EP1178362B1 - Image forming device with online image quality evaluation and associated method - Google Patents

Image forming device with online image quality evaluation and associated method Download PDF

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Publication number
EP1178362B1
EP1178362B1 EP01117708A EP01117708A EP1178362B1 EP 1178362 B1 EP1178362 B1 EP 1178362B1 EP 01117708 A EP01117708 A EP 01117708A EP 01117708 A EP01117708 A EP 01117708A EP 1178362 B1 EP1178362 B1 EP 1178362B1
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EP
European Patent Office
Prior art keywords
toner
photoconductor
image
density
accordance
Prior art date
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EP01117708A
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German (de)
French (fr)
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EP1178362A2 (en
EP1178362A3 (en
Inventor
Alfred Gonnella, Jr.
David E. Hockey
Matthias H. Regelsberger
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Eastman Kodak Co
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Eastman Kodak Co
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Publication of EP1178362A3 publication Critical patent/EP1178362A3/en
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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
    • G03G15/5041—Detecting a toner image, e.g. density, toner coverage, using a test patch
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00025—Machine control, e.g. regulating different parts of the machine
    • G03G2215/00029—Image density detection
    • G03G2215/00033—Image density detection on recording member
    • G03G2215/00037—Toner image detection
    • G03G2215/00042—Optical detection

