Photometrics Evolve 512, Руководство пользователя

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12 Evolve 512 Users Manual
Overlap Mode
(Simultaneous
Exposure-Readout)
Overlap mode is extremely useful in applications requiring continuous imaging (100% duty
cycle). Once a frame is exposed and transferred into the frame transfer area, the next
exposure immediately starts and continues until the previous frame is read out or until the
exposure time is finished, whichever is longer (so the minimum effective exposure time in
this mode is the readout time). This mode of operation allows you to continuously image a
specimen to obtain better kinetic information about a process. Figure 8 shows the required
Evolve 512 settings for overlap mode. Note that the clearing mode is set to "Pre-sequence"
(as opposed to "Pre-exposure" in Non-Overlap mode).
Figure 8. Required Settings 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 29.5 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 98.5 ms (3

29.5 ms + 10 ms), equivalent to a
frame rate of 30.45 fps (3 frames

0.0985 seconds).
Note: Because the first frame is exposed for 10 ms and the others for 29.5 ms, the first frame may look
less bright compared to all other frames.