Dimensional and Profile Scanners

Dimensional and profile scanners gather two-dimensional (2D) or three-dimensional (3D) information about an object. They use several different configurations and technologies. Coordinate measuring machines (CMM) are dimensional and profile scanners that move a measuring probe to determine coordinates of points on a workpiece surface. CMMs consist of four main components: the machine itself, the measuring probe, the control or computing system, and the measuring software.  Photogrammetry is a dimensional measurement method that uses geometry, mathematics, and physics to create 3D coordinates from 2D still-pictures. Videogrammetry is a noncontact measurement technique which applies geometry and mathematics to images from video cameras in order to determine the 3D coordinates of objects. Both 2D scanners and 3D scanners can use optical or laser-based methods to capture information about an object; however, 2D dimensional and profile scanners cannot account for object’s depth.

Dimensional and profile scanners differ in terms of machine positioning, mounting style, and probe type. Machine positioning can be controlled by an operator, a personal computer (PC), or a computer numerical control (CNC) interface. Suppliers describe mounting styles as bench top, free standing, handheld, or portable. There are four basic types of probes or sensors for dimensional and profile scanners: touch probes, laser triangulation probes, still-camera probes, and video camera probes. Touch probes or discrete-point probes make physical contact with the surface of the workpiece. They use kinematic (switching), strain-sensing, or piezoelectric technologies. Upon contact, the touch probe transmits a signal that contains the point’s coordinates to a coordinate measuring machine (CMM). The touch probe is then moved to the next location and the process is repeated. Laser triangulation probes or scanning probes use a different sensing method. As they pass over the workpiece surface, a continuous flow of data is transmitted to the measurement system. 

There are many applications for dimensional and profile scanners. Some devices are used for dimensional measurement or inspection. Others are used to capture information about the profile, form, angularity, or orientation of an object. Specialized shaft measurement products are also available. Dimensional and profile scanners that perform depth mapping measure the difference between two stereo images, successive images of the same scene taken a slightly different angles. Objects that are further away move relatively little from one image to the next. Objects that are closer to the viewer move by a greater degree. The resulting depth map consists of a single image with different intensities to represent the different depths. Dimensional and profile scanners that use three-dimensional scanning or digitizing capture the geometry of existing physical objects for conversion into a digital format or image.

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