| 摘要 |
<P>PROBLEM TO BE SOLVED: To control backlights when, for example, a photodetector is temporarily covered with a hand by mistake during operation and to choose whether control of the backlights is performed or not. <P>SOLUTION: A user is made to select whether lighting of the backlights should be controlled or not and his or her selection is registered in a memory 15. If control of lighting is registered, every time key operation is performed, brightness of the surrounding area and lighting/extinction of the backlights is detected and judgement is made on whether it is daytime or nighttime by checking the actual time against daytime and nighttime data registered in the memory 15. It is judged that conditions of lighting are satisfied when the brightness of the surrounding area is less than a threshold value if the backlights light in the daytime or if it is nighttime or when the brightness of the surrounding area less than the threshold value is successively detected for predetermined times if the backlights are off in the daytime. The backlights 13A and 13B are turned on in such a way that the lower the brightness of the surrounding area, the darker they are. If no next key operation is performed within a predetermined period of time after lighting, the backlights 13A and 13b are turned off. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
