US 2,084,309 — Ludwig Bertele
| 7 elements / 4 groups |
| f = 35.0 mm |
| f/2.8 |
| 63.4° diagonal field |
| all-spherical |
Unit-focus rendering model. The patent gives only an infinity prescription; close focus uses a 1.0 m visualization assumption and varies only the back focus.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | N-BAF10 (Schott catalog-equivalent to vintage 672472 coordinate; supplier not identified) |
| L2 | Positive Meniscus | N-BAF10 (Schott catalog-equivalent to vintage 672472 coordinate; supplier not identified) |
| L3 | Plano-Convex | FK3 (Schott) |
| L4 | Plano-Concave | SF8 / N-SF8 equivalent (Schott) |
| L5 | Negative Meniscus | FK3 (Schott) |
| L6 | Biconvex Positive | N-BAF10 (Schott catalog-equivalent to vintage 672472 coordinate; supplier not identified) |
| L7 | Negative Meniscus | S-TIL6 catalog equivalent (patent 533489; production supplier unspecified) |