Glossary

A/D:	Acronym for Analog-to-Digital converter which converts an analog signal to a digital signal. A/D converters may be referred to as 8-bit, 10-bit, 12-bit converters. This just means the analog representation when converted into digital will have a tonal range from 0-255 for 8-bit, 0-1023 for 10-bit and 0-4095 for 12-bit converters.
Adapter:	Adapter may have multiple references when speaking about imaging technology. An adapter could be a lens adapter, a connector that changes the gender, or an interface that talks to a camera.
AGC:	Automatic gain control is a method to control the amount of brightness seen in the image. Typical method is increasing or decreasing the gain on a camera to a median level set by the user.
AIA:	Automated Imaging Association. http://www.machinevisiononline.org/
Aliasing:	An image sampling error in digital systems manifesting itself as spatial frequency components beyond the sampling limit (Nyquist frequency) that are displayed at progressively lower frequencies. Aliasing can produce moiré pattern artifact in an image when the spatial frequency of the signal exceeds the sampling rate of the digitizer.
Analog:	A common way to describe the difference between analog and digital is to think of a watch. An analog watch is one that has a hand that sweeps continuously around the dial. A digital watch has discrete numbers. Therefore, analog means a signal whose function is continuous.
Aperture:	Most often is in reference to the numerical aperture of a lens also known as the f-stop.
ASCII (American Standard Code for Information Interchange):	An 8-bit code used to designate alphanumeric and other characters and symbols for computers.
Aspect Ratio:	Often used to reference the ratio of width to height for an image in some standard format. Such as 4:3 used in conventional (native format) or 16:9 used in HDTV format.
Asynchronous:	When a camera system is taking images not synchronized with the framing of a camera, it is often referred to as being asynchronous. This can also mean literally any function or signal when not in sync or unison with a reference signal can be referred to as asynchronous (not in sync).
Automatic Gain Control (AGC):	Automatic gain control is a method to control the amount of brightness seen in the image. Typical method is increasing or decreasing the gain on a camera to a median level set by the user.
Backside-illuminated:	A type of CCD sensor, full-frame (100% fill factor), that has been uniformly reduced thickness of approximately 10 µm so that an image can be focused on the backside of the sensor. The advantage of backside illumination is the metal layers used to pass signals are on the front of the sensor. Therefore, the obstruction to the pixel is 100 % free.
Bandwidth:	Bandwidth is often used in the context of data transfer such as a sensor’s bandwidth or an interface data bandwidth. Bandwidth is the difference between an upper and lower limit of frequency in cycles per second (hertz).
Baud rate:	The number of bits per second often referred to in serial communication interfaces.
Beam splitter:	An optical device used to split a single image path or light beam into two or more separate paths.
Binned Readout:	A type of sensor architecture where individual pixels are combined in a module (2) format to produce higher sensitivity. Binned readout architecture is easier to implement in a CCD rather than a CMOS structure.
Binning:	A technique for combining the signal (charge for CCDs) in multiple pixels, adjacent or in some repeatable pattern, so that the combined signal is read out as an image.
Binning factor:	The number of pixels, adjacent or in some repeatable pattern, combined through binning. A binning factor of 4 x 4s has 16 pixels combined in some pattern such as 4 row and four columns.
Bit:	A single binary unit of information where the information is either a 1 or a 0 for notation. If you have 8-bits this is also referred to as a byte. If you have 16-bits this is also referred as two bytes or a word. However, some words can be 16, 32 or even 64-bits long.
Bit depth:	The number of bits that are digitized by the A/D converter or the representation of how many bits can be made from the signal in a pixel.
Bit rate:	The rate of transmission of a digital signal is often referenced by its bit rate.
Blanking Period:	portion of the composite picture signal which lies between the trailing edge of the horizontal sync pulse and the trailing edge of the corresponding blanking pulse.
Blooming:	Often referred to as the overexposure of an image. The defocusing of regions of the picture where the brightness is at an excessive level, due to enlargement of spot size and halation of the fluorescent screen of the cathode-ray picture tube. In a camera, sensor element saturation and excess which causes widening of the spatial representation of a spot light source.
BNC connector:	A coaxial type of connector commonly used on professional video systems. The connector is used to couple coaxial cables to video and other high-frequency electronic equipment.
