JP2002010034A - Method for detecting oblique feeding and original processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting oblique feeding capable of simply correcting the oblique feeding of an original in a higher accuracy while avoiding an increase in a cost of an apparatus and an increase in size of the apparatus. SOLUTION: The method for detecting the oblique feeding comprises the steps of reading a test chart in which detecting marks 31a and 31b are formed, and obtaining an angle θ indicating a gradient of the chart from a reading line L by using a difference between lengths (a) and (b) of a line segment to be cut in internal regions of the marks 31a and 31b on image data of the marks by the line L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document processing apparatus which is used in combination with an image forming apparatus or an image file apparatus having a copying function and is used in combination therewith to read a document, and a skew detection method in the document processing apparatus. Things.

[0002]

2. Description of the Related Art In recent image reading apparatuses, an automatic document feeder is widely used in combination. By using the image reading device and the automatic document feeder in combination, a reading operation in the document moving mode can be performed. In the reading operation in the original moving mode, a plurality of originals are placed on an original tray, and the originals on the tray are transported one by one to the original reading position by the automatic original transport device. Scan the original.

[0003] Documents not suitable for document transport (for example,
In reading a book or the like, use in the original fixed mode is also possible. In the reading operation in the fixed document mode, a document is placed on a platen and a line CCD (Charge Coupled De-
vice) is moved in the main scanning direction along the document table to read the document.

In such a document reading apparatus, normal reading may not be performed due to skew of the document during document conveyance, inclination of the reading means, and the like.

For example, in the original moving mode, a conveying roller arranged on both sides of the original is usually used as a conveying system for conveying the original. However, if there is a deviation in the conveying balance of these conveying rollers, the original is conveyed. The rotating force acts on the original, and the original is conveyed at an angle. That is, the document is skewed. In such a case, the amount of skew generated in the document accompanying the conveyance of the document increases, and the skew amount differs between the beginning and the end of reading. It will be read as a distorted shape.

Conventionally, various techniques have been tried to correct the skew of a document by detecting the amount of skew of the document while the document is being conveyed.

FIG. 8 is a diagram showing an example of an active registration mechanism employed in a conventional digital copying apparatus as a skew feeding correction mechanism of an automatic document feeder.

In the active registration mechanism, first and second registration rollers 102 and 103 for document conveyance are provided on a document table glass 101 on which a document is placed in pressure contact with the document table glass 101. , Each registration roller 1
02 and 103 are first and second skew corrections, respectively.
Are mounted on the registration motors 104 and 105. Below the platen glass 101, skew amount detection sensors 106 and 107 and a reading optical system (scanner unit) 108 are provided.

That is, the digital copying apparatus includes a document reading device, an automatic document feeder, and an image forming device that prints out image data of a document read by the document reading device. The automatic document feeder includes first and second registration rollers 102.
103 and the first and second registration motors 104.
05 active register mechanism. The document reading apparatus includes a document table glass 101, an optical system for guiding reflected light from the document, a lens for forming the reflected light on an image forming surface, and an electric signal for forming the image signal. And an image processing unit for processing the photoelectrically converted image signal, and are arranged below the automatic document feeder.

In general, a line CCD is used as a photoelectric conversion element in the image reading apparatus. The image forming apparatus includes a laser modulation unit that converts an image signal processed by the image processing unit into laser light and outputs the laser light, a discharge roller that discharges transfer paper, and a fixing mechanism that fixes a transferred image after transfer. And a photoconductor for forming a latent image, a developing mechanism for developing the latent image formed on the photoconductor, and a paper feed tray.

In the above-described configuration of the active registration mechanism, in the document movement mode in which the document is read while the document is automatically conveyed, first, the two skew amount detection sensors 106 are used.
The position of the leading end of the document (A shown in FIG.
By detecting the point and comparing the two values detected as the initial value with the value detected by one of the sensors, it is determined how much the leading end A is inclined with respect to the document conveying direction B.

For example, a value detected by the skew amount detection sensor 106 is used as an initial value, and the skew amount detection sensor 10
Assuming that the difference between the detection values 6 and 107 is + k, the document being conveyed is delayed by k points on the skew amount detection sensor 107 side by k points. In this case, in order to correct the delay amount, the rotation speed of the second registration motor 105 is controlled so as to increase the paper feed amount of the second registration roller 103 per unit time.

As described above, by controlling the paper feed amount per unit time of each of the first and second registration rollers 103 and 104, the original is centered on the nip with the rollers due to the unbalance of the feed amounts. , The skew of the document can be corrected.

If the time until the completion of this operation is set as the leading distance until the document reaches the reading position (scanner position), the image read by the scanner always has no skew with respect to the transport direction. .

In Japanese Patent Application Laid-Open No. 8-56280,
As shown in FIG. 9, a plurality of document detection sensors 111.
Within the document width of the minimum size (width guides 112, 112).
A method of detecting a skew of a document by arranging the document in parallel with the document reading line and monitoring a shift in the operation timing of the document detection sensors 111 accompanying the document conveyance.

When the skew is detected, the inclination angle θ of the leading end of the document
In response to this, the document reading start / end timing is changed, and the read image information is rotated in accordance with the skew amount.
Further, the conveyance state is corrected by changing the pressure distribution of the opposing rollers of the original conveying roller 113 or the relative position of the axis of the original conveying roller 113 and the axis of the opposing roller.

