The ornamental design for a headlamp, as shown and described.
FIG. 1 is a perspective view of a first embodiment head lamp in accordance with the present invention, wherein a perspective view of a second embodiment head lamp in accordance with the present invention is a mirror image thereof;
FIG. 2 is a front elevation view of the first embodiment head lamp, wherein a front elevation view of the second embodiment head lamp is a mirror image thereof;
FIG. 3 is a right side elevation view of the first embodiment head lamp, wherein a left side elevation view of the second embodiment head lamp is a mirror image thereof; and,
FIG. 4 is a top plan view of the first embodiment head lamp, wherein a top plan view of the second embodiment head lamp is a mirror image thereof.
The rear, bottom and left side views of the first embodiment head lamp, and the rear, bottom and right side views of the second embodiment head lamp form no part of the claimed design.