Foldable projection lenses

• US 7,145,729 B2
• Filed: 08/01/2005
• Issued: 12/05/2006
• Est. Priority Date: 08/04/2004
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Moskovich, Jacob, Kreitzer, Melvyn H.
• Primary Examiner(s): SCHWARTZ, JORDAN MARC
• Application Number:
  US11/194,322
• Publication Number:
  US 20060028738A1
• Time in Patent Office: 491 Days
• Field of Search: 359649-651
• US Class Current: 359/649
• 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
• 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 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 9/10 one + and one - component

Abstract

Projection lenses for use with pixelized panels (PP) are provided. The projection lenses have a first unit (U1) separated from a positive second unit (U2) by a distance sufficient to accept a reflective surface (RS) for folding the lens'"'"' optical axis. The lenses are telecentric on the short conjugate side, have a large field of view in the direction of the long conjugate, and have low aberration levels. By using negative lens elements (L_U1/N1 and L_U1/N2) composed of plastic materials having large positive Q-values at the long conjugate side of the first lens unit (U1), the lenses can achieve low levels of lateral color, including low levels of secondary lateral color, with reduced cost compared to lenses which employ anomalous dispersion glasses in the first lens unit.

Claims

1. A projection lens for forming an enlarged image of a pixelized panel on a screen, said projection lens having an optical axis, 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 comprising a plurality of lens elements one of which has an optical surface S₁ which constitutes the short conjugate end of the first lens unit, said plurality of lens elements having a minimum clear aperture CA_min/U1 and comprising;

(A) a lens element L_U1/N1 which;

(i) comprises at least one aspheric surface,

(ii) comprises a plastic material having a V-value V_U1/N1 and a Q-value Q_U1/N1,

(iii) has a focal length f_U1/N1,

(iv) has a lens element f-number F/#_U1/N1, and

(v) has a short conjugate surface which is concave towards the short conjugate side;

(B) a lens element L_U1/N2 which;

(i) comprises at least one aspheric surface,

(ii) comprises a plastic material having a V-value V_U1/N2 and a Q-value Q_U1/N2,

(iii) has a focal length f_U1/N2, and

(iv) has a lens element f-number F/#_U1/N2; and

(C) a lens element L_U1/P which;

(i) comprises a glass material having a Q-value Q_U1/P, and

(ii) has a focal length f_U1/P; and

(II) a second lens unit having a positive power, said lens unit comprising a plurality of lens elements one of which has an optical surface S₂ which constitutes the long conjugate end of the second lens unit, said plurality of lens elements having a maximum clear aperture CA_max/U2 and comprising a lens element L_U2/P1 which;

(i) comprises a glass material have a Q-value Q_U2/P1, and

(ii) has a focal length f_U2/P1;

wherein;

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

(b) the first lens unit does not include any lens elements which comprise a glass material having a Q-value greater than 50.0;

(c) the projection lens has a field of view in the direction of the long conjugate which is greater than or equal to 85 degrees;

(d) the projection lens is telecentric on the short conjugate side;

(e) the projection lens has an effective back focal length BFL which satisfies the relationship;

BFL/f₀≧

2.0;

(f) the projection lens has a mechanical spacing S_1-2 between S₁ and S₂ which satisfies the relationship;

S_1-2/f₀≧

3.5,

where the mechanical spacing is the smaller of the center-to-center distance and the edge-to-edge distance between S₁ and S₂ for an unfolded optical axis; and

(g) f_U1/N1, F/#_U1/N1, V_U1/N1, Q_U1/N1, f_U1/N2, F/#_U1/N2, V_U1/N2, Q_U1/N2, f_U1/P, Q_U1/P, f_U2/P1, Q_U2/P1, C_min/U1, and C_max/U2 satisfy the relationships;

f_U1/N1<

0

F/#_U1/N1≦

1.0;

V_U1/N1≧

45;

Q_U1/N1≧

100.0;

f_U1/N2<

0;

F/#_U1/N2≦

1.5;

V_U1/N2≧

45;

Q_U1/N2≧

100.0;

f_U1/P>

0;

Q_U1/P≦

50.0;

f_U2/P1>

0;

Q_U2/P1≧

35.0;

and

CA_max/U2/CA_min/U1≦

1.0.

2. The projection lens of claim 1 wherein the L_U1/N2 lens element is biconcave.

3. The projection lens of claim 1 wherein the L_U1/N1 lens element and/or the L_U1/N2 lens element comprises two aspheric surfaces.

4. The projection lens of claim 1 wherein the glass material of the L_U1/P lens element has an index of refraction N_U1/P which satisfies the relationship:

N_U1/P≧

1.6.

5. The projection lens of claim 1 wherein the glass material of the L_U1/P lens element has a V-value V_U1/P which satisfies the relationship:

V_U1/P≦

75.

