I found the solution, so I think I should write here for other ones later.
First I download the source code of box2dlights. Then open BaseLight.java and find "segments" member variable. This variable contains all information about what I was finding. This code below is just for debugging purpose:
//Only first two elements are positions
float vertices = new float[spriteLight.segments.length/2];
int count = 0;
for (int i=0;i<spriteLight.segments.length;i+=4)
vertices[count++] = spriteLight.segments[i];
vertices[count++] = spriteLight.segments[i + 1];