|
A/D Conversion
Analog to digital conversion of a continuous electrical signal (e.g.
Video) to a set of discrete numeric values. Frame grabbers convert analog
video signals to digital images.
Accelerator Processor
A hardware processor in a digital image processing system that is
exclusively devoted to image processing tasks; typically based on a
dedicated microprocessor.
Active
Window
The image window that is currently selected. If only one image
window is open, it will be the active window. In multi-open image window
instances, the active window is always the front most window (non active Windows have gray title bars in Northern Eclipse© ).
Adaptive Thresholding
A method of binary contrast enhancement where the threshold value
changes throughout an image based on local brightness characteristics.
Additive Color
The form of color creation based on the additive mixing of the red,
green, and blue primary colors.
AGC
Automatic Gain Control. In video detectors an AGC is built in to
automatically adjust the dynamic range to varying lighting conditions. The
AGC should be turned off for
most computer imaging applications.
Airy Disk
Diffraction pattern created by an object under the microscope. Rings of bright/dark pattern may be
seen around small objects at high magnification. The Rayleigh Criterion is one way to describe the limit
of resolution of the microscope.
This criterion describes the amount of overlap of neighboring Airy
disks - when the two Airy disks merge the object can no longer be resolved.
Aliasing
The formation of objects, or "edges", within an image that
do not exist within the original sample. Caused by image sampling errors in digital systems.
Analog Image Processing
The technique of processing images while they are in the form of a
continuous electrical signal, typically a video signal.
Analog Signal Reconstruction
The recreation of a continuous analog electrical signal (typically a
video signal) from a series of discrete digital brightness values.
Analog-to-digital Converter (A/D)
A semi-conductor device that converts an analog voltage level (representing
image brightness) to a digital quantity.
Analogue-to-Digital (A/D) Converter
An electrical device used to covert analogue signals to digital
signals.
Angstrom (Å)
A unit of length 1/10th of a nanometer (10-10
meters).
Area
The selected area (selected region) is the area of an image in which
image processing is applied to or objects are counted and measured. Note
that the time required to complete these tasks is dependent on the size of
the area, the complexity of the selection and the number of Data Options
requested. To improve processing efficiency one should define the smallest
possible Data Setup Options and
use a single rectangular selection.
Area of Interest
"Area of Interest", also known as ROI (Region of Interest),
or selection. A connected subset of pixels defined within an image which
may be arranged in any shape using Northern Eclipse’s© tools for
drawing areas of interest within an image. They are used to segregate the
subset from the rest of the image.
Aspect Ratio
The ratio of an image's horizontal to vertical dimensions, generally
stated as x:y.
Background Subtraction
Due to non-uniformity in illumination, a process called background
subtraction is often used in image analysis to reduce these effects. This
can be performed in real time prior to image analysis on a real time frame
grabber, or after acquisition with a standard frame grabber. Background
Subtraction is possible in Northern Eclipse using the Looping function for
incoming digital or analog images or can be applied to static images using
Boolean Operations.
Bandwidth
Analog: Bandwidth is the range of frequencies transmitted from a
given signal. Digital: The total amount of Data transmittable within a
fixed time period.
Beam Splitter
A prism, or partial mirror, that diverts part or all of the light
from one direction to another.
A beam splitter is often used to divert some or all of the light
from the eyepieces to the camera.
Bilinear Interpolation
A form of pixel interpolation that is based on a weighted average of
the four pixels surrounding the pixel location of interest.
Binary Image
An image comprised of only black and white pixels.
Binary Morphological Process
The morphological process intended to operate on a binary image.
Neighborhood black and white pixel patterns are evaluated.
Binning
Binning can have a number of meanings in image analysis. In Northern
Eclipse© binning is
referred to as a method of including or excluding objects either by area,
perimeter, shape factor or any of a number of morphometric parameters.
Digital camera companies refer to binning as a method of joining
information from several pixels to a single pixel. Many of the high quality
digital cameras can do this joining of pixel information (binning) during
the image transfer to a computer. This form of binning allows greater
camera sensitivity at the expense of resolution.
Bit
This is the smallest unit in a binary number (binary digit), or the
smallest unit of digital information recognized by a computer and may take
the value of either zero or one ( TRUE or FALSE, ON or OFF, 0 or 1, BLACK
or WHITE, etc.). A pixel is represented by one or more computer bits. The
sum of bits per pixel directly determines the number of colors or gray
levels that can be represented. An 8-bit (1byte) image contains 28
or 256 gray levels, usually from zero (black) to 255 (white). Note: many image processing
programs consider zero = white and 256 = black.
Bit Depth
The number of gray levels that can be represented in each pixel of
an image (e.g. 8 bit = 256
gray levels, 10 bit = 1024 gray levels, 12 bit = 4096 gray levels, 16 bit =
65536 gray levels).