Definitions

  • the invention relates to image generation apparatus and methods for image quality diagnosis. More particularly, the present invention relates to electrophotographic image forming apparatuses and to image quality evaluation methods by on-line measurement of toner density.
  • Electrophotographic image forming devices serve to transfer images to paper or other media.
  • a photoconductor is selectively charged and optically exposed to form an electrostatic latent image on the surface.
  • Toner or other developing materials are applied to the photoconductor surface.
  • the toner is charged and thereby adheres to the surface of the photoconductor in the areas corresponding to the electrostatic latent image.
  • the toner image is transferred to paper or another medium.
  • the paper is usually heated to fix the toner on the paper.
  • the photoconductor is then refreshed, i. any toner and cargo residues are removed.
  • an output copy of a test pattern is visually inspected to evaluate the image forming and development process.
  • the test template is a substantially "perfect" image of the desired output of the electrophotographic imaging apparatus.
  • a service technician creates a copy of the photographic test template and compares the copy with the test template. If the image quality is unacceptable, the toner density is adjusted.
  • the toner density affects the quality of the output image. Artifacts can result from mechanical damage to the electrophotographic subsystems. Durability of consumables can also be the cause of performance degradation. Material fatigue can be the spatial distribution of the toner (for example, the image may have the correct toner density without being properly focused).
  • test template allows a qualitative evaluation of the image quality, which in turn allows conclusions about the toner density on the photoconductor.
  • the toner density is adjusted to adjust the picture quality.
  • image quality may be judged to be good by visual inspection, service, maintenance and other problems are not readily apparent by visual inspection, especially in the initial stages. Such problems usually need to first "become visibleā€ before a user or service technician realizes that the problem exists.
  • test template method is also not very well suited for performing maintenance and service routines. For example, certain variations in toner density may not be apparent. Due to the aforementioned qualitative aspects, the test template method results in varying results depending on the experience and training of the technician as well as other subjective factors. The test template method therefore requires performing maintenance and service routines before or after they are actually required. In addition, service and maintenance problems can not be detected early. Therefore, unexpected downtime and additional repair and maintenance costs for the image forming apparatus are possible.
  • Grayscale rendering uses toner to produce an image in varying amounts, from no toner application to maximum toner application. The density of the toner determines whether part of the image is black or white or has different shades of gray. These differences in toner density make the quantitative assessment of grayscale electrophotographic processes virtually impossible by visual inspection.
  • the present invention provides an electrophotographic (EP) image forming apparatus and method for online quality evaluation of the image forming and development process.
  • the electrophotographic (EP) image forming apparatus and method thereof make a quantitative evaluation of the density of the toner coated on the photoconductor.
  • a toner density representation of the entire photoconductor is generated.
  • the electrophotographic image forming apparatus has a reference system for detecting positions on the surface of the photoconductor.
  • the reference system uses a reference point on the photoconductor and a follower to detect locations relative to the reference point along the length and circumference of the photoconductor.
  • the reference system determines the locations of the density measurements. For each density measurement made, a reference position is recorded. In this way, density measurements are made and evaluated at the same location. The measured toner densities for different locations can be combined to produce a density representation of the toner on the photoconductor.
  • the electrophotographic image forming apparatus is equipped with a photoconductor rotatably supported on support rollers.
  • a primary charger, an exposure device, a toner station, a transfer charger, a fuser, and a cleaner are operatively disposed about the photoconductor.
  • a transmitted light densitometer is equipped with a light emitter and a light collector, which are arranged in operative relation to the photoconductor.
  • the densitometer is also connected to a microprocessor, which is provided with a memory.
  • the microprocessor is in turn connected to input and output interfaces.
  • an image frame is loaded on the photoconductor.
  • a step wedge or test image is optically exposed to form an electrostatic image on the image field.
  • the step wedge is designed for grayscale reproduction.
  • the electrostatic image has step portions corresponding to the steps of the step wedge. The toning station is disabled, so no toner is currently being applied.
  • the photoconductor density is determined for each step area of the step wedge on the image field.
  • five or more measurements of the photoconductor density of each step area are made by means of the transmitted light densitometer.
  • the densitometer measures a voltage value corresponding to the amount of light energy passing through the photoconductor on an optical beam path between the light emitter and the light collector.
  • the voltage value corresponds to the density of the toner.
  • the voltage values of the photoconductor are stored separately in memory, each photoconductor voltage value being referred to its location on the photoconductor.
  • the image field is then loaded a second time.
  • the transfer station and the fixing device are briefly deactivated to avoid exposure to the photoconductor.
  • the cleaner removes any charge from the photoconductor.
  • the step wedge is optically exposed to form an electrostatic image on the image field for the second time.
  • the electrostatic image has step areas which correspond to the steps of the step wedge. These step areas are the same as those used to measure the photoconductor voltage.
  • the toner station applies toner to the image field.
  • the toner forms a toner image corresponding to the electrostatic image, which in turn corresponds to the step wedge.
  • the combined photoconductor and toner density is determined.
  • five density measurements are taken from each step area using the transmitted light densitometer.
  • the combined voltage values are stored separately in memory, each combined voltage value being again referred to its location on the photoconductor.
  • the mean measured toner density is determined for each step area on the image field. For each step range, the measured photoconductor voltage is subtracted from the combined voltage value measured at the same location to provide a measured value of toner voltage or density for that location. The measured toner voltage values are averaged for each stage in the step wedge to provide a mean measured toner voltage value for each stage.
  • the average measured toner voltage values are compared with the toner voltage setpoints for each stage of the step wedge.
  • the toner voltage set points are those specified by the manufacturer in the electrostatic image forming apparatus specifications.
  • the measured toner voltage values indicate the toner density. Too high a measured toner voltage value indicates that the toner application is too strong. If the toner tension value is too low, it indicates that the toner application is too weak. In either case, the toner application can be adjusted and rechecked until the measured toner voltage values are equal to the toner target voltage or within an acceptable range of the toner target voltage.
  • each image field of the photoconductor is evaluated successively.
  • the average measured toner voltage value for the step on the step wedge over a full rotation of the photoconductor is representative.
  • the present invention quantitatively assesses the image quality of an electrophotographic image forming apparatus by means of a reference system to produce a toner density representation of the toner on the surface of the photoconductor.
  • the actual or measured toner densities are compared to nominal densities according to the manufacturer's specifications, regardless of the user's subjective visual checks and comparisons.
  • the density values of the toner indicate the image quality in an electrophotographic process.
  • Fig. 1 shows a schematic representation of an electrophotographic image forming apparatus 100 according to an embodiment of the invention.
  • the electrophotographic image forming apparatus 100 includes a photoconductor 105 disposed on support rollers 110 and a motor 115 that moves the photoconductor 105 in the direction indicated by arrow A.
  • the electrophotographic image forming apparatus 100 further includes a primary charger 118, an exposure apparatus 120, a toner station 125, a transfer charger 130, a fixing station 140, and a cleaner 150 operatively disposed around the photoconductor 105.
  • the photoconductor 105 includes a roller-mounted ribbon configuration, it may be otherwise supported by use of a drum or other suitable configurations. While a particular configuration and arrangement is shown for the electrophotographic imaging apparatus 100, the invention may employ other configurations and arrangements, including but not limited to those described with reference to FIGS. Arrangements with additional components.
  • the electrophotographic image forming apparatus 100 further includes a densitometer 160 connected to a light emitter 165 and a light collector 170.
  • the densitometer 160 is connected to a microprocessor 175 equipped with a memory 180.
  • the microprocessor 175 is connected to an input interface 185 and to an output interface 190.
  • the microprocessor 175 may be connected for communication with other microprocessors in the electrophotographic imaging apparatus 100.
  • the input interface 185 may be a keyboard, a touch screen, or the like.
  • the output interface 190 may be a printer, a monitor, or the like.
  • the input and output interface 185, 190 may be the same component. There may be a plurality of densitometers or other components.
  • a toner density representation of the entire photoconductor 105 is generated.
  • the electrophotographic image forming apparatus 100 includes a reference system not shown for finding positions on the surface of the photoconductor 105.
  • the reference system utilizes a reference point (not shown) on the photoconductor 105 Photoconductor 105 and a follower (not shown) to determine positions relative to the reference point along the length and the circumference of the photoconductor 105.
  • the reference point is preferably a seam.
  • the process field or another fixed point on the photoconductor can be used.
  • the follower is essentially a timer that indicates to the photoconductor 105 when to proceed from the reference point to a particular location. By knowing the distance the photoconductor 105 travels within the measured time, the location on the photoconductor 105 can be determined.
  • the follower can also be another measuring device and determine the location by other means. Alternative reference systems are also usable.
  • the reference system is used to designate the locations for the density measurements. For each density measurement made, a reference position is recorded. In this way, and as described below, a density value of the photoconductor may be subtracted from the combined density value of the photoconductor and the toner at the same location so as to determine the measured toner density for that location.
  • the measured toner densities for various locations can be combined to produce a density representation of the toner deposited on the photoconductor 105.
  • the primary charger 118 electrostatically charges an image field on the surface of the photoconductor 105.
  • the image field corresponds to the size of the image to be formed and can cover the entire surface of the photoconductor 105.
  • the photoconductor 105 is designed to receive a plurality of image fields.
  • the photoconductor 105 rotates to pass the charged image field past the exposure apparatus 120.
  • the exposure device 120 optically exposes the charged image field to produce an electrostatic latent image on the photoconductor 105.
  • the photoconductor 105 rotates to pass the electrostatic image at the toning station 125.
  • the toning station 125 deposits on the surface of the photoconductor 105 toner or other developing material.
  • the toner is charged so that it is at the electrostatic image adheres.
  • the description refers to a dry toner, it is also usable as a liquid or the like suitable developing material.
  • the photoconductor 105 rotates to pass the electrostatic image past the transfer charger 130.
  • the transfer charger 130 transfers the electrostatic toner image from the photoconductor 105 to paper or other medium selected to receive the image.
  • the paper S is removed from the paper supply (135) and passes between the transfer charger 130 and the photoconductor 105.
  • the paper S is then passed through the fuser 140 where the toner is fixed on the paper.
  • the photoconductor 105 rotates to pass the image field through the cleaner 150.
  • the cleaner removes any toner and charge residues and thus prepares the photoconductor for another image. Although these operations are described in steps, they are preferably sequential and continuous as the photoconductor goes through one cycle.
  • the densitometer 160 is connected to the light emitter 165 and the light collector 170.
  • the light emitter 165 and the light collector 170 are disposed on both sides of the photoconductor 105 opposite to each other, following the toner station 125, that is, the position where toner is applied.
  • the light emitter 165 is disposed opposite the surface where the toner is applied.
  • the densitometer 160 is preferably shown as a transmitted light densitometer. However, an incident densitometer as well as any other density measuring device for measuring the toner densities on the photoconductor 105 is also usable. When using an incident light densitometer, the positions of the light emitter 165 and the light collector 170 must be changed accordingly. The light emitter 165 and the light collector 170 are not necessarily components of the density measuring device.
  • the beam path from the light emitter 165 to the light collector 170 passes through the photoconductor 105.
  • the densitometer 160 generates voltage values proportional to the light absorption in the beam path.
  • the voltage values indicate the density of the photoconductor 105 and / or the toner on the surface.
  • the voltage values of the densitometer 160 increase with increasing opacity of the photoconductor 105, that is, the greater the toner application on the photoconductor 105. In order to exclude fluctuations caused by the photoconductor 105, it is possible to subtract the voltage values of the photoconductor without toner application from the voltage values of the photoconductor with the toner charge.
  • the densitometer 160 passes the voltage values to the microprocessor 175.
  • the microprocessor 175 transfers the voltage values to the output interface 190.
  • the voltage values can be stored in the memory 180 for further analysis and / or subsequent transmission to the output interface.
  • the voltage values may be transmitted or amplified in the form included in the densitometer 160 or otherwise conditioned to enhance transmission to the output interface 190.
  • the microprocessor 175 may translate the voltage values into other suitable factors, such as density, thickness, etc.
  • the microprocessor 175 receives commands and instructions via the input interface 185.
  • the electrophotographic image forming apparatus 100 evaluates the electrophotographic process to determine whether the toner density and thus the image quality conform to the specifications of the manufacturer.
  • the electrophotographic image forming apparatus 100 checks whether the density of the toner on the photoconductor 105 corresponds to the density required for the tonal range specified by the specification. In a grayscale sound reproduction process, the toner densities gradually change. In this case, the toner densities of the various stages are evaluated.
  • Fig. 2 shows a step wedge 200 for evaluating the various toner densities in a grayscale sound reproduction system.
  • Staged wedge 200 is an image with graded gray levels corresponding to the levels of toner density associated with a particular associated with electrophotographic image forming apparatus.
  • the step wedge of Figure 2 has a total of 16 stages, ranging from stage 210 (no exposure and no toner application) to stage 220 (maximum exposure and maximum toner application).
  • the electrophotographic image forming apparatus 100 prints at least one image of the step wedge.
  • the number of images corresponds to the number of image fields that match the length or circumference of the photoconductor. If more than one image is to be printed, the images are printed one after another. By successively printing a number of images corresponding to the number of image frames on the photoconductor, the entire surface of the photoconductor can be evaluated.
  • six frames are provided on the photoconductor 105. Accordingly, the electrophotographic image forming apparatus 100 prints six consecutive images to evaluate the electrophotographic process.
  • a (not shown) process field which is arranged between the image fields. The process panel is exposed with the maximum toner density, D max , or with each true density.
  • Expression by the electrophotographic image forming apparatus 100 is not required as long as toner is applied to the photoconductor 105.
  • the printed output is related to the operation of the electrophotographic image forming apparatus 100.
  • the printed images enable visual assessment and off-line measurement of print density with commercially available brightness meters and densitometers.
  • the steps of the step wedge correspond to the step areas on the image field.
  • Each of the step areas is assigned a specific location, as in the reference system certainly.
  • the densitometer 160 performs at least one density measurement of each step area of each image field.
  • the voltage is measured while the light emitter 165 throws light through the toner and the photoconductor 105 onto the light collector 170. Better measurement results can be achieved by improving the signal-to-noise ratio for each stage.
  • the beam path covers 1.27 cm of the surface of the photoconductor.
  • at least five density or voltage measurements are made for each step area in each frame. The five measurements are taken at five different positions of the photoconductor, but all within the same step range. More measurements increase the accuracy of the final voltage / density readings.
  • These voltage values indicate the optical properties, i. the density of the photoconductive photoconductor 105.
  • the combined voltage values are stored separately in the memory 180 by the microprocessor 175.
  • the density measurements are also carried out without toner being applied to the photoconductor 105. These density measurements are preferably performed before the densities with toner applied.
  • the reference system can be used to determine the photoconductor density for each step range, as well as subsequent densities of photoconductor and toner.
  • the toner station will be temporarily disabled.
  • the six images represent rotation of the photoconductor 105. Since toner is not applied, an empty or similar image may be used as long as these photoconductor voltage values correspond to the step areas on the image field where the step wedge measurements are made without toner.
  • the densitometer performs at least one and preferably five photoconductor voltage measurements for each step area in each frame. The five measurements are taken at five different positions of the photoconductor, but all within the same step range.
  • the reference system determines the locations of the photoconductor voltage values so that the voltage measurements for toner and photoconductor are made at the same locations.
  • the process field is measured to obtain a voltage value of the photoconductor.
  • the photoconductor voltage values correspond to the optical properties of the photoconductor 105, i. its density.
  • the photoconductor voltage values are stored in memory 180.
  • the photoconductor voltage value is subtracted from the corresponding combined voltage value in the same image field (the reference system identifies the voltage values for the same location). The result is a measured toner voltage value for each stage in each frame. The measured toner voltage value indicates the toner density for each step range of the respective image field. Similarly, the toner tension value for the process field, which is the maximum toner density, is determined.
  • the measured toner voltage values for a given step range in all image fields are averaged to obtain a mean measured toner voltage value for the particular step in the step wedge. For example, if five measurements of the toner voltage are made for each stage in each frame and if there are a total of six panels, then 30 measured toner voltage values are averaged to obtain a mean measured toner voltage value for the stage area; this value indicates the toner density for the particular step of the step wedge over a full rotation of the photoconductor 105.
  • the process field is likewise averaged to obtain the measured toner tension value for the maximum toner density, D max , or any pure density.
  • the measured toner tension values correspond to the optical properties of the toner and thus its density.
  • Fig. 3 shows an example of a summary of a typical result of such averages over six consecutive frames for all stages, including the process field.
  • the printed image fields are evaluated one after another.
  • Field-by-frame analysis based on an average of five measurements per stage can determine localized defects in the photoconductor that cause the density of one or more stages not to fall within the desired setpoint range.
  • the average measured toner voltage value for each stage is compared to a toner voltage setpoint for that stage.
  • the toner voltage set point is the manufacturer's specifications for toner density.
  • the measured toner voltage values indicate the toner density. If the measured toner tension value is greater than the toner tension set point, too much toner has been applied to the step in the step wedge. If the measured toner tension value is less than the toner tension setpoint, too little toner has been applied to that stage in the step wedge. In both cases, the toner application can be adjusted and retested until the measured toner voltage values are within the toner voltage setpoint or within an acceptable range of the toner voltage setpoint.
  • the microprocessor 175 provides the measured toner voltage values to the output interface 190.
  • the measured toner voltage values may be presented in the form of a table, such as that shown in Figure 3, to compare the measured toner voltage values to the toner voltage setpoints.
  • the measured toner voltage values may be stored in memory 180 to provide historical test data, or may be downloaded to a data storage device (not shown).
  • the evaluation of the electrophotographic process can be performed as a stand-alone diagnostic routine or as part of a larger diagnostic routine. Users and service technicians may assess via input interface 185.
  • the Judgment may also be performed as part of an error detection routine in which a warning signal is output to the user when deviations are detected between the measured toner voltage values and the toner voltage setpoints.
  • step 410 an image field on a photoconductor is loaded for the first time.
  • the photoconductor may comprise a belt and a roller, a drum or other suitable configuration.
  • a step wedge or test image is optically exposed to form an electrostatic image on the image field for the first time.
  • the step wedge is designed for grayscale reproduction and comprises 16 density levels.
  • the electrostatic image has step portions corresponding to the steps of the step wedge.
  • the process field is exposed in a similar way.
  • the toner station is disabled to avoid toner on the photoconductor.
  • the photoconductor density is determined for each step area of the step wedge on the image field.
  • five photoconductor density measurements are made from each stage region by means of a transmitted light densitometer comprising a light emitter and a light collector operatively disposed adjacent to the photoconductor.
  • the densitometer measures the density as a voltage value corresponding to the amount of light energy that passes through the photoconductor on a beam path between the light emitter and light collector.
  • the measurement of the photoconductor voltages of the process field are carried out in a similar way.
  • the voltage values of the photoconductor are stored separately in the memory, each photoconductor voltage value being determined in relation to its position on the photoconductor.
  • the densitometer other density measuring devices can be used.
  • the transfer station and the fixing device are deactivated to prevent exposure of the photoconductor.
  • the cleaner removes any charge from the photoconductor.
  • step 440 the image field is loaded a second time.
  • step 450 the step wedge or test image is optically exposed to form an electrostatic image on the image field for the second time.
  • the electrostatic image has step areas corresponding to the steps of the step wedge.
  • the step areas in step 450 are the same as the step areas in step 420.
  • step 460 the toning station is activated to apply toner to the image field.
  • the toner forms a toner image corresponding to the electrostatic image, which in turn corresponds to the step wedge. Toner is also applied to the process field.
  • step 470 the photoconductor and toner densities are determined for each step area of the step wedge on the image field.
  • five density measurements of each step range are made by means of the transmitted light densitometer in a manner similar to step 430.
  • the densitometer measures the density as a voltage value corresponding to the amount of light energy passing through the photoconductor and toner on a light emitter to light collector beam path.
  • the combined voltage values are stored separately in memory, each combined voltage value being determined again in relation to its position on the photoconductor.
  • steps 410-470 are repeated if the photoconductor has more than one frame.
  • step 410 through step 470 are repeated in parallel for each frame.
  • the frames are loaded sequentially in step 410.
  • the image fields are then exposed successively with the step wedge, etc. In this way, the toner density for the entire length or the entire circumference of the photoconductor can be evaluated.
  • step 480 the average measured toner density is determined for each step of the step wedge (if there is more than one image field, this is done for all frames).
  • the photoconductor voltage value is subtracted from the combined voltage value to provide a measured toner voltage value for that location or to obtain a toner density value.
  • the measured toner voltage values are averaged for each stage in the image field to obtain a mean measured toner voltage value for each stage.
  • step 490 the average measured toner tension values or density values for each stage of the step wedge are compared to the toner tension setpoints.
  • the measured toner voltage values and toner voltage references are tabulated on the output interface, as shown by way of example in FIG.
  • the toner voltage set points are those specified by the manufacturer in the electrostatic image forming apparatus specifications.
  • the photoconductor may bypass step 440 (second load) and step 450 (second optical exposure).
  • the photoconductor is transportable to the toning station without being affected by other processing components.
  • the photoconductor could pass through the other components or traverse the toner station a second time in the reverse direction to be charged with toner.
  • reversing the direction of the photoconductor involves additional complex steps when the photoconductor includes multiple frames.
  • a second densitometer could be located in front of the toning station to determine the photoconductor densities before applying the toner.
  • the voltage values could be used to determine area-specific problems associated with the photoconductor.
  • the voltage values could also be used, for example, to determine if there is a surface problem or other problem in a particular step area.
  • the user could choose any measured toner voltage value as well as the rest Check voltage values. Additional statistical analysis could be provided to identify problem areas. Therefore, while the invention has been described with particular reference to preferred embodiments, the invention is not limited thereto, but changes and modifications may be made within the scope of the following claims.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Facsimiles In General (AREA)
  • Image Analysis (AREA)

Abstract

An electrophotographic (EP) image-forming device and related method are provided for on-line quantitative assessment of the image information and development process. The EP image-forming device has a primary charger (118), an exposure device (120), a toning station (125), a transfer charger (130), a fusion station (140), and a cleaner (150) operatively disposed about the photoconductor. A transmission densitometer (165, 170) is positioned adjacent to the photoconductor. The densitometer determines the photoconductor density and the combination photoconductor and toner density for each step area on the image frame. The density readings are stored in memory. The photoconductor densities are subtracted from the combined densities to provide measured toner densities, which are then averaged for each step area. The average measured toner densities or voltage readings are compared to the aim toner densities or voltage readings for each step in the step tablet to quantitatively assess the image quality of the image-forming process. Preferably, every image frame on the photoconductor is assessed successively.

