192 CONTENTS
Note
In partial scan mode (readout window ysize < 480 lines).
To calculate the maximum frames per second (FPS
max
) you will need following formula (ExposeMode: Standard):
FPS_max = 1
-----------------------------------------------
t_trig + t_readout + t_exposure + t_trans + t_wait
(ExposeMode: Overlapped):
t_trig + t_readout + t_trans + t_wait < t_exposure: FPS_max = 1
---------------
t_integ
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, 65 us, 100 lines and 12MHz pixel clock
(ExposeMode: Standard):
FPS_max = 1
-----------------------------------------------------------------------------------
10 us + ((100
*
64 us) + ((510 - 100)
*
4.85 us) + 3.15 us) + 65 us + 64 us + 64 us
= 0.0001266704667806700868 1 / us
= 126.7
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. 180).
20.1.4 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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