Fast telephoto lens

Claim 2

A fast telephoto lens, which has an F-number of approximately 2.0 to 2.8, consisting of: a first converging lens group; a diverging lens group; and a second converging lens group; said first converging lens group, said diverging lens group and said second converging lens group being arranged in succession from the object side, said first converging lens group and said diverging lens group being arranged to constitute an afocal system with respect to an object at infinity, said diverging lens group being shifted toward an image so as to focus said fast telephoto lens on a close distance object, said first converging lens group including at least two positive lens components and one negative lens component which are sequentially arranged from the object side, said diverging lens group including two negative lens components at least one of which consists of an achromatic lens component constituted by a positive lens and a negative lens, said second converging lens group including at least one achromatic lens component constituted by a negative lens and a positive lens, and said fast telephoto lens satisfying conditions below: 0.7f≦f.sub.1 <f -0.5<(rd+rc)/(rd-rc)<0 where f: overall focal length of said fast telephoto lens f 1 : focal length of said first converging lens group rc: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the object rd: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the image.

Claim 3

A fast telephoto lens according to claim 1, wherein said fast telephoto lens further satisfies conditions below: ##EQU1## where f 2 : focal lenth of said diverging lens group ra: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the object rb: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the image d 4 : a second space in said first converging lens group na: refractive index of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object nb: refractive index of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object νa: Abbe number of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object νb: Abbe number of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object.

Claim 4

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=213.382 d1=23.000 n1=1.49782 ν1=82.3 r2=-738.293 d2=0.300 r3=168.324 d3=23.000 n2=1.49782 ν2=82.3 r4=-848.097 d4=8.200 G1 r5=-531.204 d5=8.100 n3=1.75692 ν3=31.7 r6=41.072 d6=91.540 r7=-7864.019 d7=7.900 n4=1.79886 ν4=34.1 r8=-105.904 d8=3.000 n5=1.51454 ν5=54.6 r9=193.539 d9=10.450 G2 r10=-114.709 d10=3.950 n6=1.46450 ν6=65.8 r11=86.161 d11=31.231 r12=376.118 d12=1.500 n7=1.68893 ν7=31.1 r13=100.0 d13=7.000 n8=1.69350 ν8=53.8 r14=-1707.134 d14=2.000 r15=224.029 d15=2.350 n9=1.69895 ν9=30.1 G3 r16=130.0 d16=8.500 n10=1.69680 ν10=55.6 r17=-205.257 Bf=111.055 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 5

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=396.963 d1=15.00 n1=1.62041 ν1=60.3 r2=-856.209 d2=0.400 r3=169.663 d3=25.00 n2=1.49782 ν2=82.3 r4=-848.700 d4=2.350 r5=-708.000 d5=5.000 n3=1.75692 ν3=31.7 G1 r6=295.194 d6=1.400 r7=171.269 d7=16.000 n4=1.49782 ν4=82.3 r8=686.191 d8=78.913 r9=1756.745 d9=10.000 n5=1.79504 ν5=28.6 r10=-140.240 d10=3.000 n6=1.51454 ν6=54.6 r11=138.770 d11=9.626 G2 r12=-165.595 d12=3.950 n7=1.58913 ν7=61.2 r13=87.786 d13=23.602 r14=628.332 d14=1.500 n8=1.68893 ν8=31.1 r15=130.000 d15=7.000 n9=1.69350 ν9=53.8 r16=-727.144 d16=2.000 r17=254.899 d17=2.350 n10=1.69895 ν10=30.1 G3 r18=127.000 d18=8.500 n11=1.69680 ν11=55.6 r19=-169.604 Bf=110.073 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 6

