Access protection system for monitoring the access of objects (14, 16) to a monitored area (20, 25), - having at least one first optoelectronic sensor which is set up to detect an intrusion of an object into the monitored area (20, 25), - having at least one second optoelectronic sensor (28; 40) which is set up for the spatially resolved monitoring of a prefield located upstream of the monitored area (20, 25), - and having an evaluation unit which is in signal communication with the first and the second sensor (22, 28, 40), the evaluation unit being set up to trigger a safety function when an object (14, 16) penetrates the monitored area (20, 25), and being set up to suppress the safety function when the penetrating object (14, 16) is classified as an approved object (14, 16), characterized - in that the prefield comprises a plurality of adjacent contour detection fields (36-1, 36-2, 36-3) of the second sensor, - in that the evaluation unit is set up to detect, on the basis of signals which have been received from the second sensor, a contour of an object penetrating into the prefield, in each case within a contour detection field (36-1 or 36-2 or 36-3), and to compare the detected contour with a predetermined reference contour, and to compare the detected position of the detected contour with a reference position of the reference contour in the respective contour detection field (36-1 or 36-2 or 36-3), wherein the reference contour consists of the fact that the contour detection field (36-1 or 36-2 or 36-3) is interrupted on its full width at the reference position, - and the evaluation unit is further arranged to classify the penetrating object (14, 16) as an approved object (14, 16) only if the detected contour corresponds to the reference contour at the reference position. - having at least one first optoelectronic sensor which is set up to detect an intrusion of an object into the monitored area (20, 25), - having at least one second optoelectronic sensor (28; 40) which is set up for the spatially resolved monitoring of a prefield located upstream of the monitored area (20, 25), - and having an evaluation unit which is in signal communication with the first and the second sensor (22, 28, 40), the evaluation unit being set up to trigger a safety function when an object (14, 16) penetrates the monitored area (20, 25), and being set up to suppress the safety function when the penetrating object (14, 16) is classified as an approved object (14, 16), - in that the prefield comprises a plurality of adjacent contour detection fields (36-1, 36-2, 36-3) of the second sensor, - in that the evaluation unit is set up to detect, on the basis of signals which have been received from the second sensor, a contour of an object penetrating into the prefield, in each case within a contour detection field (36-1 or 36-2 or 36-3), and to compare the detected contour with a predetermined reference contour, and to compare the detected position of the detected contour with a reference position of the reference contour in the respective contour detection field (36-1 or 36-2 or 36-3), wherein the reference contour consists of the fact that the contour detection field (36-1 or 36-2 or 36-3) is interrupted on its full width at the reference position, - and the evaluation unit is further arranged to classify the penetrating object (14, 16) as an approved object (14, 16) only if the detected contour corresponds to the reference contour at the reference position.