6. The projection lens of claim 1 wherein the plurality of lens elements of the first lens unit comprises a lens element L_U1/N3 which:

(i) comprises a glass material, and

(ii) has a focal length f_U1/N3,

where f_U1/N3 satisfies the relationships;

f_U1/N3<

0.

7. The projection lens of claim 6 wherein the glass material of L_U1/N3 has an index of refraction N_U1/N3 which satisfies the relationship:

N_U1/N3≦

1.9.

8. The projection lens of claim 6 wherein lens elements L_U1/P and L_U1/N3 are in the form of a cemented doublet.

9. The projection lens of claim 1 wherein the plurality of lens elements of the second lens unit comprises a lens element L_U2/P2 which:

(i) comprises a glass material having a Q-value Q_U2/P2, and

(ii) has a focal length f_U2/P2,

where f_U2/P2 and Q_U2/P2 satisfy the relationships;

f_U2/P2>

0;

and

Q_U2/P2≧

35.0.

10. The projection lens of claim 9 wherein the plurality of lens elements of the second lens unit comprises a lens element L_U2/P3 which:

(i) comprises a glass material having a Q-value Q_U2/P3, and

(ii) has a focal length f_U2/P3,

where f_U2/P3 and Q_U2/P3 satisfy the relationships;

f_U2/P3>

0;

and

Q_U2/P3≧

35.0.

11. The projection lens of claim 1, 9, or 10 wherein:

Q_U2/P1≧

45.0.

12. The projection lens of claim 1, 9, or 10 wherein:

Q_U2/P1≧

100.0.

13. The projection lens of claim 9 or 10 wherein:

Q_U2/P2≧

45.0.

14. The projection lens of claim 9 or 10 wherein:

Q_U2/P2≧

100.0.

15. The projection lens of claim 10 wherein:

Q_U2/P3≧

45.0.

16. The projection lens of claim 10 wherein:

Q_U2/P3≧

100.0.

17. The projection lens of claim 1 wherein the lens has a lateral color LC in its short conjugate focal plane which satisfies the relationships:

LC_red-blue≦

0.0003*f₀,

LC_red-green≦

0.0009*f₀,

and

LC_blue-green≦

0.0006*f₀,

where (i) the red-blue and red-green relationships are satisfied over the full field in the short conjugate focal plane, (ii) the blue-green relationship is satisfied over at least 95% of the full field in the short conjugate focal plane, and (iii) the red, green, and blue wavelengths are 0.64 micrometers, 0.55 micrometers, and 0.44 micrometers, respectively.

18. The projection lens of claim 1 wherein the projection lens has a percentage distortion D which:

(i) over the full field has a magnitude that is less than or equal to 1.0; and

(ii) over the half field-to-full field range has a maximum value D_max and a minimum value D_min which satisfy the relationship;

|D_max−

D_min|≦

0.4.

19. The projection lens of claim 1 wherein the lens exhibits no more than 35 percent vignetting at its working f-number, said working f-number being less than or equal to 2.4.

20. The projection lens of claim 1 further comprising a reflective surface for folding the projection lens'"'"' optical axis, said reflective surface being between the first lens unit and the second lens unit.

21. The projection lens of claim 20 wherein the projection lens comprises an aperture stop between the reflective surface and the second lens unit.

22. The projection lens of claim 21 wherein the spacing S_1-AS between the center of S₁ and the center of the aperture stop satisfies the relationship:

S_1-AS/f₀≧

3.0

23. The projection lens of claim 1 wherein an axial marginal ray traced through the projection lens from the projection lens'"'"' short conjugate focal plane intersects each lens surface of the projection lens at an angle of incidence that is greater than or equal to 1.5 degrees except for (i) the lens surfaces of L_U1/N1 and (ii) any lens surfaces which are on the long conjugate side of L_U1/N1 for which the angle of incidence may be greater than, less than, or equal to 1.5 degrees.

24. A projection lens system comprising:

(a) a pixelized panel; and

(b) the projection lens of claim 1.

25. The projection lens systems of claim 24 further comprising an illumination system which comprises a light source and illumination optics which forms an image of the light source.

26. A projection lens for forming an enlarged image of a pixelized panel on a screen, said projection lens having an optical axis, 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 comprising a plurality of lens elements one of which has an optical surface S₁ which constitutes the short conjugate end of the first lens unit, said plurality of lens elements having a minimum clear aperture CA_min/U1 and consisting of;

(A) a lens element L_U1/N1 which;

(i) comprises at least one aspheric surface,

(ii) comprises a plastic material having a V-value V_U1/N1 and a Q-value Q_U1/N1,

(iii) has a focal length f_U1/N1,

(iv) has a lens element f-number F/#_U1/N1, and

(v) has a short conjugate surface which is concave towards the short conjugate side;

(B) a lens element L_U1/N2 which;

(i) comprises at least one aspheric surface,

(ii) comprises a plastic material having a V-value V_U1/N2 and a Q-value Q_U1/N2,

