JP6149883B2 - Image inspection apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image inspection apparatus that optically reads an image and obtains the line width of the image, and an image forming apparatus that obtains the line width of the image and sets the output of image writing according to the line width.

  In an apparatus that optically reads an image formed on a medium such as paper, the image is correctly recognized in order to binarize the read image or to determine whether the formed image is written correctly. Techniques to enable this have been proposed.

  For example, in a device that reads one-dimensional or two-dimensional encoded information such as a barcode, the presence or absence of blur in the read image is determined, and the distance from the device to the reading target is within a range where reading can be satisfactorily performed. There has been proposed a technique for determining whether or not (see, for example, Patent Document 1).

  Also, in an apparatus for reading a bar code, the bar code has black and white alternately, and the black and white line width is an integral multiple of the thinnest line width. A technique for recognizing a line width after performing with a value has been proposed (see, for example, Patent Document 2).

  Further, a technique has been proposed in which all search lines are searched in a direction perpendicular to the edge from the edge of the image to search for edge pieces (see, for example, Patent Document 3).

JP 2006-209208 A Japanese Patent Laid-Open No. 62-120585 JP 2010-134958 A

  In the process of obtaining the line width of an image from image data obtained by optically reading a linear image, the line width is obtained by detecting edge portions of the image and obtaining the length between the edge portions. When the distance from the image to be read to the optical reading means changes, the image data becomes so-called blurred and the edge portion in the image data cannot be detected accurately, and the line width changes from the original value.

  For example, the image writing output is set to form an image, and the line width of the formed image is obtained to obtain the relationship between the image writing output and the line width of the formed image, thereby obtaining a predetermined line. In the technique of setting the image writing output to form an image with a width, the image writing output cannot be set correctly unless the line width can be obtained correctly.

  However, in any of the above-described prior art documents, the correct line width cannot be obtained when the distance from the image to be read to the optical reading means changes.

  The present invention has been made to solve such a problem, and an image inspection apparatus that can obtain the line width of an image with a correct value, and obtains the line width of the image and writes the image according to the line width. An object of the present invention is to provide an image forming apparatus for setting the output of the image.

In order to solve the above-described problem, the invention according to claim 1 is directed to a detection unit that optically reads a linear inspection image formed on a medium, and image data acquired by reading the inspection image by the detection unit. Control means for calculating the edge blur of the rising edge portion and the falling edge portion of the data, calculating the line width of the inspection image, and determining the line width of the inspection image determined corresponding to the edge blur and the actually measured value of the line width; A line width correction table in which the actual values of edge blur and line width and the actual line width of the inspection image are stored in association with each other, and the control means stores the line width correction table with the actual values of edge blur and line width. The image inspection apparatus refers to an image inspection apparatus that obtains the corrected line width value from the line width correction table and obtains the actual line width of the inspection image .

The invention according to claim 2 detects an image forming means for forming an image on a medium, a detecting means for optically reading the image formed on the medium, and a linear inspection image formed on the medium by the image forming apparatus. The edge blur of the rising edge part and the falling edge part of the image data is calculated from the image data read and acquired by the means, and the line width of the inspection image is calculated, corresponding to the measured values of the edge blur and the line width. A control means for obtaining the determined line width of the inspection image, a line width correction table in which the actual values of the edge blur and the line width and the actual line width of the inspection image are stored in association with each other. The image forming apparatus obtains the actual line width of the inspection image by referring to the line width correction table with the actually measured value of the line width, and acquiring the corrected line width value from the line width correction table .

The invention according to claim 3, in correspondence with the edge blur varies durability comprising a plurality of line width correction table, control means, according to claim 2 for selecting a line width correction table according to durability An image forming apparatus.

The invention according to claim 4, in correspondence with the edge blur that changes in the environment comprising a plurality of line width correction table, control means, according to claim 2 for selecting the line width correction table according to the setting of the environment An image forming apparatus.

In the invention according to claim 5 , the control means lowers the line width detection threshold for obtaining the line width from the image data obtained by reading the inspection image with the detection means, and the upper limit threshold for obtaining the edge blur. The image forming apparatus according to claim 2 , wherein the threshold value is changed based on either durability or environment, or both durability and environment.

The invention according to claim 6, control means, based on the detection result of the line width, according to any one of claims 2 to 5 to set the output of the image forming means for forming an image in the line width This is an image forming apparatus.

The invention according to claim 7 is the image according to any one of claims 2 to 6 , wherein the detection means is an in-line sensor that detects color information and reflectance information of an image formed by the image forming means. Forming device.

