Focal point detection apparatus, focusing system, camera, and focal point detection method
US6973264B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Sep 26, 2002 |
| Grant date | Dec 6, 2005 |
| Priority date | — |
| Expiry date | Sep 26, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B7/38
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
First to third liquid crystal filters are arranged at first to third different distances from a predeterminate image formation surface. Light flux passing through the liquid crystal filters is received by a photodiode and converted into an electric signal. A variable-density stripe pattern of a predetermined space frequency is formed on the first liquid crystal filter while the second and the third liquid crystal filter are in the state of entire transparency and a first signal is output from the photodiode. Similarly, a variable-density stripe pattern is formed on the second liquid crystal filter while the first and the third liquid crystal filter are in the state of entire transparency and a second signal is output. Similarly, a variable-density stripe pattern is formed on the third liquid crystal filter while the first and the second liquid crystal filter are in the state of entire transparency and a third signal is output. According to the first, second, and third signals, a focal point position is calculated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.