The ornamental design for a headlamp, as shown and described.
FIG. 1 is a front perspective view of a head lamp showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a perspective view of the head lamp in used with an unclaimed glass cover.
The broken lines in the drawings depict portions of the head lamp that form no part of the claimed design. The dash-dot-dash lines are for annotation purposes only and form no part thereof.