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PARALLEL PROCESSING tools for today's optiker
Handbook of Chemistry and Physics, 67th ed. (CRC Press, Boca Raton, FL, 1986).
7. The simulations reported in this article were performed by MULTILAYER™, a product of MM Research Inc., Tucson, A Z .
8. C.G.B. Garrett and D.E. McCumber, "Propagation of a Gaussian light pulse through an anomalous disper
sion medium," Phys. Rev. A 1, 305 (1970).
9. S. Chu and S. Wong, "Linear pulse propagation in an absorbing medium," Phys. Rev. Lett. 49 , 1293 (1982).
10. R.Y. Chiao et al. , "Faster than light?" Sci . Am. 269 (2), 52 -60 , 1993.
11. R.Y. Chiao and A . M . Steinberg,
"Tunneling times and superluminality," Progress in Optics, E. Wolf, ed. 37 (Elsevier, Amsterdam, Holland, 1997), pp. 347-406 .
OPN Contributing Editor Masud Mansuripur ([email protected]) is professor and Ewan M. Wright is associate professor of Optical Sciences at the Univ. of Arizona In Tucson, AZ.
Patent Design
Wide-angle Soft Focus
Photographic Lens
BY J. BRIAN CALDWELL
Patent: U.S. 5,822,132 Issued: October 13, 1998 Title: Soft Focus Lens Example: #3 of 4 Inventor: Jun Hirakawa Assignee: Asahi Kogaku
Kabushiki Kaisha
When a lens designer sets out to design a photographic objec
tive the usual goal is to produce the sharpest possible lens by optimally minimizing all aberrations. However, this is not the case with lenses intended for portrait photography. A well-corrected lens will ruthlessly reveal all facial blemishes and wrinkles, and many people find this disturbing. As Arthur Cox put it, "portrait work, especially commercial or professional portrait work, is as much subtle flattery as photography."1 The best alternative is to use a special soft focus lens having a large amount of spherical aberration. A point image produced by such a lens will consist of a fairly small core sur
rounded by a large halo. And, since this effect is stable in the presence of moderate amounts of defocus, the depth-of-field is larger than that of a well-corrected lens. The small core ensures that high-contrast, fine detail remains visible, while the large halo tends to blend away blemishes and wrinkles.
Soft focus lenses are usually available only in moderately long focal lengths because they are intended exclusively for portraiture. This month's design (see Fig. 1) is unusual—though not unprecedented—in that it is a wide-angle soft focus lens intended for landscape photography. Canon patented a wide-angle to short telephoto zoom lens having a variable soft focus function back in the 1980s,2 although this patent is not cited in the patent document for this month's design.
The current design is a fairly conventional-looking reverse tele-photo lens, covering a full field angle of 68.4°. The transverse ray aberration plots shown in Figure 2, however, reveal a large amount of
undercorrected spherical aberration. The aperture is f/3.6 and the optical prescription is given in Table 1.
References 1. A. Cox, "Optics: The technique of
definition," The Focal Press, p. 161 (1961).
2. T. Tanaka et al., "Zoom lens having a capability of introducing special features into image formats," U.S. Patent 4,781,446 issued Nov. 1, 1988.
OPN Contributing Editor J. Brian Caldwell is president of Optical Data Solutions Inc., which produces LensVIEW™, a database of optical designs found in the patent literature. Comments and suggestions are welcome at [email protected].
Figure 1. Wide-angle soft focus lens.
Figure 2. Transverse ray aberrations in millimeters for semi-field angles of 0.0, 23.9, and 34 .2° .
Table 1. Optical prescription for the objective, where measurements are given in millimeters. Focal length is 100 mm, aperture is f/3.6, full field-of-view is 68 .4° .
Optics & Photonics News/January 1999 49
