User manual

Rolera Thunder User Manual 9
Chapter 3
Operating Features
Introduction
The features described in this section are identical in all Rolera Thunder cameras unless
otherwise stated.
On-Chip
Multiplication
Gain
As explained previously, the Rolera Thunder uses a unique CCD capable of multiplying the charge
(electrons) generated in the pixels. When the multiplication is sufficiently high, it is possible to
see extremely low-light events. The amount of multiplication is controlled by the voltage applied
to multiplication register clocks. These are certified by a quantitative multiplication gain slider
which has 0-1000 steps. The calibration feature of the camera maps the gain slider to a voltage
which will provide the electron multiplication level selected.
Offset (bias)
CCD cameras are typically designed to produce a certain level of offset (also known as bias) when
no light is present and the exposure time is set to zero (0). Typically, the user subtracts an offset
(bias) from the sample image for quantitative measurement. Since the offset can change based
on several factors such as multiplication gain, speed, etc., it is recommended that a fresh offset
(bias) image be taken with the same settings as the sample image and then be subtracted from
the sample image.
The Rolera Thunder has an automatically adjusting offset switch. When a speed/gain setting is
altered, the bias valve is kept as close to a pre-selected offset as possible. This enhances the
quantitative stability of the camera.
Exposure-
Readout Modes
The Rolera Thunder camera uses a frame transfer CCD and supports Non-Overlap and Overlap
exposure and readout modes. These modes are further described in the sections that follow.
Note: A frame transfer CCD has both a light-sensitive area (sensor area) and a storage area (frame transfer
area). Since the image can be quickly transferred from the sensor area to the frame transfer area, there is no
need for a mechanical shutter.