Glossary of Image Analysis and Machine Vision Terms

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A

Aberration — The failure of an optical lens to produce an exact point-to-point correspondence between the object and its resulting image. Various types are chromatic, spherical, coma, astigmatism and distortion.

Absorption — The loss of light of certain wavelengths as it passes through a material and is converted to heat or other forms of energy.

AC Coupled — A method of connecting a video signal to any circuit in a way that removes the potentially harmful DC offset. The DC offset is the overall voltage level that the video signal "rides" on.

Accuracy — The extent to which a machine vision system can correctly measure or obtain a true value of a feature. The closeness of the average value of the measurements to the actual dimension.

Acquisition — The manner in which outside information is brought into an analysis system.

Active Illumination — Lighting a scene with a light source coordinated with the acquisition of an image. Strobed flash tubes, pulsed lasers and scanned LIDAR beams are examples.

Active Video — The part of the video waveform that is actually visible on the screen.

ActiveX® Control — Formerly known as OLE controls. A special form of component Automation Object that can be freely plugged into any OLE-enabled development tool, application or web browser.

A/D — See Analog-to-Digital Converter.

Algorithm — A set of well-defined rules or procedures for solving a problem or providing an output from a specific set of inputs.

Alpha Channel — A means by which two images can be blended, switched or combined in some way. Alpha numbers are stored in a separate plane of memory that sits alongside the frame buffer, one alpha number per pixel. The number stored determines what percentage of the first image is to be combined with what percentage of the second image.

Alpha Ray (ý-risk) — The risk of rejecting good product.

Ambient Light — Light which is present in the environment of the imaging front end of a system and generated from outside sources. This light, unless used for actual scene illumination, will be treated as background noise by the imaging system.

Analog —A smooth, continuous voltage or current signal or function whose magnitude (value) is the information. From the word "analogous," meaning "similar to."

Analog-to-Digital Converter (A/D) — A device which converts an analog voltage or current signal to a discrete series of digitally encoded numbers (signal) for computer processing.

Aperture Delay — The time from the falling edge of the input clock of the A/D until the time the image is taken.

Aperture Jitter — Uncertainty in the aperture delay.

API — Application Programming Interface.

Application Specific Machine Vision (ASMV) — A turnkey system that addresses a single specific application that one can find widely throughout industry or within a specific industry.

Architecture — For a vision system, the hardware organization designed for high speed image analysis.

Area — Portion or area of the image to be analyzed. Area analysis measures the number of pixels which fall in a specified range of gray levels for the feature of interest.

Area Array Camera — A solid state imaging device with both rows and columns of pixels, forming an array which produces a 2D image.

Array Processor — A specially designed vision engine peripheral which attaches to the host to speed up arithmetical calculations by using parallel processing techniques. The host manages image data access and analysis results.

Artifact — [1] Blemishes, noise, snow, spots, or other physical distortions in an image. [2] An artificially created structure (by accident or on purpose), form or shape, usually part of the background, used to assist in measurement or object location.

Artificial Intelligence — The capability of a computer to perform functions normally attributed to human intelligence, such as learning, adapting, recognizing, classifying, reasoning, self correction and improvement. Rarely found connected to vision systems.

ASIC — An acronym for Application Specific Integrated Circuit. All vision system elements including firmware can be integrated onto one ASIC.

Aspect Ratio — The ratio of the width to the height of a frame of a video image. The U.S. analog television standard is 4:3 or 1.333.

Astigmatism — A defect in a lens which causes blur or imperfect image results, since the rays from a given point fail to meet at the focal point.

Asynchronous — A camera characteristic which allows the return to top-of-frame to occur on demand, rather than synchronously following the 60 Hz power line scanning frequency.

Attribute List — List of distinguishing features which are selected for image processing calculation.

Auto Focus — The ability of an imaging system to control the focus of the lens to obtain the sharpest image on the detector. Edge crispness is a typical control variable.

B

Background — The part of a scene behind the object to be imaged.

Backlighting — Placement of a light source behind an object so that a silhouette of that object is formed. It is used where outline information of the object and its features is important rather than surface features.

Back Porch — The area of the video waveform staked out by the rising edge of the horizontal sync pulse and right before the active video or before the terminating edge of the horizontal blanking.

Back Propagation — A training technique which adjusts the weights of the hidden and input layers of a neural net to force the correct decision for a given feature vector data input set.

Baffle — A type of shield that prohibits light from entering an optical system.

Bandpass Filter — An absorbing filter which allows a known range of wavelengths to pass, blocking those of lower or higher frequency.

Bar Code — An identification system that employs a series of machine-readable lines of varying widths of black and white. Usually read with a laser scanner.

Bar Code (2D) — A matrix of rectangles and spaces that contains far more information than a traditional bar code.

Barrel Distortion — An optical imperfection which causes an image to bulge convexly on all sides similar to a barrel.

Beamsplitter — An optical device which divides one beam into two or more separate beams. A simple coated piece of glass in the optical path might reflect 60% of the light down onto the object, while allowing the other 40% to pass.

Beta Risk — The risk of accepting bad or defective software.

Binary — An image with pixel values either one or zero.

Binary Image — A black and white image represented as a single bit containing either zeros or ones, in which objects appear as silhouettes. The result of backlighting or thresholding.

Bit — An acronym for a BInary digiT. It is the smallest unit of information which can be represented. A bit may be in one of two states, on or off, represented by a zero or a one.

Bit Map — A representation of graphics or characters by individual pixels arranged in rows and columns. Black and white require one bit, while fancy high definition color up to 32.

Black Burst — The video waveform without the active video part.

Black Level — This level represents the darkest an image can get. Defines what black is for a particular image system.

Blanking — The time during a raster scan retrace when the video signal is suppressed.

Blanking Level — That level of the video waveform defined by the system to be where blanking occurs. This could be the black level if a pedestal is used or below the black level if a pedestal is not used.

Blob — A single, connected region in a binary or grayscale image.

Blob Analysis — Identification of segmented objects in an image based on their geometric features (i.e. area, length, number of holes).

Blooming — An effect, sometimes caused when video becomes whiter-than-white, in which a thin line becomes larger and fuzzy on the screen.

Borescope — A device for internal inspection of difficult access locations such as pipes, engines, rifle barrels and pipes. Its long narrow tube contains a telescope system with a number of relay lenses. Light is provided via the optical path or fiber bundles. A 45 degree mirror at the end allows inspection of tube walls.

Boundary — The line formed by the joining of two image regions, each having a different light intensity. The edge of a region or object.

Bounding Box — The four coordinates which define a box around the object parallel to the major and minor axis.

Breezeway — That portion of the video waveform that sits between the rising edge of the horizontal sync and before the start of burst.

