JP4270780B2 - Image recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present inventionFor image recording deviceRelated.
[0002]
[Prior art]
2. Description of the Related Art An ink jet type image forming apparatus that forms an image by ejecting ink onto a recording medium is known. An ink jet type image forming apparatus includes, for example, a recording head having a large number of recording elements (ink jet nozzles) arranged in a line. This type of image forming apparatus includes a single recording head for monochrome printing and a plurality of recording heads for color printing. In such an image forming apparatus, one or a plurality of recording heads are reciprocated along the main scanning axis, and ink is ejected from the recording heads onto the recording medium, thereby forming an image, that is, printing. .
[0003]
Each of the recording heads or the plurality of recording heads needs to adjust the ink ejection timing appropriately between the forward path and the backward path. If the ink ejection timing is not properly adjusted, a deviation occurs between the landing position of the ink droplet ejected in the forward path and the landing position of the ink droplet ejected in the backward path. In an image recorded with such a landing position deviation, white stripes are conspicuous in the sub-scanning direction in monochrome, color deviation occurs in color, and image quality is deteriorated.
[0004]
Therefore, it is necessary to properly adjust the ink ejection timing between the forward path and the backward path. Conventionally, adjustment of injection timing is performed as follows, for example.
[0005]
As shown in FIG. 48, a pair of test patterns 912 and 914 composed of dot rows extending along the array of recording elements are recorded at different positions on the paper. One test pattern 912 is recorded on the forward path, for example, and the other test pattern 914 is recorded on the return path. At this time, the sheet is not transported between the recording in the forward path and the return path. That is, the recording head reciprocates to scan the same part of the paper. The recorded dot row is read by a CCD mounted on the image forming apparatus, and the barycentric position of each dot is obtained from the read dot row image. A straight line corresponding to the dot row is obtained based on the obtained barycentric position of each dot. This process is performed on the dot rows recorded in the forward path and the backward path, respectively, the distance between the respective straight lines is measured, and the recording position deviation amount is calculated.
[0006]
[Problems to be solved by the invention]
Since the test pattern is composed of dot rows, when reading the test pattern, small diameters are formed because dirt or dust near the dot rows are mistakenly recognized as dots, or vice versa. May be recognized as garbage. In addition, image loss may occur due to nozzle omission or landing position deviation. For these reasons, the straight line corresponding to the recorded dot row cannot be obtained accurately, and as a result, the straight line interval may not be obtained accurately.
[0007]
Further, in order to recognize each dot satisfactorily, it is necessary to increase the reading resolution, and it takes a lot of time to read the test pattern. In addition, since the center-of-gravity position of each dot is obtained, much time is required for the calculation process. Furthermore, in order to increase the accuracy of the obtained linear interval, it is necessary to increase the number of samples (dot rows), which increases the reading time and the calculation processing time.
[0008]
So far, the adjustment of the ejection timing in the forward path and the backward path has been described for one recording head, but the ejection timing between a plurality of recording heads also needs to be adjusted appropriately. That is, in an image forming apparatus for color printing, the ejection timing between any two recording heads having different colors needs to be adjusted appropriately. The adjustment of the injection timing is performed in the same manner as the adjustment of the injection timing between the forward path and the return path described above.
[0009]
The ink jet type image forming apparatus includes a recording head having a number of ink jet nozzles arranged in two or more rows, in addition to the image forming apparatus having the recording head having one nozzle row as described above. In other words, an image forming apparatus having a recording head having a plurality of nozzle rows is also known. As a recording head having a plurality of nozzle rows, there are, for example, one constituted by one unit having a plurality of nozzle rows and one in which a plurality of units having one nozzle row are combined.
[0010]
In such an image forming apparatus having a recording head having a plurality of nozzle rows, it is necessary to appropriately adjust the ejection timing between the plurality of nozzle rows. The adjustment of the injection timing is performed in the same manner as the adjustment of the injection timing between the forward path and the return path described above. Of course, in an image forming apparatus provided with a plurality of recording heads for color printing, it is necessary to appropriately adjust the ejection timing between any two recording heads having different colors.
[0011]
The present invention has been made in consideration of such actual situations, and its main purpose is to determine the relative recording position shift amount of a pair of test patterns formed for adjusting the ejection timing of ink. An image forming apparatus capable of calculating in a short time is provided.
[0012]
A further object of the present invention is to provide an image forming apparatus capable of accurately calculating the relative recording position shift amount of a pair of test patterns.
[0015]
[Means for Solving the Problems]
  The present invention,On recording mediathe imageRecording means for recording;Scanning means for reciprocating the recording means along the main scanning axis;By the recording meansOn recording mediaReading means for reading a pair of recorded test patterns, and density data of the pair of test patterns read by the reading meansCorrelationAnd calculating means for calculating the relative recording position deviation amount of the pair of test patterns.Directed to image recording device.
  According to one aspect of the present invention, the pair of test patterns is composed of a plurality of pairs of pattern blocks, and the plurality of pairs of pattern blocks are composed of different pattern elements for each pair. A pattern block included in one of the plurality of pairs of pattern blocks is recorded during the forward movement by the scanning unit, and a pattern block included in the other of the plurality of pairs of pattern blocks is recorded during the backward movement..
  According to another aspect of the present invention, the pair of test patterns includes a plurality of pairs of pattern blocks, and at least a part of the plurality of pairs of pattern blocks includes a plurality of pattern elements. The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and records a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. To do.
  According to still another aspect of the present invention, the pair of test patterns includes a plurality of pairs of pattern blocks, and the plurality of pairs of pattern blocks are arranged at different intervals along a main scanning axis, and the recording The means records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and records a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. .
  According to still another aspect of the present invention, the pair of test patterns is composed of a plurality of pairs of pattern blocks, and at least some pairs of pattern elements of the plurality of pairs of pattern blocks are composed of a plurality of portions having different densities. The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and a pattern included in the other of the plurality of pairs of pattern blocks during the backward movement. Record the block.
  According to still another aspect of the present invention, the pair of test patterns includes a plurality of pairs of pattern blocks, and at least a part of the plurality of pairs of pattern blocks is at least a part of another pair of pattern blocks. The recording means records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning means, and the plurality of pairs of pattern blocks during the backward movement. The pattern block included in the other is recorded.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
First embodiment
First, the 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 sheet holding mechanism 140 that face each other with a space therebetween. A sheet 192 as a recording medium is passed between the carriage 110 and the sheet holding mechanism 140. The sheet 192 is sandwiched between a pair of conveyance rollers composed of a conveyance roller 152 and a nip roller 154 and a pair of sheet discharge rollers composed of a sheet discharge roller 162 and a nip roller 164, and is conveyed from the top to the bottom of the figure by these roller pairs.
[0021]
The sheet holding mechanism 140 includes a platen 142 in which a large number of holes are formed, and a fan 148 for pulling the internal space (platen chamber) 144 of the sheet holding mechanism 140 to a negative pressure. While being conveyed, the sheet 192 is sucked to the platen 142 by the negative pressure generated by the fan 148.
[0022]
The carriage 110 includes a recording unit 120 that is a recording unit for recording an image on a sheet 192 and a CCD unit 130 that is a reading unit for reading an image recorded on the sheet 192. 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.
[0023]
The image recording apparatus 100 further includes a carriage control unit 170 that controls the carriage 110. The carriage control unit 170 controls the recording unit so that a carriage drive mechanism 172 that is a scanning unit for moving the carriage 110 along the main scanning axis and a test image including a pair of test patterns are recorded on the sheet 192. A recording control unit 174 that is a control unit, and an image shift calculation unit 176 that is a calculation unit that calculates a relative recording position shift amount of the pair of test patterns based on the correlation between the density data of the pair of test patterns. have.
[0024]
The carriage 110 can be moved along the main scanning axis by the carriage driving mechanism 172. While the carriage 110 is moved along the main scanning axis, the recording unit 120 records a test image including a pair of test patterns on the paper 192.
[0025]
The pair of test patterns may be composed of a pair of pattern blocks or a plurality of pairs of pattern blocks. That is, each of the pair of test patterns may be composed of a single pattern block or a plurality of pattern blocks.
[0026]
The recording unit 120 includes one recording head in an image forming apparatus for monochrome printing, and includes a plurality of recording heads in an image forming 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 forming apparatus.
[0027]
First example of recording head
An example of 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 line along the sub-scanning axis at a constant pitch. In other words, the recording head 122 is composed of a single unit 210 having one nozzle row 212.
[0028]
In such an image forming apparatus using the recording head 122, the formation of ink dots in the region traversed by the nozzle row 212 of the recording head 122 by the movement of the carriage 110 along the main scanning axis is usually performed along the sub-scanning axis. The formation of the ink dots in the forward path and the formation of the ink dots in the backward path are combined so that the ink dots can be formed without gaps.
