Position detection device

摘要

In a position detection device that comprises a first substrate (1), a second substrate (2), an alternating current (AC) bridge (30) comprised of four variable capacitors (31, 32, 33, 34), and a detection circuit (6), the first and second substrates have a flat first electrode surface (1a) and a flat second electrode surface (2a), respectively, the second substrate is mounted opposite the first substrate with the first electrode surface opposite the second electrode surface and separated from the second electrode surface by a minute gap and the second substrate and the first substrate are movable relative to one another in the plane of the electrode surfaces. Each of the variable capacitors is composed of a first capacitor electrode (3a, 3b, 3e, 3f) located on the first electrode surface and a second capacitor electrode (3c, 3d, 3h, 3g) located opposite the first capacitor electrode on the second electrode surface. The capacitor electrodes (3b, 3d; 3f, 3g) of two of the variable capacitors (32, 34) are long capacitor electrodes, and the capacitor electrodes (3a, 3c; 3e, 3h) of the remaining two (31, 33) of the variable capacitors are short capacitor electrodes. The short capacitor electrodes are shorter than the long capacitor electrodes in the detection direction of the position detection device. The long capacitor electrodes (3b, 3f) located on the first electrode surface are offset in the detection direction relative to the long capacitor electrodes (3d, 3g) located on the second electrode surface. The detection circuit derives a position-indicating signal from the output voltage generated by the AC bridge. The position-indicating signal represents the relative position of the first substrate and the second substrate in the detection direction.