JP3205573B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, when an image is recorded by an ink jet head having a large number of ink discharge ports, unevenness in density occurs due to variations in ink discharge amount between discharge ports inherent in the head, and image unevenness. There was a problem of degrading the quality. In order to deal with such a problem, data on density unevenness of each head is measured at the time of manufacturing the ink jet head, and correction data for correcting the image data to be recorded is written to the ROM according to the driving conditions of the head and image processing. And the method of mounting it on products was adopted. However, this method is inadequate for the density unevenness due to the temporal change of the ink jet head. In practice, the method has been dealt with by periodic replacement of the head or maintenance, correction of the density unevenness correction data, and the like.

[0003]

However, in the above-mentioned conventional example, since periodic maintenance is required, maintenance costs and the time required for correcting the uneven density correction data are increased, and there is a strong demand for improvement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional example, and corrects and records input image information based on image correction information created by reading an image pattern recorded by a recording head. An object of the present invention is to provide an ink jet recording apparatus that can respond to a change in recording magnification.

[0005]

For this purpose, the present invention provides:
In an ink jet recording apparatus for forming an image by scanning an ink jet recording head having a plurality of discharge ports a plurality of times, a plurality of elements for generating energy used for discharging ink from the plurality of discharge ports Between a correction unit that suppresses the occurrence of density unevenness during image formation by correcting at least one image processing condition corresponding to each of A conversion unit that converts the image data into binary image data using a multivalued image corresponding to a joint portion, wherein the correction unit stores a correction table group of the at least one image processing condition; The correction data is accessed to perform the correction at the time of recording, and is used to specify the correction table corresponding to each of the plurality of elements. Means for storing data corresponding to the plurality of elements in the second storage means in accordance with a recording magnification so as to include the elements corresponding to the connecting portion. And characterized in that:

According to the present invention, there is provided an ink jet recording apparatus which forms an image by scanning an ink jet recording head having a plurality of discharge ports a plurality of times, to discharge ink from the plurality of discharge ports. Correction means for suppressing the occurrence of density unevenness at the time of image formation by correcting at least one image processing condition corresponding to each of a plurality of elements generating the energy to be applied; Conversion means for converting into binary image data using a multi-valued image corresponding to a connection portion between a scan and a continuous scan, wherein the correction means comprises a correction table group of the at least one image processing condition A first storage unit for storing the correction data, and the correction table is accessed for performing the correction at the time of recording, and the correction table is stored for each of the plurality of elements. A second storage unit for storing correction data for specifying the cable, and an access area corresponding to the connection portion on the second storage unit in accordance with a recording magnification. And means for changing and controlling the correction data.

[0007]

According to the present invention, various types of zoom recording can be performed.
Scaling especially when adopting a configuration that performs image processing in band processing
Also for printing, the access range to the second storage means for storing data (HS data) for specifying the correction table of the image processing condition corresponding to the printing element used for suppressing the occurrence of density unevenness is appropriately set. It can be easily handled by selecting or rewriting according to the magnification. Also, for example, even if the ink jet recording head changes over time, resulting in uneven density,
The density unevenness is measured by the device itself, and after a predetermined calculation process, the density correction table is newly corrected for each discharge port, so that it is possible to appropriately suppress the occurrence of the density unevenness, and always maintain high quality image quality. can do.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

<Color Copier (FIG. 1)> FIG. 1 is a diagram showing a cross-sectional shape of a color copier using the ink jet recording apparatus of this embodiment.

The color copying machine includes an image reading and image processing unit (hereinafter, referred to as a reader unit 24) and a printer unit 4.
4. The reader section 24 is composed of R, G, and B
The image is read while scanning the original 2 placed on the original glass 1 by a CCD line sensor 5 having a color filter (see FIG. 2), and the read image is processed by an image processing circuit, and At 4 for cyan (C), magenta (M), yellow (Y), and black (Bk).
Images are recorded on paper or other recording media (hereinafter also referred to as recording paper) by a color inkjet head.

The details of the operation will be described below.

