JP2003276170A - Image recorder and method of detecting shift of angle of recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recorder that can accurately calculate an amount of shifted angle of a recording head based on a mutual relationship of test patterns even when the test pattern is contaminated, dust is stuck to the test pattern, or a trouble such as a broken nozzle, position shift in deposition or the like occurs. <P>SOLUTION: This image recorder 100 comprises a recording means for recording a pair of test patterns 312, 314 on a recording medium 192, a reading means for reading the pair of test patterns 312, 314 recorded by the recording means 192, and a calculating section 176 as a calculating means for calculating an amount of relative recorded position shift between the pair of test patterns 312, 314 based on density data of the pair of test patterns 312, 314 read by the reading means. The calculating means calculates the amount of relative recorded position shift of the pair of test patterns 312, 314 based on the mutual relationship of the density data of the pair of test patterns 312, 314, and then calculates the amount of shifted angle of the recording head based on the amount of relative recorded position shift. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus and a recording head angular deviation detecting method in the apparatus.

[0002]

2. Description of the Related Art An ink jet type image recording apparatus for forming an image by ejecting ink onto a recording medium is known. The ink jet type image recording device is, for example,
The recording head includes a large number of recording elements (inkjet nozzles) arranged in a line. An image recording apparatus of this type has one recording head for monochrome printing and a plurality of recording heads for color printing. An image recording apparatus having a recording head in which a large number of recording elements are arranged in a line is
Known from the past. In such an image recording device,
One or more recording heads are mounted on the carriage. The carriage can reciprocally drive (scan) the recording head. The reciprocating direction of the recording head is the main scanning axis. The recording head ejects ink onto the recording medium in accordance with the scanning along the main scanning axis.
By this ejection, an image formed by ink dots along the main scanning axis is recorded (formed) on the recording medium.
To be done.

The recording medium has a direction (sub-scanning axis) orthogonal to the drive direction (main-scanning axis) of the recording head.
Then, it is conveyed intermittently. By this conveyance, the recording head and the recording medium move relatively. The image recording along the main scanning axis is performed while the recording medium is stopped. Then, when the recording of the image along the main scanning axis is completed, the recording medium is conveyed by a predetermined amount in the sub scanning direction and stops. By repeating the conveyance and the recording, the image recording apparatus records, that is, prints an image on the entire recording medium. Further, the image recording apparatus performs printing by various printing methods. This printing method includes, for example, one-pass unidirectional printing. In this one-pass one-way printing, the recording head is driven only in one of the forward path and the backward path, and this one driving is performed once. During this driving, the recording head forms an image along the main scanning axis. When the image is formed, the recording medium is conveyed to form the next image.

It should be noted that the mounting angle of one recording head or each of a plurality of recording heads with respect to the carriage must be properly adjusted. For example, the print head is attached to the carriage so that the print element array (nozzle array) is arranged along the sub-scanning axis. In this case, the nozzle row extends in the direction along the sub-scanning axis when the attachment angle is properly adjusted.

A case in which the image recording apparatus in which the mounting angle of the recording head is properly adjusted records an image by one-pass one-way printing will be described below with reference to FIG. FIG. 35 is a schematic diagram showing two ink dot rows printed so that the image recording apparatus is arranged along the sub-scanning direction at a position along an arbitrary main scanning axis.

Since this image recording apparatus performs recording by one-pass unidirectional printing, it records two ink dot rows by scanning twice. In the following description, the first scan is the first scan, and the subsequent scans are the second scans. Note that the arrow md shown in FIG. 35 indicates the drive direction of the recording head, and the arrow td indicates the conveyance direction of the recording medium. The image recording apparatus uses the first scan to print the ink dot row 1
Record 010. Subsequently, the image recording apparatus conveys the recording medium by the nozzle row length dn which is the length of the nozzle row. After this conveyance, the image recording apparatus records the ink dot row 1020 in the second scan. Since the mounting angle of the recording head is adjusted, the ink dot row 1010 and the ink dot row 102 are
0 and 0 are arranged linearly along the sub-scanning direction. That is, the ink dot row to be printed is printed so as to substantially coincide with the arrangement direction of the nozzle row.

In the image recording apparatus described above, when the mounting angle is not properly adjusted, the recording head 1030 is, for example, as shown in FIG.
It is inclined at an inclination angle θ _ha with respect to the sub-scanning axis. In this specification, the inclination of the recording head with respect to a predetermined mounting angle is referred to as “angle deviation”. Therefore, the recording head 1030 has an angle deviation of the inclination angle θ _{ha with} respect to a predetermined mounting angle. Therefore, the nozzle row 1040 also tilts with respect to the sub-scanning axis.

In this state, when the image recording apparatus records an image in the same manner as described above, as shown in FIG. 37, the ink dot row 1010 and the ink dot row 102
0 is inclined and printed at an inclination angle substantially similar to the inclination angle θ _ha of the nozzle row 1040. In addition, in FIG. 37, the ink dot row 1020 has a dot row length that is a length along its own longitudinal axis. The dot row length is substantially the same as the nozzle row length dn.

When the ink dot row is inclined as described above, the ink dot 1011 at the upper end and the ink dot 101 at the lower end of the ink dot row 1010 in FIG.
The position 2 is displaced from the position along the main scanning axis. Like the ink dots 1012, the ink dots at the lower end of the ink dot row 1020 are displaced along the main scanning axis. Therefore, the ink dots 1011 and the ink dots 1022 are separated from each other along the main scanning axis. That is, when the recording head 1030 has an angular deviation, the ink dot row 1010 and the ink dot row 1020 are not linearly aligned in the sub-scanning direction. As described above, the recording head having the angular deviation cannot print a straight line along the sub-scanning axis. Further, in the recording head having the angular deviation, unevenness occurs when colors are overlapped in color printing. Such an angle deviation causes deterioration of image quality of a recorded image.

Therefore, it is necessary to properly adjust the mounting angle of the recording head to the carriage. Conventionally, the adjustment of the angle deviation is performed as follows, for example.

In order to adjust the angle deviation, first, the angle deviation of the recording head is obtained. The inclination angle of the nozzle row and the ink dot row is the inclination angle θ _{ha of the} recording head.
Is substantially the same as. Therefore, the tilt angle θ _ha of the nozzle row 1040 is obtained by finding the tilt angle θ _da of the ink dot row. For example, when it is intended that the print head be mounted so that the nozzle row is along the sub-scanning axis, the inclination angle θ _da of the ink dot row is calculated by the following equation (10) according to the dot row length and the distance th. ) Is required. In the following equation (10), since the dot row length dn is the same as the nozzle row length dn, it is replaced with the nozzle row length. The distance th is the distance between a straight line tb passing through the ink dots at one end of the ink dot row and along the sub-scanning axis, and the ink dot at the other end. Further, the relationship among the inclination angle θ _da , the nozzle row length dn, and the distance th is shown in FIG. 38.

