• State
  • Locked Locked
  • Replies 33 replies
  • Subscribers 30 subscribers
  • Views 7566 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Flickering Screen and Test Patterns for DLP LightCrafter EVM

Melissa Ferrari
Prodigy 200 points

I have been having issues with a flickering output from the DLP LightCrafter.  The issue is pronounced in the attached video of the boot-up sequence below.  I am able to Connect the device through the GUI.  When using the checker Test Patterns, they retain their general shape, but the edges of the checker boxes are dynamically wavy.  When using the horizontal and vertical grey ramp I get flickering bands of light and dark of varying sizes.  There are other characteristics of the other patterns I can discuss if necessary. 

This issue has come up twice in two separate DLP LightCrafter EVMs that I have purchased.  In the most recent instance it occurred once I had attempted to connect the mini HDMI to a computer in hopes to be able to project custom videos.

I am hoping somebody from TI technically support will be able to help me solve this issue as soon as possible.

Thank you,

Melissa

 

Link to video in GoogleDrive.

  • 0
    TI__Genius 10495 points
    Hello Melissa,

    I am sorry to hear that you are having problems with your EVM. I will move your question into the DLPLIGHTCRAFTER forum.

    Best regards,
    Nadine
  • 0
    TI__Intellectual 2305 points
    Melissa,

    Welcome to the DLP LightCrafter Development Platform Forum!

    Has the LightCrafter always behaved with flickering? Or is this behavior new? Or after any modifications to the board ? Or after disconnecting and connecting flexcables or connectors? Could you explain what you have tried so far, please? Does it work as expected when the mini HDMI is not connected?

    Regards,
    A214529
  • 0 in reply to A214529
    Prodigy 200 points

    No, the LightCrafter has not always had this flickering behaviour.  It had been performing as expected prior to the flickering.  This is the second LightCrafter EVM where this has happened in the past 3 weeks.

    I have removed the light engine as outlined in this video and am using a custom optical system with a 450nm LED.  After doing this, the test patterns were working as expected.   Again, in both cases, it had worked as expected after I connected the mini HDMI to an external computer for at least a couple of hours.  To be clear, I was unable to properly connect to an external computer because I was unable to match the resolutions, but switching back to Test Patterns worked fine.  After some time, the patterns began flickering.  

    The Firmware Versions are DM365: 5.0 ; FPGA: 2.6.43 ;  MSP430: 3.0.

  • 0 in reply to Melissa Ferrari
    TI__Intellectual 2305 points
    Melissa,

    The RGB LED Driver is designed to work with the specific Red, Green and Blue LEDs for this light engine. Other LEDs may have different I-V characteristics and may not work at all, or may work for a while and then may malfunction when temperature rises (or other causes). Try decreasing the LED current settings and see if you can get continuous stable operation without flickering.

    Regards,
    A214529
  • 0 in reply to A214529
    Prodigy 200 points

    I decreased the LED current 1000X and I was not able to get operation without flickering.  Are there any other things I can try to fix this?

  • 0 in reply to Melissa Ferrari
    TI__Intellectual 2305 points
    Melissa,

    Can you plug back the original optical system (with the original Red, Green and Blue LEDs) and verify if the LightCrafter still works as expected.

    Does the custom optical system uses a compatible flex-cable, or how the connectivity between it and the LightCrafter board takes place?

    Please review the technical data, datasheet and test the connectivity of your custom optical system. Is each color channel connected to a LED or Laser device with I-V characteristics that are not too different from the original RGB LEDs (see below)?

    Green: L CG H9RN
    Red: LE A Q9WN
    Blue: LE B Q9WN

    Regards,
    A214529
  • 0 in reply to A214529
    Prodigy 200 points

    I am trying to reconnect the original optical system by going backwards through the steps in this video.  Around 4:38 they use tweezers to remove the DMD.  The DMD does not fit easily into the light engine and it requires some force to remove it.  Should I be trying to push it in so that it fits, or can I run this test without doing that?  If it is necessary that I fit the DMD into the light engine, which way should the "triangular notch" point.

