US 4,908,643 AGranted

Automatic focussing adjusting device

AssigneeFuji Photo Film Co., Ltd.

InventorsKazukiyo Tamada, Naoki Takatori, Tsuneo Yokoyama, Satoshi Mikajiri, Mineo Kubota, Hiroshi Saito

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Abstract

An automatic focussing adjusting device which detects the amount of de-focussing of an image of an object to perform an automatic focussing adjustment of a taking lens of a camera including a zoom lens. The magnification m of a group of magnification varying lenses in the zoom lens is corrected and the amount of movement .DELTA.X of a group of focus lenses necessary for focussing is calculated based on a corrected magnification .alpha..multidot.m, so that a focussing adjustment can be executed. Also, an error in the amount of de-focussing, caused by manufacturing errors in dimensions defining a positional relationship between line sensors and a group of microscopic lenses in a focus detect element is corrected, and based on a correctively calculated amount of de-focussing .beta..multidot..DELTA.P, a focussing adjustment is performed.

Claims17

Dependent claims

An automatic focussing adjusting device comprising:

focus detect means for detecting the state of forming of an image of an object on the focal plane which is formed by the incident light of a zoom lens;
lens drive means for driving a group of focus lenses in said zoom lens;
and control means for calculating an amount of de-focussing .DELTA.P in accordance with the detect output of said focus detect means, for finding the amount of movement .DELTA.X of said focus lens group necessary for focussing on said focal plane according to said amount of de-focussing .DELTA.P, the magnification m of a group of magnification varying lenses in said zoom lens and the focal distance thereof fe, and for outputting to said lens drive means a control signal to move said focus lens group by said amount of movement .DELTA.X, said control means further including correction coefficient setting means for setting a correction coefficient .alpha. for the magnification m of said magnification varying lens group, said control means generating and using the factor .alpha..multidot.m in place of the magnification m of said magnification varying lens group for calculating said control signal to move said focus line group by said amount of movement .DELTA.X.

An automatic focussing adjusting device comprising:

two line sensors for outputting the electric signals that correspond to the illumination distributions of an image of an object formed on the light receiving surfaces thereof;
a group of microscopic lenses for forming the image of said object on said two line sensors, said object image being formed by the light that has passed through two portions symmetric with respect to an optic axis on the exit pupil surface of a taking lens;
and control means for converting the amount of shift between the illumination distributions of said object image on said light receiving surfaces of said two line sensors to an amount of de-focussing with respect to the focal plane of said taking lens, and for performing a focus control operation in accordance with said amount of de-focussing, said control means further including correction coefficient setting means for setting a correction coefficient .beta. to correct the error in said amount of defocussing that is caused by the variations of dimensions defining a mutual positional relationship between said microscopic lens group and said two line sensors, said control means utilizing said correction coefficient to perform a focus control operation in accordance with said corrected amount of de-focussing.

An automatic focussing adjusting device comprising:

focus detect means including a group of light receiving elements arranged linearly at given intervals and a group of microscopic lenses disposed in front of said light receiving elements and spaced by fixed distances from said light receiving elements in a direction of the optic axis of an optical system for focus adjustment for detecting the state of an image of an object on a focal plane which is formed by the incident light of a zoom lens;
lens drive means for driving a group of focus lenses in said zoom lens;
and control means for calculating an amount of de-focussing .DELTA.P in accordance with the detect output of said focus detect means, for finding the amount of movement .DELTA.X of said focus lens group necessary for focussing on said focal plane according to said amount of de-focussing .DELTA.P, the magnification m of a group of magnification varying lenses in said zoom lens and the focal distance fe thereof, and for outputting to said lens drive means a control signal to move said focus lens group by said amount of movement .DELTA.X, said control means further including a first correction coefficient setting means for setting a correction coefficient .gamma. for the magnification m of said magnification varying lens group, and a second correction coefficient setting means for setting a correction coefficient to correctively eliminate the influence of an error in said amount of de-focussing .DELTA.P on said amount of movement .DELTA.X, said error being caused by error in the magnification m of said magnification varying lens group and by manufacturing errors in dimensions defining a positional relationship between said light receiving element group and said microscopic lens group in said focus detect means, said control means performing a correction operation in response to said correction coefficients .alpha. and .gamma. to thereby compensate for the amount of movement .DELTA.P of said focus lens group.

An automatic focussing adjusting device comprising:

focus detecting means including a group of light receiving elements arranged linearly at given intervals and a group of microscopic lenses disposed in front of said light receiving elements and spaced by fixed distances from said light receiving elements in a direction of the optic axis of an optical system for focus adjustment for detecting the state of an image of an object on a focal plane which is formed by the incident light on a zoom lens;
lens driving means for driving a group of focus lenses in said zoom lens;
and control means for calculating an amount of de-focussing .DELTA.P in accordance with the detect output of said focus detect means, for finding the amount of movement .DELTA.X of said focus lens group necessary for focussing on said focal plane according to said amount of de-focussing .DELTA.P, the magnification m of a group of magnification varying lenses in said zoom lens and the focal distance fe thereof, and for outputting to said lens drive means a control signal to move said focus lens group by said amount of movement .DELTA.X;
said control means further including correction coefficient setting means for setting a correction coefficient .delta. to correctively remove the influence of an error in said amount of de-focussing .DELTA.P on said amount of movement .DELTA.X, said error being caused by an error in the magnification m of said magnification varying lens group and by manufacturing errors in dimensions defining a positional relationship between said light receiving element group and said microscopic lens group in said focus detect means, said control means performing a correction operation in response to said correction coefficient to compensate for the amount of movement .DELTA.X of said focus lens group.

1 more element

Dependencies are inferred from the claim text.