EPIX, Inc. Home Page

Applications, Features, and Glossary of EPIX Products




Active Video
Portion of a video signal which contains information on intensity and color; i.e the viewable portion.
Area of interest. An area of an image subject to modification, loading, saving, printing, etc. Typically, when used in conjunction with, or contrasted against, the term ROI , an AOI is rectangular, with sides parallel to the image axis. Sometimes referred to as a window within the image, but not to be confused with a window of a Graphical User Interface, such as Windows™ or Java™.
Analog Camera
A camera which outputs active video and timing information as continuously varying electrical signals.
Area of Interest
See AOI.
Area Scan
A method of video acquisition from a two-dimensional array of photoelements.
Authorization Key
Device which must be plugged into the computer, typically the parallel port, to enable use of software protected against duplication.
Back Porch
The portion of a video signal which follows the rising edge of the horizontal sync and precedes the active video.
The base 2 numbering system used by most computers and digital circuits.
The smallest, fundamental, unit of binary data.
Bits per Pixel
Number of bits assigned to represent grey level, or luminance and chrominance, information in a single pixel. Indirectly, the number of different discrete levels that represent the variations of such information. For example, 8 bits per pixel can yield 256 distinct grey levels.
BGR Color
Same as RGB Color, with the order changed to blue, green, and red.
The BitMaP file format specified by Microsoft for use with Windows for saving graphics and digital images.
RAM or other memory used to store data. See Image Buffer, Frame Buffer.
To convert a field or frame of video into pixel values stored in a frame buffer.
Color Temperature
The color of whitish illumination expressed in degrees Kelvin of the temperature of an ideal blackbody yielding equivalent illumination. Lower temperature illuminators such as tungsten lamps (2800 to 3000°) radiate more reddish (lower energy) wavelengths, higher temperature illuminators such as cool white fluorescent lamps (4300°) radiate more bluish (higher energy) wavelengths.
Consultative Committee International Radio. The European video standard for monochrome television transmission which specifies 625 lines per frame, divided into two interlaced fields, and a 25 HZ frame rate.
Chroma Key
A rule for combining two video signals, or two images, based on the color of one image, such as: The output signal/image is taken from signal/image A, except where A contains the chroma key value, where the output is taken from signal/image B, allowing signal/image A and B to be overlayed, with A's chroma key pixels effectively transparent.
The process of restoring a DC reference level which was removed to make an AC coupled signal. Without a known DC reference level, a video waveform can't be digitized correctly.
Color Gamut
Color range available with a display device. A display screen's color gamut is dependent on the CRT's phosphor coating. A printed image's color gamut is dependent on the inks and paper.
Color Key
See Chroma Key.
Color Lookup Table
Table used to map an index pixel's value to (typically) three color values.
Composite Video
Video signal which combines active video, sync, and blanking into a single waveform. Examples include NTSC and PAL.
A measure of the relative intensity differences within an image. A low contrast image may be dark (a foggy night), or bright (a foggy day); a high contrast image has bright and dark areas. The difference between an image's lightest and darkest grey level value.
Digital Camera
A camera which delivers active video and timing information as discrete data.
To convert an analog signal into discrete values. Sometimes used as synonym for Capture.
See Authorization Key.
Digital Signal Processor. Component which executes computations and gives instructions to manipulate data, specifically designed to operate on signals and images, in contrast to general purpose processors.
Extended Industry Standard Architecture Bus. Faster successor to the ISA bus. Any ISA board will function correctly in an EISA slot.
Equalization Pulses
Two groups of pulses which occur before and after serrated vertical sync pulses. Equalization pulses occur at twice the normal horizontal scan rate to ensure correct 2:1 interlacing.
Frame Buffer
An Image Buffer specified to receive Captured video fields or frames. Often, an Image Buffer attached to the video capture hardware.
Front Porch
The portion of a video signal that follows the start of the horizontal blank and precedes the horizontal sync pulse.
See Color Gamut.
To recover and use the original horizontal and vertical timing control signals from a video signal.
Horizontal Blanking
The portion of the video signal when brightness is suppressed at the end of a scan line during which the electron beam retraces from right to left on the screen.
Horizontal Sync
A pulse contained within horizontal blanking which synchronizes hardware with the start/end of each line of each frame.
HSB Color
Color space composed of Hue (e.g. red, yellow, orangeish-red, etc.), Saturation (degree of dilution with white), and Brightness (level of intensity). A color space based upon human perception of color.
A rectangular grid of pixels.
Image Buffer
RAM or other memory used to hold an image or images.
Image Sequence
A linear group of images, usually time indexed.
Use of two or more fields to scan a video frame, each field representing alternate lines. An interlaced system decreases perceived flicker by increasing the field update rate. Compare with Progressive Scan.
Technique used to determine when a device requires attention, by having the device alter the processor's execution in a controlled manner. Compare with Polling.
Industry Standard Architecture Bus. The original 8 or 16 bit bus of the IBM PC.
Line Scan
Describes a method of video acquisition which uses a one dimensional array of photoelements.
Low Voltage Differential Signalling. Also known as RS-644, an EIA standard for differential signalling format for binary data. Capable of higher speeds over greater distance as compared to RS-422.
Describes a video mode which only has one component, usually luminance.
A device or component which steers one of several input signals to its output as directed by a control input. Also spelled Multiplexer.
