Abstract
Some error is introduced into the light distribution measurement of a lamp, because the reflection factor of the mirror system used for the measurement is influenced by the states of polarisation of incident light. For high pressure mercury vapour lamps and fluorescent mercury lamps, the states of polarisation of light emitted by them were measured and the following equation for evaluation of the error has been obtained by the theoretical treatment.
Δθ=ρ/2 [φθcos (αθ-βθ)-φ0cos (α0-β0)], where Δθ=the error in the relative value of luminous intensity in the direction which makes an angle θ with the normal to the axis of the inner tube of a mercury lamp, ρ=the degree of polarisation concerning the reflection factor of the mirror system, φθ =the degree of polarisation of luminous flux in the direction which makes an angle θ with the above normal, φ0 =the degree of polarisation of luminous flux in the direction of the normal, (αθ-βθ) =the phase difference between planes of the polarisation of luminous flux and reflection in the mirror system, in the case of the measurement of luminous intensity in the direction which makes an angle θ with the above normal, (α0-β0) =the phase difference between these planes, in the case of the measurement of luminous intensity in the direction of the normal.
Values of Δθ were calculated by the above equation and data concerning polarisation of light emitted by mercury lamps. As the result of it, errors introduced into the total flux of them have been estimated about 0.1-0.2% for general cases.