The invention according to claim 8 is an image forming apparatus according to any one of claims 2 to 6 , wherein the detecting means is an optical sensor for detecting reflectance information of an image formed by the image forming means. It is.

  According to the present invention, the inspection determined from the edge blur and the line width of the inspection image in the image data obtained by reading the linear inspection image and the line width of the inspection image, based on the measured values of the edge blur and the line width. The actual line width of the image can be obtained accurately. As a result, when the correct line width cannot be obtained due to the change in the distance from the medium to the detection means, the correct line width value can be calculated without acquiring the incorrect line width.

It is a block diagram which shows an example of the image inspection apparatus of this Embodiment. It is a functional block diagram which shows an example of a function structure of the image inspection apparatus of this Embodiment. It is explanatory drawing which shows an example of a test | inspection image. It is explanatory drawing which shows an example of the image data acquired by reading a test | inspection image. It is explanatory drawing which shows an example of a line | wire width correction table. It is explanatory drawing which shows an example of operation | movement of the image inspection apparatus of this Embodiment. It is explanatory drawing which shows an example of the relationship between edge blurring and line | wire width. 1 is a configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. 3 is a functional block diagram illustrating an example of a control function of the image forming apparatus according to the present exemplary embodiment. FIG. It is explanatory drawing which shows an example of a line | wire width correction table. It is explanatory drawing which shows an example of a test | inspection image. It is a flowchart which shows the flow of the process in the 1st operation example. It is explanatory drawing which shows the relationship between the light quantity and line width of a laser diode. It is explanatory drawing which shows the change of the edge blur by developer durability. It is explanatory drawing which shows the change of the edge blur by an environment. It is explanatory drawing which shows an example of the line | wire width correction table selected by durability. It is explanatory drawing which shows an example of the line | wire width correction table selected by environment.

<Example of Configuration of Image Inspection Apparatus of this Embodiment>
FIG. 1 is a configuration diagram illustrating an example of an image inspection apparatus according to the present embodiment. FIG. 1A is a plan view of the image inspection apparatus viewed from above, and FIG. 1B is a side view of the image inspection apparatus. It is the side view seen from. FIG. 2 is a functional block diagram illustrating an example of a functional configuration of the image inspection apparatus according to the present embodiment.

  3 is an explanatory diagram illustrating an example of an inspection image, FIG. 4 is an explanatory diagram illustrating an example of image data obtained by reading the inspection image, and FIG. 5 is an explanatory diagram illustrating an example of a line width correction table. is there.

  The image inspection apparatus 1A according to the present embodiment reads a linear inspection image Pt formed on a sheet P, which is an example of a medium, as shown in FIG. 3, and calculates the edge blur of the image data and the line width of the inspection image. Then, referring to the line width correction table TB1 shown in FIG. 5 with the calculated two values of edge blur and line width, the corrected line width value is obtained from the line width correction table TB1, and the inspection is performed based on the edge blur. The exact line width of the image Pt is obtained.

  The image inspection apparatus 1A includes a detector 2A that reads the inspection image Pt shown in FIG. 3, a conveyance device 3A that conveys the paper P on which the inspection image Pt is formed, and an image obtained by reading the inspection image Pt with the detector 2A. A control device 4A for obtaining the edge blur value indicating the line width of the inspection image Pt and the sharpness of the image data from the data, and a storage device 5A for storing a line width correction table and the like are provided.

  The detector 2A is an example of detection means. In this example, the detector 2A includes a light emitting element and a light receiving element (not shown), and the light emitted from the light emitting element and reflected by the paper P is received by the light receiving element. In the paper P on which an image is formed, when the image is formed in black, the reflectance of light is different between an image forming position called a black solid portion and an image non-forming position called a paper white portion.

  Thereby, the inspection image Pt is read by the detector 2A while the sheet P on which the linear inspection image Pt shown in FIG. 3 is formed is conveyed by the conveying device 3A in a direction orthogonal to the inspection image Pt. As shown in FIG. 4, at the formation position of the inspection image Pt, which is the black solid portion B having a low reflectance, at the Hi level where the potential is high, and at the non-formation position of the inspection image Pt, which is the paper white portion W having a high reflectance. The image data D is obtained with a signal waveform whose potential is low level. In FIG. 4, the horizontal axis indicates the passage of time, and the vertical axis indicates the potential corresponding to the reflectance.

  3 A of conveyance apparatuses are examples of a conveyance means, and are provided with the conveyance roller 30 provided with a pair of drive roller and driven roller which pinch | interpose the paper P, and the conveyance motor 30M which drives the conveyance roller 30. FIG. Note that the inspection image Pt may be read by relative movement of the paper P and the detector 2A by moving the detector 2A while fixing the position without conveying the paper P.

