Automatic focus device and method
US5625434A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 21, 1995 |
| Grant date | Apr 29, 1997 |
| Priority date | — |
| Expiry date | Apr 21, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/36
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An automatic focusing device drives a focusing lens so as to follow the actual movement of the subject image-forming plane. The automatic focus device has a shooting lens, a camera body, and a CPU in the camera body that computes a defocus amount by conducting focus state detections at a set time intervals. In addition, the CPU reads, via lens connections, the lens movement amount detected by a drive monitor unit in the shooting lens. Furthermore, image plane velocities are computed at set time intervals using the defocus amount and lens movement amount. A determination is made as to whether the computed image plane velocities are suitable for prediction computations, and when the determination is that the velocities are suitable, the hypothetical time t.sub.n-1 corresponding to the previous image plane velocity computation time is found. Next, after the expected exposure time tr is changed to the hypothetical exposure time tx, the image plane velocity V.sub.im at the estimated exposure time is found by substituting this hypothetical exposure time tx into a hyperbolic equation, and the shooting lens is then driven on the basis of this image plane velocity.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.