JP 1987-249119 A — Tetsuya Arimoto
| 10 ELEMENTS / 9 GROUPS |
| 20mm |
| f/2.8 |
| 94° |
| REAR FOCUS |
CONSTRAINED_RECONSTRUCTION: the complete rear group Gr translates 2.937842606 mm toward the object from infinity to 0.25 m; D4 decreases from 9.349000000 to 6.411157394 mm while r19-to-IMG increases by the same amount to keep the image plane fixed. The patent-published beta=0.1 state is independently reproduced but is not used as the production close-focus endpoint.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | BSC7 (Hoya; exact coordinate equivalent, patent vendor unresolved) |
| L2 | Negative Meniscus | PCD4 coefficient proxy (supplier unspecified; patent 618635) |
| L3 | Negative Meniscus | H-LaK12 coefficient proxy (supplier unspecified; patent 697565) |
| L4 | Plano-Convex Positive | 683315 — flint class (catalog unresolved) |
| L5 | Negative Meniscus | NBFD11 coefficient proxy (supplier unspecified; patent 786428) |
| L6 | Biconvex Positive | S-LAH60 coefficient proxy (supplier unspecified; patent 834371) |
| L7 | Biconcave Negative | SF57 (Schott; exact coordinate equivalent, patent vendor unresolved) |
| L8 | Positive Meniscus | PCD4 coefficient proxy (supplier unspecified; patent 618635) |
| L9 | Negative Meniscus | S-LAH60 coefficient proxy (supplier unspecified; patent 834371) |
| L10 | Biconvex Positive | PCS1 (Hoya; near-exact coordinate equivalent, patent vendor unresolved) |