Long-focus color-corrected petzval-type optical objective

Claim 2

A optical objective of net positive dioptric power, said objective having an image plane at which four discrete wavelength come to a common focus, said optical objective comprising: (a) a first lens group consisting of five lens elements, (b) a second lens group consisting of four lens elements, and (c) a field flattener consisting of one lens element, all of said lens elements being disposed along an optic axis, each of said lens elements being rotationally symmetric with respect to said optic axis, said second group of lens elements being separated from said first group of lens elements along said optic axis by an aperture stop, said field flattener being located adjacent said image plane, said lens elements being made from only two different optical glasses, at least one of said lens elements being made from a first one of said optical glasses, at least one other of said lens elements being made from a second one of said optical glasses.

Claim 3

The optical objective of claim 1 wherein said first and second lens group are disposed on opposite sides of an aperture stop of said objective; and wherein said first lens group comprises in successive disposition along said optic axis: (a) a first positive lens element made of said first one of said optical glasses, (b) a second positive lens element made of said first one of said optical glasses, (c) a first negative lens element made of second one of said optical glasses, (d) a second negative lens element made of said second one of said optical glasses, and (e) a third positive lens element made of first one of said optical glasses; wherein said second lens group comprises in successive disposition along said optic axis: (a) a fourth positive lens element made of said first one of said optical glasses, (b) a third negative lens element made of said second one of said optical glasses, (c) a fourth negative lens element made of said second one of said optically glasses, and (d) a fifth positive lens element made of said first one of said optical glasses; and wherein said field flattener lens element is made of said second one of said optical glasses.

Claim 4

The optical objective of claim 2 wherein said first one of said optical glasses has an index of refraction of approximately 1.457 and an Abbe number of approximately 90.77 at a base wavelength of 0.58756 micron, and wherein said second one of said optical glasses has an index of refraction of approximately 1.697 and an Abbe number of approximately 55.46 at said base wavelength.

Claim 5

The optical objective of claim 3 wherein said first one of said optical glasses is Hoya FCD10 glass, and wherein said second one of said optical glasses is Hoya LAC14 glass.

Claim 6

The optical objective of claim 4 having a design form optimized for a focal length of 1000 millimeters at a relative aperture of f/2 and a field of view of 4.2° substantially as follows: ______________________________________ Surface Radius Thickness No. (mm) (mm) Material ______________________________________ 1 1927.867 93.759 FCD10 2 -1648.146 283.367 Air 3 2595.537 87.508 FCD10 4 -846.041 2.937 Air 5 -818.691 37.504 LAC14 6 -8142.226 25.522 Air 7 -1209.561 37.504 LAC14 8 8985.894 13.345 Air 9 811.630 87.508 FCD10 10 -2010.034 616.910 Air 11 Aperture stop 261.426 Air 12 286.573 50.005 FCD10 13 -513.710 15.006 Air 14 -324.409 25.002 LAC14 15 -706.264 19.622 Air 16 3455.771 25.002 LAC14 17 603.169 12.772 Air 18 386.595 50.005 FCD10 19 -303.879 71.919 Air 20 -243.729 25.002 LAC14 21 388.414 13.633 Air 22 Image plane ______________________________________

Claim 7

The optical objective of claim 5 having an actual focal length different from 1000 millimeters, said lens elements having actual surface radii of curvature and actual axial thicknesses and spacings that are obtained from values tabulated in claim 5 by multiplying said values by a scaling factor, said scaling factor being the ratio of said actual focal length to said 1000 millimeter focal length for which said tabulated values are optimized.

Claim 8

The optical objective of claim 2 wherein said first one of said optical glasses has an index of refraction of approximately 1.486 and an Abbe number of approximately 81.70 at a base wavelength of 0.58756 micron, and wherein said second one of said optical glasses has an index of refraction of approximately 1.697 and an Abbe number of approximately 55.40 at said base wavelength.

Claim 9

The optical objective of claim 7 wherein said first one of said optical glasses is Corning-France 486817 glass, and wherein said second one of said optical glasses in Corning-France 697554 glass.

Claim 10

The optical objective of claim 8 having a design form optimized for a focal length of 1000 millimeters at a relative aperture of f/2 and a field of view of 4.2° substantially as follows: ______________________________________ Surface Radius Thickness No. (mm) (mm) Material ______________________________________ 1 1930.696 93.727 486817 2 -1985.752 157.321 Air 3 2169.018 87.478 486817 4 -945.731 3.537 Air 5 -917.788 24.994 697554 6 3781.912 44.989 Air 7 -1209.273 24.994 697554 8 173343.000 1.499 Air 9 914.125 87.478 486817 10 -2319.675 778.803 Air 11 Aperture stop 78.869 Air 12 396.283 42.763 486817 13 -523.510 9.781 Air 14 -444.264 19.995 697554 15 -4227.905 30.275 Air 16 -3374.885 19.995 697554 17 812.577 9.668 Air 18 334.555 42.764 486817 19 -699.814 225.937 Air 20 -249.564 12.544 697554 21 2177.730 44.148 Air 22 Image plane ______________________________________

Claim 11

The optical objective of claim 9 having an actual focal length different from 1000 millimeters, said lens elements having actual surface radii of curvature and actual axial thicknesses and spacings that are obtained from values tabulated in claim 9 by multiplying said values by a scaling factor, said scaling factor being the ratio of said actual focal length to said 1000 millimeter focal length for which said tabulated values are optimized.

Claim 12

The optical objective of claim 2 wherein said first one of said optical glasses has an index of refraction of approximately 1.457 and an Abber number of approximately 90.77 at a base wavelength of 0.58756 micron, and wherein said second one of said optical glasses has an index of refraction of approximately 1.697 an an Abbe number of approximately 55.40 at said base wavelength.

Claim 13

The optical objective of claim 11 wherein said first one of said optical glasses in Hoya FCD10 glass, and wherein said second one of said optical glasses is Corning-France 697554 glass.

Claim 14

The optical objective of claim 12 having a design form optimized for a focal length of 1000 millimeters at a relative aperture of f/2 and a field of view of 4.2° substantially as follows: ______________________________________ Surface Radius Thickness No. (mm) (mm) Material ______________________________________ 1 1944.442 93.749 FCD10 2 -1644.700 283.323 Air 3 2621.252 87.499 FCD10 4 -842.841 2.937 Air 5 -815.785 37.499 697554 6 -7785.324 25.508 Air 7 -1200.218 37.499 697554 8 9621.081 13.108 Air 9 814.132 87.499 FCD10 10 -1982.644 615.906 Air 11 Aperture stop 261.114 Air 12 290.575 49.999 FCD10 13 -509.072 15.004 Air 14 -323.019 25.000 697554 15 -700.858 19.621 Air 16 3240.492 25.000 697554 17 624.813 12.770 Air 18 391.217 49.999 FCD10 19 -305.380 71.391 Air 20 -246.544 25.000 697554 21 380.407 14.886 Air 22 Image plane ______________________________________

Claim 15

The optical objective of claim 13 having an actual focal length different from 1000 millimeters, said lens elements having actual surface radii of curvature and acutal axial thicknesses and spacings that are obtained from values tabulated in claim 13 by multiplying said values by a scaling factor, said scaling factor being the ratio of said actual focal length to said 1000 millimeter focal length for which said tabulated values are optimized.