  The control device 4A is an example of a control unit, and obtains the line width of the inspection image Pt from the image data D acquired by the detector 2A and obtains the edge blur that causes the line width error. The control device 4A calculates a line width detection threshold Th1 from the image data D acquired by the detector 2A in order to obtain the line width of the inspection image Pt. The line width detection threshold Th1 is 60% of the peak of the image data D in this example, assuming that the potential at the paper white portion W is 0% and the peak potential at the black solid portion B is 100%. The line width detection threshold Th1 is not limited to this value.

  The line width t1 of the inspection image Pt corresponds to a distance d1 between two intersections where the image data D and the line width detection threshold Th1 intersect. Therefore, the control device 4A calculates the position of one intersection P1 where the image data D and the line width detection threshold Th1 intersect and the position of the other intersection P2. In FIG. 4, the horizontal axis indicates the passage of time, and the intersection P1 is obtained by multiplying the relative speed between the sheet P and the detector 2A, in this example, the conveyance speed of the sheet P, by the time from the intersection P1 to the intersection P2. To the intersection point P2 is obtained. This distance d1 is the line width t1 of the inspection image Pt.

  When the inspection image Pt is read by the detector 2A, if the distance between the detector 2A and the paper P deviates from a predetermined reference position, the rising edge portion that rises from the Low level to the Hi level in the image data D At E1, the rising angle becomes gentle and the sharpness of the image data is lowered. The same applies to the falling edge portion E2 falling from the Hi level to the Low level.

  As described above, the line width t1 of the inspection image Pt is obtained by the distance d1 between two intersections between the image data D and the line width detection threshold Th1. For this reason, the magnitudes of the slopes of the rising edge portion E1 and the falling edge portion E2 of the image data D cause an error in the line width t1 of the inspection image Pt.

  The magnitude of the inclination of the rising edge E1 is indicated by the distance between the image data D in the rising edge E1 and two intersections where two thresholds having different values intersect. This distance is called edge blur. The same applies to the falling edge E2.

  The control device 4A calculates a lower limit threshold Th2 and an upper limit threshold Th3 from the image data D acquired by the detector 2A in order to obtain edge blur. In this example, the lower limit threshold Th2 is 10% of the peak of the image data D and the upper limit threshold Th3 is 90% of the peak of the image data D. However, the value of each threshold is not limited to this.

  The control device 4A calculates an intersection point P3 where the image data D and the lower limit threshold Th2 intersect at the rising edge E1, and an intersection point P4 where the image data D and the upper limit threshold Th3 intersect. Then, by multiplying the conveyance speed of the paper P by the time from the intersection point P3 to the intersection point P4, the distance d2 from the intersection point P3 to the intersection point P4 is obtained as the value of the edge blur at the rising edge portion E1.

  In addition, the control device 4A calculates an intersection point P5 where the image data D and the upper limit threshold Th3 intersect at the falling edge portion E2, and an intersection point P6 where the image data D and the lower limit threshold Th2 intersect. Then, by multiplying the conveyance speed of the paper P by the time from the intersection point P5 to the intersection point P6, the distance d3 from the intersection point P5 to the intersection point P6 is obtained as the value of the edge blur at the falling edge portion E2. In this example, an average d4 (d4 = (d2 + d3) / 2) of the distance d2 and the distance d3 is set as an edge blur value in the image data D.

  The storage device 5A is an example of a storage unit, and stores a line width correction table TB1 shown in FIG. The line width correction table TB1 is created in advance based on experimental data. For example, the edge blur d4 and the line width t1 are obtained by reading at least one inspection image Pt that matches the line width of the inspection target while varying the distance between the paper P and the detector 2A, and the edge blur and the line width are actually measured. The line width correction table TB1 is created by storing the value and the actual line width of the inspection image in association with each other. In the line width correction table TB1, the actual line width is uniquely determined from the combination of the edge blur actual measurement value B1 and the line width actual measurement value B2.

  The control device 4A obtains the edge blur d4 and the line width t1 from the image data D acquired by reading the inspection image Pt, refers to the line width correction table TB1 with the actual values of the edge blur d4 and the line width t1, and corrects the line width. The corrected line width value is acquired from the table TB1, and the actual line width t1 of the inspection image Pt is obtained.

