Abstract: A variable power finder having an objective lens of positive refracting power comprising a first lens unit of positive refracting power movable along an optical axis and a second lens unit releasably attached to the first lens unit in axial alignment, wherein a real image to be observed is formed by the objective lens.

Abstract: In the disclosed zoom lens, a positive front lens unit and a negative rear lens unit are moved forwardly axially in differential relation to vary the overall focal length from a minimum to a maximum value, while a positive middle lens unit is kept stationary during the variation of the focal length. A diaphragm determining the F-number is positioned at a fixed point between the front and rear lens units.

Abstract: In the disclosed finder, an auxiliary lens for changing the magnification power is inserted into the space between an objective lens and an eyepiece. The size of the viewfield frame is simultaneously changed to maintain a constant percentage of the viewfield of the finder. The required rate of change of magnification power that the auxiliary lens must attain to leave the size of the viewfield frame of the finder unchanged can be reduced with the advantage of minimizing the bulk and size of the finder.

Abstract: A flash device for a camera having a light emitting window of rectangular shape oriented so that the long side of the window is nearly perpendicular to a long side of the film format in the camera. An optical panel in the light emitting window is constructed in such a way as to satisfy the following conditions:0.5<f1/f<1.5f2/f<0.5,where f1 is the focal length of an end portion of the longitudinal length of the optical panel, f2 is the focal length of a central portion of the optical panel, and f is the focal length of a photographic lens of the camera.

Abstract: In the disclosed beam splitter, a first prism has an entrance face, an inclined face, and a mirrored face for totally reflecting a beam reflected from the inclined face back to the inclined face. A second prism has an entrance face in parallel with the inclined face of the first prism, and two exit faces. One of the exit faces of the second prism cooperates with the mirrored face of the first prism. When the first and second prisms are turned as a unit, the inclined face of the first prism either passes a light beam arriving from the entrance face through to the second prism and out one of the exit faces or totally reflects the arriving light beam to the mirrored face. The light beam reflected back from the mirrored face now passes through the inclined face to the second prism and out the cooperating exit face of the second prism.

Abstract: The disclosed compact photographic lens includes, from front to rear, a positive meniscus-shaped first lens unit convex toward the front, a negative aspheric second lens unit concave toward the front, a bi-concave third lens unit, and a negative fourth lens unit with its front surface concave toward the front. The lens satisfies the following conditions:-3.5<r3/f<-2.0-1.8<r7/f<-0.51.4<r8/f<6.50<d6/f<0.017where f is the focal length of the entire system, r3 is the paraxial radius of curvature of the front surface of the third lens unit, r7 and r8 are the radii of curvature of the front and rear surfaces of the fourth lens unit respectively, and d6 is the axial air separation between the third and fourth lens units when focused to infinity.

Abstract: An objective lens comprising a front lens unit and a rear lens unit with the separation between the two lens units being varied to vary the focal length of the entire system, wherein the front lens unit has a positive refractive power and consists of a positive lens of strong convex curvature toward the front, a negative doublet lens of a negative lens and a positive lens cemented together in this order from the front, and a positive lens sub-unit, and the rear lens unit has a negative refractive power and comprises a positive lens and a negative lens. Particularly the double lens is so designed that the comatic aberration in the intermediate zone of the image frame is stabilized throughout the entire range of variation of the focal length, and the halo in the intermediate zone in the telephoto end is well corrected.

Abstract: The disclosed zoom lens is constructed with a front lens group including, from front to rear, a positive lens unit, a negative lens unit and a positive lens unit having a positive overall refractive power. A rear lens group having a negative overall refractive power arranged on the image side of the front lens group moves axially along with the front lens group in differential relation. The rear lens group is constructed with a negative front lens having a glass relatively large Abbe number and a positive rear lens having a glass of relatively small Abbe number to achieve good stability of chromatic aberration correction against zooming.

Abstract: A compact zoom lens is constructed with, from front to rear, first, second and third lens units of positive, negative and positive refractive powers, respectively. A diaphragm is positioned in or adjacent the second lens unit. The second lens unit and the diaphragm are stationary. When zooming from the wide angle end to the telephoto end, the first and third lens units are axially moved in such a manner that each of the separations between the first and second lens units and between the second and third lens units is increased monotonically.

