US 2,819,651 — Carl Baur, Christian Otzen
| 5 elements / 3 groups |
| f ≈ 90.0 mm |
| F/4 |
| 2ω = 30° patent field |
| All spherical |
Unit focus by helicoid; close focus modeled as back-focus increase from 33.52 mm to 38.61 mm.
| Element | Type | Glass |
|---|---|---|
| L1 | Biconvex Positive | BK7 (Schott legacy / N-BK7 class) |
| L2 | Biconcave Negative | BASF1 / BAM21 class (legacy barium flint, 626/391) |
| L3 | Positive Meniscus | KzF4 class (Schott-Jena legacy short flint, 570/481) |
| L4 | Biconcave Negative | KF3 (SUMITA catalog equivalent for patent coordinate; production supplier unspecified) |
| L5 | Biconvex Positive | BAM5 class (barium middle glass, 607/492) |