Here I’ll cover how sensors can collect readings from an environment and represent those readings in a practical way. The most common field scanning devices are flat bed scanners and cameras. These devices either have a line of sensors or an array of them to take readings quickly. Flat bed scanners typically have a line of sensors that detect light and color. As the sensors move along the surface of an object, typically paper, they buffer the readings into memory. The memory is then read and the values are depicted as an image. Cameras work the same way, instead the sensors are in an array along a horizontal and vertical plane. There are millions of sensors in a common digital camera. When a picture is taken, each sensor are read very quickly and the values are placed in memory. The camera sensor is read side to side and top to bottom until all the senors have their readings in memory. These are examples of field scanning.
There is a limit on all of these sensors. If you take away the line of sensors or the sensor array, the individual sensor can only take a reading of a single fixed point. In order to recreate a horizontal and vertical representation of an object, the sensor has to move its focus horizontally and vertically. This is field scanning and it is how SONAR, RADAR, radio astronomy, and LIDAR work.
Having an array of sensors sometimes is not cost effective. Forward looking infra red sensors are built into sensor arrays, however they cost 10 to 100 times more than visual sensor arrays. Using field scanning at the mechanical level, this cost can be offset. Mechanical field scanning has a much slower response time than electronic. Depending on the objected being observed, this limitation can be ignored.
Above is a false color map of a field scan made with an induction sensor, commonly known as a metal detector. Creating a line of sensors or an array would be impractical. Using a single point sensor that moves through the field is more cost effective and versatile.
This isn’t a long read, I just wanted to cover the topic. I’ll be using this technique in future posts and wanted to establish some background on the subject first.