EP0156217A1 - Méthode et dispositif pour obtenir une valeur prédéterminée de potentiel lors de l'illumination de couches photo-conductrices chargées électrostatiquement - Google Patents

Méthode et dispositif pour obtenir une valeur prédéterminée de potentiel lors de l'illumination de couches photo-conductrices chargées électrostatiquement Download PDF

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Publication number
EP0156217A1
EP0156217A1 EP85102575A EP85102575A EP0156217A1 EP 0156217 A1 EP0156217 A1 EP 0156217A1 EP 85102575 A EP85102575 A EP 85102575A EP 85102575 A EP85102575 A EP 85102575A EP 0156217 A1 EP0156217 A1 EP 0156217A1
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EP
European Patent Office
Prior art keywords
potential
exposure
voltage
light
detector
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Application number
EP85102575A
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German (de)
English (en)
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EP0156217B1 (fr
Inventor
Klaus Reuter
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Hoechst AG
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Hoechst AG
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Priority to AT85102575T priority Critical patent/ATE39773T1/de
Publication of EP0156217A1 publication Critical patent/EP0156217A1/fr
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Publication of EP0156217B1 publication Critical patent/EP0156217B1/fr
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/50—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control
    • G03G15/5033—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the photoconductor characteristics, e.g. temperature, or the characteristics of an image on the photoconductor
    • G03G15/5037—Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control by measuring the photoconductor characteristics, e.g. temperature, or the characteristics of an image on the photoconductor the characteristics being an electrical parameter, e.g. voltage
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/04—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
    • G03G15/043—Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material with means for controlling illumination or exposure

