Are there Tripods to film the bottom when writing on a paper? I would like to make some short movie clips explaining how algorithms work. To do so, I would like to film how I write / scribble on the paper.

Are there tripods which support filming what is directly below the camera or should I tinker such a tripod myself? In case you recommend building it myself: How is this standard "mount" at the bottom of each digital camera called? (So that I can buy something to fixate the camera.)

(I have a Lumix DMC TZ41 digital camera. Do movie cameras have other "mounts" for tripods than digital cameras?)

Some online courses (Udacity, Coursera) make something similar / exactly what I would like to do. See Programming - CS101 - Udacity for example:
There are a number of photo tripods that allow you to invert the center column.  When inverted, the camera sits between all the legs and can be pointed down.  Another tripod design has a center column that can also be shifted to a horizontal position.  This allows greater flexibility in terms of distance from the subject (and it also means you only have to shoot between the front two legs, rather than inside all three).