Abstract: An optical monitoring means comprises a plurality of pattern fields, which are 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.