180
Name Description Pixel clock
20 MHz 40 MHz
t
trig
Time from trigger
(internal or external) to exposure start
3.6us 1.8us
t
trans
Image transfer time
(move image to readout cells in CCD)
42.6us 21.3us
t
readline
time needed to readout a line 39.05us 19.525us
t
vshift
time needed to shift unused lines away 3.6us 1.8us
t
wait
minimal time to next trigger 7.2us 3.6us
t
exposure
Exposure time 1us..10s 1us..10s
t
readout
Image readout time
(move image from readout cells to memory
t
readout
= (ActiveLines ∗ t
readline
) + (504 - ActiveLines) ∗ t
vshift
+ t
readline
1.19.1.2.3.1 Timings
Note
In partial scan mode (readout window ysize < 480 lines).
To calculate the maximum frames per second (FPS
max
) you will need following formula (Expose mode: No overlap):
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
1.19.1.2.3.2 Example: Frame rate as function of lines & exposure time
Now, when we insert the values using exposure time of, for example, 8000 us, 480 lines and 40MHz pixel clock
(Expose mode: No overlap):
FPS_max = 1
-----------------------------------------------------------------------------------------------
1.8 us + ((480
*
19.525 us) + ((504 - 480)
*
1.80 us) + 19.525 us) + 8000 us + 21.3 us + 3.6 us
= 0.0000572690945899318068 1 / us
= 57.3
1.19.1.2.3.3 Frame rate calculator
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).
MATRIX VISION GmbH
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