Princeton Instruments PhotonMAX System, Manual, Page: 49 / 98

Chapter 5 Operation 49
Figure 33. Required Selections for Overlap Mode Operation
Note:
In Overlap mode, the minimum effective exposure time is the readout time.
The simultaneous exposure-readout mechanism is illustrated with two examples.
Example 1: Overlap Mode when Exposure Time < Readout Time
Consider a situation where full frame readout is 34.8 ms, the exposure time is 10 ms, and
three frames are taken in overlap mode. The first frame is exposed precisely for the
length of time entered into the software (10 ms) and all subsequent frames are exposed
for the readout time. The total time to acquire 3 frames is then 114.4 ms (3
×
34.8 ms +
10 ms), equivalent to a frame rate of 26.2 fps (3 frames
÷
0.114 seconds).
Note:
Because the first frame is exposed for 10 ms and the others for 34.8 ms, the
first frame may look less bright compared to all other frames.
In Overlap mode when exposure time < readout time, the total time (T
N
) taken to
capture N frames is given by:
T
N
= (t
R
×
N) + t
exp
Where
T
N
= Total time taken to capture a sequence of N frames
t
R
= readout time for one frame
N = total number of frames in a sequence
t
exp
= exposure time
Readout
Effective
Exposure Time
Exp #1
10 ms
Exp #2
34.8 ms
Exp #3
34.8 ms
Readout #1
34.8 ms
Readout #2
34.8 ms
Readout #3
34.8 ms
Total time for 3 frames is approximately 114.4 ms
Clears
Figure 34. Timing Diagram for Overlap Mode when
Exposure Time < Readout Time
Select the
"Clear Pre-Sequence"
Clean Mode.
Select the
"Frame Transfer"
Readout Mode.
Select 2 or more
Images/Spectra.
Set to Fast Mode.