Focusable front projection lens systems for use with large screen formats
First Claim
1. A variable focus, front projection, lens system for forming an image on a screen which has a diagonal greater than 1.5 meters, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a first lens unit which primarily corrects aperture dependent aberrations, said first lens unit having an optical power Φ
1 and comprising at least one aspherical surface;
(b) a second lens unit having an optical power Φ
2 and comprising in order from the system'"'"'s image side;
a negative, biconcave, first lens element composed of glass;
a positive, biconvex, second lens element composed of glass;
a positive, biconvex, third lens element composed of glass; and
a fourth lens element which comprises at least one aspherical surface and is composed of plastic;
(c) a corrector lens unit having an optical power Φ
CR and comprising at least one aspherical surface; and
(d) a third lens unit which provides correction for the field curvature of the lens system, said third lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system and which has two surfaces both of which are concave to the image, said third lens unit and said coupling fluid having an optical power Φ
3 ;
wherein(i) Φ
1 >
0;
(ii) Φ
2 /Φ
>
0.7;
(iii) Φ
CR <
0;
(iv) Φ
3 <
0;
(v) the corrector lens unit and the third lens unit are separated by a distance DCR/3 which is varied during focusing of the image on the screen, said focusing being able to accommodate a range of screen diagonals of at least 1.5;
1; and
(vi) said lens system and coupling fluid have a modulation transfer function at the cathode ray tube which varies over said range of screen diagonals such that the ratio RMin/Max of the minimum value of the modulation transfer function at 5 cycles/millimeter to the maximum value of the modulation transfer function at 5 cycles/millimeter over said range of screen diagonals for any field position up to 0.85 of the maximum field is greater than 0.5.
2 Assignments
0 Petitions
Accused Products
Abstract
Variable focus, liquid coupled, front projection, lens systems (13) are provided for use with large screens (14), e.g., screens having a full diagonal of 1.5 meters and above. The lens systems (13) can be focused over a range of screen diagonals of at least 1.5:1 while maintaining a high level of performance as evidenced by relatively small changes in the lens system'"'"'s modulation transfer function (MTF) as it is focused. The lens systems can include four lens units, namely, a positive first lens unit having a positive subunit and a negative subunit, a positive second lens unit having four lens elements at least one of which is negative, a negative corrector lens unit having an aspherical lens element, and a third lens unit which is liquid coupled to a cathode ray tube (16) during use.
94 Citations
41 Claims
-
1. A variable focus, front projection, lens system for forming an image on a screen which has a diagonal greater than 1.5 meters, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a first lens unit which primarily corrects aperture dependent aberrations, said first lens unit having an optical power Φ
1 and comprising at least one aspherical surface;(b) a second lens unit having an optical power Φ
2 and comprising in order from the system'"'"'s image side;a negative, biconcave, first lens element composed of glass; a positive, biconvex, second lens element composed of glass; a positive, biconvex, third lens element composed of glass; and a fourth lens element which comprises at least one aspherical surface and is composed of plastic; (c) a corrector lens unit having an optical power Φ
CR and comprising at least one aspherical surface; and(d) a third lens unit which provides correction for the field curvature of the lens system, said third lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system and which has two surfaces both of which are concave to the image, said third lens unit and said coupling fluid having an optical power Φ
3 ;wherein (i) Φ
1 >
0;(ii) Φ
2 /Φ
>
0.7;(iii) Φ
CR <
0;(iv) Φ
3 <
0;(v) the corrector lens unit and the third lens unit are separated by a distance DCR/3 which is varied during focusing of the image on the screen, said focusing being able to accommodate a range of screen diagonals of at least 1.5;
1; and(vi) said lens system and coupling fluid have a modulation transfer function at the cathode ray tube which varies over said range of screen diagonals such that the ratio RMin/Max of the minimum value of the modulation transfer function at 5 cycles/millimeter to the maximum value of the modulation transfer function at 5 cycles/millimeter over said range of screen diagonals for any field position up to 0.85 of the maximum field is greater than 0.5. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- , said system comprising in order from the system'"'"'s image side;
-
14. A variable focus, front projection, lens system for forming an image on a screen which has a diagonal greater than 1.5 meters, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a first lens unit which primarily corrects aperture dependent aberrations, said first lens unit having an optical power Φ
1 and comprising a first subunit having an optical power Φ
S1 and a second subunit having an optical power Φ
S2, each of said subunits having at least one aspherical surface;(b) a second lens unit having an optical power Φ
2 and comprising in order from the system'"'"'s image side;a negative first lens element composed of glass; a positive second lens element composed of glass; a positive third lens element composed of glass; and a fourth lens element which comprises at least one aspherical surface; (c) a corrector lens unit having an optical power Φ
CR and comprising a plastic lens element both of whose surfaces have an overall shape which is concave to the image and at least one of whose surfaces is aspherical; and(d) a third lens unit which provides correction for the field curvature of the lens system, said third lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system and which has two surfaces both of which are concave to the image, said third lens unit and said coupling fluid having an optical power Φ
3 ;wherein (i) Φ
1 >
0;(ii) Φ
S1 >
0;(iii) Φ
S2 <
0;(iv) Φ
2 /Φ
>
0.7;(v) Φ
CR <
0;(vi) Φ
3 <
0;(vii) the corrector lens unit and the third lens unit are separated by a distance DCR/3 which is varied during focusing of the image on the screen, said focusing being able to accommodate a range of screen diagonals of at least 1.5;