[0029]
For example, in order to record a single straight line extending along the sub-scanning axis, ink dots are formed by ejecting ink from all the ink jet nozzles at a predetermined position on the forward path, and the paper 192 is pitched. The ink is moved along the sub-scanning axis by a distance equivalent to half of the distance, and ink is ejected from all the ink-jet nozzles at the same position in the main scanning direction as the ink dots formed in the forward path in the return path. As a result, a large number of ink dot rows, that is, straight lines, are arranged along the sub-scanning axis without any gap.
[0030]
In such an image forming apparatus provided with one or a plurality of recording heads 122, each of the recording heads 122 or the plurality of recording heads 122 has the ink ejection timing appropriately adjusted between the forward path and the backward path. It is necessary to For this reason, one of the pair of test patterns is recorded in the forward path, and the other of the pair of test patterns is recorded in the backward path.
[0031]
Further, in an image forming apparatus including a plurality of recording heads 122 for color printing, it is necessary to appropriately adjust the ink ejection timing between any two recording heads having different colors. For this reason, one of the pair of test patterns is recorded by one recording head 122, and the other of the pair of test patterns is recorded by another recording head 122.
[0032]
Second example of recording head
An example of another recording head included in the recording unit 120 is shown in FIG. As shown in FIG. 3, another recording head 124 is composed of a single unit 220 having a large number of recording elements (inkjet nozzles) arranged in a fixed pitch in two rows along the sub-scanning axis. . In other words, the recording head 122 is composed of a single unit 220 having a pair of nozzle rows 222 and 224.
[0033]
The nozzle row 222 and the nozzle row 224 are displaced along the sub-scanning axis by a distance corresponding to half the pitch of the inkjet nozzles.
[0034]
The number of nozzle rows included in the unit 220 is not limited to two. The unit 220 may have three or more nozzle rows.
[0035]
In such an image forming apparatus using the recording head 124, the formation of ink dots in the region traversed by the nozzle rows 222 and 224 of the recording head 124 by the movement of the carriage 110 along the main scanning axis is usually performed on the main scanning axis. During one direction of movement along, i.e., either on the way out or on the way back.
[0036]
For example, in order to record a single straight line extending along the sub-scanning axis, ink is ejected from all inkjet nozzles of one nozzle row (for example, nozzle row 222) at a specific position with respect to the main scanning axis. Forming dots, and then ejecting ink from all inkjet nozzles of the other nozzle row (for example, nozzle row 224) at a specific position with respect to the main scanning axis, i.e., the same position with respect to the main scanning axis. Form. As a result, a large number of ink dot rows, that is, straight lines, are arranged along the sub-scanning axis without any gap.
[0037]
In such an image forming apparatus including one or a plurality of recording heads 124, each of the recording head 124 or the plurality of recording heads 124 has an ink ejection timing between the nozzle array 222 and the nozzle array 224. Need to be adjusted properly. For this reason, during movement in one direction along the main scanning axis, that is, in either the forward path or the backward path, one of the pair of test patterns is recorded, and then the other of the pair of test patterns is recorded.
[0038]
In addition, the formation of ink dots by the nozzle row 222 and the formation of ink dots by the nozzle row 224 may be performed in each of the forward path and the backward path. For example, ink dots may be formed by the nozzle row 222 in the forward path, and ink dots may be formed by the nozzle row 224 in the return path. In this case, one of the pair of test patterns is recorded on the forward path, and the other of the pair of test patterns is recorded on the return path.
[0039]
Further, in an image forming apparatus including a plurality of recording heads 124 for color printing, it is necessary to appropriately adjust the ink ejection timing between any two recording heads having different colors. Therefore, one of the pair of test patterns is recorded by one recording head 124, and the other of the pair of test patterns is recorded by another recording head 124.
[0040]
Third example of recording head
An example of still another recording head included in the recording unit 120 is shown in FIG. As shown in FIG. 4, the recording head 126 includes two units 230 and 240 arranged side by side along the main scanning axis. Each of the units 230 and 240 has a large number of recording elements (inkjet nozzles) arranged in a line along the sub-scanning axis at a constant pitch. In other words, the recording head 126 is composed of two units 230 and 240 each having one nozzle row 232 and 242.
[0041]
The unit 230 and the unit 240 are arranged such that the nozzle row 232 and the nozzle row 242 are displaced along the sub-scanning axis by a distance corresponding to half the pitch of the inkjet nozzles.
[0042]
The number of units constituting the recording head 126 is not limited to two. The recording head 126 may be composed of three or more units.
[0043]
In such an image forming apparatus using the recording head 124, the ink dots are usually applied to an area crossed by the recording head 126 (more precisely, the nozzle row 232 and the nozzle row 242) due to the movement of the carriage 110 along the main scanning axis. Formation takes place during movement in one direction along the main scan axis, i.e., either on the forward path or on the return path.
[0044]
For example, to record a single straight line extending along the sub-scanning axis, all inkjet nozzles in a nozzle row (eg, nozzle row 232) of one unit (eg, unit 230) at a specific position with respect to the main scanning axis. Ink is ejected from the nozzles to form ink dots, and then the nozzle row (for example, nozzle row 242) of the other unit (for example, unit 240) at the specific position with respect to the main scanning axis, that is, the same position with respect to the main scanning axis. Ink is ejected from all of the inkjet nozzles to form ink dots. As a result, a large number of ink dot rows, that is, straight lines, are arranged along the sub-scanning axis without any gap.
[0045]
In such an image forming apparatus including one or a plurality of recording heads 126, each of the recording head 126 or the plurality of recording heads 126 has an ink ejection timing of the nozzle row 232 of the unit 230 and the unit 240. It is necessary to adjust appropriately between the nozzle row 242 and each other. For this reason, during movement in one direction along the main scanning axis, that is, in either the forward path or the backward path, one of the pair of test patterns is recorded, and then the other of the pair of test patterns is recorded.
[0046]
Further, the ink dot formation by the nozzle row 232 of the unit 230 and the ink dot formation by the nozzle row 242 of the unit 240 may be performed in each of the forward path and the backward path. For example, ink dots may be formed by the nozzle row 232 of the unit 230 in the forward path, and ink dots may be formed by the nozzle row 242 of the unit 240 in the backward path. In this case, one of the pair of test patterns is recorded on the forward path, and the other of the pair of test patterns is recorded on the return path.
[0047]
Further, in an image forming apparatus including a plurality of recording heads 126 for color printing, it is necessary to properly adjust the ink ejection timing between any two recording heads having different colors. Therefore, one of the pair of test patterns is recorded by one recording head 126, and the other of the pair of test patterns is recorded by another recording head 126.
[0048]
Fourth example of recording head
An example of another recording head included in the recording unit 120 is shown in FIG. As shown in FIG. 5, the recording head 128 is composed of two units 250 and 260 arranged so as to be shifted along the sub-scanning axis. Each of the units 250 and 260 has a large number of recording elements (inkjet nozzles) arranged in a line at a constant pitch along the sub-scanning axis. In other words, the recording head 128 is composed of two units 250 and 260 each having one nozzle row 252 and 262.
[0049]
The units 250 and 260 are arranged so that the nozzle rows 252 and 262 are continuous with respect to the position along the sub-scanning axis, in other words, the positions of the nozzle rows 252 and 262 with respect to the sub-scanning axis of the inkjet nozzles are a constant pitch. Is located. Such a combination of a plurality of units is a technique often used in manufacturing a recording head having a large dimension along the sub-scanning axis.
[0050]
The number of units constituting the recording head 128 is not limited to two. The recording head 128 may be composed of three or more units.
[0051]
In such an image forming apparatus using the recording head 128, the ink is usually applied to a region traversed by the recording head 128 (more precisely, the nozzle rows 252 and 262 of the units 250 and 260) due to the movement of the carriage 110 along the main scanning axis. In the dot formation, the ink dot formation in the forward path and the ink dot formation in the backward path are combined so that the ink dots can be formed without gaps along the sub-scanning axis.
[0052]
For example, in order to record a single straight line extending along the sub-scanning axis, ink dots are formed by ejecting ink from all the ink jet nozzles at a predetermined position on the forward path, and the paper 192 is pitched. The ink is moved along the sub-scanning axis by a distance equivalent to half of the distance, and ink is ejected from all the ink-jet nozzles at the same position in the main scanning direction as the ink dots formed in the forward path in the return path. As a result, a large number of ink dot rows, that is, straight lines, are arranged along the sub-scanning axis without any gap.
