US 3,864,027, Example 1 — Kenichi Harada
| 5 ELEMENTS / 5 GROUPS |
| DESIGN f = 400 mm |
| DESIGN F/6.3 |
| ALL SPHERICAL |
| TELEPHOTO RATIO 0.75 |
Unit focus: the whole lens moves forward and only the back focus changes, by 39.99 mm at the 5 m minimum focus. The patent prints no focus travel; the motion is inferred from its Fig. 5 curves at 1/10× magnification, which extending Example 1 as a unit reproduces. At the 400 mm scale that magnification falls at 5.0 m object to image, the catalogue minimum focus. The same catalogue lists a straight helicoid for focusing, which fits unit movement without proving it. The infinity back focus is the computed paraxial value; the patent prints none.
| Element | Type | Glass |
|---|---|---|
| L1 | Biconvex Positive | S-FSL5 (OHARA catalog equivalent; production supplier unspecified) |
| L2 | Negative Meniscus | J-LAF7 (HIKARI, coordinate equivalent) |
| L3 | Plano-Concave Negative | FF5 (HOYA catalog equivalent; production supplier unspecified) |
| L4 | Biconcave Negative | S-LAL54Q (OHARA catalog equivalent; production supplier unspecified) |
| L5 | Biconvex Positive | F5 (SCHOTT, coordinate equivalent) |