The reader section 24 comprises members or portions 1 to 23, and the printer section 44 comprises members or portions 25 to 43. In this example, the upper left side in FIG. 1 is the front surface facing the operator.

The printer section 44 has an ink jet head (recording head) 32 for performing recording by ink ejection. The recording head 32 has, for example, ejection ports with a pitch of 63.5 microns in a vertical direction (sub-scanning direction described later). 128
They are juxtaposed and have a configuration capable of recording a width of 8.128 mm. Therefore, when recording on the recording paper, the transportation of the recording paper (conveyance in the sub-scanning direction) is temporarily stopped, and in this state, the recording head 32 is moved in a direction perpendicular to the drawing to record the recording paper for a necessary distance of 8.128 width. After that, the recording paper is fed by 8.128 mm and stopped, and the operation of recording the next 8.128 mm width is repeated. This recording direction is called a main scanning direction, and the paper feeding direction is called a sub-scanning direction. In the configuration of the present embodiment, the main scanning direction is a direction orthogonal to FIG. 1, and the sub-scanning direction is the horizontal direction on FIG.

The reader section 24 repeats the operation of reading the document 2 with a width of 8.128 mm in correspondence with the printer section 44, but sets the reading direction to the main scanning direction and the direction to move for the next reading to the sub-scanning direction. Called the scanning direction. In the configuration of this embodiment, the main scanning direction is the left-right direction in FIG. 1, and the sub-scanning is the orthogonal direction in FIG.

The operation of the reader section 24 will be described as follows.

The document 2 on the platen glass 1 is illuminated by the lamp 3 on the main scanning carriage 7 and its image is passed through a lens array 4 to a light receiving element 5 (CCD line sensor).
It is led to. The main scanning carriage 7 is fitted on the main scanning rail 8 on the sub-scanning unit 9 and is slidable. Further, the main scanning carriage 7 is connected to a main scanning belt 17 by an engaging member (not shown), and moves in the left-right direction in FIG. 1 by the rotation of the main scanning motor 16 to perform a main scanning operation.

The sub-scanning unit 9 is fitted on a sub-scanning rail 11 fixed to an optical frame 10 and is slidable. Further, since the sub-scanning unit 9 is connected to the sub-scanning belt 18 by an engaging member (not shown), the sub-scanning unit 9 moves in the orthogonal direction in FIG.

The image signal read by the CCD 5 is transmitted to the sub-scanning unit 9 by the flexible signal cable 13 which can be bent in a loop. One end of the signal cable 13 is held on the holding portion 14 on the main scanning carriage 7, and the other end is fixed to the bottom surface 20 of the sub-scanning unit by the member 21. The sub-scanning signal cable 23 is connected to the electrical unit 26. Here, the signal cable 13 follows the movement of the main scanning carriage 9, and the sub-scanning signal cable 23 follows the movement of the sub-scanning unit 9.

Next, the operation of the printer unit 44 will be described as follows.

The recording paper fed one by one from a recording paper cassette 25 by a paper feed roller 27 driven by a power source (not shown) is moved by a recording head 32 between two pairs of rollers 28, 29 and 30, 31. Be recorded. The recording head 32 is formed integrally with the ink tank 33, and is detachably mounted on the printer main scanning carriage. The printer main scanning carriage 34 is fitted on a printer main scanning rail 35 and is slidable.

Further, since the printer main scanning carriage 34 is connected to the main scanning belt 36 by an engaging member (not shown), the main scanning motor 34 is moved in a direction orthogonal to FIG. Perform the operation.

The printer main scanning carriage 34 has an arm 38 to which a printer signal cable 39 for transmitting a signal to the recording head 32 is fixed. The other end of the printer signal cable 39 is fixed to a printer middle plate 40 by a member 41 and further connected to the electrical unit 26. The printer signal cable 39 is configured to follow the movement of the printer main scanning carriage 34 and not to contact the upper optical frame 10.

