Digital sundial

A digital sundial is a clock that indicates the current time with numerals formed by the sunlight striking it.

The sun's rays shine on ten linearly distributed sockets of optical waveguides that transport the light to a seven-segment display.

Each socket fiber is connected to a few segments forming the digit corresponding to the position of the sun.

Let Lθ denote a straight line passing through the origin of a Cartesian coordinate system and making angle θ ∈ [0,π) with the x-axis.

Theoretically, it is possible to build a set of masks that produce shadows in the form of digits, such that the display changes as the sun moves.

[3] The first prototype of a digital sundial was constructed in 1994; it writes the numbers with light instead of shadow, as Falconer proved.