Machine vision glossary
Short, plain definitions of the terms that come up when choosing an industrial camera or a vision system. Each entry links to the product page it belongs to.
- Line scan camera
- A camera with a single row of pixels that records one line of the surface at a time; the two-dimensional image is built from thousands of stacked lines and its length is not limited by the sensor. See the products
- Area scan camera
- A camera with a pixel grid that captures a complete frame in one exposure; for objects that fit inside the field of view. See the products
- Line rate
- The number of lines a line scan camera records each second, in lines per second. It must match the speed of the object, otherwise the image is stretched or squeezed. See the products
- Encoder
- A device that turns mechanical motion into pulses. When its pulses drive the camera trigger input, every line is taken a fixed distance after the one before, so a change in line speed does not distort the image. See the products
- Trigger
- The signal that tells the camera to capture now. It can come from an encoder, from a part-present sensor or from software.
- Global shutter
- An exposure method in which every pixel of the frame is exposed at the same instant, so a moving object is recorded without skew or distortion. See the products
- Rolling shutter
- An exposure method that reads the sensor rows one after another. It is cheaper and often more sensitive, but it shows a fast object skewed. See the products
- Field of view
- The part of the scene that appears in the image. On a line scan camera it is the width covered by a single line.
- Pixel size on the object
- Field-of-view width divided by pixel count. It tells you the smallest feature you can see; as a rule a feature should cover at least two or three pixels.
- Depth of field
- The range of distance over which the image stays sharp enough. Closing the aperture increases it but lets less light reach the sensor.
- TDI
- A line scan technique in which several sensor rows see the same point of the object in turn and their signals are summed, giving a brighter image in low light or at high speed.
- Frame grabber
- A card that receives the camera data and passes it to the computer. Our USB cameras do not need one.
- Emissivity
- A number between zero and one that says how much thermal radiation a surface emits compared with a perfect black body. Without setting it correctly, a thermal camera reads the wrong temperature. See the products
- Thermal camera
- A camera that converts the heat radiated by a surface into temperature and produces an image in which each pixel carries a temperature value, without touching the object. See the products
- Photo finish
- A system that records the instant of crossing the finish line and gives each competitor a time to a thousandth of a second; its image has time as the horizontal axis. See the products
- Seam tracking
- Automatic continuous correction of the welding head position onto the centre of the seam, by measuring the seam deviation and driving the actuator. See the products
- Flying saw cutting
- Cutting the product while it moves, by matching the saw carriage speed to the line so that the line does not have to stop. See the products