US 2019/0041605 A1 — Shinichiro Saito, Makoto Nakahara
| 17 ELEMENTS / 13 GROUPS PRODUCTION; 16 / 12 ACTIVE MODEL |
| 600mm f/4 MARKETED |
| f ≈ 587.93 mm / F4.12 DESIGN |
| 2ω ≈ 4.22° |
| 2 FLUORITE + 1 SUPER UD |
| ALL-SPHERICAL |
| INNER FOCUS / IS |
CONSTRAINED_RECONSTRUCTION: E8/L2 (surfaces 15–16) translates 18.906939851 mm imageward from infinity to the modeled 4.2 m MFD. The STO→15 gap changes 3.49→22.396939851 mm and d16 changes 38.06→19.153060149 mm, preserving their 41.55 mm sum and the fixed image plane. The patent publishes no finite-focus spacing row; the reconstruction is solved from Canon's MFD and independently cross-checks at |m|=0.149215 versus the marketed 0.15×.
| Element | Type | Glass |
|---|---|---|
| E1 | Biconvex Positive | PCD51 (HOYA) |
| E2 | Biconvex Positive | Fluorite (CaF2; manufacturer-constrained) |
| E3 | Biconcave Negative | NBFD15-W (HOYA) |
| E4 | Positive Meniscus | Fluorite (CaF2; manufacturer-constrained) |
| E5 | Positive Meniscus | S-NPH53 (OHARA; legacy) |
| E6 | Negative Meniscus | N-LASF44 (SCHOTT) |
| E7 | Positive Meniscus | 437951 ultra-low-dispersion class; spectral proxy FCD100 (HOYA) |
| E8 | Negative Meniscus | PCD51 (HOYA) |
| E9 | Negative Meniscus | S-NPH4 (OHARA) |
| E10 | Biconvex Positive | S-NBH53 (OHARA; legacy) |
| E11 | Biconvex Positive | FD60-W (HOYA) |
| E12 | Biconcave Negative | PCD51 (HOYA) |
| E13 | Biconcave Negative | S-LAH59 (OHARA) |
| E14 | Positive Meniscus | S-NBH56 (OHARA) |
| E15 | Biconvex Positive | H-ZBaF4 catalog equivalent (patent 666356; production supplier unspecified) |
| E16 | Biconcave Negative | S-NPH4 (OHARA) |