hi,
A low cost PC webcam, with IR filter removed.
Tap into the hori/line sync signals and video signal, look for the minimum video signal that occurs as the 'black target' is scanned.
This will give you an indication of the X,Y coord on 2*2 mtr plane.
Use these coords in a PIC controller to drive the aiming laser pointer.
or
Using the same PC webcam with an aperture iris that allows a very small angle of view, scan the 2*2m plane from top left to bottom right as a X,Y raster, the same mechanism drives the aiming laser
As the video signal falls to near zero on the black target, fire the aiming laser.
What you are trying to do is not easy.