JP2005254491A - Correcting device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce defects in a picture such as stripes by specifying the process causing the defect and applying a correction. <P>SOLUTION: An image output controlling section 30 is equipped with an LED printing head (LPH) 14, a scanning correcting means, and a defect detecting means. In this case, for the LED printing head (LPH) 14, a plurality of recording elements are arranged. The scanner correcting means reads an image being output by using the LPH 14 by an image reading device (IIT), and adjusts respective recording elements of the LPH 14 based on the read value. The defect detecting means detects a picture quality defect occurring by factors other than the LPH 14 regarding the output image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile, and more particularly to an image forming apparatus including a print head for performing optical writing.

  In an image forming apparatus such as a printer, a copying machine, or a facsimile employing an electrophotographic system, an electrostatic latent image is obtained by irradiating light on a uniformly charged photosensitive member by an optical recording unit. A toner is added to the electrostatic latent image to make a visible image, and the image is formed by transferring and fixing on the recording paper. As such an optical recording means, in addition to an optical scanning method in which a laser is used to scan and expose a laser beam in the main scanning direction, in recent years, in response to a request for downsizing of an apparatus, an LED (Light Emitting Diode) which is a light emitting element is used. : An optical recording means using an LED print head (LPH) in which a number of light emitting diodes) are arranged in the main scanning direction.

  This LPH generally has an LED array in which a plurality of LED chips in which a large number of LEDs are arranged in a line are arranged, and a large number of rods for imaging light output from the LEDs on the surface of the photosensitive member (photosensitive drum). And a lens array in which lenses are arranged. In the image forming apparatus, each LED of the LPH is driven to emit light based on the input image data, light is output toward the photoconductor, and light is imaged on the photoconductor surface by the lens array. An electrostatic latent image is formed in the sub-scanning direction by relatively moving the photoconductor and LPH.

  Here, in an image forming apparatus using an LED as a recording head, unevenness of the recording head (for example, uneven exposure) appears as image unevenness as it is, and therefore an operation of correcting the unevenness of the recording head is performed. As a method for correcting the unevenness of the recording head, for example, a technique (so-called scanner correction) for correcting the unevenness of the recording head by actually forming a test pattern with the recording head and reading the obtained test pattern with a scanner or the like. Traditionally exists. Further, as a conventional technique described in the publication using LPH, for example, there is one that corrects density unevenness more accurately by correcting a magnification error in recording and reading (see, for example, Patent Document 1). Further, a technique is disclosed in which density unevenness caused by other than the recording head is corrected by the recording head, thereby reducing image unevenness and eliminating unstable factors that cause image fluctuations (see, for example, Patent Document 2). ).

JP 2001-146038 A (page 5-6, FIG. 2) JP-A-11-177824 (page 5-6, FIG. 1)

  As described above, according to the conventional scanner correction, in addition to the density unevenness, image quality defects (for example, vertical stripes generated in the paper conveyance direction) caused by causes other than the recording head (LPH) are caused to some extent. Can be resolved. However, some of these image quality defects (defects) are based on characteristics that occur temporarily and change immediately, such as when dust is removed, such as when dust is removed. It is not preferable to correct the characteristic change based on such a temporary factor with the amount of light of LPH, and it is more desirable to eliminate the streaks by removing dust itself in view of the subsequent maintainability.

  Also, if scanner correction is performed only at the time of shipment from the factory, if too large a correction is made, once the consumables are replaced after they are put on the market, a lot of streaks will occur. There was a problem. In other words, if there is a defect in the process part other than LPH and a streak is generated, if correction exceeding the limit is performed, there is a high possibility that the defect will occur at an early stage after shipment. For this reason, even if correction can be performed by LPH, if the correction is performed excessively, the maintainability of the image quality due to the correction of LPH is reduced.

The present invention has been made in order to solve the technical problems as described above, and the object of the present invention is to identify the process causing the malfunction and correct it, thereby further improving the image quality trouble. It is to reduce.
Another object is to minimize the appearance of uneven density over time.
Still another object is to identify a process that causes a failure and apply a fundamental solution to the process.

