Abstract: An apparatus for driving a collapsible lens mount having several telescoping segments includes, for each movable segment, a transducer that expands and contracts responsive to a wave pulse and a drive shaft coupled to the transducer. By varying the wave pulse conditions, the expansion and contraction are made to occur at different rates. A coupling member on each segment frictionally engages the drive shaft and transmits movement of the drive shaft during relatively slow drive shaft movements to the lens segment. The apparatus may also include a lens hood driven by the transducer and drive shaft apparatus of the invention.

Abstract: A supporting apparatus for an optical scanning apparatus includes an optical source which emits an optical beam. A deflector deflects the optical beam from the optical source. A focusing lens focuses the optical beam from the deflector. An optical housing is provided with the optical source, deflector and the focusing lens. A positioning device supports the optical housing and positions the optical housing, relative to a frame. An adjusting device moves an end of the optical housing in a sub-scanning direction so that an inclination of the optical housing in the sub-scanning direction can be adjusted.

Abstract: The invention is directed to an arrangement for displacing the parts of an objective with at least one adjusting ring 6. A fine adjusting ring 40 is also provided and there is no switchover device which must be actuated by the operator. The fine adjusting ring 40 is at standstill when it is not actively rotated by the operator. A coarse adjusting ring 6 is rotatably journalled in the housing 10 of an objective. A transmission or gearing for suitably fine adjusting this coarse adjusting ring 6 includes a sun gear wheel 1 mounted fixedly on the objective housing 10, a fine adjusting ring 40 which includes a shaft pin 4 on which planetary gear wheels 2 are journalled and an output gear wheel 3 rotatably mounted on the coarse adjusting ring 6 via a slip clutch 5.

Abstract: A zoom lens apparatus having a first pair of substantially parallel guide rods. A pair of carriage assemblies are mounted to the first pair of parallel guide rods each having lens element. A pair of lead screws are provided for driving the carriage assemblies. The screws are each mounted to the apparatus by a bearing block assembly such that the longitudinal axis of the lead screw is substantially parallel to the first pair of guide rods. The bearing block constrains the movement of the first lead screw along the longitudinal axis. A zero constraint threaded drive coupling is provided with each lead screw for moving the carriage along the guide rods. A motor is provided for rotating each of the drive screws.

Abstract: A Fourier transform optical apparatus for optically Fourier transforming an input image includes a spatial light modulator for displaying an input image, a light source for irradiating the input image on the spatial light modulator, a first convex lens and a first concave lens arranged near the spatial light modulator and a second convex lens arranged at the composite focal plane of the first convex lens and first concave lens. The respective focal lengths of these three lenses are determined to satisfy conditions such that a light ray passing an intersection of the spatial light modulator and an optical axis of the Fourier transform optical apparatus becomes a light ray parallel to the optical axis after passing the second convex lens and a light ray incident to the first convex lens in parallel to the optical axis is focused at the composite focal point of the first convex lens, first concave lens and the second convex lens.

Abstract: A biaxial actuator for an optical pickup wherein by the downward stroke of the lens holder being limited by abutment of the lens holder with the slide base and the adjusting plate and the actuator cover each being fixed to the slide base or by the actuator cover being fixed to the yoke and fixing elements for fixing the actuator cover to the yoke being provided at front and rear end portions of the actuator cover and the yoke dispersion in the focussing direction stroke of the lens holder is reduced, the stroke of the lens holder is not limited even when the lens holder is mounted diagonally, and the actuator cover is correctly positioned and firmly held with respect to the yoke with no looseness therebetween.

Abstract: A camera lens barrel for a camera includes first, second, third and fourth lens groups with a diaphragm located between the second and third lens groups. The second and third lens groups are connected, while the first, third and fourth lens groups can move relative to each other along the optical axis of the camera lens barrel. A diaphragm driver is positioned radially outside of the second lens group, while a lens shift driver device, including the horizontal and vertical lens shift drivers, is positioned radially outside of the third lens group. The diaphragm driver and the lens shift driver device are connected to a control unit via a flexible printed circuit. A power transmission extends from the diaphragm driver to the fourth lens group. The power transmission is connected to the diaphragm driver via a pin. When the pin is rotated, the angular rotation of a pin is transmitted to the fourth lens group to focus the camera lens barrel. Thus, the overall diameter of the camera lens barrel is reduced.

