The Three Components of Reflection

Beautiful darks in bright light. That's another way of saying that reflections from the display surface are under control. Perhaps we will see advertisements like this in the future. However, such a description is vague unless the reflection properties are clearly indicated. If we were to only state the familiar diffuse and specular reflection properties, would the specifications be adequate? Not really, you may still not know how the display will look to your eye. This article will show that there are three components of reflection with which we must contend in order to properly describe display reflection as it is perceived by the eye. This is not a criticism of existing reflection measurement methods and recommended practices. The appearance of an electronic display to the eye may require a more complete description than the appearance of fabric or paint. What we offer here is an extension to existing reflection specifications. When considering reflection properties, people often think of specular reflection (mirror like) and diffuse reflection (as with surfaces like common copy paper or walls painted with flat or matte paint). With specular reflection—as with a mirror—the observed luminance in the virtual image is proportional to the luminance of the source. This is obvious—the luminances of the reflected images in a mirror don't depend upon their distance from the mirror just as when we observe the objects directly. With the so-called diffuse reflection, many people think in terms of Lambertian reflection where the luminance of the surface is independent of the direction from which the surface is observed and only depends upon the illuminance of that surface—a perfect Lambertian surface has not yet been realized in practice. The problem here is, in the display industry, the terms " diffuse " and " Lambertian " have been sometimes thought of as meaning the same thing, and that is generally not the case for displays. According to the ASTM, a diffuser is a surface that takes light energy away from the specular direction and distributes it is many other directions. [1] The term is not constrained to refer only to a Lambertian surface. So, it makes sense to use the term " Lambertian " for reflectance properties associated with a perfect diffuse reflection. [2] In Fig. 2. we show four different screens showing the same size text (linear size on the screen) with a black-white-metal target on the front surface to assure …