  For this purpose, the correction apparatus to which the present invention is applied grasps the state of this image quality defect from image quality defects such as streaks that occur when an image is output using a recording head in which a plurality of recording elements are arranged. And a determination means for determining, for each correction portion, whether or not to perform correction for each recording element adjustment on the recording head from the state of the image quality defect grasped by the defect condition grasping means. Including. This correction apparatus may be an image forming apparatus or a correction jig.

  Here, this defect state grasping means is characterized by detecting image quality defects caused by factors other than the recording head. In addition, when an image quality defect caused by factors other than the recording head is detected by the defect state grasping means, an output means for outputting information to that effect is further provided. It is preferable in that the correction point can be easily specified for the service person. Further, when the image output using the recording head is read, the defect state grasping means grasps the occurrence state of the image quality defect inherent to the recording head, and the determining means determines the image quality defect inherent to the recording head. For the above, correction for adjusting the printing element can be performed.

  On the other hand, an image forming apparatus to which the present invention is applied includes a recording head in which a plurality of recording elements are arranged, and an image output using the recording head is read by a reading unit, and each recording element is based on the read value. A scanner correcting means for adjusting the image quality, and a defect detecting means for detecting an image quality defect caused by factors other than the recording head for the output image. In addition to the case where the reading unit is provided inside the image forming apparatus, for example, a reading unit included in a jig as a measuring apparatus may be used.

  Here, when the image quality defect grasped by the defect detection unit does not exceed a predetermined value, the scanner correction unit including the image quality defect performs scanner correction. The predetermined value is a value that is predetermined as a level that can cope with image quality defects by correcting the recording head, and is stored in, for example, a memory provided in the image forming apparatus. This level that can be handled varies depending on the type of recording head to be used, the usage mode of the apparatus, and the like.

Therefore, the defect detection means uses at least one of the width unique to the printhead, the position unique to the printhead, and the frequency unique to the printhead, so that the target image quality defect is other than the printhead. It can be characterized by detecting whether or not it is a factor.
In addition, this defect detection means is used when the reading means reads a density difference exceeding the estimated density unevenness from the light quantity detection result of the recording head detected by the light quantity detection means in advance with a jig or the like. It is possible to detect that the image quality defect is a factor other than the recording head. As this light quantity detection means, a photodiode etc. are mentioned, for example.

Further, for example, for the plurality of color images output by a tandem full-color machine, the defect detection means grasps that the image quality defect common to the whole is a factor other than the recording head. it can.
Furthermore, the defect detection means acquires the density of an image formed by bias development that forms an image without performing exposure by the recording head, and detects image quality defects caused by factors other than the recording head. Can be a feature.
The defect detecting means outputs a plurality of density images using the recording head, obtains a gamma corresponding to the main scanning position from the density detection by the reading means, and compares the obtained gamma to detect image quality defects other than the recording head. It can be characterized by detecting. More specifically, when the value of gamma exceeds a predetermined value that is a normal fluctuation range by the print head and becomes extremely large or small, it can be detected that the image quality is other than that of the print head.

  According to the present invention, for example, it is possible to minimize the appearance of uneven density over time.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing the overall configuration of an image forming apparatus to which this embodiment is applied, and shows a so-called tandem type digital color printer. An image forming apparatus shown in FIG. 1 includes an image processing system 10 that forms an image corresponding to gradation data of each color, an image output control unit 30 that controls the image processing system 10, such as a personal computer (PC). 2 and an image reading apparatus (IIT) 3 and an image processing unit (IPS: Image Processing System) 40 that performs predetermined image processing on image data received from these.

  The image processing system 10 includes an image forming unit 11 composed of a plurality of engines arranged in parallel at regular intervals in the horizontal direction. The image forming unit 11 includes four image forming units 11Y, 11M, 11C, and 11K of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 11 (11Y, 11M, 11C, and 11K) respectively include a photosensitive drum 12 that is an image carrier (photosensitive member) that forms an electrostatic latent image and carries a toner image, and a photosensitive drum 12. A charger 13 for uniformly charging the surface of the toner, an LED print head (LPH) 14 which is a print head for exposing the photosensitive drum 12 charged by the charger 13, and a developer for developing a latent image obtained by the LPH 14. 15 is provided. Further, the image process system 10 conveys the recording paper in order to multiplex-transfer the toner images of the respective colors formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K onto the recording paper. A sheet conveying belt 21, a driving roll 22 which is a roll for driving the sheet conveying belt 21, and a transfer roll 23 for transferring the toner image on the photosensitive drum 12 onto a recording sheet are provided.

