Abstract: A densitometer with a controllable light emitter intensity operates to reduce excessive exposure of sensitive materials, such as photoconductive film. During normal printer operation, the emitter is operated in a pulsed-mode, thereby reducing emitter temperature and prolonging its useful life. Exposure of the photoconductor is also reduced, which may prolong its useful life and avoid image defects. The pulse width, frequency, and duty-cycle are chosen to give these benefits without compromising density measurement capability. The emitter drive circuitry is connected to a motion sensor so that emitter intensity is reduced to a low level when photoconductor motion is stopped. A test mode is provided during which the emitter intensity is reduced by a calibrated amount, simulating the presence of a calibrated test sample.

Abstract: A method and apparatus of generating rendered image data for use in reproducing an image with a series of patterns of halftone dots. In the method and apparatus an unrendered pixel value of a pixel to be rendered is compared with each of a series of threshold values in accordance with respective comparison criteria and a grey level for a rendered pixel of a halftone dot is generated by having certain threshold values define increasing grey level values of the rendered pixel upon meeting respective criteria and at least one threshold value of the series defines a decrease in grey level value of the rendered pixel for meeting a respective comparison criteria.

Abstract: An auto-ranging digital densitometer, for determining the optical density of a test sample, includes a photodetector and a digital logarithmic converter. Within the logarithmic converter, an amplifier circuit is adapted to produce an output signal proportional to intensity of light incident on the photodetector. The amplifier circuit has multiple gains that successively increase, one to the next, by a ratio between 2.3:1 and 5.7:1. Gain select logic selects the gain to provide good density resolution and avoid amplifier saturation. An analog-to-digital converter is adapted to convert the output signal of the amplifier circuit to digital format. A lookup table address is formed at least in part from the output of the analog-to-digital converter. The lookup table outputs at least the lower-order digits of the density value corresponding to the gain and the amplifier output. Density range is extended, resolution improved, and the requirement for a second lookup table is eliminated.

Abstract: A densitometer with built-in data processing capability uses synchronizing signals to collect data at defined spots on a moving endless belt or drum test sample. A calibration cycle accumulates data for later use in measurement correction. After correction, measurement data are output or stored for later output to a host processor or display device. Data averaging, filtering, smoothing, statistical functions, and pattern recognition are also provided by the densitometer circuitry.

Abstract: An auto-ranging densitometer is disclosed for determining the density of a test sample, wherein the densitometer includes a photodetector and an amplifier circuit adapted to produce an output signal proportional to intensity of light on the photodetector. The amplifier circuit has multiple gains that successively increase in an approximately 2:1 ratio increment. An analog to digital converter is adapted to convert the output signal of the amplifier circuit to digital format. A density signal generator circuit is adapted to receive the output of the analog to digital converter, whereby density resolution non-uniformity is minimized due to small gain increments such that the analog to digital converter needs deal with less extreme variations in density resolution.

Abstract: An auto-ranging densitometer includes a photodetector and an amplifier circuit adapted to produce an output signal proportional to intensity of light on the photodetector. The amplifier circuit has multiple gains that successively increase. An analog to digital converter converts the output signal of the amplifier circuit to digital format. A gain select logic outputs a gain code used to select the gain of the amplifier. A density signal generator circuit includes two LUTs, one of the LUTs being adapted to receive the output of the analog to digital converter and produce an output density scaled to include only low order bits; and the other of the LUTs being to receive the gain code and produce an output density scaled to include only high order bits. The outputs of the two LUTs are concantenation added to produce a summation density signal.

Abstract: An optical densitometer includes a receiver adapted to produce an electrical output voltage characteristic of an optical density to be measured. A voltage-controlled oscillator produces a periodic signal having an output waveform with a frequency and period characteristic of the output voltage of the receiver. A counter produces a digital value corresponding to the output waveform of the periodic signal produced by the oscillator; and a converter produces a digital optical density signal from the digital value. The counter is adapted to produce its digital value corresponding to the frequency or period of the periodic signal produced by the oscillator. The counter may include a portion adapted to produce a digital value corresponding to the frequency of the periodic signal produced by the oscillator; and a portion adapted to produce its digital value corresponding to the period of the periodic signal produced by the oscillator.

