Zoom lens device with inner focusing method

Details Zoom lens device with inner focusing method Zoom lens device with inner focusing method

1996-06-17

1998-04-07

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359684, 359687, 359688, G02B 1514

Patent

active

057371288

ABSTRACT:
A zoom lens device including in order of lens units from the lens unit closest to an object side of the zoom lens device to an image side of the zoom lens device, a first lens unit having a positive refractive power, a second lens unit for changing magnification and having a negative refractive power, a third lens unit for correcting changes in an image plane which occur as the magnification changes, and a fourth lens unit for forming an image. The first lens unit includes (i) a front lens subunit which is stationary during focusing and which has a positive refractive power and (ii) a rear lens subunit which is movable in order to bring an object into focus. The front lens subunit includes a negative lens and a positive lens. The rear lens subunit includes a negative lens and at least two positive lenses.

REFERENCES:
patent: 4099845 (1978-07-01), Takesi et al.
patent: 4110006 (1978-08-01), Ikemori
patent: 4113356 (1978-09-01), Matsubara
patent: 4752121 (1988-06-01), Kitagishi
patent: 4848883 (1989-07-01), Maruyama

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