Glossary
GUPPY Technical Manual
V4.0.1
225
JPEG, JPG
The JPEG (
J
oint
P
hotographic
E
xperts
G
roup) image files are files in a lossy
format. The DOS filename extension is JPG, although other operating sys-
tems may use JPEG. Nearly all digital cameras have the option to save
images in JPEG format, some at different compression levels, such as fine
and standard. The JPEG format supports full color and produces relatively
small file sizes. Fortunately, the compression in most cases does not
detract noticeably from the image. But JPEG files do suffer generational
degradation when repeatedly edited and saved. Photographic images are
best stored in a lossless non-JPEG format if they will be re-edited in future,
or if the presence of small artifacts (blemishes), due to the nature of the
JPEG compression algorithm, is unacceptable. JPEG is also used as the
image compression algorithm in many Adobe PDF files.
Linux
Linux is an open source operating system within the Unix family. Because
of its robustness and availability, Linux has won popularity in the open
source community and among commercial application developers.
Little endian
Byte order: little units first (compare: big endian)
Lux
The
lux
(symbol: lx) is the SI unit of illuminance. It is used in photometry
as a measure of the intensity of light, with wavelengths weighted accord-
ing to the luminosity function, a standardized model of human brightness
perception. In English,
lux
is used in both singular and plural.
Machine vision
Machine vision is the application of cameras and computers to cause some
automated action based on images received by the camera(s) in a manu-
facturing process. Generally, the term
machine vision
applies specifically
to manufacturing applications and has an automated aspect related to the
vision sensors. However, it is common to use machine vision equipment
and algorithm outside of the manufacturing realm.
Megapixel
Megapixel refers to one million pixels - relating to the spatial resolution of
a camera. Any camera that is roughly 1000 x 1000 or higher resolution
would be called a megapixel camera.
Microlens
Microlens is a type of technology used in some interline transfer CCDs
whereby each pixel is covered by a small lens which channels light directly
into the sensitive portion of the CCD.
OCR
OCR =
O
ptical
C
haracter
R
ecognition
Offset
Offset is just the same as the brightness control on your TV. It is a positive
DC offset of the image signal. It is used primarily to set the level of black.
Generally speaking, for the best signal, the black level should be set so
that it is near zero (but not below zero) on the histogram. Increasing the
brightness beyond this point just lightens the image but without improv-
ing the image data.