Sections

Glossary

Glossary

aberration: failure of rays to converge at one focus because of limitations or defects in a lens or mirror

accommodation: the ability of the eye to adjust its focal length is known as accommodation

adaptive optics: optical technology in which computers adjust the lenses and mirrors in a device to correct for image distortions

angular magnification: a ratio related to the focal lengths of the objective and eyepiece and given as $M = - \frac{f_{o}}{f_{e}}$

astigmatism: the result of an inability of the cornea to properly focus an image onto the retina

color constancy: a part of the visual perception system that allows people to perceive color in a variety of conditions and to see some consistency in the color

compound microscope: a microscope constructed from two convex lenses, the first serving as the ocular lens—close to the eye—and the second serving as the objective lens

eyepiece: the lens or combination of lenses in an optical instrument nearest to the eye of the observer

far point: the object point imaged by the eye onto the retina in an unaccommodated eye

farsightedness: another term for hyperopia, the condition of an eye where incoming rays of light reach the retina before they converge into a focused image

hues: identity of a color as it relates specifically to the spectrum

hyperopia: the condition of an eye where incoming rays of light reach the retina before they converge into a focused image

laser vision correction: a medical procedure used to correct astigmatism and eyesight deficiencies such as myopia and hyperopia

myopia: a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina

near point: the point nearest the eye at which an object is accurately focused on the retina at full accommodation

nearsightedness: another term for myopia, a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than being focused on the retina

numerical aperture: a number or measure that expresses the ability of a lens to resolve fine detail in an object being observed. Derived by mathematical formula
9.28 $NA = n sin α,$

where $n$ is the refractive index of the medium between the lens and the specimen and $α = θ / 2$

objective lens: the lens nearest to the object being examined

presbyopia: a condition in which the lens of the eye becomes progressively unable to focus on objects close to the viewer

retinex: a theory proposed to explain color and brightness perception and constancies; is a combination of the words retina and cortex, which are the two areas responsible for the processing of visual information

retinex theory of color vision: the ability to perceive color in an ambient-colored environment

rods and cones: two types of photoreceptors in the human retina; rods are responsible for vision at low light levels, while cones are active at higher light levels

simplified theory of color vision: a theory that states that there are three primary colors, which correspond to the three types of cones