HEAD TRACKING

• US 20110293129A1
• Filed: 02/09/2010
• Published: 12/01/2011
• Est. Priority Date: 02/13/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Dillen, Paulus Henricus Antonius, Schuijers, Erik Gosuinus Petrus, Oomen, Arnoldus Werner Johannes
• Granted Patent: US 10,015,620 B2
• Time in Patent Office: Days
• US Class Current: 381/370
• CPC Class Codes: H04S 7/304 For headphones

Abstract

A head tracking system (400) is proposed in the present invention that determines a rotation angle (300) of a head (100b) of a user (100) with respect to a reference direction (310), which is dependent on a movement of a user (100). Here the movement of a user should be understood as an act or process of moving including e.g. changes of place, position, or posture, such as e.g. lying down or sitting in a relaxation chair. The head tracking system according to the invention comprises a sensing device (410) for measuring a head movement to provide a measure (401) representing the head movement, and a processing circuit (420) for deriving the rotation angle of the head of the user with respect to the reference direction from the measure. The reference direction (310) used in the processing circuit (420) is dependent on the movement of the user. The advantage of making the reference direction (310) dependent on a movement of a user is that determining the rotation angle (300) of the head (100b) is independent of the environment, i.e. not fixed to environment. Hence whenever the user (100) is e.g. on the move and his body parts undergo movement the reference direction is adapted to this movement.

Claims

1. A head tracking system (400) comprising:

a sensing device (410) for measuring a head movement to provide a measure (401) representing a head movement, and

a processing circuit (420) for deriving a rotation angle (300) of a head (100b) of a user (100) with respect to a reference direction (310) from the measure (401), wherein the reference direction (310) used in the processing circuit (420) is dependent on a movement of a user (100).

2. A head tracking system (400) as claimed in claim 1, wherein the processing circuit (420) is further configured to determine the reference direction (310) as an average direction of the head (100b) of the user during the movement of the user (100).

3. A head tracking system (400) as claimed in claim 2, wherein the sensing device (410) comprises at least one accelerometer (410a, 410b) for deriving an angular speed of a rotation of the head (100b) of the user as the measure (401) based on centrifugal force caused by the rotation.

4. A head tracking system (400) as claimed in claim 3, wherein the processing circuit (420) is configured to derive an average direction of the head of the user from the angular speed of the head of the user.

5. A head tracking system (400) as claimed in claim 4, wherein the average direction is determined as an average of the rotation angle over a predetermined period of time.

6. A head tracking system (400) as claimed in claim 5, wherein the averaging is adaptive.

7. A head tracking system (400) as claimed in claim 1, wherein the processing circuit (420) is further configured to use a direction of a user body torso (100a) during the movement of the user (100) as the reference direction (310).

8. A head tracking system (400) as claimed in claim 7, wherein the direction of the user body torso (100a) is determined as the forward body direction of a reference point located on the body torso.

9. A head tracking system (400) as claimed in claim 8, wherein the sensing device comprises a magnetic transmitter (600) attached to the reference point and a magnetic sensor (630) attached to the head (100b) of the user (100) for receiving a magnetic field transmitted by the magnetic transmitter (600).

10. A head tracking system (400) as claimed in claim 9, wherein the magnetic transmitter (600) comprises two orthogonal coils (610 and 620) placed in a transverse plane, wherein the magnetic field created by each of the two orthogonal coils (610 and 620) is modulated with different modulation frequencies.

11. A head tracking system (400) as claimed in claim 9, wherein the magnetic sensor (630) comprises a coil, wherein the coil is placed in a predetermined direction of the head (100b) of the user (100).

12. A head tracking system (400) as claimed in claim 9, wherein the processing circuit (420) is configured to derive rotation angle (300) of a head (100b) of a user (100) from the magnetic field received by the magnetic sensor (630).

14. An audio reproduction system (700) for audio scene reproduction over headphone comprising a headphone (710) for reproducing an audio scene and a rendering processor (720) for rendering the audio scene to be reproduced, characterized in that the audio reproduction system further comprises a head tracking system (400) according to one of the claims 1-12 for determining a rotation angle (300) of a head (100b) of a user (100), wherein the rendering processor (720) renders the audio scene to be rotated by an angle opposite to the rotation angle (300).

13. A head tracking method comprising the steps of:

measuring a head movement to provide a measure (401) representing a head movement, and

deriving a rotation angle (300) of a head (100b) of a user (100) with respect to a reference direction (310) from the measure (401),

characterized in that

the reference direction used in the deriving step is dependent on a movement of a user (100).

15. An audio reproduction system as claimed in claim 13, wherein head tracking system (400) is at least partially integrated with the headphone.