Description

Die Erfindung betrifft Bilderzeugungsvorrichtungen und Verfahren zur BildqualitƤtsdiagnose. Insbesondere betrifft die vorliegende Erfindung elektrofotografische Bilderzeugungsvorrichtungen und Verfahren mit einer BildqualitƤtsbewertung durch Online-Messung der Tonerdichte.The invention relates to image generation apparatus and methods for image quality diagnosis. More particularly, the present invention relates to electrophotographic image forming apparatuses and to image quality evaluation methods by on-line measurement of toner density.

Elektrofotografische Bilderzeugungsvorrichtungen dienen dazu, Bilder auf Papier oder andere Medien zu Ć¼bertragen. Ein Fotoleiter wird selektiv geladen und optisch belichtet, um ein elektrostatisches Latentbild auf der OberflƤche auszubilden. Toner oder andere Entwicklungsmaterialien werden auf die FotoleiteroberflƤche aufgetragen. Der Toner wird geladen und haftet dadurch an der OberflƤche des Fotoleiters in den Bereichen, die dem elektrostatischen Latentbild entsprechen. Das Tonerbild wird auf Papier oder auf ein anderes Medium Ć¼bertragen. Das Papier wird normalerweise erwƤrmt, um den Toner auf dem Papier zu fixieren. Zur Vorbereitung fĆ¼r ein weiteres Bild wird der Fotoleiter dann aufgefrischt, d.h. jegliche Toner- und Ladungsreste werden beseitigt.Electrophotographic image forming devices serve to transfer images to paper or other media. A photoconductor is selectively charged and optically exposed to form an electrostatic latent image on the surface. Toner or other developing materials are applied to the photoconductor surface. The toner is charged and thereby adheres to the surface of the photoconductor in the areas corresponding to the electrostatic latent image. The toner image is transferred to paper or another medium. The paper is usually heated to fix the toner on the paper. To prepare for another image, the photoconductor is then refreshed, i. any toner and cargo residues are removed.

In vielen elektrofotografischen Bilderzeugungsvorrichtungen wird eine ausgegebene Kopie einer Testvorlage visuell geprĆ¼ft, um den Bilderzeugungs- und Entwicklungsprozess zu bewerten. Die Testvorlage ist ein im wesentlichen "perfektes" Bild der gewĆ¼nschten Ausgabe der elektrofotografischen Bilderzeugungsvorrichtung. Ein Servicetechniker erstellt eine Kopie der fotografischen Testvorlage und vergleicht die Kopie mit der Testvorlage. Falls die BildqualitƤt nicht annehmbar ist, wird die Tonerdichte eingestellt.In many electrophotographic image forming apparatus, an output copy of a test pattern is visually inspected to evaluate the image forming and development process. The test template is a substantially "perfect" image of the desired output of the electrophotographic imaging apparatus. A service technician creates a copy of the photographic test template and compares the copy with the test template. If the image quality is unacceptable, the toner density is adjusted.

Aus US 5 150 155 ist die automatische Einstellung einer Bilderzeugungsmaschine unter Benutzung eines Testbildes mit verschiedenen Graustufen bekannt. Die Einstellung durch den Vergleich des Testbildes mit Sollwerten durch eine Bedienungsperson ist ebenfalls als Stand der Technik beschrieben. Eine Anzeige eines Ausgabediagramms zur Anleitung der Bedienungsperson ist aus EP 0 461 810 A2 bekannt.From US Pat. No. 5,150,155, the automatic adjustment of an image-forming machine using a test pattern with different gray levels is known. The adjustment by the comparison of the test image with target values by an operator is also described as prior art. An indication of an output diagram for guiding the operator is known from EP 0 461 810 A2.

Neben weiteren Faktoren beeinflusst die Tonerdichte die QualitƤt des Ausgabebildes. Artefakte kƶnnen durch mechanische BeschƤdigung der elektrofotografischen Subsysteme entstehen. Auch die Haltbarkeit der Verbrauchsmaterialien kann die Ursache fĆ¼r LeistungseinbuƟen sein. MaterialermĆ¼dung kann die rƤumliche Verteilung des Toners beeintrƤchtigen (so kann das Bild beispielsweise die richtige Tonerdichte aufweisen, ohne jedoch einwandfrei fokussiert zu sein).Among other factors, the toner density affects the quality of the output image. Artifacts can result from mechanical damage to the electrophotographic subsystems. Durability of consumables can also be the cause of performance degradation. Material fatigue can be the spatial distribution of the toner (for example, the image may have the correct toner density without being properly focused).

Die Verwendung einer Testvorlage ermƶglicht eine qualitative Bewertung der BildqualitƤt, was wiederum RĆ¼ckschlĆ¼sse bezĆ¼glich der Tonerdichte auf dem Fotoleiter ermƶglicht. Die Tonerdichte wird zur Abstimmung der BildqualitƤt eingestellt. Obwohl die BildqualitƤt durch SichtprĆ¼fung mƶglicherweise als gut beurteilt wird, sind Service-, Wartungs- und sonstige Probleme nicht ohne weiteres durch SichtprĆ¼fung zu erkennen, insbesondere nicht in den Anfangsphasen. Derartige Probleme mĆ¼ssen normalerweise zuerst "sichtbar" werden, bevor ein Benutzer oder ein Servicetechniker erkennt, dass das Problem vorliegt.The use of a test template allows a qualitative evaluation of the image quality, which in turn allows conclusions about the toner density on the photoconductor. The toner density is adjusted to adjust the picture quality. Although image quality may be judged to be good by visual inspection, service, maintenance and other problems are not readily apparent by visual inspection, especially in the initial stages. Such problems usually need to first "become visible" before a user or service technician realizes that the problem exists.

Die Testvorlagenmethode ist zudem zur DurchfĆ¼hrung von Wartungs- und Serviceroutinen nicht besonders gut geeignet. So sind mƶglicherweise bestimmte Abweichungen in der Tonerdichte nicht erkennbar. Aufgrund der zuvor genannten qualitativen Aspekte ergeben sich aus der Testvorlagenmethode wechselnde Ergebnisse, und zwar je nach Erfahrung und Ausbildung des Technikers sowie anderer subjektiver Faktoren. Die Testvorlagenmethode bedingt daher die DurchfĆ¼hrung von Wartungs- und Serviceroutinen, bevor oder nachdem diese tatsƤchlich erforderlich wƤren. Zudem lassen sich Service- und Wartungsprobleme nicht frĆ¼hzeitig erkennen. Daher sind unerwartete Ausfallzeiten und zusƤtzliche Reparatur- und Wartungskosten fĆ¼r die Bilderzeugungsvorrichtung mƶglich.The test template method is also not very well suited for performing maintenance and service routines. For example, certain variations in toner density may not be apparent. Due to the aforementioned qualitative aspects, the test template method results in varying results depending on the experience and training of the technician as well as other subjective factors. The test template method therefore requires performing maintenance and service routines before or after they are actually required. In addition, service and maintenance problems can not be detected early. Therefore, unexpected downtime and additional repair and maintenance costs for the image forming apparatus are possible.

Bei Verwendung einer Graustufenwiedergabe treten die Schwierigkeiten in Bezug auf die Verwendung dieser Testvorlagenmethode zur Bewertung des Bilderzeugungs- und Entwicklungsprozesses noch deutlicher hervor. Bei der Graustufenwiedergabe wird Toner zum Erzeugen eines Bildes in unterschiedlichen Mengen aufgetragen, ausgehend von gar keinem Tonerauftrag bis hin zum maximalen Tonerauftrag. Die Dichte des Toners bestimmt, ob ein Teil des Bildes schwarz oder weiƟ ist oder unterschiedliche Grauschattierungen aufweist. Diese Unterschiede in der Tonerdichte machen die quantitative Bewertung von elektrofotografischen Graustufenprozessen durch SichtprĆ¼fung praktisch unmƶglich.When using grayscale rendering, the difficulties in using this test template method to evaluate the imaging and development process are even more pronounced. Grayscale rendering uses toner to produce an image in varying amounts, from no toner application to maximum toner application. The density of the toner determines whether part of the image is black or white or has different shades of gray. These differences in toner density make the quantitative assessment of grayscale electrophotographic processes virtually impossible by visual inspection.

Um die mit den visuellen PrĆ¼fungen der Testvorlage verbundenen Schwierigkeiten zu vermeiden, ermƶglichen kommerziell verfĆ¼gbare HelligkeitsmessgerƤte und Densitometer eine visuelle Offline-Bewertung und -Messung der gedruckten Dichte. Diese Techniken erfordern jedoch zusƤtzliche GerƤte sowie zusƤtzliche Einstellarbeiten zur Verwendung der GerƤte. Sie fĆ¼hren zudem dazu, dass Servicerufe verzƶgert werden und sind zudem ein unzureichendes Mittel zur Bewertung der Tonerdichte auf dem Fotoleiter.In order to avoid the difficulties associated with visual testing of the test chart, commercially available brightness meters and densitometers allow visual off-line evaluation and measurement of the printed density. However, these techniques require additional equipment and additional adjustments to use the equipment. They also delay service calls and are also an insufficient means of evaluating toner density on the photoconductor.

Es besteht daher Bedarf nach einer quantitativen Online-Bewertung der BildqualitƤt in einer elektrofotografischen Bilderzeugungsvorrichtung.Therefore, there is a demand for quantitative on-line evaluation of image quality in an electrophotographic image forming apparatus.

Die vorliegende Erfindung sieht eine elektrofotografische (EP) Bilderzeugungsvorrichtung und ein zugehƶriges Verfahren zur Online-QualitƤtsbewertung des Bilderzeugungs- und Entwicklungsprozesses vor. Die elektrofotografische (EP) Bilderzeugungsvorrichtung und das diesbezĆ¼gliche Verfahren nehmen eine quantitative Bewertung der Dichte des auf dem Fotoleiter aufgetragenen Toners vor.The present invention provides an electrophotographic (EP) image forming apparatus and method for online quality evaluation of the image forming and development process. The electrophotographic (EP) image forming apparatus and method thereof make a quantitative evaluation of the density of the toner coated on the photoconductor.

Nach einem Aspekt der vorliegenden Erfindung wird eine Tonerdichtedarstellung des gesamten Fotoleiters erzeugt. Die elektrofotografische Bilderzeugungsvorrichtung hat ein Referenzsystem zur Lagebstimmung von Positionen auf der OberflƤche des Fotoleiters. Das Referenzsystem nutzt einen Referenzpunkt auf dem Fotoleiter sowie eine Folgeeinrichtung, um Lagestellen in Bezug zum Referenzpunkt entlang der LƤnge und des Umfangs des Fotoleiters zu ermitteln.In one aspect of the present invention, a toner density representation of the entire photoconductor is generated. The electrophotographic image forming apparatus has a reference system for detecting positions on the surface of the photoconductor. The reference system uses a reference point on the photoconductor and a follower to detect locations relative to the reference point along the length and circumference of the photoconductor.

Das Referenzsystem ermittelt die Lagestellen der Dichtemessungen. FĆ¼r jede erfolgte Dichtemessung wird eine Referenzposition festgehalten. Auf diese Weise werden Dichtemessungen an derselben Lagestelle vorgenommen und ausgewertet. Die gemessenen Tonerdichten fĆ¼r verschiedene Lagestellen lassen sich zusammenfĆ¼hren, um eine Dichtedarstellung des Toners auf dem Fotoleiter zu erzeugen.The reference system determines the locations of the density measurements. For each density measurement made, a reference position is recorded. In this way, density measurements are made and evaluated at the same location. The measured toner densities for different locations can be combined to produce a density representation of the toner on the photoconductor.

Die elektrofotografische Bilderzeugungsvorrichtung ist mit einem Fotoleiter ausgestattet, der drehbar auf Tragwalzen gelagert ist. Ein primƤrer Lader, eine Belichtungseinrichtung, eine Tonerstation, ein Ɯbertragungslader, eine Fixierstation und ein Reiniger sind in Wirkbeziehung um den Fotoleiter angeordnet. Ein Durchlichtdensitometer ist mit einem Lichtemitter und einem Lichtkollektor ausgestattet, die in Wirkbeziehung zum Fotoleiter angeordnet sind. Das Densitometer ist zudem mit einem Mikroprozessor verbunden, der mit einem Speicher versehen ist. Der Mikroprozessor ist wiederum mit Eingabe- und Ausgabeschnittstellen verbunden. Zwar werden einzelne Komponenten dargestellt, aber jegliche Komponenten kƶnnen mehrfach vorhanden sein, auch das Densitometer.The electrophotographic image forming apparatus is equipped with a photoconductor rotatably supported on support rollers. A primary charger, an exposure device, a toner station, a transfer charger, a fuser, and a cleaner are operatively disposed about the photoconductor. A transmitted light densitometer is equipped with a light emitter and a light collector, which are arranged in operative relation to the photoconductor. The densitometer is also connected to a microprocessor, which is provided with a memory. The microprocessor is in turn connected to input and output interfaces. Although individual components are shown, but any components may be present several times, including the densitometer.

