System for detecting the presence of a possibly moving object

• US 4,026,654 A
• Filed: 09/24/1975
• Issued: 05/31/1977
• Est. Priority Date: 10/09/1972
• Status: Expired due to Term

• Current Assignee: Engins Matra
• Original Assignee: Engins Matra
• Inventors: Beaurain, Pierre
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/616,403
• Time in Patent Office: 615 Days
• Field of Search: 356/4, 356/5, 356/28, 343/5 PD, 343/6 ND, 343/112 CA, 340/1 T, 340/33, 340/38 P, 340/38 S, 180/98
• US Class Current: 356/5.07
• CPC Class Codes: G01S 17/50 Systems of measurement based on relative movement of target
• CPC Class Codes: Y10S 367/902 Speed of sound compensation
• CPC Class Codes: Y10S 367/909 Collision avoidance

Abstract

A system for detecting the distance L between two objects A and B, either or both of which may be in motion, comprising approach detector means and proximity detector means operational within overlapping distance ranges; each detector means includes an emitter mounted on a first one of the objects, which radiates a primary signal toward the second object, a responder on the second object, which radiates a similar secondary signal back toward the first object, and a signal comparator for measuring the time differential between the primary and secondary signals to determine the distance L between the objects. A range switch coupled to both comparators develops an output indicative of the distance L within a comprehensive distance range encompassing both the approach range and the proximity range and extending down to zero distance.

Claims

1. A high-resolution system for detecting the distance L separating two objects A and B, either or both of which may be in motion, comprising:

approach detector means including approach emitter on object B for radiating toward object A a primary approach signal of a first kind, approach responder means on object A for receiving the primary approach signal and radiating toward object B a secondary approach signal of said first kind, an approach receiver on object B, for receiving the secondary approach signal, and approach comparator means, coupled to the approach emitter and to the approach receiver, for comparing the times of emission of the primary approach signal and reception of the secondary approach signal to determine the distance L within an approach distance range;

proximity detector means including a proximity emitter on object B for radiating toward object A a primary proximity signal of a second kind different from the approach signals, proximity responder means on object A for receiving the primary proximity radiation signal and radiating toward object B a secondary proximity signal of said second kind, a proximity receiver on object B for receiving the secondary proximity signal, and proximity comparator means, coupled to the proximity emitter and the proximity receiver, for comparing the times of emission of the primary proximity signal and reception of the secondary proximity signal to determine the distance L within a proximity distance range encompassing distances smaller than the approach distance range; and

range switch means, coupled to the approach comparator means and the proximity comparator means, for developing an output indicative of distance L within a comprehensive distance range encompassing both the approach range and the proximity range.

2. A high-resolution distance detection system, according to claim 1, in which the approach signals and the proximity signals constitute different forms of radiation.

3. A high-resolution distance detection system, according to claim 2, in which at least one of the responder means on object A comprises:

an intermediate receiver for receiving a primary signal from object B;

and an intermediate emitter actuated by the intermediate receiver for radiating a similar but distinguishable secondary signal back toward object B.

4. A high-resolution distance detection system, according to claim 3, in which the intermediate emitter is constructed to generate and radiate a secondary signal having a different frequency from the primary signal received by the intermediate receiver, but in the same frequency spectrum.

5. A high-resolution distance detection system, according to claim 2, in which at least one of the responder means on object A comprises a reflector for reflecting a primary signal received from object B back, as a secondary signal, toward object B.

6. A high-resolution distance detection system, according to claim 1, in which the approach signals are ultrasonic signals and the proximity signals constitute electromagnetic radiation.

7. A high-resolution distance detection system, according to claim 6, in which the primary proximity signal is a coherent light beam, in which the proximity emitter includes scanning means for deflecting that beam along a predetermined scanning path, and in which the proximity responder means includes two reflectors mounted at spaced locations on object A, relative to the scanning path, to reflect two secondary proximity signals back toward object B.

8. A high-resolution distance detection system, according to claim 7, in which the primary proximity signal is generated by an oscillator-actuated laser.

9. A high-resolution distance detection system, according to claim 8, in which the proximity receiver on object B comprises a photodiode and filter means limiting light impinging on the diode to a narrow band encompassing that emitted by the laser, and further comprising scan-limiting means including two spaced auxiliary reflectors on object B for reflecting the laser beam back toward a given point on object B, and an auxiliary receiver located at that given point on object B for receiving laser beam signals reflected from the two auxiliary reflectors, limiting the angular extent of the scanning path to the spacing between the auxiliary reflectors.

10. A high-resolution distance detection system, according to claim 9, in which the scanning means comprises a double face mirror, on object B intermediate object A and object B, and means for rotating the mirror at a predetermined speed, the laser and the proximity receiver each being mounted in alignment with one face of the mirror.

11. A high-resolution distance detection system, according to claim 10, in which the mirror comprises two groups of two intersecting reflector planes each oriented at right angles to each other and at an angle of 45°

to the axis of rotation.

12. A high-resolution distance detection system, according to claim 6, in which the approach responder on object A comprises an intermediate ultrasonic receiver responsive to a primary approach signal from object B, and an intermediate approach emitter actuated by the intermediate approach receiver for radiating an ultrasonic secondary approach signal back toward the approach receiver on object B, the secondary approach signal having a frequency substantially different from the primary approach signal, each emitter radiating short primary approach signal bursts separated by substantial quiescent intervals, the system further comprising means for actuating the primary approach emitter after a predetermined quiescent interval whenever no secondary approach signal is received at the approach receiver on object B and for actuating the primary approach emitter immediately after reception of a secondary approach signal.

13. A high-resolution distance detection system, according to claim 12, and further comprising reception window control means for deactivating the approach receiver on object B for a limited time interval immediately following each reception of a secondary approach signal, said limited time interval encompassing the period of radiation of the primary approach signal.

14. A high-resolution distance detection system, according to claim 6, and further comprising power servo control means, coupled to the approach receiver and the approach emitter, for adjusting the output amplitude of the approach emitter in response to variations in the strength of the received secondary approach signals relative to a predetermined standard and thereby compensate for variations in propagation conditions for the ultrasonic approach signals.

15. A high-resolution distance detection system, according to claim 6, in which each primary approach signal comprises a short burst of ultrasonic energy of given duration at a predetermined frequency followed by a substantially longer quiescent interval, and further comprising means for progressively decreasing the quiescent interval as the distance between the objects decreases.

16. A high-resolution distance detection system, according to claim 15, in which the approach comparator means comprises an oscillator of given frequency, a counter, and gate means for applying the output of the oscillator to the counter for a period initiated by emission of the primary approach signal and terminated by reception of the secondary approach signal, whereby the count in the counter is indicative of the distance L.

17. A high-resolution distance detection system, according to claim 16, and further comprising thermal sensor means for developing a temperature signal representative of ambient temperature, and means for applying the temperature signal to the oscillator to adjust the oscillator frequency for varying ambient temperatures.