Brewster's Angle — The angle at which incident light, by reflecting at a boundary between two mediums of different refractive indices (i.e. air/glass or air/water), becomes plane polarized. For air/glass it is about 67.4 degrees.

Brightness — The total amount of light or incident illumination on a scene or object per unit area. Also called intensity.

Burst — See Chroma Burst.

Burst Gate — A signal that tells the system where the burst is located within the scan line.

Bus — Conductors used to interconnect individual circuitry within a computer. The conductors as a whole are called a bus.

Byte — Eight bits of digital information. A byte has values from 0 to 255, and is the unit most common to represent the gray scale value of one pixel.

C

C-mount — A threaded means of mounting a lens to a camera.

Calibration — The act of relating X and Y pixel spacing to known or predetermined pixels per unit length (i.e. inch, mm) factor. Often involves adjusting the image position in setup.

CCD (Charge Coupled Device) — A photo-sensitive image sensor implemented with large scale integration technology.

Centroid — The center of mass of an object having a constant density, or of an object having varying density, weighted by the gray scale value.

Character — A single letter, digit or punctuation symbol requiring one byte storage.

Chroma — See Chrominance.

Chroma Bandpass — In an NTSC or PAL video source the luma (black and white) and the chroma (color) information are combined together. In order to display an NTSC or PAL source, the luma and chroma must be split apart. The chroma bandpass filter removes the luma information from the chroma information, leaving the chroma information relatively intact.

Chroma Burst — The portion of the video waveform that helps the received determine what the colors are.

Chroma Demodulator — After the NTSC or PAL video source makes its way through the Y/C split, by either the chroma bandpass/trap method or the comb filter method, the color is decoded by the chroma demodulator.

Chroma Key — A method of combining two video images.

Chroma Trap — Similar to chroma bandpass, a method for separating the chroma information from the luma information, leaving the luma relatively intact.

Chromatic Dispersion — See Dispersion.

Chrominance — The color part of a video signal, relating to the hue and saturation but not the brightness or luminance of the signal. Also called Chroma.

Chrominance Filter — An electronic circuit, usually in the form of a notch filter, used to remove chrominance color information from a video signal.

CID (Charge Injection Device) - A photo-sensitive image sensor implemented with large scale integration technology. Based on charge injection technology, a CID can be randomly addressed, non-destructively read, can be subscanned in a small region and is less susceptible to charge overflow from bright pixels to neighbors. The pixel structure is contiguous with maximum surface to capture incident light which is useful for sub-pixel measurement.

CIE — An acronym for a chromaticity coordinate system developed by the Commission Internationale de l'Eclairage, the international commission on illumination. In the CIE system, a plot of ratios (x, y and z) of the three standard primary colors (tristimulus values) to their sum. The most common diagram is the 2 dimensional CIE (x,y).

CIF (Common Interchange Format) — Developed to share images between computers.

Clamp — Restoring a DC component that was removed to make an AC coupled signal. Also called DC-Restoration.

Classification — Assignment of image objects to one of two or more possible groups. Decisions are made by evaluating features either 1) structurally based on relationships or 2) statistically. For example, 1) a penny is round, a certain diameter (+/- a tolerance) and has a histogram of a mean value; or 2) statistically, the object is measured a number of times, then the average and standard deviation are recorded. After training the features are weighted based on significance in object identification. For multiple features, absolute values are used.

Clipping Logic — A circuit used to prevent illegal conversion. After the conversion from one color space to another, a color space converter checks for illegal colors, and clipping logic is used to remove information until a legal color is represented.

Closing — A dilation followed by an erosion. A morphological operator useful to close holes and boundaries.

CMYK — A color space typically used for printing (Cyan, Magenta, Yellow, Black).

Coaxial Illumination — Front lighting with the illumination path running along the imaging optical axis and usually introduced with a 45 degree angle beam splitter.

Coherent Fiber Optics — A bundle of optical fibers with the input and output spatial x-y relationship maintained, resulting in near spatially correct image transmission.

Collimate — To produce light with parallel rays.

Collimated Lighting — Radiation from a given point with every light ray considered parallel. In actuality, even light from a very distant point source (i.e. a star) diverges somewhat. Note that all collimators have some aberrations.

Color — A visual object attribute which may be described by a "coordinate system" such as hue, saturation and intensity (HSI), CIE or LAB. Wavelengths in the visible part of the electromagnetic spectrum to which retinal rods respond.

Color Bar — A test pattern used to check whether a video system is calibrated correctly.

Color Burst — That portion of the video waveform that sits between the breezeway and the start of active video. It tells the color decoder in the receiver how to decode the color information contained in the next line of active video.

Color Decoder — The circuit in the video system that uses the chrominance portion of NTSC/PAL to derive the two color difference signals.

Color Difference — All of the color spaces used in imaging require three components (except for CMYK).

Color Encoder — Takes two color difference signals and combines them into the chroma signal. The opposite of the color decoder.

Color Key — See Chroma Key.

Color Killer — A circuit that shuts off the color decoder in a video system if the incoming video does not contain color difference signals.

Color Purity — Describes how close a color is to the theoretical.

Color Space — A two or three dimensional space used to represent an absolute color coordinate. RGB, HSI, LAB and CIE are all representations of color spaces.

Color Subcarrier — A clock signal used to run the color encoder or color decoder in an NTSC or PAL video system.

Color Temperature — A colorimetric concept related to the apparent visual color of a source, but not its actual temperature.

Colorimetry — Techniques used to measure color of an object or region and to define the results in a comparison or coordinate system.

Comb Filter — Used in place of a chroma bandpass and chroma trap combination — provides better video quality because it is more successful at separating the luma from the chroma.

Composite Sync — A signal consisting of horizontal sync pulses, vertical sync pulses, and equalizing pulses only, with a no-signal reference level.

Composite Video — A video stream which is produced by combining both a video and picture signal with horizontal and vertical sync and blanking signals.

Compression Ratio — A number which tells how much information has been compressed in an image.

Condenser Lens — Used to collect and redirect light for the purpose of illumination. Often used to collect light from a small source and project even light onto an object.

Connectivity Analysis — An SRI routine used to determine which pixels are interconnected and part of the same object or region. The results are used for blob analysis.

Contouring — An image artifact caused by not having enough bits to represent the image.

Contrast — The difference of light intensity between two adjacent regions in the image of an object. Often expressed as the difference between the lightest and darkest portion of an image. Contrast between a flaw or feature and its background is the goal of illumination.

Contrast Enhancement — Stretching of the gray level values between dark and light portions of an image to improve both visibility and feature detection.

Convolution — Superimposing an m x n operator (usually a 3x3 or 5x5 mask) over an area of the image, multiplying the points together, summing the results to replace the original pixel with the new value. This operation is often performed on the entire image to enhance edges, features, remove noise and other filtering operations.

