Abstract:
Microscope objectives having a numerical aperture of substantially 0.25 and a magnification of about 10X provide a substantially flat image field of about 24mm.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to microscope objectives and more particularly to microscope objectives which have a numerical aperture of substantially 0.25, a magnification of substantially 10X and a substantially flat image field of about 24mm. The microscope objectives of this invention are well corrected for the usual chromatic image aberrations, as well as spherical aberration, coma and astigmatism. The substantially flat image field of about 24mm is provided when the objectives are used with a conventional 10X eyepiece and a microscope having a telescope objective as described in U.S. Pat. No. 3,355,234. 
    
    
     THE DRAWINGS 
     FIG. 1 is an optical diagram of one embodiment of the present invention; 
     FIG. 2 is an optical diagram of another embodiment of the present invention; 
     FIG. 3 is an optical diagram of a further embodiment of the present invention; and 
     FIG. 4 is an optical diagram of a still further embodiment of the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the objective XX is shown in a view transverse to its optical axis relative to object plane O and illustrate the lens elements aligned along the optical axis. The first element I of the objective is a concavo-convex positive singlet followed by the second lens element II, which is also a concavo-convex positive singlet. The third and final lens element III of the embodiment is a double convex positive doublet. The parameters of the objective are set forth in Table I wherein the axial thicknesses of successive lens elements are designated T1 to T4, and the successive axial spaces from the object plane (designated O) are S1 to S3. The successive lens radii are designated R1 to R7 wherein the minus sign (-) applies to surfaces whose center of curvature lies on the object side of their vertices. The refractive indices and Abbe numbers of the glasses in the successive lenses are absolute values designated ND(1) to ND(4), and ν(1) to ν(4) respectively. 
     
                                           TABLE I__________________________________________________________________________                           Refractive                                     AbbeLens Radius  Thickness                  Space    Index     Number__________________________________________________________________________                  S.sub.1 = 0.201360F    R.sub.1 = -0.297233FI             T.sub.1 = 0.273567F                           ND(1) = 1.78816                                     ν(1) = 47.37    R.sub.2 = -0.449693F                  S.sub.2 = 0.005471F    R.sub.3 = -2.09030FII            T.sub.2 = 0.164140F                           ND(2) = 1.78816                                     ν(2) = 47.37    R.sub.4 = -0.0780545F                  S.sub.3 = 0.961457F    R.sub.5 = 113.3618F         T.sub.3 = 0.082070F                           ND(3) = 1.80491                                     ν(3) = 25.42III R.sub.6 = 1.19907F         T.sub.4 = 0.191497F                           ND(4) = 1.58304                                     ν(4) = 59.43    R.sub.7 = -1.01792F__________________________________________________________________________ 
    
     In the foregoing, as well as succeeding tables, F is the focal length of the objective in millimeters and all values are to be considered variable within normal manufacturing tolerances. 
     The optical values for a specific objective of this embodiment having a focal length of 18.277mm are: 
     
                       TABLE II______________________________________Lens     Radius      Thickness   Space______________________________________                            S.sub.1 = 3.680  R.sub.1 = -5.4325I                    T.sub.1 = 5.000  R.sub.2 = -8.2190                            S.sub.2 = 0.100  R.sub.3 = -38.204II                   T.sub.2 = 3.000  R.sub.4 = -14.266                            S.sub.3 = 17.573  R.sub.5 = 2071.914                T.sub.3 = 1.500III    R.sub.6 = 21.915                T.sub.4 = 3.500  R.sub.7 = -18.605______________________________________ 
    
     Referring to FIG. 2, which is a preferred embodiment of the present invention, the first three elements, IV, V and VI of objective XXI have the same type of curvature as the three elements shown in FIG. 1 for objective XX. The fourth and final element of this embodiment is a convex-concavo negative singlet. The parameters of this objective are set forth in Table III wherein the axial thicknesses of successive lens elements are designated T5 to T9 and the successive axial spaces from the object plane (designated O) are S4 to S7. The successive lens radii are designated R8 to R16 where the minus sign (-) applies to surfaces whose center of curvature lies on the object side of their vertices. The refractive indices and Abbe numbers of the glasses in the successive lenses are absolute values designated ND(5) to ND(9), and ν(5) to ν(9) respectively. 
     