In der erfindungsgemƤƟen elektrofotografischen Bilderzeugungsvorrichtung wird ein Bildfeld auf dem Fotoleiter geladen. Ein Stufenkeil oder ein Testbild wird optisch belichtet, um auf dem Bildfeld ein elektrostatisches Bild zu erzeugen. Vorzugsweise ist der Stufenkeil auf Graustufenwiedergabe ausgelegt. Das elektrostatische Bild weist Stufenbereiche auf, die den Stufen des Stufenkeils entsprechen. Die Tonerstation ist deaktiviert, so dass zur Zeit kein Toner aufgebracht wird.In the electrophotographic image forming apparatus of the present invention, an image frame is loaded on the photoconductor. A step wedge or test image is optically exposed to form an electrostatic image on the image field. Preferably, the step wedge is designed for grayscale reproduction. The electrostatic image has step portions corresponding to the steps of the step wedge. The toning station is disabled, so no toner is currently being applied.

Die Fotoleiterdichte wird fĆ¼r jeden Stufenbereich des Stufenkeils auf dem Bildfeld ermittelt. Vorzugsweise werden fĆ¼nf oder mehr Messungen der Fotoleiterdichte von jedem Stufenbereich mit Hilfe des Durchlichtdensitometers vorgenommen.The photoconductor density is determined for each step area of the step wedge on the image field. Preferably, five or more measurements of the photoconductor density of each step area are made by means of the transmitted light densitometer.

Das Densitometer misst einen Spannungswert entsprechend der Menge der Lichtenergie, die durch den Fotoleiter auf einem optischen Strahlengang zwischen Lichtemitter und Lichtkollektor tritt. Der Spannungswert entspricht der Dichte des Toners. Die Spannungswerte des Fotoleiters werden im Speicher getrennt abgelegt, wobei jeder Fotoleiter-Spannungswert in Bezug auf dessen Lage auf dem Fotoleiter bezeichnet wird. Das Bildfeld wird dann ein zweites Mal geladen. Die Ɯbertragungsstation und die Fixiereinrichtung werden kurzzeitig deaktiviert, um eine Beaufschlagung des Fotoleiters zu vermeiden. Der Reiniger entfernt jegliche Ladung vom Fotoleiter.The densitometer measures a voltage value corresponding to the amount of light energy passing through the photoconductor on an optical beam path between the light emitter and the light collector. The voltage value corresponds to the density of the toner. The voltage values of the photoconductor are stored separately in memory, each photoconductor voltage value being referred to its location on the photoconductor. The image field is then loaded a second time. The transfer station and the fixing device are briefly deactivated to avoid exposure to the photoconductor. The cleaner removes any charge from the photoconductor.

Der Stufenkeil wird optisch belichtet, um zum zweiten Mal ein elektrostatisches Bild auf dem Bildfeld ausbilden zu kƶnnen. Das elektrostatische Bild weist Stufenbereiche auf, die den Stufen des Stufenkeils entsprechen. Diese Stufenbereiche sind die gleichen, die auch fĆ¼r die Messung der Fotoleiterspannung herangezogen worden sind.The step wedge is optically exposed to form an electrostatic image on the image field for the second time. The electrostatic image has step areas which correspond to the steps of the step wedge. These step areas are the same as those used to measure the photoconductor voltage.

Die Tonerstation trƤgt Toner auf dem Bildfeld auf. Der Toner bildet ein Tonerbild aus, das dem elektrostatischen Bild entspricht, welches wiederum dem Stufenkeil entspricht.The toner station applies toner to the image field. The toner forms a toner image corresponding to the electrostatic image, which in turn corresponds to the step wedge.

FĆ¼r jeden Stufenbereich des Stufenkeils auf dem Bildfeld wird die kombinierte Fotoleiter- und Tonerdichte ermittelt. Vorzugsweise werden fĆ¼nf Dichtemessungen von jedem Stufenbereich mit Hilfe des Durchlichtdensitometers vorgenommen. Die kombinierten Spannungswerte werden im Speicher getrennt abgelegt, wobei jeder kombinierte Spannungswert wieder in Bezug auf dessen Lage auf dem Fotoleiter bezeichnet wird.For each step area of the step wedge on the image field, the combined photoconductor and toner density is determined. Preferably, five density measurements are taken from each step area using the transmitted light densitometer. The combined voltage values are stored separately in memory, each combined voltage value being again referred to its location on the photoconductor.

Die mittlere gemessene Tonerdichte wird fĆ¼r jeden Stufenbereich auf dem Bildfeld ermittelt. FĆ¼r jeden Stufenbereich wird die gemessene Fotoleiterspannung von dem an derselben Lagestelle gemessenen, kombinierten Spannungswert subtrahiert, um fĆ¼r diese Lagestelle einen gemessenen Wert fĆ¼r die Tonerspannung oder Dichte bereitzustellen. Die gemessenen Tonerspannungswerte werden fĆ¼r jede Stufe in dem Stufenkeil gemittelt, um einen mittleren, gemessenen Tonerspannungswert fĆ¼r jede Stufe bereitzustellen.The mean measured toner density is determined for each step area on the image field. For each step range, the measured photoconductor voltage is subtracted from the combined voltage value measured at the same location to provide a measured value of toner voltage or density for that location. The measured toner voltage values are averaged for each stage in the step wedge to provide a mean measured toner voltage value for each stage.

Die mittleren, gemessenen Tonerspannungswerte werden fĆ¼r jede Stufe des Stufenkeils mit den Tonerspannungssollwerten verglichen. Die Tonerspannungssollwerte sind die, die der Hersteller in den technischen Daten fĆ¼r die elektrostatische Bilderzeugungsvorrichtung angibt.The average measured toner voltage values are compared with the toner voltage setpoints for each stage of the step wedge. The toner voltage set points are those specified by the manufacturer in the electrostatic image forming apparatus specifications.

Die gemessenen Tonerspannungswerte zeigen die Tonerdichte an. Eine zu hoher gemessener Tonerspannungswert weist darauf hin, dass der Tonerauftrag zu stark ist. Ein zu niedriger gemessener Tonerspannungswert weist darauf hin, dass der Tonerauftrag zu schwach ist. In beiden FƤllen lƤsst sich der Tonerauftrag einstellen und neu prĆ¼fen, bis die gemessenen Tonerspannungswerte der Tonersollspannung entsprechen oder innerhalb eines akzeptabeln Bereichs der Tonersollspannung liegen.The measured toner voltage values indicate the toner density. Too high a measured toner voltage value indicates that the toner application is too strong. If the toner tension value is too low, it indicates that the toner application is too weak. In either case, the toner application can be adjusted and rechecked until the measured toner voltage values are equal to the toner target voltage or within an acceptable range of the toner target voltage.

Vorzugsweise wird jedes Bildfeld des Fotoleiters nacheinander bewertet. Wenn jedes Bildfeld auf dem Fotoleiter bewertet worden ist, ist der mittlere gemessene Tonerspannungswert fĆ¼r die Stufe auf den Stufenkeil Ć¼ber eine ganze Umdrehung des Fotoleiters reprƤsentativ.Preferably, each image field of the photoconductor is evaluated successively. When each image field on the photoconductor has been evaluated, the average measured toner voltage value for the step on the step wedge over a full rotation of the photoconductor is representative.

Die vorliegende Erfindung bewertet quantitativ die BildqualitƤt einer elektrofotografischen Bilderzeugungsvorrichtung mit Hilfe eines Referenzsystems, um eine Tonerdichtedarstellung des Toners auf der OberflƤche des Fotoleiters zu erzeugen. Die tatsƤchlichen oder gemessenen Tonerdichten werden mit Solldichten gemƤƟ den technischen Daten des Herstellers verglichen, und zwar unabhƤngig von den subjektiven SichtprĆ¼fungen und Vergleichen des Benutzers. Die Dichtewerte des Toners zeigen die BildqualitƤt in einem elektrofotografischen Prozess an.The present invention quantitatively assesses the image quality of an electrophotographic image forming apparatus by means of a reference system to produce a toner density representation of the toner on the surface of the photoconductor. The actual or measured toner densities are compared to nominal densities according to the manufacturer's specifications, regardless of the user's subjective visual checks and comparisons. The density values of the toner indicate the image quality in an electrophotographic process.

Weitere Vorteile der Erfindung sind den folgenden Zeichnungen sowie der Beschreibung zu entnehmen.Further advantages of the invention will become apparent from the following drawings and the description.

Die Erfindung wird im folgenden anhand eines in den Zeichnungen dargestellten AusfĆ¼hrungsbeispiels nƤher erlƤutert. Es zeigen:

Fig. 1
eine schematische Darstellung einer erfindungsgemƤƟen elektrofotografischen Bilderzeugungsvorrichtung;
Fig. 2
einen Stufenkeil fĆ¼r eine erfindungsgemƤƟe elektrofotografische Bilderzeugungsvorrichtung;
Fig. 3
ein Ausgabediagramm mit einem exemplarischen Vergleich der Soll- und Messwerte fĆ¼r die Tonerspannung gemƤƟ der vorliegenden Erfindung; und
Fig. 4
ein Ablaufdiagramm zur Darstellung eines erfindungsgemƤƟen Verfahrens zur Online-Bewertung der BildqualitƤt.
The invention will be explained in more detail below with reference to an embodiment shown in the drawings. Show it:
Fig. 1
a schematic representation of an electrophotographic image forming apparatus according to the invention;
Fig. 2
a step wedge for an electrophotographic image forming apparatus of the present invention;
Fig. 3
an output diagram with an exemplary comparison of the setpoint and measured values for the toner voltage according to the present invention; and
Fig. 4
a flowchart for illustrating a method according to the invention for online evaluation of image quality.

Fig. 1 zeigt eine schematische Darstellung einer elektrofotografischen Bilderzeugungsvorrichtung 100 gemƤƟ einem AusfĆ¼hrungsbeispiel der Erfindung. Die elektrofotografische Bilderzeugungsvorrichtung 100 umfasst einen Fotoleiter 105, der auf Tragwalzen 110 sowie einem Motor 115 angeordnet ist, der den Fotoleiter 105 in die mit Pfeil A bezeichnete Richtung bewegt. Die elektrofotografische Bilderzeugungsvorrichtung 100 umfasst zudem einen primƤren Lader 118, eine Belichtungsvorrichtung 120, eine Tonerstation 125, einen Ɯbertragungslader 130, eine Fixierstation 140 sowie einen Reiniger 150, die in Wirkbeziehung um den Fotoleiter 105 herum angeordnet sind. Der Fotoleiter 105 umfasst zwar eine walzengelagerte Bandkonfiguration, aber er kann auch in anderer Weise durch Verwendung einer Trommel oder anderer geeigneter Konfigurationen gehaltert sein. Zwar wird fĆ¼r die elektrofotografische Bilderzeugungsvorrichtung 100 eine bestimmte Konfiguration und Anordnung gezeigt, aber die Erfindung kann andere Konfigurationen und Anordnungen verwenden, u.a. Anordnungen mit zusƤtzlichen Komponenten.Fig. 1 shows a schematic representation of an electrophotographic image forming apparatus 100 according to an embodiment of the invention. The electrophotographic image forming apparatus 100 includes a photoconductor 105 disposed on support rollers 110 and a motor 115 that moves the photoconductor 105 in the direction indicated by arrow A. The electrophotographic image forming apparatus 100 further includes a primary charger 118, an exposure apparatus 120, a toner station 125, a transfer charger 130, a fixing station 140, and a cleaner 150 operatively disposed around the photoconductor 105. Although the photoconductor 105 includes a roller-mounted ribbon configuration, it may be otherwise supported by use of a drum or other suitable configurations. While a particular configuration and arrangement is shown for the electrophotographic imaging apparatus 100, the invention may employ other configurations and arrangements, including but not limited to those described with reference to FIGS. Arrangements with additional components.

