JP2021022885A - Reading device, image forming apparatus, and correction method - Google Patents

Abstract

To accurately detect and correct the feature quantity of reading means that changes in an arbitrary direction.SOLUTION: A reading device comprises: reading means that reads reflected light or transmitted light from an object; first detection means that detects a reading result based on image data obtained by reading a surface of the object with the reading means; second detection means that detects a feature quantity that changes in an arbitrary direction on the basis of the image data obtained by reading the surface of the object with the reading means; and correction means that corrects the reading result detected by the first detection means by using the feature quantity detected by the second detection means.SELECTED DRAWING: Figure 6

Description

The present invention relates to a reader, an image forming apparatus and a correction method.

Conventionally, in an image reading device, when the paper (object) to be read flutters in the depth direction, there is a problem that the reading result is deteriorated due to a change in the characteristics of the image reading device in the depth direction.

In Patent Document 1, the distance between the evaluation object and the image pickup means is specified from the image signal generated by the imaging means imaging the pattern projected on the evaluation object by the projection means, and the evaluation object is defined by the position adjusting means. A technique for adjusting the position of an imaging means is disclosed.

However, according to the conventional reading device, although it is possible to detect the feature amount changing in the reading depth direction, when the paper flutters in the depth direction, the distance between the projection means and the paper changes and the paper is projected onto the paper. The pattern changes from a predetermined pattern. Therefore, there is a problem that the change in the feature amount due to the change in the projection pattern and the change in the feature amount due to the change in the characteristic of the reading means cannot be separated, and the feature amount changing in the reading depth direction of the reading means cannot be detected accurately.

The present invention has been made in view of the above, and an object of the present invention is to accurately detect and correct a feature amount that changes in an arbitrary direction of a reading means.

In order to solve the above-mentioned problems and achieve the object, the present invention presents a reading means for reading reflected light or transmitted light from an object, and a reading result based on image data obtained by reading the surface of the object with the reading means. Based on the image data obtained by reading the surface of the object with the reading means, the first detecting means for detecting the feature amount changing in an arbitrary direction, and the second detecting means for detecting the feature amount. It is characterized by including a correction means for correcting a reading result detected by the first detection means using a feature amount.

According to the present invention, since the feature amount changing in an arbitrary direction of the reading means is detected and corrected on the surface of the object, the feature amount changing in an arbitrary direction of the reading means is accurately detected and corrected. It has the effect of being able to.

FIG. 1 is a diagram showing a configuration of an example of an image processing device according to the first embodiment. FIG. 2 is a diagram schematically showing the configuration of an image reading unit and an ADF. FIG. 3 is a diagram illustrating a transport gap in the image reading device. FIG. 4 is a diagram illustrating characteristic deterioration due to a transport gap in the image reading device. FIG. 5 is a block diagram showing an electrical connection of each unit related to image correction of the image reading unit. FIG. 6 is a diagram illustrating feature quantity detection in the depth direction. FIG. 7 is a diagram for explaining the feature amount detection result in the depth direction. FIG. 8 is a diagram showing an example of feature amount detection in the reading depth direction using the MTF characteristic by the second detection unit. FIG. 9 is a diagram exemplifying the configuration of the production printer according to the second embodiment. FIG. 10 is a configuration diagram schematically showing a reading device provided in the inspection device. FIG. 11 is a diagram showing an example of image formation in a production printer. FIG. 12 is a diagram showing an example in which the detection pattern is formed outside the actual use area. FIG. 13 is a diagram showing an example of forming a detection pattern according to the third embodiment. FIG. 14 is a diagram showing a detection example of the detection pattern according to the fourth embodiment. FIG. 15 is a diagram showing an example of distribution of reading values. FIG. 16 is a diagram showing a detection example according to the fifth embodiment. FIG. 17 is a diagram showing an example of distribution of reading values at the edge portion of the transfer paper or the original. FIG. 18 is a diagram illustrating a change in magnification in the reduction optical system. FIG. 19 is a diagram illustrating a reduction optical system and transfer paper variation. FIG. 20 is a diagram for explaining a problem when the magnification is changed. FIG. 21 is a diagram illustrating detection of a change in magnification according to the sixth embodiment. FIG. 22 is a diagram showing an example of forming a vertical line pattern outside the actual use area. FIG. 23 is a diagram showing an example of forming a vertical line pattern for detecting the magnification according to the seventh embodiment. FIG. 24 is a diagram showing a modified example of the formation position of the vertical line pattern for detecting the magnification. FIG. 25 is a diagram showing a detection example according to the eighth embodiment. FIG. 26 is a diagram illustrating a change in the amount of light due to the illumination depth characteristic. FIG. 27 is a diagram illustrating height detection due to a change in illuminance of the light source according to the ninth embodiment. FIG. 28 is a diagram illustrating an example of height detection due to a change in illuminance of a light source. FIG. 29 is a block diagram showing an electrical connection of each part related to image correction of the image reading unit according to the tenth embodiment. FIG. 30 is a diagram showing the relationship between the MTF characteristic and the reference position. FIG. 31 is a diagram illustrating a case where the reading magnification is detected in advance as a feature amount in the reading depth direction. FIG. 32 is a diagram illustrating a detection method in which a reference medium is provided in the apparatus according to the eleventh embodiment. FIG. 33 is a diagram illustrating detection of image position information according to the twelfth embodiment. FIG. 34 is a diagram showing the relationship between the MTF characteristic and the reference position. FIG. 35 is a diagram showing the relationship between the depth change and the magnification error. FIG. 36 is a diagram illustrating detection of color information according to the thirteenth embodiment. FIG. 37 is a diagram illustrating detection / correction of color information. FIG. 38 is a diagram illustrating a feature amount (conveying speed) that changes in the sub-scanning direction according to the fourteenth embodiment. FIG. 39 is a diagram illustrating a change in the scanned image due to a change in the transport speed. FIG. 40 is a diagram illustrating detection of the influence of a change in transport speed. FIG. 41 is a diagram illustrating correction of the influence of a change in transport speed.

Hereinafter, embodiments of a reading device, an image forming device, and a correction method will be described in detail with reference to the accompanying drawings.

(First Embodiment)
FIG. 1 is a diagram showing a configuration of an example of an image processing device 100 according to the first embodiment. In FIG. 1, the image processing device 100 that functions as an abnormal pixel detection device is an image forming device generally called a multifunction device (MFP) that has at least two functions of a copy function, a printer function, a scanner function, and a facsimile function. is there.

The image processing device 100 has an image reading unit 101 and an ADF (Automatic Document Feeder) 102, which are reading devices, and has an image forming unit 103 below the image reading unit 101. For the image forming unit 103, the outer cover is removed to show the internal configuration in order to explain the internal configuration.

The ADF 102 is a document support unit that positions a document (object) for reading an image at a reading position. The ADF 102 automatically conveys the document placed on the mounting table to the reading position. The image reading unit 101 reads the document conveyed by the ADF 102 at a predetermined reading position. Further, the image reading unit 101 has a contact glass on the upper surface, which is a document supporting portion on which the document is placed, and reads the document on the contact glass at the reading position. Specifically, the image reading unit 101 is a scanner having a light source, an optical system, and an image sensor such as a CCD (Charge Coupled Device) inside, and reads the reflected light of the document illuminated by the light source with the image sensor through the optical system. ..

The image forming unit 103 prints the original image read by the image reading unit 101. The image forming unit 103 includes a manual roller 104 for manually feeding the recording paper and a recording paper supply unit 107 for supplying the recording paper. The recording paper supply unit 107 has a mechanism for feeding out the recording paper from the multi-stage recording paper paper feed cassette 107a. The supplied recording paper is sent to the secondary transfer belt 112 via the resist roller 108.

The toner image on the intermediate transfer belt 113 is transferred to the recording paper carried on the secondary transfer belt 112 at the transfer unit 114.

Further, the image forming unit 103 includes an optical writing device 109, a tandem type image forming unit (Y, M, C, K) 105, an intermediate transfer belt 113, the secondary transfer belt 112, and the like. The image written by the optical writing device 109 is formed as a toner image on the intermediate transfer belt 113 by the image forming process by the image forming unit 105.

