Area or Full–Field Scanners

An area, or "full–field", scanner operates by taking a digital photograph of an object to be measured, and calculating the range from the scanner to each pixel of the image. From this, it can output the x, y and z coordinates of each pixel.

Figure 1 An engine component, along with a full–field scan of surface shape. This is shown as seen by the scanner's camera. Range (z) is represented as pseudo-colour, while x runs left-right, and y is up–down. This component is leaning forward, giving the range map shown.

The pixels are laid out in a rectangular grid with a regular pitch, corresponding to the pixels on the digital camera sensor In other words, the full–field scanners take measurements on a regular grid – which might place a measurement every X microns (or millimetres) across a surface. The z–dimensions typically have resolution an order of magnitude better than the x–y resolution.

Typically a 3D area scanner (such as the Quartz white light scanner) will take millions of measurements in a few seconds. This mass of measurement data is presented as a "point cloud" – which, when visualised, looks remarkably like the object being inspected. With the Quartz scanners, each measurement can have colour – so the point cloud gives a 3D model of near–photo quality.

This is in marked contrast to a CMM that typically gathers only a small numbers of (x,y,z) coordinates – the data is difficult to interpret, but where x, y and z components all have similar resolution.