Optics: measuring and testing – Photometers
Reexamination Certificate
1998-10-27
2001-05-08
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Photometers
C356S218000, C356S222000
Reexamination Certificate
active
06229602
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photometering apparatus having a split type photodetector.
2. Description of the Related Art
In a known photometering apparatus in a camera, a light receiving surface of a photo sensor is located in a predetermined focal plane of an object image or in the vicinity thereof, so that the brightness of the object image formed on the light receiving surface can be detected by the photodetector. In a known photometering apparatus having a split type photodetector, the light receiving surface is split into a plurality of detection sections (areas) which detect the brightness of the object image incident thereupon.
In a split type photodetector, the light receiving surface is split into a plurality of detection areas corresponding to a desired number of split measurement zones. To prevent ‘crosstalk’, or due to the wiring arrangement of electrical leads, the split measurement zones are separated by an insensitive area.
FIG. 6
shows an example of a known split type photodetector. In
FIG. 6
, the split type photodetector
71
is provided with six split detection areas
73
A through
73
F which are separated by an insensitive band
75
.
Hence, it is impossible to detect the brightness of the object image formed on the insensitive band
75
; if the bright object image is made incident on the insensitive band, the object image cannot be detected, and hence the whole object may be recognized as a dark object.
If the insensitive band
75
is narrow, ‘crosstalk’ tends to occur, thus resulting in a reduced measurement accuracy. Namely, the measurement accuracy is reduced by the insensitive band
75
as the split type photodetector
71
becomes small or the number of the split detection areas is increased.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a multi-measurement or split measurement type photometering apparatus in which an immeasurable area is made as small as possible, or at least reduced.
To achieve the object mentioned above, according to the present invention, there is provided a photometering apparatus having a plurality of photometering systems for measuring the brightness of an object, wherein each photometering system includes:a light receiving device in which different parts of an object are detected by a plurality of split photodetectors whose light receivers each comprise a detection area which is made separate by at least one insensitive area; a photometering optical system for projecting the image of the object onto the light receiving device; wherein the image of the object formed on the at least one insensitive area of one of the plurality of split photodetectors of one of the plurality of photometering systems is formed on the plurality of detection areas of another of the plurality of split photodetectors of another of the plurality of photometering systems.
Preferably, the photometering apparatus includes a pair of photometering systems, wherein the ratios of the vertical and horizontal dimensions of the detection area of the plurality of split photodetectors and at least one insensitive area are the same.
Preferably, the photometering optical system of one of the plurality of photometering systems includes a photometering lens which forms an image on the light receiving portion of the one of the plurality of photometering systems at a different magnification to a photometering lens of the photometering optical system of another of the plurality of photometering systems.
Preferably, the split photodetectors have the same shape and size.
Preferably, the ratios of the vertical and horizontal dimensions of each detection area of the split photodetectors and at least one insensitive area are the same.
Preferably, the magnification of each photometering system is such that substantially all of the image of the object formed on the at least one insensitive area of the split photodetector of one of the plurality of photometering systems is formed on at least one the detection area of the other the split photodetector of another of the plurality of photometering systems.
According to another aspect of the present invention, there is provided a photometering apparatus having a plurality of photometering systems for measuring the brightness of an object, wherein each photometering system includes: a split photodetector having light receiving portions with comprising a detection area which is made separate by an insensitive area; wherein the photometering optical system of one of the plurality of photometering systems comprises a photometering lens which forms an image on the light receiving portion of the one of the plurality of photometering systems at a different magnification to a photometering lens of the photometering optical system of another of the plurality of photometering systems; and wherein the magnification of each photometering system is such that substantially all of the object image formed on the insensitive area of the split photodetector of one of the plurality of photometering systems is formed on at least one detection area of the other the split photodetector of another of the plurality of photometering systems.
Preferably, the split photodetectors have the same shape and size.
Preferably, the photometering apparatus includes a pair of photometering systems, wherein the ratios of the vertical and horizontal dimensions of each the detection area of the split photodetectors and the insensitive areas are the same.
Preferably, the magnification of one of the plurality of photometering systems is less than the magnification of another of the plurality of photometering systems.
Preferably, the photometering apparatus is provided between an image erection system and an eyepiece in a finder optical system of a single lens reflex camera.
According to another aspect of the present invention, there is provided a photometering apparatus, having a plurality of photometering systems for measuring the brightness of an object, wherein each the photometering system comprises: a light receiving device which receives light carrying the object image; and a photometering optical system for projecting the object image onto the light receiving device, the light receiving device receiving object light of different portions of the object; wherein the photometering optical systems have different magnifications.
According to another aspect of the present invention, photometering apparatus including: a pair of split photodetectors for detecting different parts of an object image each of the split photodetectors being provided with a light receiver having detection areas which are separated by an insensitive area; the ratios of the vertical and horizontal dimensions of the insensitive area of one of the pair of split photodetectors and the detection areas of the other of the pair of split photodetectors are the same.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 09-296776 (filed on Oct. 29, 1997) which is expressly incorporated herein by reference in its entirety.
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patent: 5146258 (1992-09-01), Bell et al.
patent: 5434640 (1995-07-01), Takagi et al.
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patent: 5862419 (1999-01-01), Goto et al.
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patent: 0483761 (1992-05-01), None
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Hirai Isamu
Ohkura Tadahisa
Asahi Kogaku Kogyo Kabushiki Kaisha
Font Frank G.
Greenblum & Bernstein P.L.C.
Punnosse Roy M.
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