Correlation — A mathematical measure of the similarity between images or areas within an image. Pattern matching or correlation of an X by Y array size template to the same size image, produces a scaled number, the percentage of match. Typically, the template is walked through a larger array to find the highest match.

Creepy-Crawlies — A specific image artifact resulting from the NTSC system. Also called zipper.

Cropping — A method of selecting a desired portion or region of interest out of an entire image.

Cross Section — A 3D profile of a slice of an object.

D

DAC — See Digital-to-Analog Converter.

Darkfield Illumination — Lighting of objects, surfaces or particles at very shallow or low angles, so that light does not directly enter the optics. Objects are bright with a dark background. This grazing illumination causes specular reflections from abrupt surface irregularities.

Data Reduction — The process of lowering the data content of a pixel or image such as thresholding or run length encoding.

DC Restoration — Restoring a DC component that was removed to make an AC coupled signal. Also see Clamp.

Decimation — A method of image scaling which involves removing unused pixels.

Decimation Filter — A filter designed to provide decimation without the artifacts associated with removing data.

Decision Tree — A structural classification technique based on relationships of feature measurements. Useful for differentiating a number of objects.

Dedicated System — Refers to a system which is configured for a specific application. Able to function when plugged in with no further development. Also called turnkey.

Demodulation — The technique used to separate the color components in NTSC or PAL systems.

Depth-of-Field — The range of an imaging system in which objects are in focus.

Depth Perception (3D) — Measurement of the third dimension of an object or scene.

Dichroic Filter — A filter used to transmit light based on its wavelength, rather than on its plane of vibration. Transmits one color, while reflecting a second when illuminated with white light. Often used in heads-up displays.

Differential Gain — When the magnitude of the chroma changes with respect to the luma when it should not, resulting in incorrect saturation.

Differential Phase — A change in the phase of the color burst for a change in the brightness of the picture.

Diffraction Pattern Sampling — Inspection by comparing portions of the interference pattern formed on a screen or special sensor from light waves diffracted by object edges.

Diffuse Reflection — Light which bounces off an object surface in many different directions. Light radiated from a matte surface is highly diffused.

Diffused Lighting — Scattered soft lighting from a wide variety of angles used to eliminate shadows and specular glints from profiled, highly reflective surfaces.

Digital Camera — The newest generation of video cameras transforms visual information into pixels, and then translates each pixel's level of light into a number in the camera.

Digital Clock Sync — A precise digital circuit that can quickly and accurately lock onto incoming video timing pulses, resulting in significantly lower jitter.

Digital Image — A video image converted into pixels. The numeric value of each pixel's value can be stored in a computer memory for subsequent processing and analysis.

Digital Imaging — Conversion of a video picture into pixels by means of an A/D converter where the level of each pixel can be stored in a computer.

Digital-to-Analog Converter (DAC) — A VLSI circuit used to convert digital computer processed images to analog for display on a monitor.

Digital Signal Processor (DSP) — A VLSI chip designed for ultra high speed arithmetic processing. Often embedded in a vision engine.

Digitization — Sampling and conversion of an incoming video or other analog signal into a digital value for subsequent storage and processing.

Dilation — A morphological operation which moves a probe or structuring element of a particular shape over the image, pixel by pixel. When an object boundary is contacted by the probe, a pixel is preserved in the output image. The effect is to "grow" the objects.

Dispersion — Separation of a beam of light into its wavelength components, each of which travel at slightly different speeds. Also called Chromatic Dispersion.

Dithering — Changing a range of gray to patterns of black and white, or using two or more colors to create the appearance of a larger section.

Dust — An environmental contaminant consisting of airborne particles to be dealt with in machine vision. Never use factory air to keep optical surfaces clean, since oil will deposit.

Dynamic Range — The measure of the range light sensitivity a sensor is able to reproduce, from the darkest to the brightest portion of a scene. Usually expressed in decibels.

E

Edge — A change in pixel values exceeding some threshold amount. Edges represent borders between regions on an object or in a scene.

Edge Detection — The ability to determine the true edge of an object.

Edge Enhancement — Image processing method to strengthen high-spatial frequencies in the image.

Edge Operator — Templates for finding edges in images.

Electrical Noise — Interference from various electrical devices which is present in the air as electromagnetic radiation or rides on the power lines and can introduce error into low voltage computations such as A/D conversion.

Electro-magnetic Spectrum — The total range of wavelengths, extending from the longest (audio) to the shortest (gamma rays) which can be physically generated. This entire spectrum is potentially useful for imaging, well beyond just the visible spectrum.

Encoder (Shaft or Position) — Provides rotation information for control of image acquisition, especially for moving web processes. Outputs either pulses for counting or BCD parallel with absolute position information.

Endoscope — A medical instrument used to view inside the human body. It may use borescope optics or coherent fibers to relay the image to the eye or camera. Illumination is provided by a non-coherent bundle of optical fibers.

Erosion — The converse of the morphology dilation operator. A morphological operation which moves a probe or structuring element of a particular shape over the image, pixel by pixel. When the probe fits inside an object boundary, a pixel is preserved in the output image. The effect is to "shrink or erode" objects as they appear in the output image. Any shape smaller than the probe (i.e. noise) disappears.

Extension Tube — A cylindrical threaded tube used to change the magnification, effective focal length and field of view of a lens when inserted between the lens and imaging sensor.

F

F-number or f-stop — The ratio of the focal length to the lens aperture. The smaller the fnumber, the larger the lens diameter and brighter the image and narrower the depth-of-field.

Fade — A method of switching from one video source to another video source.

Fast Fourier Transform — Produces a new image which represents the frequency domain content of the spatial or time domain image information. Data is represented as a series of sinusoidal waves.

Feature Extraction — Determining image features by applying feature detectors to distinguish or segment them from the background.

Feature Vectors — A set of features of an object (such as area, number of holes, etc) that can be used for its identification or inspection.

Features — Simple image data attributes such as pixel amplitudes, edge point locations and textural descriptors, center of mass, number of holes in an object with distinctive characteristics defined by boundaries or regions.

Fiber Optics — Light source or optical image delivery via a long, flexible fiber(s) of transparent material, usually bundled together. Light is transmitted via internal reflection inside each fiber. Coherent fiber optics are spatially organized so images can be relayed.

Fiberscope — An optical instrument similar to a borescope, but uses a flexible, coherent fiber or bundle (usually silicon), an objective lens and an eyepiece or camera.

Fiducial — A line, mark or shape used as a standard of reference for measurement or location.

Field — The set of either the even or odd lines in a video image. The odd plus the even field comprise one video frame. A field is scanned every 1/60th of a second.

