Andreas, Yes, you are right - I just did not think of that. If you can generate rather constant brightness for 70+ ms, then you do not need any delay and you do not need to have light much brighter than environment. The duration of the light has to be readout time + exposure time (exposure may be short), and the light should be triggered simultaneously with the camera (or earlier - each camera delay is programmable). when the camera is triggered it start exposure of the first line, at exposure+readout time - finishes the exposure of the last. What happens before first or after last - does not matter.
Andrey On Fri, Mar 16, 2012 at 2:55 PM, Andreas Bean <[email protected]> wrote: > Andrey, > > Thanks for the description of the trigger pulse. An optocoupler is fine, > I will do it that way. The module is controlled by a microcontroller, so > we can set arbitrary delay times. But if I remember correctly, I need to > set the exposure time to 67ms to use the flash as an shutter and the > flash has to be much more brighter than the scene without flash. > > Lets say in an average room with two windows the leds may double or > triple the brightness of the scene or even if the flash increases the > intensity by a factor of ten. > > Our camera is helmet mounted. We have seen that during walking we can't > go beyond 7ms exposure time without reasonable motion blur. From my > point of view I can't set 67ms. Or am I missing something here? > > Andreas > > Andrey Filippov schrieb: >> Andreas, >> >> Short flash is definitely better (if that will not bother too much >> humans - operator and/or other people), you'll save a lot of energy >> and if you can get it really short (>10 ms) - you will not suffer from >> motion blur. >> For delaying lamp - I would recommend you to try some laboratory delay >> generator, then make a simple circuit - there are so many ways how to >> do that. Even analog one-shot with a potentiometer should do the job, >> to be on the safe side (to protect the cameras) you can put an >> opto-coupler on the input - the camera trigger pulse is 5V amplitude >> and drives up to 1A, so it is easy to connect optocoupler input in >> parallel to the other cameras, >> >> Andrey >> >> On Fri, Mar 16, 2012 at 1:21 PM, Andreas Bean <[email protected]> wrote: >> >>> Andrey, >>> >>> Earlier we talked about using the LEDs as "snapshot shutter" versus >>> continuously lighting the scence. >>> At the moment we have 2x100W LEDs on the cam, but I think that will not >>> be enough to have snapshot functionality for panoramic indoor frames. >>> What do you think? >>> >>> So I'm thinking that it will be better to continuously light the scene >>> for 70ms during the exposure of the first to the last line. >>> In that case I don't need any delay, do I? >>> >>> What kind of circuit to you propose to get the trigger to the LEDs not >>> corrupting the camera timestamp sync? >>> >>> Andreas >>> >>> >>> Andrey Filippov schrieb: >>> >>>> Andreas, >>>> >>>> I think that modulated signal will still trigger your flash, that >>>> should not be a problem. With the single connector - the easies would >>>> probably be to add an external delay before the flash for 70 ms. >>>> Cameras have programmable delays between trigger and input and >>>> starting acquisition, but here you need the cameras to start 70 ms >>>> earlier than the flash - they need this time to erase each line. So >>>> you are correct - exposure should be at least frame readout time + >>>> flash time, and the flash should be triggered with the frame readout >>>> time delay. It is possible to tweak the FPGA code and use the other >>>> set of sync signals (small flex cable connectors inside the camera) >>>> and add external connector, but that is not done yet. >>>> >>>> Andrey >>>> >>>> On Fri, Mar 16, 2012 at 9:00 AM, Andreas Bean <[email protected]> wrote: >>>> >>>> >>>>> Andrey, >>>>> >>>>> Three days ago I got our two 100W led lighting modules for our panoramic >>>>> camera. >>>>> The trigger is a 0 - 5V signal against GND. >>>>> >>>>> Whats the easiest option to connect the modules to the camera? The >>>>> trigger turns on the leds for 80ms. >>>>> If I remember correctly then 70ms + exposure time is needed due to the >>>>> rolling shutter. >>>>> >>>>> I'm not sure if its a good idea to use the camera sync port, since we >>>>> already connected two cameras >>>>> together. Also the timestamp is sent via that port, so it can't be a >>>>> simple trigger signal. >>>>> >>>>> Whats the best option to get the leds triggered? >>>>> >>>>> Andreas >>>>> >>>>> >>>>> _______________________________________________ >>>>> Support-list mailing list >>>>> [email protected] >>>>> http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com >>>>> >>>>> >>>>> >>>> _______________________________________________ >>>> Support-list mailing list >>>> [email protected] >>>> http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com >>>> >>>> >>> _______________________________________________ >>> Support-list mailing list >>> [email protected] >>> http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com >>> >>> > > > _______________________________________________ > Support-list mailing list > [email protected] > http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com > _______________________________________________ Support-list mailing list [email protected] http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com
