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Inconsistent uniformity of black screen representation.

Jack Chuang
Prodigy 10 points

Hello TI members,

The image below shows the same projector paired with two DMDs of the same model.

Why do DMDs of the same model exhibit different black screen performances?

We speculate that this is related to the oscillation angle of the DMD.

Does anyone have any ideas?

  • 0
    TI__Expert 7910 points

    Hello Jack,

    Welcome to the E2E forum and thank you for your interest in DLP® technology.

    Can you please provide more information about your questions? 

    1. What the part number of DMD and controller you are using?

    2. Do you have an EVM or custom board?

    Regards,

    Lori 

  • 0 in reply to Lori Wang
    Prodigy 10 points

    Hi Lori,

    we use a DMD with the specifications of 0.96" WUXGA 2xLVDS TYPE-A. It's controller is DPP4422, and we use this DMD with a custom board. Thx.

  • 0 in reply to Jack Chuang
    TI__Genius 12595 points

    Hello Jack,

    This thread appears to have been assigned to the wrong group. I am reassigning to our colleagues in the appropriate group.

    Regards,

    Austin

  • 0 in reply to Jack Chuang
    TI__Expert 5110 points

    Hello Jack,

    Please, can you confirm that you are utilizing different DMDs within the same optical system and light engine to produce the images? Or are the systems entirely different?

    Best,

    Aaron

  • 0 in reply to Aaron Black
    Prodigy 10 points

    Hello Aaron,

    Yes, using the same machine for testing, when displaying the black screen on DMD #1, the outer area is red and the inner area is green. When displaying the black screen on DMD #2, the outer area is green and the inner area is red. Both DMD #1 and DMD #2 are of the same model. When I switched to another machine of the same model, the black screen on DMD #1 still had the outer area red and the inner area green, and the black screen on DMD #2 still had the outer area green and the inner area red. Therefore, I believe this phenomenon is strongly correlated with the DMD.

  • 0 in reply to Jack Chuang
    TI__Mastermind 43165 points

    Hello Jack,

    Aaron, is currently unavailable and I will be covering this for him for now.  I would like to consult with our optics team on this question.  They may have some valuable insight.

    Can you tell me a little about the optics of the systems you are testing this on?  Such as the f # of the illumination and the f # of the projection system?

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points

    Hello, the f # of our projection system is 2.4 and our projection lens is 2.0. I found an similar system online, our projector is composed of blue laser, phosphor wheel and red laser. 

    May I ask if the reason for inquiring about the f-number is related to the suspicion of its association with diffraction?

  • 0 in reply to Jack Chuang
    TI__Mastermind 43165 points

    Hello Jack,

    Thank you for the information about the optical system.

    Any time I confer with the optics team, I ask for these numbers because I know they will ask for them.  I do not know about diffraction, but it may be possible.

    Please allow a couple of days to confer with them.

    Fizix

  • 0 in reply to Fizix
    TI__Mastermind 43165 points

    Hello again Jack,

    It looks like there is also a parallel email chain on this topic that is getting more traction.  I would like to consolidate to that email chain and close this thread for now if you agree.  If there is a finding that we can post in the public forum, we can post it back here at the conclusion.

    Thank you.

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points

    Hello Fizix,

    Alright, the consistency of black screen performance seems to be increasingly valued, especially in the context of projector stitching. We will also reach out to your company's FAE to inquire about any further improvements we can make regarding black screen optimization. Thanks.

    Jack.

  • 0 in reply to Jack Chuang
    TI__Mastermind 43165 points

    Hello Jack,

    I reached out to you in email and should have feedback from the Optics team for you very soon.

    Fizix

  • 0 in reply to Jack Chuang
    TI__Intellectual 1930 points

    Hi Jack,

    I think there is a separate off-line thread to address this topic further.  At a high level, slight variations in the black level color can occur depending on the system illumination combined together with slight variations of the DMD mirrors.  All of the mirrors we believe are operating within the specifications, but may be more noticeable at higher lumens and higher on-screen illuminance.   Some factors as follows may show the effect as the above pictures.

    • Mirror tilt variation inside the part
    • Slight changes in metal density across part
    • Illumination angle of incident variation across the array in the system

    Thanks,
    Jason