Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1998-06-24
2000-06-13
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
340556, G01D 2104
Patent
active
060752386
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an optical monitoring means.
For monitoring danger areas around machines, security areas, elevator doors or the safety monitoring of apartments photoelectric detectors and beam arrays using same have so far been employed. Such beam arrays suffer from the disadvantage that a plurality of active elements, i. e. light sources and sensors, must be arranged on either side of the monitored area, something which increases the costs of such a beam array. Furthermore all active elements must be connected together by wiring in order to permit synchronization and signal processing. The electronic circuitry necessary for this is also a substantial cost factor.
The German patent publication 38 42 142 C1 discloses a method for the optical recognition of objects, the means comprising a sensor means, on which an objective projects the image of a pattern field, and a signal processing means in order to ascertain whether the image received by the sensor means possesses the same optical characteristics as the pattern field. At one end of the monitored area there is therefore a passive element, namely the pattern field, whereas the sensor means together with the associated objective is placed at the other end of the monitored area so that no power supply and control lines must be laid from the one end of the monitored area to the other end. Furthermore the number of active elements is reduced.
SUMMARY OF THE INVENTION
In contradistinction to this the invention has the aim of creating a monitoring means, which may be implemented at a moderate price, the number of active elements being reduced with the possibility of ensuring a compact structure.
In order to attain this object the optical monitoring means of the invention is characterized by a plurality of pattern fields, which are respectively arranged at one end of the area to be monitored, objectives at the other end of the area to be monitored and which are respectively associated with the pattern fields, reflectors, which deflect the image rays from the objectives onto a image projection surface, a sensor means, onto which the objectives throw an image of the pattern field, and which scans the image and feeds corresponding signals to a signal processing means, which ascertains whether the image received by the sensor means possesses the same optical characteristics as the pattern fields.
The monitoring means is made up of detectors of the above mention type and comprises a plurality of superposed detectors. Owing to this arrangement a monitoring means is created, whose function is comparable with that of a beam array, several optical detectors being utilized in order to form the array of the monitoring means. Nevertheless a single sensor means suffices, which is best a CCD camera, in order to respond to the image on the image projection surface and to supply corresponding signals to the signal processing means.
Moreover the invention relates to a monitoring means comprising optical detectors of the type initially mentioned, which is characterized in that a series of pattern fields is arranged at opposite sides of an area to be monitored, that two units, which respectively comprise an objective and a reflector, are arranged at diagonally opposite corners of the area to be monitored, that the units are so rotatably arranged that one objective in each case scans the pattern field arranged opposite to it, and that opposite each reflector a sensor means is placed, onto which the objectives throw the image of the pattern field, and which scans the image and feeds corresponding signals to a signal processing means, which ascertains whether the image received by the sensor means possesses the same optical characteristics as the pattern fields. In this respect, although two sensor means are required, a whole series of optical components is rendered unnecessary.
According to an advantageous development of the invention the sensor means is a CCD camera as is presently commercially available at a moderate price. Such a camera ca
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patent: 4339660 (1982-07-01), Buchholz et al.
patent: 4546246 (1985-10-01), Bechtel
patent: 5004908 (1991-04-01), Nakamura
patent: 5008530 (1991-04-01), Ball
patent: 5180910 (1993-01-01), Sprattle et al.
Allen Stephone B.
Ines-Elektronik-Systementwicklungs-Produktions GmbH
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