Abstract

This paper describes a technique for calculating the resultant contrast of displays incorporating various filters or filter combinations. In particular, contrast of such displays employing red or green light emitting diodes (LED’s) as the active elements is tabulated. The results indicate that adequate contrast enhancement of red LED’s in high light level environments is usually achieved using neutral density or bandpass filters with antireflective coatings. Green LED’S must be designed to have a high degree of specular reflectance so that a circular polarizer may be employed in order to achieve similar results. A discussion of required filter bandwidth to accommodate shifts in peak spectral output of LED’S due to manufacturer’s tolerances and temperature effects is also included.

© 1974 Optical Society of America

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References

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  1. W. D. Partlow, Appl. Opt. 11, 1491 (1972).
    [CrossRef] [PubMed]
  2. J. M. Ralston, “Filter Considerations For Light Emitting Diode Displays,” in Proceedings of the SID, Third Quarter1973, Vol. 1413, pp. 81–86.
  3. “Display Systems Engineering,” H. R. Luxenberg, Rudolph L. Kuehn, Eds. (McGraw-Hill, New York, 1968), pp. 106–107.
  4. D. M. Barton, IEEE Spectrum 0030 (Nov.1972).
    [CrossRef]
  5. R. W. Ahrons, Electron 0078 (22Nov.1971).

1972 (2)

1971 (1)

R. W. Ahrons, Electron 0078 (22Nov.1971).

Ahrons, R. W.

R. W. Ahrons, Electron 0078 (22Nov.1971).

Barton, D. M.

D. M. Barton, IEEE Spectrum 0030 (Nov.1972).
[CrossRef]

Partlow, W. D.

Ralston, J. M.

J. M. Ralston, “Filter Considerations For Light Emitting Diode Displays,” in Proceedings of the SID, Third Quarter1973, Vol. 1413, pp. 81–86.

Appl. Opt. (1)

Electron (1)

R. W. Ahrons, Electron 0078 (22Nov.1971).

IEEE Spectrum (1)

D. M. Barton, IEEE Spectrum 0030 (Nov.1972).
[CrossRef]

Other (2)

J. M. Ralston, “Filter Considerations For Light Emitting Diode Displays,” in Proceedings of the SID, Third Quarter1973, Vol. 1413, pp. 81–86.

“Display Systems Engineering,” H. R. Luxenberg, Rudolph L. Kuehn, Eds. (McGraw-Hill, New York, 1968), pp. 106–107.

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Figures (3)

Fig. 1
Fig. 1

Power spectra of the sun’s radiation reaching the earth and of a typical fluorescent lamp. Also included is the CIE photopic eye response.

Fig. 2
Fig. 2

Output spectrum of a green GaP LED with the transmission of an ideal green filter 4 and a hypothetical bandpass filter 5.

Fig. 3
Fig. 3

Output spectrum of a red GaAsP LED with the transmission of an ideal red filter 7 and a hypothetical bandpass filter 8.

Tables (2)

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Table I Contrast; Fluorescent Light Ambient

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Table II Contrast; Sunlight Ambient

Equations (11)

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C = L 1 + L 2 L 2 = I ( λ ) L ( λ ) d λ + K ( λ ) R ( λ ) L ( λ ) d λ K ( λ ) R ( λ ) L ( λ ) d λ ,
C = [ ( L 1 + L 2 ) L 3 ] / L 3 ,
C = ( T N L 1 + T N 2 L 2 ) / ( T N 2 L 2 ) ,
C = ( B L 1 + S L 2 ) / S L 2
B = I ( λ ) T ( λ ) L ( λ ) d λ I ( λ ) L ( λ ) d λ ,
S = K ( λ ) T 2 ( λ ) L ( λ ) d λ K ( λ ) L ( λ ) d λ
C = ( B L 1 + S L 2 ) / ( S L 2 ) ,
= F K ( λ ) T 1 ( λ ) T 2 ( λ ) L ( λ ) d λ + ( 1 F ) K ( λ ) T 1 2 ( λ ) L ( λ ) d λ K ( λ ) L ( λ ) d λ ,
B = I ( λ ) T 1 ( λ ) L ( λ ) d λ I ( λ ) L ( λ ) d λ ,
= K ( λ ) F ( λ ) L ( λ ) d λ K ( λ ) L ( λ ) d λ ,
L F = K ( λ ) R F ( λ ) L ( λ ) d λ ,

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