Projection lens and projector provided with the same
AssigneeSeiko Epson Corporation
InventorShuji Narimatsu
Life of this patent
Estimating the term…
Abstract
A projection lens includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power and including§a first component lens having a negative refractive power and a second component lens having a positive refractive power, and a fourth lens having a positive refractive power. The first, second, third and fourth lens are arranged in that order from a screen side toward an image surface side to form a telecentric system toward the image surface side. A surface on the image surface side of the first lens, and a surface (33) on the image surface side of the second component lens of the third lens are aspherical.
Claims13
A projection lens comprising:
- a first lens having a negative refractive power;
- a second lens having a positive refractive power;
- a third lens having a negative refractive power and comprising a first component lens having a negative refractive power and second component lens having a positive refractive power;
- and
- a fourth lens having a positive refractive power;
- wherein the first, the second, the third and the fourth lens are arranged in that order from a screen side toward an image surface side to form a telecentric system toward the image surface side,
- a surface on the image surface side of the first lens, and a surface on the image surface side of the second component lens of the third lens are aspherical, and
- wherein 0.7<|f1/f2-4|<1.0, where f1 is a focal length of the first lens, and f2-4 is a composite focal length of the second, the third and the fourth lens, and the focal length f1 and the composite focal length f2-4 have opposite signs, respectively.
A projection lens comprising:
- a first lens having a negative refractive power;
- a second lens having a positive refractive power;
- a third lens having a negative refractive power and comprising a first component lens having a negative refractive power and second component lens having a positive refractive power;
- and
- a fourth lens having a positive refractive power;
- wherein the first, the second, the third and the fourth lens are arranged in that order from a screen side toward an image surface side to form a telecentric system toward the image surface side,
- a surface on the image surface side of the first lens, and a surface on the image surface side of the second component lens of the third lens are aspherical;
- and
- wherein 0.8<f2/f4<1.2, where f2 is a focal length of the second lens, and f4 is a focal length of the fourth lens.
A projection lens comprising:
- a first lens having a negative refractive power;
- a second lens having a positive refractive power;
- a third lens having a negative refractive power and comprising a first component lens having a negative refractive power and second component lens having a positive refractive power;
- and
- a fourth lens having a positive refractive power;
- wherein the first, the second, the third and the fourth lens are arranged in that order from a screen side toward an image surface side to form a telecentric system toward the image surface side,
- a surface on the image surface side of the first lens, and a surface on the image surface side of the second component lens of the third lens are aspherical;
- and
- wherein the aspherical surface on the image surface side of the first lens is expressed by:
- x = Ry 2 1 + 1 - ( 1 + K ) R 2 y 2 + Ay 4 + By 6 + Cy 8 + Dy 10
- where A, B, C and D are predetermined fixed values, and R meets 0.5 <R/f< 1.0, where f is the focal length of the projection lens.
Dependencies are inferred from the claim text.