Photometrics Cascade 128, User Manual, Page: 33 / 54

22 Cascade User Manual
A slower readout speed can be used when better noise performance is needed at
the expense of frame rate. On the other hand, increased frame readout rate can
be achieved by one or more of the following
•
higher readout speed,
•
sub-region selection,
•
binning.
For more information on frame rate, please refer to the product data sheet.
Binning
Binning (combining pixels into one super pixel) allows you to increase the
sensitiv
i ty and frame rate. On the other hand, binning reduces spatial
resolution. The Cascade: 512F and 512B allow binning of 1, 2, 3, 4, 5, and 6 in the
serial (horizontal) direction and arbitrary binning in the parallel (vertical)
direction. The Cascade:128+ and the Cascade:128 allow binning of 1, 2, 3, and 4 in
the serial (horizontal) direction and arbitrary binning in the parallel (vertical)
direction.
Note: Due to the small array size in the Cascade:128+ and the Cascade:128, edge artifacts
may be present at higher binning.
Application Examples:
Cascade:512F and 512B
Example 1 “I would like to obtain kinetic information (time-correlated) information of the single
molecule fluorescence. My light level is fairly low and I want to optimize the frame rate
of the camera.”
For this application, the "Multiplication" port (Port #1) should be selected and
camera speed should be set to 10 MHz. In addition, the camera should be
operated in “Overlap mode”. This can be achieved by setting the camera to
“frame transfer mode” with clearing mode “Pre-sequence” and number of clears
“1” (refer to
Figure 5, page 13 ). If possible, choose a sub-region (ROI) and/or
binning to further increase the frame rate. Finally, on-chip multiplication gain
can be used to boost the signal level and achieve a high signal-to-noise ratio.
Example 2 “My application requires precise control of the exposure time (less than the readout
time) and I want to operate the camera in the most sensitive mode possible.”
For better imaging characteristics, the "Multiplication" port (Port #1) is selected
and camera speed must be set to 5 MHz. Use on-chip multiplication gain for
increased sensitivity. To achieve an exposure time less than readout time, use
Non-Overlap mode (as shown in
Figure 3, page 12 ) and set the clearing mode to
“Pre-exposure” and clear count to “2”.
Example 3 “ I would like to image a bright target/sample (e.g., fluorescence or bright field) that is
fixed. High resolution and high dynamic range are important."
For imaging bright, non-moving samples, the "Non-multiplication" port
(Port #2) offers the best performance in terms of dynamic range. Set the speed to
1 MHz (or 5 MHz, if higher speed is required) and conversion gain to #1 (this
allows maximum full well of the CCD to be used). Reading out the full CCD
(no-ROI or binning) gives best resolution possible. In addition, camera can be
operated in overlap or non-overlap mode as explained before.