Patent ID: 7972014
Filing Date: 2011-07-05
Classification: H04N

Abstract:
1. A scanning projection apparatus with phase detection and compensation comprising: a light source for generating a light beam consisting of plural light beams having wavelengths of red, green and blue colors; a beam scanner which deflects the light beam about a first deflection axis at a first frequency and about a second deflection axis at a second frequency to project a two dimensional image field, wherein the deflected light beam is switched off in the perimeter of the image field, defined as a dark field, and the region inside the dark field is used for displaying a projected image and is defined as an active image field; a modulation means for modulating the intensity of the light beam according to the image to be projected; and, a sensor operable to detect if the deflected light beam is positioned near a vertical extreme of the dark field but outside the active image field at a distance from the beam scanner inside the projection apparatus such that at least part of its sensing area is disposed within the vertical extreme of the dark field, wherein the light beam is switched on near the vertical extreme of the dark field for a half period of the first frequency once per image frame to sweep over the sensor; wherein the method of detection and compensation of the phase difference between the actual and predicted positions of the deflected light beam comprising the following steps: first, determining and storing T second, determining the phase error T third, compensating the phase error by adjusting the modulation timing of the light beam by T wherein, D