    My setup is pretty simple.  I am only using a single LED (as I only need one colour) to illuminate the DMD.  That is how I managed to project the video in my original post, and this setup was working very well for me at first.  I'm not sure I understand how having different LEDs would affect the projector negatively as I've been seeing.  If you could provide a little bit more of an explanation, I would greatly appreciate it.

  • 0 in reply to Melissa Ferrari
    TI__Intellectual 2305 points
    Melissa,

    The LightCrafter won't work with just 1 LED. There is an "open LED" protection (over-voltage) circuit that would trigger if any of the LEDs are not connected. Note that you can disable any LED using the GUI software, if you just want to use your 450nm LED.

    Regards,
    A214529
  • 0 in reply to A214529
    Prodigy 200 points
    Do you have any input on my first question, with regards to setting up the original optical system as you suggested earlier?
  • 0 in reply to Melissa Ferrari
    Prodigy 200 points
    I am using a third party 450nm LED to illuminate the DMD. This setup worked well for two separate LightCrafter EVMs with Light Engine removed, but after some time I started seeing the issue that I described in my first post and is shown in the video of my first post.
  • 0 in reply to Melissa Ferrari
    TI__Intellectual 2305 points

    Melissa,

    Yes, it makes sense to run this test with the DMD into the light engine.  The  "triangular notch" point as shown on the attached pictures.

    Please send complete technical information and anything needed about your custom optical engine and LEDs used, if you'd like me to take a look further and try to understand this issue.

    Regards,

    A214529


  • 0 in reply to A214529
    Prodigy 200 points
    Sorry for the late response, I was out of town.

    I plugged back in the original optical system as you had suggested on March 9th and the LightCrafter worked as expected.

    As for my customized system: I removed the optical system as outlined in the TI video and blog posts, I also flipped the systems and drivers board 180˚ as they mentioned at the end of the video. I connect the LightCrafter to the PC through the mini USB port and control it through the GUI. I am able to connect the device through the GUI successfully. Then I choose, for instance, the fine checkerboard pattern.

    My custom optical system is NOT connected to the LightCrafter board. It is simply an LED (www.thorlabs.com/thorproduct.cfm which I reflect off the DMD. I have been able to successfully see the pattern reflected off of the DMD.

    However, after a couple of days, the patterns start to malfunction as I described in the March 2nd post. I have clear videos of the malfunctioned patterns that I am having difficulty uploading to this forum, but if you could provide me with your email address, it might help to clarify my issue.

    Do you have any suggestions for further steps?
  • 0 in reply to Melissa Ferrari
    TI__Intellectual 2305 points

    Hi Melissa,

    Yes, it would be helpful to see the videos.  This is the recommended way to embed a video.

    Regards,

    A214529

  • 0 in reply to A214529
    Prodigy 200 points

    This is what I see when using my custom optical system for the two checkerboard test patterns in the GUI. 

  • 0 in reply to Melissa Ferrari
    Prodigy 200 points

    This is what I see when using my custom optical system for the horizontal gray ramp test patterns in the GUI.

  • 0 in reply to Melissa Ferrari
    Prodigy 200 points

    This is what I see when using my custom optical system for the horizontal and vertical stripe patterns in the GUI.

  • 0 in reply to Melissa Ferrari
    Prodigy 200 points
    Please confirm that you can see or download these videos. Please let me know if you have any other potential solutions.
  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points

    Hello Melissa,

    We are able to see the videos.  It is almost like the system(s) is(are) showing the bitplanes of a grayscale image very slowly in time rather than quickly in single frame. Is this a custom sequence you have loaded?

    How are you putting the images in and are you using any kind of triggering?

    Fizix 

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points
    Hello again Melissa,

    I missed that you are running your LED independently. The ligthcrafter uses source modulation to form the LSB bit times. If you are not modulating your source then you will see bizarre bit-weight patterns.

    Please try setting your sequence to use only a single LED (let's say Green) and then set up your LED to turn off and on with the Green LED enable signal and see if this cures the behavior. I am not sure why it would have worked correctly for a while before starting this behavior.

    Fizix
  • 0 in reply to Fizix
    Prodigy 200 points

    I am not sure modulating and synchronizing my external light source would fix the problem.  If this were the case, wouldn't the flashing be too quick to see in real time?

