Electro-optical position determining system

Apparatus for providing signals representative of one or more positions of at least one light source movable within a selected area, comprising:

• first and second photodetecting means spaced at first and second locations, respectively, along a base line by a first predetermined distance;
• means associated with each said photodetecting means for providing a moving field of view for each photodetecting means, said moving fields of view moving arcuately around said photodetecting means independently of movement of said at least one light source;
• means for monitoring angular positions of each of the arcuately moving fields of view with respect to the base line and providing signal indications thereof;
• light means emitted by said at least one light source detectable by each of the photodetecting means;
• a first signal generated by said first photodetecting means upon receipt of said light means from said at least one light source through the field of view of the first photodetecting means;
• a second signal generated by said second photodetecting means upon receipt of said light means from said at least one light source through the field of view of the second photodetecting means;
• and
• means operative in response to said signal indications of the angular position monitoring means when said first and second signals are generated by said first and second photodetecting means, respectively, for providing a signal representing the position of the at least one light source within the selected area.

A data entry system for providing signals representative of one or more positions of a stylus movable within a defined area, comprising:

• first and second photodetecting means spaced along a base line and separated by a predetermined distance therebetween, and wherein said first and second photodetecting means are immobile with respect to said stylus;
• means associated with each photodetector for providing a uniformly rotating narrow field of view for each said first and second photodetecting means, and wherein rotation of said narrow field of view for said each said first and second photodetecting means is independent of movement of said stylus;
• means for monitoring an angular position of each of the narrow fields of view with respect to the base line and providing signal indications thereof;
• a light emitter associated with said movable stylus, said light emitter providing light means detectable by each of the first and second photodetecting means;
• a first signal generated by said first photodetecting means each time said first photodetecting means, said narrow field of view associated therewith and said light means are in linear alignment;
• a second signal generated by said second photodetecting means each time said second photodetecting means, said narrow field of view thereof, and said light means are in linear alignment;
• and
• means operative in response to the signal indications of the angular position monitoring means when said first and second signals are generated by said first and second photodetecting means, respectively, for providing a signal representing the position of the stylus within the defined area.

A method for determining a position of a light source movable within a selected area comprising the steps of:

• emitting light having selected characteristics from said light source located within said selected area;
• uniformly scanning said selected area from first and second locations spaced a predetermined distance apart along a base line, said step of uniformly scanning further comprising
• positioning first and second photodetecting means at said first and second locations, respectively,
• sequentially exposing incremental segments of each said first and second photodetecting means to said selecting area, said sequentially exposing occurring independently of movement of said light source, and
• monitoring said exposed incremental segments of each said first and second photodetecting means with respect to a reference associated therewith;
• detecting emitted light from said light source at each said first and second locations, said detecting occurring independently of movement of said light source;
• correlating said monitored incremental detection segments of said first and second photodetecting means with said detected light at each said first and second locations, respectively, to determine a first line of sight between said detected light and said first location and a second line of sight between said detected light and said second location, respectively;
• determining a first angle between said base line and said first line of sight and a second angle between said base line and said second line of sight;
• and
• computing the position of said light source within said selected area from said first and second angles and said predetermined distance.

A data entry tablet for providing signals representative of one or more positions of a stylus movable within the area of the table, comprising:

• first and second photodectors spaced along a base line and separated by a predetermined distance therebetween, said first and second photodetectors being immovable with respect to said stylus;
• mean associated with each photodetector for providing a rotating narrow field for each photodetector, rotation of said narrow field of view of each photodetector being independent of movement of said stylus;
• means for monitoring angular positions of each of the narrow fields of view with respect to the base line and providing signal indications thereof;
• a light emitter associated with said movable stylus, said light emitter providing light means detectable by each said first and second photodetectors;
• a first signal generated by said first photodetector each time said first photodetector, said narrow field of view associated therewith and said light means are in linear alignment;
• a second signal generated by said second photodetector each time said second photodetector, said narrow field of view associated therewith and said light means are in linear alignment;
• and
• means operative in responsne to the signal indications of the angular position monitoring means when said first and second signals are generated by said first and second photodetectors, respectively, for providing a signal representing the position of the emitter within the area of the tablet.

A data entry system for providing signals representative of one or more positions of a stylus movable within a defined area, comprising:

• first and second photodetectors spaced along a base line and separated by a predetermined distance therebetween, said first and second photodetectors being immovable with respect to said stylus;
• means associated with each photodetector for providing a rotating narrow field of view for each photodetector, rotation of said narrow field of view of each photodetector being independent of movement of said stylus;
• means for monitoring an angular position of each of the narrow fields of view with respect to the base line and providing signal indications thereof;
• a light emitter associated with said movable stylus, said light emitter providing light means detectable by each of the first and second photodetectors;
• a first signal generated by said first photodetector each time the first photodetector, said narrow field of view associated therewith and said light means are in linear alignment;
• a second signal generated by said second photodetector each time the second photodetector, said narrow field of view associated therewith and said light means are in linear alignment;
• and
• means operative in response to the signal indications of the angular position monitoring means when said first and second signals are generated for providing a signal representing the position of the emitter within the defined area.