Rotation operation device

A rotation operation device comprising:

• a rotation operation section having a cylindrical shape and rotationally operable by an operator around an axis of the cylindrical shape;
• a plurality of recessed and projecting sections arranged on an axial end surface or a peripheral surface of the rotation operation section and having recesses and projections in a circumferential direction of the rotation operation section;
• a conductive section made of a conductive material, having a protruding section protruding toward each of the recessed and projecting sections and an elastic section that biases the protruding section by elasticity to each of the recessed and projecting sections, and movable in a recess-and-projection direction by each of the recessed and projecting sections when the rotation operation section rotates;
• an electrode section disposed so as to face the conductive section and changing a capacitance in accordance with a movement of the conductive section;
• and
• a detecting section detecting the change in the capacitance, wherein:
• three or more sets of combination of the recessed and projecting sections, the conductive section, and the electrode section are provided;
• the conductive section in each set is moved in turn by a respective recessed and projecting section in the recess-and-projection direction at a different timing with regular intervals;
• and
• the detecting section detects a rotation direction and a rotation quantity of the rotation operation section by means of a combination pattern of the change in the capacitance provided by the electrode section,
• wherein the recessed and projecting sections, the conductive section, and the electrode section in each set of the combination are arranged in a concentric manner.