Image registration method and apparatus

In a multi-color image projector system for generating at least two images, one of a first color, the other of a second color, the two images being projected onto a common screen, the combination of the two colored images forming a desired multi-colored image, an image registration system for registering the position of the respective images, comprising:

• a registration sensor having a single defined active area, said registration sensor comprising a photodetector device having an active area and providing an output signal proportional to the intensity of the light incident on said active area, and a sensor mask having a mask opening, said sensor active area substantially centered on said mask opening, said mask providing a means for defining the active area of said photodetector device;
• first means for sampling the output of said sensor during a calibration time interval and holding the output value as a calibration signal value;
• second means for sampling the output of said sensor during a vertical pattern time interval and holding the output value as a vertical pattern signal value;
• third means for sampling the output of said sensor during the horizontal pattern time interval and holding the output value as a horizontal pattern signal value;
• means for projecting a first color calibration pattern covering the entire active area of said sensor during a first color calibration time interval, a first color vertical half pattern which nominally illuminates only one vertical half of the active are of said sensor during a first color vertical pattern time interval, and a first color horizontal pattern which nominally illuminates only one horizontal half of said active area of said sensor during a horizontal pattern time interval;
• means for projecting a second color calibration pattern covering the entire active area of said sensor during a second color calibration time interval, a second color vertical half pattern which nominally illuminates only one vertical half of the active area of said sensor during a second color vertical pattern time interval, and a second color horizontal pattern which nominally illuminates only one horizontal half of the active area of said sensor during a second color horizontal pattern time interval;
• and
• first correction means responsive to the respective calibration, vertical pattern and horizontal pattern signals during said first color calibration, vertical pattern and horizontal pattern time intervals for forming first color position correction signals to register said first color image;
• second correction means responsive to the respective calibration, vertical pattern and horizontal pattern signals during said second color calibration, vertical pattern and horizontal pattern time intervals for forming second color position correction signals to register said second color image.

In an image projector system including one or more image projectors, each for projecting a respective image, each image having registrations at a predetermined relative location, a method for registering the position of one or more projected images, comprising:

• using the projector system to project an image which illuminates the entire active area of a registration sensor positioned at an image plane during a calibration time interval, said sensor being characterized by a single active area;
• sampling the output of said sensor during said calibration time interval and storing the output value as a calibration signal value;
• using the projector system to project a vertical pattern image which nominally illuminates only one vertical half of said active area of said sensor during a vertical pattern time interval;
• sampling the output of said sensor during a vertical pattern time interval and storing the output value as a vertical pattern signal value;
• using the projector system to project a horizontal pattern image which nominally illuminates only one horizontal half of the active area of said sensor during a horizontal pattern time interval;
• sampling the output of said sensor during the horizontal pattern time interval and storing the output value as a horizontal pattern signal value;
• and
• processing the respective calibration, vertical pattern and horizontal pattern signals to form position correction signals to register said image.