JP S56-158314 A — Akiyoshi Nakamura
| 10 ELEMENTS / 10 GROUPS |
| f ≈ 24.6–34.1 mm |
| F/3.5 |
| 2ω ≈ 84.2°–65.3° |
| ALL SPHERICAL |
Front group I (L1–L4) extends as a unit by about 4.1 mm while group II and the image plane stay fixed. Close-focus spacings are a paraxial reconstruction for 0.3 m from the film plane, not patent data.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | S-BAL35 (OHARA) |
| L2 | Negative Meniscus | S-LAH53 (OHARA) class — Close (patent 805410, Δnd +0.0011) |
| L3 | Biconcave Negative | S-LAH53 (OHARA) class — Close (patent 805410, Δnd +0.0011) |
| L4 | Positive Meniscus | S-TIH6 (OHARA) |
| L5 | Positive Meniscus | LAC13 (HOYA) |
| L6 | Biconvex Positive | BAF10 (HOYA) |
| L7 | Positive Meniscus | BACD4 (HOYA) — Close (613585) |
| L8 | Biconcave Negative | S-TIH6 (OHARA) |
| L9 | Positive Meniscus | E-C3 (HOYA) |
| L10 | Biconvex Positive | Unmatched (526521 crown/light-flint boundary; nearest HOYA CF2 at Δnd +0.0005, Δνd −1.0) |