detector for detecting light reflected from lines on a highway surface according to claim 10, further comprising:

an optical system for directionally focusing reflected light onto the photodetector;

an amplifier electrically connected at the junction of the photodetector and dynamic impedance element for amplifying changes in the output signal from the photodetector with respect to the dynamic impedance element; and

circuitry for producing an output in response to the output of the amplifier for each line detected.

13. A detector for detecting light reflected from lines on a highway surface according to claim 12, wherein the circuitry for producing an output produces a pulse , and such circuitry is circuitry for detecting peaks in the output of the amplifier and producing a pulse for detected peaks.

14. A detector for detecting light reflected from lines on a highway surface according to claim 12, wherein the circuitry for producing an output produces a pulse, and such circuitry is voltage reference and detector circuitry for producing a pulse for detected lines.

15. A detector for detecting light reflected from lines on a highway surface according to claim 12, wherein the output produced for each line detected 15 sent to logic circuitry which determines if the light is received in the predetermined manner, and if not, activates the alarm.

16. A detector for detecting light reflected from lines on a highway surface according to claim 15, wherein the lines detected are discontinuous lane dividing lines and the predetermined manner for receiving the reflected light is to receive light indicating a line within each of successive fixed time periods.

17. A detector for detecting light reflected from lines on a highway surface according to claim 16, wherein the logic circuitry is a programmed computer.

18. A detector for detecting light reflected from lines on a highway surface according to claim 10, further including logic circuitry to determine if the light has been received by the photodetector in other than the predetermined manner and to activate the alarm if the light has been received in other than the predetermined manner.

19. A detector for detecting light reflected from lines on a highway surface according to claim 18, wherein the logic circuitry is a programmed computer.

20. A detector for detecting light reflected from lines on a highway surface according to claim 10, additionally including a light source directed to illuminate the highway surface being sensed when ambient light is not sufficient to illuminate the lines for detection.

21. A detector for detecting light reflected from highway lines on a highway surface according to claim 10, wherein the detector additionally includes a plurality of photodetectors and associated series dynamic impedance elements.

22. A detector for detecting light reflected from a light area on a surface according to claim 20, wherein differences in light detected by different photodetectors indicate detection of the light area and position of the light area relative to the detector.

27. A detector according to claim 20, wherein the logic circuitry is a programmed computer.

23. A detector for detecting light reflected from discontinuous lane dividing lines on a highway surface from a moving motor vehicle, comprising:

a photodetector mounted to receive light reflected from the discontinuous lane dividing lines when the vehicle is properly within a lane but not otherwise;

circuitry to produce a pulse for each lane dividing line sensed;

logic circuitry to determine if a pulse is produced, indicating a line sensed within successive fixed periods of time in which it is expected that a line should be sensed; and

an alarm to, once enabled, provide an alarm indication if the logic circuitry determines an alarm condition exists.

24. A detector according to claim 23, additionally including a light source directed to illuminate the highway surface being sensed when ambient light is not sufficient to illuminate the lines for detection.

25. A detector for detecting light reflected from a light area on a surface according to claim 23, wherein the detector additionally includes a plurality of photodetectors and associated series dynamic impedance elements.

26. A detector for detecting light reflected from a light area on a surface according to claim 23, wherein differences in light detected by different photodetectors indicate detection of the light area and position of the light area relative to the detector.

28. A method for detecting whether a vehicle is maintaining position in a highway lane marked by at least one set of discontinuous lane dividing lines on the highway surface, comprising the steps of:

detecting, using a photodetector, discontinuous lane dividing lines marking the lane in which the vehicle is traveling;

determining through logic circuitry if a line is detected in each of a succession of time periods in which it would be expected lines would be detected if the vehicle stayed in the lane and detected such lines; and

giving an alarm if such lines are not detected in each of the expected successive time periods, such lines not being detected indicating the lines are not being sensed and possible drift of the vehicle out of the lane.