COLOR-CORRECTED PROJECTION LENSES FOR USE WITH PIXELIZED PANELS

• US 20050270657A1
• Filed: 06/02/2004
• Published: 12/08/2005
• Est. Priority Date: 06/02/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Moskovich, Jacob
• Granted Patent: US 7,002,753 B2
• Time in Patent Office: Days
• US Class Current: 359/649
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV

Abstract

Projection lenses for use with pixelized panels (PP) are provided. The projection lenses have first and second lens units (U1, U2), with the first lens unit having a negative power and the second lens unit having a positive power. The first lens unit has a first lens element (L1) having a generally meniscus shape and a second lens element (L2) having a biconcave shape when its surface configurations are described by best fit spherical surfaces. The second lens element (L2) has an Abbe number (v_L2) which is (a) less than or equal to 55 and (b) less than the Abbe number (v_L1) of the first lens element (L1). The second lens element (L2) also has an optical power (φ_L2/0.7CA) at 0.7 of the clear aperture of its short conjugate surface which is negative and has a magnitude which is greater than the second lens element'"'"'s on-axis optical power (φ_L2). This combination of lens shapes, Abbe numbers, and optical powers provides higher order lateral color correction without the need for abnormal partial dispersion glasses.

Claims

1. A retrofocus lens having a long conjugate side, a short conjugate side, and an effective focal length f₀, said lens, in order from the long conjugate side to the short conjugate side, comprising:

(I) a first lens unit having a negative power, said lens unit, in order from the long conjugate side to the short conjugate side, comprising;

(A) a first lens element L1 composed of an optical material having an Abbe number v_L1, said element having at least one aspherical surface and an on-axis optical power φ

_L1; and

(B) a second lens element L2 composed of an optical material having an Abbe number v_L2, said element having at least one aspherical surface and an on-axis optical power φ

_L2; and

(II) a second lens unit having a positive power;

wherein;

(a) the first and second lens units are the only lens units of the retrofocus lens;

(b) the first lens element L1 has a generally meniscus shape which is convex towards the long conjugate;

(c) the second lens element L2 has a biconcave shape when its surface configurations are described by best fit spherical curves;

(d) φ

_L1, v_L1, φ

_L2, and v_L2 satisfy the relationships;

φ

_L1<

0 

 

(i);


|φ

_L1|>

|φ

_L2|;

 

 

(ii)
v_L2<

v_L1; and

 

 

(iii)
v_L2≦

55; and

 

 

(iv)

(e) the at least one aspherical surface of the second lens element L2 is configured so that the element has an optical power φ

_L2/0.7CA at 0.7 of the clear aperture of its short conjugate surface which satisfies the relationships;

φ

_L2/0.7CA<

0, and
|φ

_L2/0.7CA|>

|φ

_L2|.

2. The retrofocus lens of claim 1 wherein:

φ

_L2<

0.

3. The retrofocus lens of claim 1 where the lens elements L1 and L2 respectively have center thicknesses t_c/L1 and t_c/L2, and edge thicknesses t_e/L1 and t_e/L2 which satisfy the relationships:

t_e/L1/t_c/L1≦

3.5; and


t_e/L2/t_c/L2≦

3.5;

where the edge thickness in each case is determined at the smaller of the clear apertures of the two optical surfaces of the respective element.

4. The retrofocus lens of claim 3 where t_c/L1, t_c/L2, t_e/L1, and t_e/L2 satisfy the relationships:

t_e/L1/t_c/L1≦

3.0; and


t_e/L2/t_c/L2≦

3.0.

5. The retrofocus lens of claim 1 wherein:

(a) the lens comprises an aperture stop;

(b) the second lens unit, in order from the long conjugate side to the short conjugate side, comprises a first lens subunit having an optical power φ

_U2/S1 and a second lens subunit having an optical power φ

_U2/S2, said subunits being the only lens subunits of the second lens unit;

(c) the aperture stop is either within the first lens subunit or is outside of that subunit and spaced from the subunit by an axial distance D, said distance being measured from the lens surface of the first lens subunit that is nearest to the aperture stop;

(d) the second lens subunit comprises;

(i) at least one color-correcting component; and

(ii) a lens element L3 having at least one aspherical surface; and

(e) φ

_U2/S1, φ

_U2/S2, and D satisfy the relationships;

φ

_U2/S1>

0;

 

 

(i)
φ

_U2/S1>

|φ

_U2/S1|; and

 

 

(ii)
|D|/f₀≦

0.2. 

 

(iii)

6. The retrofocus lens of claim 5 where D satisfies the relationship:

|D|/f₀≦

0.1.

7. The retrofocus lens of claim 5 where the lens elements L1, L2, and L3 respectively have center thicknesses t_c/L1, t_c/L2, and t_c/L3, and edge thicknesses t_e/L1, t_e/L2, and t_e/L3 which satisfy the relationships:

t_e/L1/t_c/L1≦

3.5;


t_e/L2/t_c/L2≦

3.5; and


t_e/L3/t_c/L3≦

3.5;

where the edge thickness in each case is determined at the smaller of the clear apertures of the two optical surfaces of the respective element.

