US 4,717,245 EXAMPLE 2 — CANON / TAKAHASHI
| 11 ELEMENTS / 9 GROUPS |
| f ≈ 50.0 mm |
| F/1.0 |
| 2ω ≈ 45.2° |
| 2 ASPHERICAL SURFACES |
Floating front extension — L11 fixed, L1–L10 extend forward. Close-focus gap computed via thin-lens model; production uses floating mechanism with undocumented sub-group displacements.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | S-BSM14 (OHARA) |
| L2 | Positive Meniscus | S-LAL14 (OHARA) |
| L3 | Neg. Meniscus (1× Asph) | S-NSL5 (OHARA) |
| L4 | Positive Meniscus | S-LAH58 (OHARA) |
| L5 | Negative Meniscus | S-NSL5 (OHARA) |
| L6 | Biconcave Negative | S-TIH53 (OHARA) |
| L7 | Biconvex Positive | S-LAH58 (OHARA) |
| L8 | Neg. Meniscus (1× Asph) | S-TIH6 (OHARA) |
| L9 | Positive Meniscus | S-LAH58 (OHARA) |
| L10 | Biconvex Positive | S-LAH58 (OHARA) |
| L11 | Positive Meniscus | S-BSL10 (OHARA) |
Detailed analysis available in the interactive viewer above.