Abstract: An auto-focusing system includes a focus condition detector which detects focus condition based on the infrared light. A data producer is provided for producing a deflection signal indicating a difference between an image forming distance for the infrared light and that for the visible light, due to aberration. In accordance with the detected focus condition and deflection signal, an objective lens is shifted to a position for properly focusing an image of visible light on an image forming plane.

Abstract: In an interchangeable lens including an optical system adjustable for focusing and adapted to be detachably mounted on a camera body which is provided with focus detection means for detecting an amount of defocus of an object image formed by the optical system, and drive means for driving the optical system for the focus adjustment thereof in accordance with the detected amount of defocus. The interchangeable lens comprises, inter alia, a code plate for producing a plurality of digital photographic distance signals representing given discrete photographic distances of the optical system in accordance with the adjustment of the optical system for focusing.

Abstract: An automatic focusing device which compises a defocus amount detecting unit for detecting a defocus amount attributable to a first optical system of an interchangeable lens assembly and a second optical system of an AF convertor, a converting circuit for converting the defocus amount into a data corresponding to a focusing amount of the second optical system which varies in non-linear relationship to the defocus amount, and an optical drive unit for moving the second optical system on the basis of a data representative of the focusing amount supplied from the converting circuit.

Abstract: An improvement of an inverted telephoto type wide angle lens system having, from the object to the image side a front lens group of a negative refractive power which is left stationary upon focusing, and a rear lens group of a positive refractive power which is shiftable for the purpose of focusing is disclosed. The improvement is characterized in that the lens system fulfills the following condition:2.65<.vertline.f.sub.F .vertline./f.sub.R <7.5wherein f.sub.F represents the focal length of the front lens group, and f.sub.F represents the focal length of the rear lens group.

Abstract: An automatic focusing device which comprises a defocus amount detecting unit for detecting a defocus amount attributable to a first optical system of an interchangeable lens assembly and a second optical system of an AF convertor, a converting circuit for converting the defocus amount into a data corresponding to a focusing amount of the second optical system which varies in non-linear relationship to the defocus amount, and an optical drive unit for moving the second optical system on the basis of a data representative of the focusing amount supplied from the converting circuit.

Abstract: A telephoto lens system comprises, from the object side to the image side, a first positive lens unit, a second negative lens unit, and a third positive lens unit, the second lens unit alone being shiftable along the optical axis with the first and third lens units being stationary for focusing the whole lens system. The first lens unit consists of a first positive component, a second positive meniscus component convex to the object side, and a third negative component of a doublet composed of cementing together a positive meniscus lens convex to the object side and a negative meniscus lens convex to the object side, the cemented surface of the third component being convex to the object side. Another feature is characterized that the light pencils exited from the second lens unit are properly convergent.

Abstract: An auto-focusing system includes a focus condition detector which detects the focus condition based on infrared light. A data producer is provided for producing a deflection signal indicating the difference between an image forming distance for infrared light and that for visible light, due to aberration. In accordance with the detected focus condition and deflection signal, an objective lens is shifted to a position for properly focusing an image of visible light on an image forming plane.

Abstract: An active focus detecting device for use in a camera is provided and includes emitting light that is polarized, and collimated so that the light forms a light bundle which will pass near the optical axis of the objective lens, and then will be projected in a diverging light path after having been focused by the objective lens towards the object. A polarization component is provided for receiving the returning light and directing a component of that light towards a detector for determining a focusing condition.

Abstract: A method for injecting molten metal in a vertical diecasting machine. In order to efficiently produce high quality castings, a molten metal is injected into a mold cavity with the upper part of the mold cavity communicating with the atmosphere, the mold cavity is occluded before the completion of the injection, and then the molten metal is pressurized to suppress the trapping of air or gases in the casting.

Abstract: An inverted telephoto type wide angle lens system is provided. The lens system comprises an aperture stop, a first lens group located at the object side of the aperture stop, and a second lens group located at the image side of the aperture stop, the second lens group including at least two movable focusing lens groups, whereby the focusing is practiced by only the movement of the focusing lens groups with the remaining lens elements in the lens system stationary.

Abstract: An improved wide angle zoom lens system of an inverted telephoto type having a negative object side lens group and a positive image side lens group is provided, in which an air space to be varied in accordance with the shift of the object side lens group for focusing is located at the image side of a negative component in the object side lens group.

Abstract: The present invention is directed to an inverted telephoto type wide angle lens system having a field angle of 114 degrees and an aperture ratio of 1/2.8. The lens system comprises eleven lens groups and fourteen lens elements which fulfill the following conditons:1.0 f<.vertline.f.sub.F .vertline.<1.4 f4.5 f<R.sub.1 6.4 f1.2 f<R.sub.2 <1.7 f1.2 f<R.sub.3 <1.5 fwherein:f represents the focal length of the whole lens system;f.sub.F represents the focal length of the front lens group;R.sub.1 represents the radius of curvature of the image side surface of the front positive meniscus lens in the front lens group;R.sub.2 represents the radius of curvature of the image side surface of the first negative meniscus lens in the front lens group; andR.sub.3 represents the radius of curvature of the second negative meniscus lens in the front lens group.

