US 6,115,188 A — Akihiro Nishio, Hideki Ogawa, Makoto Misaka
| 400mm f/2.8 (marketed) |
| Patent f = 392.15 mm, F/2.9 |
| 17 elements / 13 groups marketed; 16 / 12 modeled after rear-filter omission |
| 3.0 m minimum focus |
| 1 fluorite + 2 UD elements (manufacturer correlation) |
CONSTRAINED_RECONSTRUCTION: patent-defined cemented L2 translates imageward. Canon's 3.0 m focal-plane MFD solves D12 = 24.36 + δ and D15 = 98.83 − δ with δ = 18.794827332 mm; D12 + D15 stays 123.19 mm. Rear FL/FC are omitted and R29→IMG is normalized to 70.697755606 mm at infinity.
| Element | Type | Glass |
|---|---|---|
| HG | Plane-Parallel Plate | S-BSL7 coefficient proxy (patent 516641; production supplier unspecified) |
| L1a | Biconvex Positive | S-FPL51 coefficient proxy (patent 497815; production supplier unspecified; UD-class correlation) |
| L1b-P | Plano-Convex Positive | S-FPL51 coefficient proxy (patent 497815; production supplier unspecified; UD-class correlation) |
| L1b-N | Biconcave Negative | TAFD5G coefficient proxy (patent 835427; production supplier unspecified) |
| L1c-P | Biconvex Positive | Synthetic fluorite (CaF₂; manufacturer-correlated) |
| L1c-N | Negative Meniscus | S-BSL7 coefficient proxy (patent 516641; production supplier unspecified) |
| L2-P | Biconvex Positive | S-TIH6 coefficient proxy (patent 805254; production supplier unspecified) |
| L2-N | Biconcave Negative | H-ZLaF50D coefficient proxy (patent 804466; production supplier unspecified) |
| L3a-N | Negative Meniscus | PBH53 coefficient proxy (patent 847239; production supplier unspecified) |
| L3a-P | Biconvex Positive | E-LASF016 coefficient proxy (patent 772496; production supplier unspecified) |
| L3b-P | Biconvex Positive | PBH53 coefficient proxy (patent 847239; production supplier unspecified) |
| L3b-N1 | Biconcave Negative | S-BSM15 coefficient proxy (patent 623582; production supplier unspecified) |
| L3b-N2 | Biconcave Negative | H-ZLaF50D coefficient proxy (patent 804466; production supplier unspecified) |
| L3c-P1 | Biconvex Positive | S-BSM15 coefficient proxy (patent 623582; production supplier unspecified) |
| L3c-P2 | Biconvex Positive | S-LAL12 coefficient proxy (patent 678553; production supplier unspecified) |
| L3c-N | Biconcave Negative | S-LAH58 coefficient proxy (patent 883408; production supplier unspecified) |