US 3,622,227 Example I — Nippon Kogaku / Yoshiyuki Shimizu
| 9 ELEMENTS / 7 GROUPS |
| f ≈ 24.0 mm |
| F/2.8 |
| 2ω ≈ 84° |
| ALL SPHERICAL |
CRC (Close-Range Correction): L6–L7 gap narrows during close focusing, compensating retrofocus astigmatism. First production CRC lens (1967).
| Element | Type | Glass |
|---|---|---|
| L1 | Negative Meniscus | SK16 (Schott) / S-BSM16 (Ohara) |
| L2 | Biconvex Positive | SK16 (Schott) / S-BSM16 (Ohara) |
| L3 | Negative Meniscus | SK16 (Schott) / S-BSM16 (Ohara) |
| L4 | Biconvex Positive | F2 (Schott) / S-TIM2 (Ohara) |
| L5 | Negative Meniscus | BSC3 (Hoya) / historical crown equivalent |
| L6 | Biconcave Negative | SF56A (Schott) / S-TIH6 (Ohara) |
| L7 | Biconcave Negative | SF56A (Schott) / S-TIH6 (Ohara) |
| L8 | Biconvex Positive | SK16 (Schott) / S-BSM16 (Ohara) |
| L9 | Biconvex Positive | LAF2 (Schott) / S-LAM2 (Ohara) |
Detailed analysis available in the interactive viewer above.