Θ _da = arcsin (th / dn) (10) When the tilt angle θ _da is calculated in this way, the nozzle row length dn is known in advance because it is the total length of the nozzle row. The distance th is measured from the recorded ink dot row. In order to measure this distance th, first, in FIG.
Two ink dot rows 1010 and 1020 similar to that of No. 7 are recorded as a test pattern. Then, the recorded ink dot rows 1010 and 1020 are read by the CCD mounted on the image recording apparatus, and the barycentric position of each ink dot is obtained from the read image of each ink dot row 1010 and 1020. A straight line corresponding to each ink dot row 1010, 1020 is obtained based on the obtained barycentric position of each ink dot. Then, the straight line distance d1 which is the distance between these straight lines is measured.

As a result, the distance between the ink dot 1011 and the ink dot 1022 is obtained. Ink dots 10
22 is substantially the same in position as the ink dot 1012, which is the ink dot at one end of the ink dot row 1010, along the main scanning axis. Also, in general, the distance between straight lines d
1 is very small with respect to the dot row length dn. For this reason, the ink dots 1022 form the ink dot row 1010.
Ink dot 101 that is the ink dot at the other end of the
It can be said that it is positioned so as to be substantially orthogonal to the sub-scanning direction with respect to 1.

From these, the distance d1 between straight lines can be regarded substantially as the distance th. Therefore, the recording head 1030 uses the distance d1 between straight lines and the ink dot row 101.
The nozzle row length dn, which is the dot row length of 0, and the above equation (1
0) is used to determine the tilt angle θ _ha that is substantially the same as the tilt angle θhd.

The angle of the recording head 1030 is adjusted based on the inclination angle θ _ha .

[0016]

As described above, the distance th
The test pattern is recorded when determining Since this test pattern is composed of dot rows, when reading the test pattern, dirt or dust in the vicinity of the dot row is mistakenly recognized as a dot, or conversely, it is formed because the nozzle ejection is weak. Small dots may be recognized as dust. In addition, image loss may occur due to nozzle omissions, landing position shifts, and the like. Due to these causes, a straight line corresponding to the recorded dot row may not be obtained accurately, and as a result, the inclination angle θ _ha may not be obtained accurately.

Further, in order to properly recognize each dot, it is necessary to increase the reading resolution, and it takes a lot of time to read the test pattern. In addition, since the barycentric position of each dot is obtained, the calculation process also requires a lot of time. Further, in order to improve the accuracy of the calculated straight line interval, it is necessary to increase the number of samples (dot row), which increases the reading time and the calculation processing time.

The present invention has been made in consideration of such an actual situation, and its main purpose is to cause stains and dust on the test pattern and defects such as nozzle missing and landing position shift. Another object of the present invention is to provide an image recording apparatus capable of accurately calculating the amount of angular deviation of recording heads based on the mutual relationship.

A further object of the present invention is to provide an image recording apparatus capable of calculating the angular displacement of the recording head in a short time.

Another object of the present invention is to accurately determine the amount of angular deviation of the recording heads based on the mutual relationship even if stains or dust on the test pattern or defects such as nozzle omissions and landing position deviations occur. It is to provide a method of detecting an angle deviation of an image that can be calculated as follows.

A further object of the present invention is to provide a method for detecting the positional deviation of an image, which can calculate the angular deviation of the recording head in a short time.

[0022]

In order to solve the above problems, the image recording apparatus of the present invention has the following configuration.

An image recording apparatus according to one aspect of the present invention includes recording means for recording a pair of test patterns on a recording medium, reading means for reading a pair of test patterns recorded by the recording means, and And a calculating unit that calculates the relative recording position shift amount of the pair of test patterns based on the density data of the pair of test patterns read by the reading unit. The calculating means calculates a relative recording position deviation amount of the pair of test patterns based on a mutual correlation of the density data of the pair of test patterns, and an angular deviation amount of the recording head based on the recording position deviation amount. To calculate.

Further, the calculating means calculates the cross-correlation function between the density data of the pair of test patterns, and the relative recording position deviation amount of the pair of test patterns from the position having the maximum value of the cross-correlation function. Is calculated, and the angular deviation amount of the recording head is calculated based on the relative recording position deviation amount.

The calculating means sequentially calculates the integrated value of the density data based on the correlation between the density data of the pair of test patterns while relatively changing the positions of the density data of the pair of test patterns. The calculation means calculates a relative recording position deviation amount of the pair of test patterns from the position where the integrated value reaches a peak, and the recording head and the recording medium are calculated based on the relative recording position deviation amount. Calculate the relative angular offset.

Further, the calculating means calculates the skew feeding amount of the sheet conveyance which occurs at the time of recording the test pattern, and calculates the angular deviation of the recording head in consideration of the skew feeding amount of the sheet transport.

The angular displacement of the recording head according to one aspect of the present invention is read by a recording step of recording a pair of test patterns on a recording medium and a reading step of reading a pair of test patterns recorded on the recording medium. Based on the mutual correlation between the image data of a pair of test patterns,
The method includes a calculation step of calculating a relative recording position deviation amount of the pair of test patterns, and a step of calculating an angular deviation of the recording head from the relative recording position deviation amount.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, an image recording apparatus will be described with reference to FIG. As shown in FIG. 1, the image recording apparatus 100 includes a carriage 110 and a paper holding mechanism 140 that are opposed to each other with a space therebetween. A sheet 192 that is a recording medium is passed between the carriage 110 and the sheet holding mechanism 140. Paper 192
Is a conveyance roller pair including a conveyance roller 152 and a nip roller 154, a paper discharge roller 162 and a nip roller 164.
It is sandwiched by a pair of paper discharge rollers composed of and is conveyed from the top to the bottom of the drawing by these roller pairs.

The sheet holding mechanism 140 has a platen 142 having a large number of holes, and a fan 148 for pulling the internal space (platen chamber) 144 of the sheet holding mechanism 140 to a negative pressure. The sheet 192 is attracted to the platen 142 by the negative pressure generated by the fan 148 while being conveyed.

