Elmo Company, Limited

Yasuhiro Kondo

Masaaki Toguchi

Kazuyoshi Yamada

In the zoom lens, the second lens group includes at least one surface that is an aspheric surface, and during changing magnification, the second lens group, the third lens group, and the fourth lens group are respectively capable of moving independently, with the position of the aperture moving along a convex trajectory on the optical axis from the image side to the object side during changing magnification. Through operation in this manner, the zoom lens of the invention is inexpensive and compact, and efficiently corrects various types of aberration. Thus, at a high magnification ratio of 5&#xd7; or greater, the zoom lens of the invention affords a wide field exceeding approximately 78 degrees at the wide angle end, and affords a high performance compact zoom lens whose distortion is held to 3% or less.

Zoom lens

A mechanical cam type zoom lens device includes a movement position detector detecting movement positions of focus and zoom lenses moved by respective drivers, a reference compensation value calculating unit setting a plurality of zooming positions for a zoom lens when a focus lens is located at a predetermined focusing position and calculating an amount of movement from a predetermined focusing position in a case where the focus lens is adjusted to be in focus when the zoom lens is located at each set zooming position, the calculated amount of movement serving as a reference compensation value, a storage storing data of the reference compensation values, a focusing compensation value calculating unit calculating a focusing compensation value for the focus lens in a case where the zoom lens is located at the movement position, based on the set zooming positions, the reference compensation value read from the storage and the movement position of the zoom lens, and a focusing unit focusing the focus lens based on the calculated focusing compensation value so that the focus lens is focalized.

Mechanical cam type zoom lens device

A reflective-type infrared ray cut filter and associated manufacturing method wherein the time and cost of manufacture are reduced and manufacturing efficiency is improved are provided. In the infrared ray cut filtercomprising a multilayer membranecomposed of no less than 16 but no more than 32 layers of a high-refractive index thin membraneand a low-refractive index thin membranelaminated in an alternating fashion and formed on a glass substrate, the first layer from the side of the glass substrateis a high-refractive index thin membraneand the last layer is a low-refractive index thin membrane, and where the design wavelength is deemed &#x3bb;, the first and second layers are formed to have an optical thickness of no less than &#x3bb;/4, the third layer through a prescribed layer are formed to have an optical thickness of no more than &#x3bb;/4, the layers between the prescribed layer and the last layer are formed to have an optical thickness of no less than &#x3bb;/4, and the last layer is formed to have an optical thickness of no more than &#x3bb;/4.

Infrared ray cut filter and methods for manufacturing the same

A wide-angle lens system having a long back focal length, disposed in front of a &#x2153;&#x2033; CCD camera and the focal length (f) for all lens groups is 3.0 mm, the F-number is 3.0 and the half-field angle is 46&#xb0;. The following conditions are met by the first lens group: 1&#x2266;d/d&#x3c;1.2; R/R=0.99; and d/f=0.03. Here, (d) indicates the thickness of the second lens along the normal line at a given distance from the optical axis within the maximum effective diameter of the object side convex surface of the lens. dis the thickness of the second lens along the optical axis.

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Nagoya, Japan

Yasuhiro Kondo