The sub-scanning of the printer section 44 is performed by using a pair of rollers 2.
8.29, 30, and 31 are rotated by a power source (not shown), and the recording paper is conveyed by 8.128 mm. Reference numeral 42 denotes a bottom plate of the printer unit 44, reference numeral 45 denotes an exterior plate, reference numeral 46 denotes a pressing plate for pressing a document to the document glass 1, reference numeral 1009 denotes a discharge port, reference numeral 47 denotes a discharge tray, and reference numeral 48 denotes an electrical unit of an operation unit.

FIG. 2 is a diagram showing details of the CCD line sensor 5 of the present embodiment. The line sensor 5 includes 498 light receiving cells in a line, and one pixel is composed of three pixels of R, G, and B, so that 166 pixels can be read substantially. Among them, the effective number of pixels is 144 pixels, and the pixel width based on this number of pixels is approximately 9 mm.

<Structure of Recording Head, etc. (FIGS. 3 to 9)> FIG. 3 is a diagram showing the appearance of an ink jet cartridge in the printer section 44 of the color copying machine of the present embodiment. FIG. 4 is a diagram showing details of the printed board 85 of FIG.

In FIG. 4, reference numeral 851 denotes a printed circuit board;
52 is an aluminum radiator plate, 853 is a heater board comprising a heating element and a diode matrix, and 854 is a storage means for storing density unevenness information in advance, which may be a nonvolatile memory such as an EEPROM or any other suitable form. Reference numeral 855 denotes a contact electrode serving as a joint with the main body. Here, the ejection port groups arranged in a line are not shown.

As described above, the ink jet recording head 3
An EEPROM 854 for storing density unevenness information unique to each recording head is mounted on a printed circuit board 851 including two heating elements and a drive control unit. And this EE
The PROM 854 measures the density unevenness of each head during head production, and corrects the density unevenness data or the density unevenness corresponding to each ejection port or some ejection ports based on the measured data. Data is recorded.

Thus, when the recording head 32 is mounted on the main unit, the main unit reads out information on density unevenness from the recording head 32, and performs predetermined control for improving density unevenness based on this information. . This makes it possible to ensure high quality image quality.

FIGS. 5A and 5B are diagrams showing an example of a circuit configuration of a main part on the printed board 851 of FIG. Here, the circuit configuration inside the heater board 853 is indicated by a dashed-dotted line, and the heater board 853 has an N × M matrix structure of a circuit in which a heating element 857 and a diode 856 for preventing current from flowing around are connected in series. It is configured. That is, these heating elements 857 are driven in a time-division manner for each block as shown in FIG. 6, and the control of the supply amount of the driving energy is performed by changing the pulse width (T) applied to the segment (Seg) side. This is achieved by controlling

FIG. 5B is a diagram showing an example of the EEPROM 854 of FIG. 4, in which density unevenness information relating to the present embodiment is stored. The density unevenness information is output to the main unit by serial communication in response to a request signal (address signal) D1 from the main unit.

Now, in order to facilitate understanding of this embodiment,
First, the basic factors of the occurrence of uneven density will be described.

FIG. 7A is an enlarged view of a recording state with an ideal recording head 32. FIG. Reference numeral 61 denotes an ink discharge port. When recording is performed by the recording head 32, ink spots 60 having a uniform drop diameter (droplet diameter) are arranged on the paper. Although FIG. 5 shows the case of so-called full discharge (all discharge ports are ON), for example, 50%
Even in the case of halftone such as output, density unevenness does not occur.

On the other hand, in the case shown in FIG. 7B, the drop 6 of the second and (n-2) th discharge ports
2, 63 are smaller than the others, and the (n-2) th and (n-1) th are recorded at positions shifted from the ideal landing center. That is, the (n-2) th drop 63 is recorded to the upper right from the center, and the (n-1) th drop 64 is recorded to the lower left from the center.

As a result of this recording, FIG.
The region A shown in FIG. 3B appears as a thin line,
Since region is (n-1) th and (n-2) -th distance between the centers of larger than the average distance l ₀ between the drop and consequently appears as a thin streak than other areas. On the other hand, C
In the region, so that appears as a (n-1) th and n-th order center distance is narrower than the average distance l _0, darker streaks than other regions.