                                           TABLE III__________________________________________________________________________                        Refractive                                  AbbeLens Radius Thickness                Space   Index     Number__________________________________________________________________________                S.sub.4 = 0.3382F    R.sub.8 = -0.4274FIV           T.sub.5 = 0.2737F                        ND(5) = 1.78833                                  ν(5) = 50.47    R.sub.9 = -0.5552F                S.sub.5 = 0.0328F    R.sub.10 = -0.9581FV            T.sub.6 = 0.1642F                        ND(6) = 1.78833                                  ν(6) = 50.47    R.sub.11 = -0.7506F                S.sub.6 = 0.7957    R.sub.12 = 2.2095F        T.sub.7 = 0.0821F                        ND(7) = 1.78446                                  ν(7) = 25.75VI  R.sub.13 = 0.7295F        T.sub.8 = 0.1916F                        ND(8) = 1.69669                                  ν(8) = 56.13    R.sub.14 = -2.6553F                S.sub.7 = 0.0049F    R.sub.15 = 0.5296FVII          T.sub.9 = 0.1916F                        ND(9) = 1.69669                                  ν(9) = 56.13    R.sub.16 = 0.4342F__________________________________________________________________________ 
    
     The optical values for a specific objective of this embodiment having a focal length of 18.265 are: 
     
                       TABLE IV______________________________________Lens     Radius      Thickness   Space______________________________________                            S.sub.4 = 6.180  R.sub.8 = -7.807IV                   T.sub.5 = 5.000  R.sub.9 = -10.140                            S.sub.5 = 0.600  R.sub.10 = -17.500V                    T.sub.6 = 3.000  R.sub.11 = -13.710                            S.sub.6 = 14.534  R.sub.12 = 40.356                T.sub.7 = 1.500VI     R.sub.13 = 13.325                T.sub.8 = 3.500  R.sub.14 = -48.500                            S.sub.7 = 0.0900  R.sub.15 = 9.674VII                  T.sub.9 = 3.500  R.sub.16 = 7.934______________________________________ 
    
     Referring to FIG. 3, an objective XXII has a first element VIII, which is a concavo-convex positive singlet, a second element IX, which is a concavo-convex positive singlet, a third element X, which is a double convex positive singlet and a fourth element XI, which is a concavo-convex positive doublet. The parameters of this objective are set forth in Table V wherein the axial thicknesses of successive lens elements are designated T9 to T13, and the successive axial spaces from the object plane (designated O) are S8 to S11. The successive lens radii are designated R17 to R25 where the minus sign (-) applies to surfaces whose center of curvature lies on the object side of their vertices. The refractive indices and Abbe numbers of the glasses in the successive lenses are absolute values designated ND(9) to ND(13), and ν(9) to ν(13) respectively. 
     
                                           TABLE V__________________________________________________________________________                           Refractive                                     AbbeLens Radius  Thickness                  Space    Index     Number__________________________________________________________________________                  S.sub.8  = 0.20151F    R.sub.17 = -0.27049FVIII          T.sub.9  = 0.27378F                           ND(9) = 1.78816                                     ν(9) = 47.37    R.sub.18 = -0.47856F                  S.sub.9  = 0.00548F    R.sub.19 = -1.71598FIX            T.sub.10 = 0.16427F                           ND(10) = 1.78816                                     ν(10) = 47.37    R.sub.20 = -0.89799F                  S.sub.10 = 0.25847F    R.sub.21 = 3.03510FX             T.sub.11 = 0.19164F                           ND(11) = 1.78816                                     ν(11) = 47.37    R.sub.22 = -7.39856F                  S.sub.11 = 0.53892F    R.sub.23 = -4.65088F         T.sub.12 = 0.08213F                           ND(12) = 1.80491                                     ν(12) = 25.42XI  R.sub.24 = 0.76274F         T.sub.13 = 0.19164F                           ND(13) = 1.70166                                     ν(13) = 41.00    R.sub.25 = -1.15457F__________________________________________________________________________ 
    
     The optical values for a specific objective of this embodiment having a focal length of 18.263 are set forth in Table VI. 
     