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=196.956 d1=23.000 n1=1.49782 ν1=82.3 r2=-1307.161 d2=0.300 r3=195.829 d3=23.000 n2=1.49782 ν2=82.3 r4=-516.352 d4=9.035 G1 r5=-380.362 d5=8.100 n3=1.75692 ν3=31.7 r6=721.299 d6=94.902 r7=-2258.410 d7=10.000 n4=1.79886 ν4=34.0 r8=-117.177 d8=2.000 r9=-101.703 d9=3.000 n5=1.46450 ν5=65.8 r10=148.618 d10=20.495 G2 r11=-95.192 d11=5.000 n6=1.69350 ν6=53.8 r12=-61.177 d12=3.950 n7=1.51118 ν7=50.9 r13=93.433 d13=24.547 r14=98.544 d14=10.000 n8=1.62041 ν8=60.3 r15=-121.912 d15=3.300 r16=-261.503 d16=5.000 n9=1.62041 ν9=60.3 r17=-102.467 d17=3.000 r18=-92.976 d18=3.000 n10=1.75520 ν10=27.6 r19=-511.672 d19=8.000 G3 r20=-70.661 d20=3.000 n11=1.80518 ν11=25.4 r21=-94.501 d21=0.090 r22=88.159 d22=10.000 n12=1.60342 ν12=38.1 r23=- 100.000 d23=3.000 n13=1.62041 ν13=60.3 r24=357.774 Bf=46.847 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 7

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f =300 F-number 2.0 ______________________________________ r1=443.373 d1=14.500 n1=1.49782 ν1=82.3 r2=-745.663 d2=0.500 r3=235.410 d3=21.000 n2=1.49782 ν2=82.3 r4=-599.816 d4=6.850 r5=-527.848 d5=6.000 n3=1.74950 ν3=35.2 G1 r6=473.787 d6=1.700 r7=176.900 d7=15.000 n4=1.49782 ν4=82.3 r8=558.189 d8=102.701 r9=749.672 d9=8.000 n5=1.79504 ν5=28.6 r10=-189.496 d10=3.650 n6=1.51454 ν6=54.6 r11=125.271 d11=12.000 G2 r12=-148.765 d12=4.800 n7=1.46450 ν7=65.8 r13=97.985 d13=28.388 r14=-1754.216 d14=1.500 n8=1.68893 ν8=31.1 r15=110.000 d15=7.750 n9=1.69350 ν9=53.8 r16=-317.940 d16=2.000 G3 r17=169.454 d17=2.400 n10=1.69895 ν10=30.1 r18=113.525 d18=8.000 n11=1 69680 ν11=55.6 r19=-254.060 Bf=112.223 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 8

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f = 400 F-number 2.8 ______________________________________ r1=366.543 d1=15.000 n1=1.49782 ν1=82.3 r2=-644.512 d2=.000 r3=213.552 d3=21.000 n2=1.49782 ν2=82.3 r4=-441.810 d4=5.000 r5=-394.853 d5=4.800 n3=1.74950 ν3=35.2 G1 r6=432.180 d6=1.300 r7=156.381 d7=14.000 n4=1.49782 ν4=82.3 r8=1095.641 d8=86.847 r9=-46400.000 d9=7.000 n5=1.78470 ν5=26.1 r10=-139.436 d10=2.500 n6=1.65160 ν6=58.5 r11=128.330 d11=10.000 G2 r12=-172.383 d12=3.500 n7=1.51680 ν7=64.1 r13=104.035 d13=18.449 r14=487.163 d14=1.500 n8=1.67163 ν8=38.9 r15=98.542 d15=10.000 n9=1.59319 ν9=67.9 r16=-100.861 d16=25.500 r17=∞ d17=2.000 n10=1.51680 ν10=64.1 r18=∞ d18=7.700 G3 r19=-161.289 d19=2.800 n11=1.78797 ν11=47.5 r20=-458.625 d20=1.000 r21=609.162 d21=5.700 n12=1.53172 ν12=49.1 r22=-191.968 Bf=111.255 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 9

