If the sensor that is used to produce the range image is properly calibrated the pixel values can be given directly in physical units, such as meters.
In order to solve the depth measurement problem using a stereo camera system it is necessary to first find corresponding points in the different images.
For instance, it is difficult to solve the correspondence problem for image points that lie inside regions of homogeneous intensity or color.
As a consequence, range imaging based on stereo triangulation can usually produce reliable depth estimates only for a subset of all points visible in the multiple cameras.
It is also not unlike a LIDAR, except that ToF is scannerless, i.e., the entire scene is captured with a single light pulse, as opposed to point-by-point with a rotating laser beam.
Time-of-flight cameras are relatively new devices that capture a whole scene in three dimensions with a dedicated image sensor, and therefore have no need for moving parts.
With this technique a short laser pulse illuminates a scene, and the intensified CCD camera opens its high speed shutter only for a few hundred picoseconds.
Depth information may be partially or wholly inferred alongside intensity through reverse convolution of an image captured with a specially designed coded aperture pattern with a specific complex arrangement of holes through which the incoming light is either allowed through or blocked.