EP2100193B1 - Method and device for processing a measurement signal for detecting a property of a toner mark - Google Patents

Abstract

In a method or system for processing a measurement signal for detecting a property of a toner mark, the toner mark is produced and detected. A measurement signal is output, a signal curve of the measurement signal being determined. A temporal measurement window is provided for detecting a property of the toner mark, the temporal measurement window having a beginning and an end. A plausibility check is carried out of the determined signal curve wherein a maximum value and a minimum value of the signal curve are determined, a first difference value between a maximum value and the minimum value is determined, a first temporal distance is determined between an occurrence of the maximum value and an occurrence of the minimum value, a second temporal distance is determined between at least one of the beginning and end of the measurement window and the occurrence of at least one of the maximum value and the minimum value, and a second difference value is determined between a first distance of the maximum value from a reference value and a second distance of the minimum value from the reference value, and the second determined difference value is compared to at least one of a defined minimum difference value and a defined maximum difference value.

Description

The invention relates to a method and a device for processing a measurement signal for detecting a property of a toner mark, in which a signal course of a measurement signal is determined.

In the case of electrographic high-performance printers for printing single sheets or web-shaped carrier material with printing powers of> 50 sheets DIN A4 / minute up to several 100 sheets DIN A4 / minute as well as printing and imaging speeds of currently up to 2 m / sec, large quantities of toner material can be produced within a relatively short time consumed to produce the print images. Dyeing controls are used in such high-performance electrographic printers to keep the inking level of printed images constant. Electrographic imaging techniques include, for example, electrographic, magnetographic and ionographic imaging techniques.

From the document DE 101 36 259 A1 and the parallel one U.S. Patent 7,016,620 B2 For example, a method and a device for controlling a printing process are known in which a toner mark is generated on a subcarrier by a character generator with a lower energy than the energy used to produce other print images, so that the color density of the inked toner mark is reduced. A reflection sensor determines the color density of the colored toner mark, depending on the determined color density, the toner concentration is set in a developer station.

Further, from the document DE 101 51 703 A1 and the parallel one U.S. Patent 6,771,913 B2 Measuring arrangements for determining the layer thickness of a toner mark using capacitive sensors known. The cited documents are hereby incorporated by reference into the present specification.

Incorrect detection, in particular a false reading, of a property of the toner mark used to control the electrographic imaging process would directly result in incorrect settings of parameters of the imaging process and, in particular, cause incorrect coloration of the printed image to be generated. Such a false detection of the property of the toner mark can be caused in particular by disturbances, damages or soiling of an intermediate image carrier, in particular a photoconductor or a transfer belt.

From the documents JP 2004-341232 A . US 2004/0253013 A . US 5,574,544 A . US 2003/0081214 A . US 5,481,337 A and US 2003/231350 A In each case arrangements and methods for detecting a toner mark are known, with the aid of an image forming process is controlled. In particular disclosed JP 2004-341232 A A method according to the preamble of claim 1 and an apparatus according to the preamble of claim 7.

The object of the invention is to provide a method and a device for processing a measurement signal for detecting a property of a toner mark, by which it is ensured that at least not heavily falsified Measurement signals are used to control or regulate the imaging process.

This object is solved by the subject matters of the independent claims. Advantageous developments of the invention are specified in the dependent claims.

By a method for processing a measurement signal for detecting a property of a toner mark having the features of patent claim 1, a plausibility check of the determined signal course of the measurement signal is carried out. It can thereby be determined whether the measurement signal generated by the toner mark sensor has a characteristic characteristic of the toner mark generated. An evaluation unit of the toner mark sensor can, on the basis of a maximum-minimum analysis, generate a control signal which can be used for a coloring control of the image-forming process. By carrying out the plausibility check, it is possible in a simple manner to avoid the fact that greatly deviating measurement results from the actual measurement result are used to control the image generation process, which could impair the print quality and permanently damage components involved in the image generation process. This is possible, for example, by conveying too much toner into a developer station, as a result of which the two-component mixture of toner particles and carrier particles present there can be permanently damaged by the toner which is much too much replenished, whereby, in particular, a triboelectric charging of the toner particles can no longer be carried out sufficiently.

Measured values, measurement waveforms, and measurement results that do not pass the plausibility check are ignored and not used for the imaging process. If the plausibility check is not passed by the ascertained signal curves of a plurality of consecutively generated toner marks, then a warning or an error message can be output in a suitable manner, for example via a control panel of a printing or copying system, in which the method for processing a measurement signal for detecting a property of a toner mark having the features of patent claim 1 is used.

By a plausibility check of the sensor signal output directly from a sensor for detecting the property of the toner mark and / or its signal curve, erroneous measured values can be detected quickly and directly without these having already been changed or adapted by further processing. Such a plausibility check can determine both mechanical damage and contamination of an image carrier in the region in which the toner mark is produced. This area is also called a trademark track. The impurities may be caused by adhering toner on the image carrier, which has not previously been removed by a cleaning unit from the image carrier.