<Operation Example of Image Inspection Apparatus of Present Embodiment>
FIG. 6 is an explanatory diagram showing an example of the operation of the image inspection apparatus of the present embodiment, and FIG. 7 is an explanatory diagram showing the relationship between edge blurring and line width. As shown by a one-dot chain line in FIG. 1B, when the distance between the detector 2A and the paper P deviates from the reference position due to the paper P being bent or the like, as shown in FIG. 7, the edge blurs d2 ₂ and d3 ₂ is larger than the edge blurs d2 ₁ and d3 ₁ when the distance between the detector 2A and the paper P is the reference position. The same applies to the result of calculating the average of edge blurring on the rising edge portion E1 side and the falling edge portion E2 side.

On the other hand, the value d1 ₂ obtained as a line width t1 is smaller than the original value d1 ₁ line width of the test image Pt. For this reason, if the distance between the detector 2A and the paper P changes, the line width of the inspection image Pt cannot be obtained accurately.

  Therefore, the control device 4A reads at least one inspection image Pt formed with the same line width in the sub-scanning direction along the relative movement direction of the paper P and the detector 2A with the detector 2A and reads the image data. D is obtained, and an edge blur d4 and a line width t1 are obtained from the image data D. The control device 4A refers to the line width correction table TB1 with the actually measured values of the edge blur d4 and the line width t1, obtains the corrected line width value from the line width correction table TB1, and performs an actual line of the inspection image Pt. The width t1 is obtained.

  Further, as shown in FIG. 6, a plurality of inspection images Pt formed with the same line width in the sub-scanning direction along the relative movement direction of the paper P and the detector 2A, in this example, shown in FIG. The four inspection images Pt (1) to Pt (4) are read by the detector 2A to acquire the image data D, and the edge blur d4 and the line width t1 are obtained from each image data D. The control device 4A refers to the line width correction table TB1 with the actually measured values of the edge blur d4 and the line width t1, acquires the corrected line width value from the line width correction table TB1, and each inspection image Pt (1). The actual line width t1 of ~ Pt (4) is obtained. Then, the control device 4A determines that the line width is correctly acquired if the actual line width t1 of the inspection images Pt (1) to Pt (4) is the same.

  In the above example, the line width of the inspection image Pt is obtained using the line width correction table TB1, but a conversion formula is obtained so as to obtain a result equivalent to the line width correction table TB1 based on experimental data in advance. Then, the actual values of the edge blur d4 and the line width t1 may be converted into values indicating the actual line width using a conversion formula.

<Example of Configuration of Image Forming Apparatus of Embodiment>
FIG. 8 is a configuration diagram illustrating an example of the image forming apparatus according to the present exemplary embodiment. In the image forming apparatus 10A of the present embodiment, the light amount of the laser diode that is the writing unit is set based on the line width obtained by reading the inspection image. In this case, if the line width of the inspection image cannot be obtained accurately, the light quantity of the laser diode cannot be set correctly. Therefore, by applying the image inspection apparatus 1A described above, the line width of the inspection image can be accurately obtained.

  First, the overall configuration of the image forming apparatus 10A will be described. The image forming apparatus 10A is an electrophotographic image forming apparatus such as a copying machine. In this example, a plurality of photoconductors face one intermediate transfer belt. This is a so-called tandem color image forming apparatus that forms a full-color image by arranging in the vertical direction.

  The image forming apparatus 10A includes an image forming unit 11, a paper transport unit 20, a fixing unit 31, a detector 2A, and a document reading unit 40.

  The image forming unit 11 is an example of an image forming unit, and forms an image forming unit 11Y that forms a yellow (Y) image, an image forming unit 11M that forms a magenta (M) image, and a cyan (C) image. And an image forming unit 11BK that forms a black (BK) image.

  The image forming unit 11Y includes a photosensitive drum Y, a charging unit 12Y disposed around the photosensitive drum Y, an optical writing unit 13Y having a laser diode 130Y, a developing device 14Y, and a drum cleaner 15Y. Similarly, the image forming units 11M, 11C, and 11BK are optical writing units having the photosensitive drums M, C, and BK and charging units 12M, 12C, and 12BK, and laser diodes 130M, 130C, and 130BK arranged around the photosensitive drums M, C, and BK. 13M, 13C, 13BK, developing devices 14M, 14C, 14BK and drum cleaners 15M, 15C, 15BK.

  The surface of the photosensitive drum Y is uniformly charged by the charging unit 12Y, and a latent image is formed on the photosensitive drum Y by scanning exposure by the laser diode 130Y of the optical writing unit 13Y. Further, the developing device 14Y develops the latent image on the photosensitive drum Y by developing with toner. Thereby, an image (toner image) of a predetermined color corresponding to yellow is formed on the photosensitive drum Y.

