Step into any supermarket, hospital, or airport and you will notice something most people overlook a door slides open as if it anticipated their arrival. No touch required, just a quiet swoosh and passage is granted. It seems routine ms80 linear motor automatic sliding door operator until you question how it senses you. The response is a rather stratified pile of engineering, and decades long. ADS have become more of a necessity than scenery, and thus embedded in everyday life to the extent that without them, not being able to use them would be truly disorienting. 
At the core, everything relies on sensors, though that word carries more complexity than it suggests. Most sliding automatic doors use microwave or infrared motion detectors mounted above the doorway. These sensors create a detection field, like an invisible cone extending onto the floor. When that field is interrupted or reflected, a signal triggers the motor and the door slides open. Simple in theory. However the engineering becomes tricky soon. It needs to differentiate between human movement and something like a flying bird. It must be able to cope with a crowd of ten individuals who walk in a cluster and not get confused and swing the door back and forth. High-end versions utilize 3D time-of-flight sensors to map depth, effectively generating a live topographical view of the doorway. No, it is not a doorbell camera, it is more like what self-driving cars have to see the road. Swing doors, folding doors, revolving doors - everything has a solution to a different problem. An example is the revolving doors which are brilliant thermally. They function as an airlock, reducing the loss of heated or cooled air when people enter. This is crucial in environments like hospitals or data centers. For busy environments and large loads such as carts, wheelchairs, and stretchers, sliding doors are ideal. The type of door used does not depend on the doors to make. It adheres to building codes, occupancy loads, fire egress laws and even intense disagreements between architects and facilities managers whose priorities differ radically. One prioritizes design appeal, the other simply wants a system that will not fail at 2 AM.
At the core, everything relies on sensors, though that word carries more complexity than it suggests. Most sliding automatic doors use microwave or infrared motion detectors mounted above the doorway. These sensors create a detection field, like an invisible cone extending onto the floor. When that field is interrupted or reflected, a signal triggers the motor and the door slides open. Simple in theory. However the engineering becomes tricky soon. It needs to differentiate between human movement and something like a flying bird. It must be able to cope with a crowd of ten individuals who walk in a cluster and not get confused and swing the door back and forth. High-end versions utilize 3D time-of-flight sensors to map depth, effectively generating a live topographical view of the doorway. No, it is not a doorbell camera, it is more like what self-driving cars have to see the road. Swing doors, folding doors, revolving doors - everything has a solution to a different problem. An example is the revolving doors which are brilliant thermally. They function as an airlock, reducing the loss of heated or cooled air when people enter. This is crucial in environments like hospitals or data centers. For busy environments and large loads such as carts, wheelchairs, and stretchers, sliding doors are ideal. The type of door used does not depend on the doors to make. It adheres to building codes, occupancy loads, fire egress laws and even intense disagreements between architects and facilities managers whose priorities differ radically. One prioritizes design appeal, the other simply wants a system that will not fail at 2 AM.