| 摘要 |
The invention concerns an improved retroreflectometer giving direct readings for measuring the value or degree of retroreflectivity, or visibility at night, of a paint applied to the surface of the road for marking ground signs, under conditions that simulate geometrically the real conditions of illumination and visibility of the sign from the driver of a vehicle. The value or degree of retroreflectivity is measured directly from the sample in question, making it unnecessary to have a sample for comparative purposes and, as a result, eliminating the need to zero the apparatus before each measurement is taken. Provision is made for varying the angle at which the light beam strikes the sample, so as to simulate the actual conditions produced by different heights and/or degrees of inclination of the headlights of different categories of vehicles, and to vary the degree of inclination of the detecting element in relation to the retroreflected beam, so as to simulate the visual angle of the driver, and thus alter the angle of divergence, or phase displacement angle, between the incident beam and the retroreflected beam. The detected data are processed, stored and transduced, so as to be readable on a known type of display. |
