Hollow Planar Illuminating Apparatus

A hollow planar illuminating apparatus comprising:

• a hollow unit case;
• a light reflection surface member disposed on a bottom side of the unit case;
• a light-emitting surface member disposed on a top side of the unit case, facing the light reflection surface member;
• an LED light source disposed at end portion of a hollow light guide region sandwiched between the light-emitting surface member and the light reflection surface member and arranged with a plurality of red, green and blue LEDs aligned, each of which emits a single color;
• an LED collimator disposed in approximately parallel with the LEDs aligned and collecting the light from the LED light source so as to be parallel with a surface of the light-emitting surface member of the unit case;
• a color sensor disposed on the light reflection surface member in the vicinity to the LED collimator and individually measuring an illuminance of each of red light, green light and blue light among the light incident into the hollow light guide region from the LED light source;
• and
• an LED brightness control circuit for controlling light emission intensity of each of the red, green and blue LEDs of the LED light source, based on each illuminance of red, green and blue colored light measured by the color sensor.