In the facsimile apparatus with a CCD correction function described in Japanese Patent Application Laid-Open No. 5-160969, when an original is set and an original reading operation is started as shown in FIG. During the feeding to the position, the skew amount is detected by the skew amount detection sensor 122, and the skew angle (correction angle) is calculated by the correction angle calculation unit 123 based on the detected amount and the document movement amount. Then, the CCD substrate is rotated by the CCD angle correction unit 124 by an amount corresponding to the skew angle to perform angle correction, and after the document and the CCD are set in the same direction, actual document reading is started.

[0018]

However, each of the above-mentioned conventional configurations has the following problems.

That is, in the active registration method, (1) the paper feed amount per unit time changes due to wear of the registration roller, and the skew correction ability decreases with time. Since the running distance is required, the time required to start reading the document is increased by that much, and the size of the apparatus is increased due to the increase in the document transport path. (3) To achieve high speed, complicated control is required. (4) Since the number of motors increases, cost and power consumption increase, and there is a problem that miniaturization of the apparatus is hindered.

In the method disclosed in Japanese Patent Application Laid-Open No. 8-56280, it is necessary to provide, for example, a reflection type photo sensor, a transmission type photo sensor with an actuator, a micro switch, etc. as means for detecting skew of a document. However, there is a problem that cost and power consumption increase, and miniaturization of the device is easily hindered.

The method disclosed in Japanese Patent Application Laid-Open No. 5-160969 also detects the skew of a document in the same manner as the active registration method. Since the first section of the original is required, there is a problem that the time required to start reading the original is increased by that much, and the apparatus is likely to be enlarged due to an increase in the number of original transport paths.

In the conventional skew detection described above,
The detected skew is a tilt of the document caused by a shift of the transport system when the document is used in the document moving mode in which the document is transported by the automatic document transport device, and the reading optical system is tilted with respect to the document reading direction. In some cases, this inclination amount cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to easily perform more accurate original skew correction while avoiding an increase in apparatus cost and an increase in apparatus size. The present invention provides a skew detection method and a document processing apparatus which can be performed in a timely manner.

[0024]

In order to solve the above-mentioned problems, a skew detection method according to the present invention reads a test chart on which a skew amount detection marking is formed by a document processing apparatus, and reads the test chart. Data is input as data, and the amount of skew generated in the document processing device is detected using the skew amount detection marking on the image data.

According to the above arrangement, in the document processing apparatus employing the above-described skew detection method, the test chart on which the skew amount detection marking of a predetermined shape is formed is read by the document reading sensor and the image data is read. Is used to control all operations of an image forming apparatus, an image filing apparatus, and the like to which the document processing apparatus is connected.
The processing is performed in a PU (Central Processing Unit) in the same flow as the image processing when a normal document is read. For this reason, a detection sensor for detecting the amount of skew is not required, so that an increase in the size and cost of the document processing apparatus can be avoided, and skew detection can be easily performed with a simple configuration.

In the conventional document processing apparatus, the skew detection is performed by using the skew detection sensor to directly detect the inclination of the document caused by the shift of the conveyance system when the document is used in the document movement mode in which the document is conveyed by the automatic document conveyance device. Since it is to be detected, it cannot detect anything other than the skew of the original by the transport system.

On the other hand, in the skew detection method of the present invention,
Since the relative inclination between the reading optical system and the test chart is detected, not only the skew of the original by the transport system but also the reading direction of the reading optical system in the original fixing mode or the original moving mode is used by using this inclination. Can also be detected, and skew detection with higher accuracy can be performed.

The inclination of the reading optical system with respect to the reading direction means a state in which the longitudinal direction of the reading line of the reading optical system and the reading direction are orthogonal to each other. . The reading direction is the main scanning direction of the reading optical system that scans the original in the original fixed mode, and the original transport direction of the original being transported in the original moving mode.

In the skew detection method, the test chart may include, as skew detection marks, a pair of detection marks of the same shape arranged symmetrically with respect to an axis parallel to the document reading direction. When a reading line passing through the same side corresponding to both detection markings is assumed, and the reading line does not tilt with respect to the document reading direction, the reading line is an internal area of each detection marking. If the length of the line segment cut off by the detection mark is equal and the reading line is inclined, the length of the line segment cut by one detection marking is long and the line segment cut by the other detection marking is long. The length of the read line is determined from the difference between the lengths of the line segments of the read line cut by the two detection markings. Calculating the relative inclination between the test chart, based on the tilt calculated it is preferable to have a structure for detecting the amount of skew caused by the document processing apparatus.

According to the above configuration, the following advantages can be obtained by using a pair of detection marks of the same shape arranged in line symmetry with respect to an axis parallel to the document reading direction.

That is, for a read line passing through the same side corresponding to both detection markings, the read line is cut out in each internal area of the detection mark, and the difference between the cut line segment lengths is calculated by skew detection. Although used in the process, the difference in the line segment length appears as a relatively large value even if the skew angle of the read line is small, so that an accurate calculation result can be obtained even if the inclination angle is minute. Further, the sign of the sign of the difference between the lengths of the cut line segments can be used to determine the rotation direction in the case where a tilt occurs.