  Each of the image forming units 11Y, 11M, 11C, and 11K includes substantially the same components except for the toner stored in the developing unit 15. Image signals input from the PC 2 or IIT 3 are subjected to image processing by the image processing unit 40 and supplied to the image forming units 11Y, 11M, 11C, and 11K through the interface. The image process system 10 operates based on a control signal such as a synchronization signal supplied from the image output control unit 30. First, in the yellow image forming unit 11Y, an electrostatic latent image is formed on the surface of the photosensitive drum 12 charged by the charger 13 by the LPH 14 based on the image signal obtained from the image processing unit 40. A yellow toner image is formed on the electrostatic latent image by the developing unit 15, and the formed yellow toner image is transferred to the recording paper on the paper transport belt 21 that rotates in the direction of the arrow in the figure. It is transcribed using. Similarly, magenta, cyan, and black toner images are formed on the respective photosensitive drums 12 and are multiple-transferred onto the recording paper on the paper transport belt 21 using the transfer roll 23. The multiple transferred toner images on the recording paper are conveyed to the fixing device 24 and fixed on the recording paper by heat and pressure.

  FIG. 2 is a diagram showing a configuration of an LED print head (LPH) 14 that is a recording head. The LPH 14 includes an LED array 51 in which a large number of LEDs are arranged as a recording element (light emitting element), a printed circuit board 52 on which a circuit for controlling the driving of the LED array 51 is formed and a LED. A SELFOC lens array (SLA) (trademark) 53 for imaging the emitted light beam on the photosensitive drum 12 is provided. The printed circuit board 52 and the SELFOC lens array 53 are held in a housing 54. In the LED array 51, LEDs are arranged in the main scanning direction, for example, by the number of pixels. For example, when an A3 size short (297 mm) is used as the main scanning direction, at a resolution of 600 dpi, it is necessary to arrange at least 7040 LEDs every about 42.3 μm. In addition, the arrangement | sequence may be arranged in zigzag form other than the case where it is located in a line. The printed circuit board 52 is a memory (ROM or the like) in which data relating to a correction value obtained by the exposure amount measuring method to which the present embodiment is applied (which may be light amount correction data calculated from the correction value) is stored. And the light quantity of the LEDs constituting the LED array 51 is corrected based on the data stored in the memory.

  FIG. 3 is a hardware configuration diagram of the LPH 14 to which the present embodiment is applied, and employs a self-scanning light emitting element (SLED) system having a thyristor structure. The LPH 14 receives, for example, video data (Video Data) from the image processing unit (IPS) 40 and supplies a lighting signal to each LED chip 63, and a clock and a synchronization signal from the image output control unit 30. A transfer signal generator 62 is provided for receiving and generating a transfer signal. The LPH 14 to which this embodiment is applied includes 58 LED chips 63 having 128 LEDs, for example, and each LED chip 63 emits light of 128 dots and the entire LPH 14 emits 7424 dots. Is possible. The lighting signal generator 61 generates 58 lighting signals (CKI1 to CKI58) for the 58 LED chips 63. The transfer signal generation unit 62 generates six transfer signals (CKS_1 to CKS_6) and six sets of transfer signals (CK1_1 to CK1_6, CK2_1 to CK2_6). For example, in the example shown in FIG. 3, the number of dots of each LED chip 63 is sequentially turned on by sequentially lighting 128 times in one main scanning line, and the number of simultaneous lighting in one scanning line is 58 is the maximum.

