An optically imaging pen for interacting with a printed substrate. The pen includes: a nib for interacting with the printed substrate; an image sensor for imaging an area of the printed substrate to provide image data; a processor configured for: (i) identifying target elements in the image data and inferring a perspective transform due to a tilt of the pen; (ii) acquiring and decoding coded data contained in the image data; (iii) calculating a nib position using a tag location, the perspective transform and a known geometry of pen optics; and (iv) generating digital ink based on the nib position.