According to the invention, a maximum value and a minimum value of the signal profile are determined. These extreme values (maximum value, minimum value) are preferably determined in a measuring window, by which a period is defined in which the toner mark to be analyzed is detected by a measuring arrangement, in particular a capacitive toner mark sensor. Furthermore, a difference value between the maximum value and the minimum value is determined and output for further processing. The plausibility check then checks the plausibility of the maximum value, the minimum value and / or the difference value. In particular, the layer thickness of a toner layer supplied to a capacitive sensor can be determined in a simple manner with the aid of the difference value. Also, for example, the average Dyeing of a not completely over-colored with toner particles toner mark can be determined, which can then be closed at a known layer thickness of the colored areas on the colored area. This colored surface can be used as the actual value for a point size or line width control. The measuring signal is preferably sampled with the aid of a sensor arrangement. In this case, the signal profile can be generated from a plurality of successively determined sampling values of the measurement signal output by the sensor arrangement.

With the aid of the plausibility check, it can be checked whether the determined measured value profile, the ascertained maximum value, the determined minimum value and / or the difference value are characteristic of the toner mark produced. In particular, the time interval between the occurrence of the maximum value and the occurrence of the minimum value as a criterion can be determined for the plausibility check. Furthermore, the time interval between a measurement window size of the time measurement window for detecting the property of the toner mark and the occurrence of the maximum value and / or the minimum value is determined as criterion or as criteria for the plausibility check. Furthermore, for the plausibility check, an asymmetry between the distance of the maximum value and a reference value and the distance of the minimum value and the reference value determined as a criterion. Furthermore, it is possible to compare the difference value to a plausibility check with a minimum difference value and / or with a maximum difference value and to use it as a criterion. For the plausibility check one of the mentioned criteria, two of the mentioned criteria, three of the mentioned Criteria, four of the above criteria, or all five of the above, as well as alternatively or additionally

As a result, a comprehensive plausibility check of the signal curve of a measurement signal output by a sensor is possible. In particular, the measurement signal can be determined with the aid of a capacitive sensor which has two plate capacitors arranged one behind the other in the transport direction of the image carrier carrying the toner mark, the capacitors being charged with charging voltages opposite to a reference potential for charging the capacitors. The capacitors are short-circuited after the charging process, whereby a charge difference is generated. This charge difference is a measure of the capacitance difference of the two capacitors due to the positioning of the toner mark in the air gap of at least one capacitor. With the aid of such a capacitive sensor, the layer thickness, the amount of toner and / or the area coverage of a toner mark can be reliably determined in a simple manner.

It is particularly advantageous if at least two plausibility checks of the signal profile are carried out with two mutually different plausibility criteria. Each plausibility check is assigned an error counter. Such an error counter is incremented if the plausibility criterion assigned to this error counter has not been complied with. The error is decremented if the plausibility criterion has been adhered to. The incrementing is preferably done by a higher count than the decrementing. This can be a simple way an error signal, in particular an error message, output if at least one error counter exceeds a preset limit. Alternatively or in addition to the error message, a background adjustment of the image carrier can be carried out. As a result, errors due to contamination and damage to the image carrier can be at least partially ignored.

Preferably, the signal profiles of the measurement signals of a plurality of successively generated toner marks are detected. With the help of the acquired signal waveforms, a corrected waveform is generated. The signal curve is corrected, for example, by means of averaging or median value formation. The plausibility check is then performed for the corrected waveform of the measurement signal.

A second aspect of the invention relates to a device for determining a measurement signal for detecting a property of a toner mark according to claim 7. The device has a sensor for detecting the signal curve of a measurement signal. Furthermore, the device comprises a control unit which carries out a plausibility check of the signal profile determined with the aid of the sensor.

By means of such a device it can be ensured that strongly deviating measured values or a waveform deviating greatly from the usual signal profile or a signal course deviating from a possible signal course of the measuring signal when detecting a particular toner mark can be determined, in which case this signal characteristic is used to control or regulate the Image forming process is not further used.

Figur 1a

eine schematische Darstellung des Aufbaus einer Vorrichtung zum Bestimmen der Flächendeckung einer Tonermarke;

Figur 1b

ein Spannungs-Zeit-Diagramm mit dem prinzipiellen Verlauf eines von der Vorrichtung nach Figur 1a beim Durchführen einer Tonermarke erzeugten Messsignals;

Figur 2

ein Diagramm mit dem Signalverlauf des Sensorsignals über 1000 Abtastpunkte einer mit einem ersten Druckwerk erzeugten Tonermarke;

Figur 3

die jeweils abgetasteten Signalverläufe des Sensorsignals bei einer Vielzahl nacheinander mit einem zweiten Druckwerk erzeugter Tonermarken;

Figur 4

einen ersten Ablaufplan zum Überprüfen eines ersten Plausibilitätskriteriums;

Figur 5

einen Ablaufplan zum Überprüfen eines zweiten Plausibilitätskriteriums; und

Figur 6

einen Ablaufplan zum Ermitteln eines dritten Plausibilitätskriteriums.

