Diffuse reflection is a reflection of light or wave or other particle from the surface such that the incidence of light on the surface is spread over many angles rather than at one angle as in the case of specular reflection. The reflective surface reflects the ideal is said to exhibit Lambertian reflection, which means that there is the same luminance when viewed from all directions located in half the space adjacent to the surface.
Surfaces constructed from non-absorbing powders such as plaster, or from fibers such as paper, or from polycrystalline materials such as white marble, reflect light diffusely with great efficiency. Many common ingredients show a mixture of specular and diffuse reflections.
The visibility of objects, excluding those that emit light, is mainly due to the diffuse reflection of light: the scattered light scattered that forms the image of the object in the eye of the observer.
Video Diffuse reflection
Mekanisme
Diffuse reflections of solids are generally not due to surface roughness. A flat surface is necessary to provide speculative reflection, but does not prevent spreading reflections. A very fine piece of white marble remains white; there is no amount of polishing that will turn it into a mirror. The poles produce some specular reflections, but the remaining light continues to diffuse reflected.
The most common mechanism in which the surface gives a diffuse reflection does not involve exactly the surface: most of the light is contributed by centers scattering beneath the surface, as illustrated in Figure 1. If one imagines that the image symbolizes snow, and that the polygon is its ice crystals (transparent), the partially reflected beam (a few percent) by the first particle, enters into it, again reflected by the interface with the second particle, enters it, overrides on the third, and so forth, a series of "primers" scattered rays in random directions, which, in turn, through the same mechanism, produce a large number of "secondary" scattered rays, which produce "tertiary" rays, All these rays run through crystallytes of snow, which do not absorb light, until they arrive at the surface and come out randomly. The result is that the transmitted light is returned in all directions, so the snow is white even though it is made of transparent material (ice crystals).
For simplicity, "reflection" is pronounced here, but more commonly the interface between small particles which is a lot of irregular material on a scale that is proportional to the wavelength of light, so the diffused light is generated on each interface, rather than a single reflected ray, but the story may said in the same way.
This mechanism is very common, because almost all the general material is made of "little things" that are put together. Mineral materials are generally polycrystalline: one can describe them as being made of 3D mosaics of irregular and irregularly shaped small crystals. Organic matter usually consists of fibers or cells, with their internal membranes and complex structures. And any interface, inhomogeneity or imperfection can deviate, reflect or diffuse light, reproduce the above mechanism.
Some materials do not cause diffuse reflections: among which are metals, which do not allow incoming light; gases, liquids, glass, and transparent plastic (having an amorphous microscopic structure such as a liquid); single crystals, such as some gems or salt crystals; and some very special materials, such as the tissue that makes the cornea and the lens of the eye. These materials can diffuse diffusely, however, if the surface is roughly microscopic, as in ice glass (Fig. 2), or, of course, if their homogeneous structure deteriorates, as in eye lens cataracts.
The surface can also exhibit speculative and diffuse reflections, as well as, for example, glossy paint as used in house painting, which also gives the fraction of speculative reflection, while matte paint gives almost exclusively spreading reflections.
Most materials can provide some specular reflections, provided the surface can be polished to remove irregularities that are proportional to the wavelength of light (a fraction of a micrometer). Depending on the material and surface roughness, reflection may be largely speculative, mostly dispersed, or anywhere in between. Some materials, such as liquids and glasses, do not have an internal subdivision that produces the subsurface scattering mechanism described above, and so give only speculative reflection. Among the common materials, only polished metal can reflect light speculatively with high efficiency, as in aluminum or silver which is usually used in mirrors. All other common ingredients, even when perfectly polished, typically give no more than a few percent of specular reflections, except in certain cases, such as angular reflection by lake, or total reflection from the glass prism. , or when structured in certain complex configurations such as silver skin of many species of fish or reflective surfaces of dielectric mirrors. Diffuse reflections can be very efficient, as in white matter, because of the sum of many subsurface reflections.
Maps Diffuse reflection
Colored objects
Up to this point the white matter has been discussed, which does not absorb light. But the above scheme continues to apply in the case that the material is absorbed. In this case, diffused rays will lose some wavelengths as they run on the material, and will appear colored.
Diffusion affects the color of the object substantially because it determines the average path of light in the material, and hence the extent to which wavelengths are absorbed. Red ink looks black while in the bottle. The living color is felt only when placed on scattering material (eg paper). This is because the light path through the paper fiber (and through ink) is only a fraction of a millimeter long. However, the light from the bottle has passed several centimeters of ink and has been widely absorbed, even in its red wavelength.
And, when colored objects have diffuse and specular reflections, usually only dyed colored components. A cherry reflects red light that emanates, absorbing all other colors and has a basically white reflection (if incident light is white light). This is quite common, since, except for metals, the reflection of most materials depends on the refractive index, which is slightly different from the wavelength (although this variation causes the chromatic dispersion in the prism), so that all colors are reflected. almost with the same intensity. Reflections from different origins, on the other hand, can be colored: metallic reflections, such as gold or copper, or interferential reflections: iridescences, peacock feathers, butterfly wings, elytra beetles, or antireflection lenses.
Important for vision
Looking at the surroundings of a person, most of the objects are seen to be seen primarily by the diffuse reflections from the surface. This applies with some exceptions, such as glass, reflective fluid, fine metal or polish, glossy objects, and light-emitting objects: The sun, lights, and computer screens (which, however, radiate diffuse light. Beyond it is the same, perhaps with the exception of transparent streams or colorful beetles. In addition, Rayleigh scattering is responsible for the sky blue color, and Mie scatter for the white color of water droplets from the clouds.
The light scattered from the surface of matter is by far the main light observed by humans visually.
Interreflection
Diffuse interreflection is the process by which light reflected from an object attacks other objects in the surrounding area, illuminating them. Diffy interreflection typically describes reflected light from non-gloss or specular objects. In real life what this means is that light is reflected from a non-glazed surface such as earth, walls, or fabric, to reach an area that is not directly in the light source's view. If the diffuse surface is colored, reflected light is also colored, producing the same color of the objects around it.
In 3D computer graphics, diffuse interreflection is an essential component of global illumination. There are a number of ways to model diffuse interreflection when displaying a scene. Radiosity and photon mapping are two commonly used methods.
See also
- Diffuser
- Reflective Power
- Oren-Nayar bounce model
References
Source of the article : Wikipedia
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