Projection lens and projector using the same
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsSyunsuke Kimura, Masayuki Takahashi
Life of this patent
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Abstract
The present invention provides a projection lens for projecting light from a light source onto a screen to form a magnified image, including two joined lenses, each of which includes a negative lens and a positive lens. The difference in the refractive index and the Abbe number between the negative lens and the positive lens in each of the joined lenses and the partial dispersion ratio of the negative lens and the positive lens of the second joined lens are specified. Thus, a large angle of view and a long back focal length can be achieved while satisfying distortion aberrations, telecentric properties and magnification chromatic aberrations.
Claims19
A projection lens for projecting light from a light source onto a screen to form a magnified image, comprising two joined lenses, each of which includes a negative lens and a positive lens, and satisfying the following requirements:
- (1) −0.04<ndI1-ndI2<−0.003
- (2) 13.9<vdI1-vdI2<31
- (3) −0.039<ndII1-ndII2<0.001
- (4) 0.8<vdII1-vdII2<11.5
- (5) −0.033<PgFII1-PgFII2<0.009
- where ndI1 represents a refractive index of the negative lens of the first joined lens;
- ndI2 represents a refractive index of the positive lens of the first joined lens;
- vdI1 represents an Abbe number of the negative lens of the first joined lens;
- vdI2 represents an Abbe number of the positive lens of the first joined lens;
- ndII1 represents a refractive index of the positive lens of the second joined lens;
- ndII2 represents a refractive index of the negative lens of the second joined lens;
- vdII1 represents an Abbe number of the positive lens of the second joined lens;
- vdII2 represents an Abbe number of the negative lens of the second joined lens;
- PgFII1 represents a partial dispersion ratio (ng-nF)/(nF-nC) with respect to a g-line and an F-line of the positive lens of the second joined lens;
- and
- PgFII2 represents a partial dispersion ratio (ng-nF)/(nF-nC) with respect to a g-line and an F-line of the negative lens of the second joined lens.
A projection lens comprising a 1st lens group with a negative power, a 2nd lens group with a weak power, and a 3rd lens group with a positive power in this order from a screen side,
- wherein an aperture stop is provided between the 2nd lens group and the 3rd lens group, and
- the 2nd lens group includes a first lens with a positive power, a second lens with a negative power, and a third lens with a positive power and an aspherical surface in this order from the screen side,
- the first lens of the 2nd lens group and the second lens of the 2nd lens group are joined, and
- the following requirements are satisfied:
- (9) −0.35<f0/fI<0.27
- (10) 0. 01 <f0/fII<0.06
- (11) 0. 35 <f0/fIII<0.38
- where f0 represents a focal length of the entire lens system;
- fI represents a focal length of the 1st lens group;
- fII represents a focal length of the 2nd lens group;
- and
- fIII represents a focal length of the 3rd lens group.
A projection lens comprising a 1st lens group with a negative power, a 2nd lens group with a weak power, and a 3rd lens group with a positive power in this order from a screen side,
- wherein an aperture stop is provided between the 2nd lens group and the 3rd lens group, and
- the 2nd lens group includes a first lens with a negative power, a second lens with a positive power, and a third lens with a positive power and an aspherical surface in this order from the screen side,
- the first lens of the 2nd lens group and the second lens of the 2nd lens group are joined, and
- the following requirements are satisfied:
- (12) −0.35 <f0/fI<−0.27
- (13) 0.01 <f0/fII<0.06
- (14) 0.35 <f0/fIII<0.38
- where f0 represents a focal length of the entire lens system;
- fI represents a focal length of the let lens group;
- fII represents a focal length of the 2nd lens group;
- and
- fIII represents a focal length of the 3rd lens group.
Dependencies are inferred from the claim text.