Field-of-View (FOV) — The 2D area which can be seen through the optical imaging system.

Filter — A device or process that selectively transmits frequencies. In optics, the material either reflects or absorbs certain wavelengths of light, while passing others. Filters can be used to sharpen or smooth image details, or to extract edges from objects.

Filtering — The use of an optical filter for picture or color enhancement in front of the camera lens or light source. Also analog or digital image processing operations to enhance or modify an image. May be linear or non-linear.

Firmware — Software hard coded in non-volatile memory (ROM), usually to increase speed.

Fixture — A device to hold and locate a workpiece during processing or inspection operations.

Flicker — Occurs when the frame rate of the video is too low and the human eye can perceive the individual frames.

Fluorescence — The emission of light or other electromagnetic radiation at longer wavelengths by matter as a result of absorption of a shorter wavelength. The emission lasts only as long as the stimulating irradiation is present.

Focal Length — The distance from a lens' principal point to the corresponding focal point on the object.

Focal Plane — Usually found at the image sensor, it is a plane perpendicular to the lens axis at the point of focus.

Focus — The point at which rays of light converge for any given point on the object in the image. Also called the focal point.

Focus Following — A ranging and tracking technique that uses image processing to measure object range based on best focus.

Fourier Domain Inspection — Evaluation of the Fourier transform (frequency information) of a 2D spatial image for features of interest.

Frame — The total area scanned in an image sensor while the video signal is not blanked. Essentially one picture out of a video stream. In interlaced scanning, two fields comprise one frame. Frame rate is typically 30 Hz.

Frame Buffer — Image memory in a frame grabber.

Frame Grabber — A device that interfaces with a camera and, on command, samples the video, converts the sample to a digital value and stores that number in a computer's memory.

Frame Rate — The frequency at which an image is completely updated on the display monitor.

Frame Transfer CCD (Charge Coupled Device) — The entire image is transferred from the sensing area to a storage area on a chip. Data (charge) is read out from the storage area in a full frame mode. This workhorse of the industry is also capable of non-RS-170 operation.

Front End System — The object, illumination, optics and imager blocks of an imaging system. Includes all components useful to acquire a good image for subsequent processing.

Front Lighting — The use of illumination on the camera side of an object so that surface features can be observed.

Front Porch — The area of the video waveform that sits between the start of horizontal blank and the falling edge (start) of horizontal sync.

G

Gamma — The numeric value for the degree of contrast in a video signal. The exponent in the power law relating output to input signal magnitude. Non-linear camera tube.

Gauging — In machine vision, non-contact dimensional examination of an object.

General-Purpose Vision System (GPMV) — A vision system that can be configured or adapted to many different applications.

Glints — Shiny, specular reflections from smooth objects or surfaces.

Global Method — An image processing operation uniformly applied to the whole image.

Gradient — The rate of change of pixel intensity (first derivative).

Gradient Space — A matrix containing values for the rate of change of pixel values or gray level intensity of the image.

Gradient Vector — The orientation and magnitude of the rate of change in intensity at a point or pixel location in the image.

Grating — An optical element with an even arrangement of rods or stripes with spaces between them for light to pass. Its ability to separate wavelengths is expressed in line pairs per millimeter, for example. A moiré grating of parallel dark and light stripes is an example. Also used for structured light projection.

Gray Level — A quantized measurement of image irradiance (brightness), or other pixel property typically in the range between pure white and black.

Gray Scale — Variations of values from white, through shades of gray, to black in a digitized image with black assigned the value of zero and white the value of one.

Grayscale Image — An image consisting of an array of pixels which can have more than two values. Typically, up to 256 levels (8 bits) are used for each pixel.

Guidance — Deriving properties in an image to describe a position at various points in time.

H

Halogen Lamp — An incandescent lamp with a gas similar to iodine inside which is constantly evaporated then redeposited on the filament.

Hardware — Electronic integrated circuits, boards and systems used by the system.

HDTV — High Definition TV proposed broadcast standard to double the current 525 lines per picture to 1,050 lines, and increasing the screen aspect ratio from 12:9 to 16:9. The typical TV of 336,00 pixels would increase to about 2 million.

Height/Range — Object profile is usually measured by changes in range or distances from the sensor. 3D techniques are usually used.

High-Pass Filter — Passes detailed high frequency image information, while attenuating low frequency, slow changing data.

High Speed Imaging — Image capture near, at or above 1800 parts per minute.

Histogram — A graphical representation of the frequency of occurrence of each intensity or range of intensities (gray levels) of pixels in an image. The height represents the number of observations occurring in each interval.

Histogram Analysis — Determination of the presence or absence of a feature or flaw based on the histogram values in a certain gray scale region.

Histogram Equalization — Modification of the histogram to evenly distribute a narrow range of image gray scale values across the entire available range.

Holography — Optically recording of the interference pattern from two coherent waves which forms a three-dimensional record or hologram.

Horizontal Blanking — The blanking signal that is produced at the end of each scanning line.

Horizontal Scan Rate — The speed at which the scanning beam in a display or a camera moves from side to side.

Horizontal Sync — The portion of a video signal indicating the end of a line of video information. This sync pulse is used by video equipment in order to maintain line synchronization with the incoming video signal.

Hough Transform — A global parallel method for locating both curved and straight lines. All points on the curve map into a single location in the transform space.

HSI (Hue-Saturation-Intensity) — A color representation. A mathematical conversion from RGB.

HSI Conversion — A mathematical conversion from the color RGB space to hue, saturation and intensity values.

HSV (Hue-Saturation-Value) — See HSI.

HSYNC — See Horizontal Sync.

Hue — One of the three properties of HSI color perception. A color attribute used to express the amount of red, green, blue or yellow a certain color possesses. White, gray and black do not exhibit any hue.

Hueckel Operator — An edge finding operator which fits an intensity surface to the neighborhood of each pixel and selects surface gradients above a specified threshold.

Hybrid Electro-Optic Sensor — A silicon sensor fabricated in a configuration to match spatial information generated by the imaging system, such as a PSD (position sensitive detector), concentric rings, pie shapes and others.

Hz — An abbreviation for Hertz or cycles per second. Often used with metric prefixes such as kHz or MHz for kilohertz and megahertz respectively.

I

Identification — The process of specifically identifying an object from a large class of objects through reading symbols.

Illumination — Normally a wavelength or range of wavelengths of light or visible used to enhance a scene so the detector, normally a camera, can produce an image.

Image — Projection of an object or scene onto a plane (i.e. screen or image sensor).

Image Analysis — Evaluation of an image based on its features for decision making.

Image Capture — The process of acquiring an image of a part or scene, from sensor irradiation to acquisition of a digital image.