In the skew detection method, the movable test optical system is scanned in the main scanning direction while the test chart is stationary so as not to be inclined with respect to the main scanning direction. When reading the test chart, the inclination of the reading line in the reading optical system with respect to the main scanning direction is calculated by calculating the relative inclination of the reading line with respect to the test chart, and the main scanning of the reading optical system is performed. A configuration in which the inclination with respect to the direction is detected as the skew amount can be adopted.

According to the above arrangement, in the document fixing mode in which the reading optical system scans the fixed document to read the document, the test chart and the reading optical signal are read in a state where the test chart is not inclined. By calculating the relative inclination with respect to the reading line in the system, the calculation result can be detected as the inclination of the reading optical system with respect to the main scanning direction (moving optical system skew amount).

Incidentally, the state in which the test chart has no inclination refers to a state in which the axis of symmetry of the skew amount detection marking in the test chart is completely parallel to the main scanning direction of the reading optical system.

In the above skew detection method, a pair of detection marks of the same shape arranged symmetrically with respect to an axis parallel to the original reading direction are used as the skew detection marks of the test chart. When reading the test chart by reading the test chart by transporting the test chart to a reading position opposed to a fixedly arranged reading optical system using a document having two pairs of the front end side and the rear end side in the document conveying direction, The relative inclination between the read line and the test chart when the skew amount detection marking on the leading end of the chart approaches the reading position, and the skew amount detection marking on the trailing end of the test chart are the reading position The relative inclination between the reading line and the test chart when approaching is calculated, and the inclination detected by the skew amount detection marking By dividing the difference from the inclination detected by the skew amount detection marking on the side by the distance in the document conveyance direction from the skew amount detection marking on the front end side to the skew amount detection marking on the rear end side. Alternatively, a configuration may be adopted in which the inclination of the document that occurs when the test chart is conveyed by a unit length is obtained, and the inclination of the document is detected as the skew amount.

According to the above configuration, the difference between the inclination detected by the skew amount detection marking on the front end side of the test chart and the inclination detected by the skew amount detection marking on the front end side is obtained. While the test chart is conveyed the distance in the document conveying direction from the leading edge side skew amount detection marking to the rear end side skew amount detecting marking, the skew amount of the document caused by the conveyance system is determined. You can ask.

Therefore, the difference between the inclination detected by the skew amount detection marking on the front end side and the inclination detected by the skew amount detection marking on the front end side is calculated from the skew amount detection marking on the front end side. By dividing by the distance in the document conveyance direction to the skew amount detection marking on the end side,
The inclination of the document generated when the test chart is conveyed by the unit length can be calculated, and the calculation result can be detected as the skew of the document generated by the conveyance system (the skew amount of the conveyance system).

In the skew detection method, when the test chart is read by transporting the test chart to a reading position opposed to a fixed reading optical system, the reading line of the reading optical system is By calculating the relative tilt with respect to the test chart, the tilt of the reading optical system with respect to the document transport direction is obtained, and the tilt of the reading optical system with respect to the document transport direction can be detected as a skew amount. .

According to the above arrangement, in the original moving mode in which the original is transported to the fixed reading optical system to the reading position facing the reading optical system and the original is read, the inclination of the test chart is reduced. In a state where there is no image, the relative inclination between the test chart and the reading line in the reading optical system is calculated.
Can be detected as

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 is a block diagram schematically showing a document processing apparatus to which the present invention is applied.

As shown in FIG. 2 (a), the original document processing apparatus uses an original reading apparatus 1 and an automatic original transport apparatus 2 in combination, and the automatic original transport apparatus 2 includes a hinge 3 Thus, the document reading apparatus 1 can be opened and closed. Opening / closing of the automatic document feeder 2 is detected by an opening / closing detection sensor 4.

In the above-described document processing apparatus, when the read document is conveyed by the automatic document feeder 2 and the reading operation is automatically performed (when used in the document moving mode), as shown in FIG. The read original is placed on the original tray 5. At this time, the document placement on the document tray is detected by the document placement detection sensor 6, and the document size is detected by the document width detection sensor 7 and the document length detection sensor 8.

At the time of reading a document, the document stopper 9 is opened, and the feeding of the document is started by driving the paper feed roller 10, the paper pickup claw 11, and the registration roller 12. The conveyed document passes between the first reading optical unit 13 and the second reading optical unit 14 that are arranged facing the front and back surfaces of the document, so that the front and back surfaces of the document are simultaneously read. The read original is discharged to the discharge tray 15.

A registration roller front sensor 16 is provided before the registration roller 12, a document leading edge detection sensor 17 is provided before the first reading optical unit 13, and a paper output sensor is provided after the second reading optical unit 14. A monitor 18 is provided to monitor the presence or absence of a document in the transport path.

Further, in the above-mentioned document processing apparatus, when the document processing apparatus is used in the document fixing mode, as shown in FIG. The original is placed so that the reading surface faces downward, and the original transport device 2 is closed. When reading is started, the first reading optical system 13 moves in the main scanning direction along the glass table 19 to read a document.

In the document processing apparatus, a reference white plate for performing shading correction on each of the first reading optical unit 13 and the second reading optical unit 14 is provided. For the first reading optical unit 13, the glass table 1
A first reference white plate 20 is provided on the upper surface side of 9, and a second reference white plate 21 is provided on the lower surface side of the glass table with respect to the second reading optical unit 14.

