FIG. 1 is a front view of a headlamp showing my new design; FIG. 2 is a rear view of a headlamp thereof; FIG. 3 is a left side view of a headlamp thereof; FIG. 4 is a right side view of a headlamp thereof; FIG. 5 is a top view of a headlamp thereof; and, FIG. 6 is a bottom view of a headlamp thereof.