Die elektrofotografische Bilderzeugungsvorrichtung 100 umfasst zudem ein Densitometer 160, das mit einem Lichtemitter 165 sowie einen Lichtkollektor 170 verbunden ist. Das Densitometer 160 ist mit einem Mikroprozessor 175 verbunden, der mit einem Speicher 180 ausgestattet ist. Der Mikroprozessor 175 ist mit einer Eingabeschnittstelle 185 und mit einer Ausgabeschnittstelle 190 verbunden. Der Mikroprozessor 175 kann zur Kommunikation mit anderen Mikroprozessoren in der elektrofotografischen Bilderzeugungsvorrichtung 100 verbunden sein. Die Eingabeschnittstelle 185 kann eine Tastatur, ein berĆ¼hrungsempfindlicher Bildschirm oder Ƥhnliches sein. Die Ausgabeschnittstelle 190 kann ein Drucker, ein Bildschirm oder Ƥhnliches sein. Bei der Ein- und Ausgabeschnittstelle 185, 190 kann es sich um dieselbe Komponente handeln. Es kann eine Mehrzahl von Densitometern oder anderen Komponenten vorhanden sein.The electrophotographic image forming apparatus 100 further includes a densitometer 160 connected to a light emitter 165 and a light collector 170. The densitometer 160 is connected to a microprocessor 175 equipped with a memory 180. The microprocessor 175 is connected to an input interface 185 and to an output interface 190. The microprocessor 175 may be connected for communication with other microprocessors in the electrophotographic imaging apparatus 100. The input interface 185 may be a keyboard, a touch screen, or the like. The output interface 190 may be a printer, a monitor, or the like. The input and output interface 185, 190 may be the same component. There may be a plurality of densitometers or other components.

Nach einem Aspekt der vorliegenden Erfindung wird eine Tonerdichtedarstellung des gesamten Fotoleiters 105 erzeugt. Die elektrofotografische Bilderzeugungsvorrichtung 100 umfasst ein Referenzsystem nicht gezeigt zum Auffinden von Positionen auf der OberflƤche des Fotoleiters 105. Das Referenzsystem nutzt einen (nicht gezeigten) Referenzpunkt auf dem Fotoleiter 105 sowie eine (nicht gezeigte) Folgeeinrichtung, um Lagestellen in Bezug zum Referenzpunkt entlang der LƤnge und des Umfangs des Fotoleiters 105 zu ermitteln. Bei einem als Band ausgebildeten Fotoleiter ist der Referenzpunkt vorzugsweise eine Naht. Als Referenzpunkt ist das Prozessfeld oder ein anderer fester Punkt auf dem Fotoleiter verwendbar. Die Folgeeinrichtung ist im wesentlichen ein Timer, der dem Fotoleiter 105 anzeigt, wann von dem Referenzpunkt zu einer bestimmte Lagestelle fortzufahren ist. Durch Kenntnis der Strecke, die der Fotoleiter 105 innerhalb der gemessenen Zeit zurĆ¼cklegt, lƤsst sich die Lagestelle auf dem Fotoleiter 105 bestimmen. Die Folgeeinrichtung kann auch eine andere Messeinrichtung sein und die Lagestelle durch andere Mittel bestimmen. Alternative Referenzsysteme sind ebenfalls verwendbar.According to one aspect of the present invention, a toner density representation of the entire photoconductor 105 is generated. The electrophotographic image forming apparatus 100 includes a reference system not shown for finding positions on the surface of the photoconductor 105. The reference system utilizes a reference point (not shown) on the photoconductor 105 Photoconductor 105 and a follower (not shown) to determine positions relative to the reference point along the length and the circumference of the photoconductor 105. In the case of a photoconductor designed as a band, the reference point is preferably a seam. As a reference point, the process field or another fixed point on the photoconductor can be used. The follower is essentially a timer that indicates to the photoconductor 105 when to proceed from the reference point to a particular location. By knowing the distance the photoconductor 105 travels within the measured time, the location on the photoconductor 105 can be determined. The follower can also be another measuring device and determine the location by other means. Alternative reference systems are also usable.

Das Referenzsystem dient dazu, die Lagestellen fĆ¼r die Dichtemessungen zu bezeichnen. FĆ¼r jede erfolgte Dichtemessung wird eine Referenzposition festgehalten. Auf diese Weise und wie nachfolgend beschrieben, kann ein Dichtewert des Fotoleiters von dem kombinierten Dichtewert des Fotoleiters und des Toners an derselben Lagestelle subtrahiert werden, um so die gemessene Tonerdichte fĆ¼r diese Lagestelle zu ermitteln. Die gemessenen Tonerdichten fĆ¼r verschiedene Lagestellen lassen sich zusammenfĆ¼hren, um eine Dichtedarstellung des auf dem Fotoleiter 105 aufgetragenen Toners zu erzeugen.The reference system is used to designate the locations for the density measurements. For each density measurement made, a reference position is recorded. In this way, and as described below, a density value of the photoconductor may be subtracted from the combined density value of the photoconductor and the toner at the same location so as to determine the measured toner density for that location. The measured toner densities for various locations can be combined to produce a density representation of the toner deposited on the photoconductor 105.

Bei Gebrauch lƤdt der primƤre Lader 118 ein Bildfeld auf der OberflƤche des Fotoleiters 105 elektrostatisch auf. Das Bildfeld entspricht der GrĆ¶ĆŸe des auszubildenden Bildes und kann die gesamte FlƤche des Fotoleiters 105 bedecken. Vorzugsweise ist der Fotoleiter 105 zur Aufnahme mehrerer Bildfelder ausgelegt.In use, the primary charger 118 electrostatically charges an image field on the surface of the photoconductor 105. The image field corresponds to the size of the image to be formed and can cover the entire surface of the photoconductor 105. Preferably, the photoconductor 105 is designed to receive a plurality of image fields.

Der Fotoleiter 105 dreht sich, um das geladene Bildfeld an der Belichtungsvorrichtung 120 vorbeizufĆ¼hren. Die Belichtungsvorrichtung 120 belichtet das geladene Bildfeld optisch, um ein elektrostatisches Latentbild auf dem Fotoleiter 105 zu erzeugen.The photoconductor 105 rotates to pass the charged image field past the exposure apparatus 120. The exposure device 120 optically exposes the charged image field to produce an electrostatic latent image on the photoconductor 105.

Der Fotoleiter 105 dreht sich, um das elektrostatische Bild an der Tonerstation 125 vorbeizufĆ¼hren. Die Tonerstation 125 lagert auf der OberflƤche des Fotoleiters 105 Toner oder ein anderes Entwicklungsmaterial ab. Der Toner ist derart geladen, dass er an dem elektrostatischen Bild haftet. Die Beschreibung bezieht sich zwar auf einen Trockentoner, aber es ist auch ein flĆ¼ssiges oder ein Ƥhnliches, geeignetes Entwicklungsmaterial verwendbar.The photoconductor 105 rotates to pass the electrostatic image at the toning station 125. The toning station 125 deposits on the surface of the photoconductor 105 toner or other developing material. The toner is charged so that it is at the electrostatic image adheres. Although the description refers to a dry toner, it is also usable as a liquid or the like suitable developing material.

Der Fotoleiter 105 dreht sich, um das elektrostatische Bild an dem Ɯbertragungslader 130 vorbeizufĆ¼hren. Der Ɯbertragungslader 130 Ć¼bertrƤgt das elektrostatische Tonerbild von dem Fotoleiter 105 auf Papier oder auf ein anderes, zur Aufnahme des Bildes ausgewƤhltes Medium. Das Papier S wird dem Papiervorrat (135) entnommen und tritt zwischen dem Ɯbertragungslader 130 und dem Fotoleiter 105 hindurch. Das Papier S wird dann durch die Fixierstation 140, wo der Toner auf dem Papier fixiert wird, gefĆ¼hrt.The photoconductor 105 rotates to pass the electrostatic image past the transfer charger 130. The transfer charger 130 transfers the electrostatic toner image from the photoconductor 105 to paper or other medium selected to receive the image. The paper S is removed from the paper supply (135) and passes between the transfer charger 130 and the photoconductor 105. The paper S is then passed through the fuser 140 where the toner is fixed on the paper.

Der Fotoleiter 105 dreht sich, um das Bildfeld durch den Reiniger 150 zu fĆ¼hren. Der Reiniger entfernt jegliche Toner- und Ladungsreste und bereitet den Fotoleiter somit fĆ¼r ein weiteres Bild auf. Zwar sind diese ArbeitsgƤnge in Schritten beschrieben, aber sie erfolgen vorzugsweise nacheinander und fortlaufend, wƤhrend der Fotoleiter einen Zyklus durchlƤuft.The photoconductor 105 rotates to pass the image field through the cleaner 150. The cleaner removes any toner and charge residues and thus prepares the photoconductor for another image. Although these operations are described in steps, they are preferably sequential and continuous as the photoconductor goes through one cycle.

Das Densitometer 160 ist mit dem Lichtemitter 165 und dem Lichtkollektor 170 verbunden. Der Lichtemitter 165 und der Lichtkollektor 170 sind auf beiden Seiten des Fotoleiters 105 sich gegenĆ¼berliegend angeordnet, und zwar nachfolgend der Tonerstation 125, also der Position, an der Toner aufgebracht wird. Vorzugsweise ist der Lichtemitter 165 gegenĆ¼ber der OberflƤche angeordnet, wo der Toner aufgetragen wird.The densitometer 160 is connected to the light emitter 165 and the light collector 170. The light emitter 165 and the light collector 170 are disposed on both sides of the photoconductor 105 opposite to each other, following the toner station 125, that is, the position where toner is applied. Preferably, the light emitter 165 is disposed opposite the surface where the toner is applied.

Das Densitometer 160 wird vorzugsweise als ein Durchlichtdensitometer dargestellt. Allerdings ist auch ein Auflichtdensitometer sowie jede andere Dichtemesseinrichtung zum Messen der Tonerdichten auf dem Fotoleiter 105 verwendbar. Bei Verwendung eines Auflichtdensitometers mĆ¼ssen die Positionen des Lichtemitters 165 und des Lichtkollektors 170 entsprechend geƤndert werden. Der Lichtemitter 165 sowie der Lichtkollektor 170 sind nicht zwingend Bestandteile der Dichtemesseinrichtung.The densitometer 160 is preferably shown as a transmitted light densitometer. However, an incident densitometer as well as any other density measuring device for measuring the toner densities on the photoconductor 105 is also usable. When using an incident light densitometer, the positions of the light emitter 165 and the light collector 170 must be changed accordingly. The light emitter 165 and the light collector 170 are not necessarily components of the density measuring device.

Der Strahlengang vom Lichtemitter 165 zum Lichtkollektor 170 tritt durch den Fotoleiter 105. Das Densitometer 160 erzeugt Spannungswerte proportional zur Lichtabsorption im Strahlengang. Die Spannungswerte zeigen die Dichte des Fotoleiters 105 und/oder des auf der OberflƤche befindlichen Toners an. Die Spannungswerte des Densitometers 160 steigen mit zunehmender OpazitƤt des Fotoleiters 105 an, also je grĆ¶ĆŸer der Tonerauftrag auf dem Fotoleiter 105 ist. Um durch den Fotoleiter 105 bedingte Schwankungen auszuschlieƟen, kann man die Spannungswerte des Fotoleiters ohne Tonerauftrag von den Spannungswerten des Fotoleiters mit ToneraĆ¼ftrag abziehen. Das Densitometer 160 Ć¼bergibt die Spannungswerte an den Mikroprozessor 175.The beam path from the light emitter 165 to the light collector 170 passes through the photoconductor 105. The densitometer 160 generates voltage values proportional to the light absorption in the beam path. The voltage values indicate the density of the photoconductor 105 and / or the toner on the surface. The voltage values of the densitometer 160 increase with increasing opacity of the photoconductor 105, that is, the greater the toner application on the photoconductor 105. In order to exclude fluctuations caused by the photoconductor 105, it is possible to subtract the voltage values of the photoconductor without toner application from the voltage values of the photoconductor with the toner charge. The densitometer 160 passes the voltage values to the microprocessor 175.

