Abstract: A circuit used in laser scanners which allows the continuous calibration of a laser so that the output power of the laser is accurately modulated by the input video signal regardless of temperature changes or aging effects of the laser. The video signal includes a test segment which has two steps. The light output of the laser is measured during both steps. The lower step measurement is compared to a reference and the error is used to adjust the bias current of the laser. The difference between the upper step measurement and the lower step measurement is compared to a second reference and the error is used to adjust the gain of the video signal so that the variation in laser power maximum and minimum remains calibrated.

Abstract: A Local Area Network (LAN) is disclosed which enables a generalized data communication facility to be established over ordinary telephone wiring. The disclosed technique provides a completely general LAN architecture with any access protocol and is well suited to CSMA/CD (carrier sense, multiple access with collision detection). The invention consists of architectural and circuit techniques which enable the construction of a local area network(s) (LAN) over ordinary wiring within a building or between buildings within a short distance of each other (often called a campus). The LAN is implemented without disturbing the normal voice function of the telephone circuits and without the need to string addirional wiring. Implementing a LAN in accordance with this invention only requires three types of hardware functional elements (in the appropriate quantities for the application): (a) a Node Unit (NU), (b) Repeater Unit (RU), and (c) depending on the size of the network, possibly a Pulse Regenerator Unit (PRU).

Abstract: This invention relates to an electro-optic modulator device, such as a multi-gate light valve for an electro-optic line printer, wherein the different elements are uniquely combined in a package utilizing VLSI principles. A specially designed integrated circuit package is utilized to enable the bonding of one or two electro-optical devices as a single unit. As each electro-optical device has its chip pads at one end of the device, special modifications need to be made to joint the pads to the external connectors. The electro-optical crystal, which may be mounted on a glass plate, is bonded to the integrated circuit chip. Sonic bonding or the two layer metal technique may be used for the crystal to chip bonding.

Abstract: This circuit is an input noise filter. An RC circuit comprises a capacitor implemented from a transistor with source and drain tied together and a long transistor acting as a resistance which can either be large or small, depending on the bias. The output of the RC circuit is applied to a comparator where it is compared to a threshold voltage. When a signal is first applied to the input, the resistance is high, so that the RC circuit charges slowly. With the input signal still applied, after the comparator threshold is reached and the output from the comparator goes high, a feedback circuit senses the output and decreases the resistance, allowing the RC circuit to rapidly charge up. Finally, after the input signal ends, the feedback loop again raises the resistance to allow the RC voltage to discharge slowly to the threshold level, after which the comparator output goes low. The result is a circuit that does not shrink the digital input signal but still filters out input noise.

Abstract: A polygon system for correcting wobble by double reflection from the active facet without bow is disclosed. Instead of the impinging light source being transverse to the axis of rotation of a rotating polygon, this rotating polygon 12 having facets at a draft angle to the axis of rotation, a collimated light source 10 impinges upon a rotating polygon 12 with the facets 22 having the predetermined draft angle D. A., and angles of incidence at the first and second reflections. By two further relections, 18, 20, the light is then reimpinged upon the same facet; wobble is similarly corrected, but with no effects of bow.

Abstract: This bubblejet device has integrated into it a number of heater resistors and a temperature sensor which operate in conjunction with a temperature regulating circuit to heat the chip to its optimum operating temperature within seconds of turn-on, and thereafter maintain that temperature regardless of local temperature variations. The precise temperature regulation of the array improves print quality.

Abstract: This invention relates to a pyramid polygon scanner without cylinder optics wherein the effects of jitter are reduced by the use of a start of scan detector situated at a predetermined angle from the normal (vertical) position. The start of scan detector is rotated about an axis through the nominal scan line. Thus, if tilt (not the draft angle) is present in the rotating polygon system and jitter is generated, the rotation angle of the split detector moves the jitter to the beginning and end of scan, leaving the center of scan free of the effects of jitter. The angle of the split detector is in approximate relation to the angle of incidence at the first reflection on the rotating polygon.

Abstract: A method for generating a variable frequency clock pulse for a raster scanner. First, a correction number, which may be the sum of corrections for scan-nonlinearity, polygon signature errors and motor hunt errors, is generated. This number is then added periodically to a running sum. The most significant bit of this sum is then available as the clock pulse output. The frequency of the output clock will be proportional to the correction number. The described circuit uses an accumulating adder and a register loop to form an accumulator circuit. The correction number is then supplied to the other accumulator adder input, and the register is clocked with a fixed frequency sample clock pulse.

Abstract: A magnetic disc drive brake assembly which automatically locks the disc drive when it is removed from its case. As the disc drive is lifted, a spring is released, which spring forces a brake pad into contact with the disc drive hub, thus locking the disc drive in place. Reversing the process automatically releases the disc drive.

Abstract: The ink in an ink jet is sensed by a capacitor, one plate of which is coupled to ground through the ink. The absence of ink will appear as a decreased amount of capacitance. In this case the charge of the capacitor will leak off faster, and a sample and hold circuit can sense this to output a signal indicating the absence of ink. The charging signal can either be generated on the chip, which is made from silicon, or can be supplied to the chip. The number of pins on the chip taken for this sensing function can be minimized by multplexing the states of signals supplied to the chip for other purposes to generate the necessary signals to control and operate this sensor.

