Abstract: A pen positioning system is provided, in which a pen, having multiple output elements, is adapted to accurately determine the location of the pointing tip of the pen, in relation to an electronic tablet. The output elements, preferably ultrasonic transmitters having distinct frequencies, are located a fixed distance from each other, and are also related in space to the pointing tip of the pen. The geometric relationship between the output elements and the pointing tip of the pen allows the location of the pointing tip to be determined, independent of the angle which the pen is inclined against the surface of the writing tablet. A detection system is used to receive the output signals from the output elements, isolate the output signals from each other, and process them independently to determine the location of the output elements and of the pointing tip of the pen.

Abstract: A method and apparatus for image classification includes a first embodiment, in which halftone detection is performed based on the size of a boundary set between a class of light pixels and a class of dark pixels, and further based upon image information contained within each single image plane (i.e within one color plane). This embodiment of the invention is based upon the distinctive property of images that halftone areas within the image have larger boundary sets than non-halftone areas within the image. A second, equally preferred embodiment of the invention provides a cross color difference correlation technique that is used to detect halftone pixels.

Abstract: An arrangement for producing a variable width pulse is disclosed for use in an electrostatic printing mechanism which is adapted to produce grayscale intensity of a pixel to be printed based on predetermined digital data. The variable width pulse is formed during a clock interval which is established by a clock signal such that the width of the pulse during the clock interval is based on the digital data and corresponds to a grayscale intensity of the pixel to be printed. The arrangement includes at least a first delay line including an input, an output and a plurality of cells serially connected therebetween such that a digital signal received by the input propagates from the input to the output through the cells. Each cell includes a cell output for indication of the present state of digital data contained in the cell. A pulse generating section then provides the clock signal, as the digital signal, to the input of the first delay line such that the clock signal propagates through the first delay line.

Abstract: A technique is described for adding variable data to a print job, while requiring a minimum amount of storage. Key to the invention is the use of a data compression algorithm during RIPing. During a first stage of operation, a master document is RIPed into a compressed format and saved in a cache, such as RAM or disk storage. It is important to note that RIPing and data compression are performed simultaneously. This minimizes the amount of processing power necessary to RIP and compress a large document, while significantly reducing the amount of storage space required to save the RIPed master document. The variable data document is RIPed and compressed during a second stage of operation using the same algorithm as applied to the master document. Uniquely, the variable data document is RIPed directly onto the master document in compressed format. During the second phase of operation, the master document to be personalized is retrieved from memory and stored in a frame buffer.

Abstract: A method and apparatus for creating threshold arrays having a minimized gray scale variance without geometric artifacts. The invention comprises the steps of processing each candidate pixel in the threshold array using a variance minimization technique and applying a sparse image calculation on the same pixel. The preferred embodiment of the invention comprises the application of a variance minimization technique on a threshold array. The threshold array is analyzed on a pixel-by-pixel basis. Each candidate pixel that is to be turned on is examined in relation to the previous pixels that already exist. The candidate pixel is examined to determine its effect on the variance of the smoothed gray level determined by the convolution of the pixel pattern with a smoothing kernel. The candidate pixel is also examined in relation to the distribution of the angles it forms with the previously selected pixels. The preferred embodiment uses a variant of the combinatorial Hough transform.

Abstract: A robotic plotting system 10 is provided, in which a robotic plotter 18 having a printhead 18 is placed on a substantially flat horizontal surface 23, upon a recording medium 22, and is directed across the medium 22 by ranging signals 16 transmitted to the printhead 18 from the periphery of the recording medium 22. In one embodiment, the robotic printhead 18 includes a motorized drive mechanism 26, 28 that propels it across the surface of the recording medium 22 in a controlled manner, for example using microwave control signals 16. Thus, a user can place a piece of paper 22 of any size on a flat surface 23 such as a table or floor, and the printhead 18 is propelled across the surface 23 and is directed by signals 16 beamed between the printhead 18 and a control mechanism 14. In this manner, a large-surface-area plotting system 10 is provided in the form of a small hand-held device.

Abstract: A transducer signal waveshaping system is provided, in which a signal excitation circuit includes a non-linear device. The resulting circuit produces a short input pulse, which allows a piezoelectric transducer to transmit a shortened output signal having distinct waveshape characteristics. The resulting waveshaped output signal, typically an ultrasonic signal, provides a measurable time-dependent signal that is particularly suited for data entry systems, such as for movable transmitter pens and white boards. The location of the transmitter pen in relation to the writing area of a white board can be determined, using the periodic transmission of the waveshaped output signals. Alternative embodiments include additional circuit elements, which allow the resulting waveshaped output signal to include even more distinctive waveform features.

Abstract: A blank is provided for producing color swatches on a color printer or photocopier. A sheet adapted to be fed through the printer or photocopier contains a first set of perforations defining the perimeter of a swatch card. A second set of perforations disposed within the perimeter of the swatch card defines a plurality of openings. The openings are punched out, preferably after color swatches have been printed on the swatch card, in order to enable the viewing of a sample color through the opening for comparison with the color swatches. A third set of perforations is provided in a corner of the swatch card to enable a plurality of swatch cards to be assembled into a reference deck by passing a fastener through holes formed via the third set of perforations. Each sheet can have a plurality of swatch cards laid out therein, with each swatch card containing a plurality of color swatches.