For a better understanding of the present invention, reference will now be made to the preferred embodiments illustrated in the drawings, which are described in terms of specific terminology. It should be understood, however, that the scope of the invention, which is defined by the appended claims, is not to be limited thereby, as such changes and further modifications to the illustrated devices and / or methods, as well as such other uses of the invention, such as they are indicated therein as being common current or future expertise of a skilled artisan. The figures show embodiments of the invention, namely:

FIG. 1a

a schematic representation of the structure of an apparatus for determining the area coverage of a toner mark;

FIG. 1b

a voltage-time diagram with the basic course of a device according to FIG. 1a when performing a toner mark generated measurement signal;

FIG. 2

a diagram showing the waveform of the sensor signal over 1000 sampling points of a toner mark produced by a first printing unit;

FIG. 3

the respectively sampled signal waveforms of the sensor signal at a plurality of toner marks successively generated with a second printing unit;

FIG. 4

a first flow chart for checking a first plausibility criterion;

FIG. 5

a flow chart for checking a second plausibility criterion; and

FIG. 6

a flowchart for determining a third plausibility criterion.

In FIG. 1a For example, a measuring device 10 for detecting a toner mark 39 formed as a toner particle layer 38 by means of an electrographic image forming process is shown. This measuring arrangement 10 is used in an electrographic printer or copier to detect the coloring of the printed image and / or the dot size of dot dots colored with toner particles. With the aid of the measuring arrangement 10, the mean layer thickness of a toner mark 39 present in the detection area of this measuring arrangement 10 is detected.

The toner mark 39 has a homogeneous printed image with a uniform inking pattern with a full-surface coloring or with a non-full coloration. The toner layer 38 of the toner mark 39 has been formed on a photoconductor belt 16 charged by a charger such as a corotron by means of a character generator such as an LED character generator or a laser character generator as a latent image in the form of a charge image. This latent raster image has subsequently been developed by means of a developer unit (not shown), provided by the developer unit Toner particles have been used for coloring the latent raster image.

Developing the latent image with toner particles is preferably carried out by means of so-called tribo-jump development, in which the electrically charged toner particles provided by the developer unit are applied by the developer unit to the force applied thereto in the direction of the areas of the latent image to be inked by an electric field be transferred to these areas to be colored. The voltage required to generate the electric field is also referred to as bias voltage. It is particularly advantageous if a layer of toner particles having a substantially constant layer thickness is provided by the developer station, which is then transferred by the bias voltage only to the areas to be inked.

Between the non-inking areas of the latent image and the developer station is generated by the bias voltage another electric field which exerts a force on the toner particles in the direction of the developer station, so that no toner particles from the developer station to non-inked areas of the photoconductor belt 16th be transmitted. In the document " Digital Printing - Technology and Printing Technics on Océ Digital Printing Presses ", 9th Edition, February 2005; ISBN 3-00-001081-5, is at page 222 in Figure 8.22 exemplified a scheme of a Tribo Jump developer station shown and briefly described.

The photoconductor belt 16 is a circulating endless belt which is guided by means of deflection rollers (not shown) is. The photoconductor belt 16 contains electrically conductive components, which are electrically conductively connected to a reference potential 18. On the lateral surface 40 of the photoconductor belt 16, the toner layer 38 of the generated toner marks 39 and toner layers of printed images are arranged. Parallel to the lateral surface 40, a first electrode 12 and a second electrode 14 are arranged, which are formed in the embodiment as a plate-shaped electrodes 12, 14. The effective areas of the electrodes 12, 14 and the photoconductive belt 16 serving as the counterelectrode face each other, and the first and second electrodes 12 and 14 preferably have the same effective area. The photoconductor belt 16 is thus connected to the reference potential 18 counter electrode to the electrodes 12, 14. The first electrode 12 and the counter electrode form a first capacitor 13 and the second electrode 14 and the counter electrode form a second capacitor 15. With the same effective area of Electrodes 12, 14 and an equal distance of the electrodes 12, 14 to the counter electrode, the first capacitor 13 and the second capacitor 15 have the same capacity when between the photoconductor belt 16 no toner layer 38 and no toner residues or the same amount of toner are present. The distance between the photoconductor belt 16 and the electrodes 14, 16 is preset to a value in the range of 0.2 mm and 10 mm. Preferably, this distance is about 1 mm.

A switching unit 26 is provided in order to connect the electrode 12 with a positive voltage source 42 to the reference potential 18 and the electrode 14 with a negative voltage source 44 to the reference potential 18 by means of switches 46, 48 in a first switching state. The amounts of the voltages provided by the voltage sources are preferably the same. For example, the positive voltage output by the voltage source 42, for example +10 V, and negative voltage output by the voltage source 44, for example -10 V, with respect to the reference potential 18, for example 0 V.

In a second switching state, the switching unit 26 disconnects the connections to the voltage sources 42, 44 with the aid of the switches 46, 48, short-circuits the two electrodes 12, 14 and thereby establishes a connection to the evaluation unit 24. Thus, the charge difference of the capacitors 13, 15 is determined and fed to the evaluation unit 24. By switching to the second switching state, a sampling of a measured value generated by the charge difference takes place. The switching unit 26 is a clock signal 34 of a clock 32 is supplied, which is preferably a square wave signal with a constant duty cycle ratio. The clock frequency of the clock signal 34 and thus the switching frequency of the switching unit 26 for switching the two switching states or the switches 46, 48 is preferably in the range between 300 Hz and 1 MHz.

