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Projecting zoom lens

A zoom lens and projection technology, applied in the field of projection zoom lens, can solve the problem that the telecentric zoom lens cannot be reduced satisfactorily

Inactive Publication Date: 2005-09-21
SEIKO EPSON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] However, since the aspheric mirror is provided on the exit side or the entrance side in the existing telecentric zoom lens, the purpose of the design of the telecentric zoom lens is mainly to reduce only distortion, and thus the telecentric zoom lens cannot satisfactorily reduce other Aberration

Method used

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Embodiment Construction

[0048] Figures 1, 7 and 13 represent the wide-angle range set at the wide-angle magnification range ((a)), the standard range set at the standard magnification range ((b)), and the telephoto range set at the telephoto magnification range ((c) ) First, second and third embodiments of the projection zoom lens 2.

[0049] As shown in FIG. 13, the projection zoom lens 2 includes four lens groups, namely, a first lens group with a negative refractive ratio, a second lens group 20 with a positive refractive ratio, a third lens group 30 with a negative refractive ratio, and The fourth lens group 40 having a positive refractive ratio; they are arranged in order from the screen side (left side as shown in FIG. 1 ) to the image plane side (right side as shown in FIG. 1 ). The projection zoom lens 2 is set in the projector. The projector includes an imaging device. The imaging unit has 3 liquid crystal displays. The three images formed by the three liquid crystal displays are combined...

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Abstract

A projection zoom lens includes a first lens group having a negative refracting power, a second lens group having a positive refracting power, a third lens group having a negative refracting power, and a fourth lens group having a positive refracting power, which are arranged in that order from a screen side toward an image plane side along an optical axis. The first and the fourth lens group are kept stationary, and the second and the third lens group are moved along the optical axis to vary power from a limit wide angle power toward a limit telephoto power. The second lens group includes a 2nd-group 1st positive lens, a 2nd-group 1st compound lens formed by joining a 2nd-group 2nd positive lens having a convex surface on the image plane side and a 2nd-group 1st negative lens having a concave surface on the screen side, and a 2nd-group 3rd positive lens arranged in that order from the screen side toward the image plane side. The third lens group includes a 3rd-group 1st meniscus lens having a concave surface on the image plane, a 3rd-group 1st compound lens formed by joining a 3rd-group 1st negative lens having opposite concave surfaces and a 3rd-group 1st positive lens having opposite convex surfaces, and a 3rd-group 2nd meniscus lens having a convex surface on the image plane side arranged in that order from the screen side toward the image plane side. The first lens group has a focal length f1, the 2nd-group 1st positive lens and the 2nd-group 1st compound lens have a composite focal length f2AB of a sign opposite to that of the focal length f1, and the focal length f1 and the composite focal length f2AB meet an inequality: 0.5<|f1 / f2AB|<2.0.

Description

technical field [0001] The invention relates to a projection zoom lens suitable for use on a projector, and the lens is used to project images formed on film, slides or liquid crystal displays on a screen as enlarged pictures. Background technique [0002] Most projectors for projecting images formed on film, slides, or liquid crystal displays on a screen as enlarged pictures have projection optical systems using telecentric zoom lenses. [0003] Most telecentric zoom lenses such as those disclosed in Japanese Patent Publication Nos. JP137165 / 2000, 186235 / 1998, 206409 / 2000, 019400 / 2000, 190821 / 1999, 168193 / 1998, 243917 / 1999 and 231219 / 1999, When the maximum opening angle is set, it has a half field angle of about 25°. [0004] With a half field angle of 30°, such as the telecentric zoom lens disclosed in JP206409 / 2000, an aspheric mirror is used as the larger lens of the first lens group or the last lens group to reduce the spherical aberration caused by increasing the fiel...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G02B15/167G02B13/16G02B13/18G02B13/22G02B15/177G02B15/20
CPCG02B15/177G02B13/22G02B13/16G02B15/144511G02B3/0062G02B3/0087G02B3/04G02B2003/0093G03B21/142
Inventor 成松修司
Owner SEIKO EPSON CORP