Annular illumination (/ˈænjʊlər ɪˌluːmɪˈneɪʃən/) refers to a type of illumination that creates a ring-shaped image. The spelling of "annular" comes from the Latin word "annulus," meaning "ring." The word is pronounced with stress on the second syllable and features the short "a" sound followed by a "yoo" sound. The spelling of "illumination" comes from the Latin root "illuminare," meaning "to light up." It is pronounced with stress on the second syllable and features a schwa sound in the third syllable.
Annular illumination refers to a type of lighting technique where a circular beam of light is formed, usually having a central void or hole. This technique ensures that the illuminated area in the center is darker or less bright than the surrounding area, creating an annular appearance. It is commonly used in various applications, including photography, microscopy, and optical systems.
In photography, annular illumination is a method utilized to achieve a specific lighting effect on the subject or object being captured. By directing a circular light source towards the subject, with the center often left unlit or only partially illuminated, it creates a distinctive halo or ring-shaped glow. This technique can add depth and enhance the contrast of the photographed subject, making it stand out from the background.
In microscopy, annular illumination is employed to control the light distribution entering the microscope. By using a specialized annular stop, light is limited to a ring-shaped area, providing uniform illumination across the field of view. This technique helps to reduce glare, increase contrast, and improve the visibility of certain features under microscopic examination.
In optical systems, particularly in illumination apparatus, annular illumination is frequently used to achieve even distribution of light on the target area. The annular shape ensures that the light rays are dispersed evenly, eliminating any potential bright spots or shadows. This type of illumination can be found in various applications, from surgical lighting to industrial inspection systems.
Overall, annular illumination serves to create specific lighting effects, enhance visibility, and improve the overall performance of various optical and imaging systems.
The word "annular" originates from the Latin word "annulus", which means "ring". It entered the English language in the mid-17th century and was primarily used in the field of geometry to describe a shape that is ring-shaped or circular. The term "illumination" has its roots in the Latin word "illuminare", which means "to light up". It entered English in the late 14th century and refers to the act of lighting or the state of being illuminated. The combination of "annular" and "illumination" in the phrase "annular illumination" suggests the lighting or illumination in the form of a ring or circular shape.