Abstract

Conditions are given for the performance requirements for a high speed spectrograph objective to be used primarily for the Raman effect in the region 4358 to 5000A. A formula is given for the construction of such an objective at a speed of f/2.0. This objective has a flat tangential field and gives extremely sharp definition. With slight retouching of the back of the second flint component perfection of definition can be achieved in lenses up to 12 in. focal length. A correction to the formula is given to render the field flat with all spherical surfaces. The unretouched system works perfectly satisfactorily up to an 8 in. focal length. The trignometrically calculated aberration curves are given for a lens of 10 in. focal length.

The formula is given for construction of a 10 in. focal length f/3.5 three element lens. The design consists of a telescope objective followed by an aplanatic element. Aberration and performance characteristics are given and discussed.

© 1950 Optical Society of America

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References

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  1. G. S. Fulcher, J. Opt. Soc. Am. 37, 49 (1947).

1947 (1)

G. S. Fulcher, J. Opt. Soc. Am. 37, 49 (1947).

Fulcher, G. S.

G. S. Fulcher, J. Opt. Soc. Am. 37, 49 (1947).

J. Opt. Soc. Am. (1)

G. S. Fulcher, J. Opt. Soc. Am. 37, 49 (1947).

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Figures (6)

Fig. 1
Fig. 1

Color curve of f/2.0 objective E.F.L.=10.000 in.

Fig. 2
Fig. 2

Chromatic variation of axial aberrations of f/2.0 objective E.F.L.=10.000 in. Curve marked S.A. refers to ordinates on left of figure and is for rim zone. Curve marked ΔE.F.L. represents difference in E.F.L. of rim and paraxial zones. Ordinates for this curve given on right of figure. All aberrations given in inches.

Fig. 3
Fig. 3

T.F. field curvature determined trignometrically for 0.7 zone of 10.000 E.F.L. f/2.0 lens. Ordinates for this curve given at left of figure. S.A. off axis spherical aberration for 0.7 zone. Ordinates for this curve given at right of figure. Aberrations given in inches. The T.F. curve represents the relative departure of the focii for the various wave-lengths for the 0.7 zone from an arbitrarily chosen plane. The field angles for the various wave-lengths are dictated by the dispersing device i.e., grating which is described in detail in the text. λ4680 is on the optical axis of the lens.

Fig. 4
Fig. 4

Axial zonal spherical aberration for λ4861 for 10 in. E.F.L. f/2.0 lens. Aberrations in inches. Abscissae (h/h max.)2

Fig. 5
Fig. 5

Drawing of the axial section of the f/2.0 spectrograph objective described in Table I.

Fig. 6
Fig. 6

Drawing of the axial section of the f/3.5 “spectroaplanat” described in Table II.

Tables (2)

Tables Icon

Table I Formula for f/2.0 spectrograph objectives. All dimensions are given in inches.

Tables Icon

Table II Formula for f/3.5 “Spectroaplanat.” All dimensions are given in inches.