Zoom projection lens

Claim 1

A zoom projection lens comprising six elements and having a focal length that varies from 15 to 30mm when constructed according to the following parameters: EXAMPLE 1 ______________________________________ Radius Thickness or Element N.sub.D V mm Separation mm ______________________________________ R.sub.1 =54.086 1 1.49168 57.4 T.sub.1 =4.000 R.sub.2 = -324.17 1.911 S.sub.1 = to 25.018 R.sub.3 =Asphere 2 1.49168 57.4 T.sub.2 =1.600 R.sub.4 =38.425 24.114 S.sub.2 = to 1.007 R.sub.5 =Asphere 3 1.49168 57.4 T.sub.3 =3.631 R.sub.6 = -28.253 S.sub.3 =0.100 R.sub.7 =9.7250 4 1.49168 57.4 T.sub.4 =5.000 R.sub.8 = -21.155 5 1.59028 30.9 T.sub.5 =4.000 R.sub.9 =7.2951 S.sub.4 =1.932 R.sub.10 =15.403 6 1.60530 43.6 T.sub.6 =6.000 R.sub.11 = -33.791 ______________________________________ wherein, from front to rear, the elements are numbered from 1 to 6, the corresponding indices of refraction, N D , and Abbe numbers, V, are listed for each element, the radii of curvature of the surfaces are numbered from R 1 to R 11 , the thicknesses of the elements are numbered from T 1 to T 6 , the spacings between the elements are numbered from S 1 to S 4 , and wherein R 3 and R 5 represent the vertex radius of curvature of an aspheric surface defined by the following formula and parameters: Cy.sup.2 x = 1+√1- (1+K)C.sup.2 y.sup.2 Surface C K ______________________________________ 3 -.03504960 -2.41830036 5 .03137796 -9.89410310 ______________________________________ wherein x is the sag of the aspheric surface from a plane reference surface at a radial distance y from the axis to the lens, c is equal to the reciprocal of the vertex radius of curvature and K is the conic constant.