The carriage 110 includes a recording unit 120, which is a recording unit for recording an image on the paper 192, and the paper 1.
A CCD unit 130, which is a reading unit for reading an image recorded in 92, is provided. The carriage 110 is supported by a pair of guides 112 so as to be movable along a main scanning axis orthogonal to the paper surface.

The image recording apparatus 100 further has a carriage controller 170 for controlling the carriage 110. The carriage control unit 170 controls the carriage driving mechanism 172, which is a scanning unit for moving the carriage 110 along the main scanning axis, and the recording unit so that a test image including a pair of test patterns is recorded on the sheet 192. Based on the mutual correlation between the recording control unit 174, which is a control unit, and the density data of the pair of test patterns, the relative recording position displacement amount of the pair of test patterns is calculated, and the recording is performed based on the recording position displacement amount. It has an angle deviation calculation unit 176 which is a calculation means for calculating the angle deviation amount of the head.

The carriage driving mechanism 172 can move the carriage 110 along the main scanning axis. While the carriage 110 is moved along the main scanning axis, the recording unit 12
0 indicates a test image including a pair of test patterns on paper 1
Record at 92.

The pair of test patterns may be composed of a pair of test patterns or a plurality of pairs of test patterns. That is, each of the pair of test patterns may be composed of a single test pattern or a plurality of test patterns.

The recording unit 120 has one recording head in an image recording apparatus for monochrome printing, and has a plurality of recording heads in an image recording apparatus for color printing. For example, in an inkjet printer that handles six colors of black, cyan, magenta, light cyan, light magenta, and yellow, the recording unit 120 includes six recording heads for each color. The number of recording heads included in the recording unit 120 is arbitrarily determined according to the image quality required for the image recording apparatus.

One recording head included in the recording unit 120 is shown in FIG. As shown in FIG. 2, the recording head 122 is composed of a single unit 210 having a large number of recording elements (inkjet nozzles) arranged in a row at a constant pitch along the sub-scanning axis. In other words, the recording head 122 is composed of a single unit 210 having one nozzle row 212.

In the image recording apparatus using the recording head 122 as described above, normally, ink dots are formed in the area traversed by the nozzle row 212 of the recording head 122 by the movement of the carriage 110 along the main scanning axis.

For example, in order to print one straight line extending along the sub-scanning axis, ink is ejected from all ink jet nozzles at predetermined positions in the forward path to form ink dots, and the paper 192 is ink-printed. It moves along the sub-scanning axis by a distance corresponding to half the dot pitch, and ink is formed by ejecting ink from all inkjet nozzles at the same position in the main scanning direction as the ink dots formed in the forward path on the return path. . As a result, a large number of rows of ink dots, that is, straight lines, are printed without gaps along the sub-scanning axis.

One or a plurality of such recording heads 1
In the image recording apparatus provided with 22, the recording head 122 or each of the plurality of recording heads 122 needs to have the recording head angle adjusted appropriately. For this reason,
One of the pair of test patterns is printed in the first scan,
The other of the pair of test patterns is printed by the second scan.

Next, an angle deviation detecting method for adjusting the angle of the recording head will be described. Below, one black recording head will be described as a representative. In the following description, the black recording head has 496 inkjet nozzles, and the inkjet nozzle is 360d.
It is assumed that the nozzles are arranged at a nozzle pitch of pi. In addition, in the present embodiment, the nozzle row 212 is arranged along the sub-scanning axis. Therefore, in this angular displacement detection method, the angular displacement of the recording head with respect to the sub-scanning axis is detected. Note that the angular deviation detection can detect an angular deviation with respect to an arbitrary axis other than the angular deviation with respect to the sub-scanning axis.

In the angle deviation detecting method, a test image is recorded, a test pattern is read, and an angle deviation amount is calculated.

Recording (Printing) of Test Image The test image includes, for example, as shown in FIG. 3, a pair of test patterns 312 and 314 and a black pattern 316 for adjusting a black level which will be described later. Recording of the test pattern is performed by one-pass unidirectional printing. In FIG. 3, the carriage driving direction md and the sheet conveying direction td are shown, and the driving direction md and the sheet conveying direction td are orthogonal to each other. The driving direction md
Is along the main scanning axis, and the paper transport direction td is along the sub scanning axis.

Recording of the above test pattern is schematically shown in FIG. In printing this test pattern, as shown in FIG. 4, the print head 802 (1
st) in the driving direction md (right side in the figure), the black pattern 316 is recorded using the lower half of the nozzle row, and the test pattern 31 is printed using the upper half of the nozzle row.
Record 2. The total length of the nozzle row in the longitudinal direction is the nozzle row length dn.

After recording the black pattern 316 and the test pattern 312, the paper is conveyed by a distance dn / 2 corresponding to half the nozzle row length dn. After this conveyance, in the second scan, the print head 802 (2nd) prints the test pattern 314 using the lower half of the nozzle row.

The test patterns 312 and 314 are both composed of a single test pattern. The preferable pair of test patterns 312 and 314 have a high correlation. Therefore, the test pattern is composed of the same pattern element, for example, a rectangular pattern element having a width of 5 dots. The test patterns 312 and 314 are recorded with a shift of, for example, 64 dots along the main scanning axis so as not to overlap each other. The shift amount of the test pattern is not limited to 64 dots, and is arbitrarily set according to the width of the test pattern to be printed and the like.

The test patterns 312 and 314 are
Actually, due to the inclination of the recording head, as shown in FIG.
It does not extend along the sub-scanning axis, but tilts as shown in FIG.

Reading of Test Pattern In the following explanation, the CCD unit 130 is 1440 dpi.
It has the reading resolution of.

As shown in FIG. 6, the sheet 192 is conveyed upstream in the sheet conveying direction. By this conveyance, the test image including the test patterns 312 and 314 and the black pattern 316 is arranged above the CCD unit 130 in the carriage 110. Then, the carriage 110 is moved to arrange the CCD unit 130 below the black pattern 316.

At this position (the position shown in FIG. 6), the focus of the CCD unit 130 is adjusted. After the focus adjustment is completed, the white level of the CCD unit 130 is adjusted at that position using the white background portion of the paper. This brightness adjustment is performed by a known method.

