Head restraint position adjusting device using a distance measuring apparatus and the same between the headrest and the head, and the distance measuring method and a head restraint position adjusting method using the same between the headrest and the head

Accurately measure the distance between the headrest and the head without being affected by external noise, automatically adjust its position to prevent unnecessary movement of the headrest. Head restraint position adjusting device 100 includes a distance measuring device 10, the drive motor unit 30A, a B. Distance measuring device 10 is provided with a plurality of sensing electrodes 11 to 15 and the detection circuit 20. Detection circuit 20 includes a plurality of capacitance sensing circuits 21 to 25 and the arithmetic processing circuit 28. Arithmetic processing circuit 28, the position information of the capacitance value and the sensing electrodes 11 to 15, using a high-order function of the third order or more, y-axis electrostatic capacitance value, the position of the detection electrode and x-axis on a two-dimensional coordinates, the distance between the head rest front portion 43c and the head 49 on the basis of the highest order coefficients leading coefficient is calculated, the calculated in the high-order curve to calculate the high order curve L to determine. Head restraint position adjusting device 100, based on the measurement result, to move the head rest front portion 43c in the forward or backward direction of the vehicle.