Photography – With exposure objective focusing means – focusing aid – or... – Optical detail with photoelement system
Reexamination Certificate
1999-09-24
2001-02-13
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Optical detail with photoelement system
C396S121000
Reexamination Certificate
active
06188845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multipoint focus detecting apparatus for an optical instrument such as an SLR camera.
2. Description of the Prior Art
In recent years, SLR cameras provided with a multipoint focus detecting unit for determining a focus state (defocus) at each of a plurality of focus detection zones (focusing points) have been developed. In the optical system of a conventional multipoint focus detecting unit, other than the central focus detection zone arranged over the optical axis, one or more off-center focus detection zones are arranged away from the optical axis, and bundle of rays which form an object image which are passed through the central and off-center focus detection zones are respectively deflected by corresponding mirrors to be incident on corresponding light receiving elements arranged in a horizontal line. For instance, a light bundle of an object image which is passed through the horizontally-elongated central focus detection zone is deflected once by a mirror to be focused on a corresponding horizontally-elongated array of light receiving elements. At this time, the image observed through the horizontally-elongated central focus detection zone is divided into two, by a corresponding pair of separator lenses, to be formed as two separate images on the corresponding horizontally-elongated array of light receiving elements. At the same time, another light bundle of the object image which is passed through a vertically-elongated off-center focus detection zone is deflected twice by two mirrors to be focused on a corresponding horizontally-elongated array of light receiving elements. The image observed through the vertically-elongated off-center focus detection zone is divided into two by a corresponding pair of separator lenses to be formed as two separate images on the corresponding horizontally-elongated array of light receiving elements. The central and off-center pairs of separator lenses are arranged away from the central and off-center light receiving elements by a predetermined distance.
In the optical system of such a conventional multipoint focus detecting unit, the principal rays which have respectively passed through the corresponding pairs of separator lenses to proceed towards the corresponding arrays of light receiving elements, are not parallel to one another. Accordingly, once a mechanical dimensional error occurs and/or the arrays of light receiving elements deviate from the original positions along the optical axis direction thereof, the light bundles which are respectively passed through the corresponding pairs of separator lenses cannot be precisely led to the corresponding arrays of light receiving elements, which makes it difficult to adjust the position of each light bundle relative to the corresponding arrays of light receiving elements. Since the principal rays of the light bundles which are respectively passed through the corresponding pairs of separator lenses are not parallel to one another, the respective spaces among the principal rays vary if the arrays of light receiving elements deviate forwardly or rearwardly. This requires the position of each array of light receiving elements to be adjusted in the forward/reward direction thereof.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a multipoint focus detecting apparatus having a structure with which a mechanical dimensional error, and/or an error due to an imprecise assembly, does not easily occur and which makes it possible to easily adjust the position of each array of light receiving elements relative to the incident light bundle thereon even if such errors occur.
To achieve the object mentioned above, according to an aspect of the present invention, there is provided a multipoint focus detecting apparatus having a plurality of focus detecting zones arranged in a first pattern on a predetermined focal plane, and a corresponding plurality of arrays of light receiving elements which are arranged in a second pattern that is different from the first pattern, wherein a corresponding plurality of light bundles which are passed through the plurality of focus detecting zones are made incident on the plurality of arrays of light receiving elements, respectively. The multipoint focus detecting apparatus includes: a plurality of pairs of separator lenses, each pair of which divides an image in a corresponding one of the plurality of focus detecting zones into two separate images on a corresponding one of the plurality of arrays of light receiving elements; a separator mask positioned in front of the plurality of pairs of separator lenses and including a plurality of pairs of openings to correspond to the plurality of pairs of separator lenses, each opening of the plurality of pairs of openings determining the size of a bundle of rays which enters a corresponding one separator lens of the plurality of pairs of separator lenses; and a light bundle deflector positioned in the close vicinity of the plurality of pairs of separator lenses. A first array of the plurality of arrays of light receiving elements, on which a first light bundle which is passed through a first focus detecting zone of the plurality of focus detecting zones is incident, and a second array of the plurality of arrays of light receiving elements, on which a second light bundle which is passed through a second focus detecting zone of the plurality of focus detecting zones is incident, are aligned so as to be parallel to each other and apart from each other by a predetermined distance in a direction perpendicular to a direction in which light receiving elements of each of the plurality of arrays of light receiving elements are aligned; and wherein the light bundle deflector is positioned in the vicinity of the plurality of pairs of separator lenses so that a principal ray of the first light bundle and a principal ray of the second light bundle extend parallel to each other in a plane perpendicular to the direction in which the light receiving elements are aligned.
Preferably, the light bundle deflector includes a plurality of auxiliary lenses each of which is positioned in front of a corresponding opening of the plurality of pairs of openings so that the optical axis of each the auxiliary lens is decentered from a center axis of the corresponding opening.
Preferably, the light bundle deflector includes a plurality of prisms positioned in front of the plurality of pairs of openings, respectively.
Preferably, each separator lens of the plurality of pairs of separator lenses is decentered from a center axis of a corresponding opening of the plurality of pairs of openings.
According to another aspect of the present invention there is provided a multipoint focus detecting apparatus having a plurality of focus detecting zones arranged in a first pattern on a predetermined focal plane, and a corresponding plurality of arrays of light receiving elements which are arranged in a second pattern that is different from the first pattern, wherein a corresponding plurality of light bundles which are passed through the plurality of focus detecting zones are made incident on the plurality of arrays of light receiving elements, respectively. The multipoint focus detecting apparatus includes: a plurality of pairs of separator lenses, each pair of which divides a light bundle of an image observed through a corresponding one of the plurality of focus detecting zones into two light bundles, so that the light bundle is formed as two separate images on a corresponding one of the plurality of arrays of light receiving elements; and a separator mask positioned in front of the plurality of pairs of separator lenses and including a plurality of pairs of openings to correspond to the plurality of pairs of separator lenses, each opening of the plurality of pairs of openings determining the size of a bundle of rays which enters a corresponding one separator lens of the plurality of pairs of separator lenses. A first array of the plurality of arrays of
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Perkey W. B.
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