Bus:	An interface that provides a data & control pathway to move information. On high speed systems, this is often a parallel interface. Examples of standard bus architectures include PCI, SATA, CameraLink, PanelLink, IEEE-1394, ISA and so forth. A system-level bus will typically include a data bus, address bus, control or status bus, and power bus.
Candela (cd):	The luminous intensity emitted by a light source. One candela emits one lumen per steradian.
CCD:	Charge-coupled device.
CCTV:	Closed-circuit television
CD (cd):	Abbreviation for candela.
Charge:	In a CCD sensor, the number of electrons contained in the pixel well is often referenced as the charge in the pixel. This charge is then moved from pixel to pixel for readout. CMOS sensors do not move charge but rather have a voltage level within the pixel.
Charge Smear:	Residual charge or voltage left behind in a pixel when read out on the current image. The artifact may look like a ghost image. When operating at very high frame rates, this is a common problem in CMOS sensors.
Charge transfer:	In a CCD sensor, transferring charge must be efficient. The parametric for evaluating how much charge can be transferred is expressed as the charge transfer efficiency (CTE). Scientific-grade CCDs typically have a CTE of 99.9998%, where 100% is perfect.
Chroma:	The quality of color which represented by both hue and saturation. White, black, and grays have no chroma.
Chromatic Aberration:	This is defined as an optical defect in a lens which causes different colors or wave lengths of light to be focused at different distances from the lens. A rainbow effect can be seen as color fringes or halos along edges and around every point in the image.
Chromaticity:	Color quality of the light defined by hue and saturation. Chromaticity defines all the qualities of color except the brightness.
Chrominance:	A color term defining the hue and saturation of a color. The other component, luminance can be thought of as the portion of the image absent of color or monochrome.
Chrominance Signal:	That portion of the NTSC color television signal which contains the color information.
CMOS (Complementary Metal Oxide Semiconductor):	CMOS process is used extensively in the semiconductor business. CMOS wide variety of macro cells and architecture advantages afford high speed sensors with XY addressability as well as a high level of integration of features. CMOS has become the most widely used imaging technology due to the “Camera-On-Chip.
C-mount:	Standard lens mount found on many industrial and scientific cameras. The thread of the lens and lens mount is 1 inch in diameter with 32 threads per inch pitch and with a back focal length of 17.52 mm or 0.684 inch.
Color Encoding:	A method to create color RGB images from a single sensor having what is called a color filter array (CFA). The most common color algorithm is the Bayer CFA.
Color Fringing:	A CCD artifact caused when color filtering arrays or patterns conflict with information in a scene or image scanned or digitally photographed. It appears as magenta and green bands at contrast boundaries. Color fringing is always more apparent on the edge of the image than the center due to the lens curvature. It becomes the worst at the image corners.
Color Saturation:	In color theory, saturation refers to the intensity of a specific hue. It is based on the color's purity; a highly saturated hue has a vivid, intense color, while a less saturated hue appears more muted and grey. With no saturation at all, the hue becomes a shade of grey. Saturation is one of three coordinates in the HSV color space.
Composite Video Signal:	Composite video is the format of an analog television signal before it is modulated onto an RF carrier. It is usually in a standard format such as NTSC, PAL or SECAM. It is a composite of three source signals called Y, U and V (together referred to as YUV) with sync pulses. Y represents the brightness or luminance of the picture and includes synchronizing pulses, so that by itself it could be displayed as a monochrome picture. U and V between them carry the color information.
Contrast:	in an image or scene, the amount of difference between the lightest and darkest areas.
Contrast enhancement:	The enhancement of contrast by using an image histogram and lookup table to boost the contrast ratio.
Contrast range:	The range of gray between the lightest and darkest parts of an image; expressed as a ratio of light to dark.
Cooled CCD:	A CCD sensor that operates at temperatures below ambient to reduce dark current. Cooling is usually done with Peltier coolers or liquid coolers.
D/A converter:	An electronic device that transforms a signal sample from a digital form to an analog form. The digital form is usually a set of 8 or more binary bits which produces an analog signal of 2^n bit levels.
Dark current:	Is also know as Black Noise, is the signal charge the pixel develops in the absence of light. This charge is temperature sensitive, and normal in electrical image sensing devices.
