US 5,760,973 EXAMPLE 1 — RICOH / KAWAMURA
| 7 ELEMENTS / 4 GROUPS |
| f ≈ 28.1 mm |
| F/2.86 |
| 2ω ≈ 74.4° |
| 2 ASPHERICAL SURFACES |
Unit focusing — entire 7-element assembly translates axially. Extension ≈ 2.45 mm at 0.35 m close focus.
| Element | Type | Glass |
|---|---|---|
| L1 | Biconcave Neg. (1× Asph) | SF2 (Schott) / FD2 (HOYA) |
| L2 | Biconvex Positive | S-LAM54 (OHARA) |
| L3 | Negative Meniscus | S-TIM35 (OHARA) / FD110 (HOYA) |
| L4 | Biconcave Negative | FK5 (Schott) / S-FSL5 (OHARA) |
| L5 | Biconvex Positive | S-LAH55 (OHARA) / TAFD5 (HOYA) |
| L6 | Negative Meniscus | EFD4 (HOYA) |
| L7 | Neg. Meniscus (1× Asph) | F5 (Schott) / S-TIM5 (OHARA) |
Detailed analysis available in the interactive viewer above.