National Television Standards Committee. Color video standard composed of a luminance signal and two color difference signals. 30 frames per second, 525 lines per frame, where 483 of these lines are visible on the screen, the remainder used for blanking. For interlaced video, the 525 lines are divided into 262.5 lines per field (see Interlace).
Phase Alternation Line. Color video standard used in Europe and other countries. 625 lines per frame, 25 frames per second.
See Color Lookup Table.
To move the viewed area of text or image left and right through the horizontally larger text or image. See also Scroll.
The ISA Bus, 16 bit version. Capable of transferring two to four megabytes per second.
Peripheral Component Interconnect Bus. A 32 or 64 bit wide bus operating at 33 or 66 MHz capable of transferring 132, 264, or 528 million bytes per second (or approximately 125.88, 251.77, or 503.54 megabytes per second).
A file format specified by Zsoft for saving screen graphics
Short for picture element. The fundamental unit of digital imaging. The smallest unit of an image with homogeneous intensity and color. The numeric representation of an intensity and color. Sometimes used interchangeably with photosite to specify the light sensitive cells that compose a solid state imaging sensor.
Pixel Clock
An oscillator, timing circuit, or externally provided signal which is used to divide an incoming scan line of video into pixels.
One component value of a pixel. A monochrome pixel contains one pixie, a color pixel typically contains three or four pixies. Example: An RGB pixel is composed of green, red, and blue pixies.
Technique used to determine when a device requires attention, by having the processor continuously test the device's status. See Interrupt.
Progressive Scan
(1) A camera in which all rows of the sensor are exposed at the same time, and/or (2) A camera whose video output is not interlaced. Some cameras have a progressive scan sensor and interlaced video output, eliminating temporal shifts between fields but maintaining compatibility with interlaced monitors and frame grabbers. Compare with Interlace.
A technique that assigns a color to each grey level of a monochrome image, helping visualize patterns of intensities.
A series of scan lines which constitute a field or frame of video.
Region of Interest
See ROI.
Resolution - Depth
Measure of the number of bits, grey levels, and colors which compose each pixel.
Resolution - Spatial
Measure of the number of pixels, horizontally and vertically, that compose an image.
Resolution - Temporal
Measure of the number of images that compose an image sequence. Implies a period of time, at a fixed time interval per image, or implies a time interval per image, for a fixed period of time.
RGB Color
Color space composed of three components: red, green, and blue. The natural color space for video hardware, as video monitors use red, green, and blue phosphors.
Region of Interest. An area of an image subject to modification or analysis. Typically, when used in conjunction with, or contrasted against, the term AOI , an ROI is not limited to a rectangular shape with sides parallel to the image axis, but may be an ellipse or rectangle rotated with respect to the image axis, or an arbitrary path or polygon.
EIA standard for monochrome video which defines voltage levels, blanking times and width of sync pulses. 525 lines, 30 frames per second.
(1) EIA standard for single-ended signalling of binary data, (2) EIA standard for interpreting a bit stream as bytes, (3) EIA standard for communication of data and status between two devices using a group of RS-232 signals, and (4) EIA standard for the physical connectors used for RS-232 communication cables. The RS-232 connection between a computer and modem, or between a computer and an RS-232 controlled camera, involves all of the above specifications.
EIA standard for differential signalling format for binary data. Capable of higher speeds over greater distance as compared to RS-232.
Scan Line
The (almost) horizontal line scanned by the electron beam in a video monitor. Also, the analogous line scanned by a video camera.
To move the viewed area of text or image up and down through the vertically larger text or image. See also Pan.
Serration Pulses
Synchronization pulses within vertical sync, which occur at twice the normal horizontal scan rate to ensure correct 2:1 interlacing.
To capture a single video field or frame and store it in a frame buffer.
A variation of the NTSC or PAL video format, in which the luminance and chrominance signals are separate, providing higher quality images.
A file format specified by TrueVision for saving digital images.
Image processing operation which transforms a grey level or color image into a two-toned, or binary image, by comparing each pixel against a threshold value.
Tagged Image File Format. An industry standard file format used to save digital images. Most widely used file format since it is not company specific.
Specifically: Transistor Transistor Logic. Generally: Single-ended signalling format for binary data. which uses levels of 0 and 5 volts (nominal). TTL is intended for high speed signalling between integrated circuits on the same or adjacent boards, although may be used at slow speeds over several feet.
White Balance
Corrections to a color image, or color video, so that a whitish object appears white. The color balance is affected by the color temperature of the illumination (e.g. sunlight versus fluorescent light), and also affected by the display monitor.
Vertical Blanking
The portion of the video signal when brightness is suppressed at the end of a field, during which the electron beam retraces from the bottom to the top of the screen.
Vertical Sync
The portion of the video signal, within vertical blanking, which synchronizes hardware with the top/bottom of each frame.
Video Format
Specifications which define a video signal. These specifications include voltage levels, blanking times, width of sync pulses, lines per frame, and frames per second. Examples of common standard video formats are: NTSC, CCIR, PAL, and RS-170.
Video Sampling
The process of obtaining digital data from an analog video signal.
YCrCb Color
Color space where the Y component represents the brightness signal and the Cr and Cb components represent color difference signals. 4:2:2 YCrCb indicates that Y is sampled at twice the rate of Cr and Cb.
To magnify an image in order to observe more detail.
Back to the EPIX home page

Image Processing Products For Research and Industry