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Re: [diy_3d_printing_and_fabrication] Re: Projector Calibration/ Lens Distortion

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  • Graham Stabler
    ... If I were to do this with a camera I would drain my vat, place some high quality diffuse draughting film on top of the PDMS, project an image of white or
    Message 1 of 39 , May 23, 2013
      On Wed, May 22, 2013 at 10:18 PM, Bhatt Himanshu <bhatthimanshu@...> wrote:

      Now what you guys thinks/tell from your experience 16MP Nikon like camera with ND filter would do the job for whole platform or not??
      @Graham,Jon.. Please suggest an accurate/repeatable System.

      If I were to do this with a camera I would drain my vat, place some high quality diffuse draughting film on top of the PDMS, project an image of white or blue and take a picture using a camera mounted where the build platform normally is. If you also take a picture with a grid pattern projected then you correct for any distortion or use the grid pattern to decide on certain sampling points from the original image.

      When taking an *image* you will probably not need an ND filter, you could just project a gray screen because I assume all the variation will be there when there is a lower intensity anyway and besides you can just reduce the exposure.

      Graham
    • 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

        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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