Spectral Instruments
Pt # 2500- 8
power supply and a re-circulating water-cooler are also provided. The preamplifier
and analog processing circuits as well as the clock drivers, temperature and pressure
measurement hardware and digital image output driver circuits are all located inside
the electronics module.
The camera system is “self-aware” – that is, the camera knows, and reports to the
application software, all the information required to properly operate the camera
regardless of the type of CCD or the number of ports.
1.1.1 SICCD - The Important Distinction
Spectral Instruments manufactures precision digital imaging systems utilizing
scientific-grade CCDs. Innovative and detailed mechanical and electronic design
coupled with careful component specification and system manufacture provides
the ultimate in stable, high dynamic range digital imaging. Spectral Instruments
has invented the term Scientific Imaging CCD with SICCD as the symbol that
captures this high precision and high quality character of your camera. This
symbol occurs throughout our documentation as a shorthand reminder of those
high precision and high quality aspects of your camera system.
1.1.2 CCDs And How They Work
CCDs are used in a variety of consumer electronic products. A large assortment
of CCD sizes and types are available because of the popularity of this type of
sensor for low-cost digital imaging cameras. Most of these CCDs are not
scientific grade. Moreover, they are operated so as to give you a “TV” image.
CCD cameras that produce high quality digital images are designed to produce a
precision digital image and not a TV image. They are cooled well below ambient
temperature to reduce dark signal and they are operated in “slow readout mode”
to minimize readout noise.
Digital images are organized in a row/column format. Image elements (pixels)
emerge from a corner of the sensor. A sensor with more than one active corner
produces more than one stream of pixels during readout. Figure 2., below,
illustrates a single-port and a four-port CCD.
Referencing the left-hand portion of Figure 2., the checkered center region is the
imaging area. It is called the parallel register. To read out the CCD, the grid of
pixels is moved, one row at a time to the left, along columns, into the serial
register, labeled SR. Once a row is moved into the serial register, it is then
moved, one pixel at a time to the output node, shown as a triangle and labeled A.
A column is a line of pixels consisting of one pixel from each row. The CCD
does not read out columns, it reads out rows. But many characteristics of the
image that results are shared by all of the pixels at the same location in each row
(the same column) so they are analyzed as columns of information. Defects
involving multiple pixels are almost always column defects.
