I have a rectangular raster image in ArcMap. 

How can I produce a polygon which is just the extent of the raster image? 

That is, I want to have a polygon layer with a single quadrilateral which is the edge of the image.

I've tried simply doing a Raster->Polygon conversion, but this tries to use the data in the image to generate the outline - all I want is the outline of the edge of the image.

I'm using ArcGIS Desktop 10.