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Unit of luminous intensity. 1 candela is equal to 1 lumen per solid angle.
A property that measures the ability of a conductor to hold electrical charge, measured in farads (F). Junction capacitance is related to the rise time of the photodiode. The smaller the capacitance, the shorter the rise time, and vice versa.
Video display based on vacuum tube with electron gun and annular anodes at one end and a cathode and phosphor screen at the other. Charged plates or electromagnets deflect the electron beam such that the image is scanned line by line across the face of the tube. Signal response is nonlinear with input, gamma usually between 2 and 3.
See also Oscilloscope
With interference filters, a spacer layer between two stacks of dielectric layers. The number of cavities determines the overall shape of the transmittance curve. Typically, interference filters use three cavities, resulting in steep slopes, improved blocking near the bandwidth, and relatively flat tops.
See also Bandwidth, Blocking, Filter, Interference Filter
A highly transmissive anti-reflection (AR) coating with transmission of 96 - 99% between 400 - 700nm.
A laser class standard administered by the Center for Devices and Radiological Health, a division of the US FDA (Food and Drug Administration). It is an alternative to the IEC laser class standard used throughout Europe.
See also IEC Laser Class
A European proof of conformity that allows manufacturers and exporters to circulate products freely within the European Union. The letters "CE", French for "Conformite Europeenne," indicate that the manufacturer has satisfied all assessment procedures specified by law for its product. Products requiring the CE Mark in Europe include, but are not limited to: high voltage devices, toys, construction products, equipment that generates electromagnetic interference, personal protection Equipment, and Medical Devices.
See also IEC Laser Class
An optical measurement specified as the distance from a primary principal plane location to the end of an element. A PCX or PCV lens has a single principle plane, yielding a single CT; a DCX or DCV has two principle planes, yielding two CT values.
See also Principal Plane
Also known by centration or decenter, it is specified in terms of beam deviation. The amount of decenter is the physical displacement of the mechanical axis from the optical axis.
Typically used to denote the peak transmitting wavelength of a filter, it is the midpoint determined by the passband wavelengths where the transmittance is 50% of the peak (denoted by the Full-Width at Half Maximum).
See also Bandwidth, Filter, Full Width at Half Maximum (FWHM)
Two-dimensional self-scanning electronic analog imaging device. The rectangular imaging area consists of rows and columns of rectangular photosensitive pixels that accumulate and store electric charge. Each column is separated by a shift register, or masked charge storage area, to which pixel charge is transferred. Charge is read out of the device sequentially from the shift register (masked) as the photosensitive pixels (unmasked) collect charge for the next field. Pixel charge is then transferred to the shift register, and the cycle continues.
See also Pixel, Complementary Metal Oxide Semiconductor (CMOS), Pixel Clock, Pixel Depth
In optical systems, the ray that begins at the edge of the object and goes through the center of the entrance pupil, exit pupil, and the stop (it has a height of 0 at those locations). The chief ray, therefore, defines the size of the object, size of the image and the locations of the pupils.
See also Marginal Ray, Paraxial Rays
A measure of axial chromatic aberration which causes light of different wavelengths to have different focal lengths. There are three kinds of chromatic aberrations: axial, transverse axial and lateral.
See also Longitudinal Chromatic Aberration (LCA), Aberration, Transverse Chromatic Aberration (TCA), Dispersion, Pellicle Beamsplitter
A polarizing component that uses a linear polarizer in combination with a retarder (waveplate). The retarder is used to introduce a wave shift between the orthogonal components of the polarized light. In this way, two equal components of light oscillating perpendicular to each other with a relative phase difference add as vectors to yield a rotating linear polarization state. If the amplitude components of the orthogonal states are not equal, the vector addition of the two components will produce an elliptical polarization. For this reason, the linearly polarized light is input into the retarder at 45° to the fast axis to ensure that both components are of equal amplitude.
See also Linear Polarizer, Retarder (Waveplate), Polarization
A low refractive index material that surrounds the core of an optical fiber. The difference in index between the core and the cladding contains light traveling through the core, while also serving to protect the fiber against surface contaminant scattering.
See also Index of Refraction (n), Optical Fiber, Buffer Material, Bend Radius
The usable portion of an optic or mechanical component. In optical components, it refers to the area in which the specifications are valid; whereas, in mechanical components, it limits the height of the ray bundles that can enter.
In terms of mechanical components, it is a mounting thread denoted by 1" x 32 TPI. C-mount components have a 30mm outer diameter. In terms of imaging, it is a camera and lens standard with a 17.526mm flange distance.
See also Back Flange Distance, T-Mount, CS-Mount, S-Mount, F-Mount
A measure of the rate of change of the material's size due to a change in temperature.
With respect to lasers, the amplifying laser medium produces coherent light because the process of stimulated emission produces additional photons with the same phase as the originator. Noise within the laser output is the result of spontaneous emissions which do not have the same characteristics as the stimulated emission. During oscillation, the spontaneous emission component will also be amplified and appear in the output as random noise.