Image Compression — Used to reduce the amount of memory required to store an image.

Image Distortion — A situation in which the image is not exactly true to scale with the object scale.

Image Enhancement — Image processing operations which improve the visibility of image detail and features.

Image Formation — Generation of an image of an object or scene on the imaging sensor. It includes effects from the optics, filters, illumination and sensor itself.

Image Intensifier — Usually an electron tube equipped with a light sensitive electron emitter at one end and a phosphor screen at the other. Used to provide electron gain for imaging in low light conditions such as night vision.

Image Memory — An internal, high speed, large capacity storage area on a frame grabber card or in a computer dedicated to image retention.

Image Plane — The plane surface of the imaging sensor, perpendicular to the viewing direction, at which the optics are focused.

Image Preprocessing — Methods of conditioning an image before it is acquired, such as a Look- Up Table (LUT) or attenuation.

Image Processing — Digital manipulation of an image to aid feature visibility, make measurements or alter image contents.

Incandescent Lamp — An electrical lamp in which the filament radiates visible light when heated in a vacuum by an electrical current.

Incident Light — Light that falls directly onto an object.

Index of Refraction — A property of a medium that measures the degree that light bends when passing between it and a vacuum.

Infrared — The region of the electromagnetic spectrum adjacent to the visible spectrum, just beyond red with longer wavelengths.

Infrared Imaging — Image formation using wavelengths just below the visible spectrum.

Inspection — Non-destructive examination of a workpiece to verify conformance to some criteria.

Intensity — The relative brightness of a portion of the image or illumination source. Also called brightness.

Interlaced — A system in which two (or more) interleaved fields are used to scan out one video frame.

Interlaced Scanning — A scanning process in which all odd lines then all even lines are alternately scanned. Adjacent lines belong to different fields.

Interline Transfer CCD (Charge Coupled Device) — Data (charge) is transferred simultaneously out by odd and even lines or fields directly from the image sensors to their corresponding sensor registers. The output from the camera is always one field (frame) behind the image being captured.

Interpolation — A mathematical method of regenerating missing or needed information.

I/O (Input/Output) — Data either entering or leaving a system.

J

Jitter — A time-based error caused by instabilities in synchronization and timing circuits.

JPEG (Joint Picture Experts Group) — An image compression standard.

K

No terms beginning with "K"

L

LAB — An acronym for the LAB color coordinate system.

Laplacian Operator — The sum of the second derivatives of the image intensity in both the x and y directions is called the Laplacian. The Laplacian operator is used to find edge elements by locating points where the Laplacian in zero.

Laser Illumination — Lighting an object with a laser source for frequency selection, pulse width (strobe) control or for accurate positioning.

Laser Radar — See LIDAR.

LED (Light Emitting Diode) — Often used as a strobe for medium speed objects.

Lens — A transparent piece of material, usually glass or plastic, with curved surfaces which either converge or diverge light rays. Often used in groups for light control and focusing.

Lens Types — Commonly used lenses are: 35mm, CCTV, Copying, Cylindrical, Enlarger, Micrographic, Video, and Wide Angle.

LIDAR (Light Detection And Ranging) — A system that uses light instead of microwaves for range and tracking measurements. LADAR uses a laser light source to measure velocity, altitude, height, range or profile

Light Tent — An arrangement of diffusing surfaces above the object to create a horizon to horizon diffuse illumination.

Lightpen — A pen on a cable used to select items from a display screen.

Line(s) of Light — One or more light stripes projected at a known angle onto the object. Deformation of this type of structured light results in 3D information in a 2D image.

Line Scan Camera — A solid state video camera consisting of a single row of pixels. Also called a Linear Array Camera.

Linear Array Camera — See Line Scan Camera.

Linearity — A basic measurement of how well an A/D or DAC is performing. The smaller the number, the better. Linearity is typically specified as a range or percentage of LSBs (Least Significant Bits).

Lighting — See Illumination.

Location — The point in X and Y image space where a recognized object is found.

Look-Up Table (LUT) — High speed digital memory used to transform image input values to outputs for thresholding, windowing and other mappings such as pseudo-color.

Low Angle Illumination — See Darkfield. Very useful to enhance and highlight surface texture features.

Low-Pass Filter — A digital or optical filter which passes slow changing, low frequency information, while attenuating high frequency, detailed edge information.

Luma — See Luminance.

Luma Bandpass — A type of filter that separates the luminance part of the NTSC or PAL signal from the chrominance part.

Luminance — The black-and-white part of a video signal. Also called Luma.

M

Machine Vision — The use of devices for optical non-contact sensing to automatically receive and interpret an image of a real scene, in order to obtain information and/or control machines or processes.

Magnification — The relationship between the length of a line or size of a feature in the object plane with the length or size of the same in the image plane.

Mask — 1) Setting portions of an image ate neighbors to a constant value; 2) A filter matrix used as a convolution operator; 3) A logical or physical structure placed in an optical system to prevent viewing or passing of information in a certain spatial or frequency region.

Material Handling — Hardware systems that provide motion, indexing and/or orientation both during manufacture and the inspection process.

Matrix Array Camera — See Area Array Camera.

Measurement — Verification that a workpiece conforms to specified tolerances, such as dimensions, colors or textures.

Median Filter — A method of image smoothing which replaces each pixel value with the median grayscale value of its immediate neighbors.

Memory — The internal, high-speed, large capacity working storage in a computer where data and images may be both stored and retrieved.

Micron — One millionth of a meter, also called a micrometer.

Mirror — A smooth, highly polished surface, for reflecting light. It may be plane or curved. Mirrors are fabricated by depositing a thin coating of silver or aluminum on a glass substrate. First surface mirrors are coated on the top surface, thus avoiding a second ghost image produced when light is reflected off the back surface after passing through the glass twice.

MIPS (Millions of Instructions per Second) — A measure for computer processing speed.

Modulation Transfer Function (MTF) — The ability of a lens or optical system to reproduce (transfer) various levels of detail (modulation) of an object to the image as the frequency (usually sinusoidal) increases.

Moiré — A type of image artifact when a pattern occurs on the screen — generated when two oscillators of different frequencies beat together to create a new, unwanted frequency.

Moiré Interferometry — A method to determine 3D profile information of an object or scene, using interference of light stripes. Two identical gratings of known pitch are used. The first creates a shadow of parallel lines of light projected on the object. The second is placed in the imaging train, and superimposed on the shadow cast by the first grating, forming a moiré fringe pattern. Distance between the fringes or dark bands is directly related to range or profile. Varying the gap between the lines changes the sensitivity.

Moiré Pattern — A pattern resulting from the interference of light when gratings, screens or regularly spaced patterns are superimposed on one another. Two stacked window screens create this effect.

