Instruction manual

Theory of Operation

3.0 THEORY OF OPERATIONS

During exposure, the Imager’s CCD (Charge Coupled Device) detector collects photons emitted by the fluo-

rophore in a prepared gel. The detector is a semiconductor grid of approximately 180,000 cells for collecting

these photons. Each cell in the grid can collect up to 65,535 charge units per exposure. If a cell receives

more than 65,535 charge units, the excess charge units spill into the surrounding grid squares (in a phe-

nomena called “blooming”), and that area of the gel is considered saturated. These values serve as the raw

data for band analysis.

Because computer monitors typically display a maximum of 256 shades of gray, the computer must scale

each grid cell’s value to a value between 0 and 256, where 0 is absolute white, and 256 is absolute black.

Each “pixel” (picture element) on the monitor is illuminated at a corresponding level of brightness. This

value is a pixel’s grayscale value.

Figure 9. Imaging System Functional Diagram

UV SOURCE

(350nm to 400 nm)

GEL

EXCITATION FILTER

(NOT USER-SELECTABLE)

EMISSION FILTER

(FILTER TYPE IS SELECTED

USING THE SWITCH ON THE

BACK OF THE IMAGER)

CCD CAMERA/

DETECTOR