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The surface profile of a surface. For spherical surfaces, it is calculated from diameter and radius of curvature. For aspheric surfaces, it is calculated from radial distance from the optical axis, curvature, conic constant, and aspheric terms.
See also Radius of Curvature
A type of bevel in which the edge of an optical component is cut and conditioned to remove sharp corners. It is less toleranced than a ground edge.
See also Ground Edge
A type of microscope objective with a semi-planar design where roughly 80% of the objective's field of view appears flat.
The size of a camera sensor's active area, specified as the horizontal dimension by the vertical dimension (H x V). It is important in determing the proper lens magnification required to obtain a desired field of view.
See also Magnification
A type of filter where the transmission band is a low wavelength range, typically lower than the region blocked.
The effective resistance of a photodiode. It represents the slope of the I-V curve at the origin (V=0).
See also Photodiode
Corresponds to the "exposure time" of the sensor chip that controls the amount of light incident on it.
The standardization of transmission and reception of television signals for a given geographic area. Standard industrial cameras and consumer video equipment, therefore, are designed to reproduce what is considered "live" video using a particular television signal format. Signal parameters include synchronization, number of scanlines, bandwidth, black and blanking levels, frame rate, aspect ratio, etc. For instance, EIA or RS-170 (monochrome) and NTSC (color) use 525 scanlines with a field rate of 60 Hz; CCIR (monochrome) and PAL (color) signals use 625 lines at 50 Hz. Video components of one signal format are not compatible with those of another.
Comparison of signal power to noise power, including dark current and other unwanted/unpredictable fluctuations. In imaging systems, it is expressed in decibel values for analog systems, and "bit" values for digital systems. Industrial cameras have no less than 46dB SNR, yielding 256 steps of contrast in the image. This corresponds to an 8 bit digital signal (28 = 256). Every 6dB of an analog signal converts to 1 bit when digitized.
See also Noise Equivalent Power (NEP)
An electro-optic component that transforms light energy into an electrical current due to the photovoltaic effect.
See also Spectral Response
A lens with only one optical component such as a PCX, DCX, PCV, or DCV lens.
In terms of mechanical components, it is a mounting thread denoted by M12 x 0.5mm. S-mount components have a 12mm diameter screw thread and a 0.5mm thread pitch; the outer diameter is 16mm.
A laser using a transparent substance (crystalline or glass) as the active medium, doped to provide the energy states necessary for lasing. The pumping mechanism is the radiation from a powerful light source, such as a flash lamp.
An assembly that is used in conjunction with laser applications to eliminate spatial noise. A pinhole is used to select only the central peak of the intensity pattern from a focused spot. The size of the pinhole is selected based upon the wavelength, objective focal length, and input beam diameter.
The configurations of energy storage, relative to the structure of a laser resonator, that define the relative intensity distribution of the laser beam.
Irradiance per unit wavelength interval at a given wavelength, expressed in watts per unit area per unit wavelength interval.
Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.
An optical instrument for forming the spectrum of a light source and recording it on a film. The dispersing medium may be a prism or a diffraction grating.
See also Ghost Image
An optical instrument used to measure and analyze the distribution of radiation in a particular wavelength region.
See also Ghost Image
A type of on-axis optical aberration in which light rays from the outer portion of a lens focus either in front of (undercorrected) or behind (overcorrected) the focus point of the rays from the center portion of the lens.
A manufacturing specification that tolerances the roundness or deviation from being a perfect sphere of a spherical surface such as a ball lens.
See also Ball Lens
The linear polarization state which is perpendicular to the plane of incidence. The plane of incidence is normal to the surface or interface upon which light is incident. If the light is incident upon the interface at an angle, the light will be oscillating in such a way as to appear to be “skipping” across the surface.
The degree to which a laser beam is aligned parallel to the axis of the housing.
A wavelength interval used to denote a spectral region of energy that is not transmitted by a filter.
See also Filter
For ball bearing stages, it denotes error in the horizontal plane (left and right movement in direction of travel).
A measure of linear deviation in a translation stage in the two axes other than the direction of travel. It can be thought of as unintended linear travel in the two axes other than the direction of travel.
Energy outside of the clear aperture of an optical system that scatters off of the edges of an optical or mechanical component and reaches the sensor in the form of noise (not signal). This can decrease an image's contrast or a detector's signal to noise ratio.
The ratio of the illuminance at the peak of an aberrated diffraction pattern to that at the peak of an aberration-free system.
A proportionality constant used to calculate stress birefringence that depends on glass type, wavelength and temperature.
An indication of the peak-to-valley flatness of a surface given in terms of waves (a multiple or part of a reference wavelength). For example, a specification of 1/4 wave means that the flatness of the surface deviates by one quarter of the wavelength used to test the surface. If the wavelength was 550nm, the flatness would be held to within 0.14mm in order to produce a surface accuracy of 1/4 wave. Also given in RMS (root mean squared) where the peak-to-valley values are squared and then the square root is taken of their mean.
See also Reference Wavelength
A type of surface accuracy specification that measures the deviation of a flat surface such as that of a mirror, window, prism, or plano-lens. This deviation can be measured using an optical flat. The deviations in flatness are often measured in values of waves (&lambda), which are multiples of the wavelength of the testing source. One fringe corresponds to 1/2 of a wave. 1λ flatness is considered typical grade, 1/4λ flatness is considered to be precision grade, and 1/20λ is considered high precision grade.
See also Optical Flat
A specification of allowable flaws in the surface on an optic indicated by a hyphenated number (i.e. 60-40). The first number is referred to as the scratch number and quantifies defects of a long nature, such as scratches; the second number is the dig number and indicates round defects such as pits and dents. Scratch-Dig numbers for surface quality conform to the US government standards MIL-O13830.
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