  FIG. 4 is a block diagram showing a configuration of the lighting signal generator 61, and shows a first configuration example to which the present embodiment is applied. The lighting signal generation unit 61 rearranges the video data that is input raster data in the order of light emission, the rearrangement unit 71, and the light amount unevenness correction unit that provides the light amount unevenness correction value (density unevenness correction value) for correcting the light amount unevenness. 72. In addition, a lighting clock number calculation unit 73 that calculates the number of lighting clocks for the video data rearranged in the light emission order by the rearrangement unit 71 using the light amount unevenness correction value obtained from the light amount unevenness correction unit 72, and the calculated lighting. A serial / parallel conversion unit 74 that converts the number of clocks into parallel data, and a pulse width modulation (PWM) 75 that applies pulse width modulation to each parallel-converted signal to change the amount of light and generate each lighting signal. It has.

FIG. 5 is a diagram for explaining an outline of processing executed by the lighting clock number calculation unit 73. The lighting clock number calculation unit 73 receives the video data a rearranged in the light emission order and the light amount unevenness correction value b stored in the light amount unevenness correction unit 72, and outputs the lighting clock number y. At this time, the number of lighting clocks y is, for example,
y = a · (1 + b / 255)
It can be expressed as In the above equation, the light amount unevenness correction value b changes from 0 to 255, and as a result, the lighting clock number y output from the lighting clock number calculation unit 73 changes from a to 2a.

FIG. 6 is a circuit diagram for explaining the configuration of the LED chip 63, and here, Chip 1 which is the first array chip is taken as an example. Although the input transfer signal and the lighting signal are different, Chip2 to Chip58 have the same configuration. The LED chip 63 includes 128 thyristors (S1 to S128), 128 LEDs (LED1 to LED128), 127 diodes (CR1 to CR127), 128 resistors (R1 to R128), and signal lines. It is composed of transfer current limiting resistors (R1A, R2A, R3A) that prevent excessive current from flowing.
The anode terminals (A1 to A128), which are input terminals of the thyristors (S1 to S128), are connected to the power supply line 65. A power supply voltage VDD (VDD = 5.0 V) is supplied to the power supply line 65. The transfer signal CK1 from the transfer signal generator 62 passes through the transfer current limiting resistor R1A to the cathode terminals (K1, K3,..., K127) that are the output terminals of the odd-numbered thyristors (S1, S3,..., S127). Supplied. Further, the transfer signal CK2 from the transfer signal generator 62 is applied to the transfer current limiting resistor R2A at the cathode terminals (K2, K4,..., K128) that are the output terminals of the even-numbered thyristors (S2, S4,..., S128). Is supplied through.

  On the other hand, the gate terminals (G1 to G128), which are the control terminals of the thyristors (S1 to S128), are respectively connected to the power supply line 66 via resistors (R1 to R128) provided corresponding to the thyristors. The power line 66 is grounded (GND). The gate terminals of the LEDs (LED1 to LED128) provided corresponding to the thyristors (S1 to S128) are connected to the gate terminals (G1 to G128) of the thyristors (S1 to S128), respectively. Furthermore, the anode terminals of the diodes (CR1 to CR127) are connected to the gate terminals (G1 to G128) of the thyristors (S1 to S128). The cathode terminals of the diodes (CR1 to CR127) are connected to the gate terminals of the next-stage thyristors, respectively. That is, the diodes (CR1 to CR127) are connected in series. The anode terminal of the diode CR1 is connected to the transfer signal generator 62 via the transfer current limiting resistor R3A and receives the transfer signal CKS. Further, the cathode terminals of the LEDs (LED1 to LED128) receive the lighting signal CKI1 from the lighting signal generator 61.

Next, the operation of the LED chip 63 will be described with reference to the timing chart shown in FIG.
First, when the chip 1 of the LED chip 63 is instructed to start the operation, the transfer signal generator 62 supplies a high-level transfer signal CKS as shown in FIG. That is, a high level is input to the gate terminal G1 of the thyristor S1 shown in FIG. When the transfer signal CKS is at a high level, the thyristor S1 is turned on when the transfer signal CK1 output from the transfer signal generator 62 is at a low level as shown in FIG. 7B.

