Photography – With exposure objective focusing means – focusing aid – or... – Optical detail with photoelement system
Reexamination Certificate
2001-10-03
2004-07-20
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Optical detail with photoelement system
Reexamination Certificate
active
06766112
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of the following priority applications are herein incorporated by reference:
Japanese Patent Application No. 2000-100947 filed Apr. 3, 2000
Japanese Patent Application No. 2000-133733 filed May 2, 2000
Japanese Patent Application No. 2000-206690 filed Jul. 7, 2000
Japanese Patent Application No. 2001-206599 filed Jul. 6, 2001
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a focal point detection apparatus that detects the focal adjustment state of a photographic optical system and a focal point detection module.
2. Description of the Related Art
Focal point detection apparatuses adopting the phase difference detection method in the known art include those having focal point detection areas set both on the optical axis and off the optical axis. Attempts to achieve a more compact unit and improve the detection accuracy have been made in the prior art, as explained below in reference to the focal point detection apparatuses presented as first~fourth prior art examples.
It is to be noted that such prior art technologies are described in, for instance, “Autofocusing Technology Adopted In Single Lens Reflex Cameras” included in “Optics” Vol. 18, No. 11 (published by Japan Optics Society, a section of the Applied Physics Society, in November, 1989).
In the first prior art example, a condenser lens is decentered relative to a field aperture so as to ensure that a focal point detection light flux having advanced off the axis of the photographic lens and then having passed through the field aperture, enters the condenser lens further outward relative to the photographic optical axis from the condenser lens center.
The second prior art example is disclosed in Japanese Laid-Open Patent Publication No. H 9-304691. In the second prior art example, a focal point detection light flux having advanced off the axis of the photographic lens is deflected toward the photographic optical axis by using a sub-mirror.
While a more compact focal point detection apparatus may be achieved by adopting the technology in the first or second prior art example, the so-called “squint” phenomenon becomes an issue to be addressed since focal point detection light fluxes resulting from pupil division diagonally enter a pair of focal point detection light-receiving elements from the same direction.
In the focal point detection apparatus in the third prior art example (see Japanese Laid-Open Patent Publication No. H 3-235906), an image sensor is rotatably held around an axis perpendicular to the direction along which the light-receiving element rows are arrayed at the image sensor and also perpendicular to the optical axis, in order to address the problem of the squint phenomenon. While the technology in the third prior art example eliminates the problem of the squint phenomenon manifesting in the third and second prior art examples, the focal point detection module is bound to become large.
The fourth prior art example (see Japanese Laid-Open Patent Publication No. H 9-243905) represents another method for solving the problem of the squint phenomenon. In the focal point detection apparatus in the fourth prior art example, a plurality of focal point detection light fluxes having advanced off the axis of the photographic lens are individually deflected at optimal angles to set them roughly parallel to the optical axis by using a sub-mirror.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the detection accuracy while achieving miniaturization of the focal point detection apparatus and the focal point detection module having focal point detection areas set both on the optical axis and off the optical axis.
Another object of the present invention is to provide a focal point detection apparatus and a focal point detection module achieving simplification in the mechanism that holds the focal point detection light-receiving elements via an angle adjustment mechanism.
The present invention is adopted in a focal point detection apparatus that guides a pair of light fluxes originating from a subject, and then passing off the optical axis of a photographic optical system to an image sensor by a focal point detection optical system, forms a pair of subject images on the image sensor and detects the focal adjustment state of the photographic optical system based upon the degree to which the pair of subject images are offset. The objects described above are achieved by providing a first deflection member that is positioned between the photographic optical system and a predicted focal plane of the photographic optical system to deflect the pair of light fluxes from the subject having passed off the optical axis of the photographic optical system toward the optical axis and a second deflection member that deflects the pair of light fluxes from the subject which have been deflected by the first deflection member to allow them to advance substantially parallel to the optical axis, at the focal point detection optical system. The second deflection member may be set to one of the front and the rear of a field mask of the focal point detection optical system through which the subject light fluxes from the first deflection member are first transmitted.
The second deflection member may be provided behind a condenser lens of the focal point detection optical system.
The second deflection member may be constituted of a condenser lens included in the focal point detection optical system. In such a case, the focal point detection optical system should be constituted by ensuring that the principal ray of a focal point detection light flux enters at positions decentered from the optical axis of the condenser lens.
The present invention is also adopted in a focal point detection module having an optical axis of a focal point detection optical system, which comprises a condenser lens that condenses photographic light fluxes passing through a plurality of focal point detection areas set both on and off the axis within a photographic image plane, a pupil division mask that achieves pupil division by restricting each of the photographic light fluxes passing through the individual focal point detection areas at a pair of apertures, an image reforming lens unit that reforms images of the pair of light fluxes resulting from the pupil of division achieved at the pupil division mask and an image-capturing element that converts the pair of light fluxes the images of which have been reformed on a light-receiving surface by the image reforming lens unit to electrical signals and outputs the electrical signals.
In the focal point detection module, the objects described above are achieved by positioning the pair of apertures of the pupil division mask relative to off-axis lens portions so as to allow the pair of light fluxes achieved by dividing at the pupil division mask a light flux having passing through a focal point detection area to enter peripheral areas close to the optical axis of the focal point detection optical system in the off-axis lens portions corresponding to the focal point detection area among a plurality of lens portions included in the image reforming lens unit.
The off-axis lens portions each include an entry-side spherical surface and an exit-side spherical surface and when the line segment connecting the center of the entry-side spherical surface and the center of the exit-side spherical surface constitutes the optical axes of the off-axis lens portions, the projections achieved by projecting the optical axes of the off-axis lens portions onto a plane perpendicular to the direction of the pupil division should be roughly parallel to the optical axis of the focal point detection optical system and, in such a case, the positions of the centers of gravity of the pair of apertures may be set further toward the optical axis of the focal point detection optical system than the optical axis of the off-axis lens portions.
In the focal point detection module, it is preferable that curvatures each achieved in the entry-side spherical sur
Kanbayashi Hideki
Kuwata Chiyuki
Ozawa Masamitsu
Uchiyama Shigeyuki
Nikon Corporation
Oliff & Berridg,e PLC
Perkey W. B.
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