Automatic focus adjustment apparatus
AssigneeNikon Corporation
InventorAkira Ogasawara
Life of this patent
Estimating the term…
Abstract
An automatic focus adjustment apparatus more ideally accomplishes a tracking servo process, which drives a shooting lens so that a focusing state is maintained by predicting movements of an image plane of a moving object. A lens driving system 6 determines the moving speed of an image plane of an object or a movement prediction curve by regression-calculating from a plurality of defocus amounts previously calculated, a calculator, the accumulation time of a focusing state detector, and a lens position obtained from a lens movement amount detector, to drive a lens by assuming a future position of the image plane based on a result of the calculation.
Claims8
An automatic focus adjustment apparatus, comprising:
- having a focusing state detector having a charge accumulating type sensor;
- a calculator that processes output data from said focusing state detector to calculate a defocus amount from a focusing position;
- and
- a driver that drives a shooting lens to a said focusing position in accordance with a movement prediction curve based on said the defocus amount calculated by said calculator, wherein said driver determines said movement prediction curve by a regression calculation, said regression calculation estimates said focusing position by a movement function Qr(t) of an image plane based on a plurality of past data detected during a predetermined time, said movement function Qr(t) is defined by an equation
- Qr(t)=.alpha.+.beta.t where
- .beta.={.SIGMA.t(k).cndot.F(k)-nt.sub.ave .cndot.F.sub.ave }/{.SIGMA.t(k).sup.2)-nt.sub.ave.sup.2 } and
- .alpha.={.SIGMA.D(k)-.beta..cndot.n.cndot.t.sub.ave }/n, t(k)
- being an accumulated time of a sensor, F(k) being a focusing point, t.sub.ave being an average time of said accumulated time of said sensor and F.sub.ave being an average position of said focusing point.
A method for automatic focusing, comprising:
- detecting a focusing state using a charge accumulating type sensor;
- processing output data detected from said focusing state to calculate a defocus amount from a focusing position;
- and
- driving a shooting lens to said focusing position in accordance with a movement prediction curve based on said calculated defocus amount wherein driving said shooting lens determines said movement prediction curve by a regression calculation, said regression calculation estimates said focusing position by a movement function Qr(t) of an image plane based on a plurality of past data detected during a predetermined time, said movement function Qr(t) is defined by an equation
- Qr(t)=.alpha.+.beta.t
- where
- .beta.={.SIGMA.t(k).cndot.F(k)-nt.sub.ave .cndot.F.sub.ave }/{.SIGMA.t(k).sup.2 -nt.sub.ave.sup.2 } and
- .alpha.={.SIGMA.D(k)-.beta..cndot.n.cndot.t.sub.ave }/n, t(k)
- being an accumulated time of a sensor, F(k)being a focusing point, t.sub.ave being an average time of said accumulated time of said sensor and F.sub.ave being an average position of said focusing point.
Dependencies are inferred from the claim text.