Finally vloadn works, but unfortunately I have to copy to only one vector, not an array of them:
__global float* imagen0
...
long pix = get_global_id(0);
if (pix==0)
{
float16 vv=vload16(0,imagen0);
printf("===GPU vv: %6v16f \n",vv);
}
if (pix<16)
printf("imagen0[%2i]=%6f",pix,imagen0[pix]);