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LIghtcommander intensity linearity

Yun-Ho Jang
Prodigy 65 points
Other Parts Discussed in Thread: DLP5500, DLPC200, DLPC300, DLPC350, DLPC900

Dear, 

I've already asked to the design house, but I am posting here to see if there is a solution for my problem. 

I'm using DLP5500 with X3 board from Keynote Photonics. My application is to generate structured light with the DMD and laser, so I use a fixed-on illuminator. When I use 8bit gray patterns, the output intensity is not linear to the input images. The vendor said this is because the DMD makes the LSBs with both turning on/off mirrors as well as controlling illuminators, so some LSBs do not have linear relationship to the input images when I use a fixed-on illuminators. 

Is this issue limited to specific vendors or entire family of DMDs? If the all DMDs have same issue, is there any way to obtain linear and smooth response for 8bit gray images with a fixed-on illuminators? 

I attached a graph that I measured the DMD intensities when I display 256 steps of gray levels.  

Thank you.

Best regards, 

Yun-Ho

  • 0
    TI__Mastermind 30875 points

    Hello Yun-Ho,

    The issue is not specific to the vendors. The DLP display sequence are designed in this way for the LightCommander chipset, in short you will find this behavior common to DLP5500 (i.e., DLPC200 + DLP5500) chipset alone. For the fixed illumination we need to modify the sequences of the DLP5500 chipset. This is going to be new requirement and a development effort. 

    Can you tell more about your product? 

    Regards,

    Sanjeev

  • 0
    Prodigy 35 points

    Hi,

    I have a similar issue. I've  connected the DMD (DLP 5500) to a Lumencore solid state light engine (multiple LEDS) and find that the intensity reponspe of hte DMD for 8 bit gray images from 0-256 in steps of 4 cannot easily be inferred to be linear nor non-linear: I see a small S_shape but the small elevation after shade 124 can easily be due to experimental errors. Can you please take a look at the response curve I have attached tell me based on your experience whether the DLP is non linear or linear. I have used the software in static buffer mode so no video processing.

    Thank you,

    Mira

  • 0 in reply to Mira Sibai
    TI__Guru 54320 points

    Hello Mira,

    Welcome to the DLP section of the TI-E2E Community.

    I suspect that the characteristics of the Lumencore engine are a little different than the Rapcur LED driver and/or the PhlatLight PT54 series LED's used with the LightCommander.

    It is a little difficult to tell from just the picture if this is within your measurement error or not. It could also depend on your measurement methodology.  Without knowing your set up it is difficult to tell. 

    If you would like to discuss this offline rather than on the public forum please send me a friend request.

    Fizix

  • 0 in reply to Fizix
    Prodigy 35 points

    Thank you for your reply.

    How do I send you a friend request?

    My setup looks like the image attached.

  • 0 in reply to Mira Sibai
    TI__Guru 54320 points

    Hello Mira,

    On a post made by the party you want to friend, hover over their name where it says posted by "user name".

    A box will appear and one of the items will say "Add as a friend".  Click on that and send or modify the message and then hit send and your "Friendvite" will be sent to the user.

    After a friend has been added you can start a private conversation.

    Fizix

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Hello Sanjeev,

    I am still struggling on DLP5500 for 8 bit gray inage display with fixed on illuminator. You said DLPC200 is designed to use the illuminator for 8 bit gray scale, but is it possible to obtain native 8 bit scale with a reduced frame rate? Or any other methods will be welcome. I also want to know newer products would support this without controlling illuminators. Yhank you in advance.

  • 0 in reply to user3771403
    TI__Mastermind 30875 points

    Hello user3771403,

    This is expected behavior.

    You may want to note that on DLP5500/DLPC200 chipset offering the system is designed in such a way that, it expects that both Illuminator and DMD are modulated to generate a proper grayscale. This also means the Illuminator characteristics (both LED Driver and LEDs) should have 2-4 us switching time i.e., ON to OFF or OFF to ON response to LED_EN signals coming from DLPC200.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Thanks for quick response. Then isn't possible to get linear grayscale even if I reduce the frame rate siginificantly, such as 10hz? And also would like to know if other products have yhe same design or they can generate native grayscale without modulating illuminations. Thanks!

