Glossary

NI Vision Acquisition Express VI

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Glossary

A
array Ordered, indexed set of data elements of the same type.
aspect ratio The ratio of a picture or image's width to its height.
asynchronous (1) Independent in time from any other event. (2) Communication mechanism on the IEEE 1394 bus, which guarantees delivery of the message but does not guarantee timing.

B

Bayer encoding Method to produce color images with a single imaging sensor, as opposed to three individual sensors for the red, green, and blue components of light.
Bayer pattern Color filter array pattern that can appear in four variations, depending on the current left and top offsets of the acquisition window:
GBGB
RGRG		 GRGR
BGBG		 BGBG
GRGR		 RGRG
GBGB
buffer Temporary storage for acquired data.

D

default setting A default parameter value recorded in the driver; in many cases, the default input of a control is a certain value (often 0) that means use the current default setting.

E

external trigger A voltage pulse from an external source that triggers an event such as A/D conversion.

F

frame A complete image; in interlaced formats, a frame is composed of two fields.

G

gain Applied value to compensate for discrepancies in the filter for a particular color.
Gigabit Ethernet Describes technologies which transmit Ethernet packets at a rate of a gigabit per second.
GigE Vision A camera interface standard developed using the Gigabit Ethernet communication protocol.
grab Performs an acquisition that loops continually on one buffer. You obtain a copy of the acquisition buffer by grabbing a copy to a separate buffer that can be used for analysis.
GUI Graphical user interface. An intuitive, easy-to-use means of communicating information to and from a computer program by means of graphical screen displays; GUIs can resemble the front panels of instruments or other objects associated with a computer program.

I

I/O Input/output. The transfer of data to/from a computer system involving communications channels, operator interface devices, or data acquisition and control interfaces.
IEEE Institute of Electrical and Electronics Engineers.
ISO Trigger A high voltage isolated trigger.

L

LUT Lookup table. A selection in Measurement & Automation Explorer (MAX) for Vision that contains formulas that let you implement simple imaging operations such as contrast enhancement, data inversion, gamma manipulation, or other nonlinear transfer functions.

M

MAX Measurement & Automation Explorer. The National Instruments Windows-based graphical configuration utility you can use to configure NI software and hardware, execute system diagnostics, add new channels and interfaces, and view the devices and instruments you have connected to your computer. MAX is installed on the desktop during the National Instruments driver software installation.
memory buffer See buffer.
memory window Continuous blocks of memory that can be accessed quickly by changing addresses on the local processor.

N

NI-IMAQ Driver software for National Instruments image acquisition hardware.
NI-IMAQdx National Instruments driver software for IEEE 1394 and GigE Vision cameras.

O

one-shot Applies to pulse generation and acquisitions. A one-shot pulse or acquisition happens only once.

P

PCI Peripheral Component Interconnect. A high-performance expansion bus architecture originally developed by Intel to replace ISA and EISA; it is achieving widespread acceptance as a standard for PCs and workstations and offers a theoretical maximum transfer rate of 133 Mbytes/s.
PCIe PCI Express. A high-performance expansion bus architecture originally developed by Intel to replace PCI. PCIe offers a theoretical maximum transfer rate that is dependent upon lane width. A x1 link theoretically provides 250 MB/s in each direction—to and from the device. Once overhead is accounted for, a x1 link can provide approximately 200 MB/s of input capability and 200 MB/s of output capability. Increasing the number of lanes in a link increases maximum throughput by approximately the same factor.
PCLK Pixel clock signal. Times the sampling of pixels on a video line.
pixel Picture element. The smallest division that makes up the video scan line; for display on a computer monitor, a pixel's optimum dimension is square (aspect ratio of 1:1, or the width equal to the height).
pixel aspect ratio The ratio between the physical horizontal size and the vertical size of the region covered by the pixel. An acquired pixel should optimally be square, thus the optimal value is 1.0; however, typically it falls between 0.95 and 1.05, depending on camera quality.
pixel clock Divides the incoming horizontal video line into pixels.
pixel count The total number of pixels between two horizontal sync signals; the pixel count determines the frequency of the pixel clock.

Q

quadrature encoder An encoding technique for a rotating device where two tracks of information are placed on the device, with the signals on the tracks offset by 90 degrees from each other. The phase difference indicates the position and direction of rotation.

R

real time A property of an event or system in which data is processed as it is acquired instead of being accumulated and processed at a later time.
resolution The smallest signal increment that can be detected by a measurement system; resolution can be expressed in bits, in proportions, or in percent of full scale. For example, a system has 12-bit resolution, one part in 4,096 resolution, and 0.0244 percent of full scale.
RGB Red, green, and blue. The three primary colors used to represent a color picture. An RGB camera is a camera that delivers three signals, one for each primary.
ring Performs an acquisition that loops continually on a specified number of buffers.
ROI Region of interest. (1) An area of the image that is graphically selected from a window displaying the image. This area can be used focus further processing; (2) A hardware-programmable rectangular portion of the acquisition window.
RTSI bus Real-Time System Integration Bus. The National Instruments timing bus that connects image acquisition and DAQ devices directly, by means of connectors on top of the devices, for precise synchronization of functions.

S

saturation The richness of a color. A saturation of zero corresponds to no color, that is, a gray pixel. Pink is a red with low saturation.
sequence Performs an acquisition that acquires a specified number of buffers, then stops.
snap Acquires a single frame or field to a buffer.
sync Tells the display where to put a video picture; the horizontal sync indicates the picture's left-to-right placement and the vertical sync indicates top-to-bottom placement.

T

timeout Length of time, in milliseconds, that the driver waits for an image from the camera before returning an error
transfer rate The rate, measured in bytes/s, at which data is moved from source to destination after software initialization and setup operations; the maximum rate at which the hardware can operate.
trigger Any event that causes or starts some form of data capture.
trigger control and mapping circuitry Circuitry that routes, monitors, and drives the external and RTSI bus trigger lines; you can configure each of these lines to start or stop acquisition on a rising or falling edge.
TTL Transistor-transistor logic. A digital circuit composed of bipolar transistors wired in a certain manner. A typical medium-speed digital technology. Nominal TTL logic levels are 0 and 5 V.

U

user buffer Memory buffer created by the user as a destination for the image. In LabVIEW, this is created with the IMAQ Create VI.

V

VI Virtual Instrument.
  1. A combination of hardware and/or software elements, typically used with a PC, that has the functionality of a classic stand-alone instrument
  2. A LabVIEW software module (VI), which consists of a front panel user interface and a block diagram program.
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