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DLP9000XUV: How to realize "Smooth" projection of grey scale pattern

Part Number: DLP9000XUV

I am working on a DMD kit constructed by ViALUX (V-9001 UV), in which the DMD chip is DLP9000XUV. While I created a grey scale pattern for test (4x4, see below) and displayed it (only one frame, illuminate time = 4s, 8-bit, other settings are default), dynamic stripes appeared instead of expected static pattern.

I have heard that DMD realize grey scale display via tuning the duty ratio of on/off states, that is, the mirror will flip rapidly but overhere it is not that fast. Can you please let me know the reason and how to achieve a "smooth" or uniform grey scale display?

Also, our final target is flawlessly projecting a series of pictures/patterns in sequence with different illuminate time (~min for each picture) for photopolymerization. But it seems the project setting can only be tuned on SEQUENCE level, not on FRAME level, is it correct? Do you have any suggestions to achieve such a common function? Thanks!

  • Here is the test video:

  • Hello Zhiguang,

    This is the correct behavior.  If the frame time is 4 s the the MSB will show for 2 s, the MSB-1 for 1 s, the MSB-2 for 0.5 s and so forth until the LSB will display for 15.6 ms.  If you project this on to a static surface that you are attempting to polymerize over the 4 seconds, each patch will receive the correct dose.

    If you wish this to look smooth to your eye, you will need to make the frame rate much faster so that your eye integrates the patterns to a smooth image.

    If you need it to look smooth to the eye and expose for 4 s, then you will need to show the frames at a fast enough frame rate, but show the image enough times to reach 4 s.

    The patterns you are seeing are called "bit-planes", where an n-bit image is divided into n "bit-planes" that are binary values.  

    There are quite a few good discussions on the internet about this.

    Fizix

  • Hi Fizix,

    Thanks for your quick reply.

    Do you mean we should short the illuminate time for each frame but repeat it until reach the required time?

    I want to know in which file I can find description of the logic to achieve this gray scale display as "If the frame time is 4 s the the MSB will show for 2 s, the MSB-1 for 1 s, the MSB-2 for 0.5 s and so forth until the LSB will display for 15.6 ms." I think it would be very helpful to adjust the setting.

    Now I am using C++ code to control the DMD. I am wondering if there is a control software for my DMD, like GUI or other common used software.

    Zhiguang

  • Hello again Zhiguang,

    This controller does not have any code for grayscale.  This has to be an ViALUX implementation.  You will need to contact them about how to control this.  

    If all you are interested in is that the light dosing is correct, then you can simply let it display the way it is.

    Fizix