As described above, the density unevenness mainly appears due to the variation of the drop diameter and the deviation from the center position (this is generally called “skew”). A specific example of a method for correcting the variation in the drop diameter, which is one of the factors, will be described.

FIG. 8 is a diagram showing the relationship between the drive energy used to discharge ink to be applied to the heater (heating element) 853 at the discharge port of the recording head 32 and the drop diameter of the ink discharged at that time. is there. As can be seen from the characteristic curve of FIG. 8, the drop diameter shows a tendency to increase with an increase in energy in a certain driving energy range, and thereafter almost falls off. However,
It can be seen that there is a large difference between the values of the drop diameter with respect to the drive energy between the case of the discharge port having a large diameter and the case of the discharge port having a small diameter.

[0037] Here, for matching the size of the drop size between different ejection port diameters, referring to FIG. 8, for example in order to control the drop size of the value of the same l ₀ is the small diameter discharge ports It can be seen that the drive energy of the large-diameter discharge port should be set to E ₁ (E ₂ > E ₁ ), while the drive energy of E ₂ is set to E ₂ . In this way, an appropriate driving energy is obtained in accordance with the actual drop diameter of each ejection port, and the value of the driving energy or the identification information corresponding to the value of the driving energy is shown in FIG. By writing the data in the non-volatile memory (EEPROM) 854, it is possible to remove at least the density unevenness caused by the difference in the drop diameter between the respective discharge ports.

When variably controlling the driving energy for each discharge port increases the circuit scale on the main body side, for example, matrix driving as shown in FIG. In the case of the recording head 32, each block is set as a minimum unit (in FIG. 5A, each common terminal COM is used).
1 to COMN), the average value of the drop diameters of these discharge ports is determined, and the driving energy based on the average value is written to the nonvolatile memory 854 in the same manner as described above. Thus, density unevenness control can be performed in block units, and the circuit can be simplified.
The above-described drive energy identification information may be a control pulse width, a drive voltage, a drive current, or the like.

Next, a description will be given of means for coping with the above-mentioned "skew" which is another cause of the density unevenness.

The main cause of this "skew" is that the ejection direction of the ink ejected from the ejection port is basically deflected due to the limit of the processing accuracy of the ejection port. This deflection is corrected normally. It is practically difficult to do. Therefore, as a specific method for solving the density unevenness due to the “skew”, instead of distinguishing the drop diameter and the “skew” described above, the image density in a certain area stored by the recording head is determined. Detect before product shipment. Then, a method is employed in which control data based on the detected value is stored in the nonvolatile memory 854 to control the amount of ink applied to the area.

For example, as shown in FIG. 9A, for 50% halftone recording by an ideal recording head, there is "variation" or "distortion" in the drop diameter as shown in FIG. 9B. The following is a method of realizing the printing with the printhead so that the density unevenness is not noticeable. That is, by making the total dot area in the area within the broken line a shown in FIG. 9B close to the total dot area in the area a in FIG. 9A, the recording having the characteristics as shown in FIG. Also in the recording by the head, the naked eyes can feel the same density as in FIG.

The density unevenness is practically eliminated by performing the same operation for the region b in FIG. 9B. Such density correction control is performed by the reader unit 2 as described below.
4 is realized in the image processing.

FIG. 9B shows a model of the processing result of the density correction control in order to simplify the description, and α and β indicate correction dots. Also, as methods generally known as image binarization processing described below, a dither method, an error diffusion method, an average density method, and the like are known. However, these methods are not the gist of the present invention, and the description thereof will be omitted.

<Configuration of Control System and the Like (FIGS. 10 to 18)> In the density correction processing of the embodiment of the present invention, for example, in the flow of signal processing of the reader unit 24 as shown in FIG. It can be implemented as a process.

