Abstract

A new device is described with which screws of any length can be calibrated rapidly for both periodic and cumulative errors in terms of interference fringes. It can also be used to plot correction cams to remove fixed errors of translation or rotation, and to monitor the operation of an engine while ruling diffraction gratings or scales, correcting by automatic feedback differences between the actual carriage position and its proper position as shown by an optical interference field. This so-called “Commensurator,” whose name arises from its function of overcoming the incommensurability of the wavelength of the light used for calibration and the lead of a screw with English or metric threads, consists principally of a screw drive system, eight-figure dials, and a generator, geared together in ratios that can be controlled to one part in 108. Fringes produced by a Michelson interferometer mounted on the ruling engine (or having one mirror moved by the nut of the screw being calibrated) are changed photoelectrically to a wave train that measures translation to within 0.1 micro-inch. A second wave train of almost identical average frequency is produced by the Commensurator generator to measure screw rotation, and the two trains are continuously compared by means of a phase-sensitive amplifier and motor to within 1/100 cycle or fringe. Any error in carriage translation appears as a lag or lead which produces a torque in the motor until synchronism is re-established by a relative shift of the two wave trains, and thus makes possible automatic plotting of the screw error curve on a moving chart. Corrections for changes in barometric pressure or in temperature can be introduced during operation. By means of this device the variations in lead of a screw having 14 inches of nut motion have been recorded to the nearest 0.2 micro-inch in eight hours. When the error signals of the Commensurator are fed back directly to the corrector mechanism of a ruling engine, transient as well as fixed errors of run and period can be automatically compensated for. If the fringe system is lost, it can be re-established from the Commensurator record, so that controlled ruling of gratings wider than any available coherent fringe-field appears possible. During any period in which fringe control is not exerted the engine operates in the orthodox manner.

© 1951 Optical Society of America

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References

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  1. See G. R. Harrison, J. Opt. Soc. Am. 39, 419 (1949).
  2. A. A. Michelson, J. Franklin Inst. 181, 785 (1916).
    [Crossref]
  3. H. G. Gale, Astrophys. J. 86, 437 (1937). Richardson, Wiley, and Sheldon, J. Opt. Soc. Am. 40, 259 (1950).
    [Crossref]
  4. T. J. O’Donnell (private communication). A. A. Michelson, reference 2.
  5. H. G. Gale, reference 3.
  6. G. R. Harrison and J. E. Archer, J. Opt. Soc. Am. 40, 259 (1950).
  7. G. R. Harrison, Phys. Today 3, 6 (1950).
    [Crossref]
  8. A. A. Michelson, Studies in Optics (University of Chicago Press, Chicago, Illinois, 1927), pp. 46 and 100. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1936), third edition, pp. 254 and 298. R. F. Stamm, U. S. Patent No. 2,527,-338 (1950).
  9. A. A. Michelson, Light Waves and Their Uses (University of Chicago Press, 1903), p. 78. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1905), first edition, p. 218.
  10. J. H. Wiens, Phys. Rev. 70, 910 (1946).
    [Crossref]
  11. W. F. Meggers, Sci. Monthly 68, 3 (1949). P. Bradt and F. L. Mohler, Phys. Rev. 73, 925L (1948).
    [Crossref]
  12. W. F. Meggers and F. O. Westfall, J. Research Natl. Bur. Standards 44, 447 (1950); W. F. Meggers and K. G. Kessler, J. Opt. Soc. Am. 40, 737 (1950).
    [Crossref]
  13. J. E. Archer and G. R. Harrison, J. Opt. Soc. Am. 41, 285 (1951).
  14. Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
    [Crossref]
  15. W. F. Meggers and C. G. Peters, Bull. Natl. Bur. Standards 14, 697 (1918).
    [Crossref]

1951 (1)

J. E. Archer and G. R. Harrison, J. Opt. Soc. Am. 41, 285 (1951).

1950 (3)

G. R. Harrison and J. E. Archer, J. Opt. Soc. Am. 40, 259 (1950).

G. R. Harrison, Phys. Today 3, 6 (1950).
[Crossref]

W. F. Meggers and F. O. Westfall, J. Research Natl. Bur. Standards 44, 447 (1950); W. F. Meggers and K. G. Kessler, J. Opt. Soc. Am. 40, 737 (1950).
[Crossref]

1949 (2)

See G. R. Harrison, J. Opt. Soc. Am. 39, 419 (1949).