Specifically, the image forming unit (Y, M, C, K) 105 has four photoconductor drums (Y, M, C, K) rotatably, and a charging roller is formed around each photoconductor drum. , A developer, a primary transfer roller, a cleaner unit, and an image forming element 106 including a static eliminator, respectively. The image forming element 106 functions in each photoconductor drum, and the image on the photoconductor drum is transferred onto the intermediate transfer belt 113 by each primary transfer roller.

The intermediate transfer belt 113 is arranged on the nip between each photoconductor drum and each primary transfer roller by being stretched by a driving roller and a driven roller. The toner image primaryly transferred to the intermediate transfer belt 113 is secondarily transferred to the recording paper on the secondary transfer belt 112 by the secondary transfer device by running the intermediate transfer belt 113. The recording paper is conveyed to the fixing device 110 by the running of the secondary transfer belt 112, and the toner image is fixed as a color image on the recording paper. After that, the recording paper is discharged to the output tray outside the machine. In the case of double-sided printing, the front and back sides of the recording paper are reversed by the reversing mechanism 111, and the inverted recording paper is sent onto the secondary transfer belt 112.

The image forming unit 103 is not limited to the one that forms an image by the electrophotographic method as described above, and may be one that forms an image by an inkjet method.

Next, the image reading unit 101 and the ADF 102 will be described.

FIG. 2 is a diagram schematically showing the configurations of the image reading unit 101 and the ADF 102. As shown in FIG. 2, the image reading unit 101 includes a sensor substrate 10 having an image sensor 9 as an image sensor, a lens unit 8 for forming an image on the image sensor 9, a first carriage 6, and an image sensor 9 in the main body 11. It has a second carriage 7. The image sensor 9 is, for example, a CCD or a CMOS image sensor. The first carriage 6 has a light source 2 and a mirror 3 which are LEDs (Light Emitting Diodes). The second carriage 7 has mirrors 4 and 5. The reading unit 10 constituting the reading means of the present embodiment includes an image sensor 9 and a light source 2.

Further, the image reading unit 101 is provided with a contact glass 1 and a reference member 13 which is a reference white plate on the upper surface thereof. The reference member 13 is used for correcting various distortions in the reading optical system and the like. The image reading unit 101 also includes a contact glass 14 which is a sheet-through reading slit for reading the document conveyed by the ADF 102.

The ADF 102 is connected to the image reading unit 101 via a hinge or the like so that the contact glass 1 can be opened and closed.

The ADF 102 includes a document tray 15 as a document mounting table on which a bundle of documents composed of a plurality of documents can be placed. Further, the ADF 102 also includes a separating / feeding means including a feeding roller 16 that separates the originals one by one from the original bundle placed on the original tray 15 and automatically feeds them toward the contact glass 14.

Further, the ADF 102 is provided with the ADF background member 17 at a position facing the contact glass 14. The ADF background member 17 is configured so that the density in the main scanning direction is uniform.

In the image processing apparatus 100 configured as described above, in the scan mode in which the image surface of the document 12 is scanned to read the image of the document 12, the image reading unit 101 scans the first carriage 6 and the second carriage 7. Light is emitted upward from the light source 2 while moving from the standby position (home position) to the sub-scanning direction (A direction). At this time, in order to keep the optical path length from the contact glass 1 to the image sensor 9 constant, the second carriage 7 moves at half the speed of the first carriage 6. Then, the first carriage 6 and the second carriage 7 form an image of the reflected light from the document 12 on the image sensor 9 via the lens unit 8. Then, the signal is output by the photoelectric conversion of the image sensor 9, and is converted into a digital signal by the signal processing unit in the subsequent stage. As a result, the image of the document 12 is read and digital image data is obtained.

On the other hand, in the sheet-through mode in which the original is automatically fed and the image of the original is read, the image reading unit 101 moves the first carriage 6 and the second carriage 7 to the lower side of the contact glass 14. After that, the document placed on the document tray 15 of the ADF 102 is automatically fed by the feeding roller 16 in the arrow B direction (sub-scanning direction), and the image reading unit 101 refers to the document at the position of the contact glass 14. Light is emitted upward from the light source 2. Then, the first carriage 6 and the second carriage 7 form an image of the reflected light from the document on the image sensor 9 via the lens unit 8. Then, the signal is output by the photoelectric conversion of the image sensor 9, and is converted into a digital signal by the signal processing unit in the subsequent stage. As a result, the image of the original document conveyed by the ADF 102 is read, and digital image data is obtained. The original whose image has been read in this way is discharged to the ejection port.

The image reading unit 101 reads the reflected light from the reference member 13 by illumination by the light source 2 and sets a reference before reading the image in the scan mode such as when the power is turned on or in the sheet-through mode.

That is, the image reading unit 101 moves the first carriage 6 directly under the reference member 13 and turns on the light source 2 to form an image of the reflected light from the reference member 13 on the image sensor 9. The reflected light from the reference member 13 is converted into an analog signal by the image sensor 9, and is converted into a digital signal by the signal processing unit in the subsequent stage. As a result, the reference member 13 is read, and shading correction at the time of reading the image of the original is performed based on the reading result (digital signal).

Further, when the ADF 102 is provided with a transport belt, the ADF 102 can automatically feed the original to the reading position on the contact glass 1 and read the image of the original even in the scan mode.

In the present embodiment, the reading unit 10 is described as reading the reflected light from the object, but the present invention is not limited to this, and the reading unit 10 reads the transmitted light from the object. It may be.

Here, FIG. 3 is a diagram illustrating a transport gap in the image reader. In the image reading unit 101 described above, as shown in FIG. 3, there is a gap in the reading depth direction between the contact glass 14 which is a slit for sheet-through reading and the ADF background member 17. Due to the difference in characteristics in the reading depth direction, there is such a gap between when the original or output paper, which is the object, passes the lowermost part in the transport path (Pattern 1) and when it passes through the uppermost part (Pattern 2). , The reading result will be different. This point will be described in detail below.

FIG. 4 is a diagram illustrating characteristic deterioration due to a transport gap in the image reading device. For example, in FIG. 3, when the original is adjusted to the focus position that is most in focus (higher resolution) when the original is conveyed in pattern 1, when the original is conveyed in pattern 2. As shown in FIG. 4, the MTF characteristics are deteriorated, the resolving power of the read image is lowered, and the image becomes out of focus.

FIG. 5 is a block diagram showing an electrical connection of each unit related to image correction of the image reading unit 101. As shown in FIG. 5, the image reading unit 101 includes an image processing unit 22, a control unit 23, and a light source driving unit 24, in addition to the image sensor 9 and the light source 2 described above. The light source driving unit 24 drives the light source 2.

The control unit 23 controls each unit of the light source driving unit 24, the image sensor 9, and the image processing unit 22.

The image processing unit 22 includes a first detection unit 25, a second detection unit 26, and a correction unit 27. The image processing unit 22 may be realized by either hardware or software.

The first detection unit 25 detects the reading result based on the image data obtained by reading the surface of the object by the reading unit 10. In addition, the first detection unit 25 holds the detected reading result.

The second detection unit 26 detects a feature amount (MTF characteristic) that changes in the reading depth direction based on the image data obtained by reading the surface of the object by the reading unit 10.

The correction unit 27 uses the feature amount detected by the second detection unit 26 to correct the reading result detected and held by the first detection unit 25.

In the following, an example will be shown in which the second detection unit 26 detects a feature amount that changes in the reading depth direction using the MTF characteristic.

FIG. 6 is a diagram illustrating feature quantity detection in the depth direction. FIG. 6A is a diagram showing an example of a feature amount detection pattern. As shown in FIG. 6A, for example, a detection pattern P1 having four black vertical lines and a solid black portion is formed in advance on the reading surface of a white document which is an object.

FIG. 6B is a diagram showing reading of the detection pattern P1. As shown in FIG. 6B, the reading unit 10 reads the detection pattern P1 formed on the reading surface of the document at the timing when the document is conveyed to the reading position.

FIG. 7 is a diagram for explaining the feature amount detection result in the depth direction. As shown in FIG. 6B, the reading distribution when the detection pattern P1 (four vertical lines and the solid black portion) and the white part of the paper are read is as shown in FIG. 7. Assuming that the level of the white part is W, the level of the solid black part is W, and the difference between the MAX level and the MIN level when reading the vertical line is A,
MTF = A / (WB) x 100 (%)
Will be.

