Abstract: An optical system is presented that enables images of a wide range of natural subjects to be well reproduced with their colors, and provides an image pickup system including, at least, an image pickup optical system, an electronic image pickup device having three or more different spectral characteristics to obtain a color image, and a controller for implementing signal processing or image processing on the basis of an output from the electronic image pickup device. The optical element that takes part in determining the focal length in the image pickup system includes an optical element making use of a refraction phenomenon alone.

Abstract: An optical system enables images to be well reproduced with their colors, and provides an image pickup system including an image pickup optical system, an electronic image pickup device to obtain a color image and a controller for implementing signal processing or image processing on the basis of an output from the electronic image pickup device. The optical element that takes part in the determination of a focal length includes an optical element making use of a refraction phenomenon alone. The 400-nm wavelength input/output ratio is 10% or less with respect to an input-output ratio for a 400-nm to 800-nm wavelength at which an output signal strength ratio with respect to an input quantity of light is highest when the input quantity of light is defined by the quantity of a light beam emanating from the same object point and entering the image pickup optical system and the output signal strength is defined by the strength of a signal produced from the controller in response to the light beam.

Abstract: An objective lens includes, in order from the object side, a first lens (L1) with negative power, a second lens (L2) with positive power, an aperture stop (AS), and a third lens (L3) with positive power. A lens component located on the image side of the aperture stop (AS) is constructed with a positive single lens or a plurality of positive single lenses, and the objective lens satisfies the following conditions: 45<vd1?vd2 ?0.6<f1/f2<?0.3 where vd1 is the Abbe's number of the first lens, vd2 is the Abbe's number of the second lens, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.

Abstract: The invention relates to an optical system which, albeit being simple in construction, enables images of a wide range of natural subjects to be well reproduced with their colors, and provides an image pickup system comprising, at least, an image pickup optical system 1, an electronic image pickup device 3 having three or more different spectral characteristics to obtain a color image and a controller 4 for implementing signal processing or image processing on the basis of an output from the electronic image pickup device. The optical element that takes part in the determination of a focal length in said image pickup system comprises an optical element making use of a refraction phenomenon alone.

Abstract: An objective lens includes, in order from the object side, a first lens (L1) with negative power, a second lens (L2) with positive power, an aperture stop (AS), and a third lens (L3) with positive power. A lens component located on the image side of the aperture stop (AS) is constructed with a positive single lens or a plurality of positive single lenses, and the objective lens satisfies the following conditions: 45<vd1?vd2 ?0.6<f1/f2<?0.3 where vd1 is the Abbe's number of the first lens, vd2 is the Abbe's number of the second lens, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: The invention relates to a zoom lens system which has a higher wide angle a high zoom ratio with well-corrected aberrations, is fast, and has a large back focus. The zoom lens comprises, in order from its object side, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power and a fourth lens group G4 having positive refracting power. For zooming from a wide-angle end to a telephoto end of the zoom lens system, the second lens group G2 moves toward an image side of the zoom lens system, the third lens group G3 moves toward the object side and the fourth lens group moves toward the object side. A lens located nearest to the image side in the third lens group G3 is a negative lens concave with respect to an image plane of the zoom lens system and a lens located nearest to the object side in the fourth lens group G4 is a negative lens concave with respect to an object.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: The invention relates to a zoom lens system which has a higher wide angle a high zoom ratio with well-corrected aberrations, is fast, and has a large back focus. The zoom lens comprises, in order from its object side, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power and a fourth lens group G4 having positive refracting power. For zooming from a wide-angle end to a telephoto end of the zoom lens system, the second lens group G2 moves toward an image side of the zoom lens system, the third lens group G3 moves toward the object side and the fourth lens group moves toward the object side. A lens located nearest to the image side in the third lens group G3 is a negative lens concave with respect to an image plane of the zoom lens system and a lens located nearest to the object side in the fourth lens group G4 is a negative lens concave with respect to an object.

Abstract: The invention relates to a zoom lens system which has a higher wide angle a high zoom ratio with well-corrected aberrations, is fast, and has a large back focus. The zoom lens comprises, in order from its object side, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power and a fourth lens group G4 having positive refracting power. For zooming from a wide-angle end to a telephoto end of the zoom lens system, the second lens group G2 moves toward an image side of the zoom lens system, the third lens group G3 moves toward the object side and the fourth lens group moves toward the object side. A lens located nearest to the image side in the third lens group G3 is a negative lens concave with respect to an image plane of the zoom lens system and a lens located nearest to the object side in the fourth lens group G4 is a negative lens concave with respect to an object.

Abstract: The invention relates to a zoom lens system which is compatible with a TTL optical finder having a diagonal field angle of at least 70° at the wide-angle end and about 7 to 10 magnifications and is fast as represented by an F-number of about 2.8 at the wide-angle end. The zoom lens system comprises a first lens group G1 which is movable along its optical axis during zooming and has positive refracting power, a second lens group G2 which moves toward the image side along the optical axis during zooming from the wide-angle end to the telephoto end and has negative refracting power and rear lens groups G3 to G6 having at least two spacings variable during zooming. In particular, the focal length f1 of the first lens group G1 should meet 6<f1/L<20 where L is the diagonal length of an effective image pickup surface I located in the vicinity of an image-formation plane.

