Frame Interval Timings - 2¶

This section describes camera timings when using continuous read mode controlled by the on-board DSP.

• CCD clear only occurs on the first cycle and is typically on the order of 75 ms. Cycles 2 - n do not have a CCD Clear cycle.
• Exposure time specifies the time the sensor is exposed to light and is set as part of the 'Set Exposure Time' command
• Read-out time indicates the time it takes to readout the array. This time depends on array size and and read-out mode selected. For Hamamatsu 7031-1007 type sensor (1024x128) using FVB that time is in the 5 ms range. For the same array using area read-out mode the time is ~ 250 ms.
• Frame pad is the time added to each cycle to accommodate the data transfer time to a PC or the balance of the frame interval time (see Frame Interval Timings Explained)
• Communication to the PC using High speed USB link is typically 100 MBits / sec and is overlapped with the previous exposure and read out time

Example:
7031-1007 (1024x128) FVB, 1 sec exposure, 2 sec frame interval will yield the following:

• Cycle 1:
  o Clear CCD: 75ms
  o Exposure: 1 sec
  o CCD Readout: 5 ms
  o Frame Pad: 995 ms (Balance of the 2 sec frame interval time)
• Cyc 2
  o Clear CCD: 0 (No Clear CCD takes place)
  o Exposure 1 sec
  o CCD Readout: 5ms
  o Frame Pad: 995 ms
• Cyc n
  o Clear CCD: 0
  o Exposure 1 sec
  o CCD Readout: 5ms
  o Frame Pad: 995 ms

Note: effective exposure for first cycle is 1 sec, however, effective exposure for cycles 2 - n is ~ 2 sec.
Also, data transfer to the PC (4K bytes) takes less 1 ms and is effectively overlapped with (exposure, read-out, and frame pad). In this scenario it's best to discard the 1st frame.

Example 2

7031-1007 (1024x128) FVB, 1 sec exposure,  0 sec frame interval will yield the following:

• Cycle 1:
  o Clear CCD: 75ms
  o Exposure: 1 sec
  o CCD Readout: 5 ms
  o Frame Pad: 0 sec
• Cyc 2
  o Clear CCD: 0
  o Exposure 1 sec
  o CCD Readout: 5ms
  o Frame Pad: 0 sec
• Cyc n
  o Clear CCD: 0
  o Exposure 1 sec
  o CCD Readout: 5ms
  o Frame Pad: 0 sec

Note: In this case the effective exposure for all the cycles (1, 2, n) is 1 sec