Patrick Bader's Blog a blog about software development

7Sep/102

it’s about time…

I finally finished my Master's Thesis about GPU based image processing in the context of a multi-touch application. As I wrote in older posts I have built a prototype of an LCD based multi-touch screen. The PlayStation Eye camera is used to track blobs and fiducials using IR light and the images from the cam are processed on the GPU to extract positions, IDs, etc. For the implementation which will possibly be published in a later post, I used OpenCL, which allows programming on various heterogenous hardware. The visualization is done using solely OpenGL 3.2 Core Profile.

The thesis in in german and can be downloaded here. Feel free to read and comment it.

23Jan/1024

Adjusting screen brightness with shortcuts

A while ago I installed Windows 7 on my Sony laptop. The good thing about it is it runs quite stable and most things just work. The bad thing some of the shortcuts with the blue "Fn" key don't work anymore. Adjusting the volume works perfectly fine, but setting the brightness of the LCD backlight does not.
Since Sony is not going to release any Windows 7 64 bit drivers for my model, I finally decided to write a little programm myself. This took several hours of searching for the right API to use. There are actualy three different ones:

  1. The first API I tried is called the Monitor Configuration of the Win32 API but did not work for my laptop (some kind of I2C transmission error occured)
  2. The Backlight Control Interface using IOCTL was the first approach that worked for me, but getting the current brightness is not supported on newer Windows versions
  3. So I ended up using WMI which is available for .NET and works surprisingly quite well.

Further usage information and a downloadable binary can be found on my Projects page
If you encounter bugs or have any suggestions please do not hesitate and give some feedback.

19Nov/092

LCD Disassembly

Quite some time passed since my last post. If you were wondering what I was doing in the meantime and why news took so long, read on.

After the successful testing in my last post, I wanted to try the whole thing on with an LCD. The problem with that was how to get one. Luckily my brother has an old Sony SDM-S71R with 17" which is not needed anymore. It's not really big, but for a first test it will do.

Disassembling the whole thing was quite easy, only the first part, getting the plastic casing off, was a bit tricky. If you are unsure how to do it, search online for 'Sony SDM-S71R Service Manual'. After removing some plastic and metal casing two circuit boards will be revealed. Both of them shown below:

Power supply of the Sony LCD

Power supply of the Sony LCD

This one is the power supply for both the electronics controlling the LCD and the four fluorescent tubes for the backlight. Since I do not want to use the original backlight I do not need the high voltage part. That made me look for some alternative to the power supply. The pinout of the connection to the lcd controller is described directly on the board and is shown below:

Wiring of the connector from the LCD power supply to the controller

Wiring of the connector from the LCD power supply to the controller

The purple, grey, white, and black cables on the right need not be connected. So there are only the +12V, +5V, and ground wires left. These voltages are also used in computers, so the choice was easy: I used the power supply of an old PC.

Next is the controller board:

lcd_controller_board

Nothing exciting here aside from the many wires on the right that go to the display itself.

The display consists of the LC layer on top of a glass plate and the backlight with some plastic films between them. Again some pictures of the parts ordered top-down:

LC Layer with controller

LC Layer with controller

Diffuser with some other plastic films on top of a plastic panel and a white paper

Diffuser with some other plastic films on top of a plastic panel and a white paper

Fluorescence tubes that shine from the side into the plastic panel

Fluorescence tubes that shine from the side into the plastic panel

These are the most important parts of the LCD. If you have any questions about the disassembly, just ask.

So much for the LCD disassembly. I've already done some testing with it in combination with a self-made backlight, some IR LEDs, and a bandpass filter for the camera. But this will be the topic of the next post,...