[0053]
In such an image forming apparatus including one or a plurality of recording heads 128, each of the one recording head 128 or the plurality of recording heads 128 has the ink ejection timing properly adjusted between the forward path and the backward path. It is necessary to For this reason, one of the pair of test patterns is recorded in the forward path, and the other of the pair of test patterns is recorded in the backward path.
[0054]
Further, in an image forming apparatus including a plurality of recording heads 128 for color printing, it is necessary to appropriately adjust the ink ejection timing between any two recording heads having different colors. For this reason, one of the pair of test patterns is recorded by one recording head 128, and the other of the pair of test patterns is recorded by another recording head 128.
[0055]
As described above, the adjustment of the ink ejection timing includes the adjustment of the ejection timing between the forward path and the backward path for one recording head, and the ejection between any two recording heads for a plurality of recording heads. There is a timing adjustment and an ejection timing adjustment between any two nozzle rows for a single recording head having a plurality of nozzle rows. Both of these adjustments are performed by the same method.
[0056]
Therefore, the adjustment of the ejection timing between the forward path and the backward path relating to one black recording head will be described below as a representative. In the following description, it is assumed that the black recording head has 496 inkjet nozzles, and the inkjet nozzles are arranged at a nozzle pitch of 360 dpi.
[0057]
Test image recording (printing)
For example, as shown in FIG. 6, the test image includes a pair of test patterns 312 and 314 and a black pattern 316 for black level adjustment described later. The test pattern is recorded by one-pass bidirectional printing. That is, in FIG. 6, the test pattern 312 is recorded, for example, in the forward path, and the test pattern 314 is recorded in the backward path.
[0058]
The test patterns 312 and 314 are both composed of a single pattern block. A preferred pair of test patterns 312, 314 has a high correlation. For this reason, the pattern block is composed of the same pattern elements, for example, rectangular pattern elements having a width of 5 dots. The test patterns 312, 314 are recorded with a shift of 64 dots, for example, 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 recorded.
[0059]
When the test pattern is recorded, no paper is transported between the forward recording and the backward recording. This is because the test pattern recorded in the return path is recorded at a position deviated from the original recording position when the sheet is not accurately conveyed due to the skew of the sheet at the time of conveying the sheet. This is to avoid the error amount due to the sheet conveyance in the finally obtained reciprocating timing deviation amount.
[0060]
Reading test patterns
In the following description, it is assumed that the CCD unit 130 has a reading resolution of 1440 dpi.
[0061]
As shown in FIG. 7, the paper 192 is transported downstream in the paper transport direction, and the test image including the test patterns 312 and 314 and the black pattern 316 is disposed below the CCD unit 130 in the carriage 110. To do. Subsequently, the carriage 110 is moved to place the CCD unit 130 above the black pattern 316.
[0062]
At this position (the position shown in FIG. 7), 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 using the white background portion of the paper at that position. This brightness adjustment is performed by a known method.
[0063]
After the white level adjustment is completed, the paper 192 is conveyed upstream in the paper conveyance direction until the CCD unit 130 detects the black pattern 316 while the position of the CCD unit 130 is fixed. As the sheet 192 is conveyed, the imaging area of the CCD unit 130 changes from the white background of the sheet 192 to the black background of the black pattern 316, and the output signal of the CCD unit 130 also changes accordingly. A printer control unit (not shown) recognizes that the CCD unit 130 is facing the black pattern 316 as shown in FIG. 8 based on the output signal of the CCD unit 130, and in response to the recognition, paper The conveyance of 192 is stopped.
[0064]
The black level of the CCD unit 130 is adjusted at a position where the CCD unit 130 faces the black pattern 316. This brightness adjustment is performed by a known method.
[0065]
After the black level adjustment is completed, in order to read the test pattern, the sheet 192 is further conveyed upstream in the sheet conveying direction, and the CCD unit 130 is disposed immediately before the upper ends of the test patterns 312 and 314.
[0066]
Thereafter, the paper 192 is transported by a minute transport amount, for example, by a transport amount when the drive pulse of the transport motor is set to 20 pulses (ideally, a distance corresponding to one dot line). The CCD unit 130 reads the test patterns 312 and 314 (more precisely, the brightness of the optical image) for each minute conveyance. 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, the series of operations of paper conveyance, image reading, and data storage are continued.
[0067]
Calculating the recording position deviation of a pair of test patterns
Next, calculation of the relative recording position deviation amount along the main scanning axis of the pair of test patterns 312 and 314 will be described. In this embodiment, the amount of deviation is calculated using a cross-correlation function.
[0068]
For a certain two signals r1 (x) and r2 (x), these cross-correlation functions Φ12 (τ) are expressed by the following equation (1).
[0069]
Φ12 (τ) = ∫r1 (x) r2 (x−1τ) dx (1)
Here, τ indicates the distance between the two signals. Φ12 (τ) takes a maximum value when the signal r1 (x) matches the signal r2 (x).
[0070]
In the actual processing, as shown in FIG. 9, the optical images 312i and 314i of the test patterns 312 and 314 read by the CCD unit 130 are recorded in the return path with the optical image 312i of the test pattern 312 recorded in the forward path. The test pattern 314 is divided into an optical image 314i. Since the resolution at the time of recording is 360 dpi and the CCD resolution is 1440 dpi, the optical image division width is expressed by the following equation (2).
[0071]
Optical image division width = 64 dots (shift amount during recording) × (1440 dpi ÷ 360 dpi) (2)
Next, the data of the respective optical images 312i and 314i are summed in the sub-scanning direction (the reading direction of the CCD unit 130), and the added density data (FIG. 10) of the optical image 312i and the added density data of the optical image 314i ( FIG. 11) is obtained.
[0072]
Subsequently, the cross-correlation function is obtained by setting the addition density data of the optical image 312i in the sub-scanning direction as r1 (x) and the addition data in the sub-scanning direction of the optical image 314i as r2 (x). The position indicating the value is calculated. The position value calculated in this way represents the recording position deviation amount γtp1440 of the optical images 312i and 314i of the pair of test patterns 312 and 314.
[0073]
The recording position deviation amount γtp1440 calculated in this way is for the optical images 312i and 314i read at the resolution of 1440 dpi. Therefore, the recording position deviation of the actual test patterns 312 and 314 recorded at the resolution of 360 dpi. The quantity γtp360 is expressed by the following equation (3).
[0074]
γtp360 = γtp1440 ÷ (1440 dpi ÷ 360 dpi) (3)
The recording position shift amount γtp 360 includes a shift amount given in order to avoid mutual overlap when the test patterns 312 and 314 are recorded. Accordingly, the recording position deviation amount γtm to be obtained is a value obtained by subtracting the recording amount of deviation 64 dots from the previously obtained recording position deviation amount γtp360. That is, the recording position deviation amount γtm to be obtained is expressed by the following equation (4).
[0075]
γtm = γtp360−64 (4)
In this embodiment, since the relative recording position deviation amount of the pair of test patterns recorded for adjusting the ink ejection timing is obtained using the cross-correlation function of the density data of the pair of test patterns, the recording is performed. The amount of displacement can be calculated in a short time and with high accuracy.
[0076]
First variation of test pattern
As described above, the pair of test patterns is not limited to the one composed of a pair of pattern blocks. The pair of test patterns may be composed of a plurality of pairs of pattern blocks.
[0077]
In this modification, as shown in FIG. 12, the pair of test patterns includes a pair of pattern blocks 332 and 334, another pair of pattern blocks 336 and 338, and another pair of pattern blocks 340 and 342. Is included. For example, the pattern blocks 332, 336, and 340 included in one of the pair of test patterns are recorded in the forward path, and the pattern blocks 334, 338, and 342 included in the other of the pair of test patterns are recorded in the backward path.
[0078]
The pattern blocks 332, 334, 336, 338, 340, 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 pattern blocks 332, 334, 336, 338, 340, 342 are arranged at a pitch of 64 dots along the main scanning axis.
[0079]
The pattern blocks 332, 334, 336, 338, 340, and 342 are all composed of the same pattern element, for example, a rectangular pattern element having a width of 5 dots. The pattern blocks 332, 334, 336, 338, 340, 342 may be recorded so that all of them fall within the reading width of the CCD unit 130.
[0080]
The width of the rectangular pattern element of the pattern block is not limited to 5 dots. Further, the number of pattern blocks is not limited to six. Further, the shift amount of the pattern block is not limited to 64 dots. The width of the rectangular pattern element, the number of pattern blocks 6 and the amount of pattern block shift are arbitrary under the conditions that the pattern blocks do not overlap each other, preferably under the condition that all the pattern blocks fit within the reading width of the CCD unit 130. May be changed to
[0081]
As shown in FIG. 13, the data read by the CCD unit 130 includes optical images 332i, 336i, and 340i of pattern blocks 332, 336, and 340 recorded on the forward path that constitutes one of a pair of test patterns. It is divided into optical images 334i, 338i, and 342i of pattern blocks 334, 338, and 342 recorded on the return path that constitutes the other of the pair of test patterns.
