Photography – Having variable focal length of camera objective – Lens moves in or out of light path
Reexamination Certificate
1999-03-03
2001-10-23
Gray, David M. (Department: 2851)
Photography
Having variable focal length of camera objective
Lens moves in or out of light path
C359S694000
Reexamination Certificate
active
06308013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a converter unit of a camera, and more particularly to a converter unit of a camera, which is capable of adjusting optical axes of converter lenses that are inserted into an optical path of a lens unit of the camera.
2. Description of Related Art
According to a conventional converter unit of a lens unit for a broadcasting TV camera, an external control lever, etc. is operated to insert a converter lens into an optical path of the lens unit to thereby alter the focal length of the lens unit. For example, when a 2× extender lens enters the optical path of the lens unit, the focal length of the lens unit is doubled.
Recently, in the field of broadcasting TV cameras, there is a camera capable of selectively switching the aspect ratios between 4:3 and 16:9. In this switchable camera, a charge-coupled device (CCD) of the aspect ratio 16:9 is used for an imaging device. When the aspect ratio is set at 4:3, the right and left areas of the CCD are unused and only the area with the aspect ratio 4:3 at the center is used. Accordingly, the angle of view is reduced by approximately 20%, and the focal length of the lens unit appears to become longer.
To eliminate the above-mentioned disadvantage, it is proposed that an approximately 0.8×converter lens, which is called a ratio converter lens, is arranged on the optical path of the lens unit to compensate the focal length of the lens unit when the aspect ratio is set at 4:3.
Moreover, there is a conventional converter unit that is provided with the extender lens and the ratio converter lens to extend the focal length of the lens unit and compensate the focal length on the aspect ratio 4:3. The extender lens extends the focal length of the lens unit whereas the ratio converter lens contracts it. Both the extender lens and the ratio converter lens, however, are converter lenses for altering the focal length of the lens unit, and they are constructed in the same manner.
The applicants have proposed a converter unit that includes two kinds of extender lenses in Japanese Patent Provisional Publication No. 8-171043. According to this converter unit, the extender lenses are revolvably mounted on a single rod in order to simplify the structure, and a desired extender lens is revolved as the need arises and enters and leaves the optical path of the lens unit. One of the applicants has proposed the same in the case that one of the extender lenses is the ratio converter lens in Japanese Patent Provisional Publication No. 9-264077. According to these converter units, the optical axes of the extender lenses are adjusted at the same time by adjusting the direction of the single rod when the extender lenses are inserted into the optical path of the lens unit.
It is, however, difficult to adjust the optical axes of both the extender lenses at the same time by adjusting the direction of the single rod. For this reason, the optical axis of one of the extender lenses that is more sensitive or of a higher magnification is priorly adjusted in the past, but in this case, the optical axis of the other extender lens with the lower magnification (or the ratio converter lens) greatly deviates.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the above-described circumstances, and has as its object the provision of a converter unit for a lens unit of a camera, which is able to match optical axes of a plurality of kinds of converter lenses with different magnifications, which are revolvably mounted on a rod, with an optical axis of the lens unit properly.
To achieve the above-mentioned object, the present invention is directed to a converter unit for a lens unit of a camera, comprising: a rod fixed in a body of the converter unit; a cylindrical collar member perforated with a hole, an external circumference of the collar member being eccentric with the hole, the rod being inserted in the hole; and a converter lens revolvably mounted on the external circumference of the collar member, the converter lens being revolved to enter and leave an optical path of the lens unit to alter focal length of the lens unit.
According to the present invention, the converter lens is revolvably mounted on the eccentric external circumference of the cylindrical collar member attached on the rod, and the collar member is rotated to adjust the eccentric direction of the eccentric external circumference, thereby adjusting the direction of the revolving axis of the converter lens. It is therefore possible to match the optical axis of the converter lens with the optical axis of the lens unit.
The present invention is directed to the converter unit further comprising a second converter lens revolvably mounted on the rod, the second converter lens being revolved to enter and leave the optical path of the lens unit to alter the focal length of the lens unit. The converter lens mounted on the collar member preferably has higher magnification than the second converter lens mounted on the rod. The collar member is rotated to independently adjust the optical axis of the converter lens with the higher magnification. Therefore, the optical axis of the converter lens with the higher magnification, which requires the accurate adjustment of the optical axis thereof, can be adjusted properly without affecting the optical axis of the converter lens with the lower magnification, which can be sufficiently accurate if the rod is attached accurately. Consequently, the optical axes of the converter lenses are properly matched with the optical axis of the lens unit.
In addition, the converter unit may further comprise a second cylindrical collar member perforated with a hole, an external circumference of the second collar member being eccentric with the hole of the second collar member, the external circumference of the second collar member being supported in the body of the converter unit; wherein the rod is inserted in the hole of the second collar member and fixed in the body of the converter unit through the second collar member. Thus, the first eccentric collar member adjusts only the optical axis of one of the converter lenses, and the second eccentric cylindrical member adjusts the direction of the rod. It is therefore possible to separately adjust the optical axes of the two kinds of converter lenses.
The present invention is also directed to a converter unit for a lens unit of a camera, comprising: a cylindrical collar member perforated with a hole, an external circumference of the collar member being eccentric with the hole, the external circumference of the collar member being supported in a body of the converter unit; a rod inserted in the hole of the collar member; and a converter lens revolvably mounted on the rod, the converter lens being revolved to enter and leave an optical path of the lens unit to alter focal length of the lens unit.
REFERENCES:
patent: 4482228 (1984-11-01), Fujita
patent: 4525050 (1985-06-01), Ohashi
patent: 4573780 (1986-03-01), Sato et al.
patent: 4825235 (1989-04-01), Wakabayashi et al.
patent: 4887107 (1989-12-01), Nakamura et al.
patent: 5696634 (1997-12-01), Watanabe et al.
patent: 5751353 (1998-05-01), Tanaka et al.
patent: 8-171043 (1996-07-01), None
patent: 11-101933 (1999-04-01), None
Tanaka Minoru
Yamamoto Shigeru
Fuji Photo Optical Co., Ltd.
Gray David M.
Nixon Peaboy LLP
Safran David S.
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