Definitions

  • the invention relates to a method for maintaining a constant potential ratio in the exposure of electrostatically charged photosensitive layers on supports on which an electrostatically latent image of an original is formed during the exposure.
  • the electrophotographic layer must be manufactured within narrow tolerances and an exposure device, for example a camera, which may have to be adapted to different working conditions from printing plate to printing plate.
  • the exposure control of conventional cameras generally consists of a timer which switches off the shutter and the light source after a preselected time. Improved control is possible with so-called light dosimeters, of which the incoming light is measured in the area of the original and the exposure time is then corrected.
  • an electrostatic recording device with a measuring device in the form of an electrometer for measuring the surface potential of a light-sensitive layer is known.
  • the surface potential of a latent image on the light-sensitive layer is measured, the surface potential being determined as an AC voltage signal, and on the basis of the measured surface potential, various conditions for image generation, such as the charging voltage and the development bias, controlled.
  • a first control device contains a stored program for a sequential control of the latent image-forming device and a second controller contains a stored program for the conditions for forming the latent image by means of the latent image-forming device or for conditions for development by the developing device using output signals to be controlled by the surface potential measuring device.
  • a method for keeping optimal conditions in electrophotographic reproduction in which the carrier is electrostatically charged and exposed to form an electrostatic latent image on a photosensitive carrier and in addition to the electrostatic image of the original on the carrier an electrostatic latent reference image is formed, the potential of which is measured and an adjustable parameter for the reproduction is set in accordance with the measured potential of the reference image.
  • the reference image is generated by forming light and dark areas on the light-sensitive support and accordingly has areas of low and high potential. The potentials of both areas are measured and if the potentials of the reference image deviate from specified target values, the setting parameter assigned to the respective area for the duplication is changed until the potentials of the electrostatic latent reference image are brought to the specified target values.
  • the exposure of the light-sensitive support is insufficient, then the potential is generally too high, signals are generated to automatically adjust the voltage of the lighting device, the width of the slot opening and so on. to correct or to provide a corresponding correction for the potential.
  • the charge of the light-sensitive carrier is insufficient, ie the potential is too low overall, signals are delivered in order to automatically increase the voltage of the charging device or to carry out a corresponding correction of the potential.
  • both the exposure and the charging are inaccurate, signals are delivered to correct both parameters, so that the specified setpoints can be reached after a few copying runs. There is thus a readjustment of the voltage of the charging device and / or an increase in the exposure intensity, the starting point for these corrections being the measurement of the surface potential of an electrostatic latent reference image on the photosensitive carrier.
  • European patent application 0 098 509 describes a method for controlling the electrostatic charging of a photoconductor surface by means of a corona charging device.
  • the charged photoconductor surface is partially discharged by exposure and signals are measured that compare the exposed and unexposed areas enable the photoconductor surface.
  • the charging device is controlled in accordance with these comparison signals.
  • the comparison signals also serve to regulate the light intensity of an exposure lamp Islam and the exposure duration.
  • the corona charging voltage is regulated to a value corresponding to the corresponding levels of the measurement signal and the setpoint if the measurement signal matches a stored setpoint of the unexposed area of the photoconductor.
  • the measurement signal belonging to this corona charging voltage in the exposed area of the photoconductor regulates the exposure lamp in accordance with stored data of the lamp characteristic, which indicate the aging of the lamp, non-linear influences due to voltage fluctuations, shift in the color temperature of the exposure lamp with respect to the photoconductor sensitivity, and the like. take into account in order to charge the exposed surface sections of the photoconductor to the desired surface tension.
  • the corona charging voltage, the exposure intensity and the exposure duration are regulated in such a way that at the beginning of the concreting of the photoconductor there is a predetermined voltage in the exposed surface sections. A continuous measurement of the falling voltage of the photoconductor and the exposure process in the exposed surface sections is not carried out.
  • US Patent 3,438,705 describes an exposure and developing device in which the background density of a copy is automatically determined using a Controlled photosensitive device which scans the material to be copied.
  • the potential obtained during the scanning of the background is applied to the developing plate during exposure to prevent the plate from being overloaded.
  • the exposure is measured which the plate to be developed receives in a background area. From this measured exposure value and the initial potential of the plate to be developed, a new potential is obtained which is equal to the potential which results from the exposure of the plate, and this potential is applied to the development electrode and the plate during development.
  • a control of the exposure time due to the voltage contrast between exposed and unexposed areas of the plate to be developed is not provided. Rather, the potential of the latent image on the printing plate is determined and the conditions which are necessary for image generation are controlled by means of the signal corresponding to this potential. After the measurement, readjustment is carried out until the desired setpoints are reached.
