Anti-intrusion security device for surfaces, e.g. shop windows - has multiple reflective surfaces with light emitter and receiver to form optical protective curtain

摘要

The surface to be protected e.g. shop window (1), has a reflective border situated at the upper and lower part of the internal frame (2,3), and in the upper corner of the frame, a light source (4) is fixed, and in the opposite upper corner, a receiver (5). The light source (4) can be a Galluim-arsenide diode or similar, and the light emitted by it reaches the receiver (5) after being reflected a number of times back and forth by the reflective borders (2,3). This forms a light curtain which changes in intensity at the receiver (5) if an object or person enters the field of coverage. The mirror-like reflective borders (2,3) are made up of a number of parallel running 'V'-shaped channels, each one forming a 90 degree angle mirror, made of plastic, and numbering about twenty to thirty channels per border. This enables a cheaply produced security device for windows to be manufactured by the injection moulding process.