Abstract: An eyepiece lens comprising a single gradient-index lens having a positive refracting power, or comprising a radial gradient-index lens having a positive refracting power, and a field lens, wherein the following Eqs. are satisfied:1<.PHI..sub.m /.PHI.<1.5 (1).vertline..PHI..sub.S1 /<-.PHI..sub.S2 (2)-0.01<1/V.sub.1 <0.025 (3)where .PHI. is the refracting power of the radial gradient-index lens, .PHI..sub.m is the refracting power of a medium of the radial gradient-index lens, .PHI..sub.S1 is the refractive power of a surface located on the eye side of the radial gradient-index lens, .PHI..sub.S2 is the refracting power of a surface located on the object side of the radial gradient-index lens, and V.sub.1 is a coefficient of color dispersion of the medium of the radial gradient-index lens.

Abstract: An achromatic lens system which comprises a radial type gradient index lens which has a refractive index varying in a direction perpendicular to an optical axis and a diffraction type lens, and sufficiently corrects the secondary spectrum with a small number of optical elements.

Abstract: A gradient index lens component composed of a single radial type gradient index lens element which has planar surfaces on both side and a positive refractive power and comprising an aperture stop which is disposed in the vicinity of an object side surface of the radial gradient index lens element for restricting a light bundle. And an image pickup apparatus composed by integrating the gradient index lens component with an image pickup device.

Abstract: The delay of fuel flow in an intake passage of an engine is divided into two categories, namely a short-term delay having a relatively fast time constant and a long-term delay having a relatively slow time constant. The corrections for each delay are stored separately depending on the engine running conditions. A mechanism is provided for estimating the particle diameter of the fuel spray, and either the long-term delay correction is modified so that it increases or the short-term delay correction is modified so that it decreases as the particles of fuel spray become smaller. The basic fuel injection amount during transient engine running conditions is corrected by applying the delay flow correction thereby modified, and error in the air-fuel ratio during transient conditions due to atomization of fuel particles is prevented.

Abstract: A lens system comprising, in order from the object side, a first lens component having a positive refractive power, a second lens component having a negative refractive power and a thrid lens component having a positive refractive power; the first lens component or the third lens component being a radial type graded refractive index lens component. The lens system is composed of the lens component in a number as small as three and has favorable optical performance.

Abstract: A lens system comprising a radial type graded refractive index lens element and a diffraction type lens element so that the refractive power of the radial type graded refractive index lens element is imparted to the diffraction type lens element, thereby facilitating manufacturing of the graded refractive index lens element and favorably correcting aberrations including chromatic aberration.

Abstract: An attachment lens system comprising, in the order from the object side, a first lens unit having a positive refractive power and a second lens unit having a negative refractive power; having a negative refractive power as a whole; and adapted in such a manner that magnification thereof is changed by moving at least one of the first lens unit and the second lens unit along the optical axis so as to vary the airspace reserved between these lens units. This attachment lens system composes a lens system having a high vari-focal ratio when combined with a master lens system.

Abstract: A vari-focal lens system including, in the order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, an aperture stop, a third lens unit having a positive refractive power and a fourth lens unit having a negative refractive power; and using at least one radial GRIN lens element on each side of the aperture stop. This vari-focal lens system has only a very small number of lens elements and had favorably corrected aberrations.

Abstract: A vari-focal lens system comprising, in the order from the object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a positive refractive power and an aperture stop arranged on the image side of said third lens unit, using at least one radial GRIN lens, axial GRIN lens or aspherical surface, and having a high vari-focal ratio and a wide field angle at the wide position.

Abstract: A lens system comprising, at locations in the vicinity of each other, radial type graded refractive index lens elements made of a medium having a positive refractive power and other radial type graded refractive index lens elements made of a medium having a negative refractive power. This lens system has aberrations corrected favorably with the radial type graded refractive index lens elements which are made of materials easily preparable.

Abstract: A high performance, compact, light-weight zoom lens system manufacturable at a low cost consisting of a plural number of lens units and so adapted as to perform zooming by varying airspace(s) reserved between the lens units, said zoom lens system comprising, in the order from the object side, a first lens unit having negative refractive power, an aperture stop arranged on the image side of said first lens unit, and at least one radial GRIN lens component arranged on the image side of said aperture stop, having a concave shape and having positive power.

Abstract: A vari-focal lens system comprising a plurality of lens units including a lens unit arranged on the extremely image side and having a negative refractive power, and adapted so as to perform variation of focal length by moving the lens units, said negative lens unit being composed, in the order from the object side, of a front subunit consisting of at least one negative lens unit and a rear subunit consisting of at least one negative lens element.

Abstract: A vari-focal lens system comprising, in the order from the object side a movable front lens unit having negative refractive power and a movable rear lens unit having positive refractive power, said front lens unit consists of a negative lens component and a positive lens component or a single negative lens component, and said rear lens unit comprising at least one negative lens component. Said vari-focal lens system consists of a very small number of lens components, concretely specifically three or four lens components.

Abstract: A finder optical system for single reflex cameras is provided with a photographing lens, an optical path splitting device splitting a beam of light emanating from the photographing lens into two beams and directing one beam to a photographing system and directing the other to an observing system, and an electronic image pickup device disposed in the photographing system and having an image pickup surface for receiving an image formed by the light beam and a Porro prism for forming an orthographic image, and an eyepiece disposed in the observing system. Thus, the finder optical system for single reflex cameras can be provided which is simple in structure, small in size, and has a low manufacturing cost.

Abstract: A dome shaped ceramic insert which defines a portion of a swirl chamber is formed at the crown portion with a single aperture through which both the fuel injector and the glow plug can extend. The cylinder head is formed with a portion which fits into the aperture and which has a wall portion which cooperates with the inner walls of the insert to define the upper section of the swirl chamber.

Abstract: A system for shaking water off a surface includes an electromagnetically operable driver unit for driving a member having the surface. The driver unit is connected to a control unit which controls oscillation frequency to be generated by the driver unit. The control unit adjusts the frequency of oscillation transmitted to the member for matching the oscillation frequency with the resonating frequency of the member for effectively shaking the water off the surface.

Abstract: A range-finding optical system comprising a light emitting element, a light projecting lens located in front of the light emitting element and serving to project the light emitted from the light emitting element onto an object, a light receiving element, a light receiving lens located in front of the light receiving element and serving to converge the light, which is emitted from the light emitting element and reflected by the object, onto the light receiving element, a member for interconnecting the light projecting lens and light receiving lens and for defining the distance therebetween, and a member for interconnecting the light emitting element and light receiving element and for defining the distance therebetween, the range-finding optical system being arranged that the displacement of the focus point of the photographic lens system to be caused by temperature variation is easily compensated by means of the difference between the coefficient of thermal linear expansion of the member for interconnecting t

Abstract: A variable focal length lens system comprising a first lens unit which comprises a negative meniscus lens and a positive lens, a second lens unit which comprises a negative lens, and a third lens unit which comprises at least three lenses including at least one negative lens, the variable focal length lens system being arranged to vary the focal length by moving the second lens unit and arranged to have a large aperture ratio and high vari-focal ratio and to be small in size.