Abstract

With this eyepiece the plane-polarization in a beam of light is compensated by means of a thin, plane-parallel plate of celluloid tilted at the proper angle. To ascertain if the compensation is complete a detector consisting of a quartz plate and a second tiltable plate of celluloid is used in combination with a Savart plate and a nicol or Wollaston prism. The biquartz plate consists of two plates of quartz cut normal to the optic axis, the one of dextrogyre and the second of laevogyre quartz, mounted side by side with polished junction faces. The thickness of the quartz plates is such (1.76 mm) that for mercury green light of wave-length 5461A the rotation is ±45°. An incident plane-polarized beam is divided into two beams by the biquartz plate; the plane of vibration of the beam emerging from the first half of the plate is normal to that of the second beam. The tiltable plate of the detector is mounted above the biquartz plate and has its axis of rotation in the plane of vibration of the wave emerging from one of the biquartz plate halves. By means of this second plate a small amount of polarization can be added to, or subtracted from the polarization in the transmitted beams. The Savart plate and analyzing prism serve to detect the presence of plane-polarized light in the beam. With the aid of this eyepiece the amount of plane-polarization can be determined, for low percentages, to one-fifth of one percent. The eyepiece has been used chiefly in the measurement of the percentage plane-polarization in light reflected by different parts of the moon’s surface and by terrestrial materials; also for the measurement of sky polarization and in metallographic work.

© 1934 Optical Society of America

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References

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  1. D. Brewster, Edinburgh Trans. 9, 148 (1819); F. Savart, Pogg. Ann. 49, 292 (1840).
  2. J. Koenigsberger, Centralblatt f. Min., Geol., u. Paläon., 195–197 (1901); 565–569, 597–605 (1908); 245–250 (1909); 712–713 (1910).
  3. B. Lyot, Recherches sur la polarisation de la lumière des planètes et de quelques substances terrestres. Observatoire de Paris (section de Meudon)12–15 (1929).
  4. For the preparation of mounted celluloid films the following method has been found satisfactory: A solution of celluloid in amylacetate or glacial acetic acid is poured over the clean surface of a piece of plate glass about 10 cm square; this is then set on edge, and the excess celluloid solution is allowed to drain off. The film remaining on the glass is thin, but it should not be so thin that it shows Newton interference colors. The film is allowed to dry over night. The brass annular ring is then placed with its flat mounting surface on the film and a small quantity of the celluloid solution is spread around the outer edge of the ring and permitted to dry for several hours; the celluloid film is then cut with a sharp knife edge drawn around the outside of the mounting ring. Water is now flowed around the cut and is forced by capillarity between the plate and film, thus gradually releasing the film from the glass plate. The celluloid film thus attached to the ring mount is quite flat and is not strained, as it may be if the film is first stripped from the glass and then mounted on the ring. If two parallel films are desired a second film may be mounted in the same manner on the opposite side of the ring.
  5. See reference 3, pp. 12–13.
  6. F. E. Wright, Am. J. Sci. (IV) 26, 377–378 (1908).
  7. See reference 3, pp. 21–23.
  8. F. E. Wright, The Transmission of Light Through Inactive Crystal Plates, with Special Reference to Observations in Convergent Polarized Light, Am. J. Sci. (IV) 19, 157–211 (1911).
    [CrossRef]

1929 (1)

B. Lyot, Recherches sur la polarisation de la lumière des planètes et de quelques substances terrestres. Observatoire de Paris (section de Meudon)12–15 (1929).

1911 (1)

F. E. Wright, The Transmission of Light Through Inactive Crystal Plates, with Special Reference to Observations in Convergent Polarized Light, Am. J. Sci. (IV) 19, 157–211 (1911).
[CrossRef]

1908 (1)

F. E. Wright, Am. J. Sci. (IV) 26, 377–378 (1908).

1901 (1)

J. Koenigsberger, Centralblatt f. Min., Geol., u. Paläon., 195–197 (1901); 565–569, 597–605 (1908); 245–250 (1909); 712–713 (1910).