Bit Map
A 2D array used to depict an image. Each block in the array contains
a value that describes a sample of the image in terms of its color.
Bit Plane
The view of a single bit of an image. A bit plane represents the on or off level of a
particular bit's contribution to each pixel's brightness.
Bits per Pixel
The same as Bit Depth. Describes the "deepness" of an
image. Northern Eclipse© can use 8, 16, 24 or 48 Bits per Pixel.
Black Level
The amount of signal offset (alters the blackness level of the
image).
Black Level Reference
The reference used by an A/D converter to establish the amplitude of
a video signal to be converted to black (0).
BMP
Image bit-mapped format used by Windows and OS/2. This is a very
common image format and is universal to most windows imaging software.
Boundary Description
A description of an object's perimeter; typically a series of chain
codes or line segments having a length and direction.
Bright Field
Illumination of the specimen where the background appears
"bright". This is
the "normal" illumination method in microscopy. See also: dark field and epi-illumination.
Brightness
The quantity of light assigned to a pixel in a digital image. In comparison, intensity refers to
the quantity of light actually reflected or transmitted from a physical
scene. Also, one of the three
color components of the HSB color space that controls how bright an HSB
color appears.
Brightness Histogram
A graphical representation of the number of pixels in an image at
each gray level.
Brightness Slicing
A double binary contrast enhancement operation where pixel
brightnesses below a lower threshold and above an upper threshold are set
to black, while brightnesses between the two thresholds are set to white.
Burn In
Prolonged exposure to a bright scene may leave an after image on
certain video detectors or monitors. Also a term used to test a new computer.
Byte
A computer term for an information unit of 8 bits.
Calibration (Distance)
Redefinition of the distance scale associated with an image (i.e.
distance between pixels in a unit of measure other than pixels), (i.e.
using a calibration slide on a microscope and figuring out pixels per
micron). See Distance Calibration.
Calibration (Hardware)
Redefinition of Color Map characteristics to compensate for
variations in image quality due to hardware differences. Once the
calibrations have been determined they can be reused each time a particular
type of hardware is used again. You can correct the nonlinearities present
between different image acquisition systems as long as you have an image
with known intensities.
CCD
This is an abbreviation for Charge Coupled
Device. In Northern Eclipse© CCD is generally used in discussing video cameras that
use this device to detect images (i.e. CCD cameras).
CCD & CID
Types of electronic cameras using electronic chips as the
detector. CCD = charge-coupled
device, CID = charge-induced device.
Both cameras use a chip with a detector array which is
"read" by electronic circuitry.
CCIR (PAL)
European TV standard (756H x 581V pixels). Set by
the Comite Consultatif International des Radio Communication.
CCIR Monochrome
The European monochrome standard video format originally used by
commercial television broadcasters and still used in monochrome video
cameras.
CD "Burner"
A device for writing information to CD-ROM disks. The files can then be readily read
by a regular CD-ROM drive.
CD-ROM
A laser disk storage device (Compact Disk - Read Only Memory). Blank CD-ROM disks (which are very
cheap) can be loaded with computer files using a CD-ROM "burner". The disk can be written to many
times (multi-session), but the existing data cannot be erased. However, take care - the existing
data may be made "unreadable" if an error occurs during a
subsequent "bum" to the same multi-session disk. Currently CD-ROM disks can hold 650
Mbyte of data. The laser
"etching" method of writing to a disk results in a very stable
method of long term storage of valuable data.
CD-RW
Re-writable CD laser disk, having the same capacity as the CD-ROM
(650 Mbyte) but can be written/erased many times. The CD-RW disk can be read using the CD-ROM drive
present in most computers.
Center of Mass
The (x,y) balance point of an object where there is equal mass
above, below, left, and right. (center of gravity).
Centroid
The geometric center of an object. It is equivalent to the Center of
Mass. This is found by
calculating the average X (or horizontal) and Y (or vertical) coordinate
values for every pixel in a
given object .
Charge Coupled Device (CCD)
A semiconductor photodetector device used in most video cameras.
Closing
A binary or gray scale morphological operation composed of a
dilation operation followed by an erosion operation; small holes and gaps
are filled, while objects tend to remain their original size. See Binary
Operations.
C-mount
Standard screw-in lens mount for the attachment of a camera to a
microscope.
CMY
Cyan, Magenta, Yellow - 3 color subtractive color
representation most useful for image printing. Many dye sublimation
printers use CMY in their print process.
CMYK
Cyan, Magenta, Yellow, Black - 4 color process
with improved black and therefore better image contrast than CMY. Used in the printing industry for full-color
printing.
