Four-prisms, same index of refraction, different angles, using laser.

A set of 4 prisms, all with the same index of refraction but with different vertex angles, are mounted on a tray so that they can slide back and forth in front of the laser beam. As the beam moves from one prism to the next, the deflection angles change according to the angle of the prisms. See figure 1. Four prisms, same index of refraction, different angles, using laser.