A fast telephoto lens according to claim 1, characterized by the following data: ______________________________________ f = 400 F-number 2.8 ______________________________________ r1=404.620 d1=12.400 n1=1.49782 ν1=82.3 r2=-739.128 d2=.500 r3=229.061 d3=19.000 n2=1.49782 ν2=82.3 r4=-576.364 d4=6.500 r5=-504.589 d5=5.700 n3=1.74950 ν3=35.2 G1 r6=450.293 d6=1.600 r7=174.251 d7=14.300 n4=1.49782 ν4=82.3 r8=610.132 d8=102.683 r9=774.302 d9=7.500 n5=1.79504 ν5=28.6 r10=-170.747 d10=3.400 n6=1.51454 ν6=54.6 r11=112.007 d11=11.200 G2 r12=-135.143 d12=4.500 n7=1.46450 ν7=65.8 r13=98.477 d13=25.175 r14=537.096 d14=1.500 n8=1.67163 ν8=38.9 r15=109.866 d15=9.700 n9=1.59319 ν9=67.9 r16=-106.723 d16=26.000 r17=∞ d17=2.000 n10=1.51680 ν10=64.1 r18=∞ d18=7.800 G3 r19=-180.104 d19=2.900 n11=1.79631 ν11=41.0 r20=-975.725 d20=1.000 r21=119.226 d21=5.800 n12=1.53172 ν12=49.1 r22=3284.360 Bf=113.852 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 10

A fast telephoto lens, which has an F-number of approximately 2.0 to 2.8, comprising: a first converging lens group; a diverging lens group; and a second converging lens group; said first converging lens group, said diverging lens group and said second converging lens group being arranged in succession from the object side, said first converging lens group and said diverging lens group being arranged to constitute an afocal system with respect to an object at infinity, said diverging lens group being shifted toward an image so as to focus said fast telephoto lens on a close distance object, said first converging lens group including at least two positive lens components and one negative lens component which are sequentially arranged from the object side, said diverging lens group including two negative lens components at least one of which consists of an achromatic lens component constituted by a positive lens and a negative lens, said second converging lens group including at least one achromatic lens component constituted by a negative lens and a positive lens, and said fast telephoto lens satisfying conditions below: ##EQU2## where f: overall focal length of said fast telephoto lens f 1 : focal length of said first converging lens group rc: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being the closest to the object rd: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the image f 2 : focal length of said diverging lens group ra: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the object rb: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the image d 4 : a second space in said first converging lens group na: refractive index of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object nb: refractive index of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object νa: Abbe number of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object νb: Abbe number of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object.

Claim 11

A fast telephoto lens, which has an F-number of approximately 2.0 to 2.8, comprising: a first converging lens group; a diverging lens group; and a second converging lens group; said first converging lens group, said diverging lens group and said second converging lens group being arranged in succession from the object side, said first converging lens group and said diverging lens group being arranged to constitute an afocal system with respect to an object at infinity, said diverging lens group being shifted toward an image so as to focus said fast telephoto lens on a close distance object, said first converging lens group including at least two positive lens components and one negative lens component which are sequentially arranged from the object side, said diverging lens group including two negative lens components at least one of which consists of an achromatic lens component constituted by a positive lens and a negative lens, said second converging lens group including at least one achromatic lens component constituted by a negative lens and a positive lens, and said fast telephoto lens satisfying conditions below: ##EQU2## where f: overall focal length of said fast telephoto lens f 1 : focal length of said first converging lens group rc: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being the closest to the object rd: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the image, the surface being that closest to the image f 2 : focal length of said diverging lens group ra: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the object rb: radius of curvature of a surface of the negative lens component of said diverging lens group that is located nearer the object, the surface being that closest to the image d 4 : a second space in said first converging lens group na: refractive index of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object nb: refractive index of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object νa: Abbe number of the positive lens of the achromatic component of said diverging lens group, the positive lens being located near the object νb: Abbe number of the negative lens of the achromatic component of said diverging lens group, the negative lens being located near the object.