(iii) has a focal length f_U1/N2,

(iv) has a lens element f-number F/#_U1/N2, and

(v) has a biconcave form;

(C) a lens element L_U1/P which;

(i) comprises a glass material having a V-value V_U1/P, a Q-value Q_U1/P, and an index of refraction N_U1/P; and

(ii) has a focal length f_U1/P; and

(D) a lens element L_U1/N3 which;

(i) comprises a glass material having an index of refraction N_U1/N3, and

(ii) has a focal length f_U1/N3,

(II) a reflective surface for folding the projection lens'"'"' optical axis; and

(III) a second lens unit having a positive power, said lens unit comprising a plurality of lens elements one of which has an optical surface S₂ which constitutes the long conjugate end of the second lens unit, said plurality of lens elements having a maximum clear aperture CA_max/U2 and comprising;

(A) a lens element L_U2/P1 which;

(i) comprises a glass material have a Q-value Q_U2/P1, and

(ii) has a focal length f_U2/P1; and

(B) a lens element L_U2/P2 which;

(i) comprises a glass material having a Q-value Q_U2/P2, and

(ii) has a focal length f_U2/P2,

wherein;

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

(b) the L_U1/N1 lens element and/or the L_U1/N2 lens element comprises two aspheric surfaces;

(c) the lens elements L_U1/P and L_U1/N3 are in the form of a cemented doublet;

(d) the projection lens has a field of view in the direction of the long conjugate which is greater than or equal to 85 degrees;

(e) the projection lens is telecentric on the short conjugate side;

(f) the projection lens has an effective back focal length BFL which satisfies the relationship;

BFL/f₀≧

2.0;

(g) the projection lens has a mechanical spacing S_1-2 between S₁ and S₂ which satisfies the relationship;

S_1-2/f₀≧

3.5,

where the mechanical spacing is the smaller of the center-to-center distance and the edge-to-edge distance between S₁ and S₂ for an unfolded optical axis; and

(h) f_U1/N1, F/#_U1/N1, V_U1/N1, Q_U1/N1, f_U1/N2, F/#_U1/N2, V_U1/N2, Q_U1/N2, f_U1/P, Q_U1/P, N_U1/P, V_U1/P, f_U1/N3, N_U1/N3, f_U2/P1, Q_U2/P1, f_U2/P2, Q_U2/P2, C_min/U1, and C_max/U2 satisfy the relationships;

f_U1/N1<

0;

F/#_U1/N1≦

1.0;

V_U1/N1≧

45;

Q_U1/N1≧

100.0;

f_U1/N2<

0;

F/#_U1/N2≦

1.5;

V_U1/N2≧

45;

Q_U1/N2≧

100.0;

f_U1/P>

0;

Q_U1/P≦

50.0;

N_U1/P≧

1.6;

V_U1/P≦

75;

f_U1/N3<

0;

N_U1/N3≦

1.9;

f_U2/P1>

0;

Q_U2/P1≧

35.0;

f_U2/P2≧

0;

Q_U2/P2≧

35.0;

and

CA_max/U2/CA_min/U1≦

1.0.

27. The projection lens of claim 26 wherein L_U1/P is on the short conjugate side of L_U1/N3.

28. The projection lens of claim 26 wherein L_U1/P is on the long conjugate side of L_U1/N3.

29. The projection lens of claim 26 wherein the plurality of lens elements of the second lens unit comprises a lens element L_U2/P3 which:

(i) comprises a glass material having a Q-value Q_U2/P3, and

(ii) has a focal length f_U2/P3,

where f_U2/P3 and Q_U2/P3 satisfy the relationships;

f_U2/P3>

0;

and

Q_U2/P3≧

35.0.

30. The projection lens of claim 26 wherein the lens has a lateral color LC in its short conjugate focal plane which satisfies the relationships:

LC_red-blue≦

0.0003*f₀,

LC_red-green≦

0.0009*f₀,

and

LC_blue-green≦

0.0006*f₀,

where (i) the red-blue and red-green relationships are satisfied over the full field in the short conjugate focal plane, (ii) the blue-green relationship is satisfied over at least 95% of the full field in the short conjugate focal plane, and (iii) the red, green, and blue wavelengths are 0.64 micrometers, 0.55 micrometers, and 0.44 micrometers, respectively.

31. The projection lens of claim 26 wherein the projection lens has a percentage distortion D which:

(i) over the full field has a magnitude that is less than or equal to 1.0; and

(ii) over the half field-to-full field range has a maximum value D_max and a minimum value D_min which satisfy the relationship;

|D_max−

D_min|≦

0.4.

32. The projection lens of claim 26 wherein the lens exhibits no more than 35 percent vignetting at its working f-number, said working f-number being less than or equal to 2.4.

33. A projection lens system comprising:

(a) a pixelized panel; and

(b) the projection lens of claim 26.

34. The projection lens systems of claim 33 further comprising an illumination system which comprises a light source and illumination optics which forms an image of the light source.