2d Object tracking

I have a platform that is Three foot by three foot, and I am trying to figure out a way to track multiple different objects and have the system know which object is which. I am trying to keep it all contained below the platform surface so i would not like to use a camera tracking system. Do you have any ideas as to what may work?

A lot of variables here...

By 3 objects...do you mean 3 of the same object? 3 different coloured objects? Different sets of 3 objects?

i meant a base platform that is three foot by three foot and have objects on top of it being tracked
and any number of objects.

One way mirror and camera tracking?

That's a cool idea but i don't think it will work for what i am doing. I forgot to explain that this surface will be divided into 1" x 1" squares with LEDs in them and they will react to specific objects in predefined ways. I was thinking maybe rfid but i don't know how well that would work.