Glare indices

The Illuminating Engineering Society (lES) has produced a glare index system for the numerical evaluation of direct glare. This has become the standard system in the UK and is also used in certain other countries. 

Appropriate standards list the illuminance and the maximum glare index allowed for most tasks. Table 10.2 shows some examples of the illuminance required for some tasks. You are advised to refer to the bill document for more information. 

For many years in the UK, a glare index system has been in use for quantifying the effects of direct glare. It is also in use in certain other countries. 

EU standards for lighting use the Unified Glare Rating system in place of the glare index. 

Glare indexes are often difficult to calculate, but the flowchart in Figure 13.8 may be helpfiil in rapidly identifying particular glare problem areas. 

Situations in which glare is present should be eliminated or ameliorated a glare index of less than 19 is a minimum requirement. Color rendering index (CRl) > 80... 

However, in the 21st century, the ethical pharmaceutical industry has been fully geared towards the production of relatively safer, less toxic, more effective, higher therapeutic index, novel, innovative medicaments that will evidently help the mankind to afford a disease-free society besides, the elder ones with a glaring hope to live a still longer life span. 

The relationship between direct glare discomfort and the factors affecting it, viz. source brightness (Bs), background brightness (Bb), apparent size of the source angle (co), and an index (p) representing the position of the source in relation to the direction of vision, is as follows ... 

Dielectric coatings are thin transparent films or stacks of several thin films coated on a substrate so that there are abrupt changes of the refractive index at the interfaces. When a ray of light passes through this system, a partial wave is reflected at each interface. The refractive indices of the materials and the layer thicknesses are tuned so that destructive interference results at the wavelengths of interest Such coatings suffer less from a reduction in contrast than anti-glare surfaces. 

---