Disclosed herein are systems and methods for a lamp assembly having a novel design for fitting two or more tube-shaped lamps end-to-end. In order to change a reflectance of a portion of a reflection sheet 110, 111 with gradation in response to light and dark of portions of an image displayed on a display panel 201, a control mechanism 202 arranged to control the display panel 201 is provided. The sidewalls of the reflecting members work as a wave reflector for reflecting high frequency waves that propagate inside the top plate in the radius direction.