Claims
- 1. A method of detecting an object in a zone of detection using a plurality of pairs of three dimensional energy emitters and receivers, wherein the emitters emit energy beams in a predetermined angle at the object and the receivers sense the energy beams reflected from the object, the method comprising:sampling a reflected energy beam of an emitter receiver pair a predetermined number of times to provide a set of strength signals indicative of the strength of the reflected energy; determining a variance range for the set of strength signals; comparing the variance range for the set to a predetermined maximum variance range; and generating an object detection signal when the variance range is within the predetermined maximum variance range.
- 2. The method of claim 1 further comprising:modulating an emitted energy beam of the emitter receiver pair with a predetermined modulation code; detecting the presence of the modulation code within the sampled energy beam; and generating the object detection signal when the modulation code is detected.
- 3. A system for detecting in object in a zone of detection comprising:a plurality of pairs of three dimensional energy emitters and receivers, wherein the emitters emit energy beams in a predetermined angle at the object and the receivers sense the energy beams reflected from the object; a controller responsive to signals from the receivers, the controller having data acquisition and data processing circuitry for, sampling a reflected energy beam of an emitter receiver pair a predetermined number of times to provide a set of strength signals indicative of the strength of the reflected energy; determining a variance range for the set of strength signals; comparing the variance range for the set to a predetermined maximum variance range; and generating an object detection signal when the variance range is within the predetermined maximum variance range.
- 4. A system of claim 3, wherein the data acquisition and data processing circuitry further comprises circuitry for:modulating an emitted energy beam of the emitter receiver pair with a predetermined modulation code; detecting presence of the modulation code within the sampled energy beam; and generating the object detection signal when the modulation code is detected.
Parent Case Info
This is a division of application Ser. No. 09/410,561, filed Oct. 1, 1999 now U.S. Pat. No. 6,279,687, the contents of which is incorporated herein by reference.
US Referenced Citations (18)
Foreign Referenced Citations (4)
Number |
Date |
Country |
0 424 097 |
Apr 1991 |
EP |
0 699 619 |
Mar 1996 |
EP |
2 051 356 |
Jan 1981 |
GB |
WO 8703100 |
May 1987 |
WO |