After the white level adjustment, the CCD unit 1
While the position of 30 is fixed, the paper 192 is transported to the downstream side in the paper transport direction until the CCD unit 130 detects the black pattern 316. As the sheet 192 is conveyed, the image pickup area of the CCD unit 130 is
The white background of 92 changes to the black background of the black pattern 316, and the output signal of the CCD unit 130 changes accordingly. The printer control unit (not shown) recognizes that the CCD unit 130 faces the black pattern 316 as shown in FIG. 7 based on the output signal of the CCD unit 130, and the paper sheet is detected according to the recognition. The conveyance of 192 is stopped.

The black level of the CCD unit 130 is adjusted at the position where the CCD unit 130 faces the black pattern 316. This brightness adjustment is performed by a known method.

After the black level adjustment is completed, in order to read the test pattern, the paper 192 is further conveyed to the upstream side in the paper conveyance direction, and the CCD unit 130 is moved to the test pattern 3
It is arranged immediately before the lower ends of the 12, 314.

After that, the paper 192 is conveyed by a minute amount, for example, by an amount (ideally, a distance corresponding to one dot line) when the drive pulse of the conveying motor is set to 20 pulses. CCD unit 1 for every minute conveyance
30 reads the test patterns 312 and 314 (correctly, the brightness of the optical image). The data read by the CCD unit 130 is stored in the memory for each minute conveyance. Until the CCD unit 130 finishes reading the test pattern, these series of operations such as sheet conveyance, image reading, and data storage are continued.

Calculation of Angle Shift Amount Here, the principle of calculating the angle shift amount θ _ha of the recording head 122 of the present embodiment will be described. As described above with reference to FIG. 4, the test pattern 312 is printed using the lower half of the nozzle row in the first scan. After the paper has been transported a distance corresponding to half the nozzle row length dn, the test pattern 314 is printed using the upper half of the nozzle row in the second scan.

When the recording head 122 has no angular deviation,
As shown in FIG. 3, the test patterns 312, 31
4 is parallel to the sub-scanning axis. The test patterns 312 and 314 are separated from each other by 64 dots along the main scanning axis so as not to overlap each other. However, if the recording head 122 has an angle deviation, the test pattern 3
12, 314 are inclined with respect to the sub-scanning axis, as shown in FIG. FIG. 5 shows, as an example, test patterns 312 and 314 recorded by the recording head that is angularly shifted clockwise about the center of gravity of the nozzle row. In order to compare the test patterns 312 and 314 with and without the angular deviation, FIG.
FIG. 6 is a diagram showing test patterns 312 and 314 in FIG. 5 together with areas recorded when there is no angular deviation. In FIG. 8, a solid line 822 indicates a recording area in the case where an image is also recorded in the lower half nozzle row together with the test pattern 312 in the case where there is the angular deviation. A test pattern 312 is included in this recording area.
A solid line 824 indicates a recording area in the case where an image is also recorded in the upper half nozzle row together with the test pattern 314 in the case where there is the angular deviation. A test pattern 314 is included in this recording area. Broken line 832
Shows a recording area in the case where an image is also recorded in the lower half nozzle row together with the test pattern 312 when there is no angle deviation. A broken line 834 indicates a recording area when an image is recorded in the upper half nozzle row together with the test pattern 314 when there is no angle deviation. Therefore, these recording areas have a nozzle row length d.
It has the same longitudinal dimension as n.

As shown in FIG. 8, when there is no angular deviation, the recording area indicated by broken lines 832 and 834 has the central portion and the end portion along the longitudinal direction at the same position along the main scanning axis. positioned. From this, it is understood that the lower end of the test pattern 312 and the lower end of the test pattern 314 shown in FIG. 3 can keep 64 dots, which is a predetermined separation distance.

However, if there is an angle deviation, the solid line 82
In the recording areas denoted by reference numeral 2,824, the central portion and the end portions along the longitudinal direction are located at different positions along the main scanning axis. This angular deviation occurs because the recording head rotates clockwise around the position of the center of gravity of the nozzle row as the center of rotation. Therefore, in the central portion of the recording area indicated by the solid lines 822 and 824, the position of the central portion of the storage area when there is no angular displacement is substantially the same as the position along the main scanning axis. However, the ends of the recording area indicated by the solid lines 822 and 824 are displaced from each other in position along the main scanning axis with respect to the positions of the ends of the storage area when there is no angular deviation. That is, the recording position deviation amount γ _tm of the end portion of the recording area indicated by the solid lines 822 and 824 with respect to the end portion of the storage area when there is no angular deviation is obtained by increasing or decreasing the 64 dots which is the predetermined separation distance. To be
Specifically, the recording position deviation amount γ _tm is the distance between the central portion of the recording area indicated by the solid line 822 and the end portion of the recording area indicated by the solid line 824, with respect to 64 dots which is the predetermined separation distance. It is calculated by increasing or decreasing.

When the angle deviation is counterclockwise,
The central portion of the recording area indicated by the solid line 822 and the solid line 824
The distance from the lower end of the recording area indicated by is wide. On the contrary, when the angular deviation is clockwise, the solid line 822
The interval between the central portion of the recording area indicated by and the lower end portion of the recording area indicated by the solid line 824 is narrow.

In this embodiment, the solid line 812
The central portion of the recording area indicated by is the test pattern 312.
Is the lower end of. And the recording area shown by the solid line 814
The lower end of the area is the lower end of the test pattern 314.
Therefore, the test pattern 312 and the test pattern 31
4, the above-mentioned predetermined separation from the separation distance along the main scanning axis
The value obtained by subtracting 64 dots, which is the distance, is the recording position deviation amount γ
_tmBecomes That is, along the main scanning axis of the pair of test patterns.
The relative positional deviation amount is the recording positional deviation amount γ _tmAnd
It The test pattern 312 and the test pattern 31
How to calculate the separation distance along the main scanning axis from 4 will be described later.
explain in detail.

The recording position shift amount γ _tm is the distance along the main scanning axis from the center to the end of the recording area, as described above. Further, since the distance from the center to the end of the recording area is half the nozzle row length dn, dn /
It is 2. The inclination angle of the recording area is substantially the same as the inclination angle (angle deviation amount θ _ha ) due to the angle deviation of the recording head. Therefore, the angle shift amount _ha can be expressed by the following equation (9).

Θ _ha = arcsin (γ _tm / (dn / 2)) (9) Calculation of the recording position deviation amount of the pair of test patterns Next, along the main scanning axis of the pair of test patterns 312 and 314. The calculation of the relative recording position shift amount will be described. In the present embodiment, the amount of deviation is calculated using the cross-correlation function.

The cross-correlation function Φ12 (τ) of two signals r ₁ (x) and r ₂ (x) is expressed by the following equation (1).

