Foldable projection lenses
Assignee3M Innovative Properties Company
InventorsMelvyn H. Kreitzer, Jacob Moskovich
Life of this patent
Estimating the term…
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 (LU1/N1 and LU1/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.
Claims34
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 CAmin/U1 and comprising:
- (A) a lens element LU1/N1 which:
- (i) comprises at least one aspheric surface,
- (ii) comprises a plastic material having a V-value VU1/N1 and a Q-value QU1/N1,
- (iii) has a focal length fU1/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 LU1/N2 which:
- (i) comprises at least one aspheric surface,
- (ii) comprises a plastic material having a V-value VU1/N2 and a Q-value QU1/N2,
- (iii) has a focal length fU1/N2, and
- (iv) has a lens element f-number F/#U1/N2;
- and
- (C) a lens element LU1/P which:
- (i) comprises a glass material having a Q-value QU1/P, and
- (ii) has a focal length fU1/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 CAmax/U2 and comprising a lens element LU2/P1 which:
- (i) comprises a glass material have a Q-value QU2/P1, and
- (ii) has a focal length fU2/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 S1-2 between S1 and S2 which satisfies the relationship:
- S1-2/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) fU1/N1, F/#U1/N1, VU1/N1, QU1/N1, fU1/N2, F/#U1/N2, VU1/N2, QU1/N2, fU1/P, QU1/P, fU2/P1, QU2/P1, Cmin/U1, and Cmax/U2 satisfy the relationships:
- fU1/N1<0
- F/#U1/N1≦1.0;
- VU1/N1≧45;
- QU1/N1≧100.0;
- fU1/N2<0;
- F/#U1/N2≦1.5;
- VU1/N2≧45;
- QU1/N2≧100.0;
- fU1/P>0;
- QU1/P≦50.0;
- fU2/P1>0;
- QU2/P1≧35.0;
- and
- CAmax/U2/CAmin/U1≦1.0.
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 CAmin/U1 and consisting of:
- (A) a lens element LU1/N1 which:
- (i) comprises at least one aspheric surface,
- (ii) comprises a plastic material having a V-value VU1/N1 and a Q-value QU1/N1,
- (iii) has a focal length fU1/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 LU1/N2 which:
- (i) comprises at least one aspheric surface,
- (ii) comprises a plastic material having a V-value VU1/N2 and a Q-value QU1/N2,
- (iii) has a focal length fU1/N2,
- (iv) has a lens element f-number F/#U1/N2, and
- (v) has a biconcave form;
- (C) a lens element LU1/P which:
- (i) comprises a glass material having a V-value VU1/P, a Q-value QU1/P, and an index of refraction NU1/P;
- and
- (ii) has a focal length fU1/P;
- and
- (D) a lens element LU1/N3 which:
- (i) comprises a glass material having an index of refraction NU1/N3, and
- (ii) has a focal length fU1/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 CAmax/U2 and comprising:
- (A) a lens element LU2/P1 which:
- (i) comprises a glass material have a Q-value QU2/P1, and
- (ii) has a focal length fU2/P1;
- and
- (B) a lens element LU2/P2 which:
- (i) comprises a glass material having a Q-value QU2/P2, and
- (ii) has a focal length fU2/P2,
- wherein:
- (a) the first and second lens units are the only lens units of the projection lens;
- (b) the LU1/N1 lens element and/or the LU1/N2 lens element comprises two aspheric surfaces;
- (c) the lens elements LU1/P and LU1/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 S1-2 between S1 and S2 which satisfies the relationship:
- S1-2/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) fU1/N1, F/#U1/N1, VU1/N1, QU1/N1, fU1/N2, F/#U1/N2, VU1/N2, QU1/N2, fU1/P, QU1/P, NU1/P, VU1/P, fU1/N3, NU1/N3, fU2/P1, QU2/P1, fU2/P2, QU2/P2, Cmin/U1, and Cmax/U2 satisfy the relationships:
- fU1/N1<0;
- F/#U1/N1≦1.0;
- VU1/N1≧45;
- QU1/N1≧100.0;
- fU1/N2<0;
- F/#U1/N2≦1.5;
- VU1/N2≧45;
- QU1/N2≧100.0;
- fU1/P>0;
- QU1/P≦50.0;
- NU1/P≧1.6;
- VU1/P≦75;
- fU1/N3<0;
- NU1/N3≦1.9;
- fU2/P1>0;
- QU2/P1≧35.0;
- fU2/P2≧0;
- QU2/P2≧35.0;
- and
- CAmax/U2/CAmin/U1≦1.0.
Dependencies are inferred from the claim text.