The clock 32 is in particular part of the control unit for evaluating the sensor signal output by the measuring arrangement 10, wherein the clock signal 34 in the switching unit causes a change in the switching state of the switches 46, 48. The switching of the capacitors due to the switching states is also referred to as a switched capacitor technique. Further details on the structure and further embodiments of the measuring arrangement 10 are from the document DE 101 51 703 A1 as well as the parallel US patent 6,771,913 B2 The contents of which are hereby incorporated by reference into the present description.

The evaluation unit 24 may have, for example, a filter and a downstream amplifier. A measurement signal generated by the evaluation unit 24 is supplied to a control unit (not shown) for further processing. If, as already mentioned, a filter is used in the evaluation unit 24 for evaluation, then the filter type and the required filter parameters of the filter can be preset as a function of the switching frequency and the sampling frequency resulting therefrom.

If the toner particle layer 38 of the toner mark 39 is transported through the air gaps of the electrodes 12, 16 and 14, 16 on the photoconductor belt 16 in the direction of the arrow P1, then the capacitance difference of the two capacitors 13 will be in the second operating state at each sampling instant or at each switchover instant , 15 determined. The capacitances of the capacitors 13, 15, which have no toner markers in the detection region of the measuring arrangement 10, change when toner particles are present in the region between the respective electrodes 12, 14 and the counterelectrode, since the toner particles have a different dielectric constant than that between the electrodes 12/16 , 14/16 otherwise only available air.

From the change in the capacitance of at least one of the capacitors 13, 15, the layer thickness of the toner particle layer can be determined, which would be present with a uniform distribution of the present in each capacitor 13, 15 toner particles on the effective area of the respective capacitor 13, 15. Thus, the middle Layer thickness determined in the detection range of the respective capacitor 13, 15 toner particles determined as a toner mark 39, which covers half the effective area of a capacitor 13, 15 and has a first layer thickness can not be distinguished from a second toner mark 39, the total effective area of the capacitor 13, 15 covered and half the layer thickness of the first layer thickness.

On the basis of the capacity curve, however, the exact layer thickness profile of a toner mark in the transport direction of the photoconductor belt 16 can be determined in accordance with elaborate evaluation and a sufficient number of samples based on the transport speed for transporting the photoconductor belt 16 in the direction of the arrow P1.

The capacitance change of the capacitors 13, 15 due to the toner particles of the toner layer 38 present on the photoconductor belt 16 in the region of the capacitors 13, 15 results from the change of the dielectric, i. from the change of the layered dielectric of the respective capacitor 13, 15 during the transport of the toner layer 38 between the respective electrode 12, 14 and the counterelectrode of the respective capacitor 13, 15.

The charge difference generated by the short circuit of the electrodes 12, 14 in the second switching state as a function of the capacitances of the capacitors 13, 15 at the sampling time is further processed with the aid of the evaluation circuit 24 and is preferably supplied to the control unit. The control unit according to the invention can also cover the area of the respective toner mark 39 at a known layer thickness determine if the print image of the respective toner mark 39 is not completely colored with toner particles. Particularly with toner marks 39 having a plurality of strip-shaped or line-shaped regions of a printed image colored with toner particles, the area colored with toner particles and / or the surface of toner mark 39 not colored with toner particles can be in the range with the aid of a capacitor 13, 15 of the respective capacitor 13, 15 are determined or determined. For toner swatches that have been inked all over with toner particles, the layer thickness of the toner particle layer and, thereby, the optical density of the toner swatch can be determined or determined. In the same way, the inked area of the toner mark 39 can be determined if the toner mark 39 additionally or alternatively has punctiform colored areas. These punctiform colored areas can comprise individual pixels as well as areas composed of several pixels, so-called super pixels.

It is advantageous to supply the arrangement 10 with a toner mark which has been dyed over the entire surface and a toner mark which is not completely colored in any order, the areas of which are to be inked being dyed in each case with the same layer thickness, whereby the ratio of the toner quantity of the toner mark not inked in the entire surface as a function of the toner quantity of the entire surface Toner brand can be determined. As a result, the relative coloration or the percentage area of the partially colored toner mark can be determined with respect to the full-color inked toner mark.

In FIG. 1b a time-voltage diagram is shown, in which the basic waveform of the measuring device according to FIG. 1a output measured signal is shown. For simplicity, the time-voltage diagram is after FIG. 1b a continuous waveform is shown. However, the actual waveform is composed of a plurality of samples. The sampling rate for determining these samples is determined by the clock signal 34 output by the clock 32. The waveform is sampled by the evaluation device 24 as the toner mark 39 passes through the capacitors 13, 15 as the photoconductor belt 16 travels at a constant speed, for example in the range of 0.2 to 2 m / s between the electrodes 12, 14 and the photoconductor belt 16 is passed through the capacitors 13, 15.

