Projector and projector accessory

1. A projector, comprising:

an infrared photodetector for photodetecting infrared light that is emitted by an electronic pen that is manipulated on a screen and that is provided with an infrared light emission device and an ultrasonic generator; and

at least two ultrasonic receivers that detect ultrasonic waves that are emitted by said electronic pen; said projector being provided with capability for acquiring a position of said electronic pen on said screen.

2. A projector, comprising:

an infrared photodetector for photodetecting infrared light that is emitted by an electronic pen that is manipulated on a screen and that is provided with an infrared light emission device and an ultrasonic generator;

at least two ultrasonic receivers that detect ultrasonic waves that are emitted by said electronic pen; and

means for measuring a distance to said screen.

3. A projector according to claim 2 , wherein said projector further comprises:

means for acquiring a position of said electronic pen on said screen from output of said infrared photodetector, output of said ultrasonic receivers, and output of said means for measuring the distance to said screen.

4. A projector according to claim 3 , wherein said projector further comprises calibration means for:

estimating the projector-screen distance by using said electronic pen to indicate calibration points that are displayed by-said projector;

based on the projector-screen distance, correcting a vertical component of Cartesian coordinates derived by converting a distance to the electronic pen tip;

performing this correction for each calibration point; and

storing the generated coordinates as corrected coordinates.

5. A projector that enlarges and projects a display image that is on a light valve onto a screen, said projector comprising:

an infrared photodetector for photodetecting infrared light that is emitted by an electronic pen that is manipulated on the screen and that is equipped with an infrared light emission device and an ultrasonic generator;

at least two ultrasonic receivers for detecting ultrasonic waves that are emitted by said electronic pen;

means for measuring a distance to said screen;

means for supplying coordinate data in which a position of said electronic pen on said screen, which is calculated based on output of said infrared photodetector, output of said ultrasonic receivers, and output of said means for measuring the distance to said screen, has been normalized by a length of a side of a projected rectangular image that has been enlarged and projected; and

means for:

performing calibration by:

estimating the projector-screen distance by using said electronic pen to indicate calibration points that are displayed by the projector;

based on the projector-screen distance, correcting a vertical component of Cartesian coordinates derived by converting a distance to the pen tip;

performing this correction for each of the calibration points; and

storing the generated coordinates as corrected coordinates;

and in actual drawing, for:

generating Cartesian coordinates based on the distance to the pen tip;

using the projector-screen distance that was obtained during calibration to correct the vertical component; and

using the corrected coordinates that were obtained during calibration to convert Cartesian coordinates after correction to panel coordinate system.

6. A projector according to claim 1 , wherein said projector is a mirror-projection type projector.

7. A projector according to claim 2 , wherein said projector is a mirror-projection type projector.

8. A projector according to claim 3 , wherein said projector is a mirror-projection type projector.

9. A projector according to claim 4 , wherein said projector is a mirror-projection type projector.

10. A projector according to claim 5 , wherein said projector is a mirror-projection type projector.

11. A projector accessory for a projector, said projector accessory, comprising:

an infrared photodetector for photodetecting infrared light that is emitted by an electronic pen that is manipulated on a screen and that is provided with an infrared light emission device and an ultrasonic generator;

at least two ultrasonic receivers for detecting ultrasonic waves that are emitted by said electronic pen; and

means for measuring a distance to said screen.

12. A projector accessory according to claim 11 , wherein said projector accessory further comprises:

a means for acquiring a position of said electronic pen on said screen based on output of said infrared photodetector, output of said ultrasonic receivers, and output of said means for measuring the distance to said screen.

13. A projector accessory according to claim 12 , said projector accessory further comprising calibration means for:

estimating the projector-screen distance by using said electronic pen to indicate calibration points that are displayed by said projector;

based on the projector-screen distance, correcting a vertical component of Cartesian coordinates derived by converting a distance to the pen tip;

performing this correction for each calibration point; and

storing the generated coordinates as corrected coordinates.

14. A projector accessory according to claim 11 , wherein said projector is a mirror-projection type projector.

15. A projector accessory according to claim 12 , wherein said projector is a mirror-projection type projector.

16. A projector accessory according to claim 13 , wherein said projector is a mirror-projection type projector.