8. The retrofocus lens of claim 7 where t_c/L1, t_c/L2, t_c/L3, t_e/L1, t_e/L2, and t_e/L3 satisfy the relationships:

t_e/L1/t_c/L1≦

3.0;


t_e/L2/t_c/L2≦

3.0; and


t_e/L3/t_c/L3≦

3.0.

9. The retrofocus lens of claim 5 where the first lens subunit of the second lens unit comprises a single lens element.

10. The retrofocus lens of claim 5 where the color correcting component of the second lens subunit of the second lens unit is a cemented doublet.

11. The retrofocus lens of claim 5 where the L3 element has a focal length f_L3 which satisfies the relationship:

|f_L3|/f₀≧

1.5.

12. The retrofocus lens of claim 1 where the lens has a full field of view in the direction of the long conjugate which is greater than or equal to 85 degrees.

13. The retrofocus lens of claim 1 wherein the lens has a full field of view in the direction of the short conjugate which is greater than or equal to 50 degrees.

14. The retrofocus lens of claim 1 where the lens has a barrel length BRL which satisfies the relationship:

BRL/f₀≦

1.7.

15. The retrofocus lens of claim 1 where the lens has a maximum clear aperture CA_max which satisfies the relationship:

CA_max/f₀≦

1.3.

16. The retrofocus lens of claim 1 where the lens has a total of six lens elements.

17. A projection lens system comprising:

(a) a pixelized panel; and

(b) the retrofocus lens of claim 1.

18. The projection lens system of claim 17 where the pixelized panel has a diagonal which is greater than or equal to 250 millimeters.

19. The projection lens system of claim 17 further comprising a Fresnel lens between the pixelized panel and the retrofocus lens.

20. The projection lens system of claim 17 further comprising an illumination system which comprises a light source and illumination optics which transfers some of the light from the light source towards the pixelized panel and the retrofocus lens.

21. A retrofocus lens having a long conjugate side, a short conjugate side, an aperture stop, and an effective focal length f₀, said lens, in order from the long conjugate side to the short conjugate side, comprising:

(I) a first lens unit having a negative power, said lens unit, in order from the long conjugate side to the short conjugate side, comprising;

(A) a first lens element L1 composed of an optical material having an Abbe number v_L1, said element having at least one aspherical surface and an on-axis optical power φ

_L1; and

(B) a second lens element L2 composed of an optical material having an Abbe number v_L2, said element having at least one aspherical surface and an on-axis optical power φ

_L2, said at least one aspherical surface being configured so that the element has a negative optical power φ

_L2/0.7CA at 0.7 of the clear aperture of its short conjugate surface; and

(II) a second lens unit having a positive power, said lens unit, in order from the long conjugate side to the short conjugate side, comprising;

(A) a first lens subunit having an optical power φ

_U2/S1 and comprising a single lens element; and

(B) a second lens subunit having an optical power φ

_U2/S2, said subunit, in order from the long conjugate side to the short conjugate side, comprising;

(i) two lens elements which comprise a color-correcting doublet; and

(ii) a lens element L3 having at least one aspherical surface;

wherein;

(a) the first and second lens units are the only lens units of the retrofocus lens;

(b) the first and second lens elements L1 and L2 are the only lens elements of the first lens unit;

(c) the first and second lens subunits are the only lens subunits of the second lens unit;

(d) the two lens elements comprising a color-correcting doublet and lens element L3 are the only lens elements of the second lens subunit;

(e) the first lens element L1 has a generally meniscus shape which is convex towards the long conjugate;

(f) the second lens element L2 has a biconcave shape when its surface configurations are described by best fit spherical curves;

(g) the aperture stop is either within the first lens subunit or is spaced from that subunit by an axial distance D, said distance being measured from the lens surface of the first lens subunit that is nearest to the aperture stop; and

(h) φ

_L1, v_L1, φ

_L2, v_L2, φ

_U2/S1, φ

_U2/S2, φ

_L2/0.7CA and D satisfy the relationships;

φ

_L1<

0;

 

 

(i)
|φ

_L1|>

|φ

_L2|;

 

 

(ii)
v_L2<

v_L1;

 

 

(iii)
v_L2≦

55;

 

 

(iv)
φ

_U2/S1>

0;

 

 

(V)
φ

_U2/S1>

φ

_U2/S2|;

 

 

(Vi)
|φ

_L2/0.7CA|>

|φ

_L2|; and

 

 

(vii)
|D|/f₀≦

0.2. 

 

(viii)

22. The retrofocus lens of claim 21 wherein:

φ

_L2<

0.

23. A projection lens system comprising:

(a) a pixelized panel; and

(b) the retrofocus lens of claim 21.

24. The projection lens system of claim 23 further comprising a Fresnel lens between the pixelized panel and the retrofocus lens.

25. The projection lens system of claim 23 further comprising an illumination system which comprises a light source and illumination optics which transfers some of the light from the light source towards the pixelized panel and the retrofocus lens.