Φ12 (τ) = ∫r ₁ (x) r ₂ (x−τ) dx (1) Here, τ represents the distance between two signals. Φ12
(Τ) has a maximum value when the signal r ₁ (x) and the signal r ₂ (x) match.

In the actual processing, as shown in FIG.
Test pattern 3 read by CCD unit 130
Optical images 312i and 314i of the test pattern 312 recorded in the first scan
And an optical image 314i of the test pattern 314 recorded in the second scan. Recording resolution is 360 dpi
On the other hand, since the CCD resolution is 1440 dpi, the optical image division width is as shown in the following expression (2) when the shift amount between the test pattern 312 and the test pattern 314 at the time of recording the test pattern is 64 dots. Become.

Optical image division width = 64 dots × (1440 dpi ÷ 360 dpi) (2) Next, the data of the optical images 312i and 314i are summed in the sub-scanning direction (the reading direction of the CCD unit 130). , The added density data of the optical image 312i (FIG. 10) and the added density data of the optical image 314i (FIG. 11)
Ask for.

Subsequently, a cross-correlation function is obtained with the added density data of the optical image 312i in the sub-scanning direction as r ₁ (x) and the added data of the optical image 314i in the sub-scanning direction as r ₂ (x). The position where the cross-correlation function shows the maximum value is calculated.

Specifically, the cross-correlation of the test pattern is examined by the cross-correlation function as follows. Figure 1
2 is the added density data 7 of each of the pair of optical images 312i and 314i that is the target of the recording position shift amount to be obtained.
12, 714 and the relative positional relationship between them are shown. Then, FIG. 13 shows a cross-correlation function Φ ₁₂ (τ) between the two added density data 712 and the added density data 714, which is shown.

In FIG. 13, d1 that gives the maximum value of the cross-correlation function indicates the distance between the optical images 312i and 314i. That is, the position value calculated in this way is
Optical image 312 of the pair of test patterns 312 and 314
The recording position deviation amount γ _tp1440 of i and 314i is shown.

The recording position shift amount γ calculated in this way
_tp1440 is for optical images 312i, 314i read at a resolution of 1440 dpi, thus 3
The recording position shift amount γ _tp360 of the actual test patterns 312 and 314 recorded at the resolution of 60 dpi is expressed by the following equation (3).

Γ _tp360 = γ _tp1440 ÷ (1440 dpi ÷ 360 dpi) (3) The recording position deviation amount γ _tp360 is the test patterns 312, 3
The amount of shift given in order to avoid mutual overlap when recording 14 is included. Therefore, the recording position shift amount γ _tm to be obtained is a value obtained by subtracting the recording shift amount γ _tp360 previously obtained from the recording shift amount 64 dots. That is, the recording position shift amount γ _{tm to be obtained} is expressed by the following equation (4).

Γ _tm = γ _tp360 −64 (4) In the present embodiment, the relative recording position deviation amount of the pair of test patterns recorded for adjusting the ink ejection timing is _calculated as the pair of test patterns. Since it is obtained by using the cross-correlation function of the density data, the recording position deviation amount can be calculated in a short time and with high accuracy.

(Second Embodiment) The image recording apparatus of the second embodiment will be described below. This embodiment is different from the first embodiment only in the shape and number of test patterns, and the device configuration and the like are the same as in the first embodiment.

As described above, the pair of test patterns are
It is not limited to the one composed of a pair of test patterns. The pair of test patterns may be composed of a plurality of pairs of test patterns.

Specifically, in the present embodiment, (1)
A test pattern using any one of the methods of increasing the number of test patterns, (2) using a plurality of test patterns having different widths, and (3) adding a test pattern in the sub-scanning direction is used.

(1) Increasing the number of test patterns The test pattern of the method (1) is, as shown in FIG. 15, a pair of test patterns 332 and 334 and another pair of test patterns 336 and 338. It further includes another pair of test patterns 340 and 342. Test pattern 33 included in one of the pair of test patterns
2, 336, and 340 are printed by the first scan, for example, and the test pattern 3 included in the other of the pair of test patterns.
34, 338 and 342 are recorded in the second scan.

Test patterns 332, 334, 336,
338, 340, and 342 are recorded with a shift of, for example, 64 dots along the main scanning axis so as not to overlap each other. In other words, the test patterns 332, 334, 336,
The 338, 340, and 342 are arranged at a pitch of 64 dots along the main scanning axis.

Test patterns 332, 334, 336,
338, 340, and 342 are all the same pattern element,
For example, it is composed of a rectangular pattern element having a width of 5 dots. Test patterns 332, 334, 336, 33
8, 340, 342 are all CCD units 130
It is recommended that the data be recorded to fit within the reading width of.

The width of the rectangular pattern element of the test pattern is not limited to 5 dots. Also, the number of test patterns is not limited to six. Further, the shift amount of the test pattern is not limited to 64 dots. The width of the rectangular pattern element, the number of test patterns 6, and the shift amount of the test pattern are
Under the condition that the test patterns do not overlap each other, preferably all of the test patterns are in the CCD unit 130.
It may be arbitrarily changed under the condition that the reading width is within.

As shown in FIG. 16, the data read by the CCD unit 130 is the optical images 332i, 336i of the test patterns 332, 336, 340 recorded on the outward path which constitute one of the pair of test patterns. ,
340i and the test patterns 334, 338, and 34 recorded on the return path, which constitute the other of the pair of test patterns.
2 optical images 334i, 338i, 342i.

The recording position deviation amount of the pair of test patterns is, for example,
By the above-mentioned method, the recording position deviation amount between the pair of test patterns is calculated by using the cross-correlation function, the calculated plural recording position deviation amounts are averaged, and the angular deviation amount is calculated based on the average value. Is required.

Alternatively, the recording position deviation amount of the pair of test patterns is calculated by comparing the test pattern group printed by the first scan and the test pattern group printed by the second scan with each other.
It may be obtained using the cross-correlation function by the method described above.

According to the present modified embodiment, since the number of samples is large, it is effective in improving the accuracy of the required recording position shift amount.

(2) It is not necessary that the plurality of test patterns using the plurality of test patterns having different widths are composed of the same pattern element. Multiple test patterns are
Each pair of test patterns may be composed of different pattern elements.