  • the known methods and devices have in common that they do not take sufficient account of any changes in the light-sensitive layers from support to support during the exposure time and do not control the remaining charge of the exposed layer of the support or the exposed plate.
  • the object of the invention is to design a method of the type described in the introduction in such a way that the exposure time of a photosensitive layer of a support is determined on the basis of predetermined potentials or differences on the photosensitive layer discharged by the exposure in the bright areas.
  • an arrangement for carrying out the method is also to be created.
  • the surface potential is expediently measured in a bright area of the light-sensitive layer outside the area of the latent electrostatic image.
  • Various designs of electrostatic measuring probes are known for this measurement, but they generally have the disadvantage that they are not transparent probes and thus the ones beneath them during the exposure Cover part of the light-sensitive layer and it is not discharged and therefore the potential of a residual charge cannot be measured.
  • the target value is specified in accordance with the residual potential of the light-sensitive layer after the discharge of the light areas of the latent image or in accordance with the predetermined potential difference between the light and dark areas of the exposed latent image.
  • a certain residual potential is advantageously stored or readable, and the surface potential that decreases during the exposure is continuously compared with the specific residual potential that is assigned to the predetermined surface potential at the beginning of the exposure.
  • the exposure is ended.
  • the arrangement for carrying out the method which is equipped with a potential detector for measuring the surface potential of a light-sensitive layer of a support, is characterized in that the potential detector is connected to a signal converter which converts the AC output signals of the potential detector into DC signals and feeds them into a control device , which is connected to a shutter in the beam path of an exposure device and whose output signal closes the shutter when a predetermined target value for the potential conditions on the light-sensitive layer of the support is reached.
  • the potential detector of the device is a detector which is equipped with oblique light incidence for transmitted light operation.
  • a detector for vertical incidence of light can also be used, but with the disadvantage that the detector is reflected in the image area or, when used at the edge of the plate, the measured value is falsified by the shadow in the measuring field.
  • the potential detector works according to the known compensation principle, which will be explained later.
  • the advantages are achieved that the exposure time is controlled by monitoring the discharge curve of the photosensitive layer or the voltage contrast between the light and dark areas of the exposed photosensitive layer, whereby a uniform quality of the printed image of the developed photosensitive layer is obtained and larger Tolerances in the physical properties of the photosensitive layer of the printing plates can be compensated.
  • Fig. 1 shows schematically a pressure plate 1, which rests on an exposure table 2 and is held, for example, by suction air.
  • the printing plate 1 has previously been charged to a certain potential by a corona charging device (not shown) and conveyed onto the exposure table 2.
  • An edge strip, for example 20 mm wide, of the printing plate protrudes above the exposure table 2 and lies below a shield 4 of a potential detector 3.
  • This potential detector is generally arranged in a stationary manner on the edge of the exposure table 2, but it is also possible to pivotally mount the potential detector 3 and to pivot over the edge of the pressure plate 1 for each measurement.
  • a measuring electrode 6 is shown schematically in the area of the shield 4 of the potential detector 3.
  • the one side wall of the shield 4 is inclined with respect to the horizontal in order to take into account an oblique incidence of light 5 and thereby to avoid shadow formation by the side walls of the shield 4 on the measuring field to be exposed, which lies within the shield 4, which is open at the top and bottom .
  • the walls of the shield 4 are expediently designed to be very thin, so that their possible imaging on the edge region of the printing plate hardly influences the measurement.
  • the measuring area lying under the shield 4 is, for example, 11 mm ⁇ 15 mm, so that the ratio of the measured exposed area to the unexposed area immediately below the side walls of the shield 4 is one Has magnitude in which an error in the potential measurement, caused by the shadow formation of the side walls of the shield 4, can be kept to a minimum.
  • the measurement of the surface potential of the exposed printing plate 1 takes place with the potential detector 3 outside the actual image area of the printing plate 1, so that a possible image of the contour is also shown Ren the shield 4 does not interfere within the edge area of the printing plate 1, since the fully developed printing plate 1 is usually clamped on a cylinder in a printing press and is usually on at least one side of the edge area of about 20 mm of the printing plate 1 outside the printing zone.
  • FIG. 2 schematically shows a movable potential detector 3 which is moved along an edge of a pressure plate 1.
  • the potential detector 3 is arranged in a holder 7 which can be displaced along a guide 8 in the direction of the arrow A.
  • the bracket 7 is moved for example by means of a cable, not shown.
  • Another possible solution provides a screw spindle for the guide 8 which rotates and thereby displaces the holder 7 which is in engagement with the spindle.
  • the potential detector 3 is guided in any case by motor along the guide 8 over an edge region of the pressure plate 1.
  • a surface potential distribution serving as the reference standard for the light-dark distribution in the template is indicated by the shaded dark areas 9 I to 9 X and the light areas 10 lying between them in a stripe pattern.
