The ornamental design for a head mounted display, as shown and described.
FIG. 1 is a front, top and right side perspective view of a head mounted display showing our new design;
FIG. 2 is a front, bottom and left side perspective view thereof;
FIG. 3 is a rear, top and left side perspective view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a right side view thereof; and,
FIG. 9 is a left side view thereof.
The broken lines illustrate portions of the head mounted display that form no part of the claimed design. The oblique line shading shown in the drawings indicates translucent parts. No claim is made to any elements inside the translucent parts.