FLICKER PHOTOMETER

摘要

A flicker photometer comprises generating means for generating two beams of light of different colours. Both beams are directed to a viewing means and a subject can vary the intensity of light from one beam relative to other. The colour of the light seen by the subject is caused to alternate by a shutter which is rotated about an axis by a motor, the shutter having a portion which extends non-perpendicularly relative to the axis to facilitate a compact construction of photometer. The performance of the photometer is improved by screens which scatter light before it reaches the subject. A first of the screens reflects light from one beam, whilst a second screen transmits light from the other. If light of wavelengths to which the eye is less sensitive is passed through the second screen, whilst light of a wavelength to which the eye is more sensitive passes through the first screen, the screens help to make it practicable for the generating means to use a single lamp to produce the light for both beams.