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Is it normal condition of DLP 4500 when display black image?

Fred Kim
Prodigy 50 points
Other Parts Discussed in Thread: DLP4500

Dear all,

I'm facing kind of light leak with DLP4500.

I want to use only blue LED and try to display nothing with a black image(jpg file).

However, right side of projected plane is slightly illuminating with the black image shown as below.

Do you know any solution to minimize it like calibrating?

Does DLP4500 Model have similar output condition with black image?

Your help will be great.

  • 0
    TI__Genius 10495 points
    Hello Fred,

    I moved your question into the forum for the DLP4500. The group can help you better with question for the DLP4500.

    Best regards,

    Nadine
  • 0 in reply to Nadine Estermann
    TI__Mastermind 30600 points
    Hi Fred,

    Sorry you're having trouble. There seems to be a lot going on here. In video mode, you're trying to display a dark image but you've set the LED current as high as it will go? This could be causing the problem.

    I would recommend trying what you want in pattern sequence mode and seeing if the light leak still occurs. It is possible that there is a light leak in the optics, but the way this device works relies on modulating the LEDs, so by setting the current all the way up, you may be finding an edge case that the system was not designed for. I'll try this on my own Lightcrafter and see what I get.

    Can you detail for me what you'd like to do with your Lightcrafter?

    Thanks,
    Paul
  • 0 in reply to Nadine Estermann
    Prodigy 50 points

    Thank you so much.

    I'm not familiar with this TI forum so I posted my question at improper location.

    I will check forum with my next quote. 

  • 0 in reply to Paul Goedeke
    Prodigy 50 points

    Hi Paul,

    I'm using the Lightcrafter for DLP type 3D printer so light leak will cause bad quality of product.

    I tested it in pattern sequence mode and same problem was occurred.

    Right edge of projected plane surly illuminates when a black image is displayed.

    I think it isn't about operating mode but contrast.

    I can see weak illumination at not only the edge but also the rest of area with black image.

    If you know characteristic of contrast, could you let me know?

    I want to see none-illumination when black image is displayed like turning off the "light engine".

    Thank you for cooperation.

    p.s.: I have to use ONLY blue LED.

  • 0 in reply to Fred Kim
    TI__Expert 3240 points

    Hi there, 

    Paul asked me to look at your question. I was able to somewhat replicate your error. My display did not show leaking from a particular side, but I could still see the blue haze  when displaying a black image.  

    The best solution I can offer is to control LED enable signal. This will allow you to flip the blue LED from off to full power. It will not matter what image is is being displayed, the output will be dark. You can control the LED enable signal in the GUI by changing the LED selection option to manual mode. Checking the blue box will enable the blue LED. As seen in the image below.

    . 

    Hope that helps,

    ~Danny W

  • 0 in reply to Danny White
    Prodigy 50 points

    Hi Danny~

    I think 'haze' you mentioned is same with 'illumination' I mentioned.

    Do you have any idea to solve this trouble?

    I want to use only blue LED at full current without haze.

    Blue light is always turned on when operating.

    I'm using DLP4500 for 3D Printer so that kind of haze is very critical.

    There must be no light haze at black area of the monochrome image.

    Even haze makes material harden at unwanted area. 

    Your help would be great.

    Thanks in advance.

    p.s. : Normally 3D printer use only monochrome image.

  • 0 in reply to Fred Kim
    TI__Expert 3240 points
    I believe I do understand your issue. The optics on the LightCrafter 4500 are designed for generic evaluation uses, so some "light leaks" might occur. Even so, the preferred method displaying a dark screen is to utilize the LED enable signal. This will allow you to use the blue LED at full current and get completely dark images quickly. The monochrome images should not be an issue. This functionality is still available in video mode. I do not think it necessary to have the LEDs on all the time. Is there a reason you want the LEDs on all the time, even you want a dark images?

    I will be doing some research on the 3D printing specific application, but I feel like utilizing the LED enable functionality this is the best solution.

    Let me know if you come across any other issues.

    Best,

    ~Danny W
  • 0 in reply to Danny White
    Prodigy 50 points

    Dear Danny,

    Firstly, I appreciated your reply.

    It is very helpful to under stand more about LightCrafter 4500.

    Besides "light leaks" I have some issue about imbalance of illuminance.

    It means that I can see differences of brightness on projection plane when it turns on with whole white image.

    I measure it with UVmeter of USHIO. 

    Do you know any control method to compensate its imbalance by adjusting each pixel's PWM rate separately.

    I want to make it with system file(.ini) and than put it in flash ROM.

    If you have any idea, please let me know.

    best,

     

  • 0 in reply to Fred Kim
    TI__Mastermind 30600 points
    HI Fred,

    If you're worried about imbalance across the scene, you could perhaps create an image which compensates for that imbalance by having a gradient of values.

    For instance, if one edge of the frame is brighter than another, you could assign an intensity value of 255 (full on) to the darker edge and then some lower value to the brighter edge. The Lightcrafter is pixel accurate meaning that the exposure will be exactly what you set it to be. This method will require you to use more than binary images however (8bit if you use my example).

    If you're looking to compensate the imbalance regardless of what image you display, I don't believe that there is any method you'll be able to use. Any imbalance in illumination is likely due to the optics and as Danny mentioned, these optics are for general evaluation and not necessarily intended for specific purposes and may have some inconsistencies.

    Thanks,
    Paul