Photonics Dictionary: O

A family of specialized instruments used by ophthalmologists and optometrists to study a patient's eyes and prescribe spectacles. It includes the ophthalmoscope to observe and photograph the retina;...

The transmission and reception of information by optical devices and sensors.

A system of modular mechanical components for building precision optical systems. The basic equipment includes a variety of modules for mounting, supporting and accurately positioning lenses and...

A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of the transmittance. where τλ is transmittance. In spectroscopy,...

The transmittance of a point on a photographic negative equal to the log to the base 10 of the reciprocal of the transmittance through the negative at that point.

The optical Fourier transform is a mathematical operation applied to optical signals that involves transforming a spatial domain representation of an image into its corresponding frequency domain...

A dome-shaped structure used for some optical instruments in place of a flat window. The transparent material should be of good quality and the hemispherical surfaces should be concentric.

Optical strain sensors are devices that utilize optical principles to measure the deformation or strain experienced by a material under mechanical stress. These sensors convert changes in strain into...

An optical testing instrument is a device or system used to evaluate and measure the performance, quality, and characteristics of optical components, systems, and devices. These instruments play a...

The function that characterizes the quality of an optical system by denoting the modulation and spatial phase shift of the image of a sinusoidal object with frequency as the independent variable.

A technique for detecting and measuring atmospheric pollution, in which an oscillating mirror directs half the incoming light to a transducer that controls amplitude and frequency, and the resulting...

The process by which an atomic system changes from one energy level to another by either the emission or absorption of visible, infrared or ultraviolet radiation.

A variable focal length lens system that retains the object in focus as one or more lenses move as a unit along its optical axis.

A transistor that uses an electro-luminescent source, a transparent base and a photoelectric collector.

Optical aberration refers to imperfections or deviations from ideal optical behavior in an imaging system, such as a lens or a mirror. These aberrations can cause distortions, blurring, or other...

Opsins are a group of light-sensitive proteins found primarily in the retinas of vertebrate and invertebrate eyes, as well as in other light-sensitive tissues. These proteins play a crucial role in...

The figure seen through or imaged by an optical system. It may contain structures, natural or artificial, or it may be the real or virtual image of an object formed by another optical system. In...

In holography, the wave of light that illuminates the object to be recorded, which diffracts it to the recording medium, where it interferes with the reference beam, generating the hologram.

The movement of an object seen through a refracting prism toward the apex of a prism.

The distance between the object and the cornea, or the first surface of the objective in an optical device.

In an optical system, the space between the object being viewed and the system entrance pupil.

Distance between the front vertex of a lens and the object.

The optical element that receives light from the object and forms the first or primary image in telescopes and microscopes. In cameras, the image produced by the objective is the final image. In...

A coarse diffraction grating that is used to form a scale of intensities to determine the relative magnitudes of stars. The grating is placed over the objective of a telescope to form a diffraction...

1. A prism used in some instruments to bend light 90° before it enters the objective. 2. A dispersing prism located in front of an astronomical telescope objective to produce spectra of all...

The image error that results from astigmatism, coma, oblique spherical aberration, lateral color and distortion.

A common technique in microscopy, oblique illumination is one in which the object is illuminated by a light source that is at an oblique angle (on the side) to the optical axis. This technique is...

A hemispherical covering that is rotatable about a central axis. There is a slit opening along one side wide enough to allow a telescope to be directed at any vertical angle up to 90°.

An acid-resistant, lustrous volcanic glass, usually black or banded.

A device that completely or partially restricts the amount of light reaching the eye.

Refers to the characteristic hue of the ocean according to the presence and concentration of specific minerals or substances, such as chlorophyll. Atmospheric aberrations of color must be corrected...

In optics, an octave typically refers to a range of frequencies or wavelengths that spans a factor of 2. In other words, when dealing with optics, an octave encompasses a doubling of frequency or...

Ocular accommodation is the process by which the eye changes its optical power to maintain a clear image (focus) on an object as its distance varies. This process is essential for seeing objects at...

The eye's involuntary reaction in the process of accommodation. This reflex is most dramatic in response to looking at a distant object after having previously been focused on a near object or vice...