Dark Current Uniformity:	Represents the variation of dark current from pixel to pixel. It is calculated as the rms. deviation from the average dark current for a fully vertically binned CCD.
Dark noise:	Dark current and any other noise accumulated in the absence of light.
Depth of field (DOF):	The amount of distance between the nearest and farthest objects that appear in acceptably sharp focus in an image. Depth of field depends on the size of the aperture, the distance of the camera from the subject, and the focal length of the lens. The bigger the aperture, the greater the depth of field
Depth of focus:	The Depth of focus depends upon the numerical aperture (NA) as well as the magnification and is inversely proportional to both. The higher the magnification the shorter the depth of focus for any given numerical aperture. Also known as depth of field.
Digital Camera:	A camera equipped with an electronic photosensitive sensor. The digital pictures are stored directly in the camera's memory and can be used immediately on a computer.
Digital number (DN):	A Value assigned to a pixel in a digital image. Also called counts.
Digital signal:	A signal in which information is carried in a limited number of different discrete states. The most fundamental and widely used form of digital signals are binary signals, in which one amplitude condition represents a binary digit 1, and another amplitude condition represents a binary digit 0. Digital-to-analog converter - See D/A converter.
Digitize:	To convert an image or signal into binary code. Visual images are digitized by scanning them and assigning a binary code to the resulting vector or raster graphics data.
Dynamic range:	refers to the varying gray values, or the spread of gray values, in an image that are possible reproduction. Am image with a high dynamic range suggests a wide number of gray levels and is normally associated with good contrast levels.
Exposure:	Exposure is the total amount of light allowed to fall on electronic sensor during the process of taking an image. Exposure is measured in exposure value (ev), with higher values denoting more light.
Exposure Time:	The time during which the sensor is exposed. In the case of a sensor with an electronic shutter, the shutter speed is the time for which the shutter is held open during the taking of an image and this may be shorter time than the actual frame period.
EXTSYNC:	The external synchronization signal used to align a camera’s timing to an external signal. The variable frequency signal EXTSYNC when used to trigger a line or frame transfer from the sensor to the readout registers. In this way the camera frame rate can be controlled externally.
Fiber Optics:	An optical fiber is a transparent thin fiber, usually made of glass, for transmitting light. Fiber optics is the branch of science and engineering concerned with optical fibers.
Field of View (FOV):	The amount of the scene visible to the camera, defined as the camera's aperture divided by its focal length. Wide-angle lenses have a large field of view, while telephoto has a small field of view.
Fill factor:	The ratio of the light sensitive area to the pixels total size. If a pixel size is 17 microns and has a fill factor of 60%, this means the photo sensitive area exposed to light is 10.2 microns. The 40% area not sensitive to light has metal interconnect or other structures within the pixel design that obscures light. The fill factor can be further defined in terms of X & Y fill factor.
Fixed Pattern Noise (FPN):	Unwanted signal component that is usually constant or very slowly changing with time, but might vary spatially and so could potentially be confused with true fringes. Examples of fixed pattern noise are the pixel to pixel gain variations or cosmetic defects in CCD or CMOS sensors, or parasitic interference caused by unwanted reflections from various air/glass surfaces (i.e. glass lid on the sensor).
Flat Field Correction (FFC):	Flat Field Correction applies a gain and offset correction per pixel to correct for illumination and sensor irregularities.
F-mount:	Standard lens mount found on many scientific cameras. The thread of the lens and lens mount is 2.5 mm in diameter with a back focal length of 46.5 mm. Also know as a bayonet mount. F-mount lens are preferred lens type when the diagonal of the sensor exceeds 11 mm. Most f-mount lenses have a much larger areas where the lens is constrained to be flat as possible. In the case of an f-mount, this area is 35 mm.
Focal Length:	The distance between the focal plane on the sensor and the focal point (optical centre of the lens) when the lens is focused at infinity. The focal length of the lens is marked in millimeters on the lens mount. The principal focal point is the position of best focus for infinity.
Focal Plane:	The plane on which the image of a subject is brought to focus behind the lens. To produce a sharp picture, the lens must be focused so that this place coincides with the plane on which the image sensor sits. This point should be at the actual surface of the sensor and not the glass lid covering the sensor.