  Similarly, the surface of the photosensitive drum M is uniformly charged by the charging unit 12M, and a latent image is formed on the photosensitive drum M by scanning exposure by the laser diode 130M of the optical writing unit 13M. . Further, the developing device 14M develops the latent image on the photosensitive drum M by developing with toner. As a result, a toner image of a predetermined color corresponding to magenta is formed on the photosensitive drum M.

  The surface of the photosensitive drum C is uniformly charged by the charging unit 12C, and a latent image is formed on the photosensitive drum C by scanning exposure by the laser diode 130C of the optical writing unit 13C. Further, the developing device 14C develops the latent image on the photosensitive drum C by developing with toner. As a result, a toner image of a predetermined color corresponding to cyan is formed on the photosensitive drum C.

  The surface of the photosensitive drum BK is uniformly charged by the charging unit 12BK, and a latent image is formed on the photosensitive drum BK by scanning exposure by the laser diode 130BK of the optical writing unit 13BK. Further, the developing device 14BK develops the latent image on the photosensitive drum BK by developing with toner. As a result, a toner image of a predetermined color corresponding to black is formed on the photosensitive drum BK.

  The images formed on the photosensitive drums Y, M, C, and BK are sequentially moved to predetermined positions on the intermediate transfer belt 16 that is a belt-like intermediate transfer member by primary transfer rollers 17Y, 17M, 17C, and 17BK. Transcribed. The image composed of each color transferred onto the intermediate transfer belt 16 is transferred by the secondary transfer unit 18 to the paper P conveyed at a predetermined timing by the paper conveyance unit 2.

  In this example, the paper transport unit 20 includes a plurality of paper feed trays 21 and a paper feed unit 21 a that feeds the paper P stored in the paper feed tray 21. Further, the paper transport unit 20 includes a main transport path 23 through which the paper P fed from the paper feed tray 21 is transported, a reverse transport path 24 that reverses the front and back of the paper P, and a paper discharge through which the paper P is discharged. A tray 25 is provided.

  In the sheet conveyance unit 10, the reverse conveyance path 24 branches from the main conveyance path 23 on the downstream side of the fixing unit 31, and a switching gate 23 a is provided at a branch point of the main conveyance path 23 and the reverse conveyance path 24. In the image forming apparatus 10 </ b> A, an image is formed on the surface of the paper P that has been transported through the main transport path 23 and passed through the secondary transfer unit 18 and the fixing unit 31. When images are formed on both sides of the paper P, the paper P on which an image is formed on one side facing upward is transported from the main transport path 23 to the reverse transport path 24 and from the reverse transport path 24 to the main transport path 23. By being conveyed, the image forming surface faces downward. As a result, the paper P is turned upside down, and an image can be formed on the other side facing upward.

  The fixing unit 31 is an example of a fixing unit, and performs a fixing process for fixing the image on the paper P to which the image has been transferred. The fixing unit 31 transports the paper P and fixes the image on the paper P by performing pressure fixing with the pair of fixing rollers 32 and 33 and heat fixing with the fixing heater 34.

  The document reading unit 40 scans and exposes an image of the document with the optical system of the scanning exposure apparatus, reads the reflected light with a line image sensor, and obtains an image signal. The image forming apparatus 10A may have a configuration in which an automatic document feeder (not shown) that feeds a document is provided at the top.

  In this example, the detector 2A reads a predetermined inspection image from the sheet P on which the image is transferred by the secondary transfer unit 18 and the image is fixed by the fixing unit 31, and therefore, in this example, the main conveyance path 23 and the reverse conveyance path 24 The main transport path 23 is provided downstream of the branching point and upstream of the paper discharge tray 25. The detector 2 </ b> A may be an inline sensor that detects color information and reflectance information of an image formed by the image forming unit 11. Alternatively, the detector 2 </ b> A may be an optical sensor that detects reflectance information of an image formed by the image forming unit 11.

<Example of Control Function of Image Forming Apparatus of Present Embodiment>
FIG. 9 is a functional block diagram illustrating an example of a control function of the image forming apparatus according to the present embodiment, and FIG. 10 is an explanatory diagram illustrating an example of a line width correction table. Here, in FIG. 9, the operation of writing the inspection image, the operation of reading the inspection image to obtain the line width and the edge shift, and the operation of setting the light amount of the laser diode according to the line width obtained by reading the inspection image. A related control function will be described.

  The image forming apparatus 10A includes a control device 100 that performs a series of controls for feeding paper P, forming an image, and discharging the paper P, and a storage device 101 that stores a line width correction table and the like. The control device 100 is an example of a control unit, and includes a microprocessor called a CPU and an MPU, and a memory such as a RAM and a ROM.

