Abstract: An imaging optical system includes a liquid crystal lens including a first body formed of a substantially transparent birefringent liquid crystal member, a second body formed of a substantially transparent birefringent liquid crystal member, and two pairs of electrodes for adding an electric field or a magnetic field onto the first body and the second body. A rear face of the first body is aligned perpendicular to a front face of the second body, the first body and the second body have substantially symmetrical shape against a plane perpendicular to an optical axis and a plurality of optical elements are arranged front and after the liquid crystal lens. The liquid crystal lens has two distinct focal points. The system automatically switches between these focal points, based on the position of the lens with respect to the object being observed.

Abstract: An imaging optical system is disclosed. The system comprises a liquid crystal lens including a first body consisting of a substantially transparent birefringent liquid crystal member, a second body consisting of a substantially transparent birefringent liquid crystal member, and two pairs of electrodes for adding an electric field or a magnetic field onto the first body and the second body. A rear face of the first body is aligned perpendicular to a front face of the second body, the first body and the second body have substantially symmetrical shape against a plane perpendicular to an optical axis and plurality of optical elements are arranged front and after the liquid crystal lens.

Abstract: An illumination optical system has a diffusion member including a number of nearly spherical members which are diminutive in size and transparent and a transparent medium whose refractive index is higher than that of air and different from that of the nearly spherical members and which holds the nearly spherical members, on the exit end face of a light conducting device for introducing illumination light. In this way, a visual field can be efficiently illuminated.

Abstract: An image fiber includes plural kinds of cores and a common cladding containing the cores, which are arrayed so that no similar cores are adjacent one another. A method of making the image fiber is that a plurality of optical fiber elements having cores of different diameters are arranged so that no similar cores are adjacent one another, and after being inserted in a jacket pipe, are heated at a high temperature to fuse the cladding portions of the optical fiber elements so that the whole is drawn down to a desired thickness.

Abstract: An endoscope system including a first hard endoscope which uses a relay lens as an image transmission optical system, a second hard endoscope which uses an image guide formed by a fiber bundle, and a TV camera which is mountable respectively on the first and second hard endoscopes and which is rotatable. The TV camera has built therein a CCD. An optical low-pass filter for removing moire even in case of being rotated is provided on an ocular part of the second hard endoscope.

Abstract: An image transmitting optical system comprising at least two bar-shaped lens components and constructed to have a numerical aperture enlarged by reserving an adequate space between an image of object to be transmitted and one of surfaces of the bar-shaped lens component which is located closest to the image of the object. In this image transmitting optical system, spherical aberration and curvature of coma are corrected by designing each of the bar-shaped lens components as a cemented lens component consisting of two bar-shaped lens elements.

Abstract: An image fiber is provided with an image transmitting portion including a plurality of cores and a cladding surrounding the cores; a jacket layer higher in refractive index than the cladding, covering the periphery of the image transmitting portion; and a coating layer higher in refractive index than the cladding, covering the periphery of the jacket layer. The image fiber, integrally constructed in this way, allows light propagating through the cladding to be effectively eliminated, and thus fails to produce flare.

Abstract: An optical low pass filter consisting of a diffractive optical element consisting of a plurality of regions which have different imaging characteristics and are joined adjacent to one another so that the imaging characteristics are varied discontinuously. This optical low pass filter is to be used for optical instruments using solid-state image pickup devices and so on.

Abstract: An image fiber has a plurality of optical fibers with normalized frequencies different from one another, which is constructed so that a plurality of cores different in size and shape from one another are distributed at random in a cladding. The optical fibers include at least two kinds of optical fibers having propagation modes different in number. Thus, the image fiber is capable of suppressing cross talk to prevent the degradation of image quality.

Abstract: An electronic image pickup apparatus comprising an imaging optical system for forming images of an object and image pickup device having light receiving surface configured so as to sample the images at discontinuously distributed points. This image pickup apparatus functions to sample the images of the object formed by the imaging optical system while receiving the images on the light receiving surface of the image pickup device and output signals representing light intensities on the object side. Disposed in the imaging optical system is a refracting surface which produces the optical low pass effect and has a shape capable of exhibiting an effect to eliminate moire, for example, due to a fact that it includes a point on which differential coefficients of a function expressing a shape of the refracting surface are discontinuous.

Abstract: An observation system for an endoscope has an entrance end face upon which an image is incident and an exit end face from which the image exits. The system comprises an image guide fiber of a very small diameter to allow transmission of the image, an object optical system arranged in front of the entrance end face of the image guide fiber, and a reproduction optical system arranged on the back side of the exit end face of the image guide fiber. The reproduction optical system is comprised of an eyepiece optical system and relay lens system. The maximal exit numerical aperture of the object optical system is greater than the maximal entrance numerical aperture of the reproduction optical system.

Abstract: A TV system for endoscopes is configured to connect to a fiber scope using an image guide fiber bundle and a rigid endoscope using a relay lens system. An image is formed by either the fiber scope or the rigid endoscope on a TV monitor. The camera control unit controls a level of the color difference signal in accordance with spatial frequency components contained in the TV signal. A variable switching unit is provided which allows the electrical circuits of the camera control unit to function selectively in accordance with the characteristics of the image transmission system.

Abstract: An image transmission optical system wherein a lens unit serving for relaying an image for a unit relaying distance consists of two bar shaped cemented lens components, and each of said lens components consists of a bar-shaped lens element and two lens elements which are cemented to both the end surfaces of the bar-shaped lens element respectively of said bar-shaped lens element and have a refractive index higher than that of the bar-shaped lens element. This image transmission optical system comprises a small number of air-contact surfaces and has favorably corrected aberrations.

Abstract: An image transmission optical system wherein a lens unit serving for relaying an image for a unit relaying distance consists of two bar-shaped cemented lens components, and each of said lens components consists of a bar-shaped lens element and two lens elements which are cemented to both the end surfaces of said bar-shaped lens element respectively of said bar-shaped lens element and have a refractive index higher than that of said bar-shaped lens element. This image transmission optical system comprises a small number of air-contact surfaces and has favorably corrected aberrations.

Abstract: An illumination optical system consisting of a small number of lens components and having a very uniform light distribution characteristic wherein a light source having a two-dimensional extent, a positive lens system so arranged as to locate the front focal point thereof in the vicinity of the light source and having at least one aspherical surface, and a surface to be illuminated are arranged.

Abstract: A method for cooling high temperature reduced iron produced by a direct reduction process in a cooling zone integrated with a direct reduction furnace, such as a shaft furnace, which method utilizes the exhaust gas of the reducing furnace as the cooling gas with great operational and economical advantages.