Abstract

The Beckman spectrophotometer Model DU has proved to be a useful instrument for measuring spectral directional reflectance. Like other spectrophotometers it is subject to slit-width and stray-energy errors. The magnitude of these errors and techniques for minimizing them are discussed. The viewing geometry and an adaptor for four-inch square specimens are described.

© 1952 Optical Society of America

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References

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  1. H. H. Cary and A. O. Beckman, J. Opt. Soc. Am. 31, 682 (1941).
    [Crossref]
  2. K. S. Gibson and M. M. Balcom, J. Research Natl Bur. Standards 38, 601, RP1798 (1947), J. Opt. Soc. Am. 37, 593 (1947).
    [Crossref]
  3. , National Technical Laboratories, (December1944).
  4. Commission International de L’Eclairage, Compt. rend., 8th Session, Cambridge, Resolution 3 (September 1931), page 23.
  5. K. S. Gibson, “Spectrophotometry,” Natl. Bur. Standards Circular, 484 (1949).
  6. “Preparation and Colorimetric Properties of a Magnesium Oxide Reflectance Standard,” Natl. Bur. Standards,  LC547 (1939).
  7. W. E. Knowles Middleton and C. L. Sanders, J. Opt. Soc. Am. 41, 419 (1951).
    [Crossref]
  8. Natl. Bur. Standards Letter Circular LC929, “Standards for checking the calibration of spectrophotometers” (1948).
  9. Memorandum accompanying reports on the spectral directional reflectance of Vitrolite working standards, Natl. Bur. Standards (January10, 1949).
  10. , National Technical Laboratories, (February, 1947).
  11. IES Lighting Handbook (1947), first edition, section 6, p. 10.
  12. W. E. Forsythe, editor, Measurement of Radiant Energy (McGraw-Hill Book Company, Inc., New York and London, 1937).
  13. Commercial Standard CS62-38, Colors for Kitchen Accessories (1938).

1951 (1)

1949 (1)

K. S. Gibson, “Spectrophotometry,” Natl. Bur. Standards Circular, 484 (1949).

1948 (1)

Natl. Bur. Standards Letter Circular LC929, “Standards for checking the calibration of spectrophotometers” (1948).

1947 (1)

K. S. Gibson and M. M. Balcom, J. Research Natl Bur. Standards 38, 601, RP1798 (1947), J. Opt. Soc. Am. 37, 593 (1947).
[Crossref]

1941 (1)

1939 (1)

“Preparation and Colorimetric Properties of a Magnesium Oxide Reflectance Standard,” Natl. Bur. Standards,  LC547 (1939).

1938 (1)

Commercial Standard CS62-38, Colors for Kitchen Accessories (1938).

Balcom, M. M.

K. S. Gibson and M. M. Balcom, J. Research Natl Bur. Standards 38, 601, RP1798 (1947), J. Opt. Soc. Am. 37, 593 (1947).
[Crossref]

Beckman, A. O.

Cary, H. H.

Gibson, K. S.

K. S. Gibson, “Spectrophotometry,” Natl. Bur. Standards Circular, 484 (1949).

K. S. Gibson and M. M. Balcom, J. Research Natl Bur. Standards 38, 601, RP1798 (1947), J. Opt. Soc. Am. 37, 593 (1947).
[Crossref]

Knowles Middleton, W. E.

Sanders, C. L.

Colors for Kitchen Accessories (1)

Commercial Standard CS62-38, Colors for Kitchen Accessories (1938).

J. Opt. Soc. Am. (2)

J. Research Natl Bur. Standards (1)

K. S. Gibson and M. M. Balcom, J. Research Natl Bur. Standards 38, 601, RP1798 (1947), J. Opt. Soc. Am. 37, 593 (1947).
[Crossref]

Natl. Bur. Standards (1)

“Preparation and Colorimetric Properties of a Magnesium Oxide Reflectance Standard,” Natl. Bur. Standards,  LC547 (1939).

Natl. Bur. Standards Circular, 484 (1)

K. S. Gibson, “Spectrophotometry,” Natl. Bur. Standards Circular, 484 (1949).

Natl. Bur. Standards Letter Circular LC929 (1)

Natl. Bur. Standards Letter Circular LC929, “Standards for checking the calibration of spectrophotometers” (1948).

Other (6)

Memorandum accompanying reports on the spectral directional reflectance of Vitrolite working standards, Natl. Bur. Standards (January10, 1949).

, National Technical Laboratories, (February, 1947).

IES Lighting Handbook (1947), first edition, section 6, p. 10.

W. E. Forsythe, editor, Measurement of Radiant Energy (McGraw-Hill Book Company, Inc., New York and London, 1937).

, National Technical Laboratories, (December1944).

Commission International de L’Eclairage, Compt. rend., 8th Session, Cambridge, Resolution 3 (September 1931), page 23.

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Figures (10)

Fig. 1
Fig. 1

Schematic cross section of Beckman reflectance attachment showing geometry of irradiation and reception. D, slit; L, lens; M, mirror; S, specimen; R, ellipsoidal reflector; P, diffusing quartz plate; H, phototube envelope.

Fig. 2
Fig. 2

Holder for large specimens, shown mounted on under side of reflectance attachment. Standard and specimen may be easily inserted and removed from the instrument operating position.

Fig. 3
Fig. 3

Determination of wavelength at which phototubes should be interchanged in reflection measurement. Specimen: white Vitrolite. No stray-energy filters in spectrophotometer. Phototube: Blue, ○; red, ×. Sensitivity control position: counterclockwise limit. Instrument: No. 1, – – – –; No. 2, ———.

Fig. 4
Fig. 4

Comparison of phototube response: Incandescent source, single quartz monochrometer, nominal band width 3 mμ. Phototube: Blue, ———; red, – – – – (This is a reproduction of Fig. 4 of the paper by Cary and Beckman, J Opt. Soc. Am. 31, 682 (1941).)

Fig. 5
Fig. 5

Determination of wavelength at which phototubes should be interchanged in reflection measurement. Specimen: white Vitrolite. Stray-energy filters in spectrophotometer. Phototube and filter: blue with Corning 2424, ○; red with Corning 3965, ×. Sensitivity control position: counterclockwise limit. Instrument: No. 1, – – – –; No. 2, ———.

Fig. 6
Fig. 6

Slit-width reduction with increasing lamp voltage, wavelength 640 mμ, blue-sensitive phototube, sensitivity control position counterclockwise limit.

Fig. 7
Fig. 7

Schematic circuit for 8-volt battery connection. S, spectrophotometer; P, phototube housing; L, lamp housing; B, battery; CB, battery cable; CL, lamp cable.

Fig. 8
Fig. 8

Total and stray energy curves for tungsten source, quartz prism monochrometer and caesium-oxide phototube. Total, ———; stray, – – – –. (This is a reproduction of Fig. 2 of paper by Cary and Beckman, J. Opt. Soc. Am. 31, 682 (1941)).

Fig. 9
Fig. 9

Spectral reflectance data for a typical red specimen, showing usual discrepancies between readings obtained with blue and red phototubes. Blue, ○; red, ×.

Figure 10
Figure 10

Discrepancies in spectral reflectance measurements averaged for several red, orange, and yellow specimens. Without stray-energy filters, ●; blue phototube with Corning 2424 and red phototube with Corning 3965, ×.

Tables (3)

Tables Icon

Table I Kitchen red panel.

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Table II Chrome yellow panel.

Tables Icon

Table III Slit width data for reflectance measurement.