DEVICE FOR MEASURING DISTANCE BETWEEN HEADREST AND HEAD, METHOD FOR MEASURING DISTANCE BETWEEN HEADREST AND HEAD, HEADREST POSITION ADJUSTING DEVICE, AND HEADREST POSITION ADJUSTING METHOD

A headrest position adjusting device 100 includes a distance measuring device 10 and a drive motor unit 30, and the distance measuring device 10 includes a plurality of sensing electrodes 11 to 15 and a detecting circuit 20. The detecting circuit 20 includes a plurality of capacitance sensing circuits 21 to 25 connected one-to-one to the sensing electrodes 11 to 15 and an arithmetic processing circuit 28, and the drive motor unit 30 includes a motor driving circuit and a drive motor. Based on the detected capacitance values, the detecting circuit 20 calculates a distance calculation angle ¸ formed by points representing the positions and output values of the sensing electrodes 15 and 11 located at the highest and lowest positions and a point representing the position and output value of the largest output value, and thereby measures an electrode-head distance L. A position adjusting operation for a headrest 43 is performed based on the measurement result.