  The normal operation of forming an image on the paper P by the image forming apparatus 10A will be described. The control device 100 controls the paper transport unit 20 to transport the paper P. The control device 100 controls the image forming unit 11 based on the image data acquired from the document by the document reading unit 40 or the image data acquired from the outside, and forms an image on the paper P. Further, the control device 100 controls the fixing unit 31 to fix the image on the paper P, and discharges the paper P on which the image is formed.

  FIG. 11 is an explanatory diagram illustrating an example of an inspection image. In the operation of setting the light amounts of the laser diodes 130Y, 130M, 130C, and 130BK, the control device 100 forms a plurality of inspection images Pt on the paper P by changing the light amounts of the laser diodes 130Y, 130M, 130C, and 130BK. In this example, the line widths of the four inspection images Pt (1) to (4) are different as shown in FIG. 10 by changing the light amounts of the laser diodes 130Y, 130M, 130C, and 130BK.

  The storage device 101 is an example of a storage unit, and stores line width correction tables TB2 (1) to (n) shown in FIG. The line width correction tables TB2 (1) to (n) are created in advance based on experimental data. For example, an inspection image Pt with different line widths is read while varying the distance between the paper P and the detector 2A, and the edge blur d4 and the line width t1 are obtained. The line width correction tables TB2 (1) to (n) are created for each line width by storing the actual line widths in association with each other.

  The line width of the inspection image Pt is determined by the light amount of the laser diode that forms the inspection image Pt. Thereby, in the line width correction tables TB2 (1) to (n), the actual line width is uniquely determined for each light amount of the laser diode from the combination of the measured value B1 of the edge blur and the measured value B2 of the line width.

  The control device 100 transports the sheet P on which the inspection image Pt is formed and fixed, to the detector 2A, and reads the inspection image Pt with the detector 2A. The control device 100 obtains the line width of each inspection image Pt and the edge blur from the image data D acquired by reading the inspection image Pt with the detector 2A. The control device 100 refers to the line width correction tables TB2 (1) to (n) with the actually measured values of the edge blur d4 and the line width t1, and corrects the line widths corrected from the line width correction tables TB2 (1) to (n). To obtain the actual line width t1 of the inspection image Pt. Then, the light amounts of the laser diodes 130Y, 130M, 130C, and 130BK are set to values that have a predetermined line width.

<First Example of Operation of Image Forming Apparatus of Present Embodiment>
FIG. 12 is a flowchart showing the flow of processing in the first operation example. The control device 100 forms a plurality of inspection images Pt on the paper P by changing the light amounts of the laser diodes 130Y, 130M, 130C, and 130BK in step SA1 in FIG.

  In the first operation example, one inspection image Pt (1) is formed with the first light amount L1, and one inspection image Pt (2) is formed with the second light amount L2 lower than the first light amount L1. To do. Similarly, one inspection image Pt (3) is formed with a third light amount L3 lower than the second light amount L2, and one inspection image Pt (4) with a fourth light amount L4 lower than the third light amount L3. ). In this example, since the laser diode light quantity is set in four stages, the line width correction table can be prepared and stored in advance in accordance with four different line widths. good. FIG. 10 shows one line width correction table corresponding to a certain line width.

  In step SA2 of FIG. 12, the control device 100 conveys the sheet P, on which the inspection images Pt (1) to Pt (4) shown in FIG. 11 are formed and fixed, to the detector 2A by the sheet conveying unit 20, and detects it. Each inspection image is read by the device 2A, and image data D as shown in FIG. 4 is obtained for each inspection image.

  In step SA3 of FIG. 12, the control device 100 calculates a line width detection threshold Th1 for each image data D, and as shown in FIG. 4A, two points of the image data D and the line width detection threshold Th1. The intersections P1 and P2 are calculated, and the line width of each inspection image Pt is obtained by multiplying the conveyance speed of the paper P by the time from the intersection P1 to the intersection P2.

  In addition, the control device 100 calculates the lower limit threshold Th2 and the upper limit threshold Th3 for each image data D, and as shown in FIG. An intersection point P4 between the image data D and the upper limit threshold Th3 is calculated. Then, the distance d2 corresponding to the edge blur at the rising edge E1 is obtained by multiplying the conveyance speed of the paper P by the time from the intersection P3 to the intersection P4.

  Furthermore, the control device 100 calculates an intersection point P5 between the image data D and the upper limit threshold Th3 and an intersection point P6 between the image data D and the lower limit threshold Th2 at the falling edge portion E2. Then, the distance d3 corresponding to the edge blur at the falling edge portion E2 is obtained by multiplying the conveyance speed of the paper P by the time from the intersection point P5 to the intersection point P6. In this example, the average d4 of the distance d2 and the distance d3 is the edge blur value in each image data D.