Abstract: An electrostatographic recording apparatus and method includes a primary charger establishing a uniform primary electrostatic voltage level on an image recording member. A recorder imagewise modulates the electrostatic charge on the image recording member to form a latent electrostatic image. A development station develops the electrostatic image with toner. A controller controls the primary charger by periodically adjusting a signal to the primary charger in response to a signal related to charger efficiency. The charger efficiency is determined as the ratio of the charger's grid voltage to a voltage level established on the recording member. To calculate changes to the grid, voltage control patches are printed on the member and the densities used to determine changes to setpoint values for the charger.

Abstract: An electrometer probe is used in an electrophotographic apparatus as part of a process control system to measure charge on a photoconductive film belt. This measurement is used to control voltage level or other process parameter of the electrophotographic process. The probe is supported in an electrometer probe holder so that a sensor aperture of the probe is at a fixed distance from the film belt. In order to ensure proper operation of the electrometer probe, a method and an apparatus for independently calibrating the electrometer probe is provided. A curved plate is provided on the electrometer probe holder. The plate is mounted at the same spacing from the probe aperture as the film belt. This plate has a receptacle for the service person's test lead to attach. The other end of the test lead is attached to a test point for the toning station bias supply. The probe may be reoriented on the probe holder to position the probe aperture at the fixed distance to the plate.

Abstract: A reproduction apparatus and method particularly suited for an electrophotographic DAD-CAD system having an electrostatic recording member for supporting an electrostatic image, a primary charger establishes a primary charge on the member, the primary charge being defined by a parameter V.sub.o. An exposure device imagewise modulates the primary charge to form an electrostatic image on the recording member. The device has an exposure parameter E.sub.o. A developer station develops the electrostatic image with charged toner. The developer station has an electrical bias to establish a field for urging movement of the toner to the member. The electrical bias has an alternating current component parameter AC and a direct current parameter DC. A controller controls adjustments to the parameters E.sub.o, V.sub.o and AC by measuring a density parameter D.sub.OUT of an exposed and developed area on the member that is formed by operation of the primary charger, the exposure device and the developer station.

Abstract: In an electrostatographic process wherein images are formed on an electrostatic image supporting medium and developed by a development station having a developer formed of a mixture of toner and carrier particles, there is provided apparatus for controlling various processing control parameters in response to formation of a toned patch on the medium. The apparatus includes a first feedback controller that processes signals related to the parameter toning contrast in accordance with a closed loop control of this parameter. The first feedback controller serves as a toning contrast controller and outputs a first signal representing toner concentration set point in response to closed loop control of toning contrast. The apparatus also includes a second feedback controller means that is slaved to the first feedback controller and serves as a toner concentration (TC) controller.

Abstract: In an electrophotographic apparatus, an apparatus and method is provided for controlling reproduction by controlling adjustments to the parameters V.sub.o and E.sub.o. A density parameter D.sub.OUT of an exposed and developed maximum density patch is measured. An error, .DELTA.D.sub.OUT, in the measured density parameter is calculated from a density setpoint. The error, .DELTA.D.sub.OUT is multiplied by first and second constants to obtain respective adjustment values used for adjusting E.sub.o and V.sub.o. The control operation is repeated periodically to provide new adjustment values that are used for adjusting E.sub.o and V.sub.o and a fixed ratio is always maintained between the first and second constants.

Abstract: An electrostatographic copier or copier/printer apparatus and method for calibrating same with an improved means for adjusting for process control parameters is described. The apparatus includes a scanner for scanning an original document to be copied and for generating signals representing a density characteristic of images on the document. An electronic writer responsive to scanned signals modulates charge on an electrostatographic recording member to form a latent electrostatic image. The latent image is developed and transferred to a record member. Them are provided further means responsive to rescanning of the record member by the scanner for generating adjustment signals for correcting for calibration errors in processing of an image, and the writer is responsive to the adjustment signals. The writer may thereby correct for nonuniformities in a direction transverse to said process direction.

