US 4,398,807 A — Yutaka Iizuka
| 12 ELEMENTS / 9 GROUPS |
| DESIGN f = 75.02-150.09 mm |
| DESIGN F/3.5 |
| ALL SPHERICAL |
Front-group focusing: only the first group (L1-L3) moves toward the object, by about 14.7 mm at every zoom setting, while the other groups and the image plane stay fixed. The patent states the 1 m minimum distance and prints close-range plots with magnifications of -0.104, -0.147 and -0.208, but no close-focus spacings. The close spacings here are solved for a 1 m object-to-film distance and reproduce those magnifications; the patent's near state is the same as Nikon's marketed 1 m minimum focus.
| Element | Type | Glass |
|---|---|---|
| L1 | Biconvex Positive | N-SK16 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L2 | Biconvex Positive | N-SK16 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L3 | Biconcave Negative | E-FD4 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L4 | Positive Meniscus | SF56A (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L5 | Biconcave Negative | N-BK7 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L6 | Biconcave Negative | N-SK16 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L7 | Biconvex Positive | N-SK16 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L8 | Negative Meniscus | E-FD4 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L9 | Positive Meniscus | N-SK16 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L10 | Biconcave Negative | E-FD4 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L11 | Negative Meniscus | LAFN7 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |
| L12 | Biconvex Positive | F1 (coordinate-compatible spectral proxy; supplier and melt unconfirmed) |