To provide an optical device which can improve directionality of light emitted forward from a reflecting surface positioned near a light source.
The optical device 60 for a plane light source which emits from a front surface light entering from a side surface is provided with a semiconductor light emitting unit 30, a light guide plate 3 which has a light incident surface 3c matching the side surface, a light emitting surface 3a matching the front surface and a plurality of reflecting surfaces 27 arranged in separation along an axis x, crossing at right angles with the light incident surface 3c and which guides the light incident from the light incident surface 3c and from the semiconductor light emitting unit 30 to the light emitting surface 3a through the plurality of the reflecting surfaces 27, and a light shielding member 40 which is arranged between the light incident surface 3c and the semiconductor light emitting unit 30 and which has a slit 41 which transmits the light from the semiconductor light emitting unit 30 to the light incident surface 3c. An incident light angle range from the semiconductor light emitting unit 30 to each of the reflecting surfaces is set up by an opening width of the slit 41 along a thickness direction of the light guide plate 3.
SUGIYAMA TAKASHI
KOBAYASHI NAOHIRO
