Abstract: A marker for an optical tracking system includes an object having a curved surface and a plurality of beads adhered to the curved surface with an adhesive. The beads of the plurality of beads are configured for being retroreflectors. A bead of the plurality of beads can include a first portion having a reflective surface and a second portion that is substantially transparent. The first portion of the bead is oriented toward the curved surface of the object. The second portion of the bead is oriented away from the curved surface of the object. The beads are applied to the marker. A bead of the plurality of beads can be transparent and embedded in a reflective medium on the marker surface.

Abstract: A contact image sensor can illuminate a portion of a banknote with one or more light emitting diodes (LEDs), capture an image of the portion of the banknote with illumination reflected from or transmitted through the banknote, and generate a digital output signal that represents the captured image. A controller board can receive the digital output signal, generate one or more LED control signals, each LED control signal including changes in voltage to indicate times to switch a light emitting diode on or off, direct the one or more LED control signals to the contact image sensor, bypass digital LED control circuitry that is included with the contact image sensor, and switch the one or more LEDs in the contact image sensor on or off at the times indicated by the respective light emitting diode control signals.

Abstract: A contact image sensor can illuminate a portion of a banknote with one or more light emitting diodes (LEDs), capture an image of the portion of the banknote with illumination reflected from or transmitted through the banknote, and generate a digital output signal that represents the captured image. A controller board can receive the digital output signal, generate one or more LED control signals, each LED control signal including changes in voltage to indicate times to switch a light emitting diode on or off, direct the one or more LED control signals to the contact image sensor, bypass digital LED control circuitry that is included with the contact image sensor, and switch the one or more LEDs in the contact image sensor on or off at the times indicated by the respective light emitting diode control signals.