Der Mikroprozessor 175 Ć¼bergibt die Spannungswerte an die Ausgabeschnittstelle 190. Die Spannungswerte lassen sich zur weiteren Analyse und/oder spƤteren Ɯbertragung an die Ausgabeschnittstelle im Speicher 180 ablegen. Die Spannungswerte kƶnnen in der vom Densitometer 160 enthaltenen Form Ć¼bertragen oder verstƤrkt oder auf sonstige Weise aufbereitet werden, um die Ɯbertragung zur Ausgabeschnittstelle 190 zu verbessern. Der Mikroprozessor 175 kann die Spannungswerte in andere geeignete Faktoren umsetzen, etwa Dichte, Dicke usw. Zudem empfƤngt der Mikroprozessor 175 Befehle und Anweisungen Ć¼ber die Eingabeschnittstelle 185.The microprocessor 175 transfers the voltage values to the output interface 190. The voltage values can be stored in the memory 180 for further analysis and / or subsequent transmission to the output interface. The voltage values may be transmitted or amplified in the form included in the densitometer 160 or otherwise conditioned to enhance transmission to the output interface 190. The microprocessor 175 may translate the voltage values into other suitable factors, such as density, thickness, etc. In addition, the microprocessor 175 receives commands and instructions via the input interface 185.

In der vorliegenden Erfindung bewertet die elektrofotografische Bilderzeugungsvorrichtung 100 den elektrofotografischen Prozess, um zu ermitteln, ob die Tonerdichte und somit die BildqualitƤt den Spezifikationen des Herstellers entspricht. Die elektrofotografische Bilderzeugungsvorrichtung 100 prĆ¼ft, ob die Dichte des Toners auf dem Fotoleiter 105 der Dichte entspricht, die fĆ¼r den spezifikationsgemƤƟen Tonwertumfang erforderlich ist. In einem Graustufen-Tonwiedergabeprozess verƤndern sich die Tonerdichten schrittweise. In diesem Fall werden die Tonerdichten der verschiedenen Stufen bewertet.In the present invention, the electrophotographic image forming apparatus 100 evaluates the electrophotographic process to determine whether the toner density and thus the image quality conform to the specifications of the manufacturer. The electrophotographic image forming apparatus 100 checks whether the density of the toner on the photoconductor 105 corresponds to the density required for the tonal range specified by the specification. In a grayscale sound reproduction process, the toner densities gradually change. In this case, the toner densities of the various stages are evaluated.

Fig. 2 zeigt einen Stufenkeil 200 zum Bewerten der verschiedenen Tonerdichten in einem Graustufen-Tonwiedergabesystem. Der Stufenkeil 200 ist ein Bild mit abgestuften Grauwerten entsprechend der Stufen der Tonerdichte, die einer bestimmten, elektrofotografischen Bilderzeugungsvorrichtung zugeordnet sind. Beispielsweise weist der Stufenkeil aus Fig. 2 insgesamt 16 Stufen auf, die von Stufe 210 (keine Belichtung und kein Tonerauftrag) bis Stufe 220 (maximale Belichtung und maximaler Tonerauftrag) reichen.Fig. 2 shows a step wedge 200 for evaluating the various toner densities in a grayscale sound reproduction system. Staged wedge 200 is an image with graded gray levels corresponding to the levels of toner density associated with a particular associated with electrophotographic image forming apparatus. For example, the step wedge of Figure 2 has a total of 16 stages, ranging from stage 210 (no exposure and no toner application) to stage 220 (maximum exposure and maximum toner application).

Um den elektrofotografischen Prozess zu bewerten, druckt die elektrofotografische Bilderzeugungsvorrichtung 100 mindestens ein Bild des Stufenkeils. Vorzugsweise entspricht die Anzahl von Bildern der Anzahl von Bildfeldern, die auf die LƤnge oder den Umfang des Fotoleiters passen. Wenn mehr als ein Bild zu drucken ist, werden die Bilder nacheinander gedruckt. Indem eine Anzahl von Bildern, die der Anzahl von Bildfeldern auf dem Fotoleiter entspricht, nacheinander gedruckt wird, lƤsst sich die gesamte OberflƤche des Fotoleiters bewerten. Vorzugsweise werden sechs Bildfelder auf dem Fotoleiter 105 bereitgestellt. Dementsprechend druckt die elektrofotografische Bilderzeugungsvorrichtung 100 sechs aufeinanderfolgende Bilder, um den elektrofotografischen Prozess zu bewerten. DarĆ¼ber hinaus befindet sich auf dem Fotoleiter 105 ein (nicht gezeigtes) Prozessfeld, das zwischen den Bildfeldern angeordnet ist. Das Prozessfeld wird mit der maximalen Tonerdichte, Dmax, belichtet oder mit jeder Reindichte.In order to evaluate the electrophotographic process, the electrophotographic image forming apparatus 100 prints at least one image of the step wedge. Preferably, the number of images corresponds to the number of image fields that match the length or circumference of the photoconductor. If more than one image is to be printed, the images are printed one after another. By successively printing a number of images corresponding to the number of image frames on the photoconductor, the entire surface of the photoconductor can be evaluated. Preferably, six frames are provided on the photoconductor 105. Accordingly, the electrophotographic image forming apparatus 100 prints six consecutive images to evaluate the electrophotographic process. In addition, located on the photoconductor 105, a (not shown) process field, which is arranged between the image fields. The process panel is exposed with the maximum toner density, D max , or with each true density.

Ein Ausdruck durch die elektrofotografische Bilderzeugungsvorrichtung 100 ist nicht erforderlich, solange Toner auf dem Fotoleiter 105 aufgetragen wird. Allerdings steht die Druckausgabe im Zusammenhang mit dem Betrieb der elektrofotografischen Bilderzeugungsvorrichtung 100. Die gedruckten Bilder ermƶglichen eine visuelle Beurteilung und Offline-Messung der Druckdichte mit kommerziell verfĆ¼gbaren HelligkeitsmessgerƤten und Densitometern. Zudem ist es einem Benutzer oder Servicetechniker anhand der Druckausgabe mƶglich, andere BildqualitƤtsprobleme zu erkennen, die nicht mit der Tonerdichte im Zusammenhang stehen, beispielsweise Kratzer auf dem Fotoleiter sowie mechanische oder elektrische Probleme im Entwicklungsprozess.Expression by the electrophotographic image forming apparatus 100 is not required as long as toner is applied to the photoconductor 105. However, the printed output is related to the operation of the electrophotographic image forming apparatus 100. The printed images enable visual assessment and off-line measurement of print density with commercially available brightness meters and densitometers. In addition, it is possible for a user or service technician to recognize other image quality issues other than toner density, such as scratches on the photoconductor and mechanical or electrical issues in the development process, from the printed output.

Die Stufen des Stufenkeils entsprechen den Stufenbereichen auf dem Bildfeld. Jedem der Stufenbereiche ist eine bestimmte Lagestelle zugewiesen, wie anhand des Referenzsystems bestimmt. WƤhrend der Druckvorgang lƤuft, fĆ¼hrt das Densitometer 160 mindestens eine Dichtemessung jedes Stufenbereichs von jedem Bildfeld durch.The steps of the step wedge correspond to the step areas on the image field. Each of the step areas is assigned a specific location, as in the reference system certainly. As the printing process proceeds, the densitometer 160 performs at least one density measurement of each step area of each image field.

Zur Ermittlung des Dichtewerts wird die Spannung gemessen, wƤhrend der Lichtemitter 165 Licht durch den Toner und den Fotoleiter 105 auf den Lichtkollektor 170 wirft. Bessere Messergebnisse lassen sich durch Verbessern des Signal-StƶrverhƤltnisses fĆ¼r jede Stufe erzielen. Vorzugsweise deckt der Strahlengang 1,27 cm der OberflƤche des Fotoleiters ab. Vorzugsweise werden fĆ¼r jeden Stufenbereich in jedem Bildfeld mindestens fĆ¼nf Dichte- oder Spannungsmessungen vorgenommen. Die fĆ¼nf Messungen werden an fĆ¼nf verschiedenen Lagestellen des Fotoleiters durchgefĆ¼hrt, alle jedoch innerhalb desselben Stufenbereichs. Durch mehr Messungen erhƶht sich die Genauigkeit der endgĆ¼ltigen Spannungs-/Dichtemesswerte. Diese Spannungswerte zeigen die optischen Eigenschaften an, d.h. die Dichte des mit Toner beaufschlagten Fotoleiters 105. Die kombinierten Spannungswerte werden von dem Mikroprozessor 175 getrennt im Speicher 180 abgelegt.For determining the density value, the voltage is measured while the light emitter 165 throws light through the toner and the photoconductor 105 onto the light collector 170. Better measurement results can be achieved by improving the signal-to-noise ratio for each stage. Preferably, the beam path covers 1.27 cm of the surface of the photoconductor. Preferably, at least five density or voltage measurements are made for each step area in each frame. The five measurements are taken at five different positions of the photoconductor, but all within the same step range. More measurements increase the accuracy of the final voltage / density readings. These voltage values indicate the optical properties, i. the density of the photoconductive photoconductor 105. The combined voltage values are stored separately in the memory 180 by the microprocessor 175.

Um durch den Fotoleiter 105 bedingte Schwankungen auszuschlieƟen, werden die Dichtemessungen auch durchgefĆ¼hrt, ohne dass Toner auf dem Fotoleiter 105 aufgetragen ist. Diese Dichtemessungen werden vorzugsweise vor den Dichtemessungen mit aufgetragenem Toner durchgefĆ¼hrt. Mit Hilfe des Referenzsystems lƤsst sich die Fotoleiterdichte fĆ¼r jeden Stufenbereich ermitteln sowie nachfolgende Dichtemesswerte von Fotoleiter und Toner.In order to eliminate fluctuations caused by the photoconductor 105, the density measurements are also carried out without toner being applied to the photoconductor 105. These density measurements are preferably performed before the densities with toner applied. The reference system can be used to determine the photoconductor density for each step range, as well as subsequent densities of photoconductor and toner.

Beispielsweise werden sechs aufeinanderfolgende Bilder von dem Stufenkeil herangezogen. Die Tonerstation wird vorĆ¼bergehend deaktiviert. Die sechs Bilder stellen eine Drehung des Fotoleiters 105 dar. Da kein Toner aufgetragen ist, kann ein leeres oder Ƥhnliches Bild verwendet werden, solange diese Spannungswerte fĆ¼r den Fotoleiter den Stufenbereichen auf dem Bildfeld entsprechen, in denen die Stufenkeilmessungen ohne Toner vorgenommen werden.For example, six consecutive images are taken from the step wedge. The toner station will be temporarily disabled. The six images represent rotation of the photoconductor 105. Since toner is not applied, an empty or similar image may be used as long as these photoconductor voltage values correspond to the step areas on the image field where the step wedge measurements are made without toner.

Das Densitometer fĆ¼hrt mindestens eine und vorzugsweise fĆ¼nf Fotoleiterspannungsmessungen fĆ¼r jeden Stufenbereich in jedem Bildfeld durch. Die fĆ¼nf Messungen werden an fĆ¼nf verschiedenen Lagestellen des Fotoleiters durchgefĆ¼hrt, alle jedoch innerhalb desselben Stufenbereichs. Das Referenzsystem bestimmt die Lagestellen der Fotoleiterspannungswerte, so dass die Spannungsmessungen fĆ¼r Toner und Fotoleiter an denselben Lagestellen vorgenommen werden. Das Prozessfeld wird gemessen, um einen Spannungswert des Fotoleiters zu erhalten. Die Fotoleiterspannungswerte entsprechen den optischen Eigenschaften des Fotoleiters 105 , d.h. seiner Dichte. Die Fotoleiterspannungswerte werden im Speicher 180 abgelegt.The densitometer performs at least one and preferably five photoconductor voltage measurements for each step area in each frame. The five measurements are taken at five different positions of the photoconductor, but all within the same step range. The reference system determines the locations of the photoconductor voltage values so that the voltage measurements for toner and photoconductor are made at the same locations. The process field is measured to obtain a voltage value of the photoconductor. The photoconductor voltage values correspond to the optical properties of the photoconductor 105, i. its density. The photoconductor voltage values are stored in memory 180.

