JP H02-248910 A, Numerical Example 1 — Yasunori Murata
| 7 ELEMENTS / 6 GROUPS |
| DESIGN f = 15.3 mm |
| DESIGN F/2.8 |
| ALL SPHERICAL |
| EQUISOLID FISHEYE, 2ω = 180° |
Inferred unit focus: the whole lens moves away from the image, so only the image gap grows, from 38.96 mm at infinity to 42.69 mm (3.73 mm) at Sigma's 0.15 m minimum focus distance. The patent tabulates infinity only and does not name the production focusing method; the model reaches 1:4.1 at close focus against Sigma's 1:3.8. Nine keyframes are solved paraxially and positions between them are interpolated.
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | J-LAK14 (HIKARI catalog equivalent; production supplier unspecified) |
| L2 | Negative Meniscus | NBFD11 (HOYA catalog equivalent; production supplier unspecified) |
| L3 | Biconvex Positive | FD140 (HOYA catalog equivalent; production supplier unspecified) |
| L4 | Negative Meniscus | NBFD15 (HOYA catalog equivalent; production supplier unspecified) |
| L5 | Biconvex Positive | FK5 (SUMITA catalog equivalent; production supplier unspecified) |
| L6 | Biconvex Positive | FK5 (SUMITA catalog equivalent; production supplier unspecified) |
| L7 | Negative Meniscus | FD60 (HOYA catalog equivalent; production supplier unspecified) |