Part Number: DLP6500FYE

Hello, I would like to ask a question. In the above video, I hit the light on the DMD, and I have rotated the DMD by 45 degrees, so that the micro mirror is under the white and black mask, and the light spot is deflected on the same horizontal plane, but I After the white image is imported into the DMD, the micromirror should be deflected by +12°, and the light spot is to the left. When the white image ends to the black image mask, why is there still light intensity in the original white image direction? It should not be -12°. Deflection, there is no light intensity at +12°? I want to use a detector to receive the light intensity in the white image direction, but when the white image ends to the black image, there is still light intensity in the white image direction, and it will be collected. It will all be high level, not high and low levels separated, so I would like to ask this question, thank you

  • Hi shiqi zhou,

    Let me check with my team and update on this.

  • Hello Shiqi Zhou,

    This is expected behavior.  A couple of things are happening here.

    First, how are you getting your patterns to the DMD?  Are you in Patter On-the-Fly Mode or Video Mode? 

    Regardless, there is a small amount of energy in the diffraction pattern that remains even when the mirrors are "off".  When you are looking at the diffraction pattern rather than the re-imaged surface of the DMD (like in a projection system), It is very much easier to see this small amount of light that remains in the diffraction pattern.  You may need to set a threshold value that represents off and on.  The collected light should be fairly different in intensity.


  • Hello Fizix
    Thank you for your reply. This black-and-white image is generated by MATLAB. Is the image required to be a binary image? What is the impact? The mode is Patter On-the-Fly, is there any GUI interface update component for this threshold setting, but after I cast the white image mask, when I switch to the black image, what is the weak light intensity and the light intensity position in the white image? Same, what is the reason for this? Thanks, and look forward to your answers.
    Shi Qi Zhou

  • Hello Shiqi Zhou,

    Please try sending the White and Black images as 1-bit images to see if this changes the behavior.  If you send a 1-bit "all off" pattern to the DMD and loop it, does it still show the pattern.

    I think you misunderstand about the threshold.  That is something you would set in your measurement system to determine "on" vs "off".

    It is not possible to completely get rid of the off state diffraction pattern.

    Please let me know the result when you use 1-bit patterns in Pattern On-the-Fly Mode.  Be sure to set your dark time to 0.

    Can you send a screen shot of your Pattern Mode/Pattern Design page for the pattern(s) you are running?


  • Hello Fizix
    Thank you for your reply. The above picture is my operation interface. It is a black and white picture of one bit, and the interval is set to 1 second, and the projection is cycled. However, regardless of the white picture and the black picture, there will be weak light intensity on the left and right sides, for example, on the right. In the projected black image, the light exits at an angle of 24 degrees to the right, but after the black image is projected, there will still be a little light intensity at the original position, and the pattern can be seen like a micro-mirror shape, that is, this weak light intensity is diffraction Is it? Want to know the reason for this.
    2. Is this on and off setting for the DMD micromirror? It’s a bit unclear for what you said to set the value in the measurement system. Could this weak light be caused by the fact that the laser and the DMD are in the same straight line? It is not necessary to pass the laser light through a mirror and then project it on the DMD. Looking forward to your reply.

    shiqi zhou

  • Hello Fizix
    I have another question I want to ask, is there any requirements for the size of the light spot on the DMD device, such as full coverage or intensity requirements, will it have an impact? Looking forward to your reply

  • I am saying that there will always be some residual diffraction even in the off state.  This is a property of diffraction and will be true for all diffraction gratings.  Changing the tilt (on or off) does not change the location of orders, only the energy distribution in the orders.  the energy in the orders that are bright when all the mirrors is on will change, but will not completely disappear.  When you are re-imaging the surface of the DMD (such as when you make a projector) this light will be low on the projected image.  It is this low light when compared to the on light that determines the contrast ratio.

    Regarding a setting, this is not a setting of the projector.  Simply something you will need to characterize.  When all off what is the amount of light that gets through?  

    The size of the light spot depends on how much power is in the spot.  If lower power is used it will not matter much.  If high intensity light is used, this will effect the array temperature where the spot is.  What power level do you anticipate and what spot size?

  • Thank you for your reply, which means that even if it is closed, there will be weak light in the open direction, which is unavoidable due to the diffraction characteristics, but compared with open, the light intensity and luminous flux are different. The energy is different, is that so, thank you very much.
    1. Regarding the size of the light spot, should the micro-mirror surface be wrapped, but for the part that exceeds the working mirror surface, I think it cannot be more than 10% in the manual. Is it possible to make the light spot too large? Our expected size diameter is 2cm , In theory, should the intensity of the light spot be guaranteed to be consistent? What effect will this have when it is illuminated on the DMD? Thank you for your reply, the previous explanation has gained me a lot.

  • Hello Shiqi,

    In general unless you use a spatial light filter, a laser spot will be approximately Gaussian in distribution.  If the 2 cm is FWHM then there will be energy outside the DMD array.  How much power do you expect in the beam total?