Abstract: An image display system (10) having an auto-focus system (24). An image sensor (20) such as a CCD camera, senses the sharpness of pixels (26) comprising a portion of the image at a screen (16), preferably a magnified portion of the image. A sensor data processor (22) processes the pixel data from the sensor (20), and instructs the auto focus system (24) to adjust an optical parameter such as the focal length of a projector lens (14) as a function of the sensor (20) output. A DMD-type SLM is preferably utilized due to the uniform geometric features of the pixel mirrors, but other SLM's can be used. The sharpness or contrast between an “on” and an “off” pixel is sensed, and preferably a 10×10 array of pixels arranged in a checker board pattern is sensed.