The Principle

A Virtual Tape Measurer(VTM) is a system combining stereoscopic video and stereoscopic graphics. The 3D coordinate of a feature point in the stereo scopic viewing range can be recovered based on the knowledge of the camera setup for stereoscopic video. By obtaining the 3D coordinate of two or more points, this system can be used as a tape measurer to measure the distance in the space.

The measurement accuracy of VTM depend on the camera setup, the designed working range, and the object feature in the view. In one of our prototype system, an error of 3mm has be reported with the measurement range up to1m. A test on VTM for an Operating Microscope indicated a bias of 0.3mm and an imprecision of 0.6 mm.
A detailed accuracy analysis is available on a PAPER : 3D MEASUREMENT IN ROV VIDEO INSPECTION

The Applications

1. Video-based inspection: VTM can be easily added onto the existing video-based inspection system, to provide stereoscopic inspection and accurate 3D distance measurement function.
2. Microscope surgery: VTM could be used with with an Operating Microscope in surgery.
3. Accident recovery: VTM can be used in (vehicle) accident recovery, where a stereoscopic video camera is used to record the scene on site. The detailed 3D distance analysis could carried out later based on the video recorded.