In the above-described document processing apparatus according to the present embodiment, there are the following four types of skew amounts to be detected. The tilt of the first reading optical system in the document fixing mode. In the document moving mode, skew of a document due to a conveyance deviation of the document conveyance system. In the document movement mode, the inclination of the first reading optical system for reading the front surface of the document. In the original moving mode, the second side for reading the back side of the original
The tilt of the reading optical system.

In the document processing apparatus, a test chart provided with a skew amount detection marking is read as a document, and the respective skew amounts are detected using the image data. The amount of skew can be detected without the need for a dedicated sensor for performing skew. As a result, the skew amount can be detected without increasing the size of the document processing apparatus.

[Embodiment 1] In Embodiment 1, a method for detecting the inclination of the first reading optical system in the original fixing mode will be described.

The skew amount in the document processing apparatus as described above generally indicates that the document is skewed due to a shift in the balance of the conveyance system when the document is conveyed. In the fixed mode, the document is not conveyed, so that the above-mentioned skew does not occur.

However, in the original fixing mode, the original is read by the first reading optical system 13 itself moving along the main scanning direction, and at this time, the reading line by the first reading optical system 13 is moved in the main scanning direction. It is assumed that the reading line is perpendicular to the direction. If the reading line is inclined, accurate reading cannot be performed. Therefore, here
The state in which scanning is performed while the reading line of the first reading optical system 13 is tilted is defined as skew of the moving optical system (moving optical system skew). That is, the inclination of the first reading optical system 13 during the skew of the moving optical system is the skew amount detected in the first embodiment.

A test chart as shown in FIG. 3 is used for detecting the skew amount when the moving optical system is skewed. In the test chart, a skew amount detection marking 31 is formed at the leading end thereof.

The skew amount detecting marking 31 is a pair of right-angled isosceles triangles symmetrically arranged with respect to a center line L parallel to the main scanning direction.
b, and each oblique side forms an angle of 45 ° with the main scanning direction and a direction orthogonal to the main scanning direction (the depth direction of the apparatus). In the detection markings 31a and 31b, two sides of the right-angled isosceles triangle that are orthogonal to each other are formed so as to be the most downstream side in the main scanning direction and the innermost side in the document width direction in each triangle. , And their lengths are each set to 10 mm.

When detecting the amount of skew of the moving optical system in the original fixing mode, the test chart shown in FIG.
As shown in FIG.
Scanning of the reading optical system 13 in the main scanning direction is performed, and document reading is performed. The test chart is placed on the glass table 19 manually by the user. At this time, the test chart is placed without inclination (that is, the center line L is parallel to the main scanning direction). To be mounted on a computer).

As described above, when the original is read by moving the first reading optical system 13 with respect to the test chart fixed on the glass table 19, the inclination of the first reading optical system 13 with respect to the main scanning direction. 4A, the reading line on the actual original is as shown in FIG. At this time, if the original reading device 2 does not recognize the inclination amount of the first reading optical system 13 and develops the image data with the inclination amount being 0, the developed image data is as shown in FIG. As shown, the original data is distorted.

Here, as shown in FIG. 4 (c), first, a line segment (shown by a broken line in FIG. 4 (c)) connecting the midpoints on the oblique sides of the detection markings 31a and 31b is shown. A midpoint M is defined, and a read line passing through the midpoint M is assumed. Then, in the read line passing through the midpoint M, consider a line segment cut out in the area inside the detection markings 31a and 31b.

When the first reading optical system 13 is not inclined, the reading line passing through the midpoint M completely matches the line connecting the midpoints on the oblique sides of the detection markings 31a and 31b. , The detection markings 31a and 31b
The line segment cut off in the area inside the circle has the same length on both sides of the detection markings 31a and 31b.

On the other hand, when the first reading optical system 13 is inclined, the read line passing through the midpoint M coincides with the line segment connecting the midpoints on the oblique sides of the detection markings 31a and 31b. Instead, in FIGS. 4 (c) and 4 (d), it becomes a line as shown by a solid line. Therefore, the line segment cut in the area inside the detection markings 31a and 31b has a difference in length on both sides of the detection markings 31a and 31b. FIG. 4C shows a read line on a real document, and FIG. 4D shows a read line on image data.

That is, in the image processing apparatus according to the present embodiment, the read line passing through the middle point M is
The difference between the lengths of the line segments cut out in the area inside a 31b is calculated, and the skew amount can be calculated based on the difference. The method for calculating the skew amount will be described below with reference to FIG.
Will be described.

First, the skew amount to be detected when the test chart is fixed, that is, in the original fixing mode, is the amount of inclination generated in the first reading optical system 13 with respect to the main scanning direction, as described above. The angle θ shown in FIG.