  As described above, among the odd-numbered thyristors (S1, S3,...) To which the transfer signal CK1 is supplied when the transfer signal CKS is at a high level, the gate terminal has the highest potential, that is, a gate equal to or higher than the threshold voltage of the thyristor. The voltage thyristor S1 is turned on. At this time, since the transfer signal CK2 is at the high level as shown in FIG. 7C, the potentials of the cathode terminals (K2, K4,...) Of the even-numbered thyristors (S2, S4,...) Remain high. The even-numbered thyristors (S2, S4,...) Are kept off. Further, since the lighting signal CKI1 is at a high level as shown in FIG. 7D, the potential of the cathode terminals of the LEDs (LED1 to LED128) is high, and the LEDs (LED1 to LED128) are not lit. When the lighting signal CKI1 changes from the high level to the low level as shown in FIG. 7D, the potential of the cathode terminal of the LED1 becomes low, and the LED1 is lit.

Next, when the thyristor S1 is turned on, as shown in FIG. 7C, when the transfer signal CK2 becomes low level and the lighting signal CKI1 becomes high level, the even-numbered thyristor (S2 to which the transfer signal CK2 is supplied). , S4,...), The thyristor S2 having the highest potential at the gate terminal, that is, the gate voltage equal to or higher than the threshold voltage of the thyristor is turned on, and the LED 1 is turned off. When the transfer signal CK1 becomes high level as shown in FIG. 7B, the thyristor S1 is turned off, the potential of the gate terminal G1 is gradually lowered by the resistor R1, and the potential of the gate terminal G2 is increased. Along with this, the potentials of the gate terminals G3 and G4 also rise.
Thereafter, when the lighting signal CKI1 changes from the high level to the low level as shown in FIG. 7D, the LED 2 is turned on. Similarly, when the thyristor S2 is on, as shown in FIG. 7B, when the transfer signal CK1 becomes low level again and the lighting signal CKI1 becomes high level, the thyristor S3 is turned on and the LED 2 is not lit. Become. Then, as shown in FIG. 7C, when the transfer signal CK2 becomes high level, the thyristor S2 is turned off.

As described above, in the Chip 1 of the LED chip 63, the thyristor is formed by alternately switching the high level and the low level while providing the overlapping period (the period of Ta shown in FIG. 7) in which the transfer signals CK1 and CK2 are both at the low level. The LEDs (LED1 to LED128) can be sequentially lit by sequentially turning on (S1 to S128) and sequentially setting the lighting signal CKI1 to the low level in synchronization with this. Therefore, the signal lines connected to Chip 1 of the LED chip 63 include three for the transfer signals CKS, CK1, and CK2, one for the lighting signal CKI1, and two power lines (one of which is grounded). Therefore, it is possible to drive only with these six signal lines.
The same applies to Chip2, Chip3,..., Chip58 of the LED chip 63, and the LEDs are sequentially turned on by the transfer signals CKS, CK1, CK2, and the lighting signals CKI2 to CKI58, respectively.

Next, as a characteristic configuration in the present embodiment, a factor analysis process for image quality defects (defects) such as streaks and a corresponding process based on the result will be described.
FIG. 8 is a diagram for explaining an image quality defect analysis process and a corresponding process. Although FIG. 8 is a flowchart showing the analysis processing from step 101 to step 105, it is not essential to implement all of them, and it is sufficient that the determination of step 106 can be made by at least one processing. These processes are performed not only when the image output control unit 30 shown in FIG. 1 or the like is used, but also, for example, at the control unit of a measuring device (jig) used for inspection before manufacture and shipment. Possible forms.

