Glossary of Imaging Terms
8-bit grayscale: Images that contain 256 possible shades of gray.
24-bit color: 24-bit color images are composed of (3) 8-bit color channels. Each color channel, similar to an 8-bit grayscale image, contains up to 256 colors. When combined, the red, green and blue channels provide up to 16.7 million colors. 24-bit color is also known as True Color and Photo-realistic Color.
32-bit color: 32-bit color images have 4 color channels of 8 bits each - one channel each for red, green and blue, plus 8 bits of grayscale data to provide higher detail.
Alpha Channel: An 8-bit channel reserved by some image-processing applications for masking or additional color information.
Alphanumeric: Set of characters composed of letters and numbers; may include punctuation marks or other symbols; excludes printer control characters such as Carriage Return and flow control characters such as XOM and XOFF.
ADF: Automatic Document Feeder. A device that holds pages and feeds them one after another into a scanner.
Batch Scanning: Sequential scanning of multiple originals using previously-defined, unique settings for each.
Bitonal: An image or file comprised of pixel or dot values of either black or white.
CCD: A charge-coupled device, or CCD, is a light sensitive electronic device that converts light into an electrical charge.
Color Correction: The process of adjusting an image to compensate for scanner deficiencies or for the characteristics of the output device.
Color Dropout: Color dropout is a feature that is used to ignore specific colored ink(s) from preprinted forms/documents during the scanning process. This can be used to remove colored backgrounds or colored text templates in the scanned image. Depending on the model, Fujitsu scanners are capable of dropping out colors in the red, green or blue color spectrum.
Data rate: The speed of a data communications channel, measured in bits per second.
Long Document Scanning: Long document scanning functionality is used to process longer than normal paper sizes. Long documents can be in the form of loan documents, medical equipment logs, and similar documents.
Double Feed: The feeding of two sheets of paper at once. Sometimes on roller based scanners this can occur so cleanly that it cannot be detected.
dpi: Dots per inch. A measurement of scanner resolution. The number of pixels a scanner can physically distinguish in each vertical and horizontal inch of an original image. Documents are normally scanned at a resolution between 200 dpi and 400 dpi.
Duplex: The ability of a scanner to scan both sides of a sheet simultaneously. Requires two scanner cameras and often two processing boards.
FB: Flatbed. A scanner design in which the document is placed in the scanner's bed, either manually or by an automatic document feeder, and remains stationary during scanning. As a result, flatbed scanners provide a more stable target than other scanner designs, but they are generally slower.
Grayscale: (1) An image type consisting of shades of gray, with no color. The standard grayscale image contains 8 bits per pixel, which allows for 256 shades. (2) The depiction of gray tones between black and white. A grayscale monitor is able to display distinct gray pixels as well as black and white ones, but not color pixels. (3) An orderly variable progression in definite steps of gray densities ranging from minimum zero (white) to maximum density (black). A strip of standard gray tones placed at the side of the original copy during a photography to measure tonal range obtained. Used in processing film or materials such as photographic paper and plates.
Halftone: A simulation of continuous tones by the use of black or overlapping process color dots of varying size or position.
Host: computer in which an applications or database resides.
Hz: Abbreviation for Hertz; cycles per second. Often used with metric prefixes, as in kiloHertz (kHz).
Interface: 1. Mechanical or electrical link connecting two or more pieces of equipment together. 2.A point of demarcation between two devices where the electrical signals, connectors, timing and handshaking are defined.
Image compression boards: An imaging-dedicated processor(s). Relieves the CPU (Central Processor Unit-the computer's main chip) from many imaging-specific tasks - compression, decompression, display, zooming, shrinking, scale-to-gray. In fact, does them better than the CPU.
Mean Time Between Failure: A statistical measure of reliability, this is calculated to indicate the anticipated average time between failures of a device. The longer the better.
OCR: OCR or Optical Character Recognition is a software process where and image is converted to text data. Once the image is converted, the text can be edited by a word processing/spreadsheet application or the text data can be used as an index to perform full text searches and retrieval.
Pixel: The basic building block of all images -- a simple dot. In bitonal images, it is merely a black or white dot (see "Bitonal" definition above). In gray scale images, dots will have between 1-to-256 possible values of gray (for an 8-bit gray scale image).
Portrait Orientation: An image registered so that is is taller than it is wide, with the narrow edge running along top and bottom. When scanning, orientation is determined b the leading edge of the document.
ppm: Pages per minute. A measurement of the throughput speed of a scanner - how many letter-size pages the scanner can scan in one minute. Beware: ppm can be misleading.
Resolution: Indicates the number of dots, often measured in dpi, that make u an image on a screen or printer. The larger the number of dots, and thus the higher resolution, the finer and smoother images can appear when displayed at a given size. Low resolution caused jagged characters. The ideal resolution is a trade-off between quality and the overhead in storage power and processing strength required to use it.
SCSI: Small Computer System Interface. Pronounced "scuzzy". An Industrial standard (of sorts) for connecting peripheral devices and their controllers to a microprocessor. SCSI defines both hardware and software standards for communication between a host computer and a peripheral. Computers and peripheral devices designed to meet SCSI specifications should work together.
Simplex: A document scanner that copies single-sided documents.
Throughput: The actual amount of useful and non-redundant information which is transmitted or processed. The relationship of what when in one end and what came out the other is a measure of the efficiency of that communications link - a function of cleanliness, speed, etc.
Transport speed: The speed at which the mechanical transport runs, measured in inches/centimeters per second (ips/cps).
TWAIN and ISIS: TWAIN and ISIS are industry standard scanner drivers. They allow you to seamlessly connect your scanner to hundreds of scanning applications.
USB: USB, or Universal Serial Bus is a standard computer interface that is included with the majority of personal computers. The USB interface allows the user to connect external devices including scanners, digital cameras, printers, keyboards and mice to the PC. The current USB specification is 2.0. The 2.0 standard supports and is backwards compatible with the previous specification, 1.1. For more information to to http://www.usb.org.
VAR/VAD: Value Added Reseller/Dealer. VARs buy equipment from computer manufacturers, add some of their own software and possibly some peripheral hardware to it, then resell the system, with its newly added "value" to end users. A VAD is similar, but is generally less directly in touch with the end user.
Video Scanner Interface Board: An add-in board residing in the host computer which enables communications and control of the scanner device. The board provides device control and file or data compression. Also known as an accelerator or compression board.
The definitions in the glossary where prepared, in part, from Moore's Imaging Dictionary, published by Flatiron Publishing, Inc.