| 摘要 |
PROBLEM TO BE SOLVED: To provide a mobile device with lighting function that can suppress the power consumption of a lighting device of the mobile device. SOLUTION: The mobile device is provided with a liquid crystal display panel 42, a light guide plate 43, light emitting elements 44a-44c, a luminous sheet 45, and light receiving elements 46a, 46b. The light guide plate 43 receives a light from the light emitting elements 44a-44c and the luminous sheet 45 and makes the light on the plate incident onto the liquid crystal display panel 42. The light receiving elements 46a, 46b detect the light from the luminous sheet 45. A control circuit 57 discriminates whether or not the luminance of the liquid crystal display panel 42 is sufficient under the condition that only the luminous sheet 45 lights the liquid crystal display panel 42 in response to the luminous quantity detected from the luminous sheet 45 only. When the control circuit 57 decides that the luminance is sufficient, the control circuit 57 puts out the light emitting elements 44a-44c. Thus, only the luminous sheet 45 can light up the liquid crystal display panel 42.
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