  First, as the first method of analysis, the width, the position, and the frequency of the streak appearing in the image quality are detected (step 101). In the LED chip 63 described with reference to FIG. 3, 128 dots are formed every about 42.3 μm, and the width of one LED chip 63 is about 5.4 mm. Since the LED chips 63 are arranged in a row or in a staggered pattern, if a stripe is observed with the width of the LED chip 63 (about 5.4 mm) or a cycle of an integral multiple thereof, the arrangement of the LED chips 63 It is considered as white streaks or black streaks at seams caused by errors. In addition, when a driver that drives the LED chip 63 by 1/2 is adopted, if the width is about 2.7 mm, which is the driver period, or a stripe that is an integral multiple of this, it is considered that the stripe is due to the LPH 14. Further, for example, when a Selfoc lens having a diameter of 0.45 mm is used as the Selfoc lens array (SLA) 53 shown in FIG. 2, the radius (0.225 mm) period of this Selfoc lens is an integral multiple thereof. In addition, there is a high possibility that the muscle is caused by LPH14. Similarly, if it is a periodic streak caused by problems in manufacturing the LED chip 63, mask accuracy, etc., it is considered to be LPH14. That is, by observing the line width, the line position, and the frequency, and determining whether the frequency is unique to the LPH 14, it is possible to detect the image quality defect caused by the LPH 14 or the other with considerably high accuracy. Is possible. Note that the streaks appearing in the image quality are not necessarily periodic and may appear in a single shot. In such a case, it is possible to determine whether or not the line is unique to the LPH 14 based on the width and the appearance position.

  Further, as a second method of analysis, density unevenness can be estimated from the result of light amount correction performed by a light amount detection means such as a photodiode (PD) for measuring the amount of light emitted from each LED of the LPH 14 ( Step 102). For example, before scanner correction, a rough adjustment of the amount of light is performed with a photodiode (PD) or the like to estimate the density unevenness that appears, and it is possible to determine that the streaks exceeding that value are caused by something other than LPH14. It is. The light amount detection means such as a photodiode (PD) is configured by a jig or the like that is mounted on the LPH 14.

  Further, as a third method of analysis, there is a method of grasping a common line in all colors (step 103). For example, in the so-called tandem type digital color printer as shown in FIG. 1, when there is a streak common to all colors, it can be determined that the streak is caused by factors other than the LPH 14. As a common streak, in the case of the structure shown in FIG. In another tandem structure, for example, an apparatus that employs a system in which a toner image of each color is primarily superimposed on an intermediate transfer member (intermediate transfer belt or the like) and then transferred to a sheet at a time. The image quality defects common to all colors are considered to be caused by, for example, scratches on the surface of an intermediate transfer member (intermediate transfer belt or the like), defects during secondary transfer, and the like.

  In addition to the tandem structure described above, as a mechanism different from that shown in FIG. 1, for example, an image carrier (photosensitive drum) or intermediate transfer belt is rotated four times to form a full color image by superimposing four color toner images. There are so-called four-cycle machines. In such a 4-cycle machine, when a common streak is generated in all colors, there is a cause for the common process of charging or / and LPH, or / and an apparatus used for primary transfer. Can be estimated. With this mechanism, it is not possible to separate between charging, LPH and primary transfer. That is, LPH and other separation cannot be performed by this alone, but it can be used in combination with the above-described step 101 or the like to increase the determination accuracy.

Further, as a fourth method of analysis, there is a method for grasping the difference in gamma (step 104). Here, “gamma” is a change amount (gradient) of the output image density with respect to the input density.
FIGS. 9A to 9C are diagrams for explaining the separation process based on the difference in gamma. FIG. 9A is a diagram plotting the value of gamma at a certain main scanning position. The horizontal axis represents the input density (Cin), and the vertical axis represents the scanner detection density. In order to obtain such a gamma value, first, an image having a plurality of input densities such as 20%, 30%, and 50%, for example, is formed in a strip shape in the main scanning direction and output using the LPH 14. Then, the output image is read using a scanner such as an image reading device (IIT) 3 and the density is detected. By plotting the detected concentration, a value as shown in FIG. 9A is obtained.

  FIGS. 9B and 9C are diagrams showing gamma values according to the main scanning position. FIG. 9B shows the output density when the input density (Cin) changes from 20 to 30. FIG. FIG. 9C shows the value (change) of the output density when the input density (Cin) is changed from 30 to 50. The horizontal axis represents the main scanning position, and the vertical axis represents gamma. A certain amount of gamma difference can be dealt with by LPH14 scanner correction as a variation range of LPH14. However, for example, when the developer is clogged in the developing unit 15, the output density is not changed at all even if the input density is increased. That is, depending on the position in the main scanning direction, the grasped gamma value (gradient) may be significantly different from the normal value (the value grasped at the other scanning direction position). Therefore, a predetermined value is determined in advance as the fluctuation range of the LPH 14, and if it exceeds this value, it can be considered that the factor other than the LPH 14 is a factor.