Abstract: Disclosed is a three dimensional projection system. A holder housing has upper and lower plates and a plurality of longitudinally inclined guiding holes inclined at predetermined angles about central axes of the upper and lower plates. First and second projecting lens holders have cylindrical shapes and are provided with projecting lenses in front sides thereof. Movable pins protrusively formed on upper and lower portions of the first and second projecting lens holders are provided. The movable pins are respectively inserted into corresponding longitudinally inclined guiding holes. A holder supporting plate has a pair of front and rear plates and a spacer. The front and rear plates are provided with first and second leg portions formed at both sides thereof and extended onto an upper portion of the upper plate, and third and fourth leg portions extended onto a lower portion of the lower plate. A driving motor for supplying driving power for transporting the projecting lens holders is provided.

Abstract: A guide device for a zoom lens barrel which includes a movable cylinder linearly guided in a direction of the optical axis of a zoom lens, a pinion rotatably supported on the movable cylinder, with a part of the pinion projecting from an outer surface of the movable cylinder. The guide device further includes a driving mechanism for rotating the pinion, a zooming mechanism for moving a plurality of lens groups of the zoom lens by rotation of the pinion to change a focal length, and a straight guide projection formed on an outer surface of the movable cylinder. The pinion is situated close to the straight guide projection.

Abstract: The optical system supporting device of the present invention comprises an optical element, a holding member for holding the optical element, a supporting member for displaceably supporting the holding member and a driving means for driving the holding member in a predetermined direction, wherein a holding part for gelatinous damping materials is provided on at least one place of the supporting member and a gelatinous damping material is disposed in the holding part. This optical system supporting device is small and light, and is excellent in cotrollability.

Abstract: A multi-lens optical device for use in an optical scanner including a lens holder having a viewing aperture, and a lens unit disposed in front of the viewing aperture, wherein the lens unit includes a lens holder, a plurality of lenses of different magnifying power respectively mounted on the lens holder, a reversible motor, and a reduction gearing driven by the reversible motor to move the lens holder, permitting one lens to be aligned with the viewing aperture for scanning.

Abstract: A vise like device that has a pair of oppositely disposed jaws is disclosed. This vise is used to true the roundness of camera lenses. The jaws form arcs of a circle that corresponds to the size of the lens being repaired. The jaws are threaded to protect the threads on the frame. Once the lens frame is secure on the jaws, the vise is slowly opened, pulling the frame around the jaws until the correct diameter is reached and the frame is round. This procedure saves time because the frame becomes true automatically as the vise is opened. Thus, there is no need to continuously check the roundness against a standard as the process continues. Moreover, this process is more forgiving because the frame is gradually and gently trued up. This gradual process also eliminates the need to remove any over correction to the lens shape. Finally, once the lens had be trued, filters and other accessories can again be attached to the lens.

Abstract: An apparatus and method for aligning the optical elements of a microscope are disclosed wherein a fixture is provided for locating and mounting a plurality of mirrors for reflecting an object image along an optical path to an adjacent eyepiece connected to the fixture by an eyepiece holder. The eyepiece holder includes an outer sleeve attachable to the fixture, an inner sleeve transversely movable within the outer sleeve for slidably receiving the eyepiece, and positioning means comprising a plurality of angularly spaced screws extending through the outer sleeve for engaging the inner sleeve, whereby the eyepiece may be aligned on the optical path by selectively adjusting the screws.

Abstract: A lens apparatus is disclosed for use with a firearm scope. The lens apparatus includes first and second polarized lenses that move relative to each other. When differently colored lens materials are used and when moved relative to each other, the color seen through the two polarized lenses changes. In affixing the first and second polarized lenses to the firearm scope, first and second connection assemblies are utilized. The two connection assemblies have first and second latch release members, respectively. The two latch release members are located on the right and left sides of a scope when a user is in the normal shooting position. Upon actuation of the latch release member, pivotal movement of the polarized lenses, relative to the firearm scope lenses occurs. Each of the two connection assemblies includes a sleeve member and a cap lid. The sleeve member is flexible to surround portions of the firearm scope and is made of a material different from the cap lid material.

