US 7,002,753 B2Granted

Color-corrected projection lenses for use with pixelized panels

Assignee3M Innovative Properties Company

InventorJacob Moskovich

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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 (vL2) which is (a) less than or equal to 55 and (b) less than the Abbe number (VL1) of the first lens element (L1). The second lens element (L2) also has an optical power (φL2/0.7CA) 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 (φL2). This combination of lens shapes, Abbe numbers, and optical powers provides higher order lateral color correction without the need for abnormal partial dispersion glasses.

Claims25

Dependent claims

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 vL1, said element having at least one aspherical surface and an on-axis optical power φL1;
and
(B) a second lens element L2 composed of an optical material having an Abbe number vL2, said element having at least one aspherical surface and an on-axis optical power φL2;
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) φL1, vL1, φL2, and vL2 satisfy the relationships:
(i) φL1<0;
(ii) |φL1|>|φL2|;
(iii) vL2<vL1;
and
(iv) vL2≦55;
and
(e) the at least one aspherical surface of the second lens element L2 is configured so that the element has an optical power φL2/0.7CA at 0.7 of the clear aperture of its short conjugate surface which satisfies the relationships:
φL2/0.7CA<0, and
|φL2/0.7CA|>|φL2|.

17 more elements

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 vL1, said element having at least one aspherical surface and an on-axis optical power φL1;
and
(B) a second lens element L2 composed of an optical material having an Abbe number vL2, said element having at least one aspherical surface and an on-axis optical power φL2, said at least one aspherical surface being configured so that the element has a negative optical power φL2/0.7CA 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 φU2/S1 and comprising a single lens element;
and
(B) a second lens subunit having an optical power φU2/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) φL1, vL1, φL2, vL2, φU2/S1, φU2/S2, φL2/0.7CA and D satisfy the relationships:
(i) φL1<0;
(ii) |φL1|>|φL2|;
(iii) vL2<vL1;
(iv) vL2≦55;
(V) φU2/S1>0;
(vi) φU2/S1>|φU2/S2|;
(vii) |φL2/0.7CA|>|φL2|;
and
(viii) |D|/f0≦0.2.

28 more elements

Dependencies are inferred from the claim text.