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DLP4500: display visual patterns.

May
Genius 9880 points
Part Number: DLP4500

Hi Team,

Good day, we received inquiry regarding DLP4500. I'll copy the customer query below.

"I am generating the patterns using a custom toolbox on a 0-255 (8 bit image) scale, and then sending the images via the HDMI cable to the DLP. I am operating the DLP in video mode.What I have noticed is that for a black image (0 on a 0-255 scale), the DLP is not producing a dark image, but rather a pretty bright image.The brightness goes up not surprisingly, when I send a white image (255 on a 0-255 scale.The issue is that because the minimum brightness is high, and the increase in brightness from a dark to a bright image is not that high, I am getting a pretty low contrast image.For raw number, I measured, 0.21uW on a photodiode for a black image on the Green LED and 0.57uW for a white image on the Green LED (with current values in LightCrafter GUI set to 0 in both cases).The only time I saw the screen go dark (and measured power to go down to nW range) is when I uncheck the LED boxes under Manual Mode in LightCrafter GUI - which seems to turn off the LED.

These 2 images were obtained by setting the background to 0 (black screen) and to 1 (bright screen) and setting the current values for the LED 1 to 0 under manual mode. The image is only a qualitative indicator of the brightness as seen through the camera. The absolute brightness measurements are what I stated in my previous email. I'm also attaching a screenshot of the modes under which the GUI is being operated.  Please see attached file. DLP4500.zip

Thank you and looking forward for your kind response.

Regards,

Maynard

  • 0
    TI__Genius 12785 points

    Hello Maynard,

    Welcome back to the E2E forum.

    There a couple of questions that may be helpful in our support:

    1. Can your customer confirm that the video source is operating at full dynamic range?

    2. Can your customer get an oscilloscope plot with a photo-detector on the poor contrast black image?

    Regards,

    Austin

  • 0 in reply to Austin Snyder
    TI__Genius 9880 points

    Hi Austin,

    Thank you for your support. I just received information that customer already resolved the issue. Below is the information provided.

    "I have resolve the issue myself. The brightness of the image is set by the time the DMD spends in the on state versus the off state. As the image gets darker at the same value of LED current, the DMD should be spending more time in the off state than in that on state, which it wasn't. This resulted in a much higher brightness for dark images, and consequently a very limited dynamic range of contrast. I think this requires a repair of the LED light engine circuit. Please communicate this information to your engineers so it may help others in the future who may encounter a similar issue."

    Regards,

    Maynard

  • 0 in reply to May
    TI__Mastermind 28005 points

    Maynard,

    Thanks for the update. We are glad to hear the customer has resolved this issue. We will communicate accordingly.

    Regards,

    Philippe Dollo