Focus:	The focus, or focal point, of a lens is the point onto which collimated light parallel to the axis is focused. Although the focus is conceptually a point, physically, the focus has a spatial extent, called the Airy disc, or blur circle, due to the width of the aperture of the imaging optics.
Foot Candle (ft):	A measurement of luminance, or illumination, expressed in lumens per square foot. It is the amount of illumination from 1 international candle (the candela) falling on a 1-ft. surface at a distance of 1 foot. In SI units, 1 fc = 10.764 lux (1x
FPS:	Frames per second.
Frame:	A two-dimensional array of pixels or pixel information or a complete read-out of all pixels from a camera.
Frame buffer:	In An area of RAM used to store the pixel data for a single screen image, or frame.
Frame grabber:	A board, PCI or PCI-x, which interfaces between a camera and computer. The frame grabber provides the buffering and control for the camera.
Frame Rate:	The speed at which images are captured by an imaging system is called the frame rate and is expressed as number of frames per second (FPS).
Frame transfer:	A type of sensor architecture that has a light sensitive area for the sensor and a non-light sensitive area that is used for frame storage. An image is transferred from the light sensitive are to the shielded, non-light sensitive area. The transfer happens very fast either in CCD shift registers or an interline design.
Frequency:	The number of times per second a repetitive signal undergoes a full cycle of vibration. Frequency units are hertz (Hz). Image sensors are sometimes described in terms of their resolving capability or spatial frequency. Spatial frequency measured in either a MTF (analog) or CTF (digital) test, is the number of cycles of image brightness variation along a scan direction, generally expressed in lines per millimeter or line pairs per millimeter.
Front Porch:	The portion of a composite picture signal which lies between the leading edge of the horizontal blanking pulse and the leading edge of the corresponding sync pulse. This portion of the video signal is called a front porch because it has a similar shape to a porch on a house.
F-stop:	Also called a lens F Number or the speed of a lens. An f-stop is a designation to indicate a camera’s aperture opening. Each f-stop lets in twice as much light as the f-stop before it, and half as much light as the f-stop after it. Over a 5 f-stop range, the power is adjustable from full down to 1/32 of the total power. The f-stop is the numerical indication of how large a lens opening (aperture) is. The larger the f-stop number, the smaller the opening; for example, f/16 represents a smaller aperture than f/2. Some common f-stops on 35mm cameras are f2, f2.8, f4, f5.6, f8, f11, f16. Smaller openings (like f16) have greater depth of field.
F-stop ratio:	This number is the ratio that describes the focal distance, as determined by the diameter of the lens aperture. So the greater the aperture the lower the f-stop value; the more light strikes the sensor, the greater the sensitivity.
Full-frame:	A sensor architecture that has 100% fill-factor where the pixel is also used as the charge transport for moving an image out of the sensor. There is no electronic shuttering with full frame however; most full frame cameras use a mechanical shutter to provide stopping power. CCDs that are full frame are used in scientific applications. One advantage of a full frame is that it has no aliasing.
Full-well capacity:	Number of electrons (e-) that can be held in one potential well. High speed sensors typically have about 60,000 e- for full well where scientific sensors may have as much as 200,000 e-.
Gain:	In electronics, gain is usually taken to meaning the ratio of the signal output of a system to the signal input of the system. A gain of 10 would imply that a property of the signal (usually voltage or power) had increased by a factor of 10. In digital cameras, system gain defines the relationship between the number of electrons acquired as an input signal to the conversion/amplification of a video signal on the output.
Gamma:	Curve that describes how the middle tones of images appear. Gamma is a nonlinear function often confused with "brightness" and/or "contrast." Changing the value of the gamma affects middle tones while leaving the white and black of the image unaltered. The characteristics of displays using phosphors (as well as some cameras) are nonlinear. A small change in voltage when the voltage level is low produces a change in the output display brightness level; but this same small change in voltage at a high voltage level will not produce the same magnitude of change in the brightness output. This effect, or actually the difference between what you should have and what you actually measured, is known as gamma. The compensation is often referred to as the inverse of the classical bathtub curve.
Gamma Correction:	A nonlinear correction factor which is supposed to convert an evenly-spaced grayscale palette to evenly-spaced levels of brightness in the monitor (as measured by a photometer). It is usually in the form of a table representing the function where gamma is usually 1.7-2.2.