FIG. 8 is a diagram showing an example of feature amount detection in the reading depth direction using the MTF characteristic by the second detection unit 26.

According to the MTF calculation method described with reference to FIG. 7, the second detection unit 26 calculates the feature amount in the reading depth direction as the MTF. Since the second detection unit 26 detects the feature amount (MTF) on the reading surface (object surface) of the document which is the object, the detection error corresponding to the paper thickness which has occurred in the prior art does not occur. As shown in FIG. 8A, the feature amount originally desired to be detected (in the case of this example, the difference between the MAX level and the MIN level = A) can be detected.

The correction unit 27 performs a resolving force restoration process so that the MTF characteristics detected by the second detection unit 26 have a predetermined MTF. As a result, it is possible to correct an image whose characteristics have deteriorated due to fluttering in the depth direction and obtain a desired scanned image. Regarding the restoration process of the resolving power, the same process as the technique disclosed in Japanese Patent No. 5760426 may be performed.

As described above, according to the present embodiment, since the feature amount changing in the reading depth direction of the reading unit 10 is detected and corrected on the surface of the object, the reading depth of the reading unit 10 is corrected regardless of the paper thickness and the paper type. It is possible to accurately detect and correct the feature amount that changes in the direction.

As shown in FIG. 8B, even when a black document is used, the detection pattern P2 (four vertical lines and solid black portion) is formed of a white material so that the white document is black. The feature amount (MTF) in the reading depth direction can be detected in the same manner as when the detection pattern P1 is formed.

Further, in the prior art, an error occurs when the paper thickness of the paper changes, but in the present embodiment, when the original is attached to the contact glass 14 side and conveyed (FIG. 8 (c)), that is the case. Even in cases other than the above (FIG. 8 (d)), since the MTF is detected by forming a pattern on the surface of the original, the MTF characteristics on the surface of the original to be detected are detected, and even if the paper thickness of the original changes. It can be detected accurately without being affected.

Further, as shown in FIG. 4, assuming that the MTF is adjusted to the maximum (focus position) on the contact glass 14 side, the MTF is conveyed from the difference from the MTF detected as shown in FIG. It is also possible to detect the amount of fluttering of a document.

(Second Embodiment)
Next, the second embodiment will be described.

The second embodiment is different from the first embodiment in that a reading device is provided in the inspection device of the production printer. In the first embodiment, an example in which the image reading unit 101 of the MFP is applied as a reading device is shown, but the reading device is arranged in the inspection device of the production printer to inspect the printed image printed on the transfer paper. It may also be used for applications. In this case as well, the inspection result changes due to the characteristic change in the depth direction at the reading position due to the transport fluttering of the transfer paper. Therefore, the pattern shown in FIG. 6A is used to determine the feature amount in the depth direction. Detect and correct. Hereinafter, in the description of the second embodiment, the description of the same part as that of the first embodiment will be omitted, and the parts different from the first embodiment will be described.

FIG. 9 is a diagram exemplifying the configuration of the production printer 200 according to the second embodiment. As shown in FIG. 9, the production printer 200, which is an image forming apparatus for commercial printing, includes an image forming unit 201 and an inspection apparatus 202.

The image forming unit 201 forms an image on the entire surface of the A3 region using paper larger than A3 (SRA3 size, etc.) in order to finish the entire area of A3 without margins, and cuts off the margins.

The inspection device 202 is arranged after the output paper generated and output by the image forming unit 201. The inspection device 202 includes a reading device 203, scans the output paper, and detects the color and position of the printed image.

FIG. 10 is a configuration diagram schematically showing a reading device 203 provided in the inspection device 202. As shown in FIG. 10, the light source 2031, the first reflection mirror 2032, the second reflection mirror 2033, the third reflection mirror 2034, the image pickup element 2035, and the lens unit 2036 for forming an image on the image pickup element 2035 are provided. Further, the reading device 203 has a contact glass 204 on a transport path through which the output paper is conveyed, and a background member 205 having a reference member is arranged on the opposite side of the contact glass 204. The light source 2031 exposes the output paper located between the contact glass 204 and the background member 205.

The inspection device 202 reads the output paper conveyed by the reading device 203, detects the color and the image forming position of the image formed on the output paper, and feeds it back to the image forming unit 201.

In the present embodiment, the reading device 203 using the reduced optical system is shown as an example, but the present invention is not limited to this, and a 1x optical system or the like may be used.

FIG. 11 is a diagram showing an example of image formation in the production printer 200. In the first embodiment, the detection pattern P1 is formed in advance on the document to be read by the image reading unit 101. However, it is conceivable that forming the detection pattern P1 on the original is not allowed because the original image changes. In the present embodiment, as shown in FIG. 11, there is a margin (bleed area) outside the actual use area (outside the finished size area), which is the image forming portion of the transfer paper. Since the margin portion is cut after printing, by forming the detection pattern in the margin portion, it is possible to calculate the feature amount in the depth direction of the reading surface without giving the user the side effect of forming the detection pattern.

FIG. 12 is a diagram showing an example in which the detection pattern is formed outside the actual use area. Specifically, as shown in FIG. 12, a detection pattern P3 for MTF detection is formed outside the actual use area of the transfer paper (outside the finished size area, outside the A3 area in the example shown in FIG. 12) at the time of image formation. .. The reading device 203 reads the transfer paper image conveyed to the reading position. Then, the second detection unit 26 of the reading device 203 can detect the feature amount (MTF) in the depth direction on the reading surface in the same manner as in FIG. 7 by using the reading result. As a result, as shown in FIG. 8A, the detection error due to the paper thickness that has occurred in the prior art does not occur, and the feature amount that is originally desired to be detected can be detected.

As described above, according to the present embodiment, in the production printer 200 which is often used by cutting the margin portion, the detection pattern P3 for detecting the feature amount in the reading depth direction is formed in the margin portion, and the image forming unit 201 By reading the transfer paper with the reading device 203 arranged in the subsequent stage, it is possible to detect and correct the feature amount in the reading depth direction without giving a side effect to the user image.

Also in the image reading unit 101 of the MFP described in the first embodiment, the feature amount in the reading depth direction can be similarly detected by forming the detection pattern P1 in the margin portion of the document in advance. it can.

(Third Embodiment)
Next, a third embodiment will be described.

In the third embodiment, the detection pattern is formed of an invisible color material under visible light or a substantially invisible color material that is difficult for the human eye to recognize, which is a point of the first embodiment to the second embodiment. Different from. In the production printer 200, the transfer paper is often used in the manner shown in FIG. 11, but it does not necessarily have a margin (bleed area) on which a detection pattern can be formed. Further, when the reading device is used as the image reading unit 101 of the MFP as in the first embodiment, the detection when the detection pattern P1 cannot be formed on the document cannot be solved. In order to deal with such a case, the detection pattern is formed of an invisible color material under visible light or a substantially invisible color material that is difficult for the human eye to recognize. Hereinafter, in the description of the third embodiment, the description of the same part as that of the first embodiment to the second embodiment is omitted, and the description is different from the first embodiment to the second embodiment. The part will be described.

FIG. 13 is a diagram showing an example of forming a detection pattern according to the third embodiment. Specifically, as shown in FIG. 13A, for example, an invisible color material (for example, an invisible red toner that develops red color) that is invisible under visible light but emits a specific color when irradiated with ultraviolet light. A detection pattern P4 for MTF detection is formed on the transfer paper or the original.

In the present embodiment, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP can irradiate ultraviolet light, which is invisible light, in addition to normal visible light.

As shown in FIG. 13B, since the detection pattern P4 formed of the invisible color material is invisible under visible light, the user cannot normally recognize the detection pattern P4 formed of the invisible color material.

When a transfer paper on which the detection pattern P4 formed of the invisible color material is formed or a document on which the detection pattern P4 formed of the invisible color material is formed is read under visible light, as shown in FIG. 13 (c), a person The pattern on the transfer paper or the manuscript is read in much the same way as the eye recognition.

