FR 1,471,493, sole example
| 7 elements / 5 groups |
| f ≈ 35.1 mm |
| 1:2.8 |
| 2ω ≈ 63.3° |
| all spherical |
Unit focusing. The patent publishes only the infinity prescription; close focus is approximated as rear BF extension to 0.30 m.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | FK5 / N-FK5 class (Schott legacy; patent n_e) |
| L2 | Biconvex Positive | BaSF6 class; J-BASF6 catalog e-line spectral proxy (production supplier unspecified) |
| L3 | Negative Meniscus | Unmatched (flint/barium-flint position; no confident public catalog match; patent n_e) |
| L4 | Biconvex Positive | Unmatched (SK16-class patent e-line value; no verified d-line catalog identity) |
| L5 | Biconcave Negative | Unmatched (dense flint; no confident public catalog match; patent n_e) |
| L6 | Negative Meniscus | Unmatched (BaF13-class patent e-line value; no verified d-line catalog identity) |
| L7 | Biconvex Positive | Unmatched (LAK9-class lanthanum crown; patent e-line value stored) |