Abstract: An inverted telephoto type wide angle lens system of an aperture ratio, 1/2.0 and a field angle, 84 degrees is provided. The lens system consists, from the object to the image side, of: a first component of a positive meniscus lens element convex to the object side; a second component of a negative meniscus lens element convex to the object side; a third component of a negative meniscus lens element convex to the object side; a fourth component of a biconvex lens element; an aperture stop; a fifth component of a positive meniscus lens element convex to the object side; a sixth component of a biconvex lens element; a seventh component of a biconcave lens element; an eighth component of a positive meniscus lens element convex to the image side; and a ninth component of overall positive refractive power including at least one lens element.

Abstract: The present invention is directed to a compact lens system equally operable in both air and water, comprising a first lens group having a front surface directly facing the air or water medium, the center of the curvature of the front surface being located approximately at the entrance pupil of the lens system, and a second lens group located at the image side of the first lens group with an air space formed between the first and second lens groups. The air space and design parameters being selected in the lens system so that the field curvature of the lens system is mainly changed without any substantial change in other aberrations when the air space is changed, wherein the air space is changeable by a predetermined value in response to the change between use in air and use under water for maintaining a relatively flat image surface.

Abstract: The present invention is directed to an inverted telephoto type wide angle lens system having eight lens groups and eight lens elements which fulfill the following conditions:______________________________________ 0.75f < .vertline.f.sub.1,2,3 .vertline. < 1.1f f.sub.1,2,3 < 0 0.89f < f.sub.1,2,3,4,5 < 2.3f 0.5 < d.sub.7 /d.sub.6 < 2.0 1.0 < d.sub.8 /d.sub.10 < 2.4 1.5 < d.sub.7 /d.sub.9 < 5.2 ______________________________________wherein f.sub.1,2,3 represents the total focal length of the first to third single lens elements; f.sub.1,2,3,4,5 represents the total focal length of the first to fifth single lens elements; f represents the focal length of the entire lens system, and d.sub.i represents the i-th axial distance numbered consecutively from the front of the lens system.

Abstract: The inverted telephoto type wide angle lens system of the present invention includes, from the object to image side, a first lens group having a positive single lens, a first negative meniscus single lens convex to the object side and a second negative meniscus single lens convex to the object side. A second lens group includes at least one positive lens while a third lens group includes, from the object to the image side, a first positive meniscus single lens convex to the image side, a biconcave single lens, a second positive single lens convex to the image side and a positive single lens. In addition, the inverted telephoto type wide angle lens system of the present invention fulfills the following conditions:______________________________________ 0.75f < .vertline.f.sub.1,2,3 .vertline. < 1.25f f.sub.1,2,3 < 0 10f< f.sub.1 < 20f 6.5f < .vertline.r.sub.2 .vertline. < 22f r.sub.2 < 0 1.3f < f.sub.5 < 1.9f ______________________________________wherein:f.sub.

Abstract: A variable soft focus lens system particularly adapted for photography is disclosed. The lens system incorporates two lens groups, a first object side lens group having an image side, rearmost surface convex to the image side, and a second, image side lens group having an object side, foremost surface concave to the object side. An airspace separating the first and second lens group has a meniscus shape concave to the object side. A good quality soft tone image having undersirable aberrations well within tolerable limits, is attained by shifting at least the second lens group along the optical axis relative to the first lens group whereby the airspace separating the two lens groups and a spherical aberration of the entire lens system is varied. An image does not lose proper focus while the spherical aberration of the system is varied. The second lens group has a refractive power within specified limits in relation to the refractive power of the entire lens system.

Abstract: A compact wide angle lens system for use in a camera having a range finder is provided. The lens system is of five-group, seven-element type comprising, consecutively from the object to the image side, a first lens group consisting of a negative meniscus single lens convex to the object side, a second lens group consisting of a positive doublet having a cementing surface concave to the object side, a third lens group consisting of a negative meniscus single lens concave to the object side, a fourth lens group consisting of a positive doublet, and a fifth lens group consisting of a negative meniscus single lens concave to the object side.

Abstract: A wide angle lens system of an inverted telephoto type is provided. The lens system comprises six separate lens groups comprising, consecutively from the object to the image side a negative meniscus lens element; a positive doublet; a positive meniscus lens element; a biconcave single lens element; a positive lens element and a rear positive lens element. One of the lens elements of the fifth and sixth groups is a single lens element while the other is a doublet. The lens is capable of providing an aperture ratio greater than F/2.0, a field angle of approximately 64 degrees and a back focal distance greater than the focal length of the system.

Abstract: An objective lens system, for example of a Gauss or Tessar type is provided having the capability of adequately correcting aberrations even when the lens system is focussed at a relatively close object. The lens system is adaptable for use in cameras and comprises a first lens group including an aperture stop and a second lens group positioned on the image side of the first lens group. The second lens group includes a first lens sub-group of positive refracting power and a second lens sub-group of negative refractive power. The air spaces provided between the first lens group and the first lens sub-group and also between the first lens sub-group and the second lens sub-group are varied to compensate for changes in aberrations resulting from focussing at a relatively close object. More specifically, the first air space is increased while the second air space is decreased when the object distance of the lens system is decreased.