On the other hand, when the transfer paper on which the detection pattern P4 formed of the invisible color material is formed or the document on which the detection pattern P4 formed of the invisible color material is formed is read under ultraviolet light, as shown in FIG. 13 (d). , Only the detection pattern P4 from which the pattern is removed is detected.

At this time, when invisible red toner is used as the invisible color material, it emits red light by irradiation with ultraviolet light. Therefore, the image reading unit 101 and the reading device 203 of the MFP detect the colors (Red / Green / Blue) read by the image reading unit 101 and the reading device 203 of the MFP according to the color gamut in which the coloring material emits light. By selecting the color (selecting the reading result of Red), it can be detected with high accuracy.

As described above, according to the present embodiment, using the reading result obtained as described above, the feature amount (MTF) in the depth direction on the reading surface can be detected in the same manner as in FIG. 7, and FIG. Unlike (a), the detection error due to the paper thickness that has occurred in the prior art does not occur, and the feature amount that is originally desired to be detected can be detected.

In the present embodiment, as an invisible color material, a color material (invisible red toner) that becomes visible by irradiating ultraviolet light is mentioned, but the present invention is not limited to this, and a color material (IR) that becomes visible by irradiation with infrared light is used. Toner) may be used. When a color material that becomes visible by irradiation with infrared light is used, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP are invisible red in addition to normal visible light. Allows irradiation of external light.

In addition, when a low-density pattern is formed on the white part of the paper with a yellow color material, it is almost invisible to the human eye, and by forming the pattern on the left when printing an image, it is possible to determine which image forming device was used for printing. Although it is used as a tracking pattern, a detection pattern for MTF detection may be formed from a yellow color material and detected. In that case, it is desirable to detect with Blue, which is the complementary color of yellow.

(Fourth Embodiment)
Next, a fourth embodiment will be described.

The fourth embodiment is different from the first embodiment or the third embodiment in that a detection pattern simpler than a plurality of vertical lines and solid patterns is used. Hereinafter, in the description of the fourth embodiment, the description of the same part as that of the first embodiment to the third embodiment is omitted, and the description is different from the first embodiment to the third embodiment. The part will be described.

FIG. 14 is a diagram showing a detection example of the detection pattern P5 according to the fourth embodiment. As shown in FIG. 14A, this embodiment is an example of a simple detection pattern on a blank transfer paper or a reading surface of a document as a detection pattern for MTF detection on a transfer paper or a document. A black detection pattern P5 is formed. FIG. 14B shows the distribution of the readings of the portion indicated by the frame in the detection pattern P5 at this time.

On the other hand, FIG. 15 is a diagram showing an example of distribution of reading values. The example shown in FIG. 15 shows the distribution of the reading value when paying attention to the portion changed from black to white shown in the frame X1.

When the resolving power (MTF) is high, as shown in FIG. 15A, the black → white change changes sharply. In the example shown in FIG. 15A, black → white changes in two pixels.

On the other hand, when the resolving power (MTF) is low, the change from black to white becomes a gradual change as shown in FIG. 15 (b). In the example shown in FIG. 15B, black → white changes in 6 pixels.

For example, when the state shown in FIG. 15A is the target MTF characteristic, in the state shown in FIG. 15B, the MTF characteristic changes in the reading depth direction to obtain an out-of-focus image, and the image changes from black to white. Is gradual. Therefore, the correction unit 27 enhances the scanned image and corrects the scanned image so that the characteristics are the same as those shown in FIG. 15A.

As described above, according to the present embodiment, the second detection unit 26 arranges one patch on the reading surface of the paper for image reading, and detects the steepness of the black-and-white change of the reading result to obtain the depth. It is synonymous with detecting a change in resolution (MTF) in the direction, and can be detected as a feature amount that changes in the reading depth direction.

Further, by associating the steepness of the black-to-white change with the MTF in advance, it is possible to detect the amount of the scanned document or the transfer paper itself fluttering in the depth direction.

(Fifth Embodiment)
Next, a fifth embodiment will be described.

In the fifth embodiment, the point that the steepness of the level change from the paper background is detected from the reading result of the paper edge without forming a detection pattern is the point of the first embodiment to the fourth embodiment. Different from. In the fourth embodiment, an example is shown in which a detection pattern is formed on the paper to detect the steepness of the level change with the paper background, but the same thing can be said for reading the edge of the paper without forming the detection pattern. It can also be detected from the results. Hereinafter, in the description of the fifth embodiment, the description of the same part as that of the first embodiment to the fourth embodiment is omitted, and the description is different from the first embodiment to the fourth embodiment. The part will be described.

FIG. 16 is a diagram showing a detection example according to the fifth embodiment. In the present embodiment, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP make the ADF background member 17 at the reading position black. As shown in FIG. 16A, the present embodiment utilizes the black ADF background member 17 without forming a detection pattern for MTF detection on the transfer paper or the original. FIG. 16B shows the distribution of the readings of the portion indicated by the frame X2 in the vicinity of the edge of the white transfer paper or the original document at this time.

On the other hand, FIG. 17 is a diagram showing an example of distribution of reading values at the edge portion of the transfer paper or the original. The example shown in FIG. 15 shows the distribution of the reading value when paying attention to the change from black to white (the portion surrounded by the dotted line).

When the resolving power (MTF) is high, as shown in FIG. 17A, the black-to-white change changes sharply. In the example shown in FIG. 17A, black → white changes in two pixels.

On the other hand, when the resolving power (MTF) is low, the change from black to white becomes a gradual change as shown in FIG. 17 (b). In the example shown in FIG. 17B, black → white changes in 6 pixels.

For example, when the state shown in FIG. 17A is the target MTF characteristic, in the state shown in FIG. 17B, the MTF characteristic changes in the reading depth direction to obtain an out-of-focus image, and the image changes from black to white. Is gradual. Therefore, the correction unit 27 performs the enhancement processing of the scanned image and corrects it so that the characteristics are the same as those shown in FIG. 17A.

As described above, according to the present embodiment, the second detection unit 26 detects the change in resolution (MTF) in the depth direction by detecting the steepness of the black-and-white change at the edge of the transfer paper or the document for image reading. It is synonymous with the fact that it can be detected as a feature amount that changes in the reading depth direction.

Further, by associating the steepness of the black-to-white change with the MTF in advance, it is possible to detect the amount of the scanned document or the transfer paper itself fluttering in the depth direction.

(Sixth Embodiment)
Next, the sixth embodiment will be described.

The sixth embodiment is different from the first embodiment to the fifth embodiment in that a change in magnification is detected as a feature amount that changes in the depth direction. Hereinafter, in the description of the sixth embodiment, the description of the same part as that of the first embodiment to the fifth embodiment is omitted, and the description is different from the first embodiment to the fifth embodiment. The part will be described.

Here, FIG. 18 is a diagram for explaining a change in magnification in the reduction optical system, FIG. 19 is a diagram for explaining the reduction optical system and variation in transfer paper, and FIG. 20 is a diagram for explaining a problem when the magnification is changed.

When the reduction optical system method is used in the reading device 203 in the inspection device 202 of the production printer 200 or the image reading unit 101 of the MFP, when the transfer paper or the original conveyed at the reading position flutters in the depth direction, the reduction ratio of the read image Changes. FIG. 18 shows a change in the reading depth direction and a change in magnification when reading with a sensor (for example, an image sensor 9) having a resolution of 400 dpi and a pixel size of 4.7 μm. Further, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP are simulated.

For example, as shown in FIG. 19, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP have a transfer gap of 2 mm at the reading position, a sensor having a resolution of 400 dpi and a pixel size of 4.7 μm. When reading with (for example, the image sensor 9), what is read with a paper width of 330 mm when passing through the uppermost side of the transport gap (for example, the contact glass 14 side) is the lowest side of the transport gap (for example, the ADF background member). When passing through the 17 side), the scanned image is reduced by 0.25%.

Further, as shown in FIG. 20, when detecting the outer shape of the paper, it is read as a paper width of 329.2 mm, and a detection error of 0.8 mm occurs with respect to the paper width of 330 mm.

Therefore, in the present embodiment, the change in magnification is detected as a feature amount that changes in the depth direction.

