| 摘要 |
<p>PROBLEM TO BE SOLVED: To exactly detect the brightness of a face by external light by turning off the light when the brightness of face position is stronger than a specified value and immediately turning on the light when weaker than it. SOLUTION: In front of a fixing plate 21 fixing a movement 25, a light guide plate 31 is provided and a luminous diode illumination means 33 is provided inside a front glass 15 and on the back side of the front frame 17. A light guide plate 31 randomly reflects the light of the illumination means 33 on the back side and lightens the whole face formed in front of the light guide plate 31. The photoelectric transducer of a brightness detection means 43 fixed on the face connects to a turning control means 41 provided on the back side of the fixing plate 21, which turns on the luminous diode with the lighting control signal. This control means 41 outputs an operation voltage at every specified time to a brightness detection means 43, and terminates (outputs) the lighting control signal when the detected value of the output voltage of the brightness detection means 43 at this moment is more (less) than a specific value. That is, when the brightness of the face position is more than the specified value, it turns on, and when less, it immediately turns off.</p> |