Claim 12

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=213.382 d1=23.000 n1=1.49782 ν1=82.3 r2=-738.293 d2=0.300 r3=168.324 d3=23.000 n2=1.49782 ν2=82.3 r4=-848.097 d4=8.200 G1 r5=-531.204 d5=8.100 n3=1.75692 ν3=31.7 r6=41.072 d6=91.540 r7=-7864! 019 d7=7.900 n4=1.79886 ν4=34.1 r8=-105.904 d8=3.000 n5=1.51454 ν5=54.6 r9=193.539 d9=10.450 G2 r10=-114.709 d10=3.950 n6=1.46450 ν6=65.8 r11=86.161 d11=31.231 r12=376.118 d12=1.500 n7=1.68893 ν7=31.1 r13=100.0 d13=7.000 n8=1.69350 ν8=53.8 r14=-1707.134 d14=2.000 r15=224.029 d15=2.350 n9=1.69895 ν9=30.1 G3 r16=130.0 d16=8.500 n10=1.69680 ν10=55.6 r17=-205.257 Bf=111.055 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 13

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=396.963 d1=15.00 n1=1.62041 ν1=60.3 r2=-856.209 d2=0.400 r3=169.663 d3=25.00 n2=1.49782 ν2=82.3 r4=-848.700 d4=2.350 r5=-708.000 d5=5.000 n3=1.75692 ν3=31.7 G1 r6=295.194 d6=1.400 r7=171.269 d7=16.000 n4=1.49782 ν4=82.3 r8=686.191 d8=78.913 r9=1756.745 d9=10.000 n5=1.79504 ν5=28.6 r10=-140.240 d10=3.000 n6=1.51454 ν6=54.6 r11=138.770 d11=9.626 G2 r12=-165.595 d12=3.950 n7=1.58913 ν7=61.2 r13=87.786 d13=23.602 r14=628.332 d14=1.500 n8=1.68893 ν8=31.1 r15=130.000 d15=7.000 n9=1.69350 ν9=53.8 r16=-727.144 d16=2.000 G3 r17=254.899 d17=2.350 n10=1.69895 ν10=30.1 r18=127.000 d18=8.500 n11=1.69680 ν11=55.6 r19=-169.604 Bf=110.073 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 14

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=196.956 d1=23.000 n1=1.49782 ν1=82.3 r2=-1307.161 d2=0.300 r3=195.829 d3=23.000 n2=1.49782 ν2=82.3 r4=-516.352 d4=9.035 G1 r5=-380.362 d5=8.100 n3=1.75692 ν3=31.7 r6=721.299 d6=94.902 r7=-2258.410 d7=10.000 n4=1.79886 ν4=34.0 r8=-117.177 d8=2.000 r9=-101.703 d9=3.000 n5=1.46450 ν5=65.8 r10=148.618 d10=20.495 G2 r11=-95.192 d11=5.000 n6=1.69350 ν6=53.8 r12=-61.177 d12=3.950 n7=1.51118 ν7=50 9 r13=93.433 d13=24.547 r14=98.544 d14=10.000 n8=1.62041 ν8=60.3 r15=-121.912 d15=3.300 r16=-261.503 d16=5.000 n9=1.62041 ν9=60.3 r17=-102.467 d17=3.000 r18=-92.976 d18=3.000 n10=1.75520 ν10=27.6 r19=-511.672 d19=8.000 G3 r20=-70.661 d20=3.000 n11=1.80518 ν11=25.4 r21=-94.501 d21=0.090 r22=88.159 d22=10.000 n12=1.60342 ν12=38.1 r23= -100.000 d23=3.000 n13=1.62041 ν13=60.3 r24=357.774 Bf=46.847 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 15

