| 摘要 |
PROBLEM TO BE SOLVED: To permit a user to change and adjust the lightness on the panel face of a liquid crystal display, i.e., the brightness of the back light, so as to generate a visibility in accordance with the service environment. SOLUTION: A comparator 12 compares the level of a triangular wave or pseudo-triangular trapezoidal wave produced by integrating the dimmer input signals with the level of the DC voltage signal complying with the ambient light and emits the dimmer signal which has been subjected to the pulse width modulation, and the brightness of a fluorescent tube 2 as the back light of a liquid crystal display is controlled. When the lightness of the area surrounding the liquid crystal display varies, the lightness of the fluorescent tube 2 accordingly varies automatically, and also the lightness of the back light is varied according to the visibility or the taste of the user by changing the dimmer input signal, and it is possible to optimize the visibility of the liquid crystal display in different environments. |
