Optical Triangulation Sensors are commonly used to provide door mounted safety detection on swinging automatic doors. These types of sensors are common in North America. When automatic swinging doors open and close, it is important that they do not come into contact with pedestrians passing through the

door A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a ''doorway'' or ''portal''. A door's essential and primary purpose is to provide security b ...

. Sensors used in the automatic door industry typically fall into four categories: #

Microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequency, frequencies between 300 MHz and 300 GHz respectively. Different sources define different fre ...

sensors used to detect motion of a person as they approach an automatic door, #Reflective

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...

sensors that are mounted on the door header and detect the presence of a person in the door path #

Camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

based sensors that are also mounted on the door header and similarly detect presence; and #

Triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle ...

sensors which are mounted on the door and move with the door to provide safety. Reflective and camera technologies do not perform well on moving swing doors, because they typically depend upon detection of changes in the background. A sensor mounted on a swing door system is constantly in motion, so the background (i.e. floor beneath the door) changes continuously. A triangulation sensor overcomes this problem.

Triangulation Sensor Functionality

In most cases, an optical triangulation sensor is mounted near the top of the swinging door frame, inside a long extruded

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It h ...

tube with an

optical window The optical window is a range of wavelengths that are not blocked by the earth's atmosphere. The window runs from around 300 nanometers (ultraviolet-B) up into the range the human eye can detect, roughly 400–700 nm and continues up to approxi ...

facing the floor. An {{nowrap, 880 nm

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...

light source emits a collimated,

near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

light beam A light beam or beam of light is a directional projection of light energy radiating from a light source. Sunlight forms a light beam (a sunbeam) when filtered through media such as clouds, foliage, or windows. To artificially produce a lig ...

. The beam bounces off the floor and is received by a photodiode positioned adjacent to the LED source. A second photodiode (or a linear array of photodiodes) is positioned farther along the length of the sensor. When the emitted beam bounces off the floor, the reflected energy is almost exclusively concentrated on the first adjacent photodiode. When a human or object moves into the

optical path Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium. The geometrical optical-path length or simply geometrical path length (GPD) is the length of a segment in a given OP, i.e., the Euclidean d ...

, the reflected beam bounces back from the object. Since the beam is no longer traveling the full optical path length to the floor, its reflected angle changes. One of the adjacent photodiodes then receives the optical energy and the sensor responds by sending a signal to the automatic door controller. At that point the door stops, slows or reverses, hence averting a collision and providing safety. Triangulation sensors are found on a number of door brands and manufactured by several sensor manufacturers. One example is the SuperScan-II from BEA. Other products from other manufacturers are also available.

Safety standards

ANSI A156.10-2005 standard for U.S. Automatic Pedestrian Doors American Association of Automatic Door Manufacturers (AAADM)

External links

SuperScan-II Installing Rollup Garage DoorsOptical Sensors With LED & Laser Triangulation
Electromechanical engineering Door automation