Um die Tonerdichte in jeder Stufe des Stufenkeils zu ermitteln, wird der Fotoleiterspannungswert von dem entsprechenden, kombinierten Spannungswert in demselben Bildfeld subtrahiert (das Referenzsystem identifiziert die Spannungswerte fĆ¼r dieselbe Lagestelle). Das Ergebnis ist ein gemessener Tonerspannungswert fĆ¼r jede Stufe in jedem Bildfeld. Der gemessene Tonerspannungswert zeigt die Tonerdichte fĆ¼r den jeweiligen Stufenbereich des jeweiligen Bildfeldes an. Auf Ƥhnliche Weise wird der Tonerspannungswert fĆ¼r das Prozessfeld ermittelt, der die maximale Tonerdichte bezeichnet.To determine the toner density in each step of the step wedge, the photoconductor voltage value is subtracted from the corresponding combined voltage value in the same image field (the reference system identifies the voltage values for the same location). The result is a measured toner voltage value for each stage in each frame. The measured toner voltage value indicates the toner density for each step range of the respective image field. Similarly, the toner tension value for the process field, which is the maximum toner density, is determined.

Die gemessenen Tonerspannungswerte fĆ¼r einen bestimmten Stufenbereich in allen Bildfeldern werden gemittelt, um einen mittleren, gemessenen Tonerspannungswert fĆ¼r die jeweilige Stufe in dem Stufenkeil zu erhalten. Wenn beispielsweise fĆ¼nf Messungen der Tonerspannung fĆ¼r jede Stufe in jedem Bildfeld vorgenommen werden, und wenn es insgesamt sechs Bildfelder gibt, dann werden 30 gemessene Tonerspannungswerte gemittelt, um einen mittleren, gemessenen Tonerspannungswert fĆ¼r den Stufenbereich zu erhalten; dieser Wert bezeichnet die Tonerdichte fĆ¼r die jeweilige Stufe des Stufenkeils Ć¼ber eine vollstƤndige Drehung des Fotoleiters 105. Das Prozessfeld wird in gleicher Weise gemittelt, um den gemessenen Tonerspannungswert fĆ¼r die maximale Tonerdichte, Dmax, oder eine beliebige Reindichte zu erhalten. Die gemessenen Tonerspannungswerte entsprechen den optischen Eigenschaften des Toners und damit seiner Dichte.The measured toner voltage values for a given step range in all image fields are averaged to obtain a mean measured toner voltage value for the particular step in the step wedge. For example, if five measurements of the toner voltage are made for each stage in each frame and if there are a total of six panels, then 30 measured toner voltage values are averaged to obtain a mean measured toner voltage value for the stage area; this value indicates the toner density for the particular step of the step wedge over a full rotation of the photoconductor 105. The process field is likewise averaged to obtain the measured toner tension value for the maximum toner density, D max , or any pure density. The measured toner tension values correspond to the optical properties of the toner and thus its density.

Fig. 3 zeigt ein Beispiel einer Zusammenfassung eines typischen Ergebnisses von derartigen Mittelwerten Ć¼ber sechs aufeinander folgende Bildfelder fĆ¼r alle Stufen, einschlieƟlich des Prozessfeldes. GemƤƟ einem Aspekt der vorliegenden Erfindung werden die gedruckten Bildfelder nacheinander bewertet. Eine bildfeldweise Analyse auf der Grundlage eines Mittelwerts aus fĆ¼nf Messwerten pro Stufe kann ƶrtlich begrenzte Defekte in dem Fotoleiter ermitteln, die bewirken, dass die Dichte von einer oder mehreren Stufen nicht innerhalb des gewĆ¼nschten Sollwertbereichs liegt.Fig. 3 shows an example of a summary of a typical result of such averages over six consecutive frames for all stages, including the process field. According to one aspect of the present invention, the printed image fields are evaluated one after another. Field-by-frame analysis based on an average of five measurements per stage can determine localized defects in the photoconductor that cause the density of one or more stages not to fall within the desired setpoint range.

Der mittlere gemessene Tonerspannungswert fĆ¼r jede Stufe wird mit einem Tonerspannungssollwert fĆ¼r diese Stufe verglichen. Der Tonerspannungssollwert entspricht den Spezifikationen des Herstellers fĆ¼r die Tonerdichte. Die gemessenen Tonerspannungswerte zeigen die Tonerdichte an. Wenn der gemessene Tonerspannungswert grĆ¶ĆŸer als der Tonerspannungssollwert ist, wurde fĆ¼r diese Stufe in dem Stufenkeil zu viel Toner aufgetragen. Wenn der gemessene Tonerspannungswert kleiner als der Tonerspannungssollwert ist, wurde fĆ¼r diese Stufe in dem Stufenkeil zu wenig Toner aufgetragen. In beiden FƤllen lƤsst sich der Tonerauftrag einstellen und neu prĆ¼fen, bis die gemessenen Tonerspannungswerte dem Tonerspannungssollwert entsprechen oder innerhalb eines akzeptabeln Bereichs des Tonerspannungssollwerts liegen.The average measured toner voltage value for each stage is compared to a toner voltage setpoint for that stage. The toner voltage set point is the manufacturer's specifications for toner density. The measured toner voltage values indicate the toner density. If the measured toner tension value is greater than the toner tension set point, too much toner has been applied to the step in the step wedge. If the measured toner tension value is less than the toner tension setpoint, too little toner has been applied to that stage in the step wedge. In both cases, the toner application can be adjusted and retested until the measured toner voltage values are within the toner voltage setpoint or within an acceptable range of the toner voltage setpoint.

Der Mikroprozessor 175 Ć¼bergibt die gemessenen Tonerspannungswerte an die Ausgabeschnittstelle 190. Die gemessenen Tonerspannungswerte kƶnnen in Form einer Tabelle, wie die in Fig. 3 gezeigte, dargestellt werden, um die gemessenen Tonerspannungswerte mit den Tonerspannungssollwerten zu vergleichen. Die gemessenen Tonerspannungswerte lassen sich im Speicher 180 ablegen, um historische PrĆ¼fdaten bereitzustellen, oder sie kƶnnen auf eine (nicht gezeigte) Datenspeichereinrichtung heruntergeladen werden.The microprocessor 175 provides the measured toner voltage values to the output interface 190. The measured toner voltage values may be presented in the form of a table, such as that shown in Figure 3, to compare the measured toner voltage values to the toner voltage setpoints. The measured toner voltage values may be stored in memory 180 to provide historical test data, or may be downloaded to a data storage device (not shown).

Die Bewertung des elektrofotografischen Prozesses lƤsst sich als eigenstƤndige Diagnoseroutine oder als Teil einer grĆ¶ĆŸeren Diagnoseroutine durchfĆ¼hren. Benutzer und Servicetechniker kƶnnen die Bewertung Ć¼ber die Eingabeschnittstelle 185 vornehmen. Die Bewertung lƤsst sich auch als Teil einer Fehlererkennungsroutine durchfĆ¼hren, bei der ein Warnsignal an den Benutzer ausgegeben wird, wenn zwischen den gemessenen Tonerspannungswerten und den Tonerspannungssollwerten Abweichungen festgestellt werden.The evaluation of the electrophotographic process can be performed as a stand-alone diagnostic routine or as part of a larger diagnostic routine. Users and service technicians may assess via input interface 185. The Judgment may also be performed as part of an error detection routine in which a warning signal is output to the user when deviations are detected between the measured toner voltage values and the toner voltage setpoints.

Fig. 4 zeigt ein Ablaufdiagramm des erfindungsgemƤƟen Verfahrens zur Online-Bewertung der BildqualitƤt einer elektrofotografischen Bilderzeugungsvorrichtung. In Schritt 410 wird ein Bildfeld auf einem Fotoleiter zum ersten Mal geladen. Der Fotoleiter kann einen Gurt und eine Walze, eine Trommel oder eine andere geeignete Konfiguration umfassen.4 shows a flowchart of the method according to the invention for the online evaluation of the image quality of an electrophotographic image-forming device. In step 410, an image field on a photoconductor is loaded for the first time. The photoconductor may comprise a belt and a roller, a drum or other suitable configuration.

In Schritt 420 wird ein Stufenkeil oder ein Testbild optisch belichtet, um auf dem Bildfeld zum ersten Mal ein elektrostatisches Bild auszubilden. Vorzugsweise ist der Stufenkeil auf die Graustufenwiedergabe ausgelegt und umfasst 16 Dichtestufen. Das elektrostatische Bild weist Stufenbereiche auf, die den Stufen des Stufenkeils entsprechen. Das Prozessfeld wird auf Ƥhnliche Weise belichtet. Die Tonerstation wird deaktiviert, um den Fotoleiter nicht mit Toner zu beaufschlagen.In step 420, a step wedge or test image is optically exposed to form an electrostatic image on the image field for the first time. Preferably, the step wedge is designed for grayscale reproduction and comprises 16 density levels. The electrostatic image has step portions corresponding to the steps of the step wedge. The process field is exposed in a similar way. The toner station is disabled to avoid toner on the photoconductor.

In Schritt 430 wird fĆ¼r jeden Stufenbereich des Stufenkeils auf dem Bildfeld die Fotoleiterdichte ermittelt. Vorzugsweise werden fĆ¼nf Fotoleiterdichtemessungen von jedem Stufenbereich mit Hilfe eines Durchlichtdensitometers durchgefĆ¼hrt, welches einen Lichtemitter und einen Lichtkollektor umfasst, die in Wirkbeziehung benachbart zum Fotoleiter angeordnet sind. Das Densitometer misst die Dichte als Spannungswert entsprechend der Menge der Lichtenergie, die durch den Fotoleiter auf einem Strahlengang zwischen Lichtemitter und Lichtkollektor tritt. Die Messung der Fotoleiterspannungen des Prozessfeldes werden auf Ƥhnliche Weise durchgefĆ¼hrt. Die Spannungswerte des Fotoleiters werden im Speicher getrennt abgelegt, wobei jeder Fotoleiter-Spannungswert in Bezug auf dessen Lage auf dem Fotoleiter bestimmt ist. Anstelle des Densitometers sind auch andere Dichtemesseinrichtungen verwendbar. Die Ɯbertragungsstation und die Fixiereinrichtung werden deaktiviert, um eine Beaufschlagung des Fotoleiters zu vermeiden. Der Reiniger entfernt jegliche Ladung vom Fotoleiter.In step 430, the photoconductor density is determined for each step area of the step wedge on the image field. Preferably, five photoconductor density measurements are made from each stage region by means of a transmitted light densitometer comprising a light emitter and a light collector operatively disposed adjacent to the photoconductor. The densitometer measures the density as a voltage value corresponding to the amount of light energy that passes through the photoconductor on a beam path between the light emitter and light collector. The measurement of the photoconductor voltages of the process field are carried out in a similar way. The voltage values of the photoconductor are stored separately in the memory, each photoconductor voltage value being determined in relation to its position on the photoconductor. Instead of the densitometer, other density measuring devices can be used. The transfer station and the fixing device are deactivated to prevent exposure of the photoconductor. The cleaner removes any charge from the photoconductor.

In Schritt 440 wird das Bildfeld ein zweites Mal geladen.In step 440, the image field is loaded a second time.

In Schritt 450 wird der Stufenkeil oder das Testbild optisch belichtet, um auf dem Bildfeld zum zweiten Mal ein elektrostatisches Bild auszubilden. Wie in Schritt 420 weist das elektrostatische Bild Stufenbereiche auf, die den Stufen des Stufenkeils entsprechen. Die Stufenbereiche in Schritt 450 sind die gleichen wie die Stufenbereiche in Schritt 420.In step 450, the step wedge or test image is optically exposed to form an electrostatic image on the image field for the second time. As in step 420, the electrostatic image has step areas corresponding to the steps of the step wedge. The step areas in step 450 are the same as the step areas in step 420.

