Getting the best out of sCMOS cameras-II

[Credits: Amit Cherian and Manoj V Mathew
Experiments were conducted at the Central Imaging and Flow Cytometry Facility (CIFF), National Center for Biological Sciences (NCBS), Bangalore, India.]

We conducted a series of experiments by triggering the Hamamatsu Orca Flash 4 C11440 camera using an external trigger source. 

Exp:1 Speed Test using Camera Link Interface and Internal Trigger

We tested the maximum speed of operations in FPS for different frame sizes while using the external trigger. The trigger signal was generated using a Tektronix AFG 3252 Arbitrary Function Generator. The following parameters were used:

  1. Waveform Used: Square Wave
  2. Duty Cycle: 20%
  3. Data Interface: Camera Link
  4. Camera Speed: Standard Scan
  5. Capture Mode: External Edge Trigger
  6. External Trigger Input Option: Pos (Trigger on Positive Edge of the Pulse)

The connection diagram is shown in Figure B8.

Figure B8: Connection diagram for external triggering of Hamamatsu Flash 4 using Tektronix AFG.

The signal output of the function generator was connected to the Ext.Trig SMA connector at the back of the camera using a BNC to SMA cable.

Like in the case of experiments with the internal trigger, we used the Hamatusu HCI software as well as the Micromanager software by operating the camera in the live mode. Frame rates were read out from the indications on the live window. Both HCI and micromanager software data were consistent.

The results of the experiment are summarized in Table T5.

Table T5: Maximum speed of operation in FPS for various frame sizes using the camera link interface and external trigger (PDF Format).

The log-log plot of speed of operation in FPS as a function of Frame Size for external triggering is shown in Figure B9.

Figure B9: Log-Log plot of frame size vs speed of acquisition in fps for Camera Link Interface and external trigger

When comparing the internal and external trigger modes we observe the following:

  1. For frame sizes 2048x256 or larger the speed of operation in external trigger mode is slightly lesser than the speed of operation in internal trigger mode.
  2. For frame Sizes smaller than 2048x256 while internal trigger mode enables the use of exposure times lower than 1.0037ms, for external triggering the minimum exposure time value is fixed at 1.0037ms for all frame sizes. So for frame sizes smaller than 2048x256 the speed is significantly lower than those obtained for internal triggering.





  1. Manoj V Mathew: Conceptualized the ideas, designed the experimental setups, and wrote the article.  
  2. Amit Cherian (NCBS, Bangalore): Setup the equipment, conducted the experiments, tabulated and analyzed data and generated the figures.


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