  Furthermore, as a fifth method of analysis, there is a method of grasping a streak caused by adjusting the bias of the developing device 15 (step 105). By adjusting the developing bias, an image is output under the condition that a toner image can be formed without performing exposure using the LPH 14. By observing this output image, it is possible to determine that the resulting streaks are caused by something other than LPH14.

  By at least one of the above steps 101 to 105, it is determined whether or not the streak (image quality defect) other than the LPH 14 exceeds a predetermined value (step 106). If the image quality defect does not exceed a predetermined value, scanner correction for the LPH 14 is executed (step 107), and the process ends. If it exceeds the predetermined value, the image quality defect status is displayed on, for example, a control panel or LCD display, the image quality defect is notified (warned) to the user (step 108), and the process ends. The “predetermined value” that is the determination criterion in step 106 is a value that is determined in advance as a level that can deal with image quality defects by correcting the LPH 14 that is the recording head. For example, as shown in FIGS. In the example shown, the LPH fluctuation range which is the range of the broken line is a predetermined value. Similarly, the “predetermined value” can determine, for example, a density unevenness grade of a level (level) that can be dealt with by correction for the LPH 14 among the density unevenness grades. These “predetermined values” are stored in, for example, various memories provided in the image output control unit 30 illustrated in FIG. 1 or various memories provided in the printed circuit board 52 illustrated in FIG.

  Further, in the process as shown in FIG. 8, it is possible to determine whether or not to execute correction for each of the plurality of recording elements (LEDs) of the recording head (LPH 14). That is, it is determined whether or not to cope with the scanner correction for each recording element from the state of the image defect to be grasped. For example, when the defect is large and the defect cannot be solved only by the scanner correction of the recording head, or temporarily such as dust Corrections are not made for changes in typical characteristics. As a result, it is possible to perform scanner correction only on portions where scanner correction is effective, and it is possible to eliminate problems caused by applying corrections that are too high in grade. In the description of FIG. 8, what is unique to the LPH 14 is dealt with in step 106. However, for example, it is determined only by whether or not the image quality defect such as density unevenness or streaks exceeds a predetermined value. It is also possible to determine the processing. This is because it may be advantageous to deal with only minor corrections that can be dealt with by scanner correction only by correction for LPH 14.

  As described above in detail, according to the present embodiment, at the time of density detection for performing scanner correction, the LPH 14 and other processes are determined depending on, for example, whether or not the state of the muscle exceeds a predetermined value. It is possible to isolate the cause system between the two. Further, by separating the cause system, it is possible to solve the conventional problem of forcibly correcting by the LPH 14 and to optimize the correction by the LPH 14. Thereby, it is possible to improve the maintainability of the image quality by the scanner correction. Further, the determination as to whether or not to perform the scanner correction can be performed at the time of correction in the market, or can be performed at the time of manufacture. Furthermore, it is also effective to perform it inside the apparatus, and it can also be performed using a jig outside the apparatus.

  However, the urgency may be less depending on the level of failure. Performing scanner correction as an emergency measure is very effective from the viewpoint of speeding up troubleshooting. Therefore, even if the cause system is identified as a result of the separation of the cause system as in the process shown in FIG. There is also a method of notifying only that the process is the cause after performing the correction. On the other hand, if it is determined that the scanner correction is impossible, it is preferable not to perform the correction but only to notify that the process is the cause. In this embodiment, the LPH 14 in which LEDs are arranged has been described. However, other functions can be similarly applied to a recording head in which printing elements are arranged.

  As described above, in the present embodiment, when correction is performed in the market, it is possible to easily identify image quality defects (defects) such as streaks caused by other than the recording head. In addition, it is possible to suppress the appearance of uneven density over time only by correction at the time of factory shipment. Furthermore, it is possible to eliminate the need for scanner correction when exchanging consumables.