Gray level:	The brightness of a pixel. The value associated with a pixel representing it's lightness from black to white. Usually defined as a value from 0 to 255, with 0 being black and 255 being white.
Gray scale:	The spectrum, or range, of shades of black an image has. The gray scale range of a sensor is determined by the number of gray shades, or steps, they can recognize and reproduce. A camera that can only see a gray scale of 256 will not produce as accurate an image as one that distinguishes a gray scale of 512 or 1024. A gray scale of 256 steps is an 8-bit scale. A gray scale of 512 steps is a 9-bit scale. A gray scale of 1024 steps is a 10-bit scale. A gray scale of 4096 steps is a 12-bit scale.
High-speed framing:	The delineation between normal imaging frame rates and high speed frame rates has been widely accepted as 200 fps. Below 200 fps normally is not considered high speed imaging. Arguably, some may say anything above 100 fps would be considered high speed.
Host computer:	The primary or controlling computer for a digital camera.
Hue:	Corresponds to colors such as red, blue, green, etc.
Hz (hertz):	Cycles per second. MHz (megahertz) is a million cycles per second.
IC:	Integrated circuit.
Illuminance:	A photometric term that quantifies light incident on a surface or plane. Illuminance is commonly called light level. It is expressed as lumens per square foot (foot-candles), or lumens per square meter (lux).
Image:	A graphic representation or description of a scene, typically produced by an optical or electronic device. Common examples include remotely sensed data (e.g., satellite data), scanned data, and photographs. An image is stored as a raster data set of binary or integer values that represent the intensity of reflected light, heat, or other range of values on the electromagnetic spectrum.
Image analysis:	The Image analysis is the extraction of useful information from images; mainly from digital images by means of digital image processing techniques. Image analysis tasks can be as simple as reading bar coded tags or as sophisticated as identifying a person by its face.
Image array:	Often used to describe an imaging sensor as an array of pixels.
Image averaging:	A signal processing technique used to reduce random noise by averaging (n) number of digital images.
Image convolution:	A technique used in signal processing of an image where the substitution of the gray value of each pixel with another gray value that takes into account the gray values of the neighboring pixels. The convolution mask, or kernel, used to calculate the influence of the neighbors, determines the degree to which the image is sharpened or smoothed by the convolution process.
Image enhancement:	A signal processing technique to sharpen or improve the image.
Image intensifiers:	A light-in, light-out vacuum-tube device capable of amplifying low-light images. The tube consists of a photocathode on the input and a phosphor on the output, and sometimes a microchannel plate for increasing the light amplification (gain characteristics). Two types commonly used in industrial and scientific applications are the inverter and proximity focused units. The inverter type electrostatically focuses and inverts the image inside the tube. The proximity focused type has all of the elements closely spaced, has no need for focus electrodes, and is much more compact. An intensifier produces a monochromatic image at its output.
Image processing:	Generally refers to digital or analog enhancement and geometric modification of an image. Image analysis, which emphasizes the measurement of image parameters, is not to be confused with image processing.
Image segmentation:	In digital image processing, the partitioning of the image into non-overlapping regions according to gray level, texture, and so forth.
Infrared:	Lying outside the visible spectrum at the far end of visible light (above 760 nm).
Integration:	The process of accumulating signal or charge in a pixel. Also refers to the interfacing on the system level of electronic components.
Integration Time:	The time during which a pixel is being exposed to light. If there is an electronic shutter, the integration time is the shutter time. If there is no shutter, the integration time is approximately 1/frame rate. There is some overhead associated with reading the signal out of the pixel which must be subtracted from the integration time to be correct for 1/frame rate.
Interface:	Hardware and/or software required to connect peripheral to a camera, connect a computer system to a camera or to provide a user's access to a camera system; point at which any two parts of system connect.
Interlaced:	A system of video scanning where odd- and even-numbered lines of a TV picture are transmitted consecutively as two separate interleaved fields. Interlace is a form of compression and has been used for decades in analog (NTSC) TV.
Interline mask:	An interline CCD has metal interconnects that are opaque layered on top of a CCD register (vertical).
Iris:	An adjustable aperture built into a camera lens to permit control of the amount of light passing through the lens.