In FIG. 1, the detection markings 31a, 3
1b, in the hypotenuse of a right-angled isosceles triangle
Point to m₁, M_TwoAnd the point m₁And m_TwoStraight line connecting
Line L ₁And The straight line L₁Above, point m₁And m_Two
Is the middle point of M, and the read line passing through the middle point M is L_TwoToss
You. The reading line L_TwoAre the detection markings 31a and 31
The length of the line segment cut in the area inside b
A and b. The above m ₁, M_TwoThrough each of
Line L₁Is a reading line L_TwoIntersection with
And p₁, P_TwoAnd The reading line L
_TwoIs the smell of each of the detection markings 31a and 31b.
The point that intersects the innermost side in the paper width direction is q ₁, Q_Two
And

At this time, the distance between p ₁ and q ₁ and
The distance between p ₂ and q ₂ is equal to
And Further, the distance between p ₁ and m _{1 and} the distance between p ₂ and m
The distance is equal to ₂ , and this is f.

Here, the angle θ (deg) is defined by the points m ₁ and m
The distance between the _two (here, 250 mm) and the length of d in the figure are represented by tan θ = 2d / 250, and if d is obtained, the angle θ can be obtained.

Also, in FIG. 1 described above, the angle θ is written relatively large for the sake of explanation. However, in practice, the angle θ is very small, and when the angle θ is a very small angle, the hatched area in FIG. The hatched triangle is approximated as a right-angled isosceles triangle with d ≒ e and d ≒ f, which is 2d ≒ e + f.

On the other hand, as is clear from FIG. 1, e = a−
c, f = c−b, and thus 2d = ab.

[0067] Here, the a and b, respectively, the reading line L ₂ is the number of pixels line segments cut by the inner region of the front side of the detection markings 31a (hereinafter, the number of front-side marking pixels), and the rear side It is represented by a value obtained by multiplying the number of pixels of a line segment cut out by the internal area of the detection marking 31b (hereinafter, the number of rear-side marking pixels) by one pixel length. Therefore, from the above considerations, tan θ = {(number of front side marking pixels) − (number of rear side marking pixels)} × (1 pixel length) / 250, and the difference between the number of front side marking pixels and the number of rear side marking pixels is obtained. Is detected, the inclination amount of the first reading optical system 13 can be detected by the above calculation.

For example, the detection markings 31a, 31
When the distance between the midpoints of the oblique sides of b is 250 mm and the amount of skew (the skew angle) generated in the first reading optical system 13 is 1 °, no inclination occurs in the first reading optical system 13. In comparison with the case, in the front-side detection marking 31a, the length of the line segment cut by the internal area is (250/250).
2) × tan (1 °) = 2.182 mm longer, and the length of the line segment cut by the inner area of the rear-side detection marking 31b is reduced by 2.182 mm. For this reason,
The total skew amount is 4.364 mm. This corresponds to about 100 pixels in a device having a resolution of 600 dpi. In this way, the skew amount can be examined in pixel units.

In the above description, a pair of right-angled isosceles triangles symmetrically arranged with respect to a center line L parallel to the main scanning direction of the test chart are used as the skew amount detection markings 31. However, this has the following advantages.

First, as a first advantage, the read line is cut in the respective internal areas of the detection markings 31a and 31b, and the calculation is performed using the difference between the cut line segments. Since the difference in the minute length appears as a relatively large value even if the skew angle is small, an accurate calculation result can be obtained. Further, as a second advantage, the rotation direction in the case where the inclination occurs can be determined by the sign of the sign when the difference between the lengths of the cut line segments is obtained.

However, the shape of the skew amount detection marking 31 is not limited to the above-described right isosceles triangle, but may be other shapes as long as the following requirements are satisfied. . That is, the skew feed amount detection markings are a pair of markings of the same shape provided symmetrically with respect to a line, and when a reading line passing through the corresponding same side of both markings is assumed, the reading line is inclined. If not, the length of the line segment cut off by the internal area of the skew amount detection marking is equal,
If the reading line is inclined, the length of the line segment cut off by the one skew amount detection marking is long, and the length of the line segment cut off by the other skew amount detection marking Any shape may be used as long as it becomes shorter.

After the amount of skew of the moving optical system, that is, the inclination angle of the first reading optical system 13 is detected by the method of the first embodiment, the first reading optical system is used based on the detected angle. The skew correction can be performed by adjusting the inclination of the system 13 or by performing a rotation process in the image data according to the detection angle for each data of each read line.

[Embodiment 2] In Embodiment 2, a method for detecting a skew of a document caused by a deviation in the balance of the document transport system in the document moving mode will be described.

The skew amount detected in the second embodiment is, as shown in FIG. 5, the inclination of the original that occurs during the transportation of the original to be conveyed. Tend to increase. The skew amount of the document due to such a shift of the transport system (hereinafter referred to as the skew amount of the transport system)
Is detected using a test chart as shown in FIG. The test chart has skew amount detection markings 32 and 33 formed thereon.

The skew amount detecting markings 32 and 3
3 is a skew amount detection marking 32a, which is a pair of right-angled isosceles triangles symmetrically arranged with respect to a center line L parallel to the main scanning direction, similarly to the skew amount detection marking 31 in FIG. . 32b and skew amount detection marking 3
3a and 33b.

That is, the skew amount detection marking 3
2a and 32b, and the skew amount detection markings 33a and 32b
Each oblique side of 33b is 45 degrees with respect to the main scanning direction and a direction orthogonal to the main scanning direction (the depth direction of the apparatus).
At an angle of °. Further, two sides of the right-angled isosceles triangle that are orthogonal to each other are formed so as to be the most downstream side in the main scanning direction and the innermost side in the document width direction in each triangle, and their lengths are respectively set. It is set to 10 mm.