FIG. 21 is a diagram illustrating detection of a change in magnification according to the sixth embodiment. As shown in FIG. 21, two vertical lines are provided in the transfer paper or the paper which is the original. The second detection unit 26 calculates the amount of change in the reading depth direction from the distance between the two lines.

More specifically, as shown in FIG. 21A, the vertical line pattern P6 is formed, for example, at a distance of 160 mm between the center and the vicinity of the end. The reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP read the paper on which the vertical line pattern P6 is formed.

The second detection unit 26 obtains the distance between the two vertical lines from the scanned image and calculates the magnification. Specifically, as shown in FIG. 21A, the second detection unit 26 identifies the pixel at the vertical line position from the transition of the reading value of the portion shown by the frame X3 of the paper, and the pixel a and the pixel b Calculate the distance between them and use it as the vertical line distance. When the reading resolution is 400 dpi,
(B-a) * 25.4 / 400
Can be calculated as.

As shown in FIG. 21B, if the distance between vertical lines is detected as 159.6 mm, the second detection unit 26 may detect that the distance between the vertical lines is 0.25% smaller than the original 160 mm. it can.

Further, from the relationship shown in FIG. 18, the second detection unit 26 can detect that the 2 mm paper is fluttering at the reading position when the magnification is changed by 0.25%.

The correction unit 27 performs a process of enlarging 0.25% with respect to the magnification detected as described above. As a result, it is possible to obtain a scanned image in which the characteristic change in the depth direction is corrected.

Further, by associating the relationship between the change in magnification and the reading depth as shown in FIG. 18, it is possible to detect the amount of fluttering of the conveyed paper.

As described above, according to the present embodiment, since the feature amount changing in the reading depth direction of the reading unit 10 is detected and corrected on the surface of the object, the reading depth of the reading unit 10 is corrected regardless of the paper thickness and the paper type. It is possible to accurately detect and correct the feature amount that changes in the direction.

Here, FIG. 22 is a diagram showing an example of forming a vertical line pattern outside the actual use area. As described with reference to FIG. 11, in the production printer 200, in order to obtain a finish without margins in the entire A3 region, an image is formed on the entire A3 region using paper larger than A3 (SRA3 size, etc.), and the margin portion is formed. There are many cases where it is used as a bleed.

Therefore, as shown in FIG. 22, a vertical line pattern P6 may be formed in a margin (bleed area) portion outside the actual use area (outside the finished size area), as in the detection pattern of FIG. As a result, since the portion where the vertical line pattern P6 is formed is cut after printing, it is possible to calculate the feature amount in the depth direction of the reading surface without giving the user the side effect of forming the vertical line pattern P6. Become.

As described above, in the production printer 200, which is often used by cutting the margin portion, a vertical line pattern P6 for detecting the feature amount in the reading depth direction is formed in the margin portion and arranged after the image forming unit 201. By reading the transfer paper with the reading device 203, it is possible to detect the feature amount in the reading depth direction without giving a side effect to the user image.

In the image reading unit 101 of the MFP described in the first embodiment, the feature amount in the reading depth direction can be similarly detected by forming the vertical line pattern P6 in advance in the original margin portion. it can.

(7th Embodiment)
Next, a seventh embodiment will be described.

In the seventh embodiment, the point that the vertical line pattern for detecting the magnification is formed of an invisible color material under visible light or a substantially invisible color material that is difficult for the human eye to recognize is the first to the first embodiment. It is different from the embodiment of 6. Hereinafter, in the description of the seventh embodiment, the description of the same part as that of the first embodiment to the sixth embodiment is omitted, and the description is different from the first embodiment to the sixth embodiment. The part will be described.

FIG. 23 is a diagram showing an example of forming the vertical line pattern P7 for detecting the magnification according to the seventh embodiment. Specifically, as shown in FIG. 23A, for example, an invisible color material (for example, an invisible red toner that develops red color) that is invisible under visible light but emits a specific color when irradiated with ultraviolet light. A vertical line pattern P7 for magnification detection is formed on the transfer paper or the original.

In the present embodiment, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP can irradiate ultraviolet light, which is invisible light, in addition to normal visible light.

As shown in FIG. 23B, since the vertical line pattern P7 for magnification detection formed of the invisible color material is invisible under visible light, the vertical line pattern P7 for magnification detection formed of the invisible color material is usually used. It cannot be recognized by the user.

When the transfer paper on which the vertical line pattern P7 for magnification detection formed of the invisible color material is formed or the document on which the vertical line pattern P7 for magnification detection formed of the invisible color material is formed is read under visible light, the figure is shown. As shown in 23 (c), the pattern of the transfer paper or the manuscript is read in almost the same manner as the human eye recognizes.

On the other hand, when a transfer paper on which a vertical line pattern P7 for magnification detection formed of an invisible color material is formed or a document on which a vertical line pattern P7 for magnification detection formed of an invisible color material is formed is read under ultraviolet light. , As shown in FIG. 23D, only the vertical line pattern P7 for magnification detection excluding the pattern is detected.

At this time, when invisible red toner is used as the invisible color material, it emits red light by irradiation with ultraviolet light. Therefore, the image reading unit 101 and the reading device 203 of the MFP detect the colors (Red / Green / Blue) read by the image reading unit 101 and the reading device 203 of the MFP according to the color gamut in which the coloring material emits light. By selecting the color (selecting the reading result of Red), it can be detected with high accuracy.

As described above, according to the present embodiment, the feature amount (magnification) in the depth direction on the reading surface can be detected in the same manner as in FIG. 21 by using the reading result obtained as described above.

Further, when an invisible color material is used as in the present embodiment, the vertical line pattern P7 for magnification detection formed on the paper is not limited to the margin portion as shown in FIG. 22, and anywhere on the paper. It may be formed. Here, FIG. 24 is a diagram showing a modified example of the formation position of the vertical line pattern P7 for detecting the magnification. As shown in FIG. 24 (b), since it is invisible and invisible to the human eye under visible light, it does not affect the user image, and as shown in FIG. 24 (d), by irradiating invisible light during reading. The vertical line pattern P7 for detecting the magnification can be detected.

In the present embodiment, as an invisible color material, a color material (invisible red toner) that becomes visible by irradiating ultraviolet light is mentioned, but the present invention is not limited to this, and a color material (IR) that becomes visible by irradiation with infrared light is used. Toner) may be used. When a color material that becomes visible by irradiation with infrared light is used, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP are invisible red in addition to normal visible light. Allows irradiation of external light.

In addition, when a low-density pattern is formed on the white part of the paper with a yellow color material, it is almost invisible to the human eye, and by forming the pattern when printing an image, a tracking pattern that determines which image forming device was used for printing. In the same way, a vertical line pattern P7 for detecting the magnification may be formed from a yellow color material and detected. In that case, it is desirable to detect with Blue, which is the complementary color of yellow.

(8th Embodiment)
Next, the eighth embodiment will be described.

The eighth embodiment is different from the first to seventh embodiments in that the change in magnification is detected from the reading result of the paper edge without forming the vertical line pattern for detecting the magnification. .. Hereinafter, in the description of the eighth embodiment, the description of the same part as that of the first embodiment to the seventh embodiment is omitted, and the description is different from the first embodiment to the seventh embodiment. The part will be described.

FIG. 25 is a diagram showing a detection example according to the eighth embodiment. In the sixth embodiment to the seventh embodiment, the vertical line pattern for magnification detection is formed to detect the feature amount (magnification) in the depth direction, but in the present embodiment, the vertical line pattern for magnification detection is detected. An example of detecting the change in magnification by detecting the edge of the transfer paper or the original without using the line pattern is shown.

In the example shown in FIG. 25A, the second detection unit 26 identifies pixels a and b corresponding to the edge of the paper from the transition of the reading value of the white transfer paper having a width of 330 mm or the paper which is the original, and pixels. The distance between a and pixel b is calculated, and the magnification error is detected. In the example shown in FIG. 25 (a), since the paper width detected by the second detection unit 26 is also 330 mm with respect to the paper width of 330 mm, the magnification error is 0, and the paper does not flutter in the reading depth direction. is there.

