JP 2020-177057 A — Masashi Yamashita, Toshinori Take
| 25 ELEMENTS / 19 GROUPS |
| f = 123.6–291.0 mm (patent) |
| F/2.91 (constant) |
| 2ω = 19.57°–8.29° |
| ALL SPHERICAL |
G4 internal focus — G4 moves object-side for close focus (patent ¶0057). Constant overall length. G4 close-focus travel is calculated for the production 2.0 m MFD, not tabulated in the patent.
| Element | Type | Glass |
|---|---|---|
| L11 | Negative Meniscus | J-LASFH9 (Hikari) |
| L12 | Biconvex Positive | J-FKH1 (Hikari) |
| L13 | Plano-Convex Positive | CaF2 Fluorite |
| L21 | Positive Meniscus | N-KZFS8 (Schott; exact patent coordinate and APD-family match) |
| L22 | Biconvex Positive | S-TIH1 (OHARA; exact 717295 coordinate) |
| L23 | Biconcave Negative | J-LAK14 (Hikari) |
| L24 | Biconcave Negative | J-LASF015 (Hikari) |
| L25 | Positive Meniscus | J-SFH5 (Hikari) — anomalous-dispersion niobium flint (756247) |
| L26 | Negative Meniscus | TAFD32 (HOYA, 871407) |
| L31 | Biconvex Positive | J-LASKH2 (Hikari) |
| L32 | Biconvex Positive | CaF2 Fluorite |
| L33 | Biconcave Negative | N-KZFS5 (Schott; OHARA S-NBH5 same coordinate) |
| L34 | Biconvex Positive | TAFD35 (HOYA) |
| L41 | Plano-Convex Positive | J-LASF015 (Hikari) |
| L42 | Biconvex Positive | J-PSKH4 (Hikari) |
| L43 | Biconcave Negative | J-SF03 (Hikari) |
| L51 | Biconcave Negative | S-LAH99 / TAFD55 (001291, HRI) |
| L52 | Biconvex Positive | J-LAK18 (Hikari) |
| L53 | Negative Meniscus | TAFD32 (HOYA, 871407) |
| L54 | Positive Meniscus | S-TIH6 (OHARA) |
| L55 | Biconcave Negative | J-BK7A (Hikari) |
| L56 | Biconvex Positive | S-LAH99 / TAFD55 (001291, HRI) |
| L57 | Negative Meniscus | J-LASF015 (Hikari) |
| L58 | Biconvex Positive | J-FK5 (Hikari) |
| L59 | Biconcave Negative | TAFD37A (HOYA catalog-equivalent; patent vendor unspecified) |