Abstract: A chucking mechanism which reliably attaches and detaches a disc with high precision. The chucking mechanism includes a shaft for supporting the disc and having a tapered recess, a tapered cone adapted to fit in the tapered recess, and a piston for moving a rod, attached to the tapered cone, through a hole formed in the shaft. The mechanism also includes an O-ring having a variable diameter and being disposed between the tapered cone and the tapered recess. As the piston moves the tapered cone in a first direction, the tapered cone gradually expands the diameter of the O-ring to press and fix the disc. As the piston moves the tapered cone in a second direction, the diameter of the O-ring gradually contracts to move out of contact with the disc so as to release the disc.

Abstract: A chucking mechanism which reliably attaches and detaches a disc with high precision is provided. The chucking mechanism includes a shaft for supporting the disc and having a tapered recess, a tapered cone adapted to fit in the tapered recess, and a piston for moving a rod, attached to the tapered cone, through a hole formed in the shaft. The mechanism also includes an O-ring having a variable diameter and being disposed between the tapered cone and the tapered recess. As the piston moves the tapered cone in a first direction, the tapered cone gradually expands the diameter of the O-ring to press and fix the disc. As the piston moves the tapered cone in a second direction, the diameter of the O-ring gradually contracts to move out of contact with the disc so as to release the disc. Since the diameter of the O-ring gradually increases along the tapered portion, the inner peripheral edge of the disc is prevented from being distorted by suddenly being pressed when it is fixed.

Abstract: A positioning apparatus includes a movable member, an actuator for driving the movable member in a moving direction, a gravity guide having a reference surface for supporting the movable member in a gravity direction, a yaw guide for guiding the movable member from one side thereof in the moving direction by means of a guide surface perpendicular to the reference surface, and a measuring device for measuring a position of the movable member in the moving direction. A distance from a measuring position at which the measuring device measures the position of the movable member to the guide surface is longer than a distance from a driving position at which the actuator drives the movable member to the guide surface.

Abstract: A scale, which is provided for use with a displacement sensor, has a high degree of freedom and is capable of being manufactured at a low cost. The scale includes a graduation section and a base board which is formed separately from the graduation section and which is bonded to the graduation section. By bonding a graduation section to a separate base board, a single graduation section can be used for scales of varying lengths. Sufficient rigidity is provided by bonding a separate base board to the graduation section.

Abstract: An optical type sensor has a light emitting element, a light receiving element, at least one optical element acting on a light beam emitted from the light emitting element, in an optical path till the light beam enters the light receiving element, and a spacer member disposed to define a spacing between the light emitting element and/or the light receiving element and the at least one optical element, the spacer member having a structure for being mounted to other member.

Abstract: A rotation detecting apparatus includes a grating portion provided on one of two objects for which relative rotation is to be detected, a light-emitting portion provided on the other of the two objects, and a light-receiving portion provided on the other object. The grating portion has at least one multi-helix diffraction grating. The light-receiving portion receives a beam emitted from the light-emitting portion and then traveling by way of the multi-helix diffraction grating. Information of relative rotation of the two objects is detected through light reception of the light-receiving portion.