Abstract: An optical security system having a key, an optic lock, and a processing system. The lock generally has a plurality of optic reflective sensors, a plurality of rotatable readable discs, and a controller for processing information to and from the plurality of sensors. The optic security lock senses the surface changes of state during the rotation of the plurality of discs caused by the turning of the fully-engaged key. The data from the sensors is communicated to the controller, with the controller having a processor capable of processing data from the sensors to generate a lock command signal. The lock can include a plurality of detent mechanisms to provide precision interval alignment of the sensors with the rotatable discs to accurately sense the surface changes of state.