Real images: Lighted ‘F-object’ and an astygmatic lens.

A cylindrical lens is placed between a lighted ‘F-object’ and a screen. The lens can be rotated. An image is focused on the screen. In CASE 1, the cylindrical lens is in vertical position, and the vertical bar of the ’F’ is in focus, and the horizontal bars of the ‘F’ are out of focus. In CASE 2, the cylindrical lens is in the horizontal position, and the horizontal bars of the ‘F’ are in focus, and the vertical bars of the ‘F’ are out of focus.