US 4,457,596 — Koichi Wakamiya
| 5 ELEMENTS / 4 GROUPS |
| f ≈ 35.0 mm |
| F/2.8 |
| 2ω ≈ 62.3° |
| ALL SPHERICAL |
Unit focus — entire lens translates forward on helicoid; BFD increases by 1.60 mm at 0.8 m.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | N-LAK8 (Schott catalog-equivalent to patent LaK 8; production melt unspecified) |
| L2 | Positive Meniscus | S-LAH66 (OHARA) |
| L3 | Biconcave Negative | S-TIM28 (OHARA; exact 689311 coordinate match) |
| L4 | Biconvex Positive | S-LAH66 (OHARA) |
| L5 | Negative Meniscus | SK 16 / S-BSM16 (1620/604) |