See also Laser
A type of filter, though it has "mirror" in its name because it reflects light similar to a mirror, that contains a dielectric coating designed to reflect the visible region of the spectrum and transmit the infrared. Ideal for applications where heat needs to be removed from the reflected beam.
See also Hot Mirror, Dielectric Coating, Filter
Light in which every ray is parallel to every other ray of light. Note that light is never totally collimated due to aberrations present in collimators and due to the finite size of light sources.
See also Collimation, Autocollimator, Off-Set Angle
Converting a diverging or converging beam of light into a parallel beam of light.
See also Collimated Light, Autocollimator
A camera sensor that starts with the same sensor chip as a monochrome camera, but uses a mosaic filter to separate incoming light into a series of colors. Each color is then directed to a different set of pixels. In the filtering process some spatial resolution is lost because the sensor essentially is not using every pixel for every color.
See also Monochrome Sensor
Colorimetric parameter associated with light sources (compared with blackbodies) that relates to apparent visual color. Expressed in degrees Kelvin.
A method used to measure color and to define the results of the measurement. It includes many factors such as an object's physical characteristics, the surrounding colors, the light source, and the sensor or viewer.
An off-axis optical aberration that yields a variation in magnification (and therefore image size) with aperture. In other words, when a lens containing coma images an off-axis light bundle, each zone of the lens is focused on the image plane at a different height and with a different spot size.
See also Aberration
A type of sensor in which the charge-to-voltage conversion is done at the pixel level and yields a less uniform output and very low power dissipation. CMOS sensors should be used in applications requiring low power consumption or in space-constrained applications.
See also Pixel, Charge-Coupled Device (CCD), Binning
An optical component which is designed to collect and concentrate distant light sources efficiently. CPCs are used in solar energy collection, wireless communication, biomedical and defense research among other applications requiring condensing a divergent light source.
Polishing technique for aspheric lenses which automatically adjusts the tool dwell parameters to polish away high spots where more polishing is needed.
For rotary stages, the maximum variance between a perfect circle and the path that the stage follows.
A positive lens or set of lenses designed to collect light and project it evenly across an area. Commonly found in projector systems as part of the condenser lens portion.
The distance along the optical axis of a lens from the principle plane of that lens to either the image plane (for an image conjugate) or the object plane (for an object conjugate). Lenses designed to focus at infinity have an infinite conjugate distance for the object and a finite conjugate distance for the image.
See also Principal Plane, Infinite/Infinite Conjugate, Finite/Finite Conjugate, Infinite/Finite Conjugate
A type of neutral density filter with a gradient of optical densities which vary radially from the center. There are two configurations: high optical density in the center that decreases continuously to an uncoated edge, and high optical density on the edge that continuously decreases to an uncoated center.
See also Optical Density (OD), Neutral Density Filter
Comparison of shades of gray that define an object and its background.
See also Resolution, Depth of Field (DOF), Modulation Transfer Function (MTF)
A cylindrically enlarged end of a hole. Typically used to accept the head of a socket head cap screw, making the screw head accessible but not obstructive.
Loss of optical energy between two optical conductors.
See also Optical Fiber
One of two types of optical glass used in the manufacturing of achromatic lenses. Crown glass is harder than flint glass and has a lower index of refraction and lower dispersion.
See also Flint Glass, Achromatic Lens
Similar to a C-mount, it is a mounting thread denoted by 1" x 32 TPI. In terms of imaging, it is a camera and lens standard with a 6.526mm flange distance. A 5mm C-mount extension tube/ spacer can be added to turn it into a C-mount. C-mount lenses can be used with CS-mount cameras with the addition of this 5mm; however, due to the flange distance, CS-mount lenses cannot work with C-mount cameras.
See also Back Flange Distance, T-Mount, C-Mount, S-Mount, F-Mount
A type of beamsplitter constructed of two cemented right angle prisms, one with a broadband multi-layer dielectric coating on the hypotenuse. 50% of incident light is transmitted, and 50% is reflected. Outside surfaces have an anti-reflection coating to reduce back reflections. No beam displacement occurs between the original and separated beams. The reflected and transmitted beams travel through the same amount of glass, so although the optical path length of each arm is increased, both paths are increased by the same amount. Their cubic shape makes cube beamsplitters easy to mount, thus suffering less from deformation due to mechanical stress.
See also Plate Beamsplitter, Dielectric Coating, Anti-Reflection (AR) Coating, Beamsplitter
In filter terminology, the wavelength at which the transmission decreases to 50% throughput in a shortpass filter. In fiber optics, the shortest wavelength at which a fiber transmits in single mode. Below the cut off several modes will propagate and the fiber is no longer single-, but multimode. In detector technology, the wavelength at which the detector response falls to a set percentage (usually 20 or 50 percent).
See also Cut-On Wavelength, Filter
In filter terminology, the wavelength at which the transmission increases to 50% throughput in a longpass filter.
See also Cut-Off Wavelength, Filter
A type of lens that focuses light in only one dimension. Its profile is similar to a PCX lens (though PCV profiles also exist) and it can transform a point of light into a line image.
Optics Application Examples – Read our most popular Optics app note. Learn about detector systems, selecting the right lens, and building a projection system.
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