Wide angle zoom lens system
AssigneeFuji Photo Optical Co., Ltd.
InventorKazunori Ohno
Life of this patent
Estimating the term…
Abstract
A zoom lens system comprises a front meniscus lens of negative power and a rear meniscus lens of positive power which are shifted along an optical axis of the zoom lens system to change a relative axial distance so as to achieve zooming continuously from a wide angle end to a telephoto end and satisfies the following condition: 1.85<f.sub.1 /f.sub.2 <-1.5 where f.sub.1 and f.sub.2 are the focal length of the front and rear meniscus lenses, respectively.
Claims4
A zoom lens system comprising in order from the object end to the image end a front meniscus lens element of negative power and a rear meniscus lens element of positive power, the front and rear meniscus lens elements being shifted along an optical axis of the zoom lens system to change a relative axial distance between the front and rear meniscus lens elements so as to achieve zooming continuously from a wide angle photographic end to a telephotographic end, the zoom lens system satisfying the following condition:
- -1.85<f.sub.1 /f.sub.2 <-1.5
- where f.sub.1 and f.sub.2 are the focal length of the front and rear meniscus lenses, respectively,
- wherein said rear meniscus lens element has an object end aspheric surface and an image end aspheric surface, each aspheric surface being defined by the following relationship:
- ##EQU2## where X is the surface sag at a semi-aperture distance y from the optical axis X of the lens system, C is the curvature of a lens surface at the optical axis X equal to the reciprocal of the radius at the optical axis, K is a conic constant, and a1-a4 are aspheric coefficients, said zoom lens system being scaled to an image frame of 24.times.36 mm substantially as follows:
- ______________________________________ Radius of Axial Distance Element Curvature (mm) Between Surfaces (mm) Nd .nu. ______________________________________ S1 R.sub.1 = 94.310 L1 d.sub.1 = 1.5 1.49116 57.6 S2 R.sub.2 = 13.333 d.sub.2 = variable S3 R.sub.3 = 5.258 L2 d.sub.3 = 4.499 1.49116 57.6 S4 R.sub.4 = 9.628 ______________________________________ Aspheric Surface:
- S3 and S4 Aspheric Parameters:
- S3 S4 ______________________________________ C 0.190186 0.10386 K -0.26458 4.53346 a1 -0.22457 .times. 10.sup.-4 -0.56536 .times. 10.sup.-3 a2 0.83591 .times. 10.sup.-4 0.18961 .times. 10.sup.-2 a3 -0.74073 .times. 10.sup.-5 -0.10037 .times. 10.sup.-2 a4 0.34929 .times. 10.sup.-6 0.19060 .times. 10.sup.-3 ______________________________________ Zooming Parameters:
- FL (mm) d.sub.2 Ld ______________________________________ EDW 21.00 15.36 45.64 EDM 29.73 7.53 42.64 EDT 35.00 4.69 42.72 ______________________________________
- where the zoom lens system comprises lens elements L1 and L2 having surfaces S1 and S4 and surface radii R1 and R4, d.sub.1 to d.sub.3 are the axial distances, the index of refraction is given by Nd, the dispersion is defined by the Abbe No. as given by .nu., FL is the overall focal length of the zoom lens system for the wide angle end (EDW), the middle position (EDM) and the telephoto end (EDT).
