Patent ID: 7323867

Claim:
A thickness detecting apparatus comprising: a printed-circuit board including a pattern of a coil and a detection circuit which detects a signal representing thickness of an object detected; a detecting unit comprising a roller which detects thickness of the object by displacement of the roller; a thickness-representing unit disposed near the coil whose displacement amount represents the thickness of the object detected by the detecting unit, the thickness-representing unit including: a moving unit disposed near the coil; and a linking unit which links the detecting unit and said moving unit and displaces the moving unit in a direction opposite to a direction in which the detecting unit is displaced; and a spacer attached to the backside of the printed-circuit board and disposed between the moving unit and the coil, which causes an initial position of the moving unit to remain fixed relative to the coil, wherein the detection circuit supplies a high-frequency signal to the coil via a wiring connected to the coil and detects the thickness of the object based on the signal representing the thickness of the object which varies according to the displacement amount of the thickness-representing unit, the coil is disposed adjacent to the detection circuit on the printed-circuit board, and the coil is disposed at a position where the thickness-representing unit approaches.