In a method of sharpness enhancement, an input signal is filtered to obtain a filtered signal, the filtered signal is multiplied by a controllable fraction to obtain multiplied signals, and the multiplied signals are added to the input signal. A control unit controls unlocking of a vehicle door by determining whether the detected electronic key is an authorized one. The two polysilicon portions are separated by a gap. Stationary water molecules 1, such as those in fat cells, are heated. The warning control ECU establishes the early-warning mode when the eye-closing period of the driver becomes equal to or greater than a first threshold value, and thereafter maintains the early-warning mode until the eye-closing period of the driver falls below a second threshold value.