Camera calibration: the projection matrix

Question

I have been working on a 3D scanner for a while now and I still have some questions about the projection matrix I want to clear out before I continue.

I understand the fact that this matrix describes the relation between the camera coordinate system and the world coordinate system. Yet I don't understand why all the calibration software packages give you this matrix? Does the software just picks a random world coordinate system in space and does it calculate the matrix afterwards?

I was thinking it would be way easier to choose the world coordinate system by yourself (if it is even possible). My plan is to create a scanner where the object stands still on a static surface and where the camera + laser moves around the object in a circular movement. If it would be possible to create your projection matrix this way so the world coordinate system is nicely placed in the middle of the static platform.

If I'm not very clear, let me know and I'll add an image.

Hopefully someone can clear things a little bit up for me so I can make some progress :).

Kind regards Ruts

Answer 1

The matrix after camera calibration give you relation between two cameras (stereo vision) and it consist of intrinsic and extrinsic of camera. The matrix convert your image to 3D coordinate system and give you depth of objects.

The are number of video on youtube about 3D scanner. http://www.youtube.com/watch?v=AYq5n7jwe40 or http://www.youtube.com/watch?v=H3WzY8EWM9s