Abstract: A microscope objective adjustable for different cover slip thicknesses includes an outer ring rotatable about an optical axis of the objective, an intermediate mount carrier having a plurality of inner lens mounts fixed thereto, and an inner correcting lens mount axially movable between a pair of fixed lens mounts. The correcting mount is coupled to the outer ring for rotation therewith by a follower pin extending through a curved cam slot in the intermediate mount carrier and into an axial groove in the outer ring, such that when the outer ring is rotated the correcting mount moves axially due to engagement of the follower pin with the cam slot and simultaneously rotates about the optical axis due to engagement of the follower pin with the axial groove.

Abstract: In a camera lens group having both glass and plastic lenses mounted in a lens frame, where at least one of the lenses is movable along the optical axis, a spacing member and a resiliently deformable member are each arranged in an interval between lenses in the lens group. The resiliently deformable member biases one of the lenses away from the spacing member, and the spacing member reduces the range of possible movement of the movable lens.

Abstract: A multi-lens changing mechanism is disclosed for use in optical scanners; it comprises: (a) a main mechanism having a bottom, first and second sides, and an aperture as an inlet for receiving light, each of the first and second sides having a magnetic means attached thereto; (b) a sliding lens carriage including at least two lenses, the sliding lens carriage being slidable within the main mechanism: and (c) a driving mechanism including a guide rod and a swinging arm. The guide rod is fitted at the bottom of the main mechanism, and is able to move back and forth. The swinging arm has a first end attached to the sliding lens carriage and a second end pivotally mounted to the main mechanism such that the swinging arm will swing when it is driven by the guide rod.

Abstract: A device for adjusting an air gap between lenses having a lens barrel. First and second lenses are disposed within the lens barrel, a spring provided within the lens barrel between the first and second lenses maintains the air gap between the first and second lenses, and a retainer is screw jointed to the lens barrel. The spring is compressed or expanded by tightening or loosening the retainer with respect to the lens barrel. The air gap between lenses can be adjusted to improve the lens performance and the focusing characteristic without dismantling the lenses from the lens barrel.

Abstract: An apparatus for setting the rotational torque of a screw mechanism including a frictional member which is positioned between a lens frame and a lens frame holder. The frictional member can be made of natural fiber, sponge, rubber, or styrene foam.

Abstract: An apparatus for adjusting the axial position of a lens includes a lens frame which holds the lens, and a lens frame holder which holds the lens frame to allow movement in the optical axis direction. A plurality of split screw engaging portions are provided between the lens frame and the lens frame holder, so that the lens frame and the lens frame holder are capable of being fitted together without rotating and are screw engagable with the split screw engaging portions.

Abstract: A lens mounting system (36) comprises a lens mount (53) having a cylindrical inner surface to define an internal cavity. An annular mounting member (46) projects into the cavity and has a fixed forward facing mounting surface (48). A mounting ring (52) threadedly engaged with the inner surface is selectively movable between a withdrawn position distant from the mounting member (46) and an advanced position adjacent thereto. A lens (40) for the system includes a forward facing optical surface (42), a rearward facing optical surface (44), and an annular mounting member (46) at an interface between the first optical surface (42) and the second optical surface (44).

Abstract: An apparatus for adjusting an intermeshing angle of a pin and feed screw in a mechanism in which rotational movement of a feed screw is converted to a linear movement of the pin. The apparatus includes at least one pin which is in mesh with the feed screw, and a linearly movable member which supports the pin and which moves in the axial direction of the feed screw. The linearly movable member includes an adjusting mechanism for adjusting the intermeshing angle of the pin and feed screw.

Abstract: An objective lens posture adjusting mechanism of an optical pickup capable of easily adjusting the objective lens posture. In order to adjust an inclination angle of an objective lens about two axes relative to an optical system support base, an intermediate base is superposed upon the optical system support base via first cylindrical surfaces, an object lens support base is superposed upon the intermediate base via second cylindrical surfaces having a center axis not parallel to a center axis of the first cylindrical surfaces, and the inclination angle of the objective lens about the two axes is adjusted by relative rotations of the first and second cylindrical surfaces.

Abstract: A device is provided for controllably moving an optical element such as an attenuator, into one of a plurality of positions. The device includes a rotatable, cylindrical member having a face cam that is an endless cammed surface for supporting and moving a cam follower. As the cammed surface is rotated, the cam follower resting upon it moves the optical element in a controlled manner. A gearing means in the form of a toothless planetary gear box is coupled to the cylindrical member and provides fine control over the range of movement of the device.

