Until now, this is a good idea using large scale of LCD panel and integrate this with your car windshield.
If you type LCD Windshield, most articles are old. As the time went by, portable / foldable LCD panel is no longer far from us. Thus, we can re-exam this idea see if it’s possible to DIY.
1. A EeeBox / Thin system on your car.
2. A high-resolution/IR(Night Vision) equipped camera/webcam.
3. A Large Panel of LCD (Not necessary to cover the whole windshield, the upper and right part are the most useful location)
4. A software that will keep tracking and calculating the effect to the driver.
The theorem is quiet simple, a tracking software will focus / capture the brightness of the driver’s face / eye, and then, generate the dark block, move it accordingly and see if it helps to change the brightness on the driver’s face/eye. If it works, keep in the location. Otherwise, keep calculating and move the block to the best location to block the light.
This idea is good when sunshine/daylight. However, at night, that would be hard to implement. Especially, any change will effect the view of the driver, which may even cause dangerous situation in some conditions.