The ornamental design for a head mounted display, as shown and described.
FIG. 1 is a perspective view of a head mounted display and controller showing our new design.
FIG. 2 is a bottom plan view thereof.
FIG. 3 is a top plan view thereof.
FIG. 4 is a left elevational view thereof.
FIG. 5 is a right elevational view thereof.
FIG. 6 is a front elevational view thereof; and,
FIG. 7 is a rear elevational view thereof.
The broken line showing in the drawings discloses unclaimed subject matter and forms no part of the claimed design. The broken line showing of a controller, text and graphic indicia is for environmental purposes only and also forms no part of the claimed design.