Abstract: A progressive power lens whose distance viewing vertex power is a negative value and in which a surface refractive power Pf.sub.m in the main meridional plane in a distance viewing portion is larger than a surface refractive power Pf.sub.s in a plane perpendicular to the main meridional plane (Pf.sub.m >Pf.sub.s). A surface refractive power Pn.sub.m in a section in the main meridional plane in a near viewing portion is smaller than the surface refractive power Pn.sub.s in a plane perpendicular to the main meridional plane (Pn.sub.m <Pn.sub.s).

Abstract: The present invention provides methods and apparatuses to evaluate the best image plane position for an optical lens system, particularly a wide angle lens with a large power ratio, in e.g. an endoscope, in simple and less time consuming procedure. The present devices and methods include a screen which can form an edge image, an optical system which forms an image of the screen, a light receiver located at the focal plane, or in its neighborhood, on which the edge image of the screen is formed by the optical system to convert the edge image into an electric signal, and a sampler which samples the electric signal transmitted from the light receiver in a crossing direction perpendicular to the edge image.

Abstract: In an aspherical spectacle lens having a negative degree and an aspherical surface of rotational symmetry located on an object side, a surface power of the aspherical surface of rotational symmetry at a center portion located on an axis of rotational symmetry is substantially 0 diopter, and the aspherical surface of rotational symmetry is of an apparent convex shape.

Abstract: An image projecting device includes structure for correcting the distortion of an image and/or the defocusing of an image, which will be caused in a situation in which the optical axis of a projection lens is inclined with respect to a screen. The device includes a screen positioned along a predetermined plane, a source for emitting light which forms an optical image on the screen, with the optical axis of the source and the screen plane being inclined with respect to each other so that they are not optically normal with respect to each other, and a reflecting surface for reflecting light from the source towards the screen along a separate optical axis. The reflecting surface is optically positioned between the screen and the source and has a predetermined three-dimensional shape which is adapted to correct for trapezoidal distortion of the optical image projected onto the screen.

Abstract: A method of forming a microstructure array suitable for use in the production of a focusing screen used in a finder system of a camera. The focusing screen includes an optical material in plate form having on one surface of a plurality small lens portions that project in a regular array of equilateral triangles from the optical material and each of the which has concentric contour lines, with a central apex. A flat portion is formed between adjacent small lens portions and a constricted portion is formed in the middle portion of the inclined surface of each small lens portion, with an irregular pattern of finer asperities is formed on the surfaces of the small lens portions and the flat portion. The high and low spots can be reversed.

Abstract: A focusing screen for use in the finder system of a camera such as a single-lens reflex camera, and a method of forming a microstructure array suitable for use in the production of such a focusing screen. The focusing screen includes an optical material in plate form having on one surface a plurality of small lens portions that project in a regular array of equilateral triangles from the optical material and each of which has concentric contour lines, with a central apex. A flat portion is formed between adjacent small lens portions and a constricted portion is formed in the middle portion of the inclined surface of each small lens portion, with an irregular pattern of finer asperities is formed on the surfaces of the small lens portions and the flat portion. The high and low spots can be reversed.

Abstract: A progressive multi-focal ophthalmic lens having a front refracting surface and a rear refracting surface one of which is a progressive surface whose refractive power changes continuously with the other being a non-progressive surface. The progressive surface is formed as a Fresnel lens surface composed of microscopic steps so that the macroscopic shape of the progressive surface generally conforms to that of the non-progressive surface.

Abstract: A lens meter having a focusing indication system with divided-image registration focusing comprises a condenser lens, a target having a nondiffusing transmissive surface and a slit pattern thereon, an objective lens, a lens mount for supporting a lens to be examined, a projection lens, a screen, the arrangement being such that the distance of movement in unison of the condenser lens and the target in the direction of an optical axis is read to detect the degree of the lens supported on the lens mount, an aperture plate disposed in the vicinity of a front focal point of the condenser lens and movable with the condenser lens and the target in the direction of the optical axis, and at least two deflection prisms disposed in intimate contact with the slit pattern on the target and having bases extending across the slit pattern and substantially perpendicularly to each other.

Abstract: An aspherical lens for an indirect ophthalmoscope, comprising a single biconvex lens having a first surface with a radius of curvature r.sub.1, and a second aspherical surface facing the examiner and having a paraxial radius of curvature r.sub.2. The lens being constructed to meet the following requirements: ##EQU1## where D is the effective diameter of the lens, y is the displacement in the direction of an optical axis of an aspherical shape as expressed by a rectangular coordinate system having the origin at the vertex of the second surface and normalized by r.sub.2, and x is the displacement in a direction normal to the optical axis and also normalized by r.sub.2 .