Abstract: An adaptive threshold for processing grayscale image data obtained by scanning a document to be duplicated is set by initially dividing the data into data groups representative of selected pixels of the document. A background grayscale value and a print grayscale value are determined for each data group with the difference between the two defining a contrast grayscale value. An estimated threshold is calculated by adding 0.4 of the contrast to the background. An average threshold is also determined for the area of each data group by averaging the thresholds for contiguous data groups for which thresholds have been established. The adaptive threshold is determined for each data group by setting the adaptive threshold to the average threshold +1 if the estimated threshold exceeds the average threshold; to the average threshold -1 if the estimated threshold is less than the average threshold; and, to the average threshold otherwise.

Abstract: Scanned image data is assembled to represent scanned strips of a document each strip comprising a plurality of scanned lines. The lines of each strip are read in parallel to form data words defining columns of the scanned strips. The data words are encoded by means of Huffman and run-length coding to generate fixed-length coded words which are concatenated to represent the document. Each strip of coded words is reviewed and uncoded data is substituted for coded data in the event the coded data exceeds the uncoded data. Text data and continuous tone data are encoded using different encoding techniques due to their varying characteristics. Synchronization words are used to prefix all coded data strips; to prefix and suffix all uncoded data strips; to define all white and all black strips; and, to indicate changes in data type, i.e., text to continuous tone or vice versa.

Abstract: An ink drop duplicating system employs a plurality of angularly extending ink drop print heads to reproduce an original document. Each printing head produces a row of drop streams which are individually controlled to deposit printing drops at a plurality of printing positions along a line extending perpendicular to the major axis of the printing head. Printing control information for the ink drop printing heads is generated by a photosensing array which extends across one major dimension of an original document and which is scanned across the other major dimension. Scanning data is stored on a magnetic disk. After one or more original documents have been completely scanned, the scanning data is read from the magnetic disk and reorganized to produce drop control signals for the ink drop printing heads.

Abstract: A print system for duplex printing a plurality of document page images on a plurality of copy sheets includes means for storing print control information which defines the document images. An ink jet printer prints the page images on copy sheets as they are transported past a print station by a transport arrangement defining a closed sheet path. The sheet path is of sufficient length such that a number of copy sheets are transported simultaneously therethrough. A copy sheet inverter receives copy sheets sequentially from the sheet path after the sheets are printed on their first sides and returns them to the sheet path in an inverted orientation prior to printing on the second sides of the copy sheets.

Abstract: A display processor is disclosed that receives digitally encoded text data and generates video data signals to produce video images of dot matrix alphanumeric characters on a cathode ray tube display in a format that emulates a full page of typewritten copy. The display processor receives ASCII coded character data and digitally encoded text manipulative data and generates horizontal sync, vertical sync and video data in the form of a display scan line dot pattern. The display processor includes a display refresh memory for storing coded text and manipulative data, a character generator including a font memory and video output circuitry. Operation of the display processor is under a set of microcoded instructions outputted from an internal instruction generator in a repeating program sequence, with a random access memory being utilized to store refresh memory read and write addresses and other data required during execution of the program sequence.

Abstract: A human touch on an etched copper electrode produces a capacitive change to vary the time constant of an RC network as a part of an oscillator. The variation in the capacitance of the sensor changes the time constant of the RC network which results in a change in frequency of the output signal of the oscillator. This change in frequency thus varies with the human touch to the copper electrode. To develop a directional indication of the touch position, four electrodes are arranged in opposed pairs along orthogonal axes. Each electrode is part of an RC network connected to an oscillator with each of the four oscillators identified with one of the four positions along the orthogonal axes. The output signal from each of the oscillators is transmitted to timing and control circuitry that generates four separate pulse trains, one pulse train identified with each of four positions along the orthogonal axis.