Zoom lens device with four lens unit
US5859729A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 31, 1996 |
| Grant date | Jan 12, 1999 |
| Priority date | — |
| Expiry date | Dec 31, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B15/144105
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A zoom lens device including a total of four lens units, which are in order of lens units from the lens unit closest to an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having either a positive or negative refractive power, with a stop provided between the second lens unit and the fourth lens unit. The first lens unit comprises two lenses, a positive lens and a negative lens. The second lens unit comprises one or two negative lenses and one positive lens. The third lens unit comprises at least one positive lens and one negative lens. When magnification is being changed from a wide angle end to a telephoto end, the first, third, and fourth lens units are moved toward the object side such that the distance between the first lens unit and second lens unit increases, the distance between the second lens unit and the third lens unit decreases, and the distance between the third lens unit and the fourth lens unit changes. The zoom lens device has a magnification change-over ratio of about 2 to 3.5, a smaller overall length of the lens sy…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.