Methods and apparatus for position estimation using reflected light sources

A method of estimating a position of an object in an area defined by a wall having a surface, the method comprising:

• projecting two light spots at a substantially fixed location on the surface;
• detecting a reflected light from the two light spots using a detector mounted on the object;
• and
• estimating the position of the object with a data processing unit mounted on the object using the reflected light detected by the detector,
• wherein the projecting of the two light spots is accomplished by two light sources,
• wherein the two light sources generate lights that have different characteristics from each other, such that the two light spots can be distinguished from each other by the detector and/or the data processing unit,
• wherein the different characteristics comprise different modulations.

A position estimation system for estimating a position of an object, the system comprising:

• one or more light sources configured to project at least light spots onto a surface;
• a detector affixed to the object configured to detect the at least two light spots, wherein the at least two light spots comprise reflected light from the one or more light sources;
• and
• a data processing unit configured to determine the position of the object based on the location of the at least two light spots,
• wherein the at least two light spots comprise two or more light spots that differ with respect to an optical characteristic, and wherein the detector is configured to distinguish the two or more light spots based on the optical characteristic,
• wherein the optical characteristic is light modulation, and
• wherein the system is configured to extract a modulation signal using a band-pass filter with lower and upper frequencies.