    I just purchased a new DMD this week as I was waiting for your response, again it worked for some time at first and then after a few hours the output images were shifted and causing the same problems that I showed above in the videos.  It seems like there is something wrong with the firmware because the patterns have the exact same issues each time.

    Also, the light closest to the Input selection button on the board flashes between red and green.  Is this normal or could this be some indication of my issue?

    I am looking to create a system where I can have a 450nm LED reflect off the DMD and be imaged at the sample plane of an inverted microscope.  I really hope to solve this problem as quickly as possible, so if you have any other suggestions, I would greatly appreciate them.  

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points

    Mellissa,

    You are correct, the switching should be too fast to see.  That is what prompted the question about whether you are externally triggering. 

    It sounds like you are not doing anything unusual.

    When you say you purchased a new DMD.  I want to understand.  Did you replace the DMD in the EVM or do you mean you ordered another EVM.

    I will have my colleague that is familiar with the firmware look at your questions about the LED that flashes alternately between green and red.

    Fizix

  • 0 in reply to Fizix
    Prodigy 200 points

    This is the second EVM that I have purchased which has the same issue, but that is what I was referring to in my earliest posts. Last week I tried a new DLP (http://www.ti.com/product/DLP3000

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points

    Melissa,

    So that I make sure I am understanding, after receiving the new DMD you replaced the DMD in one of the kits and it again operated as expected for a little while and then began to exhibit the same behavior.  Is this correct?

    Thanks.

    Fizix

  • 0 in reply to Fizix
    Prodigy 200 points

    Yes exactly.

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points

    Melissa,

    Thank you for the confirmation.  Our team will discuss this and get back with you. 

    Could you also show a diagram of how your illumination is wired up and how your solution is set up to generate your patterns in the software.

    Thank you,

    Fizix

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points
    Hello Mellisa,

    Thank you for the diagram. In discussing this here we realized that we have not asked how much optical power this LED is illuminating the DMD with and what wavelength(s). Could you tell us about the LED characteristics and how much current you are driving it with?

    Thank you again.

    Fizix
  • 0 in reply to Fizix
    Prodigy 200 points
    The LED is 450nm with a documented power output of 1850mW. I drive it with a current that is just under 2.0A. The LED is collimated and the output power measured with a power meter is approximately 260 - 300mW. Most of that light does not get to the DLP chip because the collimated beam is larger than the DLP. The power measured after the collimated light reflects off the DLP was around 130mW.
  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points

    Melissa,

    Thank you, that information is very helpful in eliminating possible causes.  The power level that you are using should not be a problem, so we will have to look elsewhere. 

    We have not seen this issue before and will discuss it further.  I am sorry that we have not yet been able to pinpoint the issue or cause.

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points
    Dear Fizix and Mellissa,

    Hello my name is Hyeonseung.
    I'm having the exactly the same issue with Mellissa on the lightcrafter.
    I removed the light engine and illuminated with the DMD with the external laser source ( HeNe laser , 633 nm , 2 mW )
    I've been using it for a month and projecting the test pattern was perfectly working until yesterday.
    When I turned on the DMD today to do some experiment, the DMD started to malfunction.
    It shows flicking around the edges in the test check board pattern. ( Exactly the same behavior with Mellissa's DMD)
    Projecting images through HDMI also shows same flickering behavior.
    I really hope to see some solution from TI.

    Hyeonseung
  • 0 in reply to Hyeonseung Yu
    TI__Guru 54390 points

    Hello Hyeonseung,

    Thank you for this feedback it is helpful.  I agree this sounds like the same behavior as Melissa's.  We are continuing to investigate, but are not able to reproduce the effect here.

    Fizix

  • 0 in reply to Fizix
    Prodigy 200 points

    Hey Fizix, 

    Since you are unable to reproduce the effect there, would it be helpful to send one to you?   I currently have two EVMs that are not functioning as I need them to, and are therefore unusable until we come up with a solution.   

  • 0 in reply to Melissa Ferrari
    TI__Guru 54390 points
    Hello Melissa,

    I was thinking something similar. Let me see what would be necessary to get this rolling. I will send you a friend invite.

    Fizix