                       TABLE VI______________________________________Lens     Radius     Thickness   Space______________________________________                           S.sub.8  = 3.680  R.sub.17 = -4.940VIII                T.sub.9  = 5.000  R.sub.18 = -8.740                           S.sub.9  = 0.100  R.sub.19 = -13.339IX                  T.sub.10 = 3.000  R.sub.20 = -16.400                           S.sub.10 = 4.720  R.sub.21 = 55.430X                   T.sub.11 = 3.500  R.sub.22 = -135.120                           S.sub.11 = 9.842  R.sub.23 = -84.939               T.sub.12 = 1.500XI     R.sub.24 = 13.930               T.sub.13 = 3.500  R.sub.25 = -21.086______________________________________ 
    
     Referring to FIG. 4, the objective XXIII has the first three elements XII, XIII and XIV with the same type of curvature as the respective elements of objective XXII in FIG. 3. The fourth and final element XV is a double convex positive doublet. The parameters of this objective are set forth in Table VII wherein the axial thicknesses of successive lens elements are designated T14 to T18, and the successive axial spaces from the object plane (designated O) are S12 to S15. The successive lens radii are designated R26 to R34 where the minus sign (-) applies to surfaces whose center of curvature lies on the object side of their vertices. The refractive indices and Abbe numbers of the glasses in the successive lenses are absolute values designated ND(14) to ND(18) and ν(14) to ν(18) respectively. 
     
                                           TABLE VII__________________________________________________________________________                           Refractive                                     AbbeLens Radius  Thickness                  Space    Index     Number__________________________________________________________________________                  S.sub.12 = 0.40735F    R.sub.26 = -0.32605FXII           T.sub.14 = 0.26827F                           ND(14) = 1.78816                                     ν(14) = 47.37    R.sub.27 = -0.53042F                  S.sub.13 = 0.00537F    R.sub.28 = -2.16525FXIII          T.sub.15 = 0.16096F                           ND(15) = 1.78816                                     ν(15) = 47.37    R.sub.29 = -0.99163F                  S.sub.14 = 0.12438F    R.sub.30 = 1.73624FXIV           T.sub.16 = 0.18779F                           ND(16) = 1.78816                                     ν(16) = 47.37    R.sub.31 = -12.952F                  S.sub.15 = 0.41384F    R.sub.32 = 12.952F         T.sub.17 = 0.08048F                           ND(17) = 1.80491                                     ν(17) = 25.42XV  R.sub.33 = 0.79515F         T.sub.18 = 0.18779F                           ND(18) = 1.52249                                     ν(18) = 60.13    R.sub.34 = -1.4003F__________________________________________________________________________ 
    
     The optical values for a specific objective of this embodiment having a focal length of 18.638mm are given in Table VIII. 
     
                       TABLE VIII______________________________________Lens     Radius     Thickness   Space______________________________________                           S.sub.12 = 7.592  R.sub.26 = -6.077XII                 T.sub.14 = 5.000  R.sub.27 = -9.886                           S.sub.13 = 0.100  R.sub.28 = -40.356XIII                T.sub.15 = 3.000  R.sub.29 = -18.482                           S.sub.14 = 2.318  R.sub.30 = 32.360XIV                 T.sub.16 = 3.500  R.sub.31 = -241.400                           S.sub.15 = 7.713  R.sub.32 = 241.400               T.sub.17 = 1.500XV     R.sub.33 = 14.820               T.sub.18 = 3.500  R.sub.34 = -26.098______________________________________ 
    
     The values in the foregoing tables may be adjusted to accommodate normal manufacturing tolerances.