Wide-angle projection lens for front projection display systems
Assignee3M Innovative Properties Company
InventorKai Chang Lu
Life of this patent
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Abstract
A wide-angle projection lens includes a first lens group of negative refractive power, the first lens group having at least one aspheric surface. The projection lens also includes a second lens group of substantially zero refractive power and a third lens group of positive refractive power. The projection lens satisfies the following three conditions: |F1/F|<4.0 (Condition (1)), |F2/F|>50 (Condition (2)) and |F3/F|<3.5 (Condition (3)). In these conditions, F is the focal length of the wide-angle projection lens; F1 is the focal length of the first lens group; F2 is the focal length of the second lens group; and F3 is the focal length of the third lens group. The wide-angle projection lens is used in a front projection display device.
Claims18
A wide-angle projection lens comprising the following components in sequential order from a screen side:
- (a) a first lens group of negative refractive power, the first lens group having at least one aspheric surface;
- (b) a second lens group of substantially zero refractive power and wherein an aperture stop lies within or near the second lens group;
- and
- (c) a third lens group of positive refractive power;
- wherein the following Conditions (1) to (3) are satisfied:
- |F1/F|<4.0 Condition (1)
- |F2/F|>50 Condition (2)
- |F3/F|<3.5 Condition (3)
- where
- F is the focal length of the wide-angle projection lens;
- F1 is the focal length of the first lens group;
- F2 is the focal length of the second lens group;
- and
- F3 is the focal length of the third lens group
- wherein the wide-angle projection lens is used in a front projection display device.
An optical engine comprising:
- (a) an illumination system;
- (b) an imaging system;
- and
- (c) a projection lens having a back focal length of greater than about twice the effective focal length and a speed of less than or equal to about F/3.1 or less, and
- wherein the projection lens generates an image that has substantially no distortion and requires substantially no keystone correction and wherein the optical engine is part of a projection head in a front projection display device, wherein the projection lens comprises a first lens group, a second lens group, and a third lens group, wherein the first lens group comprises a first and a second lens element, the second lens element including the aspheric surface at its second surface.
An optical engine for a front projection display device, comprising:
- an illumination system, an imaging system, and a wide angle projection lens, wherein the wide angle projection lens includes at least a first lens group of negative refractive power and having at least one aspheric surface, wherein the wide angle projection lens outputs an image at a half field angle of at least about 50°, wherein the image has substantially no distortion, wherein the projection lens comprises a first lens group, a second lens group, and a third lens group, wherein the first lens group comprises a first and a second lens element, the second lens element including the aspheric surface at its second surface.
Dependencies are inferred from the claim text.