Abstract: An interchangeable lens includes an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject; a lens data storage unit which stores data indicating a correspondence between a value of the focal distance and a value of the size of the image circle; and a lens interface unit which sends data indicating the correspondence to the imaging apparatus.

Abstract: An interchangeable lens includes an optical system which is variable in focal distance and in which a size of an image circle varies by the focal distance, the image circle being an effective image formation region of an optical image of a subject; a lens data storage unit which stores data indicating a correspondence between a value of the focal distance and a value of the size of the image circle; and a lens interface unit which sends data indicating the correspondence to the imaging apparatus.

Abstract: A lamp apparatus comprises a lamp body, a base mounted to the lamp body, the base including a top end of base connected with a first conductor electrically and a threaded portion connected with a second conductor electrically, the top end of base and the first conductor welded through the process of mutual fusion, and a welded portion formed in a convex shape with the mixture of materials of the top end of base and the first conductor.

Abstract: A lamp apparatus comprises a lamp body, a base mounted to the lamp body, the base including a top end of base connected with a first conductor electrically and a threaded portion connected with a second conductor electrically, the top end of base and the first conductor welded through the process of mutual fusion, and a welded portion formed in a convex shape with the mixture of materials of the top end of base and the first conductor.

Abstract: A lamp apparatus comprises a lamp body, a base mounted to the lamp body, the base including a top end of base connected with a first conductor electrically and a threaded portion connected with a second conductor electrically, the top end of base and the first conductor welded through the process of mutual fusion, and a welded portion formed in a convex shape with the mixture of materials of the top end of base and the first conductor.

Abstract: An optical information reproducing device for reading informations recorded on the opto-magnetic recording medium is disclosed. The device comprises a first beam splitter for separating an inward path from an outward path of the light and a second beam splitter having a plane-parallel plate for separating the separated return light into two light fluxes including light flux with at least astigmatism, the first beam splitter having transmittivity and reflectance factor for the polarization component in the direction perpendicular to the linear polarization direction of the incident light being about 100%, the photodetector for receiving light flux with astigmatism separated from the second beam splitter being arranged in such a manner that the major axis of the ellipsoidal spot formed on the photodetector due to astigmatism becomes the push-pull signal direction.

Abstract: An optical head has a stationary optical system and a movable optical system. The stationary optical system includes a semiconductor laser located in a holding member with an opening, and a beam splitter for guiding light emitted from the light source, to the outside of the holding member through the opening. The sheet member contacts both the beam splitter and that portion of the holding member which surrounds the opening thereof, thereby sealing the opening. Further, the holding member is movably secured to the frame of the movable optical system.

Abstract: In an optical data recording/reproducing apparatus for performing write and read operations of data by irradiating laser light onto an optical data recording medium, in order to reduce noise of a semiconductor laser, an HF oscillator is provided to superpose an HF current on a drive current to be applied to the semiconductor laser. The HF oscillator is housed in a conductive shield case together with the semiconductor laser. An LC low-pass filter is also provided in a signal line connecting the components inside and outside the shield case to prevent undesired radiation of the HF current. A write drive line and a read drive line of the semiconductor laser are separated in the shield case, and the write drive line is disconnected from the HF oscillator in at least a read mode.

Abstract: An apparatus for optically reading information out of an opto-magnetic disk including a semiconductor laser emitting a polarized laser light beam which is made incident upon the opto-magnetic disk via beam splitter, reflection surface and objective lens. The light beam reflected by the opto-magnetic disk is made incident upon a photodetector by the objective lens and beam splitter. In order to compensate for the phase difference of P polarized and S polarized light components of the light beam reflected by the opto-magnetic disk within a wavelength over which the wavelength of the light beam might fluctuate due to the temperature variation, multi film constructions are provided in the beam splitter and reflection surface, the multi film constructions having such characteristics that the wavelength dependencies of the phase difference of the beam splitter and reflection surface can be made substantially a constant value such as zero and 90 degrees.