Collimated light is light whose rays are parallel. Light can be collimated by a number of processes, the easiest being to shine it on a parabolic concave mirror with the source at the focus. Collimated light is sometimes said to be focused at infinity. Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... A mirror is a reflective surface that is smooth enough to form an image. ... The focus, or focal point of a lens or parabolic mirror is the point onto which collimated light parallel to the axis is focused. ...

Laser light is often collimated due to being formed in a chamber between two such mirrors, in addition to being coherent. Laser (US Air Force) A LASER (Light Amplification by Stimulated Emission of Radiation) is an optical device which uses a quantum mechanical effect called stimulated emission (discovered by Einstein while researching the photoelectric effect) in order to generate a coherent beam of light from a lasing medium of controlled purity... Coherent waves. ...

The light from stars can be considered collimated (for almost any purpose) because they are so far away. Due to it's relatively large appearance on the sky, the light from the sun deviates about half a degree to all directions when compared to a point source in the same position, giving approximately collimated light. The Pleiades star cluster A star is any massive gaseous body in outer space, just like the Sun. ... A sun is the star at the center of a planetary system. ...

A perfect parabolic mirror will bring parallel rays (from a star) to a focus at a single point. Spherical mirrors are easier to make than parabolic mirrors and they are often used to produce approximately collimated light. To produce usefully collimated light, the light source must approximate a point; that is, it must be small relative to the optical system, like the image of the star formed by a mirror. The necessary tradeoff is that, since the luminosity of most sources is small, such an optical system can not produce much optical energy. Lasers are a notable exception to this general rule. A parabolic reflector (also known as a parabolic dish or a parabolic mirror) is a reflective device formed in the shape of a paraboloid of revolution. ...