A zoom lens system comprising in order from the object and to the image end a front meniscus lens element of negative power and a rear meniscus lens element of positive power, the front and rear meniscus lens elements being shifted along an optical axis of the zoom lens system to change a relative axial distance between the front and rear meniscus lens elements so as to achieve zooming continuously from a wide angle photographic end to a telephotographic end, the zoom lens system satisfying the following condition:
- -1.85<f.sub.1 /f.sub.2 <-1.5
- where f.sub.1 and f.sub.2 are the focal length of the front and rear meniscus lenses, respectively,
- wherein said rear meniscus lens element has an object end aspheric surface and an image end aspheric surface, each aspheric surface being defined by the following relationship:
- ##EQU3## where X is the surface sag at a semi-aperture distance y from the optical axis X of the lens system, C is the curvature of a lens surface at the optical axis X equal to the reciprocal of the radius at the optical axis, K is a conic constant, and a1-a4 are aspheric coefficients, said zoom lens system being scaled to an image frame of 24.times.36 mm substantially as follows:
- ______________________________________ Radius of Axial Distance Element Curvature (mm) Between Surfaces (mm) Nd .nu. ______________________________________ S1 R.sub.1 = 50.4 L1 d.sub.1 = 1.5 1.49116 57.6 S2 R.sub.2 = 9.808 d.sub.2 = variable S3 R.sub.3 = 4.554 L2 d.sub.3 = 3.866 1.49116 57.6 S4 R.sub.4 = 9.138 ______________________________________ Aspheric Surface:
- S3 and S4 Aspheric Parameters:
- S3 S4 ______________________________________ C 0.219587 0.10943 K 0.27841 4.63573 a1 -0.91474 .times. 10.sup.-3 -0.28051 .times. 10.sup.-3 a2 0.14263 .times. 10.sup.-3 0.20679 .times. 10.sup.-2 a3 -0.18187 .times. 10.sup.-4 -0.11558 .times. 10.sup.-2 a4 0.73193 .times. 10.sup.-6 0.24183 .times. 10.sup.-3 ______________________________________ Zooming Parameters:
- FL (mm) d.sub.2 Ld ______________________________________ EDW 18.00 11.801 37.96 EDM 23.83 6.868 36.38 EDT 35.00 2.003 37.96 ______________________________________
- where the zoom lens system comprises lens elements L1 and L2 having surfaces S1 and S4 and surface radii R1 and R4, d.sub.1 to d.sub.3 are the axial distances, the index of refraction is given by Nd, the dispersion is defined by the Abbe No. as given by .nu., FL is the overall focal length of the zoom lens system for the wide angle photography (EDW), the middle position (EDM) and the telephoto end (EDT).
A zoom lens system comprising in order from the object and to the image end a front meniscus lens element of negative power and a rear meniscus lens element of positive power, the front and rear meniscus lens elements being shifted along an optical axis of the zoom lens system to change a relative axial distance between the front and rear meniscus lens elements so as to achieve zooming continuously from a wide angle photographic end to a telephotographic end, the zoom lens system satisfying the following condition:
- -1.85<f.sub.1 /f.sub.2 <-1.5
- where f.sub.1 and f.sub.2 are the focal length of the front and rear meniscus lenses, respectively,
- wherein said rear meniscus lens element has an object end aspheric surface and an image end aspheric surface, each aspheric surface being defined by the following relationship:
- ##EQU4## where X is the surface sag at a semi-aperture distance y from the optical axis X of the lens system, C is the curvature of a lens surface at the optical axis X equal to the reciprocal of the radius at the optical axis, K is a conic constant, and a1-a4 are aspheric coefficients, said zoom lens system being scaled to an image frame of 24.times.36 mm substantially as follows:
- ______________________________________ Radius of Axial Distance Element Curvature (mm) Between Surfaces (mm) Nd .upsilon. ______________________________________ S1 R.sub.1 = 37.406 L1 d.sub.1 = 1.5 1.49116 57.6 S2 R.sub.2 = 10.025 d.sub.2 = variable S3 R.sub.3 = 4.207 L2 d.sub.3 = 2.270 1.49116 57.6 S4 R.sub.4 = 6.759 ______________________________________ Aspheric Surface:
- S1, S2, S3 and S4 Aspheric Parameters:
- S1 S2 S3 S4 ______________________________________ C 0.02674 0.09975 0.23770 0.14795 K 3.40389 -0.22785 1.28056 6.74359 a1 -0.48894 .times. 0.10231 .times. -0.93197 .times. 0.24192 .times. 10.sup.-4 10.sup.-3 10.sup.-3 10.sup.-2 a2 -0.96192 .times. -0.12487 .times. -0.18598 .times. -0.25293 .times. 10.sup.-7 10.sup.-5 10.sup.-3 10.sup.-2 a3 0 -0.70536 .times. 0.61481 .times. 0.13952 .times. 10.sup.-8 10.sup.-5 10.sup.-2 a4 0 0 -0.46908 .times. -0.24267 .times. 10.sup.-5 10.sup.-3 ______________________________________ Zooming Parameters:
- FL (mm) d.sub.2 Ld ______________________________________ EDW 26.00 10.62 44.88 EDM 32.96 6.58 45.14 EDT 45.00 2.53 48.54 ______________________________________
- where the zoom lens system comprises lens elements L1 and L2 having surfaces S1 and S4 and surface radii R1 and R4, d.sub.1 to d.sub.3 are the axial distances, the index of refraction is given by Nd, the dispersion is defined by the Abbe No. as given by .nu., FL is the overall focal length of the zoom lens system for the wide angle end (EDW), the middle position (EDM) and the telephoto end (EDT).
Dependencies are inferred from the claim text.