[0082]
For the recording position deviation amount of a pair of test patterns, for example, for each of a plurality of pairs of pattern blocks, the recording position deviation amount between the pair of pattern blocks is calculated using the cross-correlation function by the method described above. Then, the plurality of calculated recording position deviation amounts are averaged.
[0083]
Alternatively, the recording position shift amount of the pair of test patterns may be obtained by using the cross-correlation function by the above-described method for the pattern block group recorded in the forward path and the pattern block group recorded in the backward path. .
[0084]
According to this modification, since the number of samples is large, it is effective for improving the accuracy of the required recording position deviation amount.
[0085]
Second variation of test pattern
The plurality of pattern blocks need not be composed of the same pattern element. The plurality of pattern blocks may be configured with different pattern elements for each pair of pattern blocks.
[0086]
In the present modification, as shown in FIG. 17, the pair of test patterns includes a pair of pattern blocks 362 and 364 composed of rectangular pattern elements having a width of 5 dots, and a rectangular pattern element having a width of 10 dots. And another pair of pattern blocks 370 and 372 each including a rectangular pattern element having a width of 4 dots. These six pattern blocks 362, 364, 366, 368, 370, 372 are arranged at a pitch of 64 dots along the main scanning axis.
[0087]
This modification has the following advantages compared to the first modification.
[0088]
In the first modification, for example, as shown in FIG. 14, consider a case where one pattern block 342 out of six pattern blocks 332, 334, 336, 338, 340, 342 is missing. In this case, as shown in FIG. 15, the addition density data 332n, 334n, 336n, 338n, and 340n of the pattern blocks 332, 334, 336, 338, and 340n are obtained, but the addition density data 342n of the missing pattern block 342 is obtained. (Indicated by the dashed line) is not obtained. In FIG. 15, the addition density data 332n, 336n, and 340n corresponding to the pattern blocks 332, 336, and 340 recorded in the forward path are on the upper side, and the addition density data 334n corresponding to the pattern blocks 334 and 338 recorded in the return path are shown. 338n is shown on the lower side.
[0089]
FIG. 16 shows the cross-correlation function obtained for the added density data shown in FIG. As shown in FIG. 16, this cross-correlation function has a pair of peaks 352 and 354 showing the same maximum value. In FIG. 15, the added density data 332n and 336n are obtained by shifting the lower added density data 334n and 338n by 64 dots to the left along the main scanning axis with respect to the upper added density data 332n, 336n and 340n. And the addition density data 334n and 338n and the correlation between the addition density data 336n and 340n and the addition density data 334n and 338n due to a shift of 64 dots to the right along the main scanning axis. This is because they are equal.
[0090]
Thus, in the first modification, when some of the plurality of the same pattern blocks are lost, the cross-correlation function has a pair of peaks 352 and 354 showing the same maximum value. It is difficult to distinguish the peak representing
[0091]
On the other hand, in the second modified example, as shown in FIG. 17, the pair of pattern blocks 362 and 364 are both composed of rectangular pattern elements having a width of 5 dots, and another pair of pattern blocks 366 and 368 are Both are composed of rectangular pattern elements having a width of 10 dots, and another pair of pattern blocks 370 and 372 are both composed of a rectangular pattern having a width of 4 dots.
[0092]
Since the widths of the pattern elements are different for each pair of pattern blocks in this way, the correlation between two pattern blocks included in different pairs of pattern blocks is the correlation between the two pattern blocks that make up the same pair of pattern blocks. Compared to the lower one. Accordingly, the obtained cross-correlation function has only one peak indicating the maximum value, and the recording position deviation amount can be calculated stably and easily.
[0093]
The number of pattern blocks and the width of the rectangular pattern are not limited to the values described above, and may be arbitrarily changed.
[0094]
Third variation of test pattern
All of the plurality of pattern blocks need not be composed of a single pattern element. Some or all of the plurality of pattern blocks may be composed of a plurality of pattern elements.
[0095]
In the present modification, as shown in FIG. 18, the pair of test patterns includes a pair of pattern blocks 382 and 384 including two rectangular pattern elements 382a, 382b, 384a and 384b, and three rectangular pattern elements 386a. 386b, 386c, 388a, 388b, and 388c, and another pair of pattern blocks 390 and 392 that are formed of one rectangular pattern element. These six pattern blocks 382, 384, 386, 388, 390, 392 are arranged at a pitch of 64 dots along the main scanning axis.
[0096]
FIG. 19 shows added density data obtained by adding an optical image read by the CCD unit 130 to the pattern block in the sub-scanning direction. As can be easily imagined from FIG. 19, the correlation between two pattern blocks included in different pairs of pattern blocks is similar to the correlation between two pattern blocks constituting the same pair of pattern blocks, as in the second modification. And low. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0097]
Fourth variation of test pattern
The plurality of pattern blocks constituting the pair of test patterns need not be arranged at a constant pitch. The plurality of pattern blocks may be arranged at different intervals along the main scanning axis. In other words, the pattern block is recorded so that the pattern block comes to a different position for each pair of pattern blocks in the area equally divided along the main scanning axis of the reading range by the CCD unit 130. May be.
[0098]
In the present modification, as shown in FIG. 20, the pair of test patterns is arranged on the left side with a pair of pattern blocks 412 and 414 located on the left side with respect to the area equally divided into six reading ranges. It includes another pair of pattern blocks 416 and 418 positioned, and another pair of pattern blocks 420 and 422 positioned substantially in the center. In other words, the six pattern blocks 412, 414, 416, 418, 420, 422 are not arranged at a constant pitch along the main scanning axis.
[0099]
The added density data in the sub-scanning direction obtained for such a pattern block is shown in FIG. As can be easily imagined from FIG. 21, as in the second and third modifications, the correlation between two pattern blocks included in different pairs of pattern blocks is two patterns constituting the same pair of pattern blocks. It becomes low compared with the correlation of a block. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0100]
The fifth variation of the test pattern
Each of the one or more pattern elements constituting the pattern block is not limited to a rectangular pattern element. Each of the one or more pattern elements constituting the pattern block is a pattern element having an arbitrary shape, for example, a pattern element such as a square, a circle or a triangle, or a pattern element such as a character or symbol, for each pair of pattern blocks. May be changed.
[0101]
In this modified example, as shown in FIG. 22, the pair of test patterns includes a pair of pattern blocks 432 and 434 configured by triangular pattern elements and another pair of pattern blocks configured by circular pattern elements. 436 and 438, and yet another pair of pattern blocks 440 and 442 made up of floral pattern elements.
[0102]
In such a plurality of pattern blocks, as in the second and third modifications, the correlation between two pattern blocks included in different pairs of pattern blocks is two patterns constituting the same pair of pattern blocks. It becomes low compared with the correlation of a block. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0103]
Sixth variation of test pattern
It is not necessary for one pattern block to have a uniform density. One pattern element constituting one pattern block may include a plurality of portions having different densities, for example, a white data portion and a halftone data portion. A plurality of pattern elements constituting one pattern block may have different densities.
[0104]
In this modification, as shown in FIG. 23, the pair of test patterns includes a pair of pattern blocks 452 and 454 having a uniform density throughout and another pair including a portion 464 having a low density. Pattern blocks 456 and 458 and yet another pair of pattern blocks 460 and 462 including a low density portion 466.
[0105]
In such a plurality of pattern blocks, as in the second and third modifications, the correlation between two pattern blocks included in different pairs of pattern blocks is the two patterns constituting the same pair of pattern blocks. It becomes low compared with the correlation of a block. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0106]
Seventh variation of test pattern
The plurality of pattern blocks do not need to have the same width. The plurality of pattern blocks may have different widths for each pair of pattern blocks. In other words, the reading range by the CCD unit 130 may be divided unevenly along the main scanning axis according to the width of the pattern block.
[0107]
In this modification, as shown in FIG. 24, a pair of test patterns includes a pair of pattern blocks 472 and 474 configured by rectangular pattern elements, and another pair of pattern blocks 476 configured by circular pattern elements. 478 and a further pair of pattern blocks 480, 482 comprised of three rectangular pattern elements 486a, 486b, 486c, 488a, 488b, 488c.
[0108]
Therefore, among the six pattern blocks constituting the three types of image pairs, the pattern blocks 472 and 474 have the narrowest width, and the pattern blocks 480 and 482 have the widest width. Accordingly, the divided area of the reading range that covers the pattern blocks 472 and 474 having the narrowest width has a width of 300 dots that is the narrowest, and the divided area of the reading range that covers the widest pattern blocks 480 and 482 is 500 which is the widest. The divided area of the reading range having the dot width and the pattern blocks 476 and 478 having the intermediate width has a width of 400 dots. That is, the reading range is divided unevenly according to the width of the pattern block.