W. F. Meggers, Sci. Monthly 68, 3 (1949). P. Bradt and F. L. Mohler, Phys. Rev. 73, 925L (1948).
[Crossref]

1946 (1)

J. H. Wiens, Phys. Rev. 70, 910 (1946).
[Crossref]

1937 (1)

H. G. Gale, Astrophys. J. 86, 437 (1937). Richardson, Wiley, and Sheldon, J. Opt. Soc. Am. 40, 259 (1950).
[Crossref]

1936 (1)

Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
[Crossref]

1918 (1)

W. F. Meggers and C. G. Peters, Bull. Natl. Bur. Standards 14, 697 (1918).
[Crossref]

1916 (1)

A. A. Michelson, J. Franklin Inst. 181, 785 (1916).
[Crossref]

Archer, J. E.

J. E. Archer and G. R. Harrison, J. Opt. Soc. Am. 41, 285 (1951).

G. R. Harrison and J. E. Archer, J. Opt. Soc. Am. 40, 259 (1950).

Brown,

Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
[Crossref]

Gale, H. G.

H. G. Gale, Astrophys. J. 86, 437 (1937). Richardson, Wiley, and Sheldon, J. Opt. Soc. Am. 40, 259 (1950).
[Crossref]

H. G. Gale, reference 3.

Harrison, G. R.

J. E. Archer and G. R. Harrison, J. Opt. Soc. Am. 41, 285 (1951).

G. R. Harrison and J. E. Archer, J. Opt. Soc. Am. 40, 259 (1950).

G. R. Harrison, Phys. Today 3, 6 (1950).
[Crossref]

See G. R. Harrison, J. Opt. Soc. Am. 39, 419 (1949).

Hazen,

Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
[Crossref]

Jaeger,

Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
[Crossref]

Meggers, W. F.

W. F. Meggers and F. O. Westfall, J. Research Natl. Bur. Standards 44, 447 (1950); W. F. Meggers and K. G. Kessler, J. Opt. Soc. Am. 40, 737 (1950).
[Crossref]

W. F. Meggers, Sci. Monthly 68, 3 (1949). P. Bradt and F. L. Mohler, Phys. Rev. 73, 925L (1948).
[Crossref]

W. F. Meggers and C. G. Peters, Bull. Natl. Bur. Standards 14, 697 (1918).
[Crossref]

Michelson, A. A.

A. A. Michelson, J. Franklin Inst. 181, 785 (1916).
[Crossref]

A. A. Michelson, Studies in Optics (University of Chicago Press, Chicago, Illinois, 1927), pp. 46 and 100. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1936), third edition, pp. 254 and 298. R. F. Stamm, U. S. Patent No. 2,527,-338 (1950).

A. A. Michelson, Light Waves and Their Uses (University of Chicago Press, 1903), p. 78. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1905), first edition, p. 218.

T. J. O’Donnell (private communication). A. A. Michelson, reference 2.

O’Donnell, T. J.

T. J. O’Donnell (private communication). A. A. Michelson, reference 2.

Peters, C. G.

W. F. Meggers and C. G. Peters, Bull. Natl. Bur. Standards 14, 697 (1918).
[Crossref]

Westfall, F. O.

W. F. Meggers and F. O. Westfall, J. Research Natl. Bur. Standards 44, 447 (1950); W. F. Meggers and K. G. Kessler, J. Opt. Soc. Am. 40, 737 (1950).
[Crossref]

Wiens, J. H.

J. H. Wiens, Phys. Rev. 70, 910 (1946).
[Crossref]

Astrophys. J. (1)

H. G. Gale, Astrophys. J. 86, 437 (1937). Richardson, Wiley, and Sheldon, J. Opt. Soc. Am. 40, 259 (1950).
[Crossref]

Bull. Natl. Bur. Standards (1)

W. F. Meggers and C. G. Peters, Bull. Natl. Bur. Standards 14, 697 (1918).
[Crossref]

J. Franklin Inst. (1)

A. A. Michelson, J. Franklin Inst. 181, 785 (1916).
[Crossref]

J. Opt. Soc. Am. (3)

See G. R. Harrison, J. Opt. Soc. Am. 39, 419 (1949).

G. R. Harrison and J. E. Archer, J. Opt. Soc. Am. 40, 259 (1950).

J. E. Archer and G. R. Harrison, J. Opt. Soc. Am. 41, 285 (1951).

J. Research Natl. Bur. Standards (1)

W. F. Meggers and F. O. Westfall, J. Research Natl. Bur. Standards 44, 447 (1950); W. F. Meggers and K. G. Kessler, J. Opt. Soc. Am. 40, 737 (1950).
[Crossref]

Phys. Rev. (1)

J. H. Wiens, Phys. Rev. 70, 910 (1946).
[Crossref]

Phys. Today (1)

G. R. Harrison, Phys. Today 3, 6 (1950).
[Crossref]

Rev. Sci. Instr. (1)

Hazen, Jaeger, and Brown, Rev. Sci. Instr. 7, 353 (1936).
[Crossref]

Sci. Monthly (1)

W. F. Meggers, Sci. Monthly 68, 3 (1949). P. Bradt and F. L. Mohler, Phys. Rev. 73, 925L (1948).
[Crossref]

Other (4)

A. A. Michelson, Studies in Optics (University of Chicago Press, Chicago, Illinois, 1927), pp. 46 and 100. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1936), third edition, pp. 254 and 298. R. F. Stamm, U. S. Patent No. 2,527,-338 (1950).

A. A. Michelson, Light Waves and Their Uses (University of Chicago Press, 1903), p. 78. R. W. Wood, Physical Optics (The Macmillan Company, New York, 1905), first edition, p. 218.

T. J. O’Donnell (private communication). A. A. Michelson, reference 2.

H. G. Gale, reference 3.

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Figures (12)

Fig. 1
Fig. 1

The Commensurator from above, as operated in an anteroom by amplidyne control from the ruling engine.

Fig. 2
Fig. 2

Block diagram of the Commensurator shown in Fig. 1, with arrangement for direct feedback of screw error to balance generator and fringe signals.

Fig. 3
Fig. 3

Interferometer system for measuring ruling-engine carriage translation in terms of the variation in output of a photomultiplier.

Fig. 4
Fig. 4

Block diagram of the circuit used to compare in phase the two wave trains measuring rotation of the engine screw and translation of the main carriage. O1 and O2 are oscilloscopes. The large rectangle in the upper right represents the Commensurator with correction feedback to the ruling engine dashed in.

Fig. 5
Fig. 5

Simplified circuit diagram of the phase comparator.

Fig. 6
Fig. 6

Two portions of traced Commensurator records of the error curve of a screw as tested with a nut making contact with only a small section of a single thread. In the original record errors of 2×10−7 in. can be read with certainty.

Fig. 7
Fig. 7

Portions of three successive runs with a single contact nut. The top and bottom curves were run in one direction, and the middle curve in the opposite direction, with slight differences in temperature and barometric pressure. The small variations are of the order of 2×10−7 in. The smallest scale divisions correspond to twentieths of a screw turn.

Fig. 8
Fig. 8

Below: an aluminum disk one mm thick cut to form one turn of a helical cam. Above: two such disks after corrections have been plotted by Commensurator in polar coordinates, and disks have been shaped to proper curves.

Fig. 9
Fig. 9

Block diagram of feedback connections from curve follower. F. B. No. 1 is the direct mechanical feedback to the Commensurator generator, used when plotting an error curve. F. B. No. 2 and F. B. No. 3 are correction feedbacks to the ruling engine, one from the curve follower through one lever, and the other direct from the balancing motor through another.

Fig. 10
Fig. 10

Compound lever system for introducing two separate corrections to the worm drive from two selsyn repeaters. The lever AB is a continuous bar, to which another lever is attached near its center to communicate the greatly reduced vertical motion of the point of attachment to the thrust bearing of the vertical worm shaft. The bearing just to the right of this shaft is attached to the engine mount, while the others are free.

Fig. 11
Fig. 11

Selsyn repeater arranged for feeding correction into ruling engine through a lever, without introducing heat or vibration. One of the stirrers in the oil vat of the engine is visible near the top, and the belt drive of the engine, and the selsyn transmitting the engine screw rotation signal to the Commensurator, appear in the lower right.

Fig. 12
Fig. 12

Chart of the relation m=0.3290 LP, used to introduce corrections for variation in barometric pressure. The ordinates are changes in barometric pressure in inches since the start of the run; abscissas are changes in separation in mm between the two interferometer mirrors measuring carriage translation. The curves are spaced 1/100 fringe apart. This chart is mounted on a drum on the Commensurator, and rotates as calibrating or ruling progresses. Each time one of the hyperbolae is crossed an appropriate correction is introduced in the proper sense through an additive differential on the Commensurator.

Equations (2)

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10 7 ( n - 1 ) = 2726.43 + 12.288 / λ 2 × 10 - 8 + 0.3555 / λ 4 × 10 - 16
Δ m = 0.3290 ( l 0 - l 1 + Δ l ) Δ P + [ 1 + 8.9844 P i × 10 - 6 ] Δ l 0.27311 × 10 - 4 ,