  • the hatches of different densities in the dark areas 9 I to 9 X indicate the different surface potentials in the corresponding dark areas.
  • the ratio of the widths of the dark range to the bright areas is 1: 1 and the area width is adapted to the resolution of the potential detector and is in practice between 1 and 8 mm.
  • the stripe pattern is obtained by imaging a bar pattern together with the original, which is adjacent to the original and whose density densities are known in the dark areas.
  • the stripe pattern of light and dark areas is located in the edge area of the printing plate 1, which lies outside the printing zone when the printing plate is clamped onto the printing cylinder, so that this is not impaired by the stripe pattern.
  • the stripe pattern makes it possible to control the exposure time or duration on the basis of a predetermined potential difference between light and dark areas, which is considered to be more favorable than the exposure time control by reaching a fixed residual charge potential of the surface of the printing plate, since the light-sensitive layers of the printing plates are in the dark areas , ie the unexposed areas, generally show a non-uniform behavior.
  • FIG. 3 schematically shows the change in the surface potential of a bright area of a charged printing plate as a function of the exposure time.
  • the potential is measured with a fixed potential detector.
  • First the printing plate is charged to the surface potential U a and the exposure is started at the switch-on time t E.
  • the bright area in the latent electrostatic charge image is discharged during the exposure according to the curve shown, the surface potential decreasing exponentially.
  • the respective continuously measured surface potential is continuously compared with a predetermined nominal value of the surface potential U R of the residual charge of the photoconductive layer of the printing plate, and as soon as the measured surface potential matches the predetermined surface potential U R , that is at time t A , the exposure is switched off Exposure source ended.
  • FIG. 4 schematically shows bright discharge curves U E1 , U E2 , U E3 , ... and the dark discharge curve U S of an electrostatic charge image as a function of the exposure time, these measurements with a potential moving along the printing plate detector.
  • Several discharge curves of the light areas for differently high charges of the printing plate are shown.
  • no discharge of the dark areas should occur, so that the potential U D of the dark areas should lie on a straight line parallel to the time axis through the surface potential U o of the charge.
  • the potential detector 3 is moved over the stripe pattern and the distribution of the surface potentials is measured, which roughly have the theoretical course shown in dashed lines in FIG. 5. The practical course approximated to this course is shown with continuous lines.
  • the associated course of the surface potentials in the individual light and dark areas during the exposure is entered above the stripe pattern.
  • the printing plate is charged to a surface potential U o and the discharge begins with the exposure in the first bright area of the printing plate.
  • the surface potential increases from U E1 to U S1 .
  • the surface potential within the range 9 1 decreases only slightly to a value U S2.
  • a strong lowering of the surface potential to U E3 is made to rise at the beginning of the subsequent second dark portion 9 II U S3 and S4 slightly drop to U at the end of the dark area.
  • the surface potential drops to U E5 to then climb back up to U S5 in the dark area that follows. This course continues in an analogous manner through the remaining light and dark areas.
  • the residual charge potential U R of the last measured bright area before the end of the exposure provides the basis for determining the counter voltage for the developing electrode, while the charge potential U o is used for determining the required charging voltage for the next printing plate.
  • the discharge or the course of the surface potentials in the stripe pattern follows the course of the surface potentials in the electrostatically latent charge image, so that the measurement of the potential difference in the stripe pattern representative of the direct measurement of the potential difference in the latent electrostatic charge image can be made without the electrostatic latent charge image being influenced by the imaging of the potential detector during the measurement process.
  • the setpoint value ⁇ U ideal is primarily dependent on the respective toner, whether liquid or dry toner, the constancy of its triboelectric charging and the concreting or development process, and secondly on the printing plate type.
  • the speed of the concreting plays a crucial role in the concreting process.
  • the absolute value of the potential difference ⁇ U is ideally 330 V ⁇ 100 V for dry toner development and 230 V ⁇ + 100 V for liquid toner development, for example.
  • the potential difference ⁇ U ideal for optimal contrast between the light and dark areas after development is determined in advance for the parameters toner, development and printing plate and can be called up and stored.
  • FIG. 6 shows a basic block diagram of an arrangement for exposure control based on the measurement of the residual charge potential of exposed printing plates.
  • the potential detector 3 the operation of which will be described later, supplies an AC voltage signal as an output signal, which is fed to a signal converter 11 and is converted therein into a DC voltage signal.
  • This DC voltage signal is fed to an impedance converter, which ensures that the DC voltage signal is passed with a low impedance to the one input of a comparator 13, the other input of which is supplied with an adjustable comparison voltage, which is supplied by a device 15, such as a memory or a ten-turn potentiometer, and which equal the desired residual charge potential of the exposed printing plate is applied.
  • a device 15 such as a memory or a ten-turn potentiometer
