| 摘要 |
PURPOSE:To give display at luminance or illuminance easy to see at all times by increasing or decreasing luminance or illuminance of a display section according to ambient illuminance and changing in a specified pattern only when the rate of variation of ambient illuminance exceeds specified upper and lower limits. CONSTITUTION:A detection signal V from an illuminance sensor 44 that detects illuminance around a driver's seat is supplied to an illuminance control device 45, and a lumiance control signal is outputted to adjust luminance of a color cathode-ray tube. A differentiating circuit 47 differentiates the signal V from the sensor 44 and supplies a signal that indicates the rate of variation of ambient illuminance to a discriminating circuit 48. On receiving the rate of variation signal, the circut 48 outputs discriminating signals S1, S2 only when upper and lower limits set to fixed values are exceeded. A control circuit 46 outputs a signal h' that changes luminance of the cathode-ray tube 3 in a fixed pattern to a driver 21 only when the circuit 46 is receiving discriminating signals S1, S2 from the circuit 48. |
