[Elphel-support] Flash on a two camera system

[Andreas Bean]

Andrey,

In fact we develop a led light and not a discharge flash, therefore the
light isn't deposited in a short period. You say the exposure of the
last scanline starts 67ms after the first line. I'm trying the get light
intensity high enough for an exposure time of 5ms. This means that the
leds have to be turned on for 72ms ?

And additionally I don't know how long they need to reach the full
intensity, that's why I asked if its possible to get the signal before
the trigger.
How would you connect the led driver circuit to the cam?

Does it matter that the signal is only for one cam? They are closely
mounted together, so the signal can be used for both, can't it?

Have consumer digital cameras also the delay between the exposure of the
first and last line? Does that mean that during a fast movement the
first and the last line in the picture differ significantly?

Andreas



Andrey Filippov schrieb:
> Andreas,
>
> Why do you need  pulse _before_ trigger? With this senor exposure of
> the first line start 8 scan lines after the trigger, last line
> exposure starts 1/15 sec later. So if you want to use a flash, you
> need to set the exposure time >1/15 sec and trigger flash 1/15 after
> the trigger.
> The FPGA has delay timer, when the camera is triggered externally,
> this programmable delay is between the arrival of the sync pulse and
> the sensor triggering. When the camera is set to trigger directly from
> the FPGA (trigger condition =0), the delay sensor is triggered
> immediately, and the output sync is delayed by the programmed value -
> you may use it for the flash. Unfortunately it is for a single camera
> only.
> If you still need pulse before the sensor trigger - you may just
> reverse the trigger source - use external pulse, apply it to multiple
> cameras in parallel - each camera can  be individually delayed by
> programming TRIG_DELAY parameter.
>
> Andrey
>
>

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