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Micro photograph a TFT array

How LCD diplay electronic woks and how to photograph it.

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One day I was playing with my phone, and a drop of water landed on my screen. That little water drop formed a little microscope, so I coud see my phone screen pixels. That water started this project, because after that I wanted to look more and more smaller object on it. I desided I want to photograph what I will see on that screen. 

I work in the display industry, but I never saw with my own eyes how a screen really works. I was interrested about the electrical side of a screen, like how they could operate that much pixels in the size like phone.

Because of my work I saw some thin firm transistors on a layer of screens, and also a bit of research I knew what to look for. 

I was thinking about how to make a cheap big magnification microscope. It was not easy, but I rememberred the CD readers head has a really good optic in it. I started playing with my Iphone screen and a cd reader head, I could saw much more details then before, but that was not enough form me then. After I tried with the same optic with my Iphone 7 plus camera so I started photograph. I had a cheap chines LCD touch screen for an arduino uno what I never used for any project, so I made a sacrifice. I used the cheap screen back light to light the screen then placed the microscope optic, but the result was not the best. I only could see the red, green and blue pixels, nothing else. 

After a lot of struggle, I found out the screens usualy built from two glas layer between the liquid cristals. The top glass has black masking where they want to hide the controll circuit. That mean between two sub-pixel it is black area. The problem with this the transistors and the conbtroll lines are between thees pixels, so I could not saw them. 

Then I disassembled the screen and removed the front LED backlight and all the polarizer films from the front and the back also.

With this I coud see the transistors and the lines from the back side, but the problem was still that black masking around the pixels I tried to see from the top.

I had no chance and had to try separate the top and the bottom glas layer. It was fearly easy with a sharp blade.

Then lets see what cold I achive with this:

 Not so bad right? I achived this with a CD reader head optic a RGB led and my phone camera.

The CD reader head has a good option because it is reflective optic, so it usually has a laser what is shining down to the surface then the light comes back to a photo transistor, and that how it detect data on CD surface. This point I replaced the laser with a RGB led and I removed the photo transistor also and ther went my phone camera. 

This picture was created from several picture combination, that why it is not perfect.

Then I decided to improve the sistem by adding X - Y movement to, so I could search for interresting parts.

I had an old pen plotter what long time I was looking for where can I use it.

I modified the controll electronic with a modern arduino CNC shield, so then I can write software for it.

Also needed USB camera instead of my phone camera, so I was looking for a cheap solution and I found a usb microscope camera, I knew it is not so great, but it has magnification already and I did not needed big resolution, you will understand it later why.

 I was learning Python OpenCV  for a couple mounth so I know I will capable of controll everything from python. I wrote a little code for move the X - Y movement like a scanner head then I took pictures with the USB microscope and converted it to gray and it added it them, so then I finally could take high resolution photos like this:

 It is not so beautiful, but can be seen what needed. 

A little explanation what are you see exactly:

1: One sub pixel

2: One sub pixel switching thin film transistor.

3: Connection piont to connect the liquid cristal picel to the transistor

4: Controll line ESD protection transistors

5: Line controll line

6: Row controll line 

For easier on drawing it is looks like this:

Because the images...

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arraymatrix98.png

Samsung S8 display array

Portable Network Graphics (PNG) - 24.93 MB - 10/22/2019 at 20:15

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arraymatrix4.jpg

Samsung S8 display array curve

JPEG Image - 8.43 MB - 10/22/2019 at 20:14

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arraymatrix12.png

TFT array photo

Portable Network Graphics (PNG) - 7.95 MB - 08/04/2019 at 18:36

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  • Samsung S8+ AMOLED display under the microscope

    Máté Tóth10/22/2019 at 20:13 0 comments

    Microscope picture:

    I asked a local mobile screen repair shop if they may have some damaged LCD or OLED screens for my research, and they said yes and gave me several Samsung S8 and S8+ Amoled screens for free. (Big thanks for the shop manager.)

    As I found out these screens are really good and it looks like Samsung has way more experience over other display manufacturals that is insane. I choose the S8+ display to show, because the regular S8 screen has smaller pixels.

    The S8+ display has the following parameters:

    6.2" Quad HD+ Super AMOLED (2960x1440)
    529 ppi

    It is verry interresting under the microscope, it has a lot of details what I even could not see, because my home made microscope resolution was not good enough.

    So lets see how the pixels looks like when they light up:

    As you see Samsung used  the Diamond pentile matrix. You see some color sub pixels are smaller or bigger. On LCD displays usually every pixel has 3 sub pixel, one RED one GREEN and one BLUE. In this case a full pixel has multiple sub pixels from each color, like one pixel has 4 green sub pixel.

    I am not exactlly sure what is the benefits for this kind matrix, what if I have to guess these AMOLED screens hase much better color accuracy and the pixel will have much homogen light.

    The sepatrated TFT+OLED layer from the front glass+touch layer:

    Now lets see the screen under the microscope:


    This picture was made from several little picture stiched togedher, each picture around 400 x 400 pixel, and the over all picture size is 5720 x 13760 pixel. The over all size is so large I could not upload it to this tread, only just to the download section, so if you are interrested in  the full size pictures, please download them from the download section above.

    Because of touch layer is top of the TFT and OLED layer I had to separate the two layer of the display, so it destroyed it, but it give us the main part what we came for.

    The lines what you are seeing is the electrical trace which are controlling the sub pixels to light. The bigger rectangle is the BLUE sub pixel, the smaller rectangle is the RED subpixel. The GREEN pixel is quite different, it has a round shape. 

    The picture was taken from the bottom of the diplay edge, where the control lines leave the screen on the right.

    The organic layer is sitting top of the TFT layer, so you actually can not see the TFT very clearly. If you are looking closely you will find some little round dots on the lines in the middle those are actually the transistors and active parts.

    The Samsung displays has round edges on the corners, I made a little picture from it, when it is actually starting to "turn" round. You can see on the below picture, it is just missing one horizontal subpixel line from the middle and thats how it starts. 

    I am still working on the improvement of the picture quality, but it is not so easy anymore, because if you just calculate how big those lines on the pictures are, you will find out those are actually not bigger than 10-20um possibly it is closer to 10 microne, so pretty small.

    I hope you find interresting this short article. Please go to the download section for the original size images.

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Alan Green wrote 08/04/2019 at 23:32 point

This is very cool. Thank you for documenting and sharing.

What are the lighter areas with the rows of 6 darker circles?

  Are you sure? yes | no

Máté Tóth wrote 08/05/2019 at 06:13 point

The lighter area in the midle, is shoud be ground. The circles are inner layer connection.

  Are you sure? yes | no

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