The dielectric constant of toner is greater than the dielectric constant of air. Thereby, the capacitance of the capacitors 13, 15 in passing the toner mark 39 through these capacitors 13, 15 is changed. With the aid of the photoconductor belt 16, the toner layer 38 of the toner mark 39 is transported into the first capacitor 13. Thereby, the capacity of the first capacitor 13 is increased. The capacitance of the first capacitor 13 increases until the toner layer 38 of the toner mark 39 covers the largest possible effective area of the first capacitor 13. This in FIG. 1b As a result, the signal represented increases with increasing capacitance of the first capacitor 13 from 0 V up to a maximum U +. Due to the continuous drive of the photoconductor belt 16, the toner layer 38 of the toner mark 39 is further transported into the second capacitor 15 and at the same time transported out of the first capacitor 13. Thereby increases the capacity of the second capacitor 15 to the same extent as the capacitance of the first capacitor 13 decreases. As a result, the negative increase in the output signal of the evaluation arrangement 24 is approximately twice as great as merely conveying out the toner layer 38 of the toner mark 39 from the first capacitor 13 or while conveying the toner layer 38 of the toner mark 39 into the second capacitor 15.

If the toner layer 38 has been completely transported out of the first capacitor 13 and this toner layer 38 covers the largest possible effective area of the second capacitor 15, then the evaluation arrangement 24 outputs a voltage signal U-. Subsequently, the toner layer 38 is conveyed out of the second capacitor 15, whereby the output from the evaluation device 24 voltage signal from value U to 0 continuously increases. This increase occurs until the time when the toner layer 38 has been transported out of the second capacitor 15.

For not completely colored toner brands, the z. B. have a plurality of strip-shaped juxtaposed colored areas, with the aid of the measuring arrangement 10, the average layer thickness of the toner mark 39 can be determined, which would be generated with a uniform distribution of the ink particle amount used for coloring the not solid inked toner image. With the aid of the measuring arrangement 10, a stepwise change in capacitance as a result of the inked and non-colored areas of a toner mark is possible, at least with considerable effort, if strip-shaped colored areas of the toner mark 39 are transverse to the transport direction P1 of the photoconductor belt are aligned. As an alternative or in addition, the toner mark which is not completely colored may comprise punctiform colored areas which consist of a pixel or in which a punctiform colored area comprises a plurality of pixels forming a so-called superpixel. The superpixel comprises, for example, 2 × 2, 2 × 3 or 4 × 4 pixels.

The average coloration of a toner mark or a measurement signal which corresponds to the mean layer thickness of a toner mark which is not inked in the entire area can be easily determined with the aid of the measuring arrangement 10. If, in addition, the layer thickness is known with which the toner image which has not been dyed over the entire surface is colored, the areal coverage of this toner mark, which is not inked in the entire area, can be determined in a simple manner on the basis of the determined average layer thickness of the toner mark which has not been completely colored.

The layer thickness can be determined in various ways, in particular measured. Preferably, a full-color inked toner mark with the aid of the arrangement FIG. 1a recorded, wherein the different change in the capacitances of the capacitors 13, 15 indicated by the full-color inked toner mark and by the not full-color inked toner mark the area coverage of the not fully colored toner mark. This is possible due to the fact that the colored areas of the full-area inked toner mark and the toner mark which is not completely colored have the same layer thickness of the toner particle layer used for inking.

In FIG. 2 is an actual waveform of the sensor signal of the measuring device after FIG. 1a represented over a part of a pressure side to be generated i and a second pressure side i + 1, which has been determined with the aid of a total of 1000 sampling points. On the photoconductor belt 16, a first toner mark, referred to as the discharge mark, and a second toner mark, referred to as the inking mark, are generated for each print page to be produced. The toner-colored marks are preferably produced in areas on the photoconductor belt 16 which is not transferred to a substrate to be printed, in particular not on individual sheets or a web-shaped recording medium. Alternatively, the toner marks may be generated and scanned in an operational state in which no further print images are generated.

With the help of related FIG. 1a described sampling of the sensor signal, a plurality of measuring points are sequentially detected, of which in FIG. 2 by way of example the signal values determined for the measuring points 100 to 1100 are shown. The maximum value and the minimum value of the signal change of the sensor signal caused by the inking mark of the side i are about 44 measuring points apart. Furthermore, the maximum and the minimum of the signal change caused by the discharge mark of the side i + 1 are about 74 measuring points apart. The maximum and the minimum of the signal pattern of the measuring arrangement brought about by the inking mark on the side i + 1 FIG. 1a There are about 45 measuring points apart. Due to the different distance of the maximum and minimum values of the signal curve caused by the inking marks and of the signal curve caused by the discharge marks, it can be determined in a simple manner whether it is the maximum and minimum value of a coloring mark or the maximum and minimum values of the unloading mark. Thus, confusion of these two toner brands can be easily avoided. Otherwise, such confusion would lead to the imaging process being affected on the basis of false readings. In particular, a color control or other control or regulation required for the imaging process could not be as desired based on the color swath trace but based on other values, such as the unload mark, and thus be erroneous.

Furthermore, a measuring point distance between the unloading mark and the inking mark is predetermined by the positioning of the unloading marks and inking marks relative to one another. In particular, so-called measurement windows can be easily defined in which the maximum value and the minimum value must occur in the overall signal course. In this case, only the waveform in the preset measurement window can be detected and / or analyzed and evaluated.

In FIG. 3 For example, the actual waveforms over approximately 260 measurement points of a plurality of successively generated and sampled inking marks are shown in a diagram. These waveforms are respectively in the in FIG. 3 time window has been detected. This in FIG. 3 shown measuring windows include FIG. 3 The areas 100, 102, 104. It is checked whether the respective waveform has occurred in a temporal region 102 at the beginning of the measurement window and / or in a region 104 at the end of the measurement window. Thus, the location of each toner mark within the measurement window is checked.

