Determining the location of the tip of an electronic stylus

A method comprising:

• determining a locus of positions of a first ultrasonic transmitter in an electronic stylus relative to a given reference point;
• determining a locus of position of a second ultrasonic transmitter in the electronic stylus relative to the given reference point;
• and
• determining a position of a writing tip in the electronic stylus relative to the given reference point using the determined locus of positions of the first ultrasonic transmitter, determined locus of positions the second ultrasonic transmitter, and relative positions of the first ultrasonic transmitter, the second ultrasonic transmitter, and the writing tip within the stylus.

A method of determining a position of a tip of a stylus relative to a coordinate system, the stylus having a first ultrasonic transmitter at a first fixed location in the stylus and a second ultrasonic transmitter at a second fixed location in the stylus, comprising:

• determining a first locus of positions for the first ultrasonic transmitter relative to the coordinate system;
• determining a second locus of positions for the second ultrasonic transmitter relative to the coordinate system;
• determining a first inclination angle of the first ultrasonic transmitter;
• determining a second inclination angle of the second ultrasonic transmitter;
• and
• determining the location of the tip of the stylus relative to the coordinate system using the first locus of positions, the second locus of positions, the first inclination angle, the second inclination angle, and the locations of the first ultrasonic receiver, the second ultrasonic receiver, and the tip of stylus relative to one another.

A method comprising

• determining a distance between a first ultrasonic transmitter in an electronic pen and a first ultrasonic receiver in a base unit;
• determining a distance between the first ultrasonic transmitter in the electronic pen and a second ultrasonic receiver in the base unit;
• determining a distance between a second ultrasonic transmitter in the electronic pen and the first ultrasonic receiver in the base unit;
• determining a distance between the second ultrasonic transmitter in the electronic pen and the second ultrasonic receiver in a base unit;
• and
• storing each of the determined distances in a non-volatile memory.

A method of determining a position of the tip of a stylus relative to a coordinate system, the stylus having a first ultrasonic transmitter located at a first fixed location in the stylus and a second ultrasonic transmitter located at a second fixed location in the stylus, comprising:

• receiving a distance between a first ultrasonic transmitter in an electronic stylus and a first ultrasonic receiver in a base unit;
• receiving a distance between the first ultrasonic transmitter in the electronic stylus and a second ultrasonic receiver in the base unit;
• receiving a distance between a second ultrasonic transmitter in the electronic stylus and the first ultrasonic receiver in the base unit;
• receiving a distance between the second ultrasonic transmitter in the electronic stylus and the second ultrasonic receiver in a base unit;
• and
• determining the position of the tip of the stylus relative to the coordinate system using the received distances.

A method comprising:

• receiving distances between a first ultrasonic transmitter located in a stylus and each of two ultrasonic receivers located in a base unit;
• receiving distances between a second ultrasonic transmitter located in a stylus and each of the two ultrasonic receivers;
• and
• determining a location of a tip of the electronic stylus relative to the base unit using the received distances, a fixed distance between the two ultrasonic transmitters, a fixed distance between the two ultrasonic receivers, and a location of the tip of the stylus relative to one of the ultrasonic transmitters.

A method comprising:

• receiving time values indicative of a time required for an ultrasonic signal to travel between a first ultrasonic transmitter in an electronic pen and a first ultrasonic receiver in a base unit;
• receiving a second time value indicative of a time required for an ultrasonic signal to travel between the first ultrasonic transmitter and a second ultrasonic receiver in the base unit;
• receiving a third time value indicative of a time required for an ultrasonic signal to travel between a second ultrasonic transmitter in the electronic pen and the first ultrasonic receiver;
• receiving a fourth time value indicative of a time required for an ultrasonic signal to travel between the second ultrasonic transmitter and the second ultrasonic receiver;
• and
• determining a location of a tip of the electronic stylus relative to the base unit using each of the time values, a fixed distance between the two ultrasonic transmitters, a fixed distance between the two ultrasonic receivers, and a location of the tip of the stylus relative to one of the ultrasonic transmitters.