Fast focusing method for digital camera
US8259217B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 21, 2010 |
| Grant date | Sep 4, 2012 |
| Priority date | — |
| Expiry date | May 14, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N23/673
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A fast focusing method for a digital camera is applied in an auto focusing stage for judging whether the digital camera needs to be refocused. The fast focusing method includes recording a system time after a previous focusing (defined as a first time); capturing a system time before a current focusing (defined as a second time); performing a fuzziness detection procedure to acquire a focus value when a difference obtained by subtracting the first time from the second time is greater than a focusing time threshold; setting a focusing focal length range covering a reference focal length when the focus value is between a lower limit focusing threshold and an upper limit focusing threshold; capturing images at different focusing focal lengths respectively in the focusing focal length range; calculating a contrast value of each image; calculating a target focal length from the contrast values through a quadratic curve approximation method.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.