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DLP4500: Creation of Moving light sequences with the DLP4500

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Replies: 7

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Part Number: DLP4500

I would like to use a DLP4500 to project a continuously moving line onto an object. The line may be vertical, horizontal, or diagonal. How would I be able to achieve this using the DLP4500 GUI?

  • Hello Ashish,

    You have lot's of options to achieve this. I would recommend reading the DLP4500 EVM User's guide at www.ti.com/.../dlpu011f.pdf. If it is a dynamically changing lines (i.e. you are unable to pre-upload every pattern into the flash) then your best bet might be to feed the video from a PC/frontend chip into the Lightcrafter 4500. Please let me know if you have further questions.

    Thanks,
    Kyle
  • In reply to Kyle Rakos:

    Hello Kyle,

    Thanks for your reply. I did read the documentation of the DLP4500. However, since I am new to this, I found it a little hard to grasp. From my understanding, this is how I would be able to achieve a dynamic pattern. Suppose I wanted a moving vertical line for some duration of time, I would have to create images of the line. These images would contain the lines at different locations(or columns) in the direction they are supposed to move. I would then have to flash these images as patterns in the GUI. However, I gathered from the documentation that the flash memory has a capacity for only 64 patterns at max. Is my approach valid?  If it is valid, it appears to be tedious to have to again make images (to be later fed as patterns) for moving  horizontal or diagonal lines. 

    You suggested that I could achieve this by feeding a video by using a PC/ frontend chip. Could you please elaborate on this approach. It sounds simpler to me. I couldn't make much of the feeding a video part in the document you'd linked me to earlier. I apologize if my questions seem elementary.

    Thanks,

    Ashish

  • In reply to Ashish Rao:

    Hello Ashish,

    Feeding in via the front end simply consists of sending in video via an HDMI interface (similar to streaming a video on a projector). The difficulty would be in creating a program/video content on a PC. This would depend on your implementation how you would like to do this. The DLP4500 would be agnostic to how the video was generated though.

    Could you elaborate a bit more what you are trying to do and perhaps I could help.

    Thanks,
    Kyle
  • In reply to Kyle Rakos:

    Hello Kyle,

    I have an object over which I would like to run my pattern/video. Say, I have a doll head with me and a camera of resolution 240x180,
    I would like a light pattern moving over the doll head to be captured by the camera. The pattern could be a single vertical line, or a single horizontal line or a single diagonal line. In short instead of multiple bands/lines, I would like only one band/line to move over the object through the entire frame of the camera. Also, could I extend it to make a fringe pattern move?

    Thanks,

    Ashish

  • In reply to Ashish Rao:

    Hello Ashish,

    Thank you for clarifying what you are trying to do. I think you have two options, both of which are extendable to arbitrary patterns.

    • Upload every pattern you need into flash and use internal pattern streaming mode to switch between the patterns. You can use one bitplane per pattern (so each image stored in flash will have 24 projected images). 
    • Handle all image creation and display logic on the PC and simply stream it to the projector.

    Alternatively, you could mess around with using the image Display Area and Cropped Area to try to artificially contort an image to only display the vertical or horizontal line that you want (I don't think this would work with diagonal lines or fringe patterns). This is definitely not the intended use case of this function but I just wanted to let you know about the idea (you would have to test it to see if it works).

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hello Kyle,

    Thanks a lot for your help. I've tried out the second method and it works! I didn't understand the first method for now. I'll try exploring it in detail after I am done with my task. However, I have a couple of questions about the second method (projecting using video mode)

    1) What are the downsides of using video mode over pattern mode? Video mode looks pretty universal. In both cases it is required of the user to generate their own images or videos(in case of video mode)? 

    2) What makes the video mode of the light crafter different from  a commercial off the shelf projector? I'd assumed that the lightcrafter displays blacks perfectly (no projection at all) but it turns out that I was wrong. Is there any way to make those white tinges disappear from a perfectly black background when projected?

    3) Is there anyway to tune the projector intrinsics (lens intrinsic parameters)?

  • In reply to Ashish Rao:

    Hello Ashish,

    1. If you are using the video port but still creating a pattern sequence (i.e. Pattern Sequence mode) you will still be displaying pixel accurate images (just like using the flash source). The only disadvantage would be your maximum achievable pattern rate in external mode (see Table 8 of the DLPC350 datasheet). If you are using standard video mode then you will not have 100% pixel accurate image reproduction. This may or may not be acceptable for your use case.
    2. This Lightcrafter4500 is intended as an evaluation module for light control applications. Therefore, unlike standard video projectors it will have lots of signals broken out for debugging and development. Additionally, as a light control product, it has the ability to achieve pixel accurate image reproduction (i.e. no gamma correction and other image processing) and the ability to set your own bitplanes at high framerates.
    3. While you may be able to change some of the optics, I am unaware of any predefined procedures for doing so. You can find a teardwon at www.ti.com/.../optics-electronics.html. Additionally, some of optical module makers have various versions of the 4500 for sale that may better suite your needs if desired www.ti.com/.../optics-electronics.html

    Thanks,
    Kyle

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