Our Active Stereo Vision System

This Section describes the active stereoscopic subsystem which provides the three-dimensional data to our system for automatically inspecting mechanical parts.
NOTE: Whilst this Section considers some specific active stereo problems, many of the other issues discussed are not specific to any particular three-dimensional data acquisition technique, and will be of general interest.
The main components of the Vision System are illustrated by the schematic diagram in Fig. 8.
 
Fig. 8 Schematic diagram of vision system
The vision system consists of:

• a matched pair of high sensitivity CCD cameras,
• a laser scanner all mounted on an optical bench to reduce vibration.

Initially the cameras of the system must be calibrated in order to

• determing the 3D position of them relative to some world coordinates
• focal length and lens distortion of the camera (+ lens etc.).
• Camera Calibration is described in my book.

Depth maps extracted from the scene by :

• Moving the laser stripe across the scene to obtain a series of vertical columns of pixels
• Triangulate Pixels to give the required dense depth map. The depth of a point is measured as the distance from one of the cameras, chosen as the master camera.
• Knowing the relevant geometry and optical properties of the cameras the depth map is constructed using the following method: