Abstract

The problem of obtaining accurate photometric data at brightness levels below 0.5 foot-lambert is reviewed briefly. A method of calibrating a photoelectric photometer for heterochromatic measurements in this so-called Purkinje range is described with some details given of the design of the instrument used. By arbitrarily dividing the luminous emission of a tungsten lamp into twelve overlapping spectral bands it has been possible to calibrate a photometer, using a single correction filter for the phototube. The practical advantages of such a calibration include much time saved in brightness measurements on phosphor samples of different colors.

© 1952 Optical Society of America

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References

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  1. K. W. Weaver, J. Opt. Soc. Am. 39, 278 (1949).
    [CrossRef] [PubMed]
  2. J. R. DeVore, J. Opt. Soc. Am. 38, 692 (1948).
    [CrossRef] [PubMed]
  3. W. S. Plymale, Rev. Sci. Instr. 18, 535 (1947).
    [CrossRef]
  4. W. S. Plymale and D. F. Hansen, Electronics 23, 102 (February, 1950).
  5. W. E. Forsythe and E. Q. Adams, Denison Univ. Bull., J. Sci. Lab. 39, 55 (1945).

1950 (1)

W. S. Plymale and D. F. Hansen, Electronics 23, 102 (February, 1950).

1949 (1)

1948 (1)

1947 (1)

W. S. Plymale, Rev. Sci. Instr. 18, 535 (1947).
[CrossRef]

1945 (1)

W. E. Forsythe and E. Q. Adams, Denison Univ. Bull., J. Sci. Lab. 39, 55 (1945).

Adams, E. Q.

W. E. Forsythe and E. Q. Adams, Denison Univ. Bull., J. Sci. Lab. 39, 55 (1945).

DeVore, J. R.

Forsythe, W. E.

W. E. Forsythe and E. Q. Adams, Denison Univ. Bull., J. Sci. Lab. 39, 55 (1945).

Hansen, D. F.

W. S. Plymale and D. F. Hansen, Electronics 23, 102 (February, 1950).

Plymale, W. S.

W. S. Plymale and D. F. Hansen, Electronics 23, 102 (February, 1950).

W. S. Plymale, Rev. Sci. Instr. 18, 535 (1947).
[CrossRef]

Weaver, K. W.

Denison Univ. Bull., J. Sci. Lab. (1)

W. E. Forsythe and E. Q. Adams, Denison Univ. Bull., J. Sci. Lab. 39, 55 (1945).

Electronics (1)

W. S. Plymale and D. F. Hansen, Electronics 23, 102 (February, 1950).

J. Opt. Soc. Am. (2)

Rev. Sci. Instr. (1)

W. S. Plymale, Rev. Sci. Instr. 18, 535 (1947).
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Variation of luminous efficiencies with intensity for different color sources.

Fig. 2
Fig. 2

Complete photoelectric photometer for use on ordinary ac lines: (A) pick-up box, (B) control unit, (C) output meter.

Fig. 3
Fig. 3

Calibration curves for a 1P22 phototube corrected for photopic vision.

Fig. 4
Fig. 4

Computed spectral sensitivity curve (X) for the photometer relative to the scotopic (S) and photopic (P) curves.

Fig. 5
Fig. 5

Transmission curve for correction filter used on a 1P22 photomultiplier tube.

Fig. 6
Fig. 6

Schematic diagram of photometer as used. (M) mirror, (B) Lummer-Brodhun cube, (P) pick-up tube, (C) control lamp, (D) diffusing plates, (E) experimental source, (S) standard source, and (O) observer.

Fig. 7
Fig. 7

Photometer head for bench mounting.

Fig. 8
Fig. 8

Transmission curves of five of the filters used in the variable color source.

Fig. 9
Fig. 9

Six of the final calibration curves for the photometer with a phototube correction at twelve microlamberts.