Moiré Topography — A contour mapping technique in which the object is both illuminated and viewed through the same grating. The resulting moiré fringes form contour lines of object elevation or profile.

Monochromatic — Refers to light having only one color or a single wavelength of radiation.

Monochrome — Refers to a black and white image with shades of gray but no color. A monochrome signal is a video source having only one component.

Monotonic — An A/D or DAC is monotonic if for every increase in input signal, the output increases also and does not back up.

Morphology — Image algebra group of mathematical operations based on manipulation and recognition of shapes. Also called mathematical morphology. Operations may be performed on either binary or gray scale images. Parallel processors are useful to implement.

MOS Array — Metal Oxide Semiconductor camera array sensor with random addressing capability, rows and columns of photodiodes and charge sent directly from the photodiode to the camera output.

Mouse — A hand operated pointing device used to select items from a display screen.

MPEG (Moving Picture Experts Group) — A compression algorithm for video sequences. Differs from JPEG in that MPEG takes advantage of the redundancy on a frame-to-frame basis of a motion video sequence, whereas JPEG does not.

N

Neural Networks — A computing paradigm which processes information based on biological nervous systems. No programming is involved as in artificial intelligence. Rather, decisions are made based on weighted features analyzed by interconnected nodes of simple processing elements using analog computer-like techniques.

Noise — Irrelevant or meaningless data resulting from various causes unrelated to the source. Random, undesired video signals.

Noninterlaced — A method of scanning in which all the lines in the frame are scanned out sequentially. Also known as progressive scan.

Normalized Correlation — Removes the absolute illumination value from a traditional correlation, making the algorithm less sensitive to light variations.

NTSC (National Television Standards Committee) — A 60 Hz standard for encoding color video signals. Used in North America, Japan, and most of South America.

O

Object — The 3D item to be imaged, gauged or inspected.

Object Features — Any characteristic that is descriptive of an image or region, and useful for distinguishing one from another. A feature may be any measurable item such as length, size, number of holes, surface texture amount or center of mass.

Object Plane — An imaginary plane at the object, which is focused by the optical system at the image plane on the sensor.

Oblique Illumination — A lighting direction at an angle which emphasizes object features by shadows produced.

OCR (Optical Character Recognition) — A technique used to read and intelligently interpret characters, numbers of symbols, based on pre-trained image models.

OCV (Optical Character Verification) — A technique used to compare characters to pre-trained image models. Unlike OCR, OCV only makes comparisons and does not actually "read" or determine the character.

OEM (Original Equipment Manufacturer) — Supplies components to another for resale.

Oil Mist — An environmental contaminant which builds up on optical surfaces.

Opaqueness — Degree to which an object does not transmit light.

Opening — An erosion followed by a dilation, it is the opposite of the closing morphological operator.

Optical Character Recognition — See OCR.

Optical Character Verification — See OCV.

Optical Computing — Performing operations usually handled by electronic, serial computers with optical or photonic circuits/elements in parallel at near the speed of light.

Orientation — The angle or degree of difference between the object coordinate system major axis relative to a reference axis as defined in a 3D measurement space.

P

PAL (Phase Alternation Line) — A 50 Hz composite color video standard used in many parts of the world.

Pantone Matching System (PMS) — A system of describing colors by assigning numbers.

Parallax — The change in perspective of an object when viewed from two slightly different positions. The object appears to shift position relative to its background, and also appears to rotate slightly.

Parallel Processor — A redundant hardware design using a number of processors so multiple pixels may be processed at the same time.

Parent — An object which wholly contains another object called a child.

Passthrough — The continuous digitization and display of an image or video.

Pattern Recognition — A process which identifies an object based on analysis of its features.

Peak White — The highest point in the video waveform that the video level can reach and still stay within spec. If the level does become greater than peak white, it is referred to as whiter-than-white.

Pedestal — An offset used to separate the active video from the blanking level. When a video system uses a pedestal, the black level is above the blanking level by a small amount. When a video system doesn't use a pedestal, the black and blanking levels are the same.

Perceptron — The basic processing element used in neural networks. A simple analog circuit with weighted inputs and a nonlinear decision element such as a hard limiter, threshold logic or sigmoid nonlinearity.

Phase Adjust — A method of adjusting the color in an NTSC or PAL video signal.

Photodiode — A single photoelectric sensor element, either used stand-alone or a pixel site, part of a larger sensor array.

Photometry — Measurement of light which is visible to the human eye (photopic response).

Photopic Response — The color response of the eye's retinal cones.

Pinhole — A small, sharp edged hole, acts as a lens aperture which produces a soft edged image, is distortion free, with a wide field of view and large depth of field.

Pixel — An acronym for "picture element." The smallest distinguishable and resolvable area in an image. The discrete location of an individual photo-sensor in a solid state camera.

Pixel Clock — Used to divide the incoming horizontal video into pixels. The pixel clock has to be stable (with a very small amount of jitter) relative to the incoming video or the picture will not be stored correctly.

Pixel Counting — A simple technique for object identification representing the number of pixels contained within its boundaries.

Pixel Drop Out — Timing problems in the video system can cause pixel drop out, which creates image artifacts.

Polarized Light — Light which has had the vibrations of the electric or magnetic field vector typically restricted to a single direction, in a plane perpendicular to its direction of travel. It is created by a type of filter which absorbs one of the two perpendicular light rays. Crossing polarizers theoretically blocks all light transmission.

Polarizer — An optical device which converts natural or unpolarized light into polarized light by selective absorption of rays in one direction, and passing of rays perpendicular to the polarizing medium. Usually fabricated from stretched plastic sheets with oriented, parallel birefringent crystals. The first polarizers were constructed with parallel wires.

Positioning Equipment — Used to bring the part into the field of view, or to translate when multiple images or views are required.

Precision — The degree of spread or deviation between each measurement of the same part or feature. Repeatability.

Presence Verification — To look for an object to ensure that it exists.

Prism — An optical device with two or more non-parallel, polished faces from which light is either reflected or refracted. Often used to redirect light as in binoculars.

Processing Speed — A measure of the time used by an imaging system to receive, analyze and interpret image information. Often expressed in parts per minute.

Progressive Scan — A method of scanning in which all the lines in the frame are scanned out sequentially. Also known as interlaced.

Profile — The 3D contour of an object.

Q

No terms beginning with "Q"

R

Radiometry — Measurement of light within the entire optical spectrum.

RAM (Random Access Memory) — Computer memory that allows data to be read or written at a particular location without having to pass sequentially through preceding locations.

Random Access — The ability to read out chosen lines or windows of information from an imager as needed, without following the RS-170 standards.

Range Measurement — Determination of the distance from a sensor to the object.

