Patent ID: 7950162

Claim:
A tilt sensor comprising: a light emitting element and a pair of light receiving elements spaced from each other in a surface direction of a detection target plane; a rolling member adapted to take any one of a complete light shielding position, a partial light shielding position and a light unshielding position, the complete light shielding position being a position at which the rolling member blocks the light emitted from the light emitting element so that the light does not reach neither of the paired light receiving elements, the partial light shielding position being a position at which the rolling member blocks the light emitted from the light emitting element so that the light reaches only one of the paired light receiving elements, the light unshielding position being a position at which the rolling member fails to block the light emitted from the light emitting element so that the light reaches both of the paired light receiving elements; a case formed with an inner space for accommodating the rolling member; and an irregular ceiling surface exposed to the inner space; wherein the rolling member is a cylindrical member having a central axis perpendicular to the surface direction; and wherein the irregular ceiling surface is provided with a plurality of projections each being smaller in area, when viewed in a direction perpendicular to the surface direction, than the rolling member.