Abstract: A simplified method for rotating a digital image through a small angle without the need for interpolation is described. The image is divided into small, square blocks, arranged in horizontal rows where each block is exactly to the left or right of the other blocks in the row, and into columns where each block in the column is offset to the right by one pixel with respect to the next higher block. The rotation is then accomplished by moving the lower rows to the left so that the columns are exactly vertical, and by moving the rightmost columns in a downward direction so that each block is one pixel below the block to its left. The result is a rotation of the image through a small angle. There is a considerable simplification gained from not rotating the data within each block which results in a slight distortion of the image, but for small angles, this is not noticeable.

Abstract: This invention is an input device, or stylus, for entering hand drawn forms into a computer comprising a writing instrument, a pressure switch for determining whether the instrument is in contact with the writing surface, an acoustic transmitter for triangulating the position of the stylus on the surface, and a wireless transmitter for transmitting data and timing information to the computer. In operation, the stylus transmits an infra red signal which the system receives immediately, and an ultra sound pulse which two microphones receive after a delay which is a function of the speed of sound and the distance of the stylus from each microphone. From this information the system can calculate the position of the stylus. Switches for indicating functions are mounted on the stylus. Multiple stylusses can be used, each transmitting a distinctive identification code so that the system can determine which stylus is the signal source.

Abstract: A method of converting an outine defined by a plurality of vectors into an optimum set of trapezoids which can be filled in using standard printer techniques. The process is to determine all points in the outline where two vectors intersect, and the location of all scan lines that intersect these points. Then a winding number is calculated for each trapezoid formed by the scan lines and vectors, and Fill or Not Fill states are assigned to all trapezoids. Finally, all adjacent Fill areas separated by vectors are joined to form a final set of trapezoids which define the area to be filled.

Abstract: In a liquid toner xerographic system, a sheet of matted polyester is held against the back of the selenium xerographic plate as it passes the transfer station to absorb the toner on the back and leading and trailing edges of the plate. The material is supplied by supply and take up rolls and is advanced a predetermined amount for each passage of the plate. The material is located above the transfer station to clean the transfer wiper in the absence of a plate.

Abstract: A registration mechanism for offsetting paper sets against a registration edge which is alternately in an inboard and an outboard position. The paper sheet is urged against the registration edge by means of two rotating urathane paddle wheels positioned relatively closely to the registration edge, but the sheet is prevented from generating too much angular velocity by two restraining means in the form of TEFLON balls held in retainers which prevent the balls from moving laterally but allow the balls to move vertically and rotationally, these restraining means located relatively further away from the registration edge. Because the mechanism is operating in the absence of a sheet of paper most of the time, a freely spinning roller is provided in a space in the base plate under each wheel which normally is driven by the wheel in the absence of a sheet of paper at a speed sychronous to that of the wheel, thereby lessening the wear on the wheel.

Abstract: This color copying system scans the original with a raster input scanner to generate digital signals representing red, green and blue, and prints at a raster output scanner which uses cyan, magenta, yellow and black ink. In addition, under color removal is used, that being defined as the removal of a certain amount of ink from all three colors, and the addition of an equivalent amount of black ink. The first step is to convert the input scanner colors into the color being printed during the current revolution of the printing drum. This requires the solution of three equations, each of which use three look-up RAM tables. In addition, the amount of under color removal must also be calculated before the amount of ink for the dot being printed is known. This requires an additional table look-up. Finally, for the black cycle, the amount of black ink must be calculated, requiring another table.

Abstract: This invention is an infeed mechanism for a sheet fed printing machine comprising a chute for guiding a sheet from a staging position into an array of moving grippers. To improve the reliability and accuracy of placement of the sheet leading edge into the gripper throat, a plurality of flexible strips, each longer than the one above, is attached to the chute bottom edge facing the grippers, the strips coming into sequential resilient contact with the open gripper fingers. The strips therefore become a flexible extension of the lower edge of the chute and serve to constrain the sheet lead edge movement into the moving gripper fingers regardless of instantaneous mechanical misalignments and sheet imperfections.

Abstract: A circuit for correcting the write power of a laser raster output scanner as it scans across the write drum. During calibration, a piece of glass reflects part of the beam into a photo multiplier tube, the output of which is converted into a digital signal. This is compared to a reference signal. The difference for each segment of the scan is stored in RAM and also is converted back to an analog signal to modulate an acousto-optic modulator in the laser optics to correct the write power. After the system has settled to a point where the write power at the drum does not vary across the scan, the glass may be removed and the system operates using the corrections stored in RAM.

Abstract: An improved on-chip bias generator for producing a negative bias for the substrate of a VLSI FET chip for reducing the body effect and for increasing circuit speed. The improvement comprises active FETs to rectify a ring oscillator square wave output, thereby reducing the voltage losses in the rectifier and increasing the amount of voltage delivered to the substrate.

Abstract: A circuit for producing a "knight ordered dither" halftone pattern for a CRT and a "double spiral" halftone pattern for a xerographic printer is described. The circuit comprises a RAM for storing the threshold values, a comparator, and supporting addressing and logic parts. Also described are a program for allowing the operator to interactively generate threshold patterns, and several knight tour patterns specifically designed for a CRT using interlaced rasters.