If, for example, the minimum value lies in the region 102 or the maximum value in the region 104, it is not ensured that the entire signal curve generated by the toner mark is present in the region 100 used for the evaluation. The measurement window composed of the areas 100, 102, 104 has a total size of approximately 260 measurement points which define the period of the measurement window. The signal profile directly influenced by the inking mark comprises about 150 measuring points. The signal curve influenced by a discharge mark comprises about 200 measuring points.

The distance between the maximum and minimum of the inking marks is about 45 measuring points and the distance from the maximum to the minimum of unloading marks is about 75 measuring points. Within a printing page with a side length of 12 inches, the distance from the maximum of the unloading mark to the maximum of the inking mark is about 300 measuring points and the distance between the maximum of the inking mark and the maximum of the unloading mark is about 560 measuring points.

It should be noted that the sequence of maximum and minimum in the signal curve may differ depending on the construction of the printing unit and the measuring arrangement. For the evaluation and plausibility check, therefore, two extreme values caused by the toner mark in the signal course of the measuring arrangement are decisive. Unlike the diagrams in the Figures 1b and 2 is in FIG. 3 the signal profile of another printing unit has been detected with the aid of the measuring arrangement 10, whereby upon delivery of the inking mark only a minimum is generated as an extreme value and then a maximum as an extreme value.

On the basis of the determined signal curve, it is checked whether a minimum or maximum caused by the toner mark is arranged in the region 102 in the signal course. Furthermore, it is checked whether a by the toner mark in the waveform caused minimum or maximum in the area 104 occurs. In addition, it is checked whether the difference between the maximum value and the minimum value comprises at least 500 measuring units. In the case of the only partially colored discharge marks, ie in the case of toner areas which are not completely colored, the minimum difference to be exceeded of 500 measuring units can also be chosen to be lower. It is also checked whether the extreme values (minimum, maximum) are symmetrical to a defined zero line. The tolerance for a deviating asymmetry is ± 75 measuring units. The distance between the two extreme values (minimum, maximum) is specified by the status variable "WrongMarkTriggered", whereby the distance may be a maximum of 60 measuring points and a minimum of 30 measuring points. The first extreme value (in FIG. 3 : Minimum) should be at least 60 measuring points after the beginning of the measuring window and thus not in the range 102. The second extreme value (in FIG. 3 : Maximum) should be at least 60 measurement points before the measurement window end, and thus not within the range 104. The presence of an extreme value in region 102 is indicated by the status variable "WndCutAtTheBeginning" and in region 104 by the status variable "WndCutAtTheEnd".

The minimum distance between two toner marks is at least 300 measuring points. Within a tint mark the maximum distance between minimum and maximum is 75 measuring points. As a result, theoretically, an extreme value of the preceding unloading mark could lie within the measuring window of the currently considered inking mark. By defining the measurement window and the other plausibility criteria, however, a check is made, whereby such a misinterpretation of signal waveforms is avoided. This ensures that the waveform of a single toner brand (inking mark or discharge mark) is actually viewed and evaluated, and then the extreme values belonging to a toner mark are used for further processing.

The inking mark is a toner mark for determining an actual value for a dyeing control, with which, in particular, the amount of toner to be replenished in the developer station is regulated in accordance with the coloration determined. This inking mark is preferably a full-color colored inking mark. Furthermore, a second full-color toner mark is produced as a discharge mark at a distance from the first toner mark. With the help of this unloading mark the discharge potential of toner dots to be inked halftone dots is controlled to a predetermined setpoint, with the aid of this discharge mark the discharge potential is set via the light energy emitted by the character generator to unload a halftone dot to be inked.

The toner particles for dyeing are preferably provided by means of an applicator element from the developer station as a toner particle layer having a preset, preferably controlled, layer thickness. An air gap is preferably provided between the toner particle layer and the lateral surface of the image carrier, the toner particles of the toner layer being transferred to the image carrier via this air gap with the aid of a so-called bias voltage. The applicator element is subjected to the bias voltage and generated on the basis of the potential difference to the discharge potential, an electric field that exerts a force on the toner particles provided from the developer station to the inked areas of an image carrier.

1. 1. Mindestdifferenz zwischen Maximum und Minimum (Mindestsignalhub)
2. 2. Die Differenz vom Maximum zu einem Bezugswert und vom Minimum zu dem Bezugswert (Symmetrie von Minimum und Maximum zum Bezugswert)
3. 3. Der zeitliche Abstand zwischen Maximum und Minimum
4. 4. Der zeitliche Abstand der Extremwerte zu den Messfensterrändern.

As a plausibility criteria for checking the sampled waveform are preferably:

1. 1. Minimum difference between maximum and minimum (minimum signal swing)
2. 2. The difference from the maximum to a reference value and from the minimum to the reference value (symmetry of minimum and maximum to reference value)
3. 3. The time interval between maximum and minimum
4. 4. The time interval of the extreme values to the measuring window edges.