Abstract: A conversion lens upon attachment on the image side of a master lens increases the focal length of the entire system. The conversion lens comprises three components of negative, positive and negative powers in this order from the front, has a negative power as a whole, and satisfies the following conditions:2.0<f1/f3<4.00.8<.vertline.f2/f3.vertline.<1.2n1-n2>0.15where fi and ni are the focal length and the refractive index of the glass of the i-th component counting from the front respectively.

Abstract: A conversion type varifocal lens system comprising a master lens which has a front assembly of positive power and a rear assembly of negative power, and a supplementary lens upon insertion into, or removal from, the space between the front and rear assemblies to change the focal length of the entire system.

Abstract: The disclosed finder system includes, from front to rear, a first objective lens of negative power, an optical member having a half-mirror, an eyepiece of positive power and a viewfinder frame arranged near the eyepiece to be observed by the eyepiece with the aid of a reflection from the half-mirror. The finder system satisfies the condition 0.2<d/D<0.6 where D is the air separation between the first objective lens and the eyepiece lens and d is the air separation between the optical member and the eyepiece lens. Thus the first objective lens is exchangeable for a second objective lens of different power from that of the first objective lens to change the magnification of the finder system.

Abstract: An Albada finder is constructed of an objective lens, a reflection layer, a field-of-view defining frame, and an eyepiece arranged in sequence to provide a mirror image of the frame from the reflection layer to the eyepiece. An optical device of positive power is arranged outside an optical path of the finder. An information source with an information display plate and an illuminator for illuminating the display plate are arranged so that light from the display plate comes through the optical device into the eyepiece as an oblique beam. This shortens the distance from the reflection layer to the eyepiece while achieving a sharp information display.

Abstract: The disclosed triplet type objective includes from front to rear, a first lens of positive power, a second lens of negative power and a third lens of positive power followed by a diaphragm, with at least one of the refracting surfaces of the second and third lenses being aspheric. To shape this aspheric surface with reference to a spherical surface for determining the focal length of the lens, numerical ranges are given for the axial distances between the aspheric and spherical surfaces at a maximum value and its half value for aspherical effectiveness from the optical axis. Satisfying these specified ranges makes it possible to correct all aberrations well, improve the compactness, and increase in the image angle.

Abstract: On a forward portion or a rearward portion of an interchangeable lens removably mountable to a photographing device such as a camera or the like, a lens barrel is provided so as to be removably mountable to the interchangeable lens and the movement of a movable lens in the lens barrel is controlled by the output signal of an automatic focusing device to thereby obtain a focused image.

Abstract: A photographic lens having four components of characteristic forms with the 1st component counting from front being axially moved forward while the 2nd component is moved axially in a given relation to the 1st component as focusing is effected down to shorter object distances.

Abstract: A photographic objective of small size, having five lens elements of which the 1st counting from the front is of positive power and in the meniscus form convex toward the front, the 2nd is of negative power, the 3rd is of positive power and turns its convex rear surface toward the rear, the 4th is of positive power and the 5th is of negative power and in the meniscus form convex toward the rear. Numerical limits are given to certain design features of these five lens elements so that good correction of aberrations is attained.

Abstract: A light receiving apparatus for use in single-lens reflex camera is disclosed. A beam splitter is disposed between the swing-up mirror of the camera and the film plane to divide the light transmitted through the taking lens into a plural number of beams. To receive the divided beams there are provided a plural number of photoreceptors in the respective optical paths of the divided beams.

Abstract: A light measuring device for a single lens reflex camera provided with an auxiliary mirror for light measurement behind the movable mirror is disclosed. The reflection surface of the auxiliary mirror of said light measuring device is divided into a plurality of regions, and reflected light beams from the respective regions proceed in different directions from each other. Either one or both of the light beams reflected from one region and the beam reflected from the other region is or are selectively directed to a light sensitive element by a light beam selecting member.

Abstract: The disclosed photographic objective includes, from front to rear, a first lens of meniscus form convex toward the front and having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens of meniscus form which is concave toward the front and has a negative refractive power and whose front surface is aspheric, with the refractive power and configuration of each lens appropriately set to achieve compactness while permitting good correction of aberrations.