Patent ID: 8810652

Claim:
A device for monitoring a monitored area with at least one camera comprising: a contrast strip in the monitored area which has at least one bright partial strip and/or a control unit configured to detect an obscuration of a minimum area of the bright partial strip and/or the dark partial strip caused by entry of an object into the monitored area, the control unit further being configured to: learn and file in memory during a teaching phase a signature for the contrast strip, the signature comprising a bright beginning, a bright end, and the number of bright pixels between the bright beginning and the bright end of the bright partial strip, and a dark beginning, and a dark end and the number of dark pixels between the dark beginning and the dark end of the dark partial strip for each column arranged in a transverse direction to the contrast strip, recognize the obscuration of each column as a violation of the signature of the contrast strip by detecting in each column a first minimum number of bright pixels between a bright beginning and a bright end of the bright partial strip and/or a second minimum number of dark pixels between a dark beginning and a dark end of the dark partial strip in the respective columns, and, compare said first minimum number of bright pixels and/or second minimum number of dark pixels with the signature of the contrast strip, wherein an obscuration of the minimum area is recognized when a predetermined number of columns that lie side by side are obscured, and wherein the control unit is further configured to determine, in the teaching phase, the signature of the contrast strip as follows: for each column, count how often there exists a signature having the bright beginning, the bright end, the dark beginning and the dark end, to thereby determine a signature count for each column, identify a portion of area of the contrast strip which has the most side-by-side columns with a signature count of exactly one, and select an extended portion of the area of the contrast strip, the extended portion including the portion with the most side-by-side columns with a signature count of exactly one and further including all adjacent columns with a signature count of one or more, wherein the extended portion terminates at two ends of the extended portion, each end being defined by either an edge of the contrast strip or by a column with a signature count of zero.