System and method of pointed position detection system, projector and program

A pointed position detection system which detects a position pointed by a pointer within a predetermined image display region, the system comprising:

• image pick-up section for picking up an image of the image display region;
• section for storing an image for differential image generation which is generated by picking up an image of the image display region on which a uniform image is displayed;
• differential image extraction section for extracting a differential image based on the image for differential image generation and a pointing image which is generated by picking up an image of the image display region in which a pointing action is performed based on a cast shadow;
• and
• section for detecting a pointed position in the pointing image based on the extracted differential image, wherein the means for detecting the pointed position detects change of environment effect on the image display region even when the pointing action is in a halted state, and substitutes a new image for differential image generation in place of the image for differential image generation when the detected change based on a calculated dispersion of pixels is equal to or greater than a predetermined amount.

A computer-usable program embodied on an information storage medium or in a carrier wave for implementing a system that detects a pointed position in a predetermined image display region, the program implementing in a computer:

• means for storing an image for differential image generation which is generated by picking up an image of the image display region on which is displayed a uniform image by means of image pick-up means;
• differential image extraction means for extracting a differential image based on the image for differential image generation and a pointing image which is generated by picking up an image of the image display region in which a pointing action is performed based on a cast shadow;
• and
• means for detecting a pointed position in the pointing image, based on the extracted differential image, wherein the means for detecting the pointed position detects change of environment effect on the image display region even when the pointing action is in a halted state, and substitutes a new image for differential image generation in place of the image for differential image generation when the detected change based on a calculated dispersion of pixels is equal to or greater than a predetermined amount.

A pointed position detection method of detecting a position pointed in a predetermined image display region, the method comprising the steps of:

• storing an image for differential image generation which is generated by picking up an image of the image display region on which is displayed a uniform image;
• extracting a differential image based on the image for differential image generation and a pointing image which is generated by picking up an image of the image display region in which a pointing action is performed based on a cast shadow;
• detecting a pointed position in the pointing image, based on the extracted differential image;
• and
• detecting change of environment effect on the image display region even when the pointing action is in a halted state, and substituting a new image for differential image generation in place of the image for differential image generation when the detected change based on a calculated dispersion of pixels is equal to or greater than a predetermined amount.