Abstract: A lens frame supporting mechanism includes a spherical surface that is a specified region of the outer surface of a lens frame for holding an optical system and that acts as a driven and supported member. The spherical surface is supported by spherical rotators serving as supporting driving members. The lens frame is driven to rotate by means of the spherical rotators that are in contact with the lens frame, thus shifting the orientation of the optical axis of the optical system. The lens frame is rotated while being restrained from rotating about the optical axis by means of a guide ditch and a guide pin formed in the spherical surface of the lens frame. This lens frame supporting mechanism has materialized a simple supporting mechanism and a compact lens frame, and realizes a reduced load to a rotation actuator.

Abstract: A common lens barrel can be detachably attached to a plurality of TV camera bodies each having at least one filter provided in front of an image pickup device. The filters of the respective camera bodies have different thicknesses, and the common lens barrel has a plurality of lens groups. The lens barrel includes a focusing mechanisms and a mechanism for varying a distance between specific lens groups of the plurality of lens groups in accordance with the thickness of the filter of the camera body to which the common lens barrel is attached.

Abstract: An electromagnetic actuator for moving a focusing lens along an optical axis includes a lens barrel having two supporting rails, a set of cylindrical inner and outer yokes incorporating a pair of magnets, a lens holder which holds the lens and is supported slidably on the supporting rails by means of a bearing device and rail guide provided on two arms of the lens holder, a coil wound on a bobbin which is fixed on the lens holder and located so that the coil is exposed to the magnetic field of the magnets inside the yokes. The yokes have cut portions, allowing the arms of lens holder to cut into the yokes when the lens is moved.

Abstract: A switching device for a multi-lens optical scanner, which comprises a body casing, a sliding lens seat and a driving mechanism; the feature of the switching device is that the power of a scanning device is used for driving a guide rod of the switching device so as to set the mechanism at a given position automatically, and provide an optical scanner with various resolving powers desired.

Abstract: An optical head of this invention includes: a light source emitting a plurality of beams from a plurality of emitting points; an optical system for focusing the plurality of beams on a recording medium; and an adjusting means for adjusting distances from the plurality of emitting points to the optical system, wherein the adjusting means includes a first member for supporting the light source and a second member for supporting the first member; the first member is rotatable around a central axis which is vertical to the plane including an optical axis of the optical system and the plurality of emitting points and passes through a point on the optical axis; and the second member is movable along a reference plane vertical to the optical axis.

Abstract: A photosensitive element is adjustably mounted on a device, including a base frame having a flat base and a ball socket perpendicularly extended from the flat base and defining a half-round recess, the flat base having a center through hole through the center of the half-round recess for the insertion of a photosensitive element being connected to a light source through an electric wire, a core member, which has a ball head at one end received and turned within the half-round recess, an outer thread at an opposite end, a longitudinal through hole aligned with the center through hole on the base frame, and a lens mounted within the longitudinal through hole, and a socket shell, which has an inner thread at one end threaded onto the outer thread of the core member, a longitudinal through hole aligned with the longitudinal through hole on the core member, and a lens set mounted within the longitudinal through hole and matched with the lens on the core member.

Abstract: There is disclosed an adjustable collimator assembly which utilizes a lens barrel member and a housing member which holds a laser diode at a fixed position. A portion of one of these members are received within a portion of the other member. These two members have a coacting member to provide a relative movement between them for adjusting the lens barrel member relative to the laser diode. The potion of the other member which receives the one member has an integral gripping means for gripping the one member to fix the position of the members relative to each other in order to fix the position of the lens barrel relative to the laser diode.

Abstract: A coupling device and associated method for coupling an unassociated afocal optical assembly to a night vision apparatus in order to alter the optical power normally associated with the night vision. The coupling device includes two separate adapter rings that threadably connect to each other. The first adaptor ring is sized and shaped to threadably engage the night vision apparatus proximate the objective lens of the night vision apparatus. The second adaptor ring is sized and shaped to screw onto the output end of the afocal optical assembly. Accordingly, when the first adaptor ring is joined to the second adaptor ring, the output end of the afocal optical assembly is optically aligned with the objective lens of the night vision apparatus. Consequently, the afocal optical assembly enhances the optical power associated with the night vision apparatus.

