JP 2015-11156 A — Takahiko Oishi
| 9 ELEMENTS / 8 GROUPS |
| 20–40mm f/2.8–4 (production) |
| 20.60 / 30.00 / 39.00 mm (patent) |
| FNO 2.9 / 2.9 / 4.0 |
| 1 ASPHERICAL SURFACE |
| 1 ED + 1 ANOMALOUS-DISPERSION ELEMENT |
CONSTRAINED_RECONSTRUCTION: G1 translates objectward for close focus. Close-focus D6 states are solved from the production 0.28 m MFD with object distance normalized from the image plane; the patent publishes only infinity spacings.
| Element | Type | Glass |
|---|---|---|
| L11 | Negative Meniscus | 729547 (vendor/catalog identity unresolved) |
| L12 | Neg. Meniscus (1× Asph) | K-VC80-M (Sumita catalog equivalent; patent code 689528, supplier unspecified) |
| L13 | Positive Meniscus | 762265 (vendor/catalog identity unresolved) |
| L21 | Biconvex Positive | 743493 (vendor/catalog identity unresolved) |
| L22 | Biconvex Positive | 497816 (vendor/catalog identity unresolved) |
| L23 | Biconcave Negative | 788474 (vendor/catalog identity unresolved) |
| L25 | Positive Meniscus | 717479 (vendor/catalog identity unresolved) |
| L26 | Negative Meniscus | 847238 (vendor/catalog identity unresolved) |
| L27 | Biconvex Positive | 603655 (vendor/catalog identity unresolved) |