| 摘要 |
PURPOSE:To obtain display of always optimum brightness by inputting the output of a brightness and darkness detecting element to the input port of a microcomputer and switching the time for on without changing the period of a scanning signal so as to meet bright and dark states. CONSTITUTION:A phototransistor 11 receives light and the equiv. resistance between terminals is small in the case of daytime. The voltage taken into the input IN 1 of the microcomputer 12, then, falls to a low potential. The blanking time is, thereupon, set at, for example, 0.5mS. On the other hand, the phototransistor 11 does not receive the light and the equiv. resistance between the terminals is large in the case of nighttime. The voltage taken into the input (IN 1) of the microcomputer 12, then, rises to a high potential. The blanking time is, thereupon, set at, for example, 4mS. The brightness of the display is automatically changed to meet the ambient brightness in this way and the always optimum brightness is obtd.
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