ITO:	Indium tin oxide. A material used in CCD gates to provide higher quantum efficiency.
Lens:	A true “lens” is a single piece of glass (or other transparent substance) having one or more curved surfaces used in changing the convergence of light rays. What we commonly call a photographic lens is more accurately and technically called an “objective,” an optical device containing a combination of lenses that receive light rays from an object and form an image on the focal plane.
Lumen:	A unit of luminous flux, equal to the flux through a unit solid angle (steradian) from a uniform point source of 1 cd or 1 FC (foot candle) per sq. foot.
Lumigen:	A fluorescent coating applied to a CCD to enhance the blue (UV) response.
Luminance:	This term is used to describe the specific light which comes off the surface whether off a filament, light bulb, lens, louver, tabletop, etc. Luminance varies with both the direction at which you view the surface and its gloss characteristics. Luminance is measured in candela per square foot. The black and white (Y) portion of a composite, Y/C, or Y/Pb/Pr video signal. The luminance channel carries the detail of a video signal. The color channel is laid on top of the luminance signal when creating a picture. Having a separate luminance channel ensures compatibility with black-and-white televisions.
Lux:	The amount of visual light measured in metric units at the surface that the light is luminating. One lux equals one lumen per square meter. One foot-candle equals 10.764 lux.
Magnification:	Relationship of the length of a line in the object plane to the length of the same line in the focal plane. It may be expressed as image magnification (image size/object size).
Mask:	In electronic imaging this refers to the lithography process used to produce an imaging sensor. To make an imaging sensor requires many masks that represent each layer of the architecture.
Moiré:	An undesirable optical effect created by overlapping grids and lines due to under sampling of the image data.
Monitor:	A device that converts the video signal from a camera, VTR, computer, etc. into an image that is displayed on its cathode-ray tube, LCD or some other display technology.
Monochrome:	Black and white with all shades of gray.
Noise:	Unwanted electronic or optical signals that cause interference in the reproduction of data or an image. Typical noise sources in electronic imaging include but not limited to KTC noise, column noise, fixed pattern noise, random noise and so forth.
Nyquist:	A sampling theorem for discrete signal processing where the original image can be reconstructed without distortion if it is sampled at a spatial frequency (2f) at least twice that of the maximum base frequency (f).
Offset:	In reference to electronic imaging is a method to correct for fixed pattern noise and to assure that reference levels are correct. Specifically, a black level offset correction removes the fixed pattern noise and normalizes the signal for the A/D converter to have full range on the remaining signal level.
Optical coupling:	In electronic imaging this refers to a lens element that couples between two optical devices (I.e. intensifier and a camera). Typically, 80% of the light transmitted through a lens coupler is lost and typical reduces a camera’s sensitivity at least one f-stop.
Optical noise:	Any noise that can be traced to optical components. Examples of optical noise are where the reflection of incident light on a sensor surface (mirror like) is reflected on the backside of the sensor glass lid and alias to adjoining pixel site. Other examples are the spread spectrum effect of IR exposing multiple pixels through the multi-path of the light.
Output amplifier:	In sensor technology, the output amplifier is the last structure before reaching he bonding pads. The driver must be efficient and capable of driving a high capacitive load. Many output amplifiers have multiple stages to increase the drive capability without raising the read noise in the output.
Phosphor:	A material that emits light when struck by electrons. Phosphor decay time for emitting light varies depending on the material. A fast decaying phosphor has a larger grain structure which means the resolution capability of the phosphor is reduced.
Photometric units:	The units (i.e. m, lx, cd/m, etc.) that are used to measure the amount of light (illuminance) or the brightness of an object or image (luminance), taking into account the sensitometric characteristics (wavelength-dependent response) of the human eye. Contrasts with radiometric units (for example, W/m), which measure light in terms of the physical energy independent of the sensitometric characteristics of the eye.
Photon:	A quantum (energy packet) of electromagnetic radiation; the elementary particle of photon radiation therapy. X rays and gamma rays are photon radiation.