Raster — A series of scan lines that make up a television or computer display. All of the scan lines that make up a frame of video form a raster.

Raster Line — See Scan Line.

Raster Scan — A scanning pattern, generally from left to right while progressing from top to bottom of the imaging sensor or the display monitor. Generally comprised of two fields composed of odd and even lines.

Real-Time — In image processing, an operation or a function that is complete in one frame time is said to be performed in real-time.

Real-Time Processing — In machine vision, the ability of a system to perform a complete analysis and take action on one part before the next one arrives for inspection.

Reflection — The process by which incident light leaves the surface from the same side as it is illuminated.

Refraction — The bending of light rays as they pass from one medium (i.e. air) to another (i.e. glass), each with a different index of refraction.

Region — Area of an image. Also called a region of interest.

Region of Interest (ROI) — See Region.

Registration — The closeness of the part to the actual position expected for image acquisition.

Reject — A mechanism used on a manufacturing line to remove defective or sample product from the main stream or conveyor. Reject design is usually customized to the process.

Repeatability — The ability of a system to reproduce or duplicate the same measurement. The total range of variation of a dimension is called the 6-sigma repeatability. See Precision.

Resolution — A basic measurement of how much information is on the screen. Higher resolution means much more detail in the image.

Resolution, Feature — The smallest object or feature in an image which may be sensed.

Resolution, Image — The number of rows and columns of pixels in an image.

Resolution, Measurement — The smallest movement measurable by a vision system.

Resolution, Pixel Grayscale — The number of resolvable shades of gray (i.e. 256).

Resolution, Spatial — A direct function of pixel spacing. Pixel size relative to the image FOV is key.

Reticle — An optical element with a pattern located in the image plane to assist in calibration, measurement or alignment of a system or instrument. Examples are cross lines or grids.

RGB (Red, Green, Blue) — The three primary color system used for video color representation.

Ringlight — A circular lamp or bundles of optical fibers arranged around the perimeter of an objective lens to illuminate the object in the field below it. A wide variety of sizes are available on both a stock and custom basis.

ROI (Region of Interest) — See Region.

Rotation — Translation of a part about its center axis from the expected orientation in X and Y space. Expressed in degrees.

RS-170 — The Electronic Industries Association (EIA) standard governing monochrome television studio electrical signals. The broadcast standard of 30 complete images per second.

RS-232-C — The Electronic Industries Association (EIA) standard governing serial communications over a twisted pair. Good to about 150 feet.

RS-330 — Standard governing color television studio electrical signals.

RS-422; RS-423; RS-449 — The Electronic Industries Association (EIA) standards for serial communication protocols intended to gradually replace the widely used RS-232-C standard.

Run Length Encoding — A data reduction method to code a binary image. For each line in an image, data is stored denoting only the starting location of a blob and object and the length of the run of that line over the object.

S

Sample Rate — How often the A/D converter will take a sample of the video. Determined by the pixel clock.

Saturation — The amount of color present. One of the three properties of color perception along with hue and intensity. See HSI.

Scaling — A method of altering the size of an image in the x and/or y dimensions, which changes the effective resolution of the image.

Scan Line — an individual sweep across the face of the display by the electron beam that makes the picture.

Scanner (galvo & polygon mirror) — An image sensor which uses a swept or scanned beam of light (usually a laser) to generate or acquire a one or two dimensional grayscale reflectance pattern.

Scattering — Redirection of light reflecting off a surface or through an object. See Diffuse. Scene — The object and a background in its simplest form. A portion of space imaged for investigation or measurement.

Scene Analysis — Performing image processing and pattern recognition on an entire image.

Segmentation — The process of dividing a scene into a number of individual objects or contiguous regions, differentiating them from each other and the image background.

Serration Pulses — In a composite video system, serration pulses tell the receiver where the vertical sync is.

Shading — The variation of the brightness or relative illumination over the surface of an object, often caused by color variations or surface curvature.

Shape — An object characteristic, often referring to its spatial contour.

Shape from Shading — A 3D technique that uses shadows from interaction of the object and the light source to determine shape.

Sharpening — An image processing operation which enhances edges. An unsharp mask adds a low pass filtered image to the original, resulting in edge enhancement.

Shutter — An electrical or mechanical device used to control the amount of time the imaging surface is exposed to light. Often used to stop blur from moving objects.

Signal-to-Noise Ratio — A basic measurement of image quality. The magnitude of the signal (what is desirable) divided by the amount of interference with the signal (noise). Usually described in decibels (dB).

Silhouette — A black and white image of an object illuminated by backlighting. Simple Lens — A lens with only a single element.

Sinusoidal Projection — Use of a grating in which the dark stripes vary in their density sinusoidally across each one, rather than constant black. Improved profile or range discrimination is possible when used in a moiré type configuration.

Size — An object characteristic typically measured by x and y dimensions. Size may be expressed in pixels, the system calibrated units of measure or classes or size groups.

Smart Camera — A complete vision system contained in the camera body itself, including imaging, image processing and decision making functions.

Sobel Transform — A 3x3 convolution used for edge enhancement and locating.

Solid-State Camera — A camera which uses a solid state integrated circuit chip to convert incident light or other radiation into an analog electrical signal.

Span — The allowance of gray level acceptance for thresholding, adjustable from black to white from 0 to 100%.

Spatial Light Modulator — A transparent screen used in optical computer systems to introduce an image into the optical processing path. Similar to liquid crystal computer display screens, their resolution approaches 512x512 and grayscale imaging 8 bits. Also SLM.

Spectral Analysis — Evaluation of the wavelength composition of object irradiance. Spectral Characteristics — The unique combination of wavelengths of light radiated from a source or transmitter or reflected from an object.

Spectral Response — The characteristic of a sensor to respond to a distribution of light by wavelength in the electromagnetic spectrum.

Specular Reflection — Light rays that are highly redirected at or near the same angle of incidence to a surface. Observation at this angle allows the viewer to "see" the light source.

Speed — An object characteristic expressed in distance moved per unit time. Velocity. Image blur may be caused by high speeds unless strobes or shutters are used to "stop motion."

SRI Algorithms — A rich set of routines used for geometric analysis and identification developed at the Stanford Research Institute in the early 1970s. Four main steps are: 1) Convert the image to binary; 2) Perform connectivity analysis to identify each blob or object; 3) Calculate the core statistical features for image objects; and 4) Calculate additional user selected features.

Stadimetry — A range measuring technique based on the apparent size measurement of a known size object in the field-of-view.

Statistical (Theoretic) Pattern Recognition — Statistical analysis of object features to perform recognition and classification.

Stereo (Passive) — For imaging, the use of two cameras, offset by a known distance and angle, to image the same object and provide range, depth or 3D information. Active stereo uses a controlled or structured light source to provide 3D data.