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 300 F-number 2.0 ______________________________________ r1=443.373 d1=14.500 n1=1.49782 ν1=82.3 r2=-745.663 d2=0.500 r3=235.410 d3=21.000 n2=1.49782 ν2=82.3 r4=-599.816 d4=6.850 r5=-527.848 d5=6.000 n3=1.74950 ν3=35.2 G1 r6=473.787 d6=1.700 r7=176.900 d7=15.000 n4=1.49782 ν4=82.3 r8=558.189 d8=102.701 r9=749.672 d9=8.000 n5=1.79504 ν5=28.6 r10=-189.496 d10=3.650 n6=1.51454 ν6=54.6 r11=125.271 d11=12.000 G2 r12=-148.765 d12=4.800 n7=1.46450 ν7=65.8 r13=97.985 d13=28.388 r14=-1754.216 d14=1.500 n8=1.68893 ν8=31.1 r15=110.000 d15=7.750 n9=1.69350 ν9=53.8 r16=-317.940 d16=2.000 r17=169.454 d17=2.400 n10=1.69895 ν10=30.1 G3 r18=113.525 d18=8.000 n11=1.69680 ν11=55.6 r19=-254.060 Bf=112.223 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 16

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 400 F-number 2.8 ______________________________________ r1=366.543 d1=15.000 n1=1.49782 ν1=82.3 r2=-644.512 d2=.000 r3=213.552 d3=21.000 n2=1.49782 ν2=82.3 r4=-441.810 d4=5.000 r5=-394.853 d5=4.800 n3=1.74950 ν3=35.2 G1 r6=432.180 d6=1.300 r7=156.381 d7=14.000 n4=1.49782 ν4=82.3 r8=1095.641 d8=86.847 r9=-46400.000 d9=7.000 n5=1.78470 ν5=26.1 r10=-139.436 d10=2.500 n6=1.65160 ν6=58.5 r11=128.330 d11=10.000 G2 r12=-172.383 d12=3.500 n7=1.51680 ν7=64.1 r13=104 035 d13=18.449 r14=487.163 d14=1.500 n8=1.67163 ν8=38.9 r15=98.542 d15=10.000 n9=1.59319 ν9=67.9 r16=-100.861 d16=25.500 r17=∞ d17=2.000 n10=1.51680 ν10=64.1 r18=∞ d18=7.700 G3 r19=-161.289 d19=2.800 n11=1.78797 ν11=47.5 r20=-458.625 d20=1.000 r21=609.162 d21=5.700 n12=1.53172 ν12=49.1 r22=-191.968 Bf=111.255 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.

Claim 17

A fast telephoto lens according to claim 9, characterized by the following data: ______________________________________ f = 400 F-number 2.8 ______________________________________ r1=404.620 d1=12.400 n1=1.49782 ν1=82.3 r2=-739.128 d2=.500 r3=229.061 d3=19.000 n2=1.49782 ν2=82.3 r4=-576.364 d4=6.500 r5=-504.589 d5=5.700 n3=1.74950 ν3=35.2 G1 r6=450.293 d6=1.600 r7=174.251 d7=14.300 n4=1.49782 ν4=82.3 r8=610.132 d8=102.683 r9=774.302 d9=7.500 n5=1.79504 ν5=28.6 r10=-170.747 d10=3.400 n6=1.51454 ν6=54.6 r11=112.007 d11=11.200 G2 r12=-135.143 d12=4.500 n7=1.46450 ν7=65.8 r13=98.477 d13=25.175 r14=537.096 d14=1.500 n8=1.67163 ν8=38.9 r15=109.866 d15=9.700 n9=1.59319 ν9=67.9 r16=-106.723 d16=26.000 r17=∞ d17=2.000 n10=1.51680 ν10=64.1 r18=∞ d18=7.800 G3 r19=-180.104 d19=2.900 n11=1.79631 ν11=41.0 r20=-975.725 d20=1.000 r21=119.226 d21=5.800 n12=1.53172 ν12=49.1 r22=3284.360 Bf=113.852 ______________________________________ where r1, r2, r3, . . . are radii of curvature of successive lens surfaces in order from the object side; d1, d2, d3, . . . are thicknesses at the centers of respective lenses and lens distances in order from the object side; n1, n2, n3, . . . are refractive indices of respective lenses with respect to the d-line (λ=587.6 nm) in order from the object side; ν1, ν2, ν3, . . . are the Abbe numbers of respective lenses in order from the object side; and Bf is the back focal length of the telephoto lens.