The first criterion ensures that the signal has actually been caused by a toner mark. The second criterion ensures that the determined maximum value and minimum value is also the absolute maximum and the absolute minimum of the signal curve effected by the considered toner mark, since an asymmetry of the minimum value and the maximum value to a reference value may indicate extreme values of different toner brands. The third criterion is for distinguishing between inking marks and unloading marks, while the fourth criterion ensures that the entire toner mark under consideration lies within the measuring window. For this algorithm, a signal curve averaged over a plurality of identical toner marks (several discharge marks or a plurality of inking marks) should preferably be determined (for example, over 5 identical toner marks) in order to exclude the influence of coarse signal disturbances. Alternatively, a median value profile can be determined via the signal curves of several toner marks or a smoothed signal curve can be generated with the aid of a corresponding curve function (digital compensation curve).

In FIG. 4 2 is a flowchart for plausibility checking of the time interval between the two extreme values of a signal curve generated by a toner mark. The process is started in step S10. Subsequently, in step S12, the signal generated by the toner mark sensor is analyzed by the toner mark and the status variable "WrongMarkTriggered" is determined. The status variable indicates whether the minimum allowable distance between the two extreme values and / or the maximum allowable distance between the two extreme values has been adhered to or not. Subsequently, it is checked in step S14 whether the status variable "WrongMarkTriggered" indicates that the determined extreme values have too long or too short a time interval from one another. If this is the case, then in step S16, a previously determined measured value or a preset value is used as the further measured value, in which the currently determined measured value is replaced by the previously determined valid measured value or the preset value. Subsequently, an error counter is incremented by the value 3 in step S18.

If it is determined in step S14 that the status variable indicates that the time interval between the extreme values is within the permissible range, the count value of the error counter is reduced by the value 1 in step S20. Subsequently, or after the counter has been incremented by the value 3 in step S18, it is checked in step S22 whether the error counter is greater than or equal to the preset limit of 10. If this is not the case, the sequence in step S12 is continued by detecting the measured value profile of a further toner mark as well as its toner mark status.

However, if it is determined in step S22 that the permissible limit value of 10 is reached or exceeded, an error message is subsequently output in step S24 via a control panel of the printing or copying system. Subsequently, in step S26, a procedure for band background adjustment is started and then the error counter set to zero in step S26. Furthermore, the warning issued via the control panel is deactivated in step S30. Subsequently, the process in step S12 is continued for another toner mark.

In FIG. 5 is a flowchart for the plausibility check of the distance of the first extreme value (in FIG. 3 : Minimum) to the beginning of the measurement window. The process is started in step S40. In step S42, in the same manner as in step S12, after FIG. 5 the signal generated by the toner mark of the capacitive toner mark sensor is determined and analyzed, which has been generated by the toner mark. Based on the waveform, the status variable "MeasurementWndCutAtTheBeginning" is determined and optionally activated, for example, this status variable is set to the value 1 when an extreme value (minimum) has already occurred in the work area 102. In step S44, it is then checked whether the status variable "MeasurementWndCutAtTheBeginning" is activated, ie has the value 1. If this is the case, the counter of the error counter assigned to this error is subsequently increased by the value 1 in step S46. If it is determined in step S44 that the first extreme value is not within the work area 102, then the variable "MeasurementWndCutAtTheBeginning" is not activated and the process proceeds to step S48 by decreasing the count value of the error counter by one. Subsequently, it is checked in step S50 whether the error counter has reached or exceeded a limit value of 100. If this is the case, a warning is output in step S52, preferably via the control panel of the printing or copying system. Subsequently, the process in step S42 is continued for another toner mark. If it is determined in step S50 that the limit value of the error counter is not exceeded, then the sequence is also continued in step S42.

In FIG. 6 a flowchart is shown in which it is checked whether the second extreme value (in FIG. 3 : Maximum) occurs in the workspace 104 at the end of the measurement window. The process is started in step S60. Subsequently, in step S62, the signal curve of the capacitive toner mark sensor caused by the toner mark and the status of this toner mark are determined and analyzed. Starting from the signal curve, the status variable "MeasurementWndCutAtTheEnd" is determined and set. For example, the status variable "MeasurementWndCutAtTheEnd" is activated when an extreme value in region 104 has occurred. Subsequently, it is checked in step S64 with the aid of the status variable "MeasurementWndCutAtTheEnd" whether an extreme value of the signal curve caused by the toner mark has occurred in the region 104. If this is the case, the count value of an error counter is subsequently increased by 1 in step S66. If this is not the case, the count value of the error counter is reduced by the value 1 in step S68. After step S66 or after step S68, it is checked in step S70 whether the count value has reached or exceeded the limit value 100. If this is the case, then a warning, preferably via a control panel of the printer or copier, issued and the process continues in step S62 for another toner brand. If it is determined in step S70 that the limit value has not been exceeded, the process also continues in step S62.