  • the switching threshold of the comparator 13 can be freely selected and the actual charge after a certain exposure time is compared in the comparator with the desired value corresponding to the desired residual charge potential at the time of the end of the exposure. As long as the surface potential of the actual charge is greater than the target value as an absolute value, the exposure is continued. As soon as the measured surface potential is equal to or less than the target value, the comparator 13 outputs an output signal to a shutter 14 in the exposure path, which is closed and thus ends the exposure of the printing plate.
  • the impedance converter 12, the comparator 13 and the setpoint adjustment device 15 form a control device 51, which is shown in broken lines.
  • the shutter 14 is the camera shutter. Instead of the shutter 14, a relay can also be actuated, which interrupts, for example, the supply voltage to an exposure source. After completion of the exposure, the printing plate is transported to a developer device, not shown, in which it is concrete.
  • a microprocessor control can be used, which then controls the impedance converter 12 Comparator 13 and the memory 15 replaced.
  • the output signal of the signal converter 11 is then fed directly to the microprocessor, which supplies a digital signal via the digital output to the shutter 14 or to a switching transistor for actuating a relay, which interrupts, for example, the supply voltage to an exposure source.
  • FIG. 7 shows a block diagram of an arrangement which can also be used for exposure, corona and developing electrode control on the basis of the measurement of the potential difference between light and dark areas of an exposed printing plate.
  • the surface potential measured by the potential detector 3 produces an AC voltage output signal which is fed to a signal converter 16 which converts the AC voltage signal into a DC voltage signal.
  • the sign of the direct voltage depends on the phase position of the alternating voltage signal in the initial position of the measuring electrode of the potential detector. If the starting position of the measuring electrode is such that a maximum is passed through, ie the phase is positive, a positive DC voltage signal is generated in the signal converter.
  • a negative DC voltage signal is generated in the signal converter 16.
  • the output signal of the signal converter 16 is fed to a control device 52, shown in broken lines, which is an amplifier 17 and an analog-digital converter 18, which is combined with a microprocessor 19, a digital output 20 and a digital / analog converter 21 to form a unit.
  • the control of the microprocessor 19 is programmed in such a way that the measurement signal supplied by the potential detector 3, which corresponds to the potential difference between the dark discharge potential and the light discharge potential, is compared with a stored target value and, if the two values match, on the one hand the digital output 20 sends a signal to the closure 14 supplies, in order to close the latter and end the exposure, and on the other hand, the digital / analog converter 21 generates two output signals which are fed to a corona supply 24 and a developing electrode supply 25, respectively, in high-voltage amplifiers 22 and 23.
  • FIGS. 8 and 9 show the flow diagrams for the circuit arrangements according to FIGS. 6 and 7, it being assumed that both circuit arrangements are equipped with a microprocessor.
  • the surface potential U a of the charged printing plate measured by the potential detector is stored in the memory with variable access by the microprocessor and the associated residual charge potential U R is determined. Associated pairs of charge potentials U o and residual charge potentials U R are stored in tabular form in the microprocessor.
  • the surface potential U measured by the potential detector is included compared to the residual charge potential U R. This comparison is continued as long as the potential U is greater than the residual charge potential U R. As soon as the measured potential U is less than or equal to the residual charge potential U R , the exposure is switched off.
  • the charging potential U 0 is compared with a predetermined reference value U 0ideal and in the microprocessor at a combination of the two values in such a way that U a U 0ideal is greater than controlled charging corona so that the corona voltage U corona decreased by one step becomes.
  • U a U 0ideal is greater than controlled charging corona so that the corona voltage U corona decreased by one step becomes.
  • the flowchart shown in FIG. 9 is to be read in connection with the circuit arrangement according to FIG. 7 and relates to the microprocess control of a circuit arrangement with a moving potential detector.
  • the exposure and the drive for the potential detector are switched on and the charging potential U o is stored in the memory with variable access by the microprocessor.
  • the surface potentials measured by the potential detector along the dark discharge curve U S and the associated surface potentials of the light discharge curve U E are continuously read into the variable access memory.
  • Ge g ens p a n g U now Ge g ens p Annun g results from U R U + x, with the remaining charge potential U R of the printing plate at Completion of exposure and U x , an empirical value in the range of 10 to 120 V, which is added to the residual charge potential to ensure that a background-free image is obtained during toner development.
  • Last is performed the output of the counter voltage U Ge g ens p Annun g and the corona voltage U corona for controlling the development electrode and the Aufladekorona.
  • the printing plate and the measuring arrangement are also illuminated with a light intensity which corresponds to the background density under the most unfavorable conditions, such as are present, for example, in the shadow region of a cut edge of a part of a sentence.
  • a gray field of appropriate density in opaque or transparent form can be attached to or above the template edge or the head of the potential detector can be covered with a gray filter of the desired density.
  • the density of the gray field is in the range of 0.05-0.5, in particular at a value of 0.26.
  • the counter-voltage of the developing electrode is then placed at the same voltage level as the residual potential of the printing plate in the exposed area measured by the potential detector or illuminated by the image of the gray field of the printing plate, the images of all image areas are shown up to this optical density not stressed.