In the method of (2), as shown in FIG. 19, the pair of test patterns is a pair of test patterns 36 composed of rectangular pattern elements having a width of 5 dots.
2, 364 and another pair of test patterns 366, 368 composed of rectangular pattern elements having a width of 10 dots
And a further pair of test patterns 370 and 372 each composed of a rectangular pattern element having a width of 4 dots. These six test patterns 362, 364,
366, 368, 370 and 372 are 6 along the main scanning axis.
They are arranged at a pitch of 4 dots.

This method has the following advantages over the test pattern of the method (1).

In the test pattern of the method (1),
For example, as shown in FIG. 17, consider a case where one of the six test patterns 332, 334, 336, 338, 340, 342 is missing. In this case, as shown in FIG. 18, test patterns 332, 334, 336, 338, 340.
Added density data 332n, 334n, 336n, 33
8n and 340n are obtained, but the added density data 342n (indicated by a broken line) of the missing test pattern 342 is not obtained. In FIG. 18, the added density data 332n, 336n, and 340n corresponding to the test patterns 332, 336, and 340 printed in the first scan correspond to the upper side, and the test patterns 334 and 338 recorded in the second scan correspond. The addition density data 334n and 338n to be performed are shown on the lower side.

The cross-correlation function obtained for the added density data shown in FIG. 18 is shown in FIG. This cross-correlation function has a pair of peaks 352 and 354 showing the same maximum value, as shown in FIG. This is because the added density data 332n, 336 on the upper side in FIG.
n, 340n, the lower added density data 334
n and 338n are shifted 64 dots to the left along the main scanning axis, the correlation between the added density data 332n and 336n and the added density data 334n and 338n, and the added density data 334n and 338n are moved to the right along the main scanning axis. 25
6 dots (64 as the resolution when recording the test pattern
Dot (see FIG. 18)) Addition density data 336n, 340n and addition density data 334n, 33
This is because the correlation with 8n is the same.

As described above, in the test pattern of the method (1) shown in FIG. 15, when some of a plurality of the same test patterns are missing, a pair of peaks whose cross correlation functions show the same maximum value. Since it has 352 and 354, it is difficult to distinguish the peak representing the original recording position shift amount.

On the other hand, in the test pattern using this method, as shown in FIG. 20, a pair of test patterns 362 and 364 are both composed of rectangular pattern elements having a width of 5 dots, and another pair of test patterns Test patterns 366, 3
68 consists of rectangular pattern elements each having a width of 10 dots, and a pair of further test patterns 370 and 372.
Are both formed by a rectangular pattern having a width of 4 dots.

Since the width of the pattern element is different for each pair of test patterns in this way, the correlation between the two test patterns included in the different pair of test patterns is such that the two test patterns forming the same pair of test patterns are correlated. It is lower than the correlation of. Therefore, the obtained cross-correlation function has only one peak showing the maximum value, and the calculation of the recording position deviation amount can be stably and easily performed.

The number of test patterns and the width of the rectangular pattern are not limited to the above values, and may be changed arbitrarily.

(3) Adding a test pattern in the sub-scanning direction The test pattern using this method is the test pattern 412 recorded in the lower half of the nozzle row in the first scan, as shown in FIG. Will be recorded. In addition, in the second scan, the test patterns 414, 41
6 is recorded. The test pattern 414 is arranged along the main scanning axis 6 so as not to overlap with the test pattern 412.
It is offset by 4 dots. The test pattern 416 is recorded at the same position as the test pattern 412 along the main scanning axis.

The method (3) has the following advantages as compared with the methods (1) and (2). The test patterns using the methods (1) to (3) are all the first
The sheet is conveyed between the scanning and the second scanning. When skewing occurs in the sheet conveying direction, the skewing causes the test pattern recording position to shift. If the test patterns recorded by the methods (1) and (2) are used for calculating the recording position deviation amount, the deviation of the recording position becomes a measurement error as it is. However, in the method (3), the test patterns 412 and 416 shown in FIG.
It is possible to calculate the amount of positional deviation of the optical images 412n and 416n in the main scanning direction. Therefore, the skew amount of the sheet is obtained by using the equation (9) described in the first embodiment. Therefore, after correcting the skew amount,
The positional shift amount of the test patterns 412 and 414 can be calculated. Therefore, the method (3) can accurately calculate the recording position deviation amount even when the sheet is conveyed in a skewed manner.
Therefore, the test pattern of the method (3) is useful for improving the accuracy of calculation of the amount of angular displacement of the recording head.

(Third Embodiment) The image recording apparatus of the third embodiment will be described below. The present embodiment differs from the first embodiment only in the method of calculating the recording position shift amount, and the device configuration and the like are the same as in the first embodiment. Further, the modified example of the test pattern described in the second embodiment can be applied to this embodiment as it is.

In this embodiment, while the positions of the density data of the pair of test patterns are relatively changed, the integrated value of the density data is sequentially calculated based on the correlation of the density data of each other, and the integrated value becomes a peak. From this position, the relative recording position shift amount of the pair of test patterns is calculated.

Specifically, (1) the integrated value of the logical product of the binarized density data, (2) the integrated value of the logical sum of the binarized density data, and (3) the multivalued One of the integrated value of the comparison minimum value group of the density data, (4) the integrated value of the difference between the multivalued density data, and (5) the integrated value of the product of the multivalued density data, was obtained. The recording position shift amount is calculated from the peak value.

(1) Calculation Based on the Integral Value of the Logical Product of Binarized Density Data First, the added density data of a pair of test patterns, which is the target of the recording position deviation amount to be calculated, is calculated and binarized. 23, a pair of binarized density data 612 and 614 are obtained as shown in FIG. Binarization refers to comparing density data with a predetermined threshold value, and density data above the threshold value is 1
In addition, the density data below the threshold value is converted into 0.

A pair of binarized density data 612, 6
24, the logical product (AND) of arbitrary x values is taken, and the logical product 622 of the binarized density data is obtained as shown in FIG. 24. The area of 622 is calculated (that is, the integrated value is calculated). This operation is performed for any d1. That is,
In FIG. 23, the binarized density data 612 is + x
The series of calculations described above are performed while shifting in the direction. As a result, as shown in FIG. 25, a graph showing the relationship between the shift between the pair of binarized density data 612 and 614 and the integrated value of their logical product 622 is obtained.

The integrated value of the logical product of the binarized density data is a pair of binarized density data 612, 6 while shifting the binarized density data 612 in the + x direction.
The value increases as the overlap of 14 increases, and decreases as the overlap decreases. That is, the integrated value of the logical product of the pair of binarized density data has the maximum value when the pair of binarized density data overlap each other most.

