Photographic lens of continuously variable focal length

Details Photographic lens of continuously variable focal length Photographic lens of continuously variable focal length

1982-09-23

1984-05-29

Corbin, John K.

350423, G02B 704, G02B 1500

Patent

active

044511248

ABSTRACT:
A photographic lens of continuously variable focal length (i.e., a zoom lens) consisting of four lens groups designated from front to rear as groups A, B, C, and D. Group B has diverging refractive power; the other three have converging power. An iris diaphragm is located between groups B and C. Group C has a focal length which is numerically greater (disregarding difference in sign) than the focal length of group B by a factor not less than 1.42 and not more than 1.73. Lens group D is formed of two parts D.sub.1 and D.sub.2, separated from each other by a clear air space. The first part D.sub.1 has negative power; the second part D.sub.2 has positive power. The focal length of the part D.sub.1 is numerically greater (disregarding the difference in sign) than the focal length of group C by a factor not less than 1.16 and not more than 1.42.

REFERENCES:
patent: 3584935 (1971-06-01), Kojima
patent: 3658411 (1972-04-01), Price
patent: 4270848 (1981-06-01), Angenieux

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