Glossary
GUPPY Technical Manual
V4.0.1
214
Blooming
A pixel on a digital camera sensor collects photons which are converted
into an electrical charge by its photo diode. Once the full well capacity of
the pixel is full, the charge caused by additional photons will overflow and
have no effect on the pixel value, resulting in a clipped or overexposed
pixel value. Blooming occurs when this charge flows over to surrounding
pixels, brightening or overexposing them in the process. As a result detail
is lost. Blooming can also increase the visibility of purple fringing.
BMP bitmap
The BMP (bit mapped) format is used internally in the Microsoft Windows
operating system to handle graphics images. These files are typically not
compressed resulting in large files. The main advantage of BMP files is
their wide acceptance and use in Windows programs. Their large size makes
them unsuitable for file transfer. Desktop backgrounds and images from
scanners are usually stored in BMP files.
CCD
c
harge-
c
oupled
d
evice
CCD readout
CCDs are analog devices. In order to obtain a digital signal that is appro-
priate for doing quantitative analysis, it is necessary to convert the analog
signal to a digital format. When light is gathered on a CCD and is ready to
be read out, a series of serial shifts and parallel shifts occurs. First, the
rows are shifted in the serial direction towards the serial register. Once in
the serial register, the data is shifted in the parallel direction out of the
serial register, into the output node, and then into the A/D converter
where the analog data is converted into a digital signal.
CDS
CDS =
c
orrelated
d
ouble
s
ampling
Charge-coupled
device
A charge-coupled device (CCD) is a sensor for recording images, consisting
of an integrated circuit containing an array of linked, or coupled, capaci-
tors. Under the control of an external circuit, each capacitor can transfer
its electric charge to one or other of its neighbors. CCDs are used in digital
cameras and are manufactured in a wide variety of formats, architectures,
and grades.