In FIG. 25, d1 that gives the maximum area
Is a pair of binarized density data 612, 614.
The recording position deviation amount of the pair of test patterns corresponding to the above is shown. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.

(2) Calculation based on the integrated value of the logical sum of the binarized density data First, as in the calculation of the recording position deviation amount based on the logical product described above, the added density data of a pair of test patterns is calculated. Seeking,
This is binarized to obtain a pair of binarized density data 612 and 614 as shown in FIG.

A pair of binarized density data 612, 6
26, the logical sum (OR) of any value of x is taken, and the logical sum 632 of the binarized density data is obtained as shown in FIG. The area of 632 is calculated (that is, the integrated value is calculated). This operation is performed for any d1. That is,
In FIG. 23, the binarized density data 612 is + x
The series of calculations described above are performed while shifting in the direction. As a result, as shown in FIG. 27, a graph showing the relationship between the shift between the pair of binarized density data 612 and 614 and the integrated value of their logical sum 632 is obtained.

The integrated value of the logical sum of the binarized density data is a pair of binarized density data 612, 6 while shifting the binarized density data 612 in the + x direction.
It becomes smaller as the overlap of 14 increases, and becomes larger as the overlap decreases. That is, the integrated value of the logical sum of the pair of binarized density data has the minimum value when the pair of binarized density data overlap each other most.

In FIG. 27, d1 giving the minimum area
Is a pair of binarized density data 612, 614.
The recording position deviation amount of the pair of test patterns corresponding to the above is shown. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.

(3) Calculation Based on Integral Value of Comparison Minimum Value Group of Multi-Valued Density Data First, as shown in FIG. 28, the added density of a pair of test patterns which is the target of the recording position deviation amount to be obtained. Data 712 and 714 are obtained. Added density data 712, 7
Reference numeral 14 is multivalued density data.

Next, as shown in FIG. 29, a comparison minimum value group 72 of a pair of multivalued addition density data 712, 714.
Take 2. Here, the comparison minimum value means that the density data at an arbitrary x of the pair of multivalued addition density data 712 and 714 is compared to obtain the smaller density data value (minimum value). Then, this comparison minimum value is acquired in the x direction, and the integrated value of the minimum value group 722 is taken. Therefore, a pair of multivalued addition density data 712,
To take the integrated value of the comparison minimum value group 722 of 714 means to superimpose a pair of multivalued addition density data 712 and 714,
This is equivalent to obtaining the area of the overlapping portion.

This operation is performed for any d2. That is, in FIG. 28, the series of calculations described above are performed while shifting the multivalued addition density data 712 in the + x direction. Thereby, as shown in FIG. 30, a graph showing the relationship between the shift amount of the pair of added density data 712 and 714 and the integral value of the comparative minimum value group 722 is obtained.

The integrated value of the minimum group of comparisons between density data is obtained while shifting the added density data 712 in the + x direction,
It increases as the overlap of the pair of added density data 712 and 714 increases, and decreases as the overlap decreases. That is, the integrated value of the comparison minimum value group of the pair of density data takes the maximum value when the density data overlap each other most.

In FIG. 30, d2 that gives the maximum area
The value of indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multivalued addition density data 712 and 714. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.

(4) Calculation Based on Integral Value of Difference between Multi-Valued Density Data First, as in the calculation of the recording position shift amount based on the integrated value of the comparison minimum value group of density data described above, FIG. As shown, the added density data 712 and 714 of the pair of test patterns, which are the targets of the print position shift amount to be obtained, are obtained. The added density data 712 and 714 are multivalued density data.

Next, as shown in FIG. 31, the absolute value 742 of the density difference at an arbitrary x of the pair of multivalued addition density data 712 and 714 is taken. Furthermore, the integrated value of the absolute value 742 of the difference between the pair of multivalued addition density data 712 and 714 is taken.

This operation is performed for any d2. That is, in FIG. 28, the series of calculations described above are performed while shifting the multivalued addition density data 712 in the + x direction. Thus, as shown in FIG. 32, a graph showing the relationship between the shift amount of the pair of added density data 712 and 714 and the integrated value of the absolute value 742 of the difference between them is obtained.

The integrated value of the absolute value 742 of the difference between the density data becomes smaller as the overlapping of the pair of additional density data 712 and 714 increases, and decreases as the overlapping decreases while the added density data 712 is shifted in the + x direction. growing. That is, the integrated value of the absolute value of the difference between the pair of density data has the minimum value when the pair of density data overlap each other most.

In FIG. 32, d2 giving the minimum area
The value of indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multivalued addition density data 712 and 714. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.

(5) Calculation Based on the Integral Value of the Product of Multi-Valued Density Data First, as in the calculation of the recording position shift amount based on the integrated value of the comparison minimum value group of the density data described above, FIG. As shown, the added density data 712 and 714 of the pair of test patterns, which are the targets of the print position shift amount to be obtained, are obtained. The added density data 712 and 714 are multivalued density data.

Next, as shown in FIG. 33, the product 752 of the densities of a pair of multivalued addition density data 712 and 714 at an arbitrary x is taken. Further, the integrated value of the product 752 of the pair of multivalued addition density data 712 and 714 is taken.

This operation is performed for any d2. That is, in FIG. 28, the series of calculations described above are performed while shifting the multivalued addition density data 712 in the + x direction. As a result, as shown in FIG. 34, the shift amount of the pair of added density data 712 and 714 and the product 7 thereof are calculated.
A graph showing the relationship with the integrated value of 52 is obtained.

The integrated value of the product 752 of the density data sets increases as the overlap of the pair of addition density data 712 and 714 increases and decreases as the overlap decreases while the added density data 712 is shifted in the + x direction. That is, the integrated value of the product of the pair of density data takes the maximum value when the pair of density data overlap each other most.

In FIG. 34, d2 giving the maximum area
The value of indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multivalued addition density data 712 and 714. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.

The recording position deviation amount obtained as described above is shown in FIG.
28, which is the shift amount in FIG. 28, and the print position shift amount to be finally obtained is obtained by subtracting the shift amount given at the time of recording the test pattern from the print position shift amount obtained here.

In this embodiment, since the relative recording position deviation amount of the pair of test patterns is obtained by using the mutual correlation of the density data of the pair of test patterns, the recording position deviation amount is short. It can be calculated with high accuracy.

Although some embodiments have been specifically described with reference to the drawings, the present invention is not limited to the above-described embodiments, and is carried out without departing from the scope of the invention. Includes all implementations.