Collector Lens
A lens with a light source used to provide a suitably sized area of
illumination.
Color Compression
The compression of color images, typically first converting the
image to a less redundant color space such as hue, saturation, and
brightness.
Color
Correction
The changes made to a color image to improve the perceived
deficiencies in color, brightness and contrast. See Equalize.
Color Decoder
A circuit that breaks down a composite color video signal into a
component form for digitization, typically from NTSC or PAL to RGB.
Color Encoder
A circuit that combines the parts of a component color video signal
into a composite form for display, typically from RGB to NTSC or PAL.
Color Features
Features of an object that relate to its color characteristics, such
as hue and saturation.
Color Histogram
Generally three histograms - one for each color component -
representing the number of pixels in an image at each level.
Color Look Up Table (LUT)
See LUT and Color Maps.
Color Maps
Often referred to as a LUT (look up table). The digital image is comprised of
pixels, which have been assigned gray level values. These gray level values by default
are represented by entry 0 being black up through entry 255 being white.
Using a LUT other colors can be assigned to represent any or all of the
gray level entries. In Northern Eclipse© Color Maps have the
suffix (.map). See Apply Color Map.
Color Resolution
Like brightness resolution but applied to each color component. The
accuracy at which an image's pixels are quantized is measured in number of
bits or gray levels.
Color Saturation
Color saturation refers to the degree of color present (i.e.
intensity of color).
Color Space
A representation of color controlled by a number of color
components, such as RGB or HSV.
Also, the range of colors that can be created by mixing a set of
primary colors in differing proportions.
Color Temperature
A measure of the bluish (high temperature) or reddish (low
temperature) hue of the "white" light expressed as the absolute
temperature (degrees Kelvin).
This nomenclature is used to express both the sensitivity of an
electronic light detector and the color display of a computer monitor.
Composite Color
A video signal composed of a single physical signal, into which is
encoded both luminance and chrominance information.
Compression
Mathematical technique allowing images to be stored using less
space. In Northern Eclipse© the TGA image format does automatic
image compression and the JPEG plugin allows for user defined image
compression.
Contrast
Perceived as the sharpness of an image. High contrast images have a larger difference between
white and black or in the case of color images, the color range is
greater. As contrast is
increased the color (gray level) spreads out. In Northern Eclipse© viewing an image with the histogram tool and then applying the
proper equalization values will
show great improvements in image contrast.
Contrast (camera)
The
visibility of an object against the background. A low-contrast feature blends into the background, and a
high-contrast feature stands out distinctly. Contrast can be manipulated by altering the gain and
blackness level on a camera.
Contrast Enhancement
The enhancement of the brightness attributes of an image.
Contrast Stretch
A digital imaging function which stretches the collected image
between 0 (black) and 256 (white) to make maximum use of the available gray
scale range available (256 shades of gray in an 8-bit image and 0 to 65535
in a 16-bit image).
Control Points
Multiple points (fiducial markers) placed on an image to control a
warping transformation; the points represent the before and after
locations of the transformation. Also, points on drawn selected regions
that can be used to change the shape or size of a region.
Convolution
A
neighborhood arithmetic operation performed for each pixel in the
image. The size and numerical
coefficients for the neighborhood are defined by a kernel, which is passed
over the image one pixel at a time.
The coefficients are multiplied with the underlying gray levels and
added together, with the normalized result replacing the value of the pixel
at the origin (typically at the center of the neighborhood). Convolutions can be used for
sharpening, edge detection, smoothing, and object separation. See Convolution Filters.
Convolution Coefficient
One of several weights used in the weighted average computation of
the spatial convolution process.
Convolution Mask
The set of convolution coefficients used in the spatial convolution
process.
Cooled CCD
A CCD camera that operates below ambient temperature to reduce or
eliminate dark current "noise".
Current
Window
The
image window that is currently selected. If only one image window is open,
it will be the active window.
In multi-open image window instances, the currently active window is
always the front most window (non active Windows
have gray title bars in Northern Eclipse© ).
Cursor
The cursor, or pointer, is a symbol that represents where on the
screen the mouse is currently located. This symbol will change its shape when the system is in
different modes or when the
cursor is over different parts of the screen. Northern Eclipse© has many different cursor styles during various
operations.
Cyan, Magenta, and Yellow Color
Space (CMY)
A color representation used in the printing industry based on
subtracting the primary colors (red, green, and blue) from white - which is
the same as adding the secondary colors cyan, magenta, and yellow to black
- to create the desired color.
Dark Current
The background current produced by a photodetector. Cooling a CCD detector
significantly reduces the dark current "noise"(s).
Dark Field
Oblique illumination is used to produce a dark background with
reflective structures brightly lit against it. Useful for observing live unstained cells.