  • the lower on is also an advantage flow of various sources of error, such as the zero point drift and the detection of shadow potentials of the measuring probe, on the measurement result.
  • the potential detector 3 known per se is closed by a metal housing 35 with an opening 36 which surrounds the measuring device and shields it from external electrical fields.
  • the opening 36 forms a measuring opening for the measuring electrode 6.
  • a tuning or vibrating fork 31 in the metal housing is set in mechanical vibrations by an oscillator 28 via a frequency-adjustable drive 32, as indicated by the two double arrows B, B, and is electrically connected to connected to the metal housing 35.
  • the arms of the tuning fork 31 swinging towards and away from each other work as a chopper which periodically opens and closes the measuring window 6.
  • the electric lines of force emanating from the surface potential of the latent electrostatic charge image on the printing plate run through the measuring opening onto the measuring electrode 6 and are interrupted by the reciprocating arms of the tuning fork 31 which move transversely to the lines of force.
  • a chopped alternating voltage is induced in the measuring electrode 6, the amplitude of the voltage difference between the surface potential on the printing plate and the potential of the tuning fork is proportional, which is electrically connected to the metal housing 35.
  • the phase of the induced alternating voltage is determined by the polarity of the direct voltage, which is applied to the measuring electrode 6 or to the metal housing 35 of the potential detector 3.
  • the high-impedance AC voltage signal induced in the measuring electrode 6 is converted into a DC voltage signal in the signal converter 11, which is shown in broken lines in FIG. 10.
  • the induced AC voltage signal of high impedance is converted by an impedance preamplifier 26 into a signal of low impedance and fed to a signal amplifier 27, the output signal of which is fed to a phase detector 30 via an opto or photocoupler consisting of a light-emitting diode 29 and a phototransistor 37.
  • the amplitude and polarity of the DC voltage output signal of the phase detector 30 are predetermined by the amplitude and phase of the induced AC voltage signal relative to the reference signal which is applied to the measuring electrode 6.
  • a signal of the oscillator 28 is fed to the phase detector 30 via an optocoupler or photocoupler, consisting of a phototransistor 39 and a light-emitting diode 38, in contrast to which the starting position of the measuring electrode 6 is determined. If the tuning fork 31 opens the window between the measuring electrode and the pressure plate, the phase and the DC voltage output signal are positive, otherwise the phase and the DC voltage output signal negative.
  • the DC voltage output signal of the phase detector 30 is integrated by an integrator 33 for low DC voltages. The polarity of the output signal of the integrator 33 is inverted to the polarity of the surface potential of the printing plate to be measured.
  • the output signal of the integrator 33 is displayed on the one hand via a voltmeter V and on the other hand fed to a high-voltage amplifier 34.
  • the output signal of the high-voltage amplifier 34 is fed back to the metal housing 35 of the potential detector 3 in order to bring it to the same potential as that of the plate surface to be measured and is, on the other hand, supplied via a voltage divider 40, which comprises a variable resistor and two fixed resistors, to the impedance converter 12 of the control circuit for determining the residual charge potential when the exposure of the printing plate has ended.
  • the impedance of the DC voltage measurement signal is reduced.
  • the output of the impedance converter 12 is connected to the one input of a comparator 13, the other input of which is connected to a ten-turn potentiometer 41 for setting and feeding in the desired setpoint of the residual charge potential.
  • a reference voltage of a light-emitting diode 42 is applied to the ten-turn potentiometer 41, which together with a resistor 43 forms a voltage divider.
  • the light emitting diode 42 also serves to indicate whether a voltage is applied to the ten-turn potentiometer 41 or not.
  • a filter capacitor 44 which filters out any AC voltage signal components that may still be present in the DC voltage measurement signal.
  • the output of the comparator 13 is fed back to the input at which the target value of the residual charge potential is present.
  • the setpoint signal is inverted compared to the measurement signal.
  • a digital voltmeter 45 measures, depending on the position of a push button 46a, 46b, the measurement signal at one input or the setpoint signal at the other input of the comparator 13. If the measurement signal and the setpoint signal match, the comparator 13 supplies an output signal which a switching transistor 47 for actuates a switching source 48, which switches a switch 49, whereby, for example, the shutter 14 in the arrangement according to FIG. 6 is closed and the exposure is ended.
  • a light emitting diode 5C is connected to the switch as a display.
  • a microprocessor control can be provided instead of the control circuit consisting of impedance converter ⁇ r 12, comparator 13, setpoint value setting device 15.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Control Of Exposure In Printing And Copying (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Combination Of More Than One Step In Electrophotography (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
EP85102575A 1984-03-16 1985-03-07 Méthode et dispositif pour obtenir une valeur prédéterminée de potentiel lors de l'illumination de couches photo-conductrices chargées électrostatiquement Expired EP0156217B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85102575T ATE39773T1 (de) 1984-03-16 1985-03-07 Verfahren und anordnung zum einhalten eines vorgegebenen potentialverhaeltnisses bei der belichtung von elektrostatisch aufgeladenen lichtempfindlichen schichten.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19843409701 DE3409701A1 (de) 1984-03-16 1984-03-16 Verfahren und anordnung zum einhalten eines vorgegebenen potentialverhaeltnisses bei der belichtung von elektrostatisch aufgeladenen lichtempfindlichen schichten
DE3409701 1984-03-16

