Specifications

51
Chapter 6
Exposure and Readout
Before each image from the CCD array appears on the computer screen, it must first be
read, digitized, and transferred to the computer. Figure 26 is a block diagram of the
image-signal path.
CCD
Preamp
Cable driver
Incoming photons
Up/down integrator
Fast A/D
HS serial buffer board
Display
Controller
Computer
Slow A/D
HS serial interface
Storage
Digital processor
Video
display
Camera
Figure 26. Block diagram of light path in system
The remainder of this chapter describes the exposure, readout, and digitization of the
image. Included are descriptions of binning for imaging applications and the specialized
ST-133 or ST-133A timing modes.
Exposure
Charge coupled devices can be roughly thought of as a two-dimensional grid of
individual photodiodes (called pixels), each connected to its own charge storage “well.”
Each pixel senses the intensity of light falling on its collection area, and stores a
proportional amount of charge in its associated “well.” Once charge accumulates for the
specified exposure time, the pixels are read out serially.