The ornamental design for an illuminationdevice, as shown and described.
FIG. 1 is a perspective view of an illumination device showing our new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a front view thereof;
FIG. 7 is a back view thereof; and,
FIG. 8 is a front view of the illumination device in its environment.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings depict environmental structure and form no part of the claimed design.