I have an idea in my mind which needs the exact distance between the two objects(may be a transmitter receiver pair) to be calculated. One of them is fixed at its respective location and the second one is mobile.They both are not necessarily should be in line of sight. The thing over here is that whole setup should come under a range of 1m2(even this is large).
Are you actually trying to find the relative position of the moving object, rather than the distance to it? Over what sort of range, and in what environment, and to what resolution?
What moves the second point? Can you measure that? An X-Y table or arm gives many options.
The only problem with this would be that the detectors would always have to stay in the same orientation to the light source so as to provide the same detection cross section (can you get detectors that this wouldn't impact? Probably)
Consider a rectangular white page of say 1m x 1m. Now let us fix the sensors(whichever would be more appropriate) at the corners of this page(I am ready to use more no. of sensors to increase the precision and accuracy). let us assign coordinates as (0,0)(1,0)(0,1)(1,1) to this sensors. Now the the object can be both a simple like a pen or can be some sort of transmitter or led inbuilt to it or whatever(depending upon the method used) .So here i need to calculate the relative distance of that pen wrt say (0,0)...Any suggestions....
Well when you put it that way.... put a webcam on the ceiling point straight down, analyse the photo.