What is the term for a photo sensor that takes low-resolution, black-and white, closeup images?
You have two choices, one with lot of pixels (because more pixels is all the rage these days) and one pixel. You can get photo diodes or photo transistors that you would have to place very close to the lcd on each segment. You already have a sensor with many pixels. If you go to the one pixel version, you will probably place it so close to the screen you won't trigger the sensor unless the LCD is backlit.