Abstract: A tape guide arrangement for a tape recording and reproducing apparatus comprises a cylinder device provided with a rotary head, a first slant guide member for feeding a tape to the cylinder device, a second slant guide member for guiding the tape from the cylinder device into a predetermined direction, a first rotary guide member for guiding the tape to the first slant guide member, and a second rotary guide member for causing the tape from the second slant guide member to pass through a predetermined position. Each of the first and second rotary guide members is provided with an axis of rotation substantially perpendicular to an imaginary plane defined in relation to positions which are set on the first and second slant guide members and the cylinder device, respectively, and through which an elongated edge of the tape passes.

Abstract: An encoder for measuring devices having a code plate including binary grating patterns arranged in a given regular fashion and forming a first scale, a linear sensor including photodiode elements arranged with fixed intervals and forming a second scale disposed in parallel with the code plate, and processor means for absolute-interpolating one pitch of the first or second scale on the basis of reading data or information obtained from the linear sensor corresponding to a relative position of the patterns to the elements.When the number of the scale divisions of the first scale within a fixed range is N, the number of the scale divisions of the second scale is N+1. Accordingly, when the first scale is a main scale, the second scale is a vernier scale. The processor means detects a phase inverting point corresponding to the interpolation point on the basis of the reading data. The processor means performs the absolute interpolation by detecting the phase inverting point.

Abstract: A crosslinked foam having an expansion ratio of 25 to 60 which comprises a composition containing 100 parts by weight of a resin component consisting of an ethylenevinyl acetate copolymer or a mixture thereof with a thermoplastic resin and 50 to 500 parts by weight of an inorganic powder material.

Abstract: A focus detecting device for an eye fundus camera including a target having a target pattern comprised of a first slit and a second and third slits disposed in parallel with and at the opposite sides of the first slit. The second and third slits are symmetrical to each other with respect to the first slit. Deflecting prisms are provided to deflect the luminous flux through the first slit in one direction perpendicular to the longitudinal axis of the first slit and the luminous fluxes through the second and third slits in the opposite direction. The slit pattern is convenient for automatic focus adjustment.

Abstract: A brushless DC motor includes a permanent field magnet secured to a rotor and having a radially directed annular surface, and two phase coil elements in the form of a sectorial loop secured to a stationary stator and disposed in a plane parallel to the annular magnet surface, the loop having circumferentially extending portions which are in inner and outer relation in respect to the center of the annular magnet surface, with the magnet and each coil element being relatively rotatable about the axis of the rotor. The mean radial distance f between the inner and outer circumferentially extending portions of each coil element and the radial width b of the annular surface of the magnet are selected as that the ratio b/f is within the range of 0.8 to 1.2 for maximizing the viscosity factor .mu. of the motor. In addition to providing the above ratio within the stated range or as an alternative thereto, the mechanical viscosity factor .mu. can be maximized by providing a reduced air gap d'=.sqroot.2d/.sqroot.

Abstract: In a toughened lens which has been subjected to chemical tempering process and then to edge grinding, the fracture strength can be greatly enhanced if the peripheral portion is chamfered with the angle of chamfering to the tangential line on the optical surface of the lens not greater than 45.degree.. This toughened effect is further increased by subjecting the chamfered peripheral portion to such a post treatment as mechanical polishing, chemical etching or thermal polishing.