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Concept
Laser lighting display
Résumé
A laser lighting display or laser light show involves the use of laser light to entertain an audience. A laser light show may consist only of projected laser beams set to music, or may accompany another form of entertainment, typically musical performances.
Laser light is useful in entertainment because the coherent nature of laser light allows a narrow beam to be produced, which allows the use of optical scanning to draw patterns or images on walls, ceilings or other surfaces including theatrical smoke and fog without refocusing for the differences in distance, as is common with video projection. This inherently more focused beam is also extremely visible, and is often used as an effect. Sometimes the beams are "bounced" to different positions with mirrors to create laser sculptures.
Laser scanners reflect the laser beam on small mirrors which are mounted on galvanometers to which a control voltage is applied. The beam is deflected a certain amount which correlates to the amount of voltage applied to the galvanometer scanner. Two galvanometer scanners can enable X-Y control voltages to aim the beam to any point on a square. This is called vector scanning. This enables the laser lighting designer to create patterns such as Lissajous figures (such as are often displayed on oscilloscopes); other methods of creating images through the use of galvanometer scanners and X-Y control voltages can generate letters, shapes, and even complicated and intricate images. A planar or conical moving beam aimed through atmospheric smoke or fog can display a plane or cone of light known as a "laser tunnel" effect.
A less complicated way of spreading the laser beam is by means of diffraction. A grating splits the monochromatic light into several rays, and by using holograms, essentially complicated gratings, the beam can be split into various patterns.
Diffraction uses something referred to as the Huygens-Fresnel principle. The basic idea is that on every wavefront exists a forward propagating spherical wavelet of light.
Source officielle
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