Abstract: Processes and apparatuses analyze an image of maze pattern in order to extract bits encoded in the maze pattern. Grid lines of a maze pattern are determined. Directions for effective pixels of associated bars are estimated and are grouped into clusters. Lines are estimated for selected effective pixels of a selected cluster that is associated with a first principal direction. Grid lines of another cluster are determined, where the other cluster is associated with a second principal direction that is perpendicular with the first principal direction. Estimated lines are pruned based on slope variation analysis, grouped based on a distance analysis, and a best fit line is selected from each group. Affine parameters are determined from best fit lines. The correct orientation of a maze pattern is obtained by determining a type of missing corner of the maze pattern. Bits are extracted from the image of maze pattern by processing gray level values of the associated maze pattern cells.

Abstract: Systems and methods that determine a path of a pen tip as the pen tip is moved across a document are described. The document is watermarked with a maze pattern from which encoded position information is determined. A sequence of images is captured by a camera that is located in a pen. The path of the pen tip is determined by decoding the associated maze pattern and by matching the captured images with document images. If the position coordinates of any frame that is associated with a stroke cannot be determined from m-array decoding, the frames are transformed and then matched with an area of a document image. Once the position coordinates of at least one frame is determined, the position coordinates of other frames are determined by matching the frames in a neighboring area.

Abstract: A process and apparatus for determining the location of a captured array from a larger image is described. A non-repeating sequence may be folded into a non-repeating array in which the array is unique for every neighboring window of a given size. A portion of the array of the neighboring window may be captured and a subset of extracted bits corresponding to the captured array is decoded to identify error bits. The location of the captured array is determined within the non-repeating array by further processing the decoded bits.

Abstract: An efficient technique is provided for determining a portion of a document corresponding to a captured image. Areas of a document in which the pattern is at least partially obscured are identified. A reference pixel in the image is selected, and an offset between the pixel and the pattern is determined. A pixel-by-pixel comparison is then made of the image with the document such that the reference pixel is only compared with locations in the document that are both within the identified areas and have the determined offset from the pattern. The comparison with the highest correspondence between the image pixels and the electronic document then identifies the position of the reference pixel relative to the electronic document.

Abstract: An efficient technique is disclosed for determining a portion of a document corresponding to a captured image. When a user employs a pen to create a stroke in a document, images of the document are captured by a camera mounted on the pen. While the location of some of the images will be determined from, for example, an analysis of a pattern on the document that is captured by the image or a pixel-by-pixel comparison of the image with the document, the location of other images will be determined by segmenting the sequence of images into groups that correspond to the shape of the stroke. Information relating to located images in a segment can then be employed to determine the position of unlocated images in the segment. For example, a document search region for an unlocated image can be established based upon the position of a previous located image and a maximum velocity or acceleration of the pen.

Abstract: X-y positions of a digital pen's tip may be determined by using a calibration parameter to map the x-y positions of the respective centers of images captured by the pen's camera. The calibration parameter may be generated by iteratively calculating estimates of the calibration parameter. Calibration input data may be produced by a user placing the pen tip in a fixed location on a surface, which may be a positionally encoded medium, such as paper, and then rotating the pen and/or moving the opposite end of the pen in various directions to capture multiple images for use in generating the calibration parameter. A user may perform such a calibration procedure without the need for complicated calibration equipment typically used in connection with conventional calibration techniques.

Abstract: An input device and method for generating electronic ink and/or other inputs is described. The input device may be used in combination with any surface through the use of an improved movement sensing technique for generating data for use in ink related applications and non-ink related applications. Improved motion sensing may be achieved using one or more inertial sensors for detecting movement of the input device by measuring such indicators as velocity, acceleration, and changes in electro-magnetic fields. The input device may include a memory for storing movement data and a transceiver for transmitting data representing movement of the input device to a host computer. Processing of the sensed movement data to generate images representative of hand written strokes may also be performed using a processor within the input device. The input device may be formed in the shape of a pen, and may include an ink cartridge to facilitate movement of the input device in a familiar manner.

Abstract: A system and method for encoding a document image and finding a location based on that image are described. A document page is encoded into codes associated with various locations of the document page. The codes are assembled into a code book. Captured images may then be similarly encoded and searched against the codes in the codebook. One or more codes and associated locations may be returned, thereby providing one or more possible locations for the captured images.

Abstract: A system and process for determining the location of a captured image from a larger image is described. Using a list of determined locations, the system is able to determine the best or most likely path of a pen tip.