What beaker said above about the elements of the VFD shining back is right on the mark. In direct sunlight, the non-lit elements shine just as bright as the lit elements. It's because the elements themselves are too reflective, reflecting sunlight back as if the element was lit. The best way to solve this problem is to find a VFD that is not reflective. Either that, or find a display screen that can distinquish between reflected light and light emitted by lit elements. I'm not surprised the AR screen still does not work that well in direct sunlight.