How the pixels are interpolated using DLP3000 HDMI mode

Ruonan Yang

I am using DLP3000 HDMI mode to display image. The native 608 * 684 input resolution pattern has a one-to-one association with the corresponding micromirror on the DLP 3000. But when I upload a 608*684 pattern to the DLP, the pattern is stretched, i.e. a circle will become ellipse. I searched through the forum and found this thread : https://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/advanced_light_control/f/850/t/170877#pi239031349=1

I know that DLP uses diamond pixel configuration but I am still confused how it stretch the image. The center to center distance of between adjacent pixels should also be equal, which means if I upload a 4*4 square, the appearance on the DLP should also be square.

I noticed that the DLP3000 support 864*480, the aspect ratio is similar to what I saw on the DLP. I wonder how 608*684 mirror array produces 864*480 resolution image.

Thanks!

Ruonan

over 7 years ago

0 Paul Goedeke over 7 years ago

TI__Mastermind 30600 points

Ruonan,

It has to do with how the rows and columns are numbered when you take a rectangular 608*684 image and display it as a diamond image. The graphic below shows this:

Basically, each column is now two "corner-to-center' distances apart, whereas the rows are only 1 "corner-to-center" distance apart. This causes the stretching that you see.

Hope that is clear!

Paul

0 Ruonan Yang over 7 years ago in reply to Paul Goedeke

Prodigy 80 points

Thank you for the reply! I wonder is there a way to correct the stretch. Or is there any product using the orthogonal pixel array so that I can display the image as it is?

0 Paul Goedeke over 7 years ago in reply to Ruonan Yang

TI__Mastermind 30600 points

To get orthogonal pixels you'll have to use the DLP6500. There is an EVM for this device but it doesn't come with optics.

What I would recommend is opening up an image editor (MS Paint or similar) and simply making your horizontal features half as wide as you'd like them to be. Basically any method you can think of to correct the image before it is projected. That will result in a correct image when on the screen.

0 Ruonan Yang over 7 years ago in reply to Paul Goedeke

Prodigy 80 points

Another question: I found that it appears square when I use micro-SD card to display an 608*684 image, it appears square and part of the DLP is not active, as shown in the picture below. It seems that it follows another rule to display an image. Do you know how it works when using micro-SD card?

0 Ruonan Yang over 7 years ago in reply to Paul Goedeke

Prodigy 80 points

Thanks for the suggestion! I will try it!

0 Paul Goedeke over 7 years ago in reply to Ruonan Yang

TI__Mastermind 30600 points

I haven't seen that behavior before. What resolution images are you providing from the SD card? Can you give me a little more detail?

* Are you only loading images from the SD card?
* How many images?
* What file format?
* Are you also booting from the SD card?

0 Ruonan Yang over 7 years ago in reply to Paul Goedeke

Prodigy 80 points

The image is 608*684.

1. Yes, I am loading image from the SD card
2. almost 10,000 images
3. bmp format
4. Yes. Actually the SD card works well. But the smallest time interval is only 1 second. I need to make the image upload faster so I turn to the HDMI mode.

0 Paul Goedeke over 7 years ago in reply to Ruonan Yang

TI__Mastermind 30600 points

Hi Ruonan,

Can you read the following threads? Make sure your DM365 FW is updated:

e2e.ti.com/.../208000
e2e.ti.com/.../274297

Hopefully these help!
Paul

0 Ruonan Yang over 7 years ago in reply to Paul Goedeke

Prodigy 80 points

Thanks!!

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How the pixels are interpolated using DLP3000 HDMI mode