Projection system, position detection system, and method for controlling position detection system

1. A projection system comprising:

a projector that projects a projection image on a projection surface; and

a pointing element that points at the projection surface,

wherein the pointing element includes

a recursive reflector that is provided at a front end section of the pointing element and that reflects infrared light, and

an information communication transmitter that transmits contact notification to the projector when the pointing element senses contact between the front end section and an object; and

wherein the projector includes

a light radiator that radiates the infrared light toward the projection surface,

a first camera that captures an image of the projection surface,

a second camera that is disposed in a position different from a position of the first camera and captures an image of the projection surface, and

one or more electronic circuits,

wherein the one or more electronic circuits is configured to detect a position where the pointing element comes into contact with the projection surface based on a position of the recursive reflector detected with the first and second cameras and the contact notification.

2. The projection system according to claim 1 ,

wherein the one or more electronic circuits is configured to detect the contact notification, and

wherein the one or more electronic circuits is configured to detect a first bright spot candidate that is a candidate of a bright spot corresponding to the infrared light reflected off the recursive reflector from a first captured image captured with the first camera and a second bright spot candidate that is a candidate of the bright spot from a second captured image captured with the second camera.

3. The projection system according to claim 2 ,

wherein the second camera is so disposed as to be separate from the first camera along one of a first coordinate axis perpendicular to a normal to the projection surface and a second coordinate axis perpendicular to the normal and the first coordinate axis, and

wherein the one or more circuits is configured to convert coordinates of a position of the first bright spot candidate in the first captured image into first position coordinates in a two-dimensional coordinate system specified by the first and second coordinate axes and converts coordinates of a position of the second bright spot candidate in the second captured image into second position coordinates in the two-dimensional coordinate system, and

wherein the one or more circuits is configured to calculate coordinates of a position of the front end section in the two-dimensional coordinate system based on the first and second positional coordinates when the contact detector evaluates whether or not the front end section is in contact with the projection surface based on a difference between the first position coordinates and the second position coordinates, determines that the front end section is in contact with the projection surface, and detects the contact notification.

4. The projection system according to claim 1 ,

wherein the light radiator includes a first light source so provided as to correspond to the first camera and a second light source so provided as to correspond to the second camera.

5. The projection system according to claim 2 ,

wherein the one or more circuits is configured to detect as the first bright spot candidate an area in the first captured image that is an area which corresponds to a set of pixels each having a pixel value greater than or equal to a first threshold and in which the number of pixels that belongs to the area is smaller than a second threshold and further detects as the second bright spot candidate an area in the second captured image that is an area which corresponds to a set of pixels each having a pixel value greater than or equal to the first threshold and in which the number of pixels that belongs to the area is smaller than the second threshold.

6. The projection system according to claim 2 ,

wherein the one or more circuits is configured to evaluate whether or not the front end section is in contact with the projection surface when the first bright spot candidate was detected and the second bright spot candidate was detected.

7. The projection system according to claim 6 ,

wherein the one or more circuits is configured to determine that the front end section is in contact with the projection surface when a difference between the first position coordinates and second position coordinates along the one of the first and second coordinate axes is smaller than or equal to a third threshold and a difference between the first position coordinates and second position coordinates along another of the first and second coordinate axes is smaller than or equal to the third threshold.

8. A position detection system comprising:

a pointing element that points at an operation surface; and

a position detection apparatus that detects a position at which the pointing element is pointing,

wherein the pointing element includes

a recursive reflector that is provided at a front end section of the pointing element and that reflects infrared light, and

an information communication transmitter that transmits contact notification to the position detection apparatus when the pointing element senses contact between the front end section and the operation surface, and

the position detection apparatus includes

a light radiator that radiates the infrared light toward the operation surface,

a first camera that captures an image of the operation surface,

a second camera that is disposed in a position different from a position of the first camera and captures an image of the operation surface, and

one or more electronic circuits configured to detect a position where the pointing element is pointing at the operation surface based on a position of the recursive reflector detected with the first and second cameras and the contact notification.

9. A method for controlling a position detection system,

wherein the position detection system includes a pointing element that points at an operation surface and includes a recursive reflector that is disposed at a front end section of the pointing element and that reflects infrared light, and a position detection apparatus that includes a first camera and a second camera disposed in a position different from a position of the first camera and detects a position at which the pointing element is pointing,

wherein the method comprises:

transmitting, via the pointing element, contact notification to the position detection apparatus when the pointing element senses contact between the front end section and the operation surface,

causing, via the position detection apparatus, a light radiator to radiate the infrared light toward the operation surface,

causing, via the position detection apparatus, the first and second cameras to each capture an image of the operation surface, and

detecting, via the position detection apparatus, a position where the pointing element is pointing at the operation surface based on a position of the recursive reflector detected with the first and second cameras and the contact notification.

10. The method for controlling a position detection system according to claim 9 , further comprising:

detecting, via the position detection apparatus, a first bright spot candidate that is a candidate of a bright spot corresponding to the infrared light reflected off the recursive reflector from a first captured image provided when the first camera captures an image of the operation surface and a second bright spot candidate that is a candidate of the bright spot from a second captured image provided when the second camera captures an image of the operation surface.

11. The method for controlling a position detection system according to claim 10 ,

wherein the second camera is so disposed as to be separate from the first camera along one of a first coordinate axis perpendicular to a normal to the operation surface and a second coordinate axis perpendicular to the normal and the first coordinate axis, and

wherein the method further comprises:

converting, via the position detection apparatus, coordinates of a position of the first bright spot candidate in the first captured image into first position coordinates in a two-dimensional coordinate system specified by the first and second coordinate axes and converts coordinates of a position of the second bright spot candidate in the second captured image into second position coordinates in the two-dimensional coordinate system, and

calculating, via the position detection apparatus, coordinates of a position of the front end section in the two-dimensional coordinate system based on the first and second positional coordinates when the position detection apparatus evaluates whether or not the front end section is in contact with the operation surface based on a difference between the first position coordinates and the second position coordinates, determines that the front end section is in contact with the operation surface, and

detecting, via the position detection apparatus, the contact notification.