Abstract: An image forming apparatus has an optical device for image magnification change. The apparatus is provided with a fixed platen on which a document is placed, four reflecting mirrors and an exposure lamp by which the document is exposed and scanned, and a lens unit including a fixed-focus lens by which an image of the document is formed on an image carrier. An imagewise light emitted from a document is reflected by the first, second and third reflecting mirrors and is transmitted through the fixed-focus lens. The reflected light is projected into the image carrier by way of the fourth reflecting mirror at which the light transmitted by the fixed-focus lens is reflected. The lens unit accommodates the fixed-focus lens and is movable in the same moving direction as the first, second and third reflecting mirrors at the time of an image magnification change operation. A lens cam member is mounted on the lens unit.

Abstract: The apparatus is a laser transmitter and receiver unit with independent adjustment of the focus of each and preservation of precise parallel alignment between the two lines of sight. The transmitter laser and the receiver photodetector are each mounted in a precisely machined two part mounting assembly. The first part of both mounting assemblies includes an objective lens and is fitted against the same precise surface of a reference fixture. The second part of each mounting assembly, holding the laser or photodetector, is connected to the first part by means of precisely mated coaxial sliding cylinders, so that the laser or photodetector can be replaced on the fixture with high accuracy. Axial adjustment of the distance of the laser or photodetector from their respective objective lenses is furnished by spacer washers inserted between the two parts of the assemblies.

Abstract: An optical apparatus (2) has a first optical element (4, 4a) and a second optical element (5, 5a). The first optical element (4, 4a) is disposed in the same optical path (3) as the second optical element (5, 5a). A first optical assembly (6a, 6b, 8, 8a, 10, 10a, 20, 22, 24, 70, 72) is disposed between the first optical element (4, 4a) and the second optical element (5, 5a) along the optical path (3). The optical apparatus (2) has pneumatic adjusting means (40, 42) for pneumatically adjusting the position of the first optical assembly (6a, 6b, 8, 8a, 10, 10a, 20, 22, 24, 70, 72) along the optical path 3 such that the focal length of the optical apparatus (2) is changed.

Abstract: A multiple field of view sensor lens assembly suitable for inclusion in an infrared imaging system. The lens assembly includes a rotatable telescope 10 for providing first and second fields of view for the sensor, the first field of view being along a first axis thereof L and the second field of view being along a separate second axis T. A servo mechanism 30 is included for rotating the telescope 10 from a first orientation at which the first axis is aligned with the optical axis to a second orientation at which the second axis is aligned with the optical axis. In a preferred embodiment the inventive lens assembly is disposed to provide fields of view in opposing directions along the first axis L, and a third field along the second axis T.

Abstract: In a lens holding device, a plurality of protrusions of equal height are provided oppositely at the front and rear of the periphery of a plastic photographic lens. The plurality of protrusions are substantially equidistant. Three sets of stairs, each having a plurality of steps with a predetermined difference in height between adjacent steps, are provided at positions corresponding to the protrusions in a lens receiving member and a lens pressing member, between which the lens is sandwiched. The position of the lens can be adjusted from a most advanced position to a most retreated position along the optical axis by selecting a preferred step of each of the stairs.

Abstract: A precision linear actuator (10, 120, 140) is provided particularly adapted for accurately controlling the positioning of a lens element in the optical system of a guided vehicle such as a missile. The actuator includes a frame (12, 130, 142) rigidly affixed to the missile structure which includes a pair of bearing supports (30, 32) and a pair of separated guide pockets (24, 26). A lever (14, 122, 150) is installed within the frame (12, 130, 142) and is fixed to the frame by bearings (44, 46) which enable the lever to undergo slight rotation with respect to the frame. An actuator mechanism in the form of a voice coil (56), drive motor or other device is employed to drive the lever (14, 122, 150) to undergo its rotational motion. A lens holder (16) is installed within an open area inside the lever (14, 122, 150) and defines separated guide rails (76, 78, 80, 82) which enable it to be moved linearly with respect to the frame (12, 130, 142).

Abstract: An inclination adjusting device for an objective lens used for an optical information recording and reproduction apparatus with a reduced number of components for a small size and light weight is provided. An objective lens is held at an end portion of a plate spring. The other end portion of the plate spring is fixed to an adjusting board, which is supported in a manner so that it can tilt against a base on a spherical element as a support. The adjusting board is properly positioned with regard to the base by use of one guide pin. The adjusting board is tilted in the longitudinal direction of the plate spring and in the direction crossing the longitudinal direction by use of a first and second adjusting screws, respectively.

Abstract: A focusing mechanism for telescopes, microscopes and the like uses a tensioned strap circumscribing a pair of wheels in a generally S-shape whereby rotation of the wheels moves the eye piece of the scope to proper focus location.

