Moiré pattern
Interference pattern from overlaid similar patterns.
A moiré pattern is a large-scale interference pattern that emerges when two partially opaque, ruled patterns with transparent gaps are superimposed, provided the patterns are not perfectly identical. The patterns may be displaced, rotated, or have slightly different pitch (spacing). This phenomenon appears in numerous contexts. In printing, the dot pattern used can interfere with the image. In television and digital photography, a pattern on the subject being captured can interact with the arrangement of light sensors, producing unwanted artifacts. Conversely, moiré patterns are deliberately created in devices like micrometers to amplify the effects of very small movements. In physics, the effect is a manifestation of wave interference, analogous to the double-slit experiment or the beat phenomenon in acoustics.
The term “moiré” derives from the French word for a type of textile, historically made of silk but now also of cotton or synthetic fiber, which has a rippled or “watered” appearance. This fabric, called moire, is produced by pressing two layers of the textile while wet; the imperfect spacing of the threads creates a characteristic pattern that remains after drying. The French noun *moire* has been in use since the 17th century for “watered silk,” borrowed from the English word *mohair* (attested 1610). The verb *moirer*, meaning “to produce a watered textile by weaving or pressing,” appeared by the 18th century, and the adjective *moiré* formed from it has been used since at least 1823.
Moiré patterns are often an artifact of digital imaging and computer graphics, such as when scanning a halftone picture or ray tracing a checkered plane—a special case of aliasing due to undersampling a fine regular pattern. This can be mitigated in texture mapping through techniques like mipmapping and anisotropic filtering. The effect also occurs between overlapping transparent objects. For instance, an invisible phase mask made of transparent polymer with a wavy thickness profile, when overlaid with another similar mask, produces a broad moiré pattern on a distant screen. This phase moiré effect and the classical moiré effect from opaque lines represent two ends of a continuous optical spectrum, termed the universal moiré effect. The phase moiré effect is the basis for broadband interferometers in x-ray and particle wave applications and can reveal hidden pattern
- field
- Mathematics, physics, art
- known_for
- Large-scale wave interference pattern from overlaid patterns
- pronunciation_UK
- MWAH-ray
- pronunciation_US
- mwah-RAY
- French_pronunciation
- [mwaʁe]
Lore & Background
Moiré patterns are often an artifact of images produced by digital imaging and computer graphics techniques, such as scanning a halftone picture or ray tracing a checkered plane, which is a special case of aliasing due to undersampling. This can be overcome in texture mapping through mipmapping and anisotropic filtering. The nonlinear interaction of optical patterns of lines creates a real and visible pattern of roughly parallel dark and light bands superimposed on the lines. The moiré effect also occurs between overlapping transparent objects; for example, an invisible phase mask made of a transparent polymer with a wavy thickness profile, when light shines through two overlaid masks of similar phase patterns, produces a broad moiré pattern on a screen some distance away. This phase moiré effect and the classical moiré effect from opaque lines are two ends of a continuous spectrum in optics called the universal moiré effect.
Reader's Guide
Moiré patterns are significant because they appear in diverse fields, from printing and digital photography to physics and art. In printing, the printed pattern of dots can interfere with the image; in television and digital photography, a pattern on an object being photographed can interfere with the shape of light sensors to generate unwanted artifacts. They are also sometimes created deliberately; in micrometers, they are used to amplify the effects of very small movements. The phase moiré effect is the basis for a type of broadband interferometer in x-ray and particle wave applications and provides a way to reveal hidden patterns in invisible layers. Line moiré and shape moiré are specific types, with shape moiré demonstrating moiré magnification, which can magnify tiny shapes along one or both axes. The mathematical calculation of moiré patterns, such as for parallel patterns, shows that the distance between dark and pale zones depends on the step of the patterns and the discrepancy between them, similar to the Vernier scale. The legacy of moiré patterns lies in their dual role as both a nuisance to be mitigated and a useful tool for measurement and visual effects.
Did You Know?
- The term 'moiré' originates from a type of textile, historically made of silk, with a rippled or 'watered' appearance.
- Moiré patterns are used in micrometers to amplify the effects of very small movements.
- The phase moiré effect is the basis for a type of broadband interferometer in x-ray and particle wave applications.
- Shape moiré can magnify tiny shapes along one or both axes, a property called moiré magnification.
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