Flat panel display device and stereoscopic display device

A stereoscopic display device, wherein:

• the stereoscopic display device comprises a liquid crystal lens grating, a backlight system, and a display panel, the liquid crystal lens grating being arranged on a light exit surface of the display panel;
• and
• the backlight system comprises a reflector plate and a back frame that carries the reflector plate, wherein the back frame comprises at least two primary assembling pieces, the at least two primary assembling pieces being joined to form a main frame structure of the back frame;
• and the reflector plate comprises a foamed plastic substrate layer and a reflection layer formed on the foamed plastic substrate layer;
• wherein the at least two primary assembling pieces comprise a first primary assembling piece and a second primary assembling piece, the first primary assembling piece having an end connectable to an end of the second primary assembling piece for jointing the first and second primary assembling pieces, the end of the first primary assembling piece forming at least two joint sections, each of which has a structure mating the end of the second primary assembling piece, the end of the second primary assembling piece being switchably jointed to one of the at least two joint sections of the first primary assembling piece so that the second primary assembling piece is connected to the first primary assembling piece in a position-adjustable manner.