[0109]
The division width of the reading range is not limited to the above-described value, and may be arbitrarily changed according to the width of the pattern block.
[0110]
Eighth variation of test pattern
The pair of pattern blocks need not be arranged side by side along the main scanning axis. The pair of pattern blocks may be recorded apart from each other along the main scanning axis, that is, with another pattern block interposed therebetween.
[0111]
In this modification, as shown in FIG. 25, the pair of test patterns includes a pair of pattern blocks 512 and 514, another pair of pattern blocks 516 and 518, and another pair of pattern blocks 520 and 522. These six pattern blocks 512, 516, 520, 514, 518, 522 are arranged in order at a pitch of 64 dots along the main scanning axis. The pattern blocks 512, 516, and 520 are recorded on the forward path, for example, and the pattern blocks 514, 518, and 522 are recorded on the backward path. The pair of pattern blocks are recorded with a shift of 64 × 3 = 192 dots along the main scanning axis.
[0112]
The pair of pattern blocks 512 and 514 includes a pair of rectangular patterns 512a and 512b, 514a and 514b, respectively, and are located with the pattern block 516 and the pattern block 520 interposed therebetween. Another pair of pattern blocks 516 and 518 are both rectangular patterns having a relatively narrow width, and are positioned with the pattern block 520 and the pattern block 514 interposed therebetween. Further, another pair of pattern blocks 520 and 522 is a rectangular pattern having a relatively wide width, and is positioned with the pattern block 514 and the pattern block 518 interposed therebetween.
[0113]
In such a plurality of pattern blocks, as in the second and third modifications, the correlation between two pattern blocks included in different pairs of pattern blocks is the two patterns constituting the same pair of pattern blocks. It becomes low compared with the correlation of a block. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0114]
Ninth variation of test pattern
Each of the plurality of pairs of pattern blocks need not be recorded separately along the main scanning axis. That is, the plurality of pairs of pattern blocks may include at least a pair of pattern blocks recorded separately along the main scanning axis and at least a pair of pattern blocks recorded adjacent to each other along the main scanning axis. .
[0115]
In the present modification, as shown in FIG. 26, the pair of test patterns includes a pair of pattern blocks 532 and 534, another pair of pattern blocks 536 and 538, and another pair of pattern blocks 540 and 542. These six pattern blocks 532, 536, 534, 538, 540, 542 are arranged in order at a pitch of 64 dots along the main scanning axis. The pattern blocks 532, 536, and 540 are recorded, for example, in the forward path, and the pattern blocks 534, 538, and 542 are recorded in the backward path.
[0116]
The pair of pattern blocks 532 and 534 are both rectangular patterns having a relatively wide width, and are located with the pattern block 536 interposed therebetween. Another pair of pattern blocks 536 and 538 is composed of a pair of rectangular patterns 536a and 536b, 538a and 538b, respectively, and is located with the pattern block 534 interposed therebetween. Further, another pair of pattern blocks 540 and 542 are both rectangular patterns having a relatively narrow width and are located adjacent to each other.
[0117]
That is, the pair of pattern blocks 532 and 534 is recorded with a shift of 64 × 2 = 128 dots along the main scanning axis, and the pair of pattern blocks 536 and 538 is similarly recorded along the main scanning axis with 64 × 2 = 128. The pattern is recorded with a dot shift, and the pair of pattern blocks 540 and 542 are recorded with a shift of 64 dots along the main scanning axis. In other words, both the pattern blocks 532 and 534 and the pattern blocks 536 and 538 are arranged at a pitch of 128 dots along the main scanning axis, and the pattern blocks 540 and 542 are arranged at a pitch of 64 dots along the main scanning axis. Yes.
[0118]
The recording position deviation amounts of the pair of test patterns to be obtained are calculated by, for example, calculating the recording position deviation amounts between them using a cross-correlation function for each of the plurality of pattern block pairs. It is obtained by averaging the amount of deviation.
[0119]
Alternatively, the recording position shift amount of the pair of test patterns to be obtained may be obtained using a cross-correlation function for the pattern block group recorded in the forward path and the pattern block group recorded in the backward path.
[0120]
In such a plurality of pattern blocks, as in the second and third modifications, the correlation between two pattern blocks included in different pairs of pattern blocks is the two patterns constituting the same pair of pattern blocks. It is lower than the correlation between block pairs. For this reason, the obtained cross-correlation function has only one peak indicating the maximum value. Therefore, even when some of the plurality of pattern blocks are missing, the recording position deviation amount can be calculated stably and easily.
[0121]
Modification of recording method (tenth modification of test pattern)
The test pattern recording method is not limited to a method in which the sheet is not conveyed between the recording in the forward path and the recording in the backward path. That is, when the test pattern is recorded, the sheet may be conveyed between the recording on the outward path and the recording on the return path.
[0122]
In this modification, the test image has a pair of reference patterns 552 and a pair of test patterns, as shown in FIG. 27. The pair of test patterns includes pattern blocks 562 and 564, and A pair of pattern blocks 566 and 568 and another pair of pattern blocks 570 and 572 are included. The reference pattern 552 and the three pattern blocks 562, 566, and 570 are sequentially arranged along the main scanning axis, and the reference pattern 554 and the three pattern blocks 564, 568, and 572 are arranged along the main scanning axis below them. Are in order. Further, the reference patterns 552 and 554, the pattern blocks 562 and 564, the pattern blocks 566 and 568, and the pattern blocks 570 and 572 are arranged along the sub-scanning axis. That is, the reference patterns 552 and 554 and the pattern blocks 562, 566, 570, 564, 568, and 572 are aligned in a lattice pattern along the main scanning axis and the sub scanning axis.
[0123]
For example, the reference pattern 552 and the three pattern blocks 562, 566, and 570 are recorded in the first band by forward scanning. The reference pattern 554 is recorded in the second band by the same scanning direction as that for recording the reference pattern, that is, forward scanning. Further, the three pattern blocks 564, 568, and 572 are recorded in the second band in the direction opposite to the reference pattern recording, that is, by backward scanning. Between the pattern recording of the first band and the pattern recording of the second band, the sheet is conveyed by a distance corresponding to the width along the sub-scanning axis of the first band.
[0124]
The pair of reference patterns 552 and 554 are both composed of rectangular pattern elements, the pair of pattern blocks 562 and 564 are both composed of rectangular pattern elements having a relatively narrow width, and the pair of pattern blocks 566 and 568 are a pair of rectangles, respectively. The patterns 566a and 566b are composed of 568a and 568b, and the pair of pattern blocks 570 and 572 are both composed of a relatively wide rectangular pattern.
[0125]
Such a plurality of pattern blocks arranged in a grid pattern is particularly effective for a carriage having a CCD unit that can read only a narrow area in one scan along the sub-scanning axis.
[0126]
Since the sheet is conveyed during recording, it is conceivable that a recording error along the main scanning axis may occur due to skew (skew) due to the sheet conveyance. The shift amount δ skew along the main scanning axis due to the sheet conveyance is obtained using the cross-correlation function for the reference pattern 552 and the reference pattern 554. Therefore, a recording error due to skew or the like is preferably corrected based on the obtained deviation amount Δskew. Also, it is possible to simultaneously detect an abnormality in paper conveyance from the deviation amount δ skew.
[0127]
The actual deviation amount is obtained by using the cross-correlation function for the pattern blocks 562, 566, and 570 recorded in the forward path and the pattern blocks 564, 568, and 572 recorded in the backward path by the above-described method.
[0128]
In the plurality of images shown in FIG. 27, two rows of reference patterns and a plurality of pattern blocks arranged along the main scanning axis are recorded along the sub-scanning axis. A reference pattern and a plurality of pattern block rows arranged along the main scanning axis may be further added along the sub-scanning axis.
[0129]
Modified Example of CCD Unit (Another Useful Use Case of Test Pattern of Tenth Modified Example) The image recording apparatus may have a CCD unit that reads along the main scanning axis. The test image shown in FIG. 27 can be effectively applied to such an image recording apparatus.
[0130]
In the present modification, as shown in FIG. 28, the image recording apparatus has a CCD unit 134 that is moved along the main scanning axis. The CCD unit 134 is attached to a carriage, for example, and is moved along the main scanning axis by the movement of the carriage. Alternatively, the CCD unit 134 may be provided alone in the image recording apparatus, and the CCD unit 134 itself may be moved along the main scanning axis.
[0131]
In this modification, by obtaining a cross-correlation function with respect to the reference pattern 552 and the reference pattern 554, it is possible to simultaneously correct the paper conveyance skew and the CCD unit 134 mounting inclination.