Stereo Photogrammetry — See Shape from Shading.

Stereoscopic Approach — The use of triangulation between two or more image views from differing positions. Used to determine range or depth.

Strobe Duration — The amount of time, expressed in microseconds, during which the flash lamp (strobe) is at 90% intensity.

Strobed Light — Brief flashes of light for observing an object during a short interval of time, typically used to "stop" movement and resulting image blur. Strobes may use xenon flash tubes, banks of LEDs or a laser to illuminate the scene.

Structural (Syntactic) Pattern Recognition — Evaluation of the relationship of object features in a specific order, i.e. decision trees, to perform recognition and classification.

Structured Light — Points, lines, circles, sheets and other projected configurations used to directly determine shape and/or range information by observing their deformation as it intersects the object in a known geometric configuration.

Subpixel Resolution — Mathematical techniques used on gray scale images to resolve an edge location to less than one pixel. A one tenth pixel resolution is reasonable in the factory. Syntactic PR — See Structural Pattern Recognition.

Sync — The portion of a video signal indicating either the end of a field or end of a line of video information.

Sync Generator — A circuit that provides sync signals.

Sync Pulse — Timing signals used to control the television scanning and display process. The horizontal sync triggers tracing of a new line from left to right, while the vertical sync initiates the start of a new field.

Synchronous — A camera characteristic denoting operation at a fixed frequency locked to the AC power line (typically 60 or 50Hz).

System Performance Measures — Accuracy, precision or repeatability, and alpha and beta risk for a given throughput rate specify the performance of a vision system.

Systems Integration — The art of assembling hardware, software, components, mounts and enclosures to produce a system that meets a customer's specification.

T

Tail End System — The operator interface, I/O and communications blocks of a vision system. Includes all aspects of information display and handling. Is often overspecified.

TDI (Time Delay Integration) Camera — Similar to a line scan camera, a TDI camera is comprised of a number of rows of pixels. As an object such as a web moves, the charge from one row is passed to the next row, synchronously continuing the integration. Requires far less illumination intensity than the standard line scan.

Template — An artificial model of an object or a region or feature within an object.

Template Matching — A form of correlation used to find out how well two images match.

Texture — The degree of smoothness of an object surface. Texture affects light reflection, and is made more visible by shadows formed by its vertical structures.

Thickness — The measurement in the third dimension (length and width being the other two) from one object surface to another using one or two 3D range sensors or other technique.

Thresholding — The process of converting gray scale image into a binary image. If the pixel's value is above the threshold, it is converted to white. If below the threshold, the pixel value is converted to black.

Throughput Rate — The maximum parts per minute inspection rate of a system.

Timebase Corrector — Repairs a video signal that has bad sync.

Top Hat — A morphological operator comprised of an opening followed by a subtraction of the output image from the original input image.

Trackball — A stationary ball used as a pointing device to select items from a display screen.

Transition — For an edge in a binary image, the location where pixels change between light and dark.

Translation — Movement in the X and/or Y direction from a known point.

Translucent — An object characteristic in which part of the incident light is reflected and part is transmitted. The transmitted light emerges from the object diffused.

Transmittance — The ratio of the radiant power transmitted by an optical element or object to the incident radiant power.

Transputer — A type of computer architecture with several CPUs connected in parallel.

Triangulation — A method of determining distance by forming a right triangle consisting of a light source, camera and the object. The distance or range can be calculated if the camera-to-light source distance and the incident to reflected beam angle are both known. Based on the Pythagorean relation.

True Color — The imaging system is representing the image on the display with enough bits and in the correct format so that there is no loss of color image detail.

Tube Type Camera — A camera in which the image is formed on a fluorescent screen, then read out sequentially in a raster scan type pattern by an electron beam for conversion to an analog voltage proportional to incoming light intensity.

U

Ultrasonic Imaging — Use of ultrasound waves as the imaging "illumination" source.

Ultrasound — Low frequency radiated acoustical waves just above human sound perception which are useful for penetration and "illumination" for inspection of solid objects.

Ultraviolet — The region of the electromagnetic spectrum adjacent to the visible spectrum, but of higher frequency (shorter wavelength) than blue ranging from 1 to 400 nm. UV A ranges from 320 to 400 nm while UV B falls between 280 and 320 nm.

User Interface — Includes display, operator, user controls and a means to access and modify custom user programming.

V

Validation — A rigid set of tests to verify that a system performs as documented.

Variable Scan Input — Frame grabber capability to accept a variety of non RS-170 input formats from a variety of cameras. Allows operation above the 30 Hz limit.

Vector Scope — Used to determine the color purity of an NTSC or PAL video system. Vertical Scan Rate — See Frame Rate.

Verification — Activity providing qualitative assurance that a fabrication or assembly process was successfully completed.

Vertical Sync — The portion of a video signal indicating the end of a field of video information. This sync pulse is used by video equipment in order to maintain field synchronization with the incoming video signal.

VESA (Video Electronics Standards Association) — A 32-bit display or other hardware card.

VGA (Video Graphics Array) — The IBM video display standard of 16 colors.

Video — Visual information encoded in a specific bandwidth and frequency spectrum location originally developed for television and radar imaging.

Video Quality — A video image that has a high signal-to-noise ratio and is free of any image artifacts has high image quality.

Video Waveform — Made up of several parts that are all required to make up a video image that can be accurately displayed.

Vidicon — A generic name for a camera tube of normal light sensitivity. It outputs an analog voltage stream corresponding to the intensity of the incoming light.

Visible Light — The region of the electromagnetic spectrum in which the human retina is sensitive, ranging from about 400 to 750 nm in wavelength.

Vision Engine — Analyzes the image and makes decisions, using a very fast processor inside a computer. It performs dedicated evaluation of the pre-processed image data to find features and make measurements. Unlike a personal computer, the vision engine is built for speed, not flexibility.

VSYNC — See Vertical Sync.

W

Wavelength — The distance covered by one cycle of a sinusoidally varying wave as it travels at or near the speed of light. It is inversely proportional to frequency.

Well — A morphological operator comprised of a closing followed by a subtraction of the output image from the original input image.

Window — A selected portion of an image or a narrow range of gray scale values.

Windowing — Performing image processing operations only within a predefined window or area in the image.

X

Xenon Strobe — A gas filled electronic discharge tube, useful for high speed, short duration illumination for inspection.

X-ray — A portion of the electromagnetic spectrum beyond the ultraviolet with higher frequency and shorter wavelengths. Able to penetrate solid objects for internal, non-destructive evaluation.

Y

No terms beginning with "Y"

Z

Zoom Lens — A compound lens which remains in focus as the image size is varied continuously. May be motorized or manually operated.