| 摘要 |
A flicker photometer comprises generating means (1, 8, 4) for generating two beams of light of different colours. Both beams are directed to a viewing means (190), and a subject can vary the intensity of light from one beam relative to the other. The colour of the light seen by the subject is caused to alternate. The performance of the photometer is improved by screens which scatter light before it reaches the subject. A first of the screens (186, 188) reflects light from one beam, whilst a second screen (b) is translucent, and thus 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 (1) to produce the light for both beams.
|
