Abstract: A fundus camera capable of guiding accurately a sight line using an internal fixation target light source while an apparatus constitution is simplified. The fundus camera is provided with an illumination optical system for illuminating the fundus with visible illumination light for photographing and with invisible illumination light for observation, a photographing optical system for picking up an image of the fundus with visible reflection light from the fundus including a first image-pickup element, an observation optical system for picking up the image of the fundus with invisible reflection light from the fundus including a wavelength-selecting mirror and a second image-pickup element, a fixation target projection optical system for fixating an eye including alight-dividing member and a fixation target light source, and a wavelength-selecting filter. In the fundus camera, the visible fixation target light is guided to the eye and photo-received on the second image-pickup element.

Abstract: An image reading apparatus for reading a projected image by a line sensor formed in a linear shape. An image reading apparatus has an illumination system, an original supporting member, a projection lens and a line sensor formed in a linear shape. The illumination system includes a light guide formed of a cylindrically shaped light-transmitting material, a light source for introducing light into the light guide from the lengthwise direction of the light guide, a light-diffusing portion formed on the circumference of the light guide in the lengthwise direction of the light guide and a slit portion positioned opposite the light-diffusing portion.

Abstract: The present invention is a variable magnification lens system with a constant object-image distance. The lens system comprises an aperture stop, two fixed lens units constructed symmetrically with each other and two movable lens units constructed symmetrically with each other and located between the two fixed lens units, wherein the two lens units are positioned symmetrically with each other with respect to the aperture stop at the time of equal magnification, while the two lens units are positioned asymmetrically with each other with respect to the aperture stop during other magnification ratios.

Abstract: There is disclosed a lens system for projecting images of microfilm onto a screen or the like. The lens system is characterized by five lens components, that is, a first positive meniscus lens component convex to the magnification side, a second negative meniscus lens component concave to the magnification side, a third biconvex lens component, a fourth biconcave lens component having a powerful concave surface faced to the magnification side, and a fifth biconvex lens component.

Abstract: A modified Gauss type lens system of 5-group, 6-element is disclosed, which lens system comprises first to third and fifth groups each consisting of a single lens element and a fourth group consisting of a doublet and fulfills the following conditions:2.8f<f.sub.1,2,3 <10f0.25<(d.sub.1 +d.sub.2 +d.sub.3 +d.sub.4 +d.sub.5)/.SIGMA.d<0.35(N.sub.1 +N.sub.2 +N.sub.5 +N.sub.6)/4>1.721.0<r.sub.6 /.vertline.r.sub.7 .vertline.<1.50.2f<.vertline.r.sub.7 .vertline.<0.35fN.sub.1, N.sub.2 >1.7130<.nu..sub.1, .nu..sub.2, .nu..sub.5, .nu..sub.6 <5628 <.nu..sub.3, .nu..sub.

Abstract: A four element lens system for use on a camera and the like comprises two positive meniscus lens having two negative meniscus lens interposed between the positive lens. The optical axis of each lens elements being aligned with an aperture stopper element or its functional equivalent between the negative lens elements. The position of the effective plane of the aperture stopper satisfying the following equation: ##EQU1## wherein S is a distance along the optical axis between lens elements, S'.sub.2, is the distance between the surface of the second negative meniscus lens and the effective plane of the aperture stopper and S".sub.2 is the distance between the effective plane of the aperture stopper and the surface of the third negative meniscus lens. Preferably each of the lens elements is injection molded from a plastic material with both of the positive lens elements and the negative lens elements being identical lens.