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Original question:

DLP4500 IMAGE DISTORTED

DLPLCR4500EVM: DLP4500 IMAGE DISTORTED

Saad Idrees
Prodigy 140 points
Part Number: DLPLCR4500EVM

In reference to the post:
"The image is distorted vertically by 1/sqrt(2) and horizontally by sqrt(2).  This effectively makes a square (1:1) come out (1:2) - i.e. is stretched in the horizontal direction by a factor of two relative to the vertical. What you need to do is generate an image that is "pre-distorted" by a factor of 2 vertical direction.  In other words make the "squares" in the image you feed to the DLP4500 twice as high as they are wide.  When you feed this in, the result will be an image whose squares are (1:1) - i.e. really are squares."

If I want to create a square with a specific dimension when projected onto a screen, I then need to pre-scale the image in both horizontal and vertical direction right? Scaling by a factor of 2 in vertical direction will only make the squares (1:1) but the overall dimension is still not what is expected? Just to confirm.

Thanks

Saad

  • 0
    TI__Mastermind 28005 points
    Saad,

    I do not believe that is the case. Due to the shape of the DMD, I believe you only need to double the height of the pattern to achieve the desired result. See the post that follows:

    "The apparent distortion is a consequence of the way the columns and rows are mapped on a "diamond" device. Although there are other ways that it could have been mapped, this way was chosen to make the DMD circuitry similar to DMD on an "orthogonal" device.

    The following two threads have a discussion of this:

    e2e.ti.com/.../1119954

    e2e.ti.com/.../1588635

    I hope this helps."

    Best Regards,
    Philippe Dollo
  • 0 in reply to Philippe Dollo
    Prodigy 140 points
    Hi Philippe,

    I ran a quick test. I created a 100 x 100 orthogonal pixel square. At 1280x800 resolution this was 5.7 x 5.7cm on my screen. At 912x1140, this was 8 x 4cm. So the horizontal dimension multiplied by sqrt(2) and and vertical dimension divided by sqrt(2).

    In horizontal dimension, 1280 orthogonal pixel maps to 912 diamond pixels. Because of diamond shape of mirrors, each pixel length will be multiplied by sqrt(2) and hence the overall image in horizontal dimension is stretched by factor of sqrt(2). With the vertical dimension however, 800 orthogonal pixels maps to 1140 diamond pixels. So in this case the image in vertical dimension is squished by a factor of sqrt(2). The relative ratio between horizontal and vertical is therefore 2.

    What do you think?

    Best,
    Saad
  • 0 in reply to Saad Idrees
    TI__Mastermind 28005 points
    Saad,

    That seems to align with my knowledge of the part. Thank you for sharing.

    Best Regards,
    Philippe Dollo