1984-11-29
1988-05-03
Corbin, John K.
350431, 350437, 350449, G02B 1502, G02B 1320
Patent
active
047416050
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE PRIOR ART
An objective with these properties is known from U.S. Pat. No. 3,588,227 and is designed to serve as a microscope objective. Two objects in front of the objective are imaged sharply in the focal plane and with the same magnification. According to the principle of the known design, at the image-side focus of the objective, an optical element is arranged which in one half of this focal plane functions as a positive lens, acting to focus the closest object on the focal plane, and in the other half thereof functions as a plane-parallel disc without any net refraction (thus only the refractive power of the objective itself acts on beams in this half) so that the beams from the more distant object are not refracted as much and, because of a choice of suitable dimensions, are focused in the very same focal plane.
SUMMARY OF THE INVENTION
One object of the present invention is to produce a photographic objective, which is of particular use in moving picture and TV-cameras, making it possible in a single scene to provide sharp images of two objects at different distances, i.e., each with its own depth of field. The image thus combined should have a natural appearance, and if two different optical systems are used, it is particularly important that the unsharp image of one object made by the system which makes a sharp image of the other object, disrupt the sharp image of the other system as little as possible. Otherwise, the unsharp image could create a visible ghost image. If, however, the fuzzy image is of the same size as and is superimposed on a sharp image, the image will be perceived as sharp.
It is previously known to achieve this purpose by using two different objectives and mirror devices. Major mechanical stability problems are encountered in this case, however. Furthermore, it is difficult to make two images coincide exactly, one with a sharp object A and an unsharp object B and the other with an unsharp object A and a sharp object B. The two images of A, one sharp and one unsharp, must be superimposed on each other even if they do not lie in the center of the image surface, which means that the objective must provide the same magnification. One purpose of the invention is to achieve such a consolidation of images, and to do this with a single objective, suited to photography, cinematography, TV, etc.
The objective revealed by the above-mentioned patent specification does not constitute a solution to the problem according to the invention. Two objects A and B at different distances will each be sharply imaged in individual halves by the known objective and be of the same size, but at the same time the unsharp images will be of different sizes, and therefore an unsharp and different-sized image of A, for example, will be superimposed on the sharp image of A. This will have a very disturbing effect in a cinematographic picture, for example.
In other designs, relating to photographic objectives, lenses divided into zones are used, similar to Fresnel lenses, for instance, and are revealed in, for example, No. GB-A-335 696 and U.S. Pat. Nos. 2,546,996 and 2,651,237. While the zones do provide sharp images of objects at different distances, the problem of the unequal magnifications of the unsharp ghost images of the different objects has not been addressed and therefore the purpose of the present invention has not been achieved. It is true that U.S. Pat. No. 2,651,238 discusses this problem, but the solution there indicated was that the ghost images be so greatly out of focus that they do not disturb the sharp images, which can be difficult to achieve except with very small individual depths of field and with a large aperture.
The above-mentioned purpose and other purposes and advantages are achieved according to the invention, which has an image-forming objective of the type described by way of introduction, in which the corrective element is arranged in the objective focal plane closest to the object. The unsharp image of an object, which is also giving a sharp image, will be
REFERENCES:
patent: 2546996 (1951-04-01), Garutso
patent: 3388650 (1968-06-01), Westphalen
patent: 3588227 (1971-06-01), Yamamoto et al.
Alfredsson Hans
Ingelstam Erik
Moller Bo
Ohlsson Per-Olof
Vogl Georg
AB Svensk Filmindustri
Corbin John K.
Sugarman Scott J.
Svenska Ord AB
LandOfFree
Multifocal objective does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multifocal objective, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multifocal objective will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1502292