Decompression
The recreation of an original image from a compressed form of the
image.
Deconvolution
A mathematical process used to remove out-of-focus blur from
digitized optical sections. It is a restoration operation where a previous
optical or other process such as image blurring due to misfocus, is
reversed. Typically a stack of images is deconvolved. Northern Eclipse has
a deconvolution plugin for No Neighbour (2D), Nearest Neighbour, and Full
Iterative using the point spread function (PSF) method.
Depth of Field
The range of distances between imaged object and lens where the
object will appear in focus.
Depth of Focus
The range of distances between lens and photosensor where the imaged
object will appear in focus.
Device Driver
The lowest level of software in a digital image processing
system. A device driver interfaces
the function library to physical devices such as frame grabbers,
accelerator processors, and special purpose processors. Digital cameras
and framegrabbers require software device drivers.
Difference Image
The image resulting from the pixel-by-pixel subtraction of one image
from another.
Differencing
An operation that subtracts one image from another, pixel by
pixel. Typically, each image
is of the same scene but acquired at different times or under different
lighting conditions.
Digital
Digital
data can be handled without error; manipulation of analogue data (or
signals) and will always involve some finite degree of error, however
small.
Digital Camera
A camera with digitizing and computer interfacing circuitry. Since these cameras are designed to
be operated through a computer interface, images are transferred directly
to the computer. No frame grabber or external digitizing system is required. Northern Eclipse© supports a full line of digital
cameras.
Digital Image
An image composed of discrete pixels, each having an associated
brightness value.
Digital Image Processing
The technique of processing images while they are in the form of
discrete digital brightness quantities.
Digital to Analog Converter (D/A)
A semiconductor device that converts digital image brightness
quantities to analog voltage levels.
Digitization Sampling and
Quantizing
An analog video signal to create a digital image.
Dilate
Filter
Number
of Repetitions - Selects the number of iterations of dilation to carry out.
Dilation
A binary or gray scale morphological operation that increases the
size of bright objects uniformly in relation to the background; small holes
and gaps are filled. See Binary Operations.
Distance
This
measurement quantity is the straight-line distance between the two points
selected. If a spatial calibration has been made, the quantity is reported
in calibrated units.
DLL
Windows Dynamic Link Library.
A file that contains executable code, providing increased
functionality for the programs that use them.
Dot Pitch
The size of the color phosphor dots in a color cathode-ray tube.
DPI
Dots per Inch, a term common to printer manuals. The higher the DPI, the greater the
resolution.
DVD Disk
Very high capacity laser disk (10x the capacity of a CD-ROM). There are currently several formats
and standards for DVD disks.
Dye Saturation
Refers to the highest level of light that can be used to produce
fluorescence - further increase in the laser light will not increase the
level of fluorescence.
Dynamic Range
Range of values of a measured variable over which a system provides
accurate data (e.g. an 8 bit image has a dynamic range of 0 to 255, 16 bit
image has a dynamic range of 0 to 65,535).
Dynamic Range (or Bit Depth)
The number of different shades of gray between black and white that
are present in the image. An
8-bit image has 256 gray levels, a 12-bit image has 4096 gray levels and a
16-bit image has 65,536 gray levels.
Dynamic Range (or Brightness)
The brightness span of an image's gray scale.
Edge Enhancement
An algorithm for sharpening the edges on stored digital images.
Edge Enhancement Filter
A spatial filter that increases the edge detail in an image.
Edge Filter
Another term for a shortpass or longpass filter with a very sharp
cut-on or cut-off.
Empty Magnification
Greater magnification than the useful magnification. No useful information will be
obtained and sharpness and contrast will decrease.
Epi-fluorescence
Fluorescence technique where the excitation light passes through the
objective before reaching the specimen. It therefore also acts as a
condenser. Conventional
fluorescence microscopy on modem microscopes is normally performed with
epi-illumination.
Equalization
Use this command to re-map the currently active image’s histogram. For example an image that has a
gray level range of 10 to 50, (a very low contrast image), may be stretched
out from 0 to 255 (10 mapping to 0, ..., 50 mapping to 255). This operation will maximize the
contrast of an image. Note
that linear re-mapping of an image made by this command will irretrievably
alter the image.(NOT TO BE USED IN CONJUNCTION WITH DENSITOMETRY)
Erode Filter
Number of Erosions - Select the number of iterations of erosion to
carry out. Numbers larger than
1 are useful if you have an image that you are certain will require a large
amount of erosion.
Erosion
A binary or gray scale morphological operation that uniformly
reduces the size of bright objects in relation to the background; small
speckle and spurs are eliminated. See Binary Operations
Even Field
The even numbered lines in an interlaced scan video signal.
|