How to track motion of a moving ovendoor
I am not fully aware of the context of this oven door; but I would like to contribute a suggestion.

How about a quality potentiometer at the hinge of the door? Consider this, you get both the position and the velocity of the door this way; this method is simple and robust. Obtaining the position of the door is trivial, through some testing and measuring, you could find what values the pot outputs at given inputs, or door positions. 

Also, if you differentiate the position with respect the time (in practice, you can simply divide the rate of change in position you obtain over the rate of change in time), you would get the angular velocity. Then from there you can calculate the velocity the door is traveling at.



From the picture above, the angular velocity would be little omega. V is the velocity the end of the door travels. V, obviously obtained with angular velocity multiplied by radius.