Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2002-08-15
2004-11-09
Porta, David (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C340S556000
Reexamination Certificate
active
06815660
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an optoelectronic monitoring device comprising at least one transmitter arranged at an end of a monitored zone, at least one reflector arranged at an end of the monitored zone opposite the transmitter for electromagnetic radiation transmitted by the transmitter and at least one receiver for radiation reflected by the reflector. The invention further relates to a method of detecting objects intruding into a monitored zone.
Such monitoring devices and detection methods are generally known and serve to detect objects intruding into the monitored zone. The use of such monitoring devices takes place, for example, at hazardous machinery or at devices relevant to safety at which the intrusion of objects or persons, or individual body parts, into the monitored zone, also known as the protected zone, should be prevented. The monitoring device in this manner provides for the safety of the persons working on the machine or for the security of the monitored or protected zone.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an optoelectronic monitoring device of the kind first named which, while functioning reliably, is as secure as possible against manipulation and is as insensitive as possible with respect to external interference radiation and which should in particular have a favorable cost and allow the detection of objects in the monitored zone with high resolution. Furthermore, an improved detection method should be provided.
This object is satisfied, on the one hand, in that the transmitter has a group of transmission elements which are spaced apart from one another and which each transmit electromagnetic radiation into the monitored zone. A receiver has at least one spatially resolving reception element for radiation reflected by the radiator and an evaluation device is provided which is coupled to the reception element. The transmitter, the reflector and the receiver are made and arranged such that, during the monitoring operation, at least one part of the group of transmission elements including a plurality of transmission elements is imaged on the reception element by means of the reflector so that a check can be made by means of the evaluation device as to whether a pattern on the reception element formed by the imaged transmission elements deviates from an expected image of the transmission elements.
In accordance with the invention, the transmission elements of the transmitter and the reception element of the receiver form an active side and the reflector at the end of the monitored zone opposite the transmission elements forms a passive side of the monitoring device. If the radiation transmitted by at least one transmission element is interrupted, e.g. by an object intruding into the monitored zone, then this infringement of the monitored zone, or protected zone, is recognized in that a deviation of the pattern detected on the reception element from the expected image of the transmission elements occurs by means of the evaluation device. In this connection, the resolution of the monitoring device, i.e. the detection limit, is defined by the distance of the transmission elements from one another. The resolution of the device can generally be increased as desired by the selection of a correspondingly low spacing between the transmission elements, which preferably lie in one plane and form radiation sources.
In accordance with the invention, only a single reception element is required for the group of transmission elements, i.e. it is not necessary to associate a receiver with every transmission element. A particularly cost favorable active/passive construction is thereby realized. Alternatively, in accordance with the invention, a plurality of reception elements can also be provided.
A further advantage of the monitoring device of the present invention consists of the fact that any displacement of the passive part, i.e. of the reflector, relative to the active part is recognized, since the pattern of the group of transmission elements detected on the reception element deviates from the expected image of the group of transmission elements with a relative arrangement between the transmitter, the reflector and the receiver not in accordance with their purpose. As a result, the monitoring device of the invention is highly secure against manipulation. A deflected reflection of the radiation transmitted by the transmission elements, e.g. by introducing additional beam deflection means into the beam path, carried out for purposes of manipulation, results in a spatial displacement of the imaged transmission elements on the reception element, which is recognized by comparing the actually detected pattern of the transmission elements with the expected pattern.
Further, the imaging of the transmission elements advantageously takes place in accordance with the invention such that interference radiation not originating from the transmission elements cannot impact in the regions of the reception elements in which the radiation transmitted by the transmission elements and reflected by the reflector is detected. As a result, the monitoring device of the invention is highly secure against interference radiation.
Respectively separate units are not necessarily to be understood as the transmission elements in the sense of the invention; the transmission elements can rather be radiation sources generally realized in any manner. The wavelength of the radiation used can generally be any wavelength in accordance with the invention and can lie both in the range visible to the human eye and in the range invisible to the human eye.
The radiation sensitive area of the reception element is preferably smaller, and in particular substantially smaller, than the area over which the transmission elements are distributed. The imaging of at least some of the transmission elements is preferably achieved by an optical imaging system of the receiver which is matched to the respective circumstances and which is interposed in front of the reception element, with the optical imaging system or the optical receiving system preferably having a multi-lens system.
In a preferred practical embodiment of the invention, provision is made that the receiver is arranged in the region of the transmitter and preferably in direct proximity to the transmitter. It is particularly preferred for the receiver and the transmitter to be combined to form one module. An advantageous modular construction is thereby made possible in which a plurality of modules including at least one respective transmitter and at least one receiver can be combined together to form a transmission/reception system. With such a modular system, low demands result in an advantageous manner on the number of transmission elements per module, which is required for monitoring security which is sufficient in accordance with the respective application, and on the opening angle of the modules.
In accordance with a further preferred embodiment of the invention, a single row arrangement of transmission elements is provided. A narrow construction of the active side of the monitoring device, which is advantageous for certain applications, can be achieved by this one-dimensional arrangement of the group of transmission elements. The receiver, or its reception element, is preferably arranged on a line with the row of transmission elements, but can also be positioned to the side of the transmission elements.
A two-dimensional arrangement of the transmission elements, and thus a three-dimensional monitored zone, is achieved in accordance with a further preferred embodiment in that a multi-row arrangement of the transmission elements is provided. In this connection, these elements preferably form lines and gaps extending perpendicular to one another. The transmission elements can also be arranged asymmetrically.
A further embodiment of the invention provides for at least one reception element to be provided on which the group of transmission elements is completely imaged. Precisely one such reception ele
Henkel Olaf
Wuestefeld Martin
Porta David
Sick AG
Sohn Seung C.
Townsend and Townsend / and Crew LLP
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