Abstract

An apparatus incorporating several improvements for direct measurement of aberrations in microscope objectives is described. In principle, it is similar to that of Kingslake, who by shifting a pinhole across the aperture of a microscope objective measured the resultant transverse aberration from which spherical aberration could be readily calculated. By using a different pinhole system, accuracy of setting has been improved, as also the brightness of image. Sensitivity of measurement of transverse aberration has been increased by the addition of a separate magnifying system.

The theory of measurements has been extended to extra axial aberrations and the methods of measurements of spherical aberration, offence against sine condition, tangential and sagittal curvatures have been described with aberration graphs for a typical microscope objective.

© 1960 Optical Society of America

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References

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  1. R. Kingslake, J. Opt. Soc. Am. 26, 251 (1936).
    [Crossref]
  2. L. C. Martin, Trans. Opt. Soc. 23, 75 (1921); C. Beck, Trans. Opt. Soc. 28, 37 (1926); Hartridge, Proc. Cambridge Phil. Soc. 21, 29 (1922).
    [Crossref]
  3. A. E. Conrady, Applied Optics and Optical Design (Dover Publications Inc., New York, 1957), p. 404.
  4. Equation (3) was first suggested to the authors by H. A. Unvala, Scientific Officer, Ministry of Defence, Government of India.

1936 (1)

1921 (1)

L. C. Martin, Trans. Opt. Soc. 23, 75 (1921); C. Beck, Trans. Opt. Soc. 28, 37 (1926); Hartridge, Proc. Cambridge Phil. Soc. 21, 29 (1922).
[Crossref]

Conrady, A. E.

A. E. Conrady, Applied Optics and Optical Design (Dover Publications Inc., New York, 1957), p. 404.

Kingslake, R.

Martin, L. C.

L. C. Martin, Trans. Opt. Soc. 23, 75 (1921); C. Beck, Trans. Opt. Soc. 28, 37 (1926); Hartridge, Proc. Cambridge Phil. Soc. 21, 29 (1922).
[Crossref]

Unvala, H. A.

Equation (3) was first suggested to the authors by H. A. Unvala, Scientific Officer, Ministry of Defence, Government of India.

J. Opt. Soc. Am. (1)

Trans. Opt. Soc. (1)

L. C. Martin, Trans. Opt. Soc. 23, 75 (1921); C. Beck, Trans. Opt. Soc. 28, 37 (1926); Hartridge, Proc. Cambridge Phil. Soc. 21, 29 (1922).
[Crossref]

Other (2)

A. E. Conrady, Applied Optics and Optical Design (Dover Publications Inc., New York, 1957), p. 404.

Equation (3) was first suggested to the authors by H. A. Unvala, Scientific Officer, Ministry of Defence, Government of India.

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Figures (11)

Fig. 1
Fig. 1

Drawing of the testing apparatus; A, microscope objective; B graduated rotatable shoulder; D, pinhole carrier; E, microscope tube; F, special attachment; G, micrometer screw.

Fig. 2
Fig. 2

Path of light rays. S, source—high-pressure mercury arc (Mazda ME/D, 250w) F, filter; C, condenser; O, star object; A, objective; Exp, plane of exit pupil; Ap, plane of the pinhole; P, plane of measurement; M, auxiliary magnifying microscope; PM, plane of a filar micrometer eyepiece.

Fig. 3
Fig. 3

Photograph showing the interference pattern produced by a four pinhole system. The vertical straight line represents the cross hair of the filar micrometer.

Fig. 4
Fig. 4

Relation between the exit-pupil aperture and the aperture measured in the plane of the pinhole.

Fig. 5
Fig. 5

Deduction of the equations for Tangential OSC′ and tangential field curvature.

Fig. 6
Fig. 6

Deduction of the equations for sagittal OSC′ and sagittal curvature.

Fig. 7
Fig. 7

Transverse aberration and the longitudinal spherical aberration curves of the microscope objective.

Fig. 8
Fig. 8

Off-axis transverse aberration, tangential OSC′ and XT curves of the microscope objective.

Fig. 9
Fig. 9

Transverse aberration Δζ on the sagittal plane, and XS curve of the microscope objective.

Fig. 10
Fig. 10

The curves at the top show the tangential and sagittal field curvatures for zonal as well as marginal rays. Bottom curves show the variation of OSC′ with field.

Fig. 11
Fig. 11

Degree of stability of the transverse aberration readings and comparison of spherical aberration curves obtained from measurements in two different measuring planes.

Tables (3)

Tables Icon

Table I Readings for transverse aberration of axial and off-axis images; x=3 mm, S=150 mm, P=plane of best visual focus.

Tables Icon

Table II Calculation of L, OSC′, XT, and XS.

Tables Icon

Table III Calculation of OSC′ (sagittal), Gpr=6 mm.

Equations (15)

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T = T 0 + d ( N - 1 ) N · S × ( y + T 0 + G p r ) ,
Y = y + x tan U = y + x ( y + T + G p r ) S
Y = y + x ( y + G p r ) S
Y = y + ( x y / S ) .
y + [ x ( y + G p r ) / S ] = 0
y = - G p r [ x / ( S + x ) ] .
T = T M / m .
L = T tan U = T ( S + x Y + T ) .
com a T = G p r - G U + G L 2
O S C = coma T 3 G p r = G p r - 1 2 ( G U + G L ) 3 G p r .
sin < U Q L = U L ( S + x ) - X T = 2 Y S + x ,
X T = G U - G L sin < U Q L = ( G U - G L ) ( S + x ) 2 Y .
X S = ( Δ ζ S + - Δ ζ S - ) 2 Y ( S + x ) ,
O S C = G p r - 1 2 ( G S + + G S - ) G p r .
O P D = ( δ y / S ) 0 y T ,