The error counters are designed so that they can not assume negative values. The activation of the status variable "WrongMarkTriggered" can be caused by defects of the photoconductor or deposits. Defects of the photoconductor can be determined by a band background balance and their effects on the evaluation of the toner brand taken into account (hidden). If the status variable "WrongMarkTriggered" is activated, then it can be assumed that the detected signal curve is not can be used as a basis for controlling the image-forming process or for the control required for a stable image-forming process, so that the last measured value found to be valid is used as the further measured value and output for further output. The areas 102, 104 are protected areas at the beginning of the measurement window or at the measurement window end. If the status variable "MeasurementWndCutAtTheBeginning" and / or the status variable "MeasurementWndCutAtTheEnd" is activated together with the status variable "WrongMarkTriggered", this is an indication of defects of the photoconductor as well as toner deposits. If the "MeasurementWnd CutAtTheBeginning" status variable or the "MeasurementWndCutAtTheEnd" status variable is enabled, this is an indication of timing issues that may be caused by improper trigger timing, brand tape buildup, and tape slippage.

The invention can be used to advantage in electrographic printing or copying machines whose recording methods for image formation are based in particular on the electrophotographic, magnetographic or ionographic recording principle. Further, the printing or copying apparatuses can use a recording method for image formation, in which an image recording medium is directly or indirectly electrically driven pointwise. However, the invention is not limited to such electrographic printing or copying machines.

Although preferred embodiments have been shown and described in detail in the drawings and foregoing description, this should be considered as illustrative and not restrictive of the invention. It should be noted that only the preferred embodiments are shown and described and all changes and modifications that present and future are within the scope of the invention, which is intended to be protected by the appended claims.

LIST OF REFERENCE NUMBERS

10

measuring arrangement

12, 14

plate-shaped electrodes

13, 15

capacitors

16

Photoconductor belt

18

Ground potential photoconductor band

24

evaluation

26

switching unit

32

clock

34

clock signal

38

toner layer

39

toner mark

42, 44

voltage sources

46, 48

switch

100, 102, 104

areas

S10 to S72

steps

Claims (7)

1. A method for processing a measurement signal for detecting a property of a toner mark,

   - in which the toner mark (39) is produced using an image producing device,

   - the toner mark (39) is detected using a measurement arrangement,

   - a measurement signal is output by the measurement arrangement,

   - a signal curve of the measurement signal is determined,

   - and in which a plausibility check is carried out of the determined signal curve, in that

   -- a maximum value and a minimum value of the signal curve are determined,

   -- a first difference value between the maximum value and the minimum value is determined and is output for further processing,

   -- wherein the temporal distance between the occurrence of the maximum value and the occurrence of the minimum value is determined,
   characterized in that

   -- the temporal distance between the beginning or the end of a temporal measurement window for detecting the properties of the toner mark and the occurrence of the maximum value and/or the minimum value is determined,

   -- in that a second difference value between the distance of the maximum value and a reference value and the distance of the minimum value and the reference value is determined, and

   -- in that the second difference value is compared to a minimum difference value and/or a maximum difference value.
2. The method according to one of the preceding claims, characterized in that using the plausibility check it is determined whether the determined measurement value curve, the determined maximum value, the determined minimum value and/or the first difference value are characteristic for the produced toner mark.
3. The method according to one of the preceding claims, characterized in that the measurement signal is determined using a capacitive sensor (10) of the measurement arrangement that has two capacitors (13, 15) situated one after the other in the direction of transport of the image carrier bearing the toner mark, the capacitors (13, 15) being supplied with charge voltages (42, 44) for the charging of the capacitors (13, 15) that are opposite relative to a reference potential (18), and the capacitors (13, 15) being short-circuited after a charge operation, thus producing a charge difference that is a measure of the difference in capacitance of the two capacitors (13, 15) as a result of the positioning of the toner mark (39) in the air gap of at least one capacitor (13, 15).
4. The method according to one of the preceding claims, characterized in that at least two plausibility checks are carried out of the signal curve using two plausibility criteria that are different from each other, to each of which an error counter is allocated, the error counter being incremented if this plausibility criterion is not met and decremented if the plausibility criterion is met, the incrementing preferably taking place by a higher numerical value than the decrementing.
5. The method according to claim 4, characterized in that the numerical value of each error counter is compared to a respective preset boundary value, and when the preset boundary value is reached and/or exceeded, an error message is output and/or a background compensation of the image carrier is carried out.
6. The method according to one of the preceding claims, characterized in that the signal curves of the measurement signals of a plurality of toner marks (39) produced one after the other are detected, and that using the detected signal curves a corrected signal curve is produced, preferably using a mean value formation or median value formation, the plausibility check being carried out for the corrected signal curve.
7. A device for determining a measurement signal for detecting a property of a toner mark,

   - with an image producing unit for producing the toner mark (39),

   - with a measurement arrangement that detects the toner mark (39) and that outputs a measurement signal, characterized by

   - a control unit that is designed to determine the signal curve of the measurement signal and to carry out a plausibility check of the signal curve, in that the control unit

   -- determines a maximum value and a minimum value of the signal curve,

   -- determines a first difference value between the maximum value and the minimum value,

   -- wherein the control unit determines the temporal distance between the occurrence of the maximum value and the occurrence of the minimum value,

   -- wherein the control unit determines the temporal distance between the beginning or the end of a temporal measurement window for detecting the properties of the toner mark and the occurrence of the maximum value and/or the minimum value,

   -- wherein the control unit determines a second difference value between the distance of the maximum value and a reference value and the distance of the minimum value and the reference value,

   -- wherein the control unit compares the second difference value to a minimum difference value and/or maximum difference value.

Images