Abstract: The voltages, V.sub.0, on a photoconductor surface are measured over a wide range of grid voltages, the results of which are stored in a look-up table V.sub.grid vs. V.sub.0. The updated V.sub.grid /V.sub.0 look-up table permits automatic and accurate adjustment of the primary charging step in the electrographic cycle. This method accommodates any number of desired V.sub.0 levels over a wide range of voltage. The present use establishes the relationship without going through a lengthy iterative procedure inherent in using feedback adjustment loops. The calibrated look-up table is updated as often as is required to compensate for such things as aging, wear, and environmental changes, to name a few. Calibration is repeated and the entire look-up table is updated after certain intervals of time or usage, or whenever drift is detected at even a single point of the V.sub.grid to V.sub.0 relationship. This compensates for the variability of corona charging over time as well as over a range of V.sub.0 's.

Abstract: A method and apparatus for corona-charging a charge-receiving member having image frames used in recording, such as in electrostatographic recording. In the method and apparatus there is synchronizing movement of the charge-receiving member with the application of different voltages to the corona-charging apparatus. Thus, during a transition period when a region of the charge-receiving member that is adjacent a leading edge of an image frame is aligned with the charging apparatus, an element of the charging apparatus is provided with an overcharge voltage level substantially higher than a voltage level suitable for achieving on the image frame an aim point voltage level to which the image frame is to be charged to provide a relatively rapid rate of charge deposition on the charge-receiving member. The voltage on the element is thereafter adjusted to a lower voltage level suitable for achieving an aim point voltage level on the image frame. The element is preferably a grid but may be a corona-charging wire.

Abstract: An apparatus for controlling the transmission density of a layer of pigmented thermoplastic marking particles (e.g., electrographic toner) being deposited on a dielectric film or layer by an electrically biased particle applicator. Such apparatus uses (a) an electrometer for producing a first signal proportional to the level of electrostatic charge on the film after such particles have been applied thereto; (b) a charge-to-mass determining device for producing a second signal proportional to the electrostatic charge-to-mass ratio of the particles applied to the film surface; and (c) a bias voltage controller responsive to the first and second signals for controlling the electrical bias on the particle applicator to control the mass per unit area of the particles applied to the film surface.

Abstract: The need for adjustment of the transfer and fusing subsystems of an electrostatographic machine is determined by adjusting the machine's process control parameters until density reading of an untransferred toner image of a test patch are within specification, or are otherwise acceptable. The toner image is transferred and fused to an image receiver sheet, and deficiencies in the images on the receiver sheet indicate the need for adjustment of the transfer and/or fusing subsystems.

Abstract: Test patch densities are accurately determined during automatic set-up procedures, regardless of non-uniformities in the amount of wear and scumming from one part of the image receiver to another, or of variations in the coatings applied to the image receiver during manufacture, by correcting densitometer readings by obtaining density readings on the untoned image receiver during a cycle-up portion of the automatic set-up operation, saving the readings, and subtracting the saved readings from subsequent test readings of the same portion of the image receiver.

Abstract: Densitometer readings are corrected by obtaining density readings on an untoned area of the interframe region of an image receiver during cycle-up, storing the readings and subtracting the stored readings from subsequent test readings of the same area of the image receiver. Differences between the cycle-up readings and test readings are used to adjust density readings of toned reference patches obtained with the test readings. The procedure can be used during production modes of the machine, with all readings being taken in the interframe regions, or the procedure can be a part of an automatic set-up operation with toned reference patch readings being taken in the image frame areas of the image receiver.

Abstract: An electrophotographic copier uses a first light source to copy reflection originals and uses a second light source to copy transparency originals. Operation of the copier is adjusted to attain a desirable copy image of reflection originals using the first light source, and then the second light source is used to expose a patch on the image receiver through a test transparency of predetermined optical density. When the patch is developed, its optical density is compared to an aim value, and any difference is used for adjusting the exposure value of the second light source.