On the other hand, in the example shown in FIG. 25B, the second detection unit 26 calculates that the distance between the pixels c and the pixel d corresponding to the edge of the paper is 329.2 mm, which is 0.25% with respect to the paper width of 330 mm. It is detected that it is shrinking. In this case, it is possible to detect that the paper is fluttering by 2 mm in the depth direction at the reading position from the relationship shown in FIG. 18 as before.

As described above, according to the present embodiment, since the feature amount changing in the reading depth direction of the reading unit 10 is detected and corrected on the surface of the object, the reading depth of the reading unit 10 is corrected regardless of the paper thickness and the paper type. It is possible to accurately detect and correct the feature amount that changes in the direction.

(9th embodiment)
Next, a ninth embodiment will be described.

The ninth embodiment is different from the first to eighth embodiments in that a change in the amount of light from the light source is detected as a feature amount in the reading depth direction. Hereinafter, in the description of the ninth embodiment, the description of the same part as that of the first embodiment to the eighth embodiment is omitted, and the description is different from the first embodiment to the eighth embodiment. The part will be described.

FIG. 26 is a diagram illustrating a change in the amount of light due to the illumination depth characteristic. For example, in the image reading unit 101 of the MFP, the amount of light of the light source that exposes the paper within the transport gap changes. In the example shown in FIG. 26A, an example in which the transport gap is 2 mm is shown. As shown in FIG. 26B, in the case of a configuration in which the illuminance of the light source is maximized at a gap of 0 mm (14 contact glass surfaces), the illuminance of the light source is 5% at the position of the gap of 2 mm (ADF background member 17). descend.

That is, according to the example shown in FIG. 26, when the paper flutters on the contact glass 14 side and when it flutters on the ADF background member 17 side, a density difference of 5% occurs even if the same material is read. Will be done.

Hereinafter, a method of detecting and correcting a change in the amount of light from a light source as a feature amount in the reading depth direction will be described.

FIG. 27 is a diagram illustrating height detection due to a change in illuminance of the light source according to the ninth embodiment. In the example shown in FIG. 27 (a), an example in which the transport gap is 2 mm is shown. FIG. 27 (b) shows an example in which the illuminance on the document surface is reduced by 5% at the position of the transport gap of 2 mm, as in FIG. 26 (b). Therefore, when the paper is read using this light source, the same document is read at the position of the gap 0 mm (pattern 1 shown in FIG. 27 (a)) and the position of the gap 2 mm (pattern 2 shown in FIG. 27 (a)). In this case, as shown in FIG. 27 (c), a difference of 5% occurs in the reading level, similar to the change in the illuminance on the original surface.

The second detection unit 26 of the present embodiment detects a reading level decrease of 5% when the gap is 0 mm (pattern 1) and when the gap is 2 mm (pattern 2).

Specifically, the second detection unit 26 holds the reading level of a plurality of paper types at the gap 0 mm position acquired in advance by the reading unit 10. Then, when reading the corresponding paper type, the second detection unit 26 detects the amount of change in illuminance from the comparison between the reading level and the holding reading level. Further, the second detection unit 26 detects the amount of paper flutter at the reading position.

Here, FIG. 28 is a diagram illustrating an example of height detection due to a change in the illuminance of the light source. For example, as shown in FIG. 28, in the paper type A, when the reading level at the holding gap of 0 mm is 220 dig / 8 bit and the reading level read this time is 209 dig / 8 bit, the reading level is reduced by 5%. Therefore, the illuminance on the document surface is also reduced by 5%. Then, from the relationship shown in FIG. 27, the second detection unit 26 detects that the gap is 2 mm at the reading position.

As described above, in order to correct the reduction amount of 5% of the illuminance on the document surface detected by the second detection unit 26, the correction unit 27 has 220 with respect to the reading result held by the first detection unit 25. Multiplying / 209 (≈1.05%) is used as the corrected reading result.

As described above, according to the present embodiment, the MTF (sharpness of shading), the magnification error, and the illuminance of the light source are corrected by simultaneously detecting and correcting a plurality of three feature quantities in the reading depth direction. It is possible to correct a plurality of changes in the characteristics of the illuminance of the above, and it is possible to correct the reading result with less deterioration of the characteristics.

(10th Embodiment)
Next, the tenth embodiment will be described.

The tenth embodiment is the first embodiment in which the second detection unit 26 detects the relative difference from the reference value by holding the feature amount reference value in the reading depth direction in advance. Or different from the ninth embodiment. Hereinafter, in the description of the tenth embodiment, the description of the same part as that of the first embodiment to the ninth embodiment is omitted, and the description is different from the first embodiment to the ninth embodiment. The part will be described.

FIG. 29 is a block diagram showing an electrical connection of each part related to image correction of the image reading unit 101 according to the tenth embodiment. As shown in FIG. 29, the second detection unit 26 detects the relative difference from the reference value by holding the feature amount reference value in the reading depth direction in advance.

Here, FIG. 30 is a diagram showing the relationship between the MTF characteristic and the reference position. For example, when detecting the MTF characteristic as a feature amount, in the reading device 203 in the inspection device 202 of the production printer 200 or the image reading unit 101 of the MFP, the second detection unit 26 is at a reference position (position of a gap of 0 mm, FIG. 3). The MTF characteristic (50% in the case of FIG. 30A) in the pattern 1) in the above is acquired and retained in advance.

Then, when the MTF at the time of reading the transfer paper or the paper which is the original document conveyed to the image reading position as shown in FIGS. 6 to 8 is 35%, the second detection unit 26 performs FIG. 30 (a). ), By grasping the depth characteristics of the MTF in advance, it is possible to detect that the reading is performed at a position of a gap of 1.5 mm.

It is not always necessary to optimize the MTF at the reference position, and as shown in FIG. 30B, even if the MTF at the reference position deviates from the optimum value, the MTF at the reference position From the amount of change in MTF (20% in the case of FIG. 30B) detected as (45% in the case of FIG. 30B), the paper transport gap of 1.5 mm at the reading position can be detected.

Here, FIG. 31 is a diagram illustrating a case where the reading magnification is detected in advance as a feature amount in the reading depth direction. As another example of detecting the relative difference from the reference value by holding the feature amount reference value in the reading depth direction in advance, a case where the reading magnification is detected as the feature amount will be described.

For example, when the reading magnification is detected as a feature amount, in the reading device 203 in the inspection device 202 of the production printer 200 or the image reading unit 101 of the MFP, the second detection unit 26 is at a reference position (position of 0 mm gap, FIG. 3). The magnification error (magnification error 0% in the case of FIG. 31) in the pattern 1) in the above is acquired in advance and held.

Then, when the magnification error when reading the transfer paper or the paper which is the original, which is conveyed to the image reading position as shown in FIGS. 21 to 22, the second detection unit 26 is shown in FIG. As shown in 31, it is possible to detect reading at a position 1.6 mm from the reference position.

As in the case of detecting the MTF characteristic as a feature amount, it is not always necessary to set the magnification error to 0% at the reference position. For example, even if the magnification error at the reference position deviates from 0%, the paper at the reading position is calculated from the change amount of the magnification error at the reference position and the detected magnification error using the relationship shown in FIG. The amount of variation can be detected.

As described above, according to the present embodiment, the feature amount is detected as the amount of change from the reference value held in advance, so that the feature amount in the reading depth direction can be detected with high accuracy.

(11th Embodiment)
Next, the eleventh embodiment will be described.

In the eleventh embodiment, the point of detecting the relative difference from the reference value by providing a detection pattern for detecting the feature amount reference value in the reader is the first embodiment to the first embodiment. It is different from the embodiment of 10. Hereinafter, in the description of the eleventh embodiment, the description of the same part as that of the first embodiment to the tenth embodiment is omitted, and the description is different from the first embodiment to the tenth embodiment. The part will be described.

FIG. 32 is a diagram illustrating a detection method in which a reference medium is provided in the apparatus according to the eleventh embodiment. So far, an example in which the feature amount reference value is held in advance and the relative difference from the reference value is detected has been shown, but in the present embodiment, the detection pattern P8 is used as a reference medium for detecting the feature amount reference value. Is provided in the reader so as to detect the relative difference from the reference value.

