Phase Correction in Binoculars
April 6, 2010 | Posted by Best Binocular Reviews 
Phase correction in binoculars is a set of coatings on the prism glass inside the binocular that keeps light in correct color phases. These coatings are only needed on roof prism binoculars to enhance resolution, contrast, and color fidelity.
Phase Correction is needed because by their design, roof-prism binoculars split the light entering the barrels after passing through the objective lens into two separate paths. The light waves are then reflected off the surfaces of the roof prism and are split into two out-of-phase beams of light. Light reflected from one roof surface is 1/2 of a wavelength shifted from the light hitting the other roof surface. This is sometimes referred to as “out of phase” or “phase shift”. Although the light waves are subsequently merged back together when they reach the viewer’s eye, it results in reduced image resolution as well as reduced contrast.
To help increase the image quality and contrast, better quality binoculars have a thin coating on the roof prism surface which forces the light beams back into phase, thus creating a sharper view that is especially noticeable when viewing fine detail.
Phase shift does not occur in Porro prism designs.
Categories: Binocular Terms | 
Tags: Binocular Terms, Glossary, Phase Correction | 
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