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DLPLCR9000EVM: About the self-imaging phenomenon of DMD

Jihee Ryu
Prodigy 60 points

Part Number: DLPLCR9000EVM

Hi. I am using DLPLCR9000EVM with 1 pixel line image. 

like this...  

on on  on on on on 

off off  off  off off off

on on  on  on on on

.

.

.

The problem is, I found the repeated focusing phenomenon when I observe the dmd pattern.

My optics was just like this. 

dmd >> Lens 1 >> Iris >>  Lens 2 >> camera

camera is on the image plane of dmd, and lens 1 and lens 2 makes the 4f system. 

When I move the camera, the pattern disappeared and appeared again. 

Someone says to me, it looks like talbot effect. 

I wonder it's right or has any other name.

Thanks. 

Kind Regards, 

Jihee. 

  • 0
    TI__Mastermind 43165 points
    Hello Jihee,

    This sound to me more like a spatial coherency issue. If the pixels of the DMD are nicely lined up with the pixel of the camera you get an image, but when moved a little they line up with the space between the camera pixels and give you a reduced output.

    Beyond that, without some pictures or images from the camera, I do not have an answer.

    Fizix