Abstract: In a motor-driven power steering apparatus, a plurality of rotational position detecting sensors are provided in an electric motor, and during an abnormality in any one rotational sensor, the electric motor can be driven by using a detected result of any other one rotational position detecting sensor.

Abstract: In an electric power steering apparatus, an O-ring is interposed between a middle portion in an axial direction of a first faucet portion provided in a gear housing and a middle portion in an axial direction of a second faucet portion provided in a motor case when fitting the second faucet portion to the first faucet portion.

Abstract: An external optical system is simplified in construction so that a laser oscillation apparatus is low-priced and compact as a whole. On the side of one end portion (10A) of a return-type resonator (10), a laser beam is reflected by a polarizing mirror (147) to be incident upon a polarizing mirror (146) which is situated diagonally below the mirror (147), and is also reflected by a polarizing mirror (142) to be incident upon a polarizing mirror (141) which is situated diagonally above the mirror (142). Thus, at the one end portion (10A), the polarizing mirror (141) and the like are arranged so that optical axes cross each other. Since the emitted laser beam forms a linear polarized beam inclined at an angle of 45.degree. to a horizontal plane, as indicated by arrow (100), the laser beam can be subjected to circular polarization by using only one 1/4-wavelength mirror. Thus, the construction of the external optical system can be simplified.

Abstract: A laser oscillator which is capable of providing a circularly polarized laser beam by an external optical system having a brief configuration. A folding section of a folded-type resonator (10) comprises reflecting mirrors (4a), (4b) and (4c). The reflecting mirror (4a) is inclined at an angle of 45.degree. to an optical axis of an excitation section (3a), and the reflecting mirror (4c) is inclined at an angle of 45.degree. to an optical axis of an excitation section (3b). The reflecting mirror (4b) is horizontally arranged so that the center of the mirror is positioned at the vertex of an isosceles right triangle with respect to the reflecting mirrors (4a) and (4c). Thus, an S polarized-light component of a laser beam from the excitation section (3b) is reflected by the reflecting mirror (4c) toward the reflecting mirror (4b).