Abstract: An optical data recording and reproducing apparatus including an objective lens for converging light onto an optical disc, and a lens holder which supports the objective lens. The lens holder has a circular opening and a lens holding surface provided on a periphery of the circular opening. One of either the objective lens or the lens holding surface of the lens holder has a symmetrical tapered surface which is adapted to come into contact with the other of either the lens holding surface or objective lens, respectively.

Abstract: The present invention is a mount for optical instruments, and particularly, for a Berek compensator having a birefringent crystal, which can be both tiled and rotated by structure of adjustment rings which are concentric to the optical path of the device.

Abstract: An optical head for optically writing data onto a recording medium and reading the data from the recording medium. The optical head includes an optical lens holder; a driver for the holder which is located on a side of the holder; flat spring members for elastically supporting the holder in a horizontal direction; and other flat spring members for elastically supporting the holder in a vertical direction, and for creating a sandwiched area. At least a part of the spring members for supporting the holder in a horizontal direction is located within the sandwiched area of the other spring members.

Abstract: Lenses (30', 32') are orthogonally tilted with respect to one another in a telescope to provide imaging for an amplifier-phase conjugate mirror (PCM)(10) in a laser oscillator/amplifier (12). This mutually orthogonal tilting avoids the problem of air breakdown which occurs when the laser energy is otherwise focused at a single point and thus avoids the need to use a vacuum cell to suppress the sparking at the telescope's focus. An adjustment of the tilting of one lens (32') with respect to the other lens (30') also avoids astigmatism.

Abstract: A movable lens barrel contains a front lens group and a rear lens group and moves along the optical axis during zooming. The front lens group moves together with the movable lens barrel during zooming, and moves relative to the movable lens barrel along the optical axis during focussing. The rear lens group moves within and relative to the movable lens barrel during zooming. A deviation of the focussing position takes place due to backlash of the drive mechanism of the movable lens barrel. This focussing position deviation is eliminated by changing the position of the front lens group as set for focussing, or by changing the position of the rear lens group as set for zooming, respectively in accordance with the zooming direction. In order to determine the set position of the front lens group, two tables are provided corresponding respectively to the zooming direction.

Abstract: A lens unit having a hollow holder and a lens member coupled in the hollow holder in which the lens member has an outer surrounding wall portion integrally formed with the lens member, the outer surrounding wall portion extending along an axis of the lens member, and an outer surface of the outer surrounding wall portion being coupled with an inner wall surface of the hollow holder, whereby the lens member can be prevented from falling or rolling when it is installed in the hollow holder.

Abstract: An adjusting mechanism for a lens comprises a mount, a sphere, a pressing ring, a positioning housing, a fixing ring, a lens, and an adjusting ring. Three protruding members are provided radially and horizontally around the circumference of the sphere. The sphere is stably disposed on the mount in an opening having a spherical surface provided on the center of the mount by three tension springs each secured between the protruding members and the mount. The inside of the sphere forms cylindrical space to accommodate the lens. The lens only axially moves with respect to the sphere by turning an adjusting ring screwed onto the sphere. The positioning housing is fixed on the mount around the sphere and the fixing ring is fastened on the top of the positioning housing.

Abstract: A positioner for accurately and precisely positioning an optical member such as a lens aligned with the tip of an optical fiber in relation to an optical device such as a beam launcher/splitter; the positioner includes a tilt base mounted in a frame and angularly displaceable about orthagonal X and Y axes defined by three ball bearings all engaging one surface of the tilt base and all biased against the tilt base. Two differential screws mounted on the frame engage two of the ball bearings to effect angular yaw and pitch adjustments. The tilt base is connected to a retainer support in turn connected to a retainer member; two additional differential screws engage the support through further ball bearings to effect linear movements of the retainer member along the X and Y axes.

Abstract: An actuator rotatable about a support shaft rectilinearly movable along axis of a shaft and rotatably movable about the shaft includes a cylindrical magnet extending about the shaft. The cylindrical magnet has a plurality of poles in the radial direction and magnetized boundaries between poles of opposite polarity extending in a circumferential direction of the magnet and extending in an axial direction of the magnet. A plurality of yokes are provided to define magnetic poles coupled in facing relationship with the magnetic boundaries of a cylindrical magnet and having coils coupled thereto to define the magnetic poles.