EP 2 321 688 B1 — Iain A. Neil
| 18 ELEMENTS / 15 GROUPS |
| DESIGN f ≈ 18 mm |
| PATENT ≈ F/1.4; PRINTED 15.80 mm IRIS TRACES F/1.32 |
| MARKETED T1.4 (TRANSMISSION STOP) |
| 2 ASPHERICAL SURFACES / 2 ELEMENTS |
PUBLISHED three-state floating focus (Table 1, F1/F2/F3). The front sub-group G1a is fixed. From infinity to the nearest printed state, G1b moves 1.657 mm toward the image and G2, which carries the iris, moves 1.777 mm toward the object (0.699 mm and 0.899 mm at the middle state); the image plane stays fixed. Displayed distances replace the patent's optional front filter by its air-equivalent thickness: 341.6 mm and 532.3 mm from object to image, against 342.6 mm and 533.3 mm with the filter in place. The patent text quotes the same two states from its first surface instead, as about 15 cm and 34 cm. Positions between the printed states are interpolated. The marketed close focus (0.35 m to 0.5 m depending on the listing) is not the patent's near state.
| Element | Type | Glass |
|---|---|---|
| L2 | Biconvex Positive | S-LAL61 (OHARA) |
| L3 | Negative Meniscus (1× Asph) | S-FPL51 (OHARA) |
| L4 | Biconcave Negative | S-LAM2 (OHARA) |
| L5 | Positive Meniscus | S-TIH6 (OHARA) |
| L6 | Biconcave Negative | S-FPL53 (OHARA) |
| L7 | Biconvex Positive | S-NBH51 (OHARA) |
| L8 | Biconvex Positive | S-LAH58 (OHARA) |
| L9 | Positive Meniscus | S-FPL53 (OHARA) |
| L10 | Positive Meniscus | S-PHM52 (OHARA) |
| L11 | Negative Meniscus | S-LAM66 (OHARA) |
| L12 | Biconcave Negative | S-NBH51 (OHARA) |
| L13 | Biconvex Positive | S-FPL53 (OHARA) |
| L14 | Biconvex Positive | S-FPL53 (OHARA) |
| L15 | Negative Meniscus | S-LAH59 (OHARA) |
| L16 | Positive Meniscus | S-FPL53 (OHARA) |
| L17 | Negative Meniscus (1× Asph) | S-NBH51 (OHARA) |
| L18 | Biconvex Positive | S-NPH1 (OHARA) |
| L19 | Biconvex Positive | S-PHM52 (OHARA) |