PLANE LIGHT SOURCE DEVICE, A LIQUID CRYSTAL DISPLAY DEVICE AND A DISPLAY DEVICE, PARTICULARLY CONCERNED WITH EXACTLY CONTROLLING BRIGHTNESS

摘要

PURPOSE: A plane light source device, an LCD device and a display device are provided to form an optical sensor for detecting a light and a shielding member for shielding a light incident at more than certain angle in horizontal direction, and to feed back a detected value to increase/decrease lightness of a light source, thereby suppressing time and temperature changes of brightness and chromaticity. CONSTITUTION: A light guide plate(2) introduces a light incident from an incident surface(2c). The light guide plate(2) has printed dots on a lower surface(2b), and comprises a diffusive portion(13) for diffusing the incident light. An optical sensor(4) receives a light incident from a side(2e) of the light guide plate(2). A shielding member(9) is located in front of the optical sensor(4). The shielding member(9) has pin holes to shield a light which is incident at more than certain angle in a direction of an opposing surface(2d) from the incident surface(2c) in the optical sensor(4). Lightness of LEDs(1) is controlled based on the light detected by the optical sensor(4).