Table I
Optical constants of viewing lens.
| Equivalent focal length | 31.94 mm |
| Back focal distance | 29.27 mm |
| Back flange focal distance | 28.07 mm |
| Nodal point separation | 0.59 mm |
| Lens thickness | 7.10 mm |
| Entrance pupil to front surface | 2.23 mm |
| Exit pupil to back surface | 4.39 mm |
Table II
Values of the dioptric power, D, of a spectacle lens as a function of dial gauge reading, Δf, for a range from +20.00 to−20.00 diopters. The values, dD/df, give the sensitivity of the instrument for various values of D.
| Δf (inches) | D (diopters) | (dD/df)×0.001 (diopters/milli-inch) |
|---|
| 0.621 | +20.00 | 0.042 |
| 0.494 | 15.00 | 0.037 |
| 0.350 | 10.00 | 0.033 |
| 0.187 | 5.00 | 0.028 |
| 0.078 | 2.00 | 0.026 |
| 0.000 | 0.00 | 0.025 |
| −0.083 | −2.00 | 0.023 |
| −0.217 | −5.00 | 0.021 |
| −0.471 | −10.00 | 0.018 |
| −0.774 | −15.00 | 0.015 |
| −1.389 | −20.00 | 0.012 |
Table III
Setting of spectacle tester in diopters for best imagery of tangential and radial lines as a function of angular separation from the axis for a periscopic lens having a spherical power of +2.00 diopters and a base curve of−1.25 diopters. Values are given for four object distances and values of the astigmatic difference in setting are shown.
| Object distance meters | Setting for best imagery for tangential lines at angular separation from axis of |
|---|
| 0° | 5° | 10° | 15° | 20° | 25° | 30° |
|---|
| ∞ | 1.99 | 2.01 | 2.03 | 2.11 | 2.18 | 2.30 | 2.49 |
| 1.00 | 0.98 | 1.02 | 1.03 | 1.09 | 1.16 | 1.25 | 1.39 |
| 0.50 | −0.04 | −0.02 | 0.01 | 0.06 | 0.13 | 0.22 | 0.35 |
| 0.25 | −2.08 | −2.06 | −2.03 | −2.01 | −1.97 | −1.91 | −1.84 |
|
| Object distance meters | Setting for best imagery for radial lines at angular separation from axis of |
| 0° | 5° | 10° | 15° | 20° | 25° | 30° |
|
| ∞ | 1.99 | 2.01 | 2.01 | 2.02 | 2.03 | 2.04 | 2.07 |
| 1.00 | 0.98 | 0.98 | 0.98 | 0.98 | 1.02 | 1.02 | 1.06 |
| 0.50 | −0.04 | −0.04 | −0.03 | −0.02 | 0.00 | 0.02 | 0.05 |
| 0.25 | −2.08 | −2.06 | −2.05 | −2.05 | −2.04 | −2.03 | −2.03 |
|
| Object distance meters | Values of the astigmatic difference at angular separation from axis of |
| 0° | 5° | 10° | 15° | 20° | 25° | 30° |
|
| ∞ | 0.00 | 0.00 | 0.01 | 0.09 | 0.15 | 0.26 | 0.42 |
| 1.00 | 0.00 | 0.04 | 0.05 | 0.11 | 0.14 | 0.23 | 0.33 |
| 0.50 | 0.00 | 0.02 | 0.04 | 0.08 | 0.13 | 0.20 | 0.30 |
| 0.25 | 0.00 | 0.00 | 0.02 | 0.04 | 0.07 | 0.12 | 0.19 |
Table IV
Setting of spectacle tester in diopters for best imagery of tangential and radial lines as a function of angular separation from the axis for a meniscus lens having a spherical power of +2.00 diopters and a base curve of−6.00 diopters. Values are given for four object distances and values of the astigmatic difference in setting are shown.
| Object distance meters | Setting for best imagery for tangential lines at angular separation from axis of |
|---|
| 0° | 5° | 10° | 15° | 20° | 25° | 30° | 35° |
|---|
| ∞ | 2.02 | 2.01 | 1.99 | 1.98 | 1.95 | 1.92 | 1.92 | 1.91 |
| 1.00 | 1.02 | 1.00 | 0.98 | 0.97 | 0.93 | 0.89 | 0.86 | 0.87 |
| 0.50 | 0.02 | −0.01 | −0.04 | −0.07 | −0.11 | −0.16 | −0.19 | −0.23 |
| 0.25 | −1.91 | −1.95 | −2.00 | −2.03 | −2.09 | −2.16 | −2.23 | −2.31 |
|
| Object distance meters | Setting for best imagery for radial lines at angular separation from axis of |
| 0° | 5° | 10° | 15° | 20° | 25° | 30° | 35° |
|
| ∞ | 2.02 | 2.01 | 1.99 | 1.97 | 1.95 | 1.92 | 1.90 | 1.86 |
| 1.00 | 1.02 | 1.00 | 0.98 | 0.97 | 0.97 | 0.92 | 0.88 | 0.85 |
| 0.50 | 0.02 | −0.01 | −0.03 | −0.04 | −0.07 | −0.11 | −0.14 | −0.19 |
| 0.25 | −1.91 | −1.95 | −1.98 | −2.00 | −2.03 | −2.06 | −2.09 | −2.16 |
|
| Object distance meters | Values of the astigmatic difference at angular separations from axis of |
| 0° | 5° | 10° | 15° | 20° | 25° | 30° | 35° |
|
| ∞ | 0.00 | 0.00 | 0.00 | 0.01 | 0.00 | 0.00 | 0.02 | 0.05 |
| 1.00 | 0.00 | 0.00 | 0.00 | 0.00 | −0.04 | −0.03 | −0.02 | 0.02 |
| 0.50 | 0.00 | 0.00 | −0.01 | −0.03 | −0.05 | −0.05 | −0.05 | −0.04 |
| 0.25 | 0.00 | 0.00 | −0.02 | −0.03 | −0.06 | −0.10 | −0.14 | −0.15 |
Table V
Measured values of the angular distortion as a function of viewing angle on the eye side for a periscopic type lens having a spherical power of +2.00 diopters. The distortion is given as the algebraic difference between the viewing angle and the half-field angle.
| Viewing angle degrees | Half-field angle degrees | Angular distortion degrees |
|---|
| 0.00 | 0.00 | 0.00 |
| 5.00 | 4.75 | 0.25 |
| 10.00 | 9.40 | 0.60 |
| 15.00 | 14.07 | 0.93 |
| 20.00 | 18.68 | 1.32 |
| 25.00 | 23.32 | 1.68 |
| 30.00 | 27.83 | 2.17 |
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