[0123]

According to the present invention, even if dirt or dust on the test pattern or defects such as nozzle missing or landing position deviation occur, the amount of angular deviation of the recording heads can be accurately determined based on the mutual relationship. It is possible to provide an image recording device that can be calculated. Furthermore, the present invention can provide an image recording apparatus capable of calculating the angular deviation of the recording head in a short time.

Further, according to the present invention, even if stains or dust on the test pattern or defects such as nozzle omissions and landing position shifts occur, the angle shift amount of the print heads is accurately calculated based on the mutual relationship. It is possible to provide a method of detecting an angular deviation of an image that can be performed. Furthermore, the present invention can provide a method for detecting the positional deviation of an image, which can calculate the angular deviation of the recording head in a short time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an image recording apparatus according to the present invention.

FIG. 2 is a front view showing one recording head included in the recording section shown in FIG.

FIG. 3 is a diagram showing a test image including a pair of test patterns and a black pattern.

FIG. 4 is a schematic view showing a process of forming the test pattern of FIG.

FIG. 5 is a diagram showing a test pattern having an angular deviation.

FIG. 6 is a diagram illustrating a focus adjustment and a white level adjustment,
It is a figure which shows the positional relationship of the CCD unit with respect to the image shown in FIG.

7 is a diagram showing the positional relationship of the CCD unit with respect to the image shown in FIG. 5 during black level adjustment.

FIG. 8 is a diagram for comparing a test pattern having an angular deviation and a test pattern having no angular deviation.

9 is a diagram showing optical images of a pair of test patterns shown in FIG. 6 read by a CCD unit.

10 is a diagram showing added density data of an optical image of the left test pattern shown in FIG. 6;

11 is a diagram showing added density data of an optical image of the right test pattern shown in FIG. 6;

12 is a diagram showing added density data obtained for the optical image shown in FIG. 9;

FIG. 13 is a graph showing the cross-correlation of the pair of multivalued addition density data shown in FIG. 12 by the cross-correlation function.

FIG. 14 is a diagram showing a test pattern using the method (1).

FIG. 15 is a diagram showing optical images of the six pattern blocks shown in FIG. 14 read by the CCD unit.

FIG. 16 is a diagram showing a state in which one of the six pattern blocks shown in FIG. 14 is missing.

17 is a diagram showing added density data obtained for the pattern block shown in FIG. 16;

FIG. 18 is a diagram showing a cross-correlation function obtained for the added density data shown in FIG. 17;

FIG. 19 is a diagram showing a test pattern using the method (2).

FIG. 20 is a diagram showing a test pattern using the method (3).

21 is a diagram showing added density data of the test pattern of FIG. 21.

FIG. 22 shows binarized density data of a pair of test patterns for which the recording position shift amount is to be obtained.

23 shows a logical product (AND) of the pair of binarized density data shown in FIG.

24 is a graph showing the relationship between the shift amount of the pair of binarized density data shown in FIG. 22 and the integrated value of their logical product.

25 shows a logical sum (OR) of the pair of binarized density data shown in FIG.

FIG. 26 is a graph showing the relationship between the shift amount of the pair of binarized density data shown in FIG. 22 and the integrated value of their logical sums.

FIG. 27 shows added density data of a pair of test patterns for which the recording position shift amount should be obtained.

28 shows a comparison minimum value group of the pair of multivalued density data shown in FIG. 27.

FIG. 29 is a graph showing the relationship between the shift amount of the pair of multivalued density data shown in FIG. 27 and the integral value of the comparison minimum value group thereof.

FIG. 30 is a diagram showing the absolute value of the difference between the pair of multivalued density data shown in FIG. 27.

31 is a graph showing the relationship between the shift amount of the pair of multivalued density data shown in FIG. 27 and the integrated value of the absolute values of their differences.

32 is a diagram showing a product of a pair of multivalued density data shown in FIG. 27;

FIG. 33 is a graph showing the relationship between the shift amount of the pair of multivalued density data shown in FIG. 27 and the integrated value of their products.

FIG. 34 is a schematic diagram showing two ink dot rows printed so that the image recording apparatus is arranged along the sub-scanning direction at a position along an arbitrary main scanning axis.

FIG. 35 is a front view showing a recording head having an angular deviation.

FIG. 36 is a diagram showing an ink dot row recorded by a recording head having an angular deviation.

FIG. 37 is a diagram showing a relationship between an inclination angle and a nozzle row length.

[Explanation of symbols]

100 image recording device 110 carriage 112 Guide 120 recording section 130 CCD unit 140 paper holding mechanism 170 Carriage controller 172 carriage drive mechanism 174 recording control unit 176 calculator 192 sheets

Claims (5)

[Claims] 1. A recording unit for recording a pair of test patterns on a recording medium, a reading unit for reading a pair of test patterns recorded by the recording unit, and a pair of tests read by the reading unit. An image recording apparatus having a calculation means for calculating a relative recording position deviation amount of a pair of test patterns based on pattern density data, wherein the calculation means calculates a correlation between the density data of a pair of test patterns. An image recording apparatus that calculates a relative recording position deviation amount of a pair of test patterns based on the above, and calculates an angular deviation amount of the recording head based on the recording position deviation amount. 2. The calculation means calculates a cross-correlation function between density data of a pair of test patterns, and a relative recording position deviation amount of the pair of test patterns from a position having the maximum value of the cross-correlation function. The image recording apparatus according to claim 1, wherein the image recording apparatus calculates the angle deviation amount of the recording head based on the relative recording position deviation amount. 3. The calculating means successively calculates the integrated value of the density data based on the correlation between the density data of the pair of test patterns while relatively changing the positions of the density data of the pair of test patterns. A relative recording position deviation amount of the pair of test patterns is calculated from the peak position, and a relative angular deviation between the recording head and the recording medium is calculated based on the relative recording position deviation amount. The image recording apparatus according to item 1. 4. The calculation means calculates a skew amount of sheet conveyance that occurs when a test pattern is recorded, and calculates an angular deviation of a recording head in consideration of the skew amount of sheet conveyance.
And the image recording apparatus described in 3. 5. A recording step of recording a pair of test patterns on a recording medium, a reading step of reading a pair of test patterns recorded on the recording medium, and a mutual step between image data of the read pair of test patterns. Angular deviation detection of the recording head, which includes a calculation step of calculating a relative recording position deviation amount of the pair of test patterns based on the correlation, and a step of calculating an angular deviation of the recording head from the relative recording position deviation amount. Method.