May 15 2014
A collimator is a device used for changing the direction of a light diverging from a point source into a parallel beam. The collimation of light is necessary to make spectroscopic measurements.
A typical optical collimator consists of a tube with a convex lens at one end and an adjustable aperture at the other. The aperture is set at the focal plane of the lens. The radiation striking the aperture exits the collimator as a parallel beam, such that the image can be viewed without parallax.
Basic Principle
A typical collimator consists of an objective lens with an illuminated reticle at its focal plane. The emerging beam is collimated so that the image of the reticle is projected at infinity. The collimator is usually set at infinity adjustment.
The shape of the emerging light beam will tend to change while moving the reticle out of the focal plane of the objective lens. The movement of the reticle away from the objective lens will result in a convergent beam. In this case, the image of the reticle is real, and projected at a finite distance.
On the other hand, moving of the reticle towards the objective lens will result in a divergent beam, producing virtual images. At this point, the adjustment of the collimator is set at a finite distance.
Applications
The key applications of a collimator include:
- Radiology
- CO2 cutting lasers and laser diodes
- Pigtailed receptacles
Sources and Further Reading