Specifically, as shown in FIG. 32 (a), for example, the ADF background member 17 arranged to face the contact glass 14 at the reading position of the image reading unit 101 of the MFP is a rotating member which is a rotating body. In addition, the ADF background member 17 has a detection pattern (pattern shown in FIGS. 6 and 21) P8 on the surface for detecting the feature amount in the reading depth direction. When acquiring the feature amount reference value, the ADF background member 17 is controlled to be rotated to position the detection pattern P8 at the reading position as shown in FIG. 32 (a).

The second detection unit 26 calculates and holds the feature amount reference value from the reading result of the detection pattern P8.

Next, when reading the transfer paper or the paper that is the original material conveyed to the image reading position, the second detection unit 26 is formed on the paper reading surface as shown in FIG. 32 (b). The feature amount is detected from the detection pattern P9.

At this time, in order to prevent the detection pattern P8 on the ADF background member 17 from showing through when reading the paper, it is desirable to shift the detection pattern P8 on the ADF background member 17 from the reading position. The example shown in FIG. 32B shows an example in which the detection pattern P8 on the ADF background member 17 is shifted by 180 degrees from the reading position.

As described above, according to the present embodiment, the amount of change in the characteristic amount from the reference is detected from the amount of change in the amount of the feature amount detected in each of the ADF background member 17 and the paper reading surface, and the relationship shown in FIG. 30 is used. , It becomes possible to detect the amount of paper transport fluttering.

Further, according to the present embodiment, it is possible to reacquire the feature amount reference value at an arbitrary timing, such as acquiring each time the power is turned on in each device, and the individual difference of each device and the reading unit 10 over time can be obtained. Even when the characteristics change, by updating the feature amount reference value, it becomes possible to detect with higher accuracy than before.

Further, according to the present embodiment, when detecting a plurality of changes in MTF, magnification, and light intensity, a plurality of feature quantity reference values are prepared in the ADF background member 17 as shown in FIG. 32 (c). .. Then, the second detection unit 26 holds a plurality of feature amount reference values detected at arbitrary timings such as when the power of the device is turned on. By detecting the detection patterns P10 and P11 formed on the paper at the paper transport timing, the second detection unit 26 can detect a plurality of feature amounts.

(12th Embodiment)
Next, a twelfth embodiment will be described.

The twelfth embodiment is different from the first embodiment to the eleventh embodiment in that the image position information is detected. Hereinafter, in the description of the twelfth embodiment, the description of the same part as that of the first embodiment to the eleventh embodiment is omitted, and the description is different from the first embodiment to the eleventh embodiment. The part will be described.

FIG. 33 is a diagram illustrating detection of image position information according to the twelfth embodiment. As shown in FIG. 33, the second detection unit 26 estimates the outer shape of the object by detecting the position of the object (transfer paper) using a reading sensor (for example, an image sensor 9). More specifically, the second detection unit 26 estimates the outer shape by detecting the coordinates of the four corners of the transfer paper.

Further, the second detection unit 26 detects the position of the image pattern by using a reading sensor (for example, an image sensor 9). This is also estimated by detecting the coordinates of the four corners of the image pattern, similar to the outer shape of the transfer paper.

As described above, the reading device 203 in the inspection device 202 of the production printer 200 and the image reading unit 101 of the MFP detect the transfer paper position (outer shape) and the image pattern position, and correct the image pattern printing position on the transfer paper. To do.

However, when a reading device of a reduced optical system is used, the distance (a, b) in the main scanning direction, which is the detection position of the transfer paper or the image pattern, as shown in FIG. 33 due to the influence of the magnification error as shown in FIG. , C), an error occurs in the detection result.

Therefore, in order to correct the influence of the magnification error, the second detection unit 26 detects the detection pattern P3 for MTF detection as shown in FIG. 12, and from the relationship between the MTF characteristics shown in FIG. 30 and the reading depth direction. Calculate the amount of paper transport flutter.

Here, FIG. 34 is a diagram showing the relationship between the MTF characteristic and the reference position, and FIG. 35 is a diagram showing the relationship between the depth change and the magnification error. For example, it is assumed that the results of detecting the distances a, b, and c shown in FIG. 33 by the first detection unit 25 are a = 10 mm, b = 310 mm, and c = 320 mm.

When the detection pattern P3 as shown in FIG. 12 is formed when the paper is read and the MTF detected by the second detection unit 26 is 35%, the paper surface is from the 1.5 mm contact glass 14 due to the relationship shown in FIG. It means that they are being transported at distant positions.

Further, from the relationship shown in FIG. 35, it can be seen that when the paper passing through the position 1.5 mm away from the contact glass 14 is read, the magnification is reduced by 0.19%.

The correction unit 27 multiplies the position detection results a, b, and c read by reducing the size by 0.19% by 100 / (100-0.19), respectively, in order to correct the reduced amount. The correction unit 27 uses the calculation results (a = 10.02, b = 310.59, C = 320.61) as the image position detection result by the reading unit 10.

As described above, according to the present embodiment, it is possible to detect a highly accurate image position in which the characteristic change in the reading depth direction is corrected.

(13th Embodiment)
Next, the thirteenth embodiment will be described.

The thirteenth embodiment is different from the first embodiment to the twelfth embodiment in that color information is detected. Hereinafter, in the description of the thirteenth embodiment, the description of the same part as that of the first embodiment to the twelfth embodiment is omitted, and the description is different from the first embodiment to the twelfth embodiment. The part will be described.

FIG. 36 is a diagram illustrating detection of color information according to the thirteenth embodiment. For example, when the production printer 200 arranges the inspection device 202 after the image forming unit 201 in the production printer 200 and detects the color tone of the printed image, the image processing unit reads the result of reading the color pattern shown in FIG. Is converted from RGB to CMYK density and fed back to the image forming unit 201.

However, as described in FIG. 26, the characteristics of the illumination in the reading device 203 in the reading depth direction change due to the paper transport fluttering, so that an error occurs in the RGB values when the color pattern is read.

Therefore, in order to correct the influence of the change in the illumination characteristic, the second detection unit 26 detects the read RGB value of the paper background shown by the frame X4 in FIG. 36 to detect the change in the illumination characteristic.

The correction unit 27 corrects the reading result of the color pattern by using the detection result of the characteristic change of the illumination.

Here, FIG. 37 is a diagram illustrating detection / correction of color information. When reading the color pattern shown in FIG. 36, the reading value of the paper background (shown by the frame X4) detected by the first detection unit 25 is R / G / B = 190/192 as shown in FIG. 37 (a). It is assumed that the reading value of the / 195 digit and the yellow pattern (indicated by the frame X5) is R / G / B = 190/170/50 digit as shown in FIG. 37 (b).

Further, it is assumed that the reference value of the paper background held by the second detection unit 26 is R / G / B = 200/200/200 digit.

At this time, the second detection unit 26 detects that the illumination characteristics at the paper surface reading position are changed to 190/200 for R, 192/200 for G, and 195/200 for B due to the paper transport flutter. To do.

The correction unit 27 corrects the reading value of the yellow pattern by the change in the illumination characteristics. Specifically, the correction unit 27
R = 190 * 200/190 = 200 digit
G = 170 * 200/192 = 177digit
B = 50 * 200/195 = 51digit
Is corrected to obtain the color information detection result of the reading unit 10.

As described above, according to the present embodiment, highly accurate color detection can be performed by correcting the characteristic change in the reading depth direction.

(14th Embodiment)
Next, the fourteenth embodiment will be described.

The 14th embodiment is different from the 1st embodiment to the 13th embodiment in that the feature amount changing in the sub-scanning (paper transport direction) is detected. So far, an example of detecting and correcting a feature amount changing in the reading depth direction has been shown, but the detection of the feature amount is not limited to the depth direction. In this embodiment, an example of detecting and correcting a feature amount that changes in the sub-scanning (paper transport direction) is shown. Hereinafter, in the description of the fourteenth embodiment, the description of the same part as that of the first embodiment to the thirteenth embodiment is omitted, and the description is different from the first embodiment to the thirteenth embodiment. The part will be described.

