Optical: systems and elements – Lens – Eyepiece
Reexamination Certificate
2001-04-19
2003-12-23
Mai, Huy (Department: 2873)
Optical: systems and elements
Lens
Eyepiece
C359S645000, C396S373000, C396S378000
Reexamination Certificate
active
06667836
ABSTRACT:
The present invention relates to a viewfinder for camera having a video signal tap and, in particular, a viewfinder eyepiece for viewing a display device, such as a cathode ray tube (CRT), liquid crystal device (LCD), or the like, in the viewfinder of a camera, such as on a high definition (HD) video camera.
Professional video cameras for electronic news gathering (ENG), for electronic field production (EFP) and for studio use heretofore have used a relatively compact viewfinder that extends from the front of the camera to one side and then rearwardly for a short distance for convenient use by the cameraman when the HD video camera is supported on the cameraman's shoulder. The conventional viewfinder has a small CRT facing laterally which is viewed by the cameraman through an eyepiece and a mirror positioned at 45° to reflect the image displayed on the CRT. When the HD video camera is used on a tripod, a dolly, a crane or other camera support for an extended period of time, it becomes inconvenient to use the conventional viewfinder that extends for such a short distance that the cameraman must position his head adjacent the camera as though it was supported on his shoulder. Therefore the conventional viewfinder now is usually provided with an optical extension having additional optical elements to move the viewing position rearwardly to a more convenient location when the HD video camera is supported on a tripod or the like. However, since the CRT in the conventional viewfinder remains at the front of the camera facing laterally toward the mirror, the optical extension must include appropriate optical elements as an eyepiece for viewing the CRT at a greater distance than the eyepiece of the non-extended conventional viewfinder, and those optical elements must be different for each optical extension of a different length, thereby increasing the cost of a set of optical extensions of different lengths for accommodating the preferences of different cameramen. Moreover, the increased distance from the viewing position to the CRT when using optical extensions reduces the quality of the image viewed by the cameraman. Further, the conventional eyepiece has a limited diopter focus range, usually only from about zero (0) to plus three (+3) diopters, for accommodating the eyesight of the cameraman, which range is inadequate for nearsighted (myopic) and extremely farsighted (hypermyopic) persons.
Therefore, it is a principal object of the present invention to provide a novel viewfinder for a camera having a video tap that solves the aforementioned and other problems and shortcomings of the conventional video camera viewfinder. Specifically, it is an object of this invention to provide such a camera viewfinder in which a viewing module comprises a display device portion directly connected to an optical eyepiece, which module is repositioned as a unit, with or without a structural, non-optical extension for lengthening or shortening the viewfinder, whereby the display viewed by the cameraman remains optimal and the same. Another object of this invention is to provide a viewing module of a viewfinder for a camera having a video tap in which the viewing module includes an optical eyepiece with an adjustable focus over a large diopter focus range. Still another object is to provide such a viewing module in which the eyepiece is comprised of three powered lenses or lens groups on the optical axis in which only the middle lens or lens group is movable for adjusting the focus, whereby the length of the eyepiece does not change over the entire diopter focus range adjustment. A further object of this invention is to provide such a viewing module for the viewfinder of a camera having a video tap in which the three lenses or lens groups are comprised of a negative powered lens adjacent the image display device, such as a CRT or LCD, a positive powered lens in the middle and a positive powered lens adjacent the eye of the viewer. Another object of this invention is to provide a viewfinder eyepiece with a large eye relief distance for viewer comfort.
REFERENCES:
patent: 4217048 (1980-08-01), Egawa
patent: 5446590 (1995-08-01), Kikuchi
patent: 5749008 (1998-05-01), Ishihara et al.
patent: 6252729 (2001-06-01), Kanai
patent: 2002/0191300 (2002-12-01), Neil
patent: 5-346608 (1993-12-01), None
Literature from OpTex entitled “Electronic Extension Viewfinder For Sony ENG Cameras”, dated Nov. 1990.
Mai Huy
Panavision Inc.
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