US 3,884,556 Embodiment 3 — Olympus / Nakagawa
| 7 ELEMENTS / 7 GROUPS |
| f ≈ 21.00 mm |
| F/3.5 |
| 2ω ≈ 92° |
| ALL-SPHERICAL |
Unit focus; the full optical cell translates, modeled as a back-focus change from 36.40 mm at infinity to 39.84 mm at 0.20 m.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | 720421 — vintage lanthanum flint (patent nd=1.72000, νd=42.1; no exact public catalog match) |
| L2 | Negative Meniscus | S-PHM52 (OHARA, current equivalent) |
| L3 | Negative Meniscus | S-LAL8 (OHARA) / N-LAK8 class |
| L4 | Biconvex Positive | S-TIM8 (OHARA) / F8 class |
| L5 | Biconcave Negative | SF57 (SCHOTT, legacy dense flint class) |
| L6 | Positive Meniscus | S-PHM52 (OHARA, current equivalent) |
| L7 | Positive Meniscus | S-PHM52 (OHARA, current equivalent) |
Detailed analysis available in the interactive viewer above.