In FIG. 10, the image signal read from the CCD sensor 5, which is one of the solid-state image pickup devices, has its sensor sensitivity corrected by a shading correction circuit 91, and the L signal
The OG conversion circuit 92 converts the three primary colors of light R (red), G (green), and B (blue) to the three primary colors C (printed color).
(Cyan), M (magenta), and Y (yellow). Next, the C, M, and Y signals are extracted by using the Bk (black) portion as a common component, or a part of the common component is extracted as a black component, and are subjected to head shading as C, M, Y, and Bk signals The signal is input to the circuit 94. In the head shading circuit, when an image signal read by the CCD is recorded by the printer unit, γ correction (density correction) is performed according to the characteristics of the corresponding nozzle of the head as described later. Supplied. γ
The conversion circuit 95 has a function of several steps for calculating output data with respect to input data, for example, as shown in FIG. 11, and an appropriate relationship is determined according to the density balance of each color and the user's taste of the color. Selected. This curve function is determined according to the characteristics of the ink and the characteristics of the recording paper. Further, the output of the gamma conversion circuit is sent to the binarization processing circuit. In this embodiment, the average concentration dependent method (MD method) is employed. The output of the binarization circuit is sent to the printer unit and recorded by the head. In FIG. 10, the head shading circuit (γ
(Correction circuit) 94 is placed before the γ conversion circuit 95 to perform γ conversion after performing γ correction. However, the reverse may be performed.

Reference numeral 97 in FIG. 10 denotes a density unevenness measuring unit. In this embodiment, an electric configuration block of a portion 100 including a head shading circuit (γ correction circuit) 94 and the density unevenness measuring unit 97 is shown in FIG. It has a configuration.

In FIG. 12, reference numeral 150 denotes a control unit.
In this embodiment, a gate array is used as described later with reference to FIGS. Reference numeral 151 denotes a CPU which sets a register in the control unit 150, writes a gamma correction table number into the RAM 152 via the control unit 150,
The density unevenness data is read out from the memory 152, and an operation described later with reference to FIGS. 37 and 39 is performed based on the read out data. A RAM 152 is internally allocated so that a lower address is used as an area for temporarily storing data of density unevenness, and an upper address is used as a storage area for a density correction table number. Reference numeral 126 denotes a ROM that stores a γ correction table, and as shown in FIG. 13, 64 types of γ correction tables are prepared for each color.
In this embodiment, the ROM 126 has the form of an EPROM.
In the following, “EPROM”, “γ-correction ROM” or
Also referred to as the term "table ROM."

FIG. 14 further shows a portion 100 in FIG.
A portion 97 and 94 surrounded by a dashed line are a density unevenness measuring section 97 and a head shading circuit (γ correction circuit) 94, respectively.

First, in the density unevenness measuring section 97, L
The color signal whose density unevenness is currently being measured is selected from the data converted into the three primary colors by the OG conversion unit 92 and latched by the latch circuit 131. The latched image signal is added by the adder 132, and the addition result is averaged by the averaging circuit 133.
Averaged. The averaged data is stored in the temporary memory 134. Here, the data added by the adder 132 is the density of a plurality of dots recorded by each ejection port, and the sampling number can be selected from several types.

An original is set on an original table so that the arrangement direction of the ejection openings of the basic pattern (for example, 50% halftone) for measuring density unevenness and the arrangement direction of the CCD line sensors 5 are perpendicular to each other. In this case, the resolution of the recording head 32 and the CCD line sensor 5
If the resolutions are the same, the density data of the number of pixels corresponding to the number of light receiving elements of the CCD 5 can be obtained by one sampling of the CCD 5. If the resolution of the CCD 5 is higher than the resolution of the recording head 32,
It is necessary to calculate the density of one pixel recorded from data of a plurality of light receiving elements of CD5.

The average value density data of each discharge port is
5 (CPU 151), and the correction table shown in FIG. 15 is assigned to each ejection port. The correction table number obtained in this way is the correction R in FIG.
Stored in AM136.

In the present embodiment, the memory 134 for temporarily storing the read density unevenness and the γ correction memory 136 are one RA.
It is shared by M152. FIG. 15 shows the state of the internal assignment.

The EPROM 126 stores 64 types of .gamma. Correction curves shown in FIG. 16 in the layout shown in FIG.

Next, a specific example of the γ correction processing will be described.