Abstract: A display interface system that uses a server-client approach. The server contains all of the necessary information regarding display information, while the client deals with the specific display type that it is connected to. The server contains generic descriptions of user interface screens which allow the server to be independent of specific display types. This allows one version of software to support many types of displays, rather than several software revisions for each display type, saving the software developer time, maintenance, and labor costs. A request-response communication system is used whereupon the client requests previous or next user display screens, system parameter requests, or updates from the server. The client requests screen information through a series of key-tag sequences, while the server controls the sequencing of the user display screens. The client is shielded from any knowledge of the contents of the screen and is only concerned with the fact that something is being displayed.

Abstract: A silicon switch is provided. A silicon member biases a contact into abutment with an opposing contact located on a substrate such that a normally closed switch is provided. A plunger is provided which has an axis that extends along the axis of the two contacts. The plunger is secured by the silicon member in such a way that pressure on the plunger causes the switch contacts to open. When pressure is released, the bias built into the silicon member pushes the contacts back together. The switch is intended for use in a pen, for example in a white board application, where pressure of the pen to a marking surface forces the plunger upwardly into the pen and thus opens the switch contacts.

Abstract: A system for printing and copying color and black-and-white documents avoids the need for manual collating. The system provides N sets of documents using a printer and a copier, where each set of documents includes a first type of sheets (such as black-and-white sheets), and a second type of sheets (such as color sheets) provided in a particular sequence in relation to the first type of sheets. A first complete document set is printed, including the first and second types of sheets, along with N-1 insert sets of the second type of sheets, and an instruction sheet indicating the particular sequence. The first complete document set is positioned in a document feeder of the copier, and the N-1 insert sets are positioned in a post-process insertion tray of the copier.

Abstract: The present invention is a method and apparatus for computing color transformations of source images. It performs color transformations using a lookup table and a hashing block for referencing entries in the lookup table. The index generated by the hashing block is dependent on a first color value. A color encoding block is coupled to the lookup table for generating an encoded color value dependent on the first color value. The index produced by the hashing block is further dependent upon response characteristics of the human eye. The hashing block generates indexes referencing widely separated entries in the plurality of entries of the lookup table when first color values have small differences in value. A comparing block is coupled to the lookup table and the color encoding block for comparing the entry of the lookup table and the encoded color value to determine a match. A color calculation block is coupled to the lookup table for generating a second color value dependent on the first color value.

Abstract: From a raster page, patches of connected pixels of the same color are identified. Patches of at least a predetermined sized, typically corresponding to text or line art objects, are subjected to a lossless compression. Patches below the predetermined size, typically corresponding to image or photo objects, are substantially subjected to a lossy compression. The patch predetermined size controls the mix of lossless and lossy compression procedures. Optimum compression is achieved by maximizing the lossless compression while attaining a targeted compression ratio. Various features include efficient recognition and encoding of patches, refined treatment of the boundaries between the lossless- and the lossy-compressed pixels, adaptive compression ratio control, and fail-safe compression provisions.

Abstract: A transmitter device is disclosed for use with a conventional pen in which the ultrasound transmitter is a cylindrical element lying coaxial with the pen and adjacent to its tip, and a jointed eraser structure. Conventional triangulation techniques are used to track the position and motion of a writer or eraser. An encoding facility associated with the pen provides the ability to distinguish whether the pen is used for marking or an as erasing implement, as well as determining the nature or character of written line width or eraser swath. A data stream thus generated can be used in a variety of ways, such as for example, to feed information into the memory of a digital computer, and/or to feed information for transmission to remote stations.

Abstract: Interleaved data are converted to a planar format by an algorithm that follows map cycles throughout a frame buffer. Such map cycles result from iterating a function that maps planar addresses to CMYK addresses. There are three phases to the algorithm: In phase I, a 1-Cycle is processed and all of its member indices that are <=MAX.sub.-- HIT in the array firstHit? ! are saved. In phase II, all indices between 1 and MAX.sub.-- HIT are visited, skipping any indices that have already been in a cycle. As each cycle is converted, any hits to indices between 1 and MAX.sub.-- HIT are directly recorded in the array hit? !, so that indices that have been used are quickly skipped. Phase III is skipped unless there are still some copies left to process. In phase III, there is no more space for recording every hit individually. When looking for new cycles, only indices that are not multiples of anything in the 1-Cycle are considered.

Abstract: A image is printed from a source of drawing instructions. The image is reducible to pixels arranged in a plurality of ranked image lines. The system employs a storage device having compressed and uncompressed regions. Each region has a designated capacity and each is arranged to store pixels of one more of the plurality of image lines. A drawing processor is coupled to the storage device and can be coupled to the source of drawing instructions for responding thereto. This drawing processor can store new pixels in the storage device for successively selected ones of the image lines. The drawing processor has a conditional device, a decompression device and an insertion device. The conditional device can compressively encode and move from the uncompressed region to the compressed region, a remote one of the image lines, if: a) the selected one of the image lines is in the compressed region, and b) the uncompressed region has reached its designated capacity.