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DLPLIGHTCRAFTER: Problem with Exposure time when using external trigger input

Karl Basker
Intellectual 385 points

Part Number: DLPLIGHTCRAFTER

Problem with Exposure time when using external trigger input

Dear TI support,

I want to use external trigger to run stored pattern sequence.

What I expect, is to have the pattern ON during given exposure time, then all mirrors in OFF position and then the same with the next pattern with the arrival of next trigger.

Similar to the screenshot from the Lightcrafter user guide, only I don't use delay: 

What I get instead though is that the pattern stays ON forever, until the next trigger changes it:

I tried various exposure times, triggers with different duration, duty cycles, and single triggers run manually.

But nothing changes - whatever I do, the pattern seems to ignore the exposure time set.

Here's a screenshot from DLP UI with one of many stored pattern settings that I tried:

Do you know something about this behavour and how could I solve the issue?

Thanks,
Karl

  • 0
    TI__Expert 3240 points
    Hello,

    Thanks for using the TI E2E forum. Our Lightcrafter 3000 expert is out for the holiday. He will be back Monday.

    Best,
    ~Danny W
  • 0 in reply to Danny White
    TI__Mastermind 20045 points
    Hello Karl and sorry for the delay,

    I was able to test on the Lightcrafter and confirmed correct operation. What is the frequency of your external trigger? Also where did you get your version of the firmware for the MSP430, FPGA, and DM365? Those are not the latest versions that I see available on our website so you may want to try those: www.ti.com/.../dlplightcrafter

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    TI__Mastermind 20045 points
    Hello Karl,

    If this is still an issue please let us know so we can reopen the thread.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Intellectual 385 points

    Hi Kyle.

    First, thanks a lot for checking this out for me. Sorry for delay, I was on vacation and wasn't able to do the tests and respond. In my tests, the frequency of trigger is vey low, I tried between 2 to 10 sec period as well as single triggers.Altough when everything starts to work well I would need to do higher triggering frequency up to 100Hz - 1 kHz if possible.

    The Lightcrafer is from Keynote Photonics, so it's their firmware versions. But yesterday and today changed to TI firmware, so now the versions are as follows:

    But that didn't seem to help.

    I will try to reiterate what I want basically to achieve. As in following example screenshot, using external trigger I want to display 3 patterns sequentially, each for 2 seconds. After these 2 sec I need all mirrors to switch to OFF position until the arrival of next trigger and so on.


    What happens though is whatever exposure time I do set, the pattern stays on until the next trigger swiches to next pattern.

    Interestingly, I noticed today that after the exposure time has passed (2 sec in this example), the mirrors emit high-pitch noise until the next trigger arrives, while they are totally silent during the exposure time. I guess that they are static during exposure time and then enter some mirror refresh mode (like video mode). 

    I hope this explains my problem well and maybe you could recreate this test on your side to compare.

    Thanks!

    Karl

  • 0 in reply to Karl Basker
    Intellectual 385 points
    Hi Kyle,

    I got a response from Keynote Photonics, which explains the issue. In my system I don't use LEDs and the LED module is not installed on my version of Lightcrafter. As they explained, the exposure is controlled not by the DMD, but by LEDs meaning that the pattern stays ON, but the LEDs turn off. That's why in my case there is no exposure time unfortunately.

    Do you think there is a way to modify the firware so that the exposure time is controlled by mirrors turning all-OFF instead of LEDs?

    Thanks
    Karl
  • 0 in reply to Karl Basker
    TI__Mastermind 20045 points
    Hi Karl,

    It may be possible by looking at the source code and trying to change some things. However, this is not intended operation and would not be supported. Perhaps a better solution would be to have your external trigger frequency increase and put multiple blank patterns after the desired display patterns.

    For example, if you want your pattern exposure to be 2 seconds and the trigger to be 10 seconds you could do the following. Add your desired pattern as the first pattern to display, add 4 blank (black) patterns, and then change the external trigger to 2 seconds.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Intellectual 385 points

    Thanks Kyle,

    that's what I am trying and it works really well. My first trigger displays the pattern and the second on is for blank pattern (either black or white).

    However there are cases when I can't use external trigger but I still need to have exposure time in pattern sequences and for that I don't find  a solution.

    Do you think it would be possible to modify the code so that the exposure time setting on DLP GUI is switching the mirrors all-off (or all-on)?

    Regards,

    Karl

  • 0 in reply to Karl Basker
    TI__Mastermind 20045 points
    Hello Karl,

    Unfortunately this operation is not something we support. You would have to find a way to control your illumination for this scenario or change the external triggers.

    Thanks,
    Kyle