The gamma correction circuit 94 has a number of correction functions (64 types of # 0 to # 63 in this example) as shown in FIG. For example, the function indicated by # 32 is a straight line having a slope of 45 °, and outputs an input signal as it is as an output signal. On the other hand, in the functions of # 31 and below, the input signal is multiplied by a constant smaller than 1 and output. If this function corresponds to, for example, a high density portion of the recording head 32, the input image data is corrected to a density lower than the actual density. On the other hand, in the functions indicated by # 33 and above, the input image is corrected to be darker than the actual image by multiplying the input data by a coefficient larger than 1. Therefore, in this case, it is effective for a low density portion of the recording head 32.

The correction table is determined by the ink bleed rate determined by the relationship between ink and paper and the binarization method in FIG. 10, for example, the error diffusion method or the density preservation method.
Take a curve like

In general, the rate of increase in density when a dot is formed on a blank sheet is higher than when the dot is formed on a blank sheet. Further, at high duty, the dots are already overlapped with each other, so that the density unevenness becomes less noticeable. Therefore, the correction rate is the highest just near the halftone (80H), and decreases toward both ends. Further, at low duty, there is a sufficient distance between dots, so that correction is not necessary. This is because, when the correction is performed, the difference between the ejection port that performs ejection and the ejection port that does not perform ejection becomes clear and the streak becomes conspicuous.

As described above, in this embodiment, one of the plurality of characteristics shown in FIG. 17 is made to correspond to each of the ejection ports of the recording head 32. That is, the identification number of the correction function as shown in FIG. 17 is recorded in the nonvolatile memory 854 of FIG. By referring to these identification numbers, the image signal is γ-corrected by the γ correction circuit 94 corresponding to each ejection port, and the correction result is sent to the binarization processing circuit 96 via the γ conversion circuit 95. . The binarization circuit 96 has a function of ultimately converting multi-value information (indicated by 8 bits in FIG. 17) of each pixel into a binary value of “1” or “0”, as described above. Binarization is performed using a simple dither method, error diffusion method, average density preservation method, or the like. In this embodiment, the average density storage method is adopted as an example, and an output result as shown in FIG. 7B can be obtained by the printer unit 44 as a binary output of the processing result.

FIG. 18 is a block diagram showing a detailed circuit configuration example of the gamma correction circuit 94 in FIG.

Here, reference numeral 120 denotes a counter, 121 denotes a decoder, and a RAM 122 at a subsequent stage according to the color signals T1 and T2.
To 125 are selected. Reference numerals 122 to 125 denote RAMs (random access memories) which store color conversion data corresponding to each color. However, in the present invention, as shown in FIG.
5) and the density data temporary storage RAM 134 described later were shared. Reference numeral 126 denotes a γ correction ROM (read only memory), which stores the γ correction table data shown in FIG.

The color signals T1 and T2 supplied from the BK generation / UCR circuit 93 are "00", "01", "10",
This is a 2-bit signal in which a combination of “11” is considered,
In order to identify colors of image data, the contents of the two bits correspond to Y, M, C, and Bk, respectively. The counter 120 to which the signal T2 of the lower bit of the 2-bit color signal is input has the output Bk (C
(S-EK), and counts up at the rise of the signal T2. In other words, the counter 120 counts + at the end of the C signal.
1 will be done. Then, since one set of Y, M, C, and Bk means one pixel information, the counter 120 is counted up in pixel units. The output of the counter 120 is connected to the address input terminals of the four RAMs 122 to 125.

In the RAMs 122 to 125, the contents of the nonvolatile memory 854 in each recording head are transferred and written in advance via the CPU 151 (see FIG. 14) which is a central processing unit. The outputs of the decoder 121 are sequentially output from the RAMs 122 to 1 in synchronization with the color signals T1 and T2.
Access is performed by designating 25 addresses. As a result, the contents of the accessed RAM are selectively output and input as the upper address of the γ correction ROM 126.

That is, the output of the counter 120 indicates the ejection port number of the recording head 32 corresponding to the image data at that time. The numbers (the characteristic curve numbers # 0 to # 63 in FIG. 17) are recorded. Accordingly, the γ correction ROM 126 determines the table number by the upper address and generates Bk / UCR by the lower address.
The image data output from the circuit 93 is taken as it is, the input image data is corrected according to one function selected from the γ correction curve in FIG.
Handing over to

<Zoom Recording (FIGS. 19 to 21)>
The operation of the gamma correction circuit at the time of zooming in this example will be described.

