US 716,035 — Harting / Voigtländer & Sohn AG (1902)
| 5 ELEMENTS / 3 GROUPS |
| f = 100 (normalized) |
| F/4.0 |
| 2ω ≈ 43.6° |
| ALL SPHERICAL |
Unit focus — entire lens moves via bellows extension or helicoid. Air gaps between groups remain constant. Patent does not specify close focus; 1.0 m assumed for a 100 mm focal length interpretation.
| Element | Type | Glass |
|---|---|---|
| La | Negative Meniscus | Light Flint (LF, probable discontinued Schott type) |
| Lb | Biconvex Positive | Dense Crown (SK, high-confidence match: Schott N-SK2, Δnd = 0.0006) |
| Lc | Biconcave Negative | Light Flint (LF, same glass as elements a/a′) |
| Lb' | Biconvex Positive | Dense Crown (SK, Schott N-SK2) |
| La' | Negative Meniscus | Light Flint (LF, same glass as elements a/c) |
Detailed analysis available in the interactive viewer above.