Projection lens and image display device

• US 6,130,786 A
• Filed: 06/28/1999
• Issued: 10/10/2000
• Est. Priority Date: 05/25/1993
• Status: Expired due to Term

• Current Assignee: Hitachi Consumer Electronics Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Yoshikawa, Hiroki, Ogura, Naoyuki, Mori, Shigeru, Osawa, Atsuo
• Primary Examiner(s): Sugarman, Scott J.
• Assistant Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US09/340,141
• Time in Patent Office: 470 Days
• Field of Search: 359/649, 359/650, 359/651, 359/714
• US Class Current: 359/649
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 13/24 for reproducing or copying at short object distances
• CPC Class Codes: G02B 9/60 having five components only

Abstract

An image display device which is compact on the whole and low in cost, and which uses a plurality of projection lens systems each of which is constituted by five lens groups including a first aspherical lens group, a second aspherical lens group, a third biconvex lens group, a fourth aspherical lens group and a fifth aspherical lens group which are arranged in this order successively from a screen side, the third lens group having refractive power of not lower than 70% of the total power of the projection lens system, the respective peripheral shapes of the first and second aspherical lens groups being set to have a predetermined relation, a low-dispersion high-index glass material being used for a convex lens of a green projection lens system, a high-dispersion high-index glass material being used for convex lenses of blue and red projection lens systems.

Claims

1. A rear projection type image displaying apparatus comprising:

a projection tube for outputting an image light;

a projection lens system for enlarging the image light outputted from the projection tube and projecting the image light;

a mirror for reflecting the image light projected from the projection lens system; and

a screen for receiving the image light reflected by the mirror and displaying an image corresponding to the image light at a front side of the apparatus;

wherein the projection lens system comprises;

a first meniscus lens being concave toward the screen and disposed at a nearest position to an image displaying device and having a smallest amount of power among elements forming the projection lens system;

a first aspherical lens made of plastic material and having the center of curvature at the center portion including the axis of the lens surface at the image displaying device side being positioned toward the screen side;

a biconvex lens made of a glass material having a positive power not lower than 70% of a total power of the projection lens system;

a second aspherical lens; and

a second meniscus lens disposed at the nearest position to the screen, and having a positive power with a convex surface toward the screen for effecting a light collecting function at the center portion including the axis and dispersing function at the peripheral portion apart from the axis in the radius direction;

wherein the displaying surface of the image displaying device is curved in a circular arc having a center of curvature toward the screen; and

wherein a distance d between the surface of the first meniscus lens toward the screen and the displaying surface of the image displaying device is set as d/f₀ ≧

0.35 where f₀ is focal length of the projection lens system.

2. A rear projection type image displaying apparatus comprising:

a projection tube for outputting an image light;

a projection lens system for enlarging the image light from the projection tube and projecting the enlarged image light;

a mirror for reflecting the image light projected from the projection lens system; and

a screen for receiving the image light reflected by the mirror and displaying the image corresponding to the image light at the front side of the apparatus;

the projection lens system comprising;

a first meniscus lens being concave toward the screen and disposed at the nearest position to an image displaying device among the lens elements, and having a smallest amount of power among the projection lens system, the surface at the image displaying device being coupled with a cooling liquid for cooling the image display, and further a lens group having a most negative power in the projection lens system being formed by said first meniscus lens, said cooling liquid and the surface of said image displaying device;

a converging lens having a highest positive power of all of the lens elements is made of glass material; and

a second meniscus lens disposed at a nearest position to the screen, and having a positive power with a convex surface toward the screen for effecting a light collecting function at the center portion including the axis and dispersing function at the peripheral portion apart from the axis in the radius direction;

wherein the displaying surface of the image displaying device is curved in a circular arc having a center of curvature toward the screen; and

wherein a distance d between the surface of the first meniscus lens toward the screen and the displaying surface of the image displaying device is set as d/f₀ ≧

0.35 where f₀ is focal length of the projection lens system.

3. A rear projection type image displaying apparatus comprising:

a projection tube for outputting an image light;

a projection lens system for enlarging the image light from the projection tube and projecting it;

a mirror for reflecting the image light projected from the projection lens system; and

a screen which is projected the image light reflected by the the mirror and displaying the image corresponding to the image light at the front side of the apparatus;

the projection lens system comprising;

a first aspherical lens having a positive power and being a convex meniscus lens toward the screen side at the nearest position to the screen, for effecting a light collecting function at the center portion including the axis and dispersing function at the peripheral portion apart from the axis in the radius direction;

a second lens made of plastic material with the center of curvature at the center portion including the axis of the lens surface at the image displaying device side being positioned toward the screen side;

a third lens with biconvex lens shape made of a glass material having a positive power not lower than 70% of a total power of the projection lens system;

a fourth lens having a meniscus shape being convex toward the screen side; and

a fifth lens having a meniscus shape being concave toward the screen side and disposed at the nearest to said image displaying device, and said fifth lens being coupled with said cooling liquid for cooling said image displaying device, and further a lens group having a most negative power in the projection lens system being formed by said fifth lens, said cooling liquid and the displaying surface of said image displaying device;

wherein the displaying surface of the image displaying device is curved in a circular arc having a center of curvature toward the screen; and

wherein a distance d between the surface of the first meniscus lens toward the screen and the displaying surface of the image displaying device is set as d/f₀ ≧

0.35 where f₀ is focal length of the projection lens system.

4. A rear projection type image displaying apparatus according to claim 3, wherein the second lens has an abbe number (VD) of not larger than 50.