FIG. 19 shows the relationship between reading by the scanner and recording by the printer in the reduction mode in this embodiment. The figure shows a case of 50% reduction for the sake of simplicity.

In this case, the information read from the document 2 by the CCD 5 with the 128 sensors is thinned out in half, and the recording is performed by the 64 ejection ports in the printer section. In the present embodiment, as shown in the figure, for the first scan of the CCD, the printer performs recording from the first discharge port of the head 32 to the 64th discharge port (first group) and performs the second scan of the CCD. For the 65th discharge port to the 128th discharge port (second
Group). Hereinafter, the first scan will be performed for the third scan.
The group and the fourth group are recorded as the second group. In other words, in reduced mode,
Recording is performed by alternately using the halves of the head, and therefore, the recording paper is conveyed by the printer unit by 8.128 millimeters even in the case of reduction. However, the printer main scanning carriage 34 scans the same area (ie, 8.128 mm width) of the recording paper twice each.

As can be understood from the above description, in the reduction mode, the used discharge ports are alternately switched. Therefore, when the initial value of the control nozzle counter 120 in FIG. 18 is recorded in the first group, it is set to "0". When recording in the second group, it is set to 64 (actually, the CPU 1 in FIG.
35 does this). Here, as already mentioned,
D5 has 166 sensors. When the image processing is performed by band processing as in the case of the present embodiment shown in FIG. 21, the algorithm of the binarization processing is performed between bands (scan n and scan n). (Between (n + 1)). Therefore, the image processing unit of the scanner unit actually performs processing of 128 + α pixels in each band, and the head shading circuit 94 (FIG. 13) is no exception.

FIG. 20 shows the RAM 152 (FIG. 1) of this embodiment.
4, FIG. 15) shows the data contents of the HS data (density correction table number) storage area. The HS data from the discharge port No. 1 to 128 is written from the address 1800H, and the data from the discharge port No. 1 is written again from the address 1880H. This is because the HS data is written so as to be adapted to the connection processing in the present embodiment as shown on the right side of the figure. Specifically, the connection portion (the portion indicated by the dotted arrow) is the next printer main scanning carriage 34.
Is determined by which discharge port is used for recording.

In this embodiment, as described with reference to FIG.
Since the first group and the second group are used alternately at the time of reduction, H at the same time (including enlargement) and at the time of reduction are obtained.
The configuration of the S table may be the same as shown in FIG. 20, and can be dealt with by changing the access area as shown on the right side of FIG. However, for example, when only 64 ejection ports of the first group are used at the time of reduction, the HS data table in the RAM 152 is also arranged so that the HS data of the first ejection port is written again from the address 1840H as shown in FIG. I just need. Therefore, in this case, the HS data area of the RAM 152 may be selectively rewritten and used as shown in FIG. 20 or 21 according to the magnification. In this case, a memory area for saving the contents shown in FIGS. 20 and 21 may be provided. Further, even if printing is performed by an arbitrary number of continuous ejection ports,
This can be handled by appropriately rewriting the HS data of the AM 152.

In the above-described embodiment, the case where the image reading device and the ink jet recording device are connected as a copying machine and the density correction processing is performed in the image reading device has been described. However, the present invention is not limited to this. The present invention can also be applied to an ink jet recording apparatus of the type that inputs R, G, B signals from a device or the like, or a facsimile apparatus. In this case, the above-described γ correction circuit 94 for correcting uneven density is used for signal processing in the ink jet recording apparatus. Provided in the system.

<Operation Sequence> Next, FIG. 22 shows an example of the external configuration of the apparatus of this embodiment, FIG. 23 shows a schematic control procedure of the apparatus of this embodiment, and FIG. 24 which is an explanatory diagram of step S1 in FIG. An outline of the operation of the present example apparatus will be described with reference to FIGS. 25, 26, 27 (a) and 27 (b) which are the specific procedures of S2, S4, S6 and S7.

