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Glossary Of Terms

On this page, you can look up terms associated with precision surfaces, optics, and precision measurement. More detailed definitions of many terms associated with surface texture metrology can be found in ZYGO's Surface Texture Parameters PDF document.

Click on a letter to go directly to that point in the glossary:

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z 

A/W Space
The amplitude/ wavelength response of a surface measuring instrument as defined by the M. Stedman Amplitude/ Wavelength Graphs.

The amount by which a measured value adheres to a standard.

Equal to 0.0000000001 meters, or 0.1 nanometers.

An optical device for dividing a beam into two or more separate beams.

1) A housing containing magnetic tape wound between two spools and which has a write-protect switch. 2) An ink bladder for the Paintjet Printer.

Coherence Length
The distance over which interference will occur. Coherence length of an optical source is affected by the size of the source, spatial coherence, the phase purity of the source, temporal coherence, and the spectral bandwidth of the light.

Coherent Light Source
A light source that is capable of producing radiation with all the waves vibrating in phase.

Denotes a spherically shaped surface, curved inward.

Denotes a spherically shaped surface, curved outward.

Coordinate System
A method of locating points or positions by assigning numbers to them. A three dimensional coordinate system has 3 axes and is used to locate a point or object in space.

Fizeau interferometer
An interferometer that incorporates a reference and test light path of unequal distance.

The general shape of a surface or low frequency surface characteristics.

The light and dark band caused by interference. In a Fizeau double-pass setup with the interferometer operating at 633 nm, each cycle from light to dark to light is equal to 316 nm.

The Hewlett-Packard Interface Bus. A cable with standard connectors for transfer of data between the computer and peripherals. Also known as IEEE-488.

An extension of AT&T's UNIX System V developed by Hewlett-Packard for its super-minicomputers and workstations.

Denotes the lack of a fixed phase relation between two waves.

Index of refraction
The ratio of the speed of light in vacuum to the speed of light in a refractive material for a given wavelength.

The constructive and destructive superposition of two wavefronts that have different phases. In an interferometer the two wavefronts are produced by the reference surface and the test sample surface.

An instrument that employs the interference of light waves to measure the wavefront.

Interferometric Objective
An optical component attached to a microscope that gathers light from the object, forms a real image of it, and creates an interference pattern.

An acronym of "Light Amplification by Stimulated Emission of Radiation." A laser is a cavity, with mirrors at the ends, that is filled with a gas or gas mixture, such as Helium and Neon.

Lateral Resolution
The smallest linear separable and measurable feature on the imaged surface. Lateral resolution of an interferometric microscope objective is a function of the numerical aperture. and the Spatial Sampling Interval. See Vertical Resolution, Rayleigh, and Sparrow.

The direction of predominant surface features.

The amount of lateral enlarging produced by an interferometric microscope objective.

Abbreviation for megabyte; a unit of data approximately equal to one million bytes (1,048,576 bytes).

The area of a computer where programs and data are stored.

The prefix meaning one-millionth.

Equal to 0.0254 micrometer.

Micrometer (or Micron)
Equal 0.000001 meters (formerly micron), or 39.3701 microinches.

Fine irregularities of a surface.

Equal to 0.001 meters, or 39.3701 mils.

Millimicron - See nanometer.

Mirau interferometer
An interferometer where interference occurs only when the reference and test light paths are equal.

Motion Controller
A control device for ZYGO microscopes comprised of a joystick and a motor drive. It is used to drive the microscope head up and down and operate motorized translation stage accessories.

The small mechanical device whose movement corresponds to pointer movements on a monitor.

Nanometer (nm)
Equal to 0.000000001 meters (formerly millimicron), or 0.03937 microinch.

Any random or periodic non-data signal in the measurement.

Nominal Surface
The intended surface contour, exclusive of any intended surface roughness. numeric aperture.

The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an objective, multiplied by the refractive index of the medium in which the vertex is located. In air the N.A. must be less than 1.

Phase Discontinuity
A phase discontinuity occurs when the software algorithm for connecting the adjacent pixel phases in a continuous manner cannot determine the direction and height of a step. This is typically caused by steep surface slopes. This slope limitation in the microscope is objective dependent.

Shortened form of "picture element." The smallest element of the CID detector used for imaging and data acquisition.

The number of detector pixels in a particular data set. The number varies due to the use of the masks and zoom features which can alter the definable measurement area.

The contour of the surface in a plane perpendicular to the surface. It is a two-dimensional plot of the data.

Abbreviation for piezoelectric transducer. This component modulates the phase of the interference pattern across the detector by moving the objective and hence the reference surface.

A unit of angular measurement equal to the angle at the center of a circle subtended by an arc equal in length to the radius. There are 2 pi radians in a circle.

Abbreviation for Random Access Memory. It is erasable program memory; programs and data are usually copied into RAM from a disk drive. Data in RAM is lost when power is removed.

Rayleigh Resolution
Describes the resolving power of an objective as 1.22l/N.A.

Refractive Index - See index of refraction.

The precision with which repeat measurements of the same sample give the same value with all conditions unchanged between measurements, except time.

The smallest quantity that can be measured.

The finer irregularities of the surface texture; usually including irregularities resulting from the production process.

An acronym for Small Computer System Interface, an industry standard interface that provides high-speed access to peripheral devices.

Sparrow Resolution
Describes the resolving power of an objective as l/N.A.

Spatial Sampling Interval
The apparent size of a camera pixel (see points) that is projected on the test sample. Spatial Sampling Interval is a function of the interferometric microscope magnification.

1) an object that reflects light. 2) In the direction in which a mirror reflects incident light.

Surface Texture
The repetitive or random deviation from the nominal surface that forms the three dimensional surface topography. Includes lay, waviness, roughness, and flaws. Any manufactured surface has irregularities due partly to the nature of the material but to a greater extent to the finishing operation used.

A rotating plate on the microscope that contains up to five objectives to provide for a rapid change of magnification.

An interactive, multi-tasking, and multi-user computer operating system that controls the communications, data storage, and information process capabilities of the computer hardware. It is comprised of three main parts: kernel, shell, and file system.

Vertical Resolution
The smallest measurable increment normal to the plane of measurement. A function of the resolution of measurement of interferometric phase.

A surface connecting all field points (of electromagnetic energy) that are equidistant from the source.

The component of surface texture upon which roughness is superimposed. See form.

X, Y, Z axes - See below.

Horizontal or left and right direction. Can refer to left-to-right movement of a translation stage or to the left-to-right direction on the video monitor. Orthogonal to Y and Z.

Horizontal or back and forward direction, but 90 degrees to X. Can refer to the front-to-back movement of a translation stage or to the up-and-down direction on the video monitor. Orthogonal to X and Z.

Vertical direction of the microscope relative to the fixture stage. Refers to the up-and-down movement of the microscope head. Parallel to the optical axis and normal to the X-Y plane.

(1) Greek root word meaning "bridge" or "link."
(2) A precision measuring instrument that helps improve manufacturing quality and productivity.
(3) The company that designs and manufactures the precision instruments cited in definition (2).

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