DEVICE FOR MEASURING THE DISTANCE BETWEEN A HEAD AND A HEADREST, HEADREST POSITION-ADJUSTMENT DEVICE USING SAID DEVICE, METHOD FOR MEASURING THE DISTANCE BETWEEN A HEAD AND A HEADREST, AND HEADREST POSITION-ADJUSTMENT METHOD USING SAID METHOD

Disclosed is a headrest position adjusting device accurately measures the distance between a head and a headrest without being affected by external noise, prevents unnecessary movements of the headrest, and automatically adjusts the position thereof. Said headrest position adjusting device (100) is provided with a distance measuring device (10) and drive motor units (30A and 30B). The distance measuring device (10) is provided with a plurality of detection electrodes (11 to 15) and a detection circuit (20). The detection circuit (20) is provided with a plurality of capacitance detection circuits (21 to 25) and a computation circuit (28). The computation circuit (28) uses capacitance values, position information from the detection electrodes (11 to 15), and a high-degree function with a degree of at least 3 to compute a high-degree curve in a two-dimensional coordinate system with capacitance on the y-axis and detection-electrode position on the x-axis. The computation circuit computes the highest-degree coefficient of the aforementioned high-degree curve and determines the distance (L) between a head (49) and a front part (43c) of a headrest on the basis of the computed highest-degree coefficient. On the basis of the measurement result, the headrest position adjusting device (100) moves the front part (43c) of the headrest towards the front or back of a vehicle.