Interactive display system

In an interactive display system, a transmitter is provided for transmitting a periodic signal to a plurality of receivers through the air. One or more phase differences are measured between the receiving at pairs of receivers. These phase differences control the coordinates of a locator on a display screen. Separate measured phase differences control the positions along different coordinate axes independently.

We claim:

1. Interactive display system, comprising

a transmitter, for transmitting a periodic signal which is suitable for propagation through the air to

a plurality of substantially pointlike receivers at respective fixed positions with respect to each other, whereas a relative position of the transmitter with respect to the plurality of receivers is manipulatable, the receivers being suitable for receiving said periodic signal, a first and a second receiver from the plurality feeding

first phase difference measuring means, for measuring a first phase difference between said receiving the periodic signal at the first and second receiver, the first phase difference measuring means feeding

location control means, for on the basis of a received phase signal controlling a target location on the display screen,

characterized, in that the location control means are arranged for controlling a first coordinate of the target location along a first predetermined coordinate axis on the display screen, independent of a second coordinate along a second coordinate axis which is oriented across the first coordinate axis.

2. Interactive display system according to claim 1, in which

a third and fourth receiver from the plurality of receivers feed

second phase difference measuring means, for determining a second phase difference, using said receiving of the periodic signal at the third and fourth receivers, the second phase difference measuring means feeding

the location control means, for on the basis of a second received phase signal cocontrolling the target location,

wherein a first plane through the transmitter and the first and second receiver does not coincide with a second plane through the transmitter and the third and fourth receiver, characterized, in that

the location control means are arranged for controlling the second coordinate of the target location with respect to the second coordinate axis, under control of the second phase difference signal, independent of the first phase difference signal.

3. Interactive display system according to claim 2, the first, second, third and fourth receivers exhibiting respective first, second, third and fourth spatial cones of directions of highest directional receiving sensitivity, characterized, in that the first, second, third and fourth receivers are directed such that the first, second, third and fourth spatial cones overlap in a manipulation region, the manipulation region not including a plane through the first second and third receivers.

4. Interactive display system according to claim 3, characterized, in that said manipulation region is a maniplupation cone extending to infinity.

5. Interactive display system according to claim 2, characterized, in that the first coordinate axis and the second coordinate axis cross each other at an angle, a first line through the first and second receivers making the same angle with respect to a second line through the third and fourth receivers.

6. Interactive display system according to claim 5, characterized, in that the angle is 90 degrees.

7. Interactive display system according to claim 2, characterized, in that the second receiver is also the fourth receiver.

8. Interactive display system according to claim 7, characterized, in that the first, second and third receivers form three corners of an isosceles triangle, the third receiver being at the top angle, the second coordinate axis being perpendicular to the coordinate axis, the second phase difference being determined as a sum of further phase differences between the receiving at the first and third and the receiving at the second and third receivers respectively.

9. Interactive display system according to claim 1 or 2, characterized, in that the location control means comprise coordinate update means for adding a coordinate update value to any of said first or second coordinate, said coordinate update value being determined from the first or second phase signal respectively.

10. Interactive display system according to claim 9, characterized, in that the location control means comprise scaling means, for, at a first point in time, scaling said update value by a factor, the factor increasing in proportion to a second update value, the second update value occurring at a second point in time, the second point in time preceding the first point in time.

11. Interactive display system according to claim 9, characterized, in that any of the first and/or second phase difference measuring means feed the location control means via phase differentiating means, the phase differentiating means being arranged for feeding a first and/or second time differentiated phase difference as phase signal to the location control means.

12. Interactive display system according to claim 11, characterized, in that the phase differentiating means feed the location control means via inertia retaining means, for setting any of the first and/or second phase signal as close to a further time differentiated phase difference as were attainable by adding an integer number of phase cycles to the time differentiated phase difference, the further time differentiated phase difference corresponding to the time differentiated phase difference at a previous point in time before a present point in time.

13. Interactive display system according to claim 1 or 2, characterized, in that the phase difference measuring means feed the location control means via phase reduction means, for reducing the phase signal to a value as close to a zero phase value as were attainable by adding an integer number of phase cycles to the phase difference.

14. Interactive display system according to claim 1 or 2, characterized, in that the phase difference measuring means feed the the location control means via jitter reduction means, for restricting the phase signal to a zero value unless the phase signal is outside a predetermined distance from said zero value.

15. Interactive display system according to claim 1 or 2, characterized, in that it comprises averaging means, for feeding an averaged phase signal to the location control means.

16. Interactive display system according to claim 1 or 2, characterized, in that said target location is indicated on the screen by a cursor shape, the cursor shape being independent of the target location.

17. Interactive display system according to claim 1, 2 or 3, characterized, in that the transmitter is provided in a mounting suitable for attachment to a human head.

18. Interactive display system according to claim 1, 2 or 3, characterized, in that the plurality of receivers is provided on a manipulable mounting, provided with means for cordless coupling of the phase signal to the location control means.

19. Interactive display system according to claim 1 or 2, characterized, in that the signal suitable for propagation through the air is an acoustic signal.

20. Interactive display system according to claim 1 or 2, characterized, in that the signal suitable for propagation through the air is an electromagnetic signal.