Digital signal integrity & grounding
If this is an LCD display panel (like and old laptop), they are typically driven bit serial with LVDS driver chips (like the DS90CF563 http://www.ti.com/lit/ds/snls107e/snls107e.pdf ), or even current signalling - mostly because the LCD cable was the biggest RF radiator in the entire device. 

If it's current signalled you may find that the input to the panel isn't just a resistor, but a current sink driven from a negative voltage. 

You could use a line receiver (eg an SN75HVD12 http://www.ti.com/lit/ds/symlink/sn75hvd12.pdf ) which will drive your fpga directly and happily cope with all sorts of unpleasant voltages on the input.