A CCD line-scan system for road luminance measurement

摘要

Modern traffic route lighting is based on the 'luminance concept'. The design is based on the calculation of the average road surface luminance and the non-uniformity of the luminance pattern (and, of course, on other criteria as well, e.g. glare limitation). The calculations can be done with reasonable ease and accuracy using modern computers and the appropriate software, although a number of theoretical and practical problems need to be solved. Checking whether the lighting installation complies with the requirements and the design specifications directly after completion, and even more so after a considerable time in use, is at present very difficult to do. The road surface is a variable in the lighting installation with a considerable, but usually unknown, influence on the luminance. Another major problem is that there are no accurate, cheap and easy-to-use luminance meters available. The reason for this is that in measuring point luminances in road lighting (needed to define the non-uniformity), the measuring angle is very small (an observation angle of about one degree with the horizontal), the measuring field is very small (about two minutes in arc in diameter) and the luminances to be measured are very low, down to 0.05 cd/m2 or even less). This implies a meter that is very accurate and very sensitive, and extremely accurate in aiming — all this under outdoor weather conditions.