[0132]
First, the correction of the inclination of the attachment of the CCD unit 134 will be described on the assumption that there is no skew in paper conveyance. Here, as shown in FIG. 29, the CCD unit 134 is functionally disassembled into a first band data reading unit 134a and a second band data reading unit 134b.
[0133]
As shown in FIG. 28, when the CCD unit 134 is not inclined with respect to the sub-scanning axis, the first band data reading unit 134a on the upper side of the CCD unit 134 and the second band data reading on the lower side are read. The unit 134b starts reading the reference pattern 552 and the reference pattern 554 simultaneously. As a result, as shown in FIG. 30, a reading optical image of the reference pattern 552 and the reference pattern 554 synchronized with respect to the CCD moving direction is obtained.
[0134]
On the other hand, when the CCD unit 134 is inclined with respect to the sub-scanning axis as shown in FIG. 31, the first band on the upper side of the CCD unit 134 is shown in FIG. The data reading unit 134a first starts reading the reference pattern 552 from the upper end side, and the second band data reading unit 134b below the CCD unit 134 starts reading the reference pattern 554 from the upper end side later.
[0135]
As a result, as shown in FIG. 33, read optical images of the reference pattern 552 and the reference pattern 554 having a deviation with respect to the CCD moving direction are obtained. The shift amount δinclination due to the inclination of the CCD unit 134 is obtained by using the cross-correlation function by the above-described method for the read optical images of the reference pattern 552 and the reference pattern 554.
[0136]
The deviation amount Δinclination thus obtained includes the deviation amount due to the skew of the paper when there is a skew of the paper due to the paper conveyance. Therefore, the recording position deviation amount to be finally obtained is calculated by calculating the cross correlation function for the deviation amount δinclination with respect to the pattern blocks 562, 566, 570 recorded in the forward path and the pattern blocks 564, 568, 572 recorded in the backward path. It is obtained by subtracting from the recording position deviation amount calculated using the above.
[0137]
Second embodiment
The image forming apparatus according to the second embodiment will be described below. This embodiment is different from the first embodiment only in the method of calculating the recording position deviation amount, and the apparatus configuration and the like are the same as those of the first embodiment. Further, the image modification examples described in the first embodiment can be applied to the present embodiment as they are.
[0138]
In the present embodiment, the relative value of the density data of the pair of test patterns is relatively changed, and the integrated value of the density data is sequentially calculated based on the correlation of the density data of each other. Then, the relative recording position deviation amount of the pair of test patterns is calculated.
[0139]
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 multi-value density data Integrated value of the comparison minimum value group, (4) integrated value of the comparison maximum value group of the multi-value density data, (5) integrated value of the difference between the multi-value density data, and (6) multi-value density data. One of the integral values of the products of the two is obtained, and the recording position deviation amount is calculated from the obtained peak value.
[0140]
(1) Calculation based on integral value of logical product of binarized density data
First, the addition density data of a pair of test patterns that are targets of the recording position deviation amount to be obtained is obtained, and binarized to obtain a pair of density data 612 and 614 as shown in FIG. Ask for. Binarization is an operation of comparing density data with a predetermined threshold, and converting density data above the threshold to 1 and density data below the threshold to 0.
[0141]
For a pair of binarized density data 612 and 614, the logical product (AND) is taken at an arbitrary value of x, and as shown in FIG. The logical product 622 is obtained, and the area of the logical product 622 is obtained (that is, the integral value is obtained). This operation is performed for an arbitrary d1. That is, in FIG. 34, the above-described series of calculations are performed while shifting the binarized density data 612 in the + x direction. As a result, as shown in FIG. 36, a graph showing the relationship between the shift between the pair of binarized density data 612 and 614 and the integral value of the logical product 622 is obtained.
[0142]
The integrated value of the logical product of the binarized density data is a value as the overlap of the pair of binarized density data 612 and 614 increases while the binarized density data 612 is shifted in the + x direction. Increases as the overlap decreases. That is, the integrated value of the logical product of a pair of binarized density data takes the maximum value when the pair of binarized density data overlaps most.
[0143]
In FIG. 36, the value of d1 giving the maximum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of binarized density data 612 and 614. Therefore, the recording position deviation amount of the pair of test patterns is obtained based on the graph of FIG.
[0144]
(2) Calculation based on the integrated value of the logical sum of binarized density data
First, similarly to the calculation of the recording position deviation amount based on the logical product described above, the addition density data of a pair of test patterns is obtained and binarized, and as shown in FIG. 34, a pair of binarization is performed. The obtained density data 612 and 614 are obtained.
[0145]
For a pair of binarized density data 612 and 614, the logical sum (OR) is taken at an arbitrary value of x, and as shown in FIG. The logical sum 632 is obtained, and the area of the logical sum 632 is obtained (that is, the integral value is obtained). This operation is performed for an arbitrary d1. That is, in FIG. 34, the above-described series of calculations are performed while shifting the binarized density data 612 in the + x direction. As a result, as shown in FIG. 38, a graph showing the relationship between the shift between the pair of binarized density data 612 and 614 and the integrated value of the logical sum 632 is obtained.
[0146]
The integrated value of the logical sum of the binarized density data becomes smaller as the overlap of the pair of binarized density data 612 and 614 increases while the binarized density data 612 is shifted in the + x direction. And increases as the overlap decreases. That is, the integrated value of the logical sum of a pair of binarized density data takes the minimum value when the pair of binarized density data overlaps most.
[0147]
In FIG. 38, the value of d1 giving the minimum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of binarized density data 612 and 614. Therefore, the recording position shift amount of the pair of test patterns is obtained based on the graph of FIG.
[0148]
(3) Calculation based on the integrated value of the comparison minimum value group of multi-value density data
First, as shown in FIG. 39, the addition density data 712 and 714 of a pair of test patterns which are targets of the recording position deviation amount to be obtained are obtained. The added density data 712 and 714 are multi-value density data.
[0149]
Next, as shown in FIG. 40, a comparison minimum value group 722 of a pair of multi-value density data 712 and 714 is taken. Here, the comparative minimum value means that density data at an arbitrary x of a pair of multi-value density data 712 and 714 is compared and a smaller density data value (minimum value) is obtained. Then, the comparative minimum value is acquired in the x direction, and the integral value of the minimum value group 722 is taken. Therefore, taking the integral value of the comparison minimum value group 722 of the pair of multi-value density data 712 and 714 is equivalent to superimposing the pair of multi-value density data 712 and 714 and obtaining the area of the overlapping portion. To do.
[0150]
This operation is performed for an arbitrary d2. That is, in FIG. 39, the above-described series of calculations is performed while shifting the multi-value density data 712 in the + x direction. Thereby, as shown in FIG. 41, a graph showing the relationship between the shift amount of the pair of density data 712 and 714 and the integral value of the comparison minimum value group 722 is obtained.
[0151]
While the density data 712 is shifted in the + x direction, the integral value of the comparison minimum value group between the density data increases as the overlap between the pair of density data 712 and 714 increases, and decreases as the overlap decreases. That is, the integral 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.
[0152]
In FIG. 41, the value of d2 giving the maximum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multi-value 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.
[0153]
(4) Calculation based on the integrated value of the comparison maximum value group between multi-value density data
First, similarly to the calculation of the recording position deviation amount based on the integrated value of the comparison minimum value group between the density data described above, as shown in FIG. 39, the pair of test patterns that are the targets of the recording position deviation amount to be obtained are shown. Addition density data 712 and 714 are obtained. The added density data 712 and 714 are multi-value density data.
[0154]
Next, as shown in FIG. 42, a comparison maximum value group 732 of a pair of multi-value density data 712 and 714 is taken. Here, the comparative maximum value means that density data at an arbitrary x of a pair of multi-value density data 712 and 714 is compared and a larger density data value (maximum value) is obtained. The maximum comparison value is acquired in the x direction, and the integral value of the maximum value group 732 is obtained. Therefore, taking the integral value of the comparison maximum value group 732 of the pair of multi-value density data 712 and 714 corresponds to superposing the pair of multi-value density data 712 and 714 and obtaining the area of the contour. .
[0155]
This operation is performed for an arbitrary d2. That is, in FIG. 39, the above-described series of calculations is performed while shifting the multi-value density data 712 in the + x direction. Thereby, as shown in FIG. 43, a graph showing the relationship between the shift amount of the pair of density data 712 and 714 and the integral value of the comparison maximum value group 732 is obtained.
[0156]
While the density data 712 is shifted in the + x direction, the integral value of the comparison maximum value group between the density data decreases as the overlap of the pair of density data 712 and 714 increases, and increases as the overlap decreases. That is, the integral value of the comparison maximum value group of the pair of density data takes the minimum value when the pair of density data overlaps most.