1819 (1)

D. Brewster, Edinburgh Trans. 9, 148 (1819); F. Savart, Pogg. Ann. 49, 292 (1840).

Brewster, D.

D. Brewster, Edinburgh Trans. 9, 148 (1819); F. Savart, Pogg. Ann. 49, 292 (1840).

Koenigsberger, J.

J. Koenigsberger, Centralblatt f. Min., Geol., u. Paläon., 195–197 (1901); 565–569, 597–605 (1908); 245–250 (1909); 712–713 (1910).

Lyot, B.

B. Lyot, Recherches sur la polarisation de la lumière des planètes et de quelques substances terrestres. Observatoire de Paris (section de Meudon)12–15 (1929).

Wright, F. E.

F. E. Wright, The Transmission of Light Through Inactive Crystal Plates, with Special Reference to Observations in Convergent Polarized Light, Am. J. Sci. (IV) 19, 157–211 (1911).
[CrossRef]

F. E. Wright, Am. J. Sci. (IV) 26, 377–378 (1908).

Am. J. Sci. (IV) (2)

F. E. Wright, Am. J. Sci. (IV) 26, 377–378 (1908).

F. E. Wright, The Transmission of Light Through Inactive Crystal Plates, with Special Reference to Observations in Convergent Polarized Light, Am. J. Sci. (IV) 19, 157–211 (1911).
[CrossRef]

Centralblatt f. Min., Geol., u. Paläon. (1)

J. Koenigsberger, Centralblatt f. Min., Geol., u. Paläon., 195–197 (1901); 565–569, 597–605 (1908); 245–250 (1909); 712–713 (1910).

Edinburgh Trans. (1)

D. Brewster, Edinburgh Trans. 9, 148 (1819); F. Savart, Pogg. Ann. 49, 292 (1840).

Observatoire de Paris (section de Meudon) (1)

B. Lyot, Recherches sur la polarisation de la lumière des planètes et de quelques substances terrestres. Observatoire de Paris (section de Meudon)12–15 (1929).

Other (3)

For the preparation of mounted celluloid films the following method has been found satisfactory: A solution of celluloid in amylacetate or glacial acetic acid is poured over the clean surface of a piece of plate glass about 10 cm square; this is then set on edge, and the excess celluloid solution is allowed to drain off. The film remaining on the glass is thin, but it should not be so thin that it shows Newton interference colors. The film is allowed to dry over night. The brass annular ring is then placed with its flat mounting surface on the film and a small quantity of the celluloid solution is spread around the outer edge of the ring and permitted to dry for several hours; the celluloid film is then cut with a sharp knife edge drawn around the outside of the mounting ring. Water is now flowed around the cut and is forced by capillarity between the plate and film, thus gradually releasing the film from the glass plate. The celluloid film thus attached to the ring mount is quite flat and is not strained, as it may be if the film is first stripped from the glass and then mounted on the ring. If two parallel films are desired a second film may be mounted in the same manner on the opposite side of the ring.

See reference 3, pp. 12–13.

See reference 3, pp. 21–23.

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Figures (4)

Fig. 1
Fig. 1

Eyepiece for measuring percentage plane-polarization in a beam of light. Light entering the iris diaphragm I passes to lens L1 whence it emerges as a parallel beam and passes through the tilting-plate compensator P1 to the biquartz plate B, to the detector tilting-plate P2, to the eyepiece O and to the Savart plate S, and the analyzing prism E. The lens L2 serves to focus the beam on the upper surface of B; it is mounted on a slider and can be withdrawn, if not desired.

Fig. 2
Fig. 2

Photographs of Savart fringes. (2a). Incident light is partially plane-polarized; the fringes are of unequal intensity and are not in alignment across the halves of the divided field. (2b). Incident light is plane-polarized. Savart fringes are not in alignment. (2c). Plane-polarization of incident light is compensated. The Savart fringes from the tilting-plate of the detector extend across the field and show no change either in alignment or in intensity.