Abstract: A distortion-free and compact image-forming optical system with a minimal number of optical components which provides a wide image area and which is favorably corrected for ray aberrations and arranged in a compact structure by folding an optical path. A pentagonal prism member (5) has a first surface (1), a second surface (2), a third surface (3), and a fourth surface (4). The first surface (1) and the fourth surface (4) are refracting surfaces. The second surface (2) and the third surface (3) are reflecting surfaces. The first surface (1) is formed from a spherical surface. The second surface (2), the third surface (3) and the fourth surface (4) are formed from three-dimensional surfaces. Light rays from an object plane O provided on the back side of a cover glass (6) pass through the cover glass (6) and enter the prism member (5) through the first surface (1). The incident light rays are reflected successively by the second surface (2) and the third surface (3).

Abstract: A real image mode variable magnification finder has an objective system with positive refracting power, an image erecting optical system for erecting an object image formed by the objective system, and an eyepiece system with positive refracting power. The objective system includes a first lens unit with negative refracting power, a second lens unit with positive refracting power, and a third lens unit with positive refracting power, so that a space between the first lens unit and the second lens unit and a space between the second lens unit and the third lens unit are changed when the magnification of the finder is changed in the range from a wide-angle position to a telephoto position. The image erecting optical system has a first prism and a second prism so that a field frame is interposed between the first prism and the second prism. The finder also satisfies the following condition:-0.5<n/m<0.

Abstract: The invention provides a zoom lens system which achieves a wide angle of field, has a simplified construction, and is suitable for use on video cameras. The zoom lens system comprises, in order from an object side thereof, a first lens group G1 having positive refracting power, a second lens group G2 having negative refracting power, a third lens group G3 having positive refracting power, and a fourth lens group G4 having positive refracting power. The second lens group G2 moves toward an image side thereof while the third G3 and fourth G4 lens groups move constantly toward the object side for zooming from a wide-angle end thereof to a telephoto end thereof. The first lens group G1 consists only of a positive single lens.

Abstract: A zoom lens system composed, in order from the object side, of a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive or negative refractive power and a fourth lens unit having a positive refractive power; and configured to change a magnification thereof by moving the second lens unit and moving the fourth lens unit monotonously toward the object side from its location at a wide position to a tele position. A ratio of a focal length of the first lens unit relative to that of the fourth lens unit is defined within a specific range and a magnification of the fourth lens unit at the tele position is specified within a definite range.

Abstract: An optical system for monitor cameras to be mounted on vehicles comprising a camera body disposed so as to be accommodatable into a support erected on a vehicle, a photographic lens system disposed in the camera body, an image pickup device having a light receiving surface which is disposed at an imaging location of the photographic lens system and directed perpendicularly to a longitudinal direction of the support, and a prism for changing a direction toward a visual field which functions to image a visual field in a horizontal direction onto the light receiving surface of the image pickup device.

Abstract: The invention provides a zoom lens system having a zoom ratio as high as about 8 to 12 but is of wide field angle and small size, and is suitable for use on a video camera, said zoom lens system comprising a positive first lens unit L1 which is movable in an orbit, said orbit displaceable toward objet side at the telephoto end position rather than at the wide-angle end position, a negative second lens unit L2 which is movable in an orbit, said orbit displaceable toward the image side at the telephoto end position rather than at the wide-angle end position, a positive third lens unit L3 which is movable in an orbit, said orbit displaceable toward the object side at the telephoto end position rather than at the wide-angle end, and a positive or negative fourth lens unit L4 which is movable, and conforming to2.6<f.sub.l /(f.sub.W .multidot.f.sub.T).sup.1/2 <6 (1)-1.2<.beta..sub.2T <-0.7 (2)3.2<.beta..sub.2T /.beta..sub.2W <8 (3)where:f.sub.l is the focal length of the first lens unit,f.sub.

Abstract: A compact four-unit type of zoom lens system particularly suited for video cameras. The zoom lens system has a variable power ratio of about 6-8 and is made up of a reduced number of about 9-11 lenses. This zoom lens system comprises a first lens unit I having a positive refractive power, a second lens unit II having a negative refractive power, a third lens unit III having a positive refractive power and a fourth lens unit IV having a positive refractive power. The first and third lens units I and III are movable toward the object side for zooming from the wide angle end to the telephoto end while the second lens unit II remains fixed. The fourth lens unit IV is movable for correcting image position variations. The third lens unit III includes at least one positive lens element and one negative lens element with a concave surface facing the fourth lens unit IV. The fourth lens unit IV includes one positive lens element and may further include one negative lens element.

Abstract: A compact and light-weight zoom lens system including, in the order from the object side, a first lens unit having a negative refractive power, a second lens unit comprising a negative lens element and having a positive refractive power, and a third lens unit having a positive refractive power. The zoom lens system is adapted so as to perform variation of focal length by moving the second lens unit and the third lens unit along the optical axis while varying the airspace reserved between these lens units with the first lens unit kept stationary.