1; and(viii) said lens system and coupling fluid have a modulation transfer function at the cathode ray tube which varies over said range of screen diagonals such that the ratio RMin/Max of the minimum value of the modulation transfer function at 5 cycles/millimeter to the maximum value of the modulation transfer function at 5 cycles/millimeter over said range of screen diagonals for any field position up to 0.85 of the maximum field is greater than 0.5. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
- , said system comprising in order from the system'"'"'s image side;
-
25. A projection lens system for forming an image on a screen, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a lens element of optical power Φ
A which is composed of plastic and has at least one aspherical surface;(b) a lens element of optical power Φ
B which is composed of plastic and has at least one aspherical surface;(c) a lens element of optical power Φ
C which is composed of glass;(d) a lens element of optical power Φ
D which is composed of glass and is biconvex;(e) a lens element of optical power Φ
E which is composed of glass and is biconvex;(f) a lens element of optical power Φ
F which is composed of plastic and has at least one aspherical surface;(g) a lens element of optical power Φ
G which is composed of plastic, the surfaces of said lens element each having an overall shape which is concave to the image and at least one of said surfaces being aspherical; and(h) a lens unit which provides correction for the field curvature of the lens system, said lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system, is composed of plastic, and has two surfaces both of which are concave to the image and at least one of which is aspherical, said lens unit and said coupling fluid having an optical power Φ
H ;wherein (i) Φ
A, Φ
D, and Φ
E are each>
0;(ii) Φ
B, Φ
C, Φ
G, and Φ
H are each<
0;(iii) Φ
A /Φ
>
0.4;(iv) |Φ
B |/Φ
<
0.4; and(v) |Φ
F |/Φ
<
0.2;and wherein the lens element having an optical power Φ
G and the lens unit are separated by a distance which is varied during focusing of the image on the screen. - View Dependent Claims (26, 27, 28, 29, 30, 31)
- , said system comprising in order from the system'"'"'s image side;
-
32. A variable focus, front projection, lens system for forming an image on a screen which has a diagonal greater than 1.5 meters, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a first lens unit which primarily corrects aperture dependent aberrations, said first lens unit having an optical power Φ
1 and comprising at least one aspherical surface;(b) a second lens unit having an optical power Φ
2 and comprising in order from the system'"'"'s image side;a negative first lens element composed of glass; a positive second lens element composed of glass; a positive third lens element composed of glass; and a fourth lens element which comprises at least one aspherical surface and has an optical power Φ
E4 ;(c) a corrector lens unit having an optical power Φ
CR and comprising at least one aspherical surface; and(d) a third lens unit which provides correction for the field curvature of the lens system, said third lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system and which has two surfaces both of which are concave to the image, said third lens unit and said coupling fluid having an optical power Φ
3 ;wherein (i) Φ
1 >
0;(ii) Φ
2 /Φ
>
0.7;(iii) Φ
CR <
0;(iv) Φ
3 <
0;(v) |Φ
E4 |/Φ
<
0.2;(vi) the corrector lens unit and the third lens unit are separated by a distance DCR/3 which is varied during focusing of the image on the screen, said focusing being able to accommodate a range of screen diagonals of at least 1.5;
1; and(vii) said lens system and coupling fluid have a modulation transfer function at the cathode ray tube which varies over said range of screen diagonals such that the ratio RMin/Max of the minimum value of the modulation transfer function at 5 cycles/millimeter to the maximum value of the modulation transfer function at 5 cycles/millimeter over said range of screen diagonals for any field position up to 0.85 of the maximum field is greater than 0.5. - View Dependent Claims (33, 34)
- , said system comprising in order from the system'"'"'s image side;
-
35. A variable focus, front projection, lens system for forming an image on a screen which has a diagonal greater than 1.5 meters, said system being optically coupled to a cathode ray tube by a coupling fluid during use, said system and said coupling fluid having an optical power Φ
- , said system comprising in order from the system'"'"'s image side;
(a) a first lens unit which primarily corrects aperture dependent aberrations, said first lens unit having an optical power Φ
1 and comprising in order from the system'"'"'s image side;a first subunit having an optical power Φ
S1 ; anda second subunit having an optical power Φ
S2 ;
where at least one of said first and second subunits comprises an aspherical surface and where;
space="preserve" listing-type="equation">Φ
.sub.S1 >
0; and
space="preserve" listing-type="equation">Φ
.sub.S2 <
0;(b) a second lens unit having an optical power Φ
2 and comprising at least one aspherical surface;(c) a corrector lens unit having an optical power Φ
CR and comprising at least one aspherical surface; and(d) a third lens unit which provides correction for the field curvature of the lens system, said third lens unit comprising a lens element which is in contact with said coupling fluid during use of the lens system and which has two surfaces both of which are concave to the image, said third lens unit and said coupling fluid having an optical power Φ
3;wherein (i) Φ
1 >
0;(ii) Φ
2 /Φ
>
0.7;(iii) Φ
CR <
0;(iv) Φ
3 <
0;(v) the corrector lens unit and the third lens unit are separated by a distance DCR/3 which is varied during focusing of the image on the screen, said focusing being able to accommodate a range of screen diagonals of at least 1.5;
1; and(vi) said lens system and coupling fluid have a modulation transfer function at the cathode ray tube which varies over said range of screen diagonals such that the ratio RMin/Max of the minimum value of the modulation transfer function at 5 cycles/millimeter to the maximum value of the modulation transfer function at 5 cycles/millimeter over said range of screen diagonals for any field position up to 0.85 of the maximum field is greater than 0.5. - View Dependent Claims (36, 37, 38, 39, 40, 41)
- , said system comprising in order from the system'"'"'s image side;
Specification