When detecting the skew amount of the transport system in the document moving mode, the test chart is automatically transported by the document transport device 1 from a state where the test chart is placed on the document tray, and the first reading optical device in the stationary state is read. System 13 (or the second
It is read by the reading optical system 14).

At this time, if a shift occurs in the transport system of the document transport device 1, even if the test chart placed on the document tray is normally placed without tilting, the test chart is not read at the document reading position. A relative inclination occurs between the chart and the first reading optical system 13 (or the second reading optical system 14).

Here, in the above-described test chart, the skew amount detecting marking 32 on the leading end side in the document conveying direction is used.
When the document approaches the document reading position, the relative inclination angle between the test chart and the first reading optical system 13 (or the second reading optical system 14) is detected by the same calculation as in the first embodiment. Is done. Also, when the test chart is further conveyed and the skew amount detection marking 33 on the rear end side in the document conveying direction approaches the document reading position, the test chart and the first reading optical system 13 (or A relative tilt angle with the second reading optical system 14) is detected.

At this time, the skew amount detection marking 32
The difference between the skew angle detected by the test chart and the skew angle detected by the skew amount detection marking 33 is determined by determining the distance between the skew amount detection marking 32 and the skew amount detection marking 33 by the test chart. This is the amount of skew caused by the shift of the transport system that occurs during transport. That is, the difference between the inclination angle detected by the skew amount detection marking 32 and the inclination angle detected by the skew amount detection marking 33 is calculated by using the skew amount detection marking 32 and the skew amount detection marking. By dividing by the distance in the document conveyance direction up to 33, the inclination of the document generated when the test chart is conveyed by the unit length is obtained, and this is detected as the above-described skew amount of the conveyance system.

After the skew amount of the transport system is detected by the method of the second embodiment, the transport system such as the transport rollers is adjusted in accordance with the detection result, and the transport balance of each transport roller is adjusted. Skew correction can be performed.

In addition, the skew of the transport system in the original moving mode may be skew in the form shown in FIG. 7 in addition to the form shown in FIG. The skewed original shown in FIG. 7 indicates a case where the original itself is not inclined but the original transport direction itself is inclined with respect to the normal transport direction.

The skew amount in this case can be detected by the following procedure using the test chart of FIG.

That is, when the test chart is conveyed and the skew amount detection marking 32 on the leading end side in the document conveying direction approaches the original reading position, the skew amount on the rear end side in the original conveying direction. At each time when the detection marking 33 approaches the document reading position,
For the line segment connecting the midpoints on the oblique sides of the two detection markings, the position of the midpoint M is counted from the fulcrum on the reading line including the midpoint M to determine the number of pixels, and the amount of skew is calculated. The inclination in the document conveying direction can be calculated from the difference in the number of pixels between the position of the midpoint M with respect to the detection marking 32 and the position of the midpoint M with respect to the skew amount detection marking 33.

The detection of the skew amount of the transport system in the second embodiment is performed by the first reading optical system 13 and the second reading optical system 14.
However, since the detection result is affected only by the shift of the transport system, the detection result is the same regardless of which optical system is used. It is sufficient that the line amount is detected by using one of the optical systems.

[Embodiment 3] In the third embodiment, in the original moving mode, the moving direction of the conveyed original is
A method for detecting skew when the reading line of the optical system for reading the original in a fixed state is inclined will be described.

In the document moving mode, the first reading optical system 13 (or the second reading optical system 14) itself is in a fixed state, and the document is conveyed to the fixed reading position of these reading optical systems. An original is read. At this time, the first reading optical system 13 (or the second reading optical system 1) is used.
It is assumed that the reading line according to 4) is orthogonal to the document conveying direction, and if the reading line is inclined, accurate reading cannot be performed. Therefore, here, the state where the reading line of the first reading optical system 13 (or the second reading optical system 14) is inclined with respect to the document conveying direction is referred to as skew of the fixed optical system (fixed optical system skew). Is defined. That is, the inclination of the first reading optical system 13 (or the second reading optical system 14) in the fixed state with respect to the document conveyance direction is the skew amount detected in the third embodiment.

For detecting the skew amount when the fixed optical system is skewed, the test chart shown in FIG. 3 may be used similarly to the detection of the skew amount of the moving optical system described in the first embodiment.
However, in the process of the third embodiment, the test chart is placed on the document tray 5 of the document feeder 1 and is conveyed to the document reading position by the document feeder 1.

When the test chart is conveyed and the marking 31 for detecting the amount of skew of the test chart comes to the document reading position facing the first reading optical system 13 (or the second reading optical system 14), the embodiment will be described. By performing the same processing as described in 1, the relative detection between the test chart and the first reading optical system 13 (or the second reading optical system 14) becomes possible.

Here, the relative detection between the test chart and the first reading optical system 13 (or the second reading optical system 14) is based on the fact that the amount of skew detected in the above processing is a fixed optical system. This is because the transport system skew amount described in the second embodiment may be included in addition to the skew amount. That is, since the skew of the fixed optical system is generated during use in the document moving mode, if the conveyance system is displaced in the document conveyance device 1, the amount of skew detected is fixed optical system. This includes both the system skew amount and the transport system skew amount, and it is not possible to detect only the fixed optical system skew amount.