  At step SA4 in FIG. 12, the control device 100 refers to the line width correction tables TB2 (1) to (4) with the actual values of the edge blur d4 and the line width t1, and the line width correction tables TB2 (1) to (4). ) To obtain the actual line width t1 of the inspection images Pt (1) to Pt (4).

  FIG. 13 is an explanatory diagram showing the relationship between the light amount of the laser diode and the line width. By obtaining the line width for each inspection image Pt formed by varying the light amount of the laser diode, the light amount of the laser diode necessary for forming an image with a predetermined line width is recognized for each line width. The characteristic information of the light quantity and line width of the laser diode as shown in (a) and FIG. 13 (b) is acquired.

  In step SA5 of FIG. 12, the control device 100 sets the laser diode light quantity so as to have a predetermined line width based on the laser diode light quantity and line width characteristic information shown in FIGS. 13 (a) and 13 (b). To do. For example, if the target line width is 150 μm, the light quantity of the laser diode corresponding to this line width is obtained from FIGS. In this example, the laser light quantity of the laser diode is described as four stages, but any number of stages may be used as long as there are a plurality of levels.

  In the image forming apparatus 10A, if the line width of the inspection image Pt cannot be obtained accurately, the light amount of the laser diode cannot be set correctly, and the image becomes unclear due to the line becoming thicker or thinner during image formation. Therefore, the quality may be deteriorated.

  On the other hand, the line width of the inspection image Pt is obtained by referring to the line width correction tables TB2 (1) to (4) from the edge blur obtained from the image data D and the actually measured line width, thereby obtaining the inspection image Pt. The line width of can be obtained accurately. Since the line width of the inspection image Pt can be accurately obtained, the light amount of the laser diode necessary for forming an image with a predetermined line width can be recognized, so that the light amount of the laser diode can be set correctly, The quality of image formation is stabilized.

<Second Operation Example of Image Forming Apparatus of Present Embodiment>
In the image forming apparatus 10A, the size of the edge blur determined from the image data D obtained by reading the image changes depending on the durability of the developer after long-term use and the environment in which the apparatus is installed.

  FIG. 14 is an explanatory diagram showing changes in edge blur due to developer durability. For example, when the image forming apparatus 10A is used and the developer is used for a long period of time, the toner charge amount is decreased and the scattering of lines is increased.

  For this reason, even if control is performed so as to form the same line width, image data D can be obtained with a signal waveform as shown by a solid line in FIG. 7 in the initial stage of use of the developer. When used, the value of the edge blur increases as shown by the alternate long and short dash line in FIG.

  As a result, as shown in FIG. 14, when the value of the distance deviation from the reference position between the paper P and the detector 2A is increased, the edge blur value is increased and the developer is compared with the developer durability initial stage. After endurance, the value of edge blur increases.

  FIG. 15 is an explanatory diagram showing changes in edge blur due to the environment. When the installation location of the image forming apparatus 10A is high temperature and high humidity, the toner charge amount decreases and the scattering of lines increases. For this reason, even if control is performed so as to form the same line width, the image data D can be obtained with a signal waveform as shown by a solid line in FIG. 7 in a general environment of medium temperature and low humidity. Then, as indicated by the alternate long and short dash line in FIG. 7, the value of the edge blur increases.

  As a result, as shown in FIG. 15, when the value of the distance between the paper P and the detector 2A from the reference position increases, the value of edge blur increases, and the high temperature and high humidity environment as compared with the general environment. Then, the edge blur value becomes large.

  In view of this, a line width correction table taking into consideration durability, use environment, and the like is created, and the line width correction table can be selected by setting the environment after the initial durability and after durability.

  FIG. 16 is an explanatory diagram illustrating an example of a line width correction table selected based on durability. The control device 100 of the image forming apparatus 10A selects the line width correction table TB3 (1) shown in FIG. On the other hand, the control device 100 measures the developer usage time and the like, and after the endurance when the developer usage time has reached a predetermined value, it corresponds to the increase in the value of edge blur shown in FIG. The line width correction table TB3 (2) is selected.

  After the endurance of the developer, the control device 100 measures the edge blur d4 and the line width t1 obtained from the image data D obtained by reading inspection images Pt (1) to Pt (4) as shown in FIG. 11, for example. The line width correction table TB3 (2) is referred to by value. Then, the control device 100 acquires the corrected line width value from the line width correction table TB3 (2), and obtains the actual line width t1 of the inspection images Pt (1) to Pt (4).

  As a result, the line width of the inspection image can be accurately obtained even after the developer has been endured. Although the developer has been described as an example of the element considering durability, other elements whose edge blur changes after the initial durability and after the durability may be used.