Photon (shot) noise:	Shot noise consists of random fluctuations of the electric current in an electrical conductor, which is caused by the fact that the current is carried by discrete charges (electrons). The strength of this noise increases for growing magnitude of the average current flowing through the conductor. Shot noise is to be distinguished from current fluctuations in equilibrium, which happen without any applied voltage and without any average current flowing
Photon-limited operation:	A camera that is photon-limited, also known as quantum limited, is one where the electronic noise is less that the inherent noise generated by the sensor.
Picture:	A visual representation or image of something.
Pixel:	Picture element; a single dot and smallest element in a visual display.
Preamplifier noise:	Unwanted noise that is generated by the on-chip output amplifier.
Primary Colors:	Three colors wherein no mixture of any two can produce the third. For electronic imaging these are the additive primary colors red, blue and green.
Progressive Scan:	The progressive scan is a format for reading an image in sequential order, line by line.
Quantum efficiency:	Quantum efficiency (QE) is a figure given for a photosensitive device (charge-coupled device (CCD), for example) which is the percentage of photons hitting the photo reactive surface that will produce an electron-hole pair. It is an accurate measurement of the device's sensitivity.
Readout:	For electronic imaging the term refers to process of extracting the image, pixel by pixel from the sensor.
Region:	Refers to an area that is user-defined, typical a rectangular area on the sensor that is exposed and processed as an image.
Region of interest (ROI):	User-defined resolution, a rectangular exposure area on the sensor.
Resolution:	A measure of the ability to resolve an edge on an object.
Responsivity:	Similar to sensitivity this is a term for describing the rating of the output current from a camera sensor divided by the incident flux of light, usually expressed in signal current per watt of input radiation at a specific wavelength.
ROI:	Region of interest.
Saturation:	In color, the degree to which a color is diluted with white light or is pure. The vividness of a color, described by such terms as bright, deep, pastel, pale, etc. Saturation is directly related to the amplitude of the chrominance signal.
Sensitivity:	Similar to responsivity of a camera sensor but numerically different. It is the signal current per unit of illuminance on the faceplate in lumens. It is expressed in amps/lumen. Unless otherwise specified, the radiation is understood to be that of an unfiltered incandescent source at 2,856 degrees K.
Shutter:	A digital camera usually has an electronic shutter. Most sensors have an electronic shutter but some full frame designs use a mechanical; shutter.
Signal-to-noise ratio (SNR):	The measure of the signal quality at a given pixel. It is the ratio of the measured signal to the overall noise at that pixel.
SNR:	Signal-to-noise ratio.
Spike:	In electronics, a sharp brief voltage pulse. Powerful RF spikes that can damage video equipment and computers are generated when mercury or xenon arc lamps are started. To a limited extent, spikes entering through the power line (but not those rated as RF) can be suppressed with spike arrestors (transient suppressors).
Sync:	Term meaning the same as "synchronous" or "synchronize".
Sync Signal:	The signal employed used to synchronize a camera to another event.
Synchronizing:	Maintaining two or more cameras processes in phase.
System noise:	Undesirable signals generated by electronic circuitry. System noise includes photon noise, preamplifier noise, and dark current noise.
TDI:	Time-delay integration.
Thermoelectric cooling:	In electronic imaging, the process of pulling heat away from a sensor by using Peltier cooling devices.
Thinning:	Process that uses acid etching to uniformly reduce the size of CCDs to approximately 10 µm so that an image can be focused on the backside of its parallel register (where there is no gate structure). Thinned CCDs exhibit a high sensitivity to photons ranging from the soft x-ray to the near-infrared regions of the spectrum.
Time-delay integration (TDI):	A sensor architecture that provides an integration and readout mode that allows the acquisition of long scans of a moving image.
Trigger:	Signal (TTL or switch closure) that is transmitted to synchronize two or more cameras.
UV:	The range of radiation wavelengths from about 4000 angstroms (just beyond the violet in the visible spectrum) to about 40 angstroms (on the border of the x-ray region).
Video camera:	Camera that produces either analog video (NTSC, PAL or SECAM) or digital video (DV).
Voltage:	Electric potential or potential difference expressed in volts.
Wavelength:	In a periodic wave, the distance between two points of corresponding phase in consecutive cycles.
Well Capacity:	The total number of electrons a pixel can hold before blooming or reaching the saturation level.
X-ray:	High-energy photon with a wavelength in the approximate range from 0.05 angstroms to 100 angstroms.