[0157]
In FIG. 43, the value of d2 giving the minimum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multi-value density data 712 and 714. Therefore, the recording position deviation amount of the pair of test patterns is obtained based on the graph of FIG.
[0158]
(5) Calculation based on the integrated value of the difference between multi-value density data
First, as shown in FIG. 39, similarly to the calculation of the recording position deviation amount based on the integral value of the comparison minimum value group between the density data described above, as shown in FIG. Addition density data 712 and 714 are obtained. The added density data 712 and 714 are multi-value density data.
[0159]
Next, as shown in FIG. 44, the absolute value 742 of the density difference at an arbitrary x of the pair of multi-value density data 712 and 714 is taken. Further, the integral value of the absolute value 742 of the difference between the pair of multi-value density data 712 and 714 is taken.
[0160]
This operation is performed for an arbitrary d2. That is, in FIG. 39, the above-described series of calculations is performed while shifting the multi-value density data 712 in the + x direction. As a result, as shown in FIG. 45, a graph showing the relationship between the shift amount of the pair of density data 712 and 714 and the integral value of the absolute value 742 of the difference between them is obtained.
[0161]
The integral value of the absolute value 742 of the difference between the density data decreases as the overlap of the pair of density data 712 and 714 increases while the density data 712 is shifted in the + x direction, and increases as the overlap decreases. In other words, the integral value of the absolute value of the difference between the pair of density data takes the minimum value when the pair of density data overlaps most.
[0162]
In FIG. 45, the value of d2 giving the minimum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multi-value density data 712 and 714. Therefore, the recording position deviation amount of the pair of test patterns is obtained based on the graph of FIG.
[0163]
(6) Calculation based on the integral value of the product of multi-value density data
First, similarly to the calculation of the recording position deviation amount based on the integrated value of the comparison minimum value group between the density data described above, as shown in FIG. 39, the pair of test patterns that are the targets of the recording position deviation amount to be obtained are shown. Addition density data 712 and 714 are obtained. The added density data 712 and 714 are multi-value density data.
[0164]
Next, as shown in FIG. 46, a density product 752 at an arbitrary x of a pair of multi-value density data 712 and 714 is obtained. Further, the integral value of the product 752 of the pair of multi-value density data 712 and 714 is taken.
[0165]
This operation is performed for an arbitrary d2. That is, in FIG. 39, the above-described series of calculations is performed while shifting the multi-value density data 712 in the + x direction. As a result, as shown in FIG. 47, a graph showing the relationship between the shift amount of the pair of density data 712 and 714 and the integral value of their product 752 is obtained.
[0166]
The integrated value of the product 752 between the density data increases as the overlap of the pair of density data 712 and 714 increases while the density data 712 is shifted in the + x direction, and decreases as the overlap decreases. That is, the integral value of the product of the pair of density data takes the maximum value when the pair of density data overlaps most.
[0167]
In FIG. 47, the value of d2 giving the maximum area indicates the recording position shift amount of the pair of test patterns corresponding to the pair of multi-value 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.
[0168]
The recording position deviation amount obtained above is the deviation amount in FIGS. 34 and 39, and the recording position deviation amount to be finally obtained is the deviation amount given at the time of test pattern recording from the recording position deviation amount obtained here. Is calculated by subtracting
[0169]
In this embodiment, since the relative recording position deviation amount of the pair of test patterns recorded for adjusting the ink ejection timing is obtained by using the correlation between the density data of the pair of test patterns, the recording is performed. The positional deviation amount can be calculated in a short time and with high accuracy.
[0170]
Although several embodiments have been specifically described so far with reference to the drawings, the present invention is not limited to the above-described embodiments, and all the embodiments performed without departing from the scope of the invention are not limited thereto. Including implementation.
[0171]
The present invention includes an image recording apparatus and an image recording position shift detection method described in the following sections.
[0172]
1. The image recording device
Recording means for recording an image on a recording medium;
Scanning means for moving the recording means along the main scanning axis, and the recording means displays a test image including a pair of test patterns on the recording medium while being moved along the main scanning axis by the scanning means. Record and further
Reading means for reading the pair of test patterns recorded on the recording medium by the recording means;
Calculation means for calculating a relative recording position shift amount of the pair of test patterns based on a correlation between density data of the pair of test patterns read by the reading means.
[0173]
2. In the image recording apparatus of item 1, the calculating means obtains a cross-correlation function of the density data of the pair of test patterns, and calculates a relative value of the pair of test patterns from a position where the cross-correlation function takes a maximum value. The amount of recording position deviation is calculated.
[0174]
3. In the image recording apparatus of item 1, the calculation means sequentially calculates an integrated value of density data based on a correlation between the density data of the pair of test patterns while relatively changing positions of the density data of the pair of test patterns. Then, the relative recording position shift amount of the pair of test patterns is calculated from the position where the integrated value becomes a peak.
[0175]
4). In the image recording apparatus according to item 3, the calculation means calculates an integral value from the sum of the density data of each other.
[0176]
5). In the image recording apparatus of item 4, the calculation means calculates an integral value from the logical product of the density data of each other, and a relative recording position shift of the pair of test patterns from a position where the integral value is maximized. Calculate the amount.
[0177]
6). In the image recording apparatus of item 4, the calculating means calculates an integrated value from the logical sum of the density data of each other, and the relative recording position shift of the pair of test patterns from the position where the integrated value is minimized. Calculate the amount.
[0178]
7. In the image recording apparatus of item 4, the calculating means calculates an integrated value of density data in a portion where the density data overlap each other, and the relative value of the pair of test patterns is determined from the position where the integrated value is maximized. The amount of recording position deviation is calculated.
[0179]
8). In the image recording apparatus according to item 4, the calculating means compares the density data with each other, calculates an integrated value based on a value with the smaller density data, and starts from the position where the integrated value becomes maximum. The relative recording position shift amount of the test pattern is calculated.
[0180]
9. In the image recording apparatus according to item 4, the calculating means compares the density data with each other, calculates an integrated value based on a value with the larger density data, and starts from the position where the integrated value is minimized. The relative recording position shift amount of the test pattern is calculated.
[0181]
10. In the image recording apparatus according to item 3, the calculating means calculates an integrated value from an absolute value of a difference between the density data, and records the pair of test patterns relative from a position where the integrated value is minimized. The amount of positional deviation is calculated.
[0182]
11. In the image recording apparatus of item 3, the calculating means calculates an integrated value from the product of the density data of each other, and the relative recording position shift amount of the pair of test patterns from the position where the integrated value is maximized. Is calculated.
[0183]
12 In the image recording apparatus according to the first aspect, the recording unit includes one inkjet head having a pair of nozzle rows, and the pair of test patterns are recorded by the pair of nozzle rows, respectively.
[0184]
13. In the image recording apparatus according to the first aspect, the recording unit is a pair of inkjet heads each having one nozzle row, and the pair of test patterns is recorded by the pair of inkjet heads.
[0185]
14 In the image recording apparatus of item 1, the pair of test patterns are the same pattern.
[0186]
15. In the image recording apparatus of item 1, the recording means is reciprocated along the main scanning axis by the scanning means, records one of the pair of test patterns during the forward movement, and moves during the backward movement. Record the other of the pair of test patterns.
[0187]
16. In the image recording apparatus of item 12 or 13, the recording unit records the pair of test patterns while being moved in one direction along the main scanning axis by the scanning unit.
[0188]
17. In the image recording apparatus of item 15 or 16, the pair of test patterns are recorded while being shifted along the main scanning axis.
[0189]
18. In the image recording apparatus of item 15 or 16, the pair of test patterns are recorded while being shifted along a sub-scanning axis orthogonal to the main scanning axis.
[0190]
19. In the image recording device of item 15 or 16, the pair of test patterns has a plurality of pairs of pattern blocks.
[0191]
20. In the image recording apparatus of item 19, the two test patterns constituting different pairs of pattern blocks are constituted by different pattern elements.
[0192]
21. In the image recording apparatus of item 19, the plurality of pattern blocks are arranged at a non-uniform pitch.
[0193]
22. In the image recording device according to Item 19, the pair of pattern blocks are positioned with a pattern block included in another pair of pattern blocks in between.
[0194]
23. In the image recording device of item 19, each of at least a pair of pattern blocks is composed of a plurality of pattern elements.
[0195]
24. 2. The control unit according to claim 1, further comprising a control unit configured to control a recording operation of the recording unit based on a relative recording position shift amount calculated by the calculating unit.
[0196]
25. Image recording position deviation detection method
A recording step of recording a test image including 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 calculation step of calculating a relative recording position shift amount of the pair of test patterns based on a mutual correlation between the read image data of the pair of test patterns.