  • 0 in reply to user3771403
    TI__Mastermind 30875 points

    Unfortunately not.

    The entire DLPC200 display sequence assumes both DMD and Illuminator are modulated, so this applicable to all the frame rates 6Hz to 700Hz 8-bit grayscale.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Thank you Sanjeev, then how about if I reduce the bit depth like 6 bit? Can I get a linear grayscale for 6 bit depth? I also wonder if this issue is same for other DLP controller such as DLPC300 or later versions? I hoped to display 8 bit grayscale images on DMD with DLP5500 but the truth is very frustrating. Please let me know if there is any option to get this goal. 

    Best regards, 

    Yun

  • 0 in reply to user3771403
    TI__Mastermind 30875 points

    Hello Yun,

    As you know DLPC200 currently supports 1-bit and 8-bit patterns only, so 6-bit is not an option at this time. Even if 6-bit pattern supported, the answer would be again NO at this point of time.

    We have noticed the limitation in DLPC200. We certainly want to make a note of it and bring this notice to our design teams.

    If you were to use DLPC200/DLP5500 the only option to develop new display sequence where illuminator modulation is not taken into account, for this we need to invest time in implementing this feature and effort.

    We would like to know if you working on any product plan, planning to take this into market, the reason behind such question is to justify for effort on our side. Otherwise it will be hard for us to implement in short time. I hope you understand.

    In another context,

    Yes DLPC300 and DLPC350 have option to display the grayscale by keeping illuminator continuously ON.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Thank you for your reply. 

    I've concluded that the DLP5500 with DLPC200 is not going to work for my project. I'm a bit disappointed that the spec sheet from TI and supports from Keynote photonics because I thought I could display 8 bit grayscale images that was described and replied from TI and Keynote Photonics. I wasted my big investment (>$4000) and should find out how to solve it. 

    Recently I happened to find out LightCrafter 6500 & 9000 are released from TI and some other design houses. Those kits are using DLPC900 and I guess the controller can display 8 bit grayscale via HDMI connection with fixed-on illuminator? The spec sheet describes it can display 8 bit grayscale at about 240 frames per second, but I'd like to confirm the frame rate was calculated with illumination modulation or not. 

    Thank you in advance. 

    Regards, 

    Yun

  • 0 in reply to user3771403
    TI__Mastermind 30875 points

    Hello Yun,

    We want to let you know that we are indeed taking it seriously to add such a capability in DLP5500/DLPC200 chipset in near future. But we will not be able to provide the rough date about its availability. 

    Yes, we confirm that on DLPC900 the frame rate on it is calculated without taking illumination modulation into account. So the 240Hz is just with the DMD modulation, you can keep illumination ON all the time.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Hello Sanjeev,

    I really appreciate your prompt answers. If you add the native 8 bit grayscale capability to DLPC200/DLP5500, can I use it my current board or do I need to get a new board? 

    And I am considering getting one of LCR6500 or LCR90 soon. Do they support 60 Hz RGB 8bit display via HDMI without illumination modulation? Just wanted to make sure that the actual implementation is supporting the full capability of DLPC900. Lastly which DLP package type comes with LCR6500 between two package types of DLP6500? 

    Thank you in advance.

    Best,

    Yun

  • 0 in reply to user3771403
    TI__Mastermind 30875 points

    Hello Yun,

    If you add the native 8 bit grayscale capability to DLPC200/DLP5500, can I use it my current board or do I need to get a new board? 

    [Sanjeev] You don't net to get a new board. You can still use the old board.

    Do they support 60 Hz RGB 8bit display via HDMI without illumination modulation? Just wanted to make sure that the actual implementation is supporting the full capability of DLPC900.

    [Sanjeev] Yes.

    Lastly which DLP package type comes with LCR6500 between two package types of DLP6500? 

    [Sanjeev] DLP6500FYE 

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Intellectual 310 points

    Thank you so much Sanjeev, 

    It sounds great that I will be able to use my current system (X3-PM55 from Keynote Photonics) for native 8 bit grayscale display in near future. Hopefully it will be released soon. 

    Best, 

    Yun