In Schritt 460 wird die Tonerstation aktiviert, um Toner auf das Bildfeld aufzutragen. Der Toner bildet ein Tonerbild aus, das dem elektrostatischen Bild entspricht, welches wiederum dem Stufenkeil entspricht. Auch auf das Prozessfeld wird Toner aufgetragen.In step 460, the toning station is activated to apply toner to the image field. The toner forms a toner image corresponding to the electrostatic image, which in turn corresponds to the step wedge. Toner is also applied to the process field.

In Schritt 470 wird fĆ¼r jeden Stufenbereich des Stufenkeils auf dem Bildfeld die Fotoleiter- und die Tonerdichte ermittelt. Vorzugsweise werden fĆ¼nf Dichtemessungen von jedem Stufenbereich mit Hilfe des Durchlichtdensitometers auf Ƥhnliche Weise wie in Schritt 430 vorgenommen. Das Densitometer misst die Dichte als Spannungswert entsprechend der Menge der Lichtenergie, die durch den Fotoleiter und den Toner auf einem Strahlengang zwischen Lichtemitter und Lichtkollektor tritt. Die kombinierten Spannungswerte werden im Speicher getrennt abgelegt, wobei jeder kombinierte Spannungswert wieder in Bezug auf dessen Lage auf dem Fotoleiter bestimmt ist.In step 470, the photoconductor and toner densities are determined for each step area of the step wedge on the image field. Preferably, five density measurements of each step range are made by means of the transmitted light densitometer in a manner similar to step 430. The densitometer measures the density as a voltage value corresponding to the amount of light energy passing through the photoconductor and toner on a light emitter to light collector beam path. The combined voltage values are stored separately in memory, each combined voltage value being determined again in relation to its position on the photoconductor.

In Schritt 475 werden die Schritte 410 bis 470 wiederholt, wenn der Fotoleiter mehr als ein Bildfeld aufweist. Vorzugsweise werden Schritt 410 bis Schritt 470 fĆ¼r jedes Bildfeld parallel wiederholt. Beispielsweise werden die Bildfelder in Schritt 410 nacheinander geladen. In Schritt 420 werden die Bildfelder dann mit dem Stufenkeil nacheinander belichtet usw. Auf diese Weise lƤsst sich die Tonerdichte fĆ¼r die gesamte LƤnge oder den gesamten Umfang des Fotoleiters auswerten.In step 475, steps 410-470 are repeated if the photoconductor has more than one frame. Preferably, step 410 through step 470 are repeated in parallel for each frame. For example, the frames are loaded sequentially in step 410. In step 420, the image fields are then exposed successively with the step wedge, etc. In this way, the toner density for the entire length or the entire circumference of the photoconductor can be evaluated.

In Schritt 480 wird die mittlere gemessene Tonerdichte fĆ¼r jede Stufe des Stufenkeils bestimmt (falls mehr als ein Bildfeld vorliegt, erfolgt dies fĆ¼r alle Bildfelder). FĆ¼r jede Lagestelle auf dem Bildfeld wird der Fotoleiterspannungswert von dem kombinierten Spannungswert subtrahiert, um fĆ¼r diese Lagestelle einen gemessenen Tonerspannungswert oder Tonerdichtewert zu erzielen. Die gemessenen Tonerspannungswerte werden fĆ¼r jede Stufe in dem Bildfeld gemittelt, um einen mittleren, gemessenen Tonerspannungswert fĆ¼r jede Stufe zu erhalten. Wenn jedes Bildfeld auf dem Fotoleiter bewertet worden ist, ist der mittlere gemessene Tonerspannungswert fĆ¼r die Stufe auf den Stufenkeil Ć¼ber eine ganze Umdrehung des Fotoleiters reprƤsentativ.In step 480, the average measured toner density is determined for each step of the step wedge (if there is more than one image field, this is done for all frames). For each location on the image field, the photoconductor voltage value is subtracted from the combined voltage value to provide a measured toner voltage value for that location or to obtain a toner density value. The measured toner voltage values are averaged for each stage in the image field to obtain a mean measured toner voltage value for each stage. When each image field on the photoconductor has been evaluated, the average measured toner voltage value for the step on the step wedge over a full rotation of the photoconductor is representative.

In Schritt 490 werden die mittleren, gemessenen Tonerspannungswerte oder Dichtewerte fĆ¼r jede Stufe des Stufenkeils mit den Tonerspannungssollwerten verglichen. Die gemessenen Tonerspannungswerte und die Tonerspannungssollwerte werden auf der Ausgabeschnittstelle in Tabellenform dargestellt, wie exemplarisch in Fig. 3 gezeigt. Die Tonerspannungssollwerte sind die, die der Hersteller in den technischen Daten fĆ¼r die elektrostatische Bilderzeugungsvorrichtung angibt.In step 490, the average measured toner tension values or density values for each stage of the step wedge are compared to the toner tension setpoints. The measured toner voltage values and toner voltage references are tabulated on the output interface, as shown by way of example in FIG. The toner voltage set points are those specified by the manufacturer in the electrostatic image forming apparatus specifications.

Alternativ hierzu kann der Fotoleiter den Schritt 440 (zweites Laden) und den Schritt 450 (zweites optisches Belichten) umgehen. Nachdem die Fotoleiterdichten ermittelt worden sind (Schritt 430), ist der Fotoleiter zur Tonerstation ohne Beaufschlagung durch weitere Verarbeitungskomponenten transportierbar. Der Fotoleiter kƶnnte die anderen Komponenten passieren oder in RĆ¼ckwƤrtsrichtung ein zweites Mal die Tonerstation durchlaufen, um mit Toner beaufschlagt zu werden. Die Richtungsumkehr des Fotoleiters zieht jedoch zusƤtzliche komplexe Schritte nach sich, wenn der Fotoleiter mehrere Bildfelder umfasst. Zudem kƶnnte ein zweites Densitometer vor der Tonerstation angeordnet sein, um die Fotoleiterdichtewerte vor Aufbringen des Toners zu ermitteln.Alternatively, the photoconductor may bypass step 440 (second load) and step 450 (second optical exposure). After the photoconductor densities have been determined (step 430), the photoconductor is transportable to the toning station without being affected by other processing components. The photoconductor could pass through the other components or traverse the toner station a second time in the reverse direction to be charged with toner. However, reversing the direction of the photoconductor involves additional complex steps when the photoconductor includes multiple frames. In addition, a second densitometer could be located in front of the toning station to determine the photoconductor densities before applying the toner.

Obwohl die Erfindung mit besonderem Bezug auf bevorzugte AusfĆ¼hrungsbeispiele beschrieben wurde, ist die Erfindung nicht darauf beschrƤnkt. So kƶnnen innerhalb des Schutzbereichs der nachstehenden AnsprĆ¼che Ƅnderungen und Abwandlungen vorgenommen werden. Beispielsweise kƶnnten die Spannungswerte dazu genutzt werden, flƤchenspezifische Probleme in Verbindung mit dem Fotoleiter zu ermitteln. Die Spannungswerte kƶnnten auch beispielsweise verwendet werden, um zu ermitteln, ob in einem bestimmten Stufenbereich ein OberflƤchenproblem oder ein sonstiges Problem vorliegt. Der Benutzer kƶnnte jeden gemessenen Tonerspannungswert sowie die Ć¼brigen Spannungswerte kontrollieren. Es kƶnnten zusƤtzliche statistische Analysen bereitgestellt werden, um Problembereiche zu erkennen. Obwohl die Erfindung mit besonderem Bezug auf bevorzugte AusfĆ¼hrungsbeispiele beschrieben wurde, ist die Erfindung daher nicht darauf beschrƤnkt, sondern es kƶnnen innerhalb des Schutzbereichs der nachstehenden AnsprĆ¼che Ƅnderungen und Abwandlungen vorgenommen werden.Although the invention has been described with particular reference to preferred embodiments, the invention is not limited thereto. Thus, changes and modifications may be made within the scope of the following claims. For example, the voltage values could be used to determine area-specific problems associated with the photoconductor. The voltage values could also be used, for example, to determine if there is a surface problem or other problem in a particular step area. The user could choose any measured toner voltage value as well as the rest Check voltage values. Additional statistical analysis could be provided to identify problem areas. Therefore, while the invention has been described with particular reference to preferred embodiments, the invention is not limited thereto, but changes and modifications may be made within the scope of the following claims.

Bezugszeichenreference numeral

100100
elektrofotografische (EP) Bilderzeugungsvorrichtungelectrophotographic (EP) image forming apparatus
105105
Fotoleiterphotoconductor
110110
Tragwalzensupport rollers
115115
Motorengine
118118
primƤrer Laderprimary loader
120120
Belichtungsvorrichtungexposure device
125125
Tonerstationtoning station
130130
Ɯbertragungsladertransfer charger
140140
Fixierstationfuser
150150
Reinigercleanser
160160
Densitometerdensitometer
165165
Lichtemitterlight emitter
170170
Lichtkollektorlight collector
175175
Mikroprozessormicroprocessor
180180
SpeicherStorage
185185
EingabeschnittstelleInput interface
190190
AusgabeschnittstelleOutput interface
SS
Papierpaper
200200
Stufenkeilstep wedge

Claims (12)

  1. A method for on-line image quality assessment of an image-forming device having a photoconductor (105) with multiple image frames and an on-line density measuring device (160), comprising:
    applying in each image frame a toner image (200) having successive tones corresponding to a plurality of step areas of toner density;
    measuring multiple toner densities with the on-line density measuring device (160) for a plurality of locations within the step areas;
    averaging the measured toner densities within the steps;
    characterized by:
    displaying an output chart enabling an operator to compare multiple readings indicative of averaged toner densities with corresponding aim values.
  2. A method in accordance with claim 1, further comprising the step of displaying on the output chart a map of the toner density on the photoconductor (105).
  3. A method in accordance with claim 1, wherein the output chart indicates averaged toner density for each step area of each image frame.
  4. A method in accordance with claim 1, wherein the displaying step provides readings indicative of toner density for a particular step of the step tablet (200) over one complete revolution of the photoconductor (105).
  5. A method in accordance with claim 1, further comprising the step of determining localized defects in the photoconductor (105) causing the density of one or more steps not to be at the desired aim value.
  6. A method in accordance with claim 1, wherein multiple readings for a particular step area in all of the image frames are averaged to give an average measured toner voltage reading for that particular step in the step table (200).
  7. An image-forming device having a photoconductor (105) with multiple image frames and comprising:
    a toning station (125) for applying in each image frame a toner image having successive tones corresponding to a plurality of step areas of toner density;
    an on-line density measuring device (160) for measuring multiple toner densities with the on-line density measuring device for a plurality of locations within the step areas;
    a microprocessor (175) for averaging the measured toner densities within the steps;
    characterized by:
    a display device (190) for displaying an output chart enabling an operator to compare multiple readings indicative of averaged toner densities with corresponding aim values.
  8. A device in accordance with claim 7, wherein the display device (190) provides a map of the toner density on the photoconductor (105).
  9. A device in accordance with claim 7, wherein the output chart indicates averaged toner density for each step area of each image frame.
  10. A device in accordance with claim 7, wherein the display device provides readings indicative of toner density for a particular step of the step tablet (200) over one complete revolution of the photoconductor.
  11. A device in accordance with claim 7, wherein the display device (190) provides determination of localized defects in the photoconductor (105) causing the density of one or more steps not to be at the desired aim value.
  12. A device in accordance with claim 7, wherein multiple readings for a particular step area in all of the image frames are averaged by the microprocessor (175) to give an average measured toner voltage reading for that particular step in the step table (200).
EP01117708A 2000-08-01 2001-07-27 Image forming device with online image quality evaluation and associated method Expired - Lifetime EP1178362B1 (en)

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US09/629,394 US6650848B1 (en) 2000-08-01 2000-08-01 Image-forming device having on-line image quality assessment and related method

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US6650848B1 (en) 2003-11-18
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DE10136746A1 (en) 2002-02-14
AU2001271906A1 (en) 2002-02-13
CA2386761C (en) 2005-09-20
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DE50109854D1 (en) 2006-06-29
EP1178362A3 (en) 2002-10-02

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