The ornamental design for a head mounted displaydevice, as shown and described.
FIG. 1 is a front 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 view thereof; and,
FIG. 7 is a bottom view thereof.
The greyscale shading in FIGS. 1-7 is provided solely for the purposes of showing surface contours and to assist in visually delineating different elements of the design from each other. None of the shades of greyscale shading are not intended to indicate the color or relative darkness of any portion of the claimed design. The broken line showing of portions of the head mounted display device in FIGS. 1-7 represents environmental subject matter and forms no part of the claimed design. Portions of the head mounted display device that are obscured by the rear half of the headband and are not visible in any other view form no part of the claimed design.