Publications (2)

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EP0156217A1 true EP0156217A1 (fr) 1985-10-02
EP0156217B1 EP0156217B1 (fr) 1989-01-04

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EP85102575A Expired EP0156217B1 (fr) 1984-03-16 1985-03-07 Méthode et dispositif pour obtenir une valeur prédéterminée de potentiel lors de l'illumination de couches photo-conductrices chargées électrostatiquement

Country Status (8)

Country Link
US (1) US4616923A (fr)
EP (1) EP0156217B1 (fr)
JP (1) JP2717101B2 (fr)
AT (1) ATE39773T1 (fr)
AU (1) AU570307B2 (fr)
CA (1) CA1228114A (fr)
DE (2) DE3409701A1 (fr)
ES (1) ES8607577A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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US5241276A (en) * 1989-04-28 1993-08-31 Kabushiki Kaisha Toshiba Surface potential measuring system

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US4970557A (en) * 1987-09-02 1990-11-13 Sharp Kabushiki Kaisha Electrophotographic apparatus controlling image quality according to condition of deterioration
JP2954593B2 (ja) * 1987-12-14 1999-09-27 株式会社リコー 画像形成装置の作像制御方法
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JP3019355B2 (ja) * 1990-03-19 2000-03-13 ミノルタ株式会社 画像形成装置
JP3362068B2 (ja) * 1993-04-28 2003-01-07 株式会社リコー 画像形成プロセスにおける電位形成条件制御方法
US7225301B2 (en) 2002-11-22 2007-05-29 Quicksilver Technologies External memory controller node

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EP0395447A3 (fr) * 1989-04-28 1991-05-22 Kabushiki Kaisha Toshiba Système de mesure du potential superficiel
US5151659A (en) * 1989-04-28 1992-09-29 Kabushiki Kaisha Toshiba Surface potential measuring system
US5241276A (en) * 1989-04-28 1993-08-31 Kabushiki Kaisha Toshiba Surface potential measuring system

Also Published As

Publication number Publication date
US4616923A (en) 1986-10-14
EP0156217B1 (fr) 1989-01-04
AU4008085A (en) 1985-09-19
ES541193A0 (es) 1986-06-01
DE3567295D1 (en) 1989-02-09
ATE39773T1 (de) 1989-01-15
JP2717101B2 (ja) 1998-02-18
CA1228114A (fr) 1987-10-13
ES8607577A1 (es) 1986-06-01
AU570307B2 (en) 1988-03-10
DE3409701A1 (de) 1985-09-19
JPS60213964A (ja) 1985-10-26

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