Our friend Arild has a nice post in his own blog about the effects of using polarized sunglasses in combination with the HUD display of his 9-5.
As I also love my sunshades with polarized glasses, I would have loved if the HUD of the new 9-5 would behave the same way as the SID of my OG 9-5. Why am I comparing those different displays? Well they are both based on the same technology, namely LCD.
Thanks to Wikipedia, I don’t have to explain what the Malus’ law is. Nonetheless and in short, if the axes of two polarizing filters are orthogonal, the polarisers are crossed and in theory no light is transmitted.
Well a LCD screen uses the Malus’ law to let more or less background light pass through and show brighter and darker spots. And if the polarizing axe of our sunshades is orthogonal to the polarizing axe of the LCD, we will only see a black screen.
Coming back to the LCD’s in Saabs and other cars. I had a Citroen C2, in that car the information and radio Display was always pitch black when I had my shades on, I had to put my head almost horizontally to see something on that display. On the Peugeot of my wife it is almost perfect. If my head is vertical I see a darker display, but at least I see something. If I incline the head to one side the display gets darker, and if i incline the head to the other side the display gets brighter. But the best result is still the SID of my OG 9-5. Full brightness with my head in vertical position and dark display putting my head in a horizontal position, but I don’t usually drive in that position 😉
And what about the HUD? It seems like the polarizing axe of the display hasn’t been well chosen. Is somebody to blame? Not really, because the inclination of the windscreen might be the reason, but it is a problem that could have been corrected during the development of the HUD.
At the end of the day, new Saab should take care of such details, and I think they will.