FIG. 38 is a diagram illustrating a feature amount (conveying speed) that changes in the sub-scanning direction according to the fourteenth embodiment. FIG. 38 shows an example of the reading device 203 of the production printer 200. As shown in FIG. 38, the reading device 203 includes a first transport roller 2037 and a second transport roller 2038 for transporting the transfer paper upstream / downstream in the transfer paper transport direction at the reading position. The reading device 203 operates the first transport roller 2037 and the second transport roller 2038 at substantially the same speed. In the present embodiment, in order to smoothly convey the paper without slack, the reading device 203 operates the second downstream conveying roller 2038 at a slightly higher speed.

Here, FIG. 38 (a) shows a state (state 1) in which only the first transport roller 2037 is used for transport, and FIG. 38 (b) is a state in which both the first transport roller 2037 and the second transport roller 2038 are used for transport. (State 2) is shown, and FIG. 38 (c) shows a state (state 3) in which only the second transfer roller 2038 is used for transportation. The transport speeds of these three states are slightly different from each other.

To show a specific example, when the reading device 203 operates the first conveying roller 2037 at a linear speed of 400 mm / s to convey paper, the reading device 203 makes the second conveying roller 2038 about 0.5% faster at 402 mm / s. Operate at the transport speed. Therefore, in the state 1 of FIG. 38 (a), the paper is conveyed at a linear speed of 400 mm / s. Further, in the state 2 of FIG. 38 (b), the paper is conveyed at a linear speed of 401 mm / s in which the speeds of the first transfer roller 2037 and the second transfer roller 2038 are balanced. Further, in the state 3 of FIG. 38 (c), the paper is conveyed at a linear speed of 402 mm / s. The numerical value of the transport speed is a specific example, and is not limited to this.

FIG. 39 is a diagram illustrating a change in the scanned image due to a change in the transport speed. In the case of an operation such that the reading unit 10 reads at the same magnification at a linear speed of 400 mm / s, as shown in FIG. 39, the reading unit 10 reads the printed image at the same magnification in the state 1 and generates the read image, but in the state 2, the reading unit 10 generates the read image. The printed image is read at a speed of 400/401 = 0.9975 times, and a read image read with a reduction of 0.25% is obtained. In the state 3, the printed image is read at a speed of 400/402 = 0.995 times. The read image is reduced by 0.5% and the read image is obtained.

FIG. 40 is a diagram illustrating detection of the influence of a change in transport speed. Therefore, in the present embodiment, in the margin portion of the printed image, the pattern PT1 for detecting the transport speed is placed at a distance a from the paper tip, which is a portion corresponding to the switching of the transport state, at a distance a + b from the paper tip. The pattern PT2 for detecting the transport speed is formed as shown in FIG. 40.

The second detection unit 26 calculates the distance A of the detection pattern PT1 from the front end of the paper, the distance B of the detection pattern PT2 from the detection pattern PT1, and the distance C of the rear end of the paper from the detection pattern PT2, and the distance corresponding to each original state. By comparing with a, b, and c, the change in magnification in each state is detected.

Regarding the detection of the front / rear edge of the paper and the detection patterns PT1 and PT2, an example of detecting the edge of the paper and the detection pattern in the main scanning direction is described in FIGS. 22 and 25, but the sub-scanning is performed by the same method. It can be detected by applying it in the direction.

As described above, the second detection unit 26 has a = A (equal magnification) in the state 1, B / b = 0.9975 (0.25% reduction) in the state 2, and C / c = 0 in the state 3. Detects .995 (0.5% reduction).

FIG. 41 is a diagram illustrating correction of the influence of a change in transport speed. The correction unit 27 performs magnification processing on a region corresponding to each state of the scanned image according to the change in magnification in the sub-scanning direction in each state detected by the second detection unit 26.

FIG. 41 shows an example of correcting the magnification change detected in FIG. 40, but the same magnification processing is performed in the region corresponding to the state 1, and the 0.25% enlargement processing is performed in the region corresponding to the state 2. In the region corresponding to No. 3, 0.5% enlargement processing is performed.

As a result of the above, the corrected image becomes the same as the printed image of FIG. 40, and it is possible to obtain an image in which the influence of the magnification change generated by the change in the transport speed is corrected.

In the present embodiment, it is described that the feature amount changing in the sub-scanning direction is detected and corrected by taking the change in the conveying speed as an example, but the present invention is not limited to this, for example, paper conveying fluttering (resist deviation) in the main scanning direction. It can be applied in the same way to the correction of.

As described above, according to the present embodiment, it is possible to accurately detect and correct the feature amount that changes in the sub-scanning (paper transport direction).

In the above embodiment, an example in which the reading device of the present invention is applied to a multifunction device which is an image forming device having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function will be described. However, it can be applied to any image processing device such as a copier, a printer, a scanner device, and a facsimile machine.

10 Reading means 25 First detecting means 26 Second detecting means 27 Correcting means 100, 200 Image forming device 101, 203 Reading device 103, 201 Image forming unit

Japanese Unexamined Patent Publication No. 2006-279287

Claims (22)

A reading means that reads reflected or transmitted light from an object,
A first detection means for detecting a reading result based on image data obtained by reading the surface of an object with the reading means, and
A second detection means that detects a feature amount that changes in an arbitrary direction based on image data obtained by reading the surface of the object with the reading means.
A correction means for correcting the reading result detected by the first detection means by using the feature amount detected by the second detection means, and
A reading device comprising. The feature amount that changes in an arbitrary direction detected by the second detection means is a feature amount that changes in the reading depth direction.
The reading device according to claim 1. The feature amount detected by the second detecting means is a change in the reading resolution of the reading means.
2. The reading device according to claim 2. The second detecting means detects a change in the reading resolution of the reading means from a plurality of lines formed on the object.
The reading device according to claim 3. The plurality of lines formed on the object are arranged outside the real image forming region on the object.
The reading device according to claim 4. The plurality of lines formed on the object are formed by using an invisible or substantially invisible coloring material.
The reading device according to claim 4 or 5. The second detecting means detects a change in the reading resolution of the reading means from a change in the reading value at the boundary of an image having a large density change.
The reading device according to claim 3. The second detecting means detects a change in the reading resolution of the reading means from a change in the reading value at the end of the object.
The reading device according to claim 3. The feature amount detected by the second detecting means is a change in the reading magnification of the reading means.
2. The reading device according to claim 2. The second detecting means detects a change in the reading magnification of the reading means from the interline distance of a plurality of lines formed on the object.
9. The reading device according to claim 9. The plurality of lines formed on the object are arranged outside the real image forming region on the object.
10. The reading device according to claim 10. The plurality of lines formed on the object are formed by using an invisible or substantially invisible coloring material.
The reading device according to claim 10 or 11. The second detecting means detects a change in the reading magnification of the reading means from the distance between both ends of the object.
9. The reading device according to claim 9. The feature amount detected by the second detecting means is a change in the amount of light of the light source for exposing the object included in the reading means.
2. The reading device according to claim 2. The second detecting means detects a change in the amount of light of the light source for exposing the object from a change in the reading value of the object.
14. The reading device according to claim 14. The feature amount detected by the second detecting means is a change in the reading resolution of the reading means, a change in the reading magnification of the reading means, or a change in the amount of light of the light source for exposing the object provided by the reading means. Detect multiple,
2. The reading device according to claim 2. The feature amount detected by the second detection means is the amount of change from the reference value held in advance.
The reading device according to any one of claims 2 to 16. The feature amount detected by the second detection means is the amount of change from the reference value calculated by reading the reference medium provided in the apparatus.
The reading device according to any one of claims 2 to 16. The first detection means detects image position information on the object and
The correction means corrects the image position information on the object detected by the first detection means by using the feature amount detected by the second detection means.
The reading device according to any one of claims 1 to 18. The first detection means detects color information on the object and
The correction means corrects the color information on the object detected by the first detection means by using the feature amount detected by the second detection means.
The reading device according to any one of claims 1 to 18. The reading device according to any one of claims 1 to 20 and
Image forming part and
An image forming apparatus comprising. A correction method in a reading device including a reading means for reading reflected light or transmitted light from an object.
The first detection step of detecting the reading result based on the image data obtained by reading the surface of the object by the reading means, and
A second detection step of detecting a feature amount changing in an arbitrary direction based on image data obtained by reading the surface of the object with the reading means, and
A correction step for correcting the reading result detected in the first detection step using the feature amount detected in the second detection step, and a correction step.
A correction method characterized by including.

Images