Automatic focusing device
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorYukio Uenaka
Life of this patent
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Abstract
An automatic focusing device, in which a focus lens is driven for tracking an object-in-motion so as to obtain an in-focus state, based upon a focus prediction that is executed from repeated distance measurements. Tracking is executed with different algorithms according to a moving direction of the object-in-motion. One algorithm is a catch-up tracking, wherein the focus lens is driven to a position where it is predicted that the in-focus state should be obtained at the time of completion of the lens drive. Another algorithm is a preemptive tracking, wherein the focus lens is driven to a position where it is predicted that the in-focus condition should be obtained at the time an exposure is actually executed after a completion of the lens drive.
Claims32
An automatic focusing device, comprising:
- a focus lens that is movable along an optical axis thereof;
- drive means for driving said focus lens;
- distance measuring means for obtaining a defocus amount of said lens;
- detecting means for determining the relative direction of movement of an object with respect to said focus lens from at least two relative directions, along said optical axis, based upon defocus amounts obtained by said distance measuring means;
- and
- drive control means for controlling said drive means to drive said focus lens, based upon the relative direction determined by said detecting means, to a position where an in-focus condition is obtained with respect to said object after elapse of a predetermined time,
- wherein said drive control means comprises means for determining a drive amount of said focus lens using different algorithms selected in accordance with said relative direction of movement of said object determined by said detecting means, wherein only one of said algorithms uses a factor related to release time lag.
An automatic focusing device, comprising:
- means for detecting the relative direction of movement of an object with respect to said automatic focusing device from at least two relative directions;
- and
- means for controlling focusing of a lens associated with said automatic focusing device in response to said detecting means, so as to obtain an in-focus condition of said object with respect to said automatic focusing device, said focusing control means comprising means for controlling said focusing of said lens based upon an algorithm that is selected for use from a plurality of algorithms in accordance with said computed relative direction of movement of said object, wherein only one of said algorithms uses a factor related to release time lag.
A method for automatically focusing upon an object, comprising the steps of:
- obtaining a defocus amount of a lens that focuses upon the object, wherein a distance between the lens and the object is changeable;
- determining the relative direction of movement of the object with respect to the focus lens from at least two relative directions, based upon the obtained defocus amount;
- and
- controlling focusing of the lens based upon the determined relative direction of movement of the object, so as to obtain an in-focus condition of the object, the control of focusing of the lens being based upon an algorithm that is selected for use from a plurality of algorithms in accordance with the computed relative direction of movement of the object, wherein only one of said algorithms uses a factor related to release time lag.
Dependencies are inferred from the claim text.