  FIG. 17 is an explanatory diagram showing an example of a line width correction table selected according to the environment. When the general environment is selected as the installation environment, the control device 100 of the image forming apparatus 10A selects the line width correction table TB4 (1) shown in FIG. In contrast, when the high-temperature and high-humidity environment is selected as the installation environment, the control device 100 selects the line width correction table TB4 (2) corresponding to the increase in the value of edge blur shown in FIG. .

  In a high-temperature and high-humidity environment, the control apparatus 100 measures the edge blur d4 and the line width t1 obtained from the image data D acquired by reading inspection images Pt (1) to Pt (4) as shown in FIG. The line width correction table TB4 (2) is referred to. Then, the control device 100 acquires the corrected line width value from the line width correction table TB4 (2), and obtains the actual line width t1 of the inspection images Pt (1) to Pt (4). Thereby, even in a high temperature and high humidity environment, the line width of the inspection image can be accurately obtained.

  Each line width correction table may be provided in consideration of both durability and installation environment. Moreover, you may correct | amend the value acquired with the line | wire width correction table using the correction coefficient according to durability and installation environment. Further, a line width detection threshold value that is a line width detection threshold Th1, a lower threshold value that is a lower threshold Th2, and an upper threshold that is an upper threshold Th3 are set to either durability or environment, or durability and environment. You may change based on both. The control device 100 changes each threshold, for example, at the initial stage of use of the developer and after the endurance. Moreover, each threshold is changed based on the setting of the installation environment.

  In each of the above embodiments, the inspection image is formed on paper. However, other paper-sheet-like media made of resin or the like may be used. But it ’s okay. If the surface of the medium is uneven, the distance between the detector and the medium changes, which causes a problem that the line width cannot be obtained accurately. Therefore, by applying the above-described present invention, a correct line width can be obtained.

  The present invention is applied to an image forming apparatus that obtains the line width of an image formed by a predetermined image writing output and sets the image writing output according to the line width.

  DESCRIPTION OF SYMBOLS 1A ... Image inspection apparatus, 2A ... Detector, 4A ... Control apparatus, 10A ... Image forming apparatus, 100 ... Control apparatus

Claims (8)

Detection means for optically reading a linear inspection image formed on the medium;
From the image data obtained by reading the inspection image with the detection means, the edge blur of the rising edge portion and the falling edge portion of the image data is calculated, the line width of the inspection image is calculated, and the edge blur and the line width are actually measured. Control means for obtaining the line width of the inspection image determined in accordance with the value ;
A line width correction table in which measured values of edge blur and line width and the actual line width of the inspection image are stored in association with each other,
The control means refers to the line width correction table with the measured values of edge blur and line width, obtains the corrected line width value from the line width correction table, and obtains the actual line width of the inspection image. An image inspection apparatus characterized by that. Image forming means for forming an image on a medium;
Detection means for optically reading an image formed on the medium;
From the image data acquired by reading the linear inspection image formed on the medium by the image forming apparatus with the detection means, the edge blur of the rising edge portion and the falling edge portion of the image data is calculated, and the inspection image A control means for calculating the line width and obtaining the line width of the inspection image determined in accordance with the edge blur and the actually measured value of the line width;
A line width correction table in which measured values of edge blur and line width and the actual line width of the inspection image are stored in association with each other,
The control means refers to the line width correction table with the measured values of edge blur and line width, obtains the corrected line width value from the line width correction table, and obtains the actual line width of the inspection image. An image forming apparatus . A plurality of the above-mentioned line width correction tables corresponding to edge blur that changes with durability,
The image forming apparatus according to claim 2, wherein the control unit selects the line width correction table according to durability . A plurality of the line width correction tables corresponding to edge blurring that changes in the environment,
The image forming apparatus according to claim 2, wherein the control unit selects the line width correction table according to an environment setting . The control means sets a line width detection threshold for obtaining a line width from image data obtained by reading an inspection image with the detection means, and an upper threshold and a lower threshold for obtaining edge blur. The image forming apparatus according to claim 2, wherein the image forming apparatus is changed based on any one of the environments or both durability and the environment . The said control means sets the output of the said image formation means which forms an image with the said line width based on the detection result of line width, The any one of Claims 2-5 characterized by the above-mentioned. Image forming apparatus. 7. The image formation according to claim 2 , wherein the detection unit is an inline sensor that detects color information and reflectance information of an image formed by the image formation unit. apparatus. The image forming apparatus according to claim 2 , wherein the detection unit is an optical sensor that detects reflectance information of an image formed by the image forming unit.

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