Photography – With data recording – Optical
Reexamination Certificate
2001-03-26
2002-11-05
Mathews, Alan A. (Department: 2851)
Photography
With data recording
Optical
Reexamination Certificate
active
06477330
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 2000-093068 filed on Mar. 30, 2000, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an unsophisticated data-imprinting optical system which can be applied to a camera capable of optically imprinting photographing data, such as a date, onto a film negative.
2. Description of the Prior Art
A system for a camera which enables imprinting of photographing data, such as a date, onto a film negative has hitherto been known, and imprinting of photographing data is one of the important functions of the camera.
Since long ago, such a system has been constructed such that a numerical string of a manually-set date is optically imprinted onto a film negative by means of a simple shutter which controls a projection lens and an exposure time. This system suffers a problem of a battery cell being depleted by an illumination lamp. Recent proliferation of a light source system which operates at an extremely-feeble electric current, such as an LED or liquid crystal, obviates the problem. Hence, the majority of cameras are equipped with this system. However, the system recently encounters a new problem, and another system capable of solving the new problem has recently been adopted.
In association with recent, rapid miniaturization of a camera, a limit is imposed on a space for positioning a data-imprinting optical system, and there arises a necessity for directly illuminating a numerical string or a string of characters by means of an LED or liquid crystal. The limit and the necessity account for the new problem. If a string of characters to be displayed is long, upsizing of a display element, such as an LED or liquid crystal, arises in addition to a problem of space. Accordingly, there arises a problem of inevitable use of a battery cell of large capacity, in addition to a cost problem. To solve the problems, there is employed a system which imprints data on a film negative, by means of illuminating a string of LEDs in a time sequence in the manner of a light sign board, and successively exposing the film in a time sequence through utilization of an automatic film take-up operation of the camera. This system involves use of only a single string of light sources. Traveling speed of a film negative rather than a shutter determines an exposure time, thereby imprinting data very efficiently. This is described in, for example, Japanese Unexamined Patent Publication No. 9(1997)-304823.
Such a data-imprinting optical system requires only an object size corresponding to the size of a single line of LEDs. The optical system has a narrow angle of view, and the only requirement is that image quality in the vicinity of center of the angle of view be compensated. Accordingly, sufficient performance of the optical system can be achieved by use of a single biconvex lens.
The foregoing system is predicated on an automatic film advancing operation of a camera. For this reason, the system cannot be applied to a low-cost, unsophisticated camera of manual-advance type which has recently become pervasive. The manual-advance camera involves indefinite film advance, which is very likely to result in unevenness in exposure of a character string.
An unsophisticated camera of manual advance type which has recently become pervasive requires a necessity of exposing data to be imprinted in the form of a regular character string by a single exposing operation. As a matter of course, strong demand has existed for miniaturizing such an unsophisticated camera. In contrast with the data-imprinting camera described previously, the unsophisticated camera encounters difficulties in reducing an imaging factor and the angle of view of a character string and constructing a projection lens from a single biconvex lens, which would otherwise increase an optical path length and hinder miniaturization of a camera.
Difficulties are encountered in direct application of the related-art technique to a data-imprinting optical system of an unsophisticated camera of manual advance type which has currently become pervasive. Therefore, development of a new data-imprinting optical system has been desired.
In connection with such a desire, there has been known a technique for exposing all display data within a single period of exposure time by a single operation, as described below.
Several methods for introducing extraneous light into the data-imprinting optical system are described in Japanese Unexamined Patent Publication No. 10(1998)-073878. Particularly, the publication includes a description about a lens-equipped camera of film type having a liquid-crystal display imprinting function. Back light is usually used for liquid crystal display. However, a camera is made inexpensive by use of the intensive extraneous light collected by a condenser lens. The technique has great value as a light-source system of a data impinging optical system. However, no contrivance has been made on the technique for realizing miniaturization of and space-saving in the camera.
Japanese Unexamined Patent Publication No. 10(1998)-254099 also describes a lens-equipped camera of film type having a liquid-crystal display imprinting function. More specifically, the publication describes a technique for collecting extraneous light on a liquid-crystal display surface more efficiently. However, this publication also fails to describe a contrivance to enable miniaturization of and space-saving in the camera.
The present invention has been conceived against the foregoing backdrop and is aimed at providing a data-imprinting optical system which can be applied to a low-cost, unsophisticated camera of manual film advance type and enables miniaturization of and space-saving in the camera.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a data-imprinting optical system which imprints, onto a film surface, data appearing on a photographing information/data display member located on the part of an object relative to the film surface and which is separate from a photographing lens, wherein
the optical system comprises one meniscus lens having a positive refractive power and a brightness aperture and satisfies conditional expressions (1) through (3) provided below:
3.9
≦L/F<
5.0 (1)
0.02
<D
1
/F<
0.10 (2)
−0.5
<R
3
/F<
−0.2 (3)
where,
L: distance from the photographing data display member to the film surface along the optical axis of a photographing lens,
F: focal length of the meniscus lens,
D
1
: distance from the aperture to the surface of the meniscus lens facing the aperture along the optical axis of the data-imprinting optical system, and
R
3
: the radius of curvature of the surface of the meniscus lens opposite that facing the aperture (a paraxial radius of curvature in a case where the surface is an aspherical surface).
Preferably, the meniscus lens is formed from an organic material, and the surface of the meniscus lens opposing the photographing information/data display member is aspherically concave. Further, the aperture is preferably located on the part of the meniscus lens opposing the photographing information/data display member.
Preferably, a conditional equation (4) provided below is satisfied when the angle of inclination assumes a positive value in a case where an optical axis of a photographing optical system moves away from an optical axis of the data-imprinting optical system as the data-imprinting optical system approaches the film surface:
0.0°≦&thgr;<10.0° (4)
Preferably, the data display member is disposed opposite the optical axis of the photographing optical system with reference to the optical axis of the data-imprinting optical system, and a conditional equation (5) provided below is satisfied, given that the minimum distance between the optical axis of the data-imprinting optical system and the data display member within a plane perpendicular to the optical axis of the data-imprintin
Fuji Photo Optical Co., Ltd.
Mathews Alan A.
Snider & Associates Ronald R. Snider
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