US 4,352,544, sole example — Toshihiro Imai
| 6 ELEMENTS / 6 GROUPS |
| DESIGN f = 28.00 mm |
| DESIGN F/2.80 |
| ALL SPHERICAL |
Unit focus with a straight helicoid; the whole lens moves toward the object to focus at 0.3 m. Close-focus travel is calculated from the infinity prescription.
| Element | Type | Glass |
|---|---|---|
| L1 | Positive Meniscus | S-LAM52 (OHARA coordinate equivalent; supplier unconfirmed) |
| L2 | Negative Meniscus | S-BSM16 (OHARA coordinate equivalent; supplier unconfirmed) |
| L3 | Biconvex Positive | S-LAH63 (OHARA coordinate equivalent; supplier unconfirmed) |
| L4 | Biconcave Negative | FD110 (HOYA coordinate equivalent; supplier unconfirmed) |
| L5 | Positive Meniscus | S-BSM16 (OHARA coordinate equivalent; supplier unconfirmed) |
| L6 | Biconvex Positive | BSM4 (OHARA coordinate equivalent; supplier unconfirmed) |