Abstract

In order to characterize the light scattered by eye protection filters a reduced luminance coefficient l* = Ls/τE is defined: Ls luminance of scattered light, τ directional transmittance of the filter, E illuminance of incident radiation. The possibilities of measuring this quantity, which is specific for the material concerned [unit (cd/m2)/lx = sr−1] are discussed, and a method is described which also fulfills the ophthalmological conditions; this is demonstrated for filters used in welding. By comparison measurements with an earlier American method, which gives the percentage of the scattered light, it is shown that a value l* = (1 cd/m2)/lx is equivalent to 0.8% scattered light.

© 1968 Optical Society of America

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References

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  1. E. Hartmann, Institut für medizinische Optik, Universität München, personal communication; see also Lichttechnik 19, 70A (1967).

Hartmann, E.

E. Hartmann, Institut für medizinische Optik, Universität München, personal communication; see also Lichttechnik 19, 70A (1967).

Other (1)

E. Hartmann, Institut für medizinische Optik, Universität München, personal communication; see also Lichttechnik 19, 70A (1967).

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Figures (5)

Fig. 1
Fig. 1

Derivation of the reduced luminance coefficient: O—light emitting object, S—scattering filter, rf—distance OS, ω1—solid angle, viewing the object from the filter.

Fig. 2
Fig. 2

Scheme of the sum method: O—source, L1—lens forming a parallel beam, B1—and B2—diaphragms, E—detector, re—distance B2E. Filter S first at diaphragm B1, secondly at diaphragm B2.

Fig. 3
Fig. 3

Scheme of the difference method: O—light emitting object, B—diaphragm, S—scattering filter, rf—distance OS, re—distance SE, r = rf + re; ω1, ω2, ω3—solid angles. Detector E first in position I, secondly in position II, φ—angle between the direction of both positions.

Fig. 4
Fig. 4

Scheme of the ring diaphragm method: O—source, M—mirror illuminating the small hole B0, L1—quartz lens, S—filter, L2, L3—achromatic glass lenses, BR—ring diaphragm, BH—circular aperture, G—ground glass in front of the photomultiplier P,ω—solid angle of the measured scattered light. (a) Determination of Φ1, filter in position I; (b) determination of Φ2, filter in position I; (c) determination of Φ3, filter in position II.

Fig. 5
Fig. 5

Comparison of scattering quotient S and reduced luminance coefficient l*. S refers here to the method of the American and Canadian Standards (haze test).

Equations (12)

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L s = l E f .
L g = L τ + L s .
L s = l ( L F / r f 2 ) ω 0 = l L ω 1 ,
V = L s / L g = 1 1 + ( τ / l ω 1 ) .
l * = l / τ .
V = 1 1 + ( 1 / l * ω 1 ) .
l * = L s / E f τ .
l * = [ V / ( 1 - V ) ] ( 1 / ω 1 ) .
S = ( a 2 - a 1 ) / a 2 × 100 in % .
l * = [ S / ( 1 - S ) ] ( r e α / ω 0 F e c ) .
l * = [ E ¯ s / ( E ¯ g cos φ - E ¯ s ) ] ( ω 2 / ω 1 ω 3 ) .
l * = ( 1 / ω ) [ ( Φ 2 - Φ 3 ) Φ 1 ] ,

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