Optical metrology is the principle behind optical measurement devices, such as the GapGun that can determine the dimensional profile of a part, by taking a series of pictures of its surface.
How the GapGun takes optical measurements
The GapGun is an optical measurement system that uses laser triangulation technology to collect its measurements. GapGun does this by projecting a laser stripe across the surface of a part to determine the measureable feature. Simultaneously, the integrated camera system takes images of this static laser stripe. As the angle is known between the camera and the laser projection, then an algorithm (mathematical rule) can be written to calculate the dimensions of the surface over which the laser falls and the camera sees. This measured data is then output to point cloud format to generate a digital copy of the surface.
A point cloud is produced by software that uses image processing to convert the images of the profile into a series of points which can be used to extrapolate the shape of the feature. These points allow the system to analyse the measured surface. Because a laser is a clean form of structured light, measured data is highly reliable and can be used as a stable light source for data analysis.