In step S1 of FIG. 23, after the power is turned on by the main power switch 1008 of FIG. 22, so-called temperature adjustment for keeping the temperature of the head at 25 ° C. in preparation for printing is started, and thereafter, the recording head mounted on the apparatus 24 (the data in the nonvolatile memory of the recording head stores the identification number (ID) unique to the head and the gamma correction table number for each nozzle) of the printer unit shown in FIG. The ID and the ID are copied to an SRAM (HS data buffer). This process is performed whenever there is a possibility that the user has replaced the head, such as when the power is turned on or immediately after the head replacement door (1010 in FIG. 22) is opened and closed.

In the SRAM of the printer section, R
HS data obtained by the HS processing is stored and backed up by a battery together with the HS data buffer described above. Since the HS data buffer and the RHS data buffer store the respective IDs and γ correction data for each of the four color heads of cyan, magenta, yellow, and black, γ correction data of different heads is not erroneously used. It has become.

Thereafter, in step S2, the HS data is transferred to the γ correction memory. At this time, the following judgment is made in order to use the latest HS data of the mounting head.

That is, as shown in step S8 of FIG. 25, the ID and RH of the cyan head copied when the power is turned on.
The head IDs of the S data buffer are compared, and if they match, it means that the RHS process has been performed in the past and that the result remains in the RAM.
The HS data subjected to the RHS processing is used for recording (step S9). Since the data in the nonvolatile memory of the head is never rewritten, it is guaranteed that the HS data subjected to the RHS processing is always newer than the initial HS data of the recording head. The ID of each head is compared with the head ID of the RHS data buffer.
Since the data in the HS data buffer belongs to another head and cannot be used for the current head, the data in the HS data buffer copied from the head to the γ correction memory is transferred (step S10). . Then, for the other colors (magenta, yellow, and black), the processes of S11, S12, and S13 including the same procedure as S8 to S10 are performed.

After the HS data corresponding to the head has been transferred to the gamma correction memory, the apparatus operation unit (FIG. 22) which is a command to perform the copying operation of step S4 in FIG.
COPY key (reference numeral 1004)
And the like, and input determination processing of a door switch (not shown) provided in the head replacement door is performed (step S3 in FIG. 23).

Next, an outline of the copying operation shown in step S4 of FIG. 23 will be described.

FIG. 26 shows an example of a copying operation procedure.
It is activated in response to the operation of the PY key 1005. First, in step S4-1, it is determined whether the reduction mode is the same size / enlargement mode. If the mode is the reduction mode, the process proceeds to step S4-2, and the access area is switched so that the HS data (table number) corresponding to the group selected in one scan is read as described with reference to FIG. Make a record. Alternatively, as described with reference to FIG. 21, recording is performed after rewriting to the HS data corresponding to the use group (rewriting from the state of FIG. 20 to the state of FIG. 21). On the other hand, in the case of the same magnification / enlargement mode, FIG.
As described in the above, since all the ejection openings are involved in printing in one scan, the printing operation is performed after switching so that the area in this mode is accessed, or after rewriting to the state of FIG. Is executed (step S4-3).

Next, step S6 in FIG. 23 is a process when the door for head replacement is opened, and FIG.
Is performed as shown in FIG. That is, when the door is opened, the above-described door switch is turned off, and after the detection in step S3, the process in step S6 is performed. As shown in FIG. 27A, this stops all the drive motors in the apparatus (step S6-1), turns off the reading system halogen lamp, and shuts off the head drive power (step S6).
-2) is a process with the purpose of ensuring the safety of the user by stopping the current flowing through the head portion that can be touched by the user and the physical movement of the head portion, for example. . After the door open process is performed, input of other keys is prohibited until the door switch is turned on, that is, the door is closed in step S3 in FIG. 100
An error is displayed in step 7) (step S6-3), the user is informed of the door open state, and the apparatus enters a loop state.

On the other hand, when the door is closed, a door shut process of step S7 is performed. This process will be described with reference to FIG. 27B. When it is detected that the door is closