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Projector Calibration/ Lens Distortion

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  • Bhatt Himanshu
    Hello, I tried several prints and came to conclusion that in my setup i get good prints in the middle area of my Build platform. for testing i tried rows and
    Message 1 of 39 , May 19, 2013
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      Hello,
      I tried several prints and came to conclusion that in my setup i get good prints in the middle area of my Build platform.
      for testing i tried rows and colums of cylindrical support structure. from 0.9mm to 0.4 mm in diameter. first few prints, it dint print support structures bellow 0.7mm. then i increase cure time upto 30 sec. now i got 0.4 but only in the middle same structures on the left or right side of projectors are broken or not printed. at the Cure time of 30 sec i can use 25mm Build platform for supports up to 0.4mm but now the problem is in HOLES i didnt get the small holes of 0.4mm diameter which i was gettting earlier @ 18-20 sec cure time..
      after searching on google i found this
      http://www-bcf.usc.edu/~yongchen/Research/SFF_09_DLPCalbration.pdf
      they resolve the problem using hitech algorithms .

      I can print Idols, Yoda, Coins easily with great details but fine jewellary makes the problem coz in that i need both holes and small support structure (easily removable).

      Here is my setup details.

      2800 Lumen Benqmx518
      50um XY resolution
      38um Z resolution
      Software: B9C
      Resin : B9R Red

      I am thinking to use grey scale in problematic area. but for that i need extensive trials. if you guys have clever calibration process please share..

      if you guys faced same problem than please share with me.
      Thanks,
      Regards,
      Himanshu Bhatt
    • Graham Stabler
      ... The reason I suggested a diffuser is because I was talking about converting a camera into a sensor so the image you get is actually an average of the
      Message 39 of 39 , May 23, 2013
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        On Wed, May 22, 2013 at 11:32 PM, Bhatt Himanshu <bhatthimanshu@...> wrote:

        @Graham
        I read about ND filters and i think i can get it from local camera shop. Do i need diffuser if i use ND filter/filters properly. 

        The reason I suggested a diffuser is because I was talking about converting a camera into a sensor so the "image" you get is actually an average of the light hitting the sensor. The idea of an ND filter is just to reduce the light levels though as I mention on another thread you can do this by projecting darker images anyway I think. 

        I want to make it clear that I am not suggesting trying to measure the output of a specific pixel on the projector but rather to get the average intensity over a fairly small area (because crappy webcam sensors are tiny) and then use a grid of these measurements to produce a correction which should be fairly smooth if the aberration is only caused by the optics.

        Cheers,

        Graham
         
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