1.19 Appendix A. Specific Camera / Sensor Data 185
To calculate the maximum frames per second (FPS
max
) you will need following formula (Expose mode: Sequential):
FPS_max = 1
-----------------------------------------------
t_trig + t_readout + t_exposure + t_trans + t_wait
(Expose mode: Overlapped):
t_trig + t_readout + t_trans + t_wait < t_exposure: FPS_max = 1
---------------
t_exposure
t_trig + t_readout + t_trans + t_wait > t_exposure: FPS_max = 1
-------------------------------------
t_trig + t_readout + t_trans + t_wait
Example: Frame rate as function of lines & exposure time
Now, when we insert the values using exposure time of, for example, 8000 us, 768 lines and 40MHz pixel clock
(Expose mode: Sequential):
FPS_max = 1
-------------------------------------------------------------------------------------------
4.85 us + ((768
*
32.7 us) + ((788 - 768)
*
4.85 us) + 32.7 us) + 8000 us + 22.5 us + 58 us
= 0.000030004215592290717 1 / us
= 30
Note
The calculator returns the max. frame rate supported by the sensor. Please keep in mind that it will
depend on the interface and the used image format if this frame rate can be transferred.
See also
To find out how to achieve any defined freq. below or equal to the achievable max. freq., please have a look
at Achieve a defined image frequency (HRTC) (p. 164).
1.19.1.3.4 Reprogramming CCD Timing
Reprogramming the CCD Controller will happen when the following changes occur
• Changing the exposure time
• Changing the capture window
• Changing Trigger Modes
Reprogram time consists of two phases
1. Time needed to send data to the CCD controller depending on what is changed
exposure : abt 2..3ms
window: abt 4..6ms
trigger mode: from 5..90ms,
varies with oldmode/newmode combination
2. Time to initialize (erase) the CCD chip after reprogramming this is fixed, abt 4.5 ms
So for example when reprogramming the capture window you will need (average values)
t
regprog
= change_window + init_ccd
t
regprog
= 5ms + 4.5ms
t
regprog
= 9.5ms
MATRIX VISION GmbH
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