US 5,315,441 — Kenji Hori, Wataru Tatsuno
| 11 ELEMENTS / 8 GROUPS |
| f ≈ 28.6 mm |
| F/1.4 |
| 2ω ≈ 75.4° |
| 1 ASPHERICAL SURFACE (GROUND GLASS) |
Three-group floating focus (Nikon CRC). G1 fixed relative to the image plane. G2 + aperture stop and G4 are mechanically coupled and move together toward the object. G3 moves toward the object at 1.1× the speed of G2/G4, creating differential gap changes that independently correct spherical aberration and astigmatism at close range.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | BSC7 / BK7 type (HOYA BSC7 nd=1.51680, νd=64.20) |
| L2 | Biconvex Positive | S-LAH66 (OHARA) — near nd=1.77250/νd=49.62 |
| L3 | Negative Meniscus | FK5 / S-FSL5 type (Schott FK5 nd=1.48749, νd=70.41) |
| L4a | Positive Meniscus | J-PKH1 (Hikari, 519699) |
| L4b | Negative Meniscus | KF3 (SUMITA catalog equivalent for patent coordinate; production supplier unspecified) |
| L5 | Biconvex Positive | S-LAH65V (OHARA) — near nd=1.80400/νd=46.58 |
| L6a | Positive Meniscus | 748523 — E-LAKH1 catalog equivalent (Hikari; production supplier unspecified) |
| L6b | Negative Meniscus | Dense flint (near OHARA S-TIH4, nd=1.75520, νd=27.53) |
| L7 | Pos. Meniscus (1× Asph) | S-LAH66 (OHARA) — same as L2 |
| L8a | Plano-Convex Positive | S-LAH65V (OHARA) — same as L5 |
| L8b | Negative Meniscus | J-SFH2 (Hikari coordinate match) |