[0197]
26. 26. The image misregistration detection method according to item 25, wherein the calculating step calculates a cross-correlation function between density data of the pair of test patterns, and calculates the pair of the correlation values from a position having the maximum value of the cross-correlation function. The relative recording position deviation of the test pattern is calculated.
[0198]
27. 26. The image misregistration detection method according to Item 25, wherein the calculating step includes a step of relatively changing the positions of the density data of the pair of test patterns and a correlation between the density data of each position. A step of sequentially calculating an integrated value of density data based on the step, a step of calculating a position where the integrated value becomes a peak, and a relative recording position shift amount of the pair of test patterns from the position where the integrated value becomes a peak The step of calculating.
[0199]
【The invention's effect】
According to the present invention, there is provided an image forming apparatus capable of calculating a relative recording position shift amount of a pair of test patterns formed for adjusting ink ejection timing in a short time. In addition, in this image forming apparatus, since the relative recording position deviation amount is obtained based on the correlation between the density data of the pair of test patterns, the image recording position deviation amount can be obtained with high accuracy. .
[Brief description of the drawings]
FIG. 1 shows an image recording apparatus according to the present invention.
FIG. 2 illustrates an example of one recording head included in the recording unit illustrated in FIG.
FIG. 3 illustrates an example of another recording head included in the recording unit illustrated in FIG.
4 shows an example of still another recording head included in the recording unit shown in FIG.
FIG. 5 shows an example of still another recording head included in the recording unit shown in FIG.
FIG. 6 shows a test image including a pair of test patterns and a black pattern.
7 shows a positional relationship of the CCD unit with respect to the image shown in FIG. 6 during focus adjustment and white level adjustment.
8 shows the positional relationship of the CCD unit with respect to the image shown in FIG. 6 during black level adjustment.
9 shows an optical image of a pair of test patterns shown in FIG. 6 read by a CCD unit.
10 shows added density data of the optical image of the left test pattern shown in FIG.
11 shows the added density data of the optical image of the right test pattern shown in FIG.
FIG. 12 shows a first modification of the test pattern.
13 shows an optical image of the six pattern blocks shown in FIG. 12 read by the CCD unit.
14 shows a state in which one of the six pattern blocks shown in FIG. 12 is missing.
FIG. 15 shows added density data obtained for the pattern block shown in FIG.
16 shows a cross-correlation function obtained for the added density data shown in FIG.
FIG. 17 shows a second modification of the test pattern.
FIG. 18 shows a third modification of the test pattern.
FIG. 19 shows added density data obtained for the pattern block shown in FIG.
FIG. 20 shows a fourth modification of the test pattern.
FIG. 21 shows added density data obtained for the pattern block shown in FIG.
FIG. 22 shows a fifth modification of the test pattern.
FIG. 23 shows a sixth modification of the test pattern.
FIG. 24 shows a seventh modification of the test pattern.
FIG. 25 shows an eighth modification of the test pattern.
FIG. 26 shows a ninth modification of the test pattern.
FIG. 27 shows a tenth modification of the test pattern recorded by the modification of the recording method.
28 shows the test pattern shown in FIG. 27 and a CCD unit having no inclination with respect to the sub-scanning axis.
29 shows a first band data reading unit and a second band data reading unit obtained by virtually dividing the CCD unit shown in FIG. 28. FIG.
30 shows density data of a pair of reference patterns read by a CCD unit having no inclination with respect to the sub-scanning axis. FIG.
FIG. 31 shows the reference pattern shown in FIG. 27 and a CCD unit having an inclination with respect to the sub-scanning axis.
FIG. 32 shows how the CCD unit shown in FIG. 31 reads a reference pattern.
FIG. 33 shows density data of a pair of reference patterns read by a CCD unit having an inclination with respect to the sub-scanning axis.
FIG. 34 shows binarized density data of a pair of test patterns for which the recording position deviation amount is to be obtained.
35 shows a logical product (AND) of a pair of binarized density data shown in FIG.
FIG. 36 is a graph showing a relationship between a shift amount of a pair of binarized density data shown in FIG. 34 and an integral value of their logical products;
FIG. 37 shows a logical sum (OR) of a pair of binarized density data shown in FIG.
38 is a graph showing a relationship between a shift amount of a pair of binarized density data shown in FIG. 34 and an integrated value of their logical sums.
FIG. 39 shows added density data of a pair of test patterns for which the recording position deviation amount is to be obtained.
40 shows a comparative minimum value group of a pair of multi-value density data shown in FIG. 39. FIG.
41 is a graph showing the relationship between the shift amount of the pair of multi-value density data shown in FIG. 39 and the integral value of the comparison minimum value group.
42 shows a comparative maximum value group of the pair of multi-value density data shown in FIG. 39. FIG.
43 is a graph showing the relationship between the shift amount of the pair of multi-value density data shown in FIG. 39 and the integral value of the comparison maximum value group. FIG.
44 shows an absolute value of a difference between a pair of multi-value density data shown in FIG. 39.
45 is a graph showing the relationship between the shift amount of the pair of multi-value density data shown in FIG. 39 and the integral value of the absolute value of the difference between them. FIG.
46 shows a product of a pair of multi-value density data shown in FIG. 39. FIG.
47 is a graph showing the relationship between the shift amount of the pair of multi-value density data shown in FIG. 39 and the integral value of their products.
FIG. 48 shows a pair of test patterns composed of dot rows recorded on a recording medium in a conventional example.
[Explanation of symbols]
100 Image recording apparatus
110 Carriage
112 Guide
120 Recording unit
130 CCD unit
140 Paper holding mechanism
170 Carriage controller
172 Carriage drive mechanism
174 Recording control unit
176 calculator
192 paper

Claims (5)

Recording means for recording an image on a recording medium;
Scanning means for reciprocating the recording means along the main scanning axis;
Reading means for reading a pair of test patterns recorded on a recording medium by the recording means;
In the image recording apparatus and a calculation means based on the correlation of the density data of the pair of the test pattern read by said reading means, to calculate the relative print position shift amount of the pair of test patterns,
The pair of test patterns is composed of a plurality of pairs of pattern blocks, and the plurality of pairs of pattern blocks are composed of different pattern elements for each pair,
The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and stores a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. image recording apparatus and recording. Recording means for recording an image on a recording medium;
Scanning means for reciprocating the recording means along the main scanning axis;
Reading means for reading a pair of test patterns recorded on a recording medium by the recording means;
An image recording apparatus comprising: a calculation unit that calculates a relative recording position shift amount of the pair of test patterns based on a correlation of density data of the pair of test patterns read by the reading unit.
The pair of test patterns is composed of a plurality of pairs of pattern blocks, and at least a part of the plurality of pairs of pattern blocks is composed of a plurality of pattern elements,
The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and stores a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. An image recording apparatus for recording. Recording means for recording an image on a recording medium;
Scanning means for reciprocating the recording means along the main scanning axis;
Reading means for reading a pair of test patterns recorded on a recording medium by the recording means;
An image recording apparatus comprising: a calculation unit that calculates a relative recording position shift amount of the pair of test patterns based on a correlation of density data of the pair of test patterns read by the reading unit.
The pair of test patterns is composed of a plurality of pairs of pattern blocks, and the plurality of pairs of pattern blocks are arranged at different intervals along the main scanning axis,
The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and stores a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. An image recording apparatus for recording. Recording means for recording an image on a recording medium;
Scanning means for reciprocating the recording means along the main scanning axis;
Reading means for reading a pair of test patterns recorded on a recording medium by the recording means;
An image recording apparatus comprising: a calculation unit that calculates a relative recording position shift amount of the pair of test patterns based on a correlation of density data of the pair of test patterns read by the reading unit.
The pair of test patterns is composed of a plurality of pairs of pattern blocks, and at least a part of the pair of pattern elements is composed of a plurality of portions having different densities. And
The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and stores a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. An image recording apparatus for recording. Recording means for recording an image on a recording medium;
Scanning means for reciprocating the recording means along the main scanning axis;
Reading means for reading a pair of test patterns recorded on a recording medium by the recording means;
An image recording apparatus comprising: a calculation unit that calculates a relative recording position shift amount of the pair of test patterns based on a correlation of density data of the pair of test patterns read by the reading unit.
The pair of test patterns is composed of a plurality of pairs of pattern blocks, and at least a part of the plurality of pairs of pattern blocks is arranged with at least a part of another pair of pattern blocks in between,
The recording unit records a pattern block included in one of the plurality of pairs of pattern blocks during the forward movement by the scanning unit, and stores a pattern block included in the other of the plurality of pairs of pattern blocks during the backward movement. An image recording apparatus for recording.

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