US 7,623,308 B2Granted

Rear projection lens device and magnification adjusting method thereof

AssigneeFujinon Corporation

InventorTomonari Masuzawa

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Abstract

The rear projection lens device comprises a fixed lens barrel, a first lens barrel having a front lens group, a second lens barrel having a rear lens group, and a rotation stopper. The first lens barrel is helicoid-coupled with the fixed lens barrel, and moves in an optical axial direction by rotating relative to the fixed lens barrel. The second lens barrel is helicoid-coupled with the first lens barrel and moves in the optical axial direction so as to change an interval between the front lens group and the rear lens group when the first lens barrel rotates. The rotation stopper allows the second lens barrel to move in the optical axial direction, but stops the rotation around the optical axis. A zoom adjustment and aberration correction associated with the zoom adjustment are conducted concurrently only by rotating the first lens barrel.

Claims4

Dependent claims

A rear projection device for projecting image light to a screen from behind said screen, said rear projection device comprising:

(a) a front lens group;
(b) a rear lens group disposed behind said front lens group;
(c) a first lens barrel for retaining said front lens group;
(d) a second lens barrel for retaining said rear lens group;
(e) a third lens barrel for rotatably accommodating said second lens barrel, said third lens barrel not being rotated;
(f) a first moving mechanism for moving said front lens group in an optical axial direction when said first lens barrel being rotated, said first moving mechanism including a first female helicoid disposed on an inner circumference of said third lens barrel and a first male helicoid disposed on an outer circumference of said first lens barrel to engage with said first female helicoid;
(g) a second moving mechanism for moving said rear lens group in said optical axial direction when said first lens barrel being rotated, said second moving mechanism including a second female helicoid disposed on an inner circumference of said first lens barrel and a second male helicoid disposed on an outer circumference of said second lens barrel to engage with said second female helicoid;
and
(h) a rotation stopper mechanism for linearly moving said second lens barrel in said optical axial direction without rotating said second lens barrel when said first lens barrel being rotated.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/063,987Filed 24 Feb 2005
Priority: JP 2004-0565821 Mar 2004
Published: US 2005/0190464 A11 Sep 2005
Granted: 24 Nov 2009
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G02B 7/10
With mechanism for focusing or varying magnification: by relative axial movement of several lenses, e.g. of varifocal objective lens
G02B 15/142
By axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of…:…
G02B
Optical elements, systems or apparatus