An improved system and method for controlling the brightness of indicator lights used on portable information handling systems. Correct luminance characteristic of the LCD panel is calculated by making a correction of the data thus obtained using a predetermined condensing function. The eccentric cams are arranged side by side in a direction of an inclined axis inclined with respect to an input rotation axis at an inclination angle in a manner that respective center axes of the eccentric cams are parallel to the inclined axis and decentered in directions opposite to each other from the inclined axis. The plurality of first coaxial patterns are disposed on the transparent conductive layer and surround the active area.