  As an application example of the present invention, for example, the present invention can be applied to an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic system. The image forming apparatus can also be applied to a correction device as a jig that performs scanner correction and corrects density unevenness. Further, the concept of the recording element can be expanded and applied to an apparatus having a recording head on which recording elements are arranged, such as an ink jet printer.

1 is a diagram illustrating an overall configuration of an image forming apparatus to which the exemplary embodiment is applied. It is the figure which showed the structure of the LED print head (LPH). It is a hardware block diagram of LPH to which this Embodiment is applied. It is the block diagram which showed the structure of the lighting signal generation part. It is a figure for demonstrating the outline | summary of the process performed in the lighting clock number calculation part. It is a circuit diagram for demonstrating the structure of a LED chip. It is a timing chart for demonstrating operation | movement of a LED chip. It is a figure for demonstrating the analysis process and response process of an image quality defect. (a)-(c) is a figure for demonstrating the separation process by the difference in gamma.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image process system, 11 ... Image forming unit, 12 ... Photosensitive drum, 13 ... Charger, 14 ... LED print head (LPH), 15 ... Developer, 51 ... LED array, 52 ... Printed circuit board, 53 ... Cell Fock lens array (SLA) 61 ... Lighting signal generator 62 ... Transfer signal generator 63 ... LED chip 71 ... Rearranger 72 ... Light intensity unevenness corrector 73 ... Lighting clock number calculator 74 ... Serial Parallel converter

Claims (12)

A defect state grasping means for grasping a state of the image quality defect from an image quality defect generated when an image is output using a recording head in which a plurality of recording elements are arranged;
And a determination unit that determines, for each correction portion, whether or not to perform correction for each recording element adjustment on the recording head from the state of the image quality defect grasped by the defect state grasping unit.   The correction apparatus according to claim 1, wherein the defect state grasping unit detects an image quality defect caused by factors other than the recording head.   3. The correction apparatus according to claim 2, further comprising an output means for outputting information indicating that an image quality defect caused by factors other than the recording head is detected by the defect state grasping means. . The defect state grasping means grasps an occurrence state of an image quality defect unique to the recording head when an image output using the recording head is read,
The correction apparatus according to claim 1, wherein the determination unit executes correction for adjusting the recording element for an image quality defect inherent in the recording head. A recording head in which a plurality of recording elements are arranged;
A scanner correction unit that reads an image output using the recording head with a reading unit, and adjusts each recording element based on the read value;
An image forming apparatus comprising: a defect detection unit that detects an image quality defect caused by factors other than the recording head for an output image.   6. The image according to claim 5, wherein when the image quality defect grasped by the defect detection means does not exceed a predetermined value, scanner correction is executed by the scanner correction means including the image quality defect. Forming equipment.   The image forming apparatus according to claim 6, wherein the predetermined value is a value determined in advance as a level that can cope with the image quality defect by correcting the recording head.   The defect detection means uses at least one of a width specific to the recording head, a position specific to the recording head, and a frequency specific to the recording head, and the target image quality defect is other than the recording head. 6. The image forming apparatus according to claim 5, wherein it is detected whether or not it is a factor of the above.   The defect detection means determines that a target image quality defect is detected when a density difference exceeding an estimated density unevenness amount is read by the reading means from the light quantity detection result of the recording head detected by the light quantity detection means. The image forming apparatus according to claim 5, wherein the image forming apparatus is detected as a factor other than the recording head.   The image forming apparatus according to claim 5, wherein the defect detection unit grasps that an image quality defect common to the plurality of output color images is a factor other than the recording head.   The defect detection means acquires density of an image formed by bias development for forming an image without performing exposure by the recording head, and detects an image quality defect caused by factors other than the recording head. The image forming apparatus according to claim 5.   The defect detection means outputs an image having a plurality of densities using the recording head, obtains a gamma corresponding to the main scanning position from the density detection by the reading means, and compares the obtained gamma to obtain an image quality other than the recording head. 6. The image forming apparatus according to claim 5, wherein a defect is detected.

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