US 4,176,913 A, Example 2 — Soichi Nakamura, Kiyoshi Hayashi
| 10 ELEMENTS / 8 GROUPS |
| f = 200 mm |
| F/2 |
| 2ω = 12.32° |
| 2 ED ELEMENTS |
| INTERNAL FOCUS |
PUBLISHED internal-focus states from US 4,176,913 A Example 2: the complete negative middle group translates 17.000 mm imageward; D6 increases 41.201→58.201 mm while D11 decreases 22.912→5.912 mm, preserving D6+D11=64.113 mm. The patent labels the close endpoint β≈-0.1; this slider endpoint is not reconstructed from the production 2.5 m MFD.
| Element | Type | Glass |
|---|---|---|
| L11 | Biconvex Positive | J-FKH1 catalog-equivalent coefficient proxy (patent 500819; production supplier unspecified) |
| L12 | Biconvex Positive | J-FKH1 catalog-equivalent coefficient proxy (patent 500819; production supplier unspecified) |
| L13 | Biconcave Negative | E-FD4 catalog-equivalent coefficient proxy (patent 755275; production supplier unspecified) |
| L21a | Positive Meniscus (cemented) | J-LAFH3 catalog-equivalent coefficient proxy (patent 795284; production supplier unspecified) |
| L21b | Biconcave Negative (cemented) | FK3 catalog-equivalent coefficient proxy (patent 465658; production supplier unspecified) |
| L22 | Biconcave Negative | FK3 catalog-equivalent coefficient proxy (patent 465658; production supplier unspecified) |
| L31 | Biconvex Positive | H-LaK6A catalog-equivalent coefficient proxy (patent 694536; production supplier unspecified) |
| L32a | Biconcave Negative (cemented) | FF5 catalog-equivalent coefficient proxy (patent 595356; production supplier unspecified) |
| L32b | Biconvex Positive (cemented) | K-LaK14 catalog-equivalent coefficient proxy (patent 697556; production supplier unspecified) |
| L33 | Negative Meniscus | FK3 catalog-equivalent coefficient proxy (patent 465658; production supplier unspecified) |