Fig. 3
Fig. 3

Eyepiece similar to Fig. 1, except that the tilting-plate compensator P1 has been replaced by a combination of Rochon prism R1, a compound Rochon prism R2, a nicol prism N, rotatable in a mount about the telescope axis, and a Rochon prism R3. The intensity of the stronger beam is reduced to that of the second by rotation of the nicol prism through a measured angle α thus producing nonpolarized light emergent from R3.

Fig. 4
Fig. 4

Photometer using the detector of Fig. 1 and the rotation of a nicol or Rochon prism to reduce the intensity of the more intense incident beam to that of the less intense beam so that when the two beams are united by the Rochon prism R3 nonpolarized light results.

Tables (5)

Tables Icon

Table I Percentage intensity of plane-polarized light transmitted by one or more tilted plane-parallel plates of celluloid (nD=1.505). Computed by use of Eqs. (1) to (4).

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Table II Angular separation of fringes from Savart calcite plates of different thicknesses.

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Table III Measurements of percentage plane-polarization in beams of light of known plane-polarization.

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Table IV Measurements, by the Cornu method, to test calibration of eyepiece.

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Table V Measurements of plane-polarization in light reflected by Mare Serenitatis in September, 1933. The readings record angle of tilt of the compensator in degrees.

Equations (22)

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R p = tan 2 ( i - r ) / tan 2 ( i + r ) R n = sin 2 ( i - r ) / sin 2 ( i + r ) .
T n = ( 1 - R n ) 2 ( 1 + R n 2 + R n 4 + ) = ( 1 - R n ) 2 / ( 1 - R n 2 ) = ( 1 - R n ) / ( 1 + R n ) ,
T p = ( 1 - R p ) / ( 1 + R p ) .
P = ( T p - T n ) / ( T p + T n ) .
tan A n = sin ( i - r ) / sin ( i + r )
tan ( 45 ° - A n ) = tan r / tan i , tan A p = tan ( i - r ) / tan ( i + r )
tan ( 45 ° - A p ) = sin 2 r / sin 2 i ,
T n = ( 1 - R n 1 + R p ) 2 × ( 1 + R n 2 ( 1 - R n ) ( 1 - R n ) [ 1 - R n 2 ( 1 - R n ) 2 ] )
C 0 tan 2 r + 2 C 1 tan r + C 2 = 0 ,
C 0 = sin 2 i · [ e 2 + ( o 2 - e 2 ) · sin 2 ϑ · cos 2 ζ ] - 1 ,
C 1 = sin 2 i · ( o 2 - e 2 ) sin ϑ · cos ϑ · cos ζ ,
C 2 = sin 2 i · ( o 2 cos 2 ϑ + e 2 sin 2 ϑ ) .
tan r 1 = ( 1 / C 0 ) [ - C 1 ± ( C 1 2 - C 0 C 2 ) 1 2 ] ,
tan r 2 = ( 1 / C 0 ) [ + C 1 ± ( C 1 2 - C 0 C 2 ) 1 2 ] .
Δ 1 = ( ( d · sin i ) / λ ) ( cot r 1 - cot r ω ) ,
Δ 2 = ( ( d · sin i ) / λ ) ( cot r 2 - cot r ω ) ,
Δ 1 - Δ 2 = ( ( d · sin i ) / λ ) ( cot r 1 - cot r 2 ) .
Δ 1 - Δ 2 = 2 · d sin i λ · C 1 C 2 = d · sin i λ · 2 · sin 2 ϑ · cos ζ ( o 2 + e 2 ) / ( o 2 - e 2 ) - cos 2 ϑ .
Δ 1 - Δ 2 = 0.15453104 · ( ( d · sin i ) / λ ) = 262.21924 · d · sin i .
d · sin i = 0.0038136.
I = cos 2 φ ,
P = ( T 1 - T 2 ) / ( T 1 + T 2 ) = ( 1 - cos 2 α ) / ( 1 + cos 2 α ) = cos 2 β