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Why does the captured fringe pattern from the reference plain have uneven intensity

Xinjun Zhu
Prodigy 170 points

Dear all,

 

I use LightCrafter 3000 to project sinusoida fringe pattern on a reference plain, the supposed captured fringe pattern should be  sinusoida. However, I get the fringe pattern using CCD and find that it has uneven intensity. So could you give some advice on this?

Best wishes.

The following figures are the simulated fringe pattern, the captured fringe pattern by CCD and  one column of the captured fringe pattern.

 

 

  • 0
    TI__Mastermind 30875 points

    Hello Xinjun,

    If you look at the LightCrafter optical engine specification from EVM user's guide document the ANSI contrast ratio is 43:1, there will be minute variation in the intensities across the screen. This could be one cause.

    Another thing, the projector is 608x684 resolution, I see your capture image is 1280x1024, there is mismatch in the aspect ratio of both sensor chips, so I am guessing the sinusoidal fringe capture may not  of entire projected image, so based on where you have focused you might see slight variation. 

    You can try capturing entire projected fringe image and look at the intensity variation.Also try focusing at the center of the projected image and see if you can improvement.

    Regards,
    Sanjeev

     

  • 0 in reply to Sanjeev
    TI__Expert 4720 points

    Hello Xinjun,

    You may be observing uneven lighting across the DMD as well. Try projecting a solid white pattern and measure the intensity across the image. This could provide some calibration information for your application to account for the intensity differences across the image.

    Regards,

    Blair