Therefore, when detecting the amount of skew of the fixed optical system, it is necessary to first correct the skew of the transport system according to the method of the second embodiment. By performing the detection processing based on the test chart in a state where the conveyance system in the document conveyance device 1 is not shifted, it is possible to detect only the fixed optical system skew amount.

The skew amount of the fixed optical system is detected by using a test chart in which a skew amount detection marking 31 is formed on one side, using a first reading optical system 13 and a second reading optical system 1.
4, it is possible to detect the first reading optical system 13 and the second reading optical system 14 simultaneously by using a test chart in which the skew amount detection markings 31 are formed on both sides. Is also possible. This eliminates the need for reversing the test chart and setting it again, shortening the adjustment time,
Worker burden can be reduced.

After the amount of skew of the fixed optical system is detected by the method of the third embodiment, the first reading optical system 13 (or the second reading optical system) is determined based on the detected inclination angle of the optical system. 1
The skew correction can be performed by adjusting the inclination of 4) or by performing a rotation process in the image data according to the detection angle for each data of each read line.

[0094]

According to the skew detection method of the present invention, a test chart on which a skew amount detection marking is formed is read by a document processing apparatus and input as image data as described above. The skew amount generated in the document processing apparatus is detected by using the skew amount detection marking above.

Therefore, in a document processing apparatus employing the above-described skew feeding detection method, the processing process is performed by a CPU (Central Processing) which controls all operations of an image forming apparatus, an image file apparatus, and the like to which the document processing apparatus is connected. Unit), it can be performed in the same flow as image processing when a normal document is read, and a sensor for detecting the amount of skew is not required. And an increase in cost can be avoided, and skew detection can be easily performed with a simple configuration.

In the skew detection method described above, the relative inclination between the reading optical system and the test chart is detected.
Using this inclination, it is possible to detect not only the skew of the original by the transport system but also the inclination of the reading optical system with respect to the reading direction in the original fixed mode or the original moving mode. Can also be achieved.

In the skew detection method, the test chart may include, as skew detection marks, a pair of detection marks of the same shape arranged symmetrically with respect to an axis parallel to the document reading direction. If a reading line passing through the same side corresponding to both detection markings is assumed, and if the reading line does not tilt with respect to the document reading direction, the reading line is an internal area of each detection marking. If the length of the line segment cut off by the detection mark is equal and the reading line is inclined, the length of the line segment cut by one detection marking is long and the line segment cut by the other detection marking is long. The length of the read line is determined from the difference between the lengths of the line segments of the read line cut by the two detection markings. Calculating the relative inclination between the test chart, based on the tilt calculated it is preferable to have a structure for detecting the amount of skew caused by the document processing apparatus.

Therefore, a pair of detection marks of the same shape, which are arranged symmetrically with respect to an axis parallel to the document reading direction, are used. A line is cut in each internal area of the detection marking, and a difference in the length of the cut line segment is used in a calculation process of skew detection, whereby an accurate calculation result can be obtained even if the inclination angle is minute. Further, the sign of the sign of the difference between the lengths of the cut line segments can be used to determine the rotation direction in the case where a tilt occurs.

In the skew detection method, the movable reading optical system is scanned in the main scanning direction while the test chart is stationary so as not to be inclined with respect to the main scanning direction. When reading the test chart, the inclination of the reading line in the reading optical system with respect to the main scanning direction is calculated by calculating the relative inclination of the reading line with respect to the test chart, and the main scanning of the reading optical system is performed. A configuration in which the inclination with respect to the direction is detected as the skew amount can be adopted.

Therefore, in the original fixed mode in which the original is scanned by scanning the optical system with respect to the fixed original, the inclination of the reading optical system with respect to the main scanning direction (moving optical system skew amount) is detected. Can be.

In the skew detection method, a pair of identically-shaped detection markings arranged symmetrically with respect to an axis parallel to the document reading direction are used as skew detection marks in the test chart. When reading the test chart by reading the test chart by transporting the test chart to a reading position opposed to a fixedly arranged reading optical system using a document having two pairs of the front end side and the rear end side in the document conveying direction, The relative inclination between the read line and the test chart when the skew amount detection marking on the leading end of the chart approaches the reading position, and the skew amount detection marking on the trailing end of the test chart are the reading position The relative inclination between the reading line and the test chart when approaching is calculated, and the inclination detected by the skew amount detection marking By dividing the difference from the inclination detected by the skew amount detection marking on the side by the distance in the document conveyance direction from the skew amount detection marking on the front end side to the skew amount detection marking on the rear end side. Alternatively, a configuration may be adopted in which the inclination of the document that occurs when the test chart is conveyed by a unit length is obtained, and the inclination of the document is detected as the skew amount.

Therefore, in the original moving mode in which the original is conveyed to the fixed reading optical system to the reading position facing the reading optical system and the original is read, the test chart is conveyed by a unit length. The skew of the document caused by the transport system (the skew amount of the transport system)
Can be detected as

In the skew detection method, when the test chart is read by transporting the test chart to a reading position opposed to a fixedly arranged reading optical system, the reading line of the reading optical system is By calculating the relative tilt with respect to the test chart, the tilt of the reading optical system with respect to the document transport direction is obtained, and the tilt of the reading optical system with respect to the document transport direction can be detected as a skew amount. .

Therefore, in the original moving mode in which the original is conveyed to the fixed reading optical system to the reading position facing the reading optical system and the original is read, the inclination of the reading optical system relative to the original conveying direction (fixed) Optical system skew amount) can be detected.

[Brief description of the drawings]

FIG. 1 illustrates one embodiment of the present invention, and illustrates the principle of detecting a relative inclination between a test chart and a read line by using a skew amount detection marking on a test chart. FIG.

FIGS. 2A and 2B show a configuration example of a document processing apparatus according to the present invention, wherein FIG. 2A is an explanatory view schematically showing a side surface of the apparatus, and FIG.
FIG. 2 is an explanatory view schematically showing the front of the apparatus, and FIG. 2C is an enlarged view showing a schematic configuration of a document reading unit viewed from the front of the apparatus.

FIG. 3 is a plan view showing a test chart used in skew amount detection in Examples 1 and 3.

FIGS. 4A to 4D show distortion occurring in image data of a read document when a tilt occurs between a reading direction of a test chart and a reading line of a reading optical system. FIG.

FIG. 5 is an explanatory diagram illustrating an example of a skewed form of a document generated in a document moving mode.

FIG. 6 is a plan view illustrating a test chart used in skew amount detection according to the second embodiment.

FIG. 7 is a diagram illustrating a skewed form of a document generated in the document movement mode.
It is explanatory drawing which shows the example different from.

FIG. 8 is a perspective view showing an example of a conventional document skew feeding correction mechanism.

FIG. 9 is a plan view showing another example of the conventional document skew correction mechanism.

FIG. 10 is a plan view showing still another example of the conventional document skew correction mechanism.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 document reading device 2 document conveying device 13 first reading optical system 14 second reading optical system 31, 32, 33 skew amount detection marking 31 a, 31 b, 32 a, 32 b, 33 a, 33 b detection marking

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Okada 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Eiji Atsumi 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Takeshi Iwamoto 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation (72) Inventor Takayuki Fujiyama 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Sharp Corporation F-term (Reference) 2H076 AA58 BA45 BA63 BB05 BB10 BB12 EA24 3F048 AA01 AB02 BA20 CA06 CC05 DA06 DB01 EB23 5C062 AB05 AB17 AC02 AC55 AC65 5C072 AA01 AA03 BA01 BA02 BA04 NA01 RA03 RA18 XA01

Claims (6)

[Claims] An original processing apparatus reads a test chart on which a skew amount detection marking is formed, inputs the test chart as image data, and uses the skew amount detection marking on the image data to read the original document. A skew detection method comprising detecting a skew amount generated in a processing device. 2. The test chart according to claim 1, wherein the skew amount detection marking includes a pair of detection marks of the same shape arranged symmetrically with respect to an axis parallel to the original reading direction. Assuming a reading line passing through the corresponding side of the marking, if the reading line does not tilt with respect to the document reading direction, the length of the line segment cut off by the internal area of each detection marking if the reading line is not inclined. If the reading line is inclined and the reading line is inclined, the length of the line segment cut by one detection marking is long and the length of the line segment cut by the other detection marking is short. And the relative inclination between the read line and the test chart based on the difference in the length of the line segment of the read line cut by the two detection markings. 2. The skew detection method according to claim 1, wherein the skew amount generated in the document processing apparatus is detected based on the calculated inclination. 3. When reading the test chart by scanning a movable reading optical system in the main scanning direction while keeping the test chart stationary so as not to be inclined with respect to the main scanning direction, By calculating the relative inclination of the reading line in the reading optical system with respect to the test chart, the inclination of the reading optical system with respect to the main scanning direction is obtained, and the inclination of the reading optical system with respect to the main scanning direction is determined by the amount of skew. 3. The skew detection method according to claim 2, wherein the skew detection is performed. 4. A pair of detection marks of the same shape, which are arranged symmetrically with respect to an axis parallel to the document reading direction, as a skew amount detection marking of the test chart, are provided on the front end side in the document conveyance direction. When reading the test chart by transporting the test chart to a reading position opposed to a fixedly arranged reading optical system using a pair having two pairs at the rear end side, and obliquely moving the front end side of the test chart The relative inclination between the reading line and the test chart when the marking for detecting the amount approaches the reading position, and the reading when the marking for detecting the amount of skew on the rear end side of the test chart approaches the reading position. The relative inclination between the line and the test chart is calculated, and the inclination detected by the skew amount detection marking on the tip side and the skew amount detection marker on the tip side are calculated. By dividing the difference from the inclination detected by the distance in the document conveyance direction from the leading-side skew amount detection marking to the trailing-side skew amount detection marking, the test chart has a unit length. Find the inclination of the document that occurs during transport,
3. The skew detection method according to claim 2, wherein the skew of the document is detected as a skew amount. 5. When the test chart is read by transporting the test chart to a reading position opposed to a fixedly arranged reading optical system, a reading line in the reading optical system is relative to the test chart. 3. The skew feeding according to claim 2, wherein the skew of the reading optical system with respect to the document feeding direction is obtained by calculating the tilt, and the tilt of the reading optical system with respect to the document feeding direction is detected as a skew amount. Detection method. 6. A document processing apparatus which performs skew detection by applying the skew detection method according to any one of claims 1 to 5.