Loupe

Claim 2

A magnifier comprising from the viewing end, a first positive lens group comprising a singlet element, a second lens group comprising a bi-convex element and a bi-concave element forming a doublet having the overall shape of a meniscus, said elements having surfaces S1-S5 with curvatures C1-C5 numbered successively from the viewing end where the curvature is the equivalent focal length of the lens, divided by the surface radius at the optical axis, and 0.2 < C1 < 0.75 1.0 < c2 < 1.7 1.2 < c3 < 1.9 1.0 < c4 < 5.0 1.5 < c5 < 3.5.

Claim 3

the magnifier of claim 1 wherein said first element has first and second surfaces S1 and S2, said second group has surfaces S3, S4 and S5, all surfaces numbered from the viewing end, and one of surface S4, and surfaces S3 and S5 are aspheric.

Claim 4

The magnifier of claim 2, where surface S2 is aspheric.

Claim 5

The magnifier of claim 2 where surface S4 is aspheric.

Claim 6

The magnifier of claim 2 where surfaces S3 and S5 are aspheric.

Claim 7

The magnifier of claim 2 where surfaces S3 and S5 are aspheric, and where C3 > |C4| c5 > |c4|.

Claim 8

the magnifier of claim 1 wherein said surfaces S1-S5 have curvatures C1-C5 respectively at the optical axis where C is the equivalent focal length of the overall lens divided by the surface radius of each surface at the optical axis where surface S4 is aspheric, and where |C4| > C3 |c4| > c5.

Claim 9

the magnifier of claim 2 where the sum of the absolute value of the curvatures of said surfaces S3, S4 and S5 respectively is between five and eight.

Claim 10

The magnifier of claim 1 wherein said first group has subtending surfaces S1 and S2, said second lens group has surfaces S3, S4 and S5 and the sum of the absolute values of the curvatures of surfaces S3, S4 and S5 respectively is between five and eight.

Claim 11

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .620 L1 .398 1.491 57.1 S2 -1.351 .015 S3 1.571 L2 .452 1.491 57.1 S4 -1.252 L3 .078 1.590 30.8 S5 2.829 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 -1.748 0 S3 - .435 0 S5 - .614 0 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 12

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .238 L1 .316 1.491 57.1 S2 -1.564 .015 S3 1.393 L2 .542 1.491 57.1 S4 -3.778 L3 .078 1.590 30.8 S5 1.895 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 - .717 .103 S4 -2.144 .038 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 13

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .324 L1 .321 1.491 57.1 S2 -1.467 .015 S3 1.400 L2 .569 1.491 57.1 S4 -4.098 L3 .078 1.590 30.8 S5 2.005 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 - .771 .101 S4 -2.109 -.025 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 14

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .592 L1 .403 1.491 57.1 S2 -1.267 .015 S3 1.266 L2 .608 1.491 57.1 S4 -3.889 L3 .078 1.590 30.8 S5 1.987 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 -1.362 0 S4 -1.584 0 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 15

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .712 L1 .313 1.490 57.1 S2 -1.452 .014 S3 1.804 L2 .348 1.490 57.1 S4 -1.338 .070 1.589 30.8 S5 3.115 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 -1.759 0 S3 -0.605 0 S5 -0.805 0 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 16

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between Surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .210 L1 .316 1.491 57.1 S2 -1.600 .015 S3 1.390 L2 .518 1.491 57.1 S4 -3.420 L3 .078 1.590 30.8 S5 1.770 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 - .735 .102 S4 -2.203 -.069 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.

Claim 17

The lens of claim 1 defined substantially as follows: ______________________________________ Surface Axial Distance Curvatures Between surfaces/BFL N.sub.d V.sub.d ______________________________________ S1 .606 L1 .389 1.491 57.1 S2 -1.283 .015 S3 1.261 L2 .598 1.491 57.1 S4 -3.891 L3 .078 1.590 30.8 S5 2.000 ______________________________________ ______________________________________ Aspheric Surfaces K G ______________________________________ S2 -1.470 0 S3 .070 0 S4 -1.618 0 S5 .015 0 ______________________________________ where EFL is the equivalent focal length of the lens; L1-L3 are successive elements with L1 closest to the viewer, S1-S5 are successive surface curvatures of elements L1-L3 at the optical axis where the curvature is the EFL of the lens divided by radius of the surface at the optical axis; and aspheric surfaces are defined by the equation: X-1/2C(K+1)X.sup.2 -1/2CY.sup.2 +G(C.sup.3 /2)Y.sup.4 = 0 where X is the sag of the surface along an abscissa on the optical axis at the radial distance Y from the optical axis; C is the curvature of the surface; K is a conic constant and G is a higher order coefficient of aspheric sag of the surface; N d is the index of refraction and V d is the Abbe number of the elements.