The ornamental design for a head mounted displaydevice, as shown and described.
FIG. 1 is a perspective view of a head mounted display device showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a reference view thereof showing the state that the subject design has been worn around the user's neck;
FIG. 9 is a reference view thereof showing that one side of the display part (optical module) can be separated front the neck-band and the subject design can be adjusted to the face shape of the user by swivelling the display part up and down; and,
FIG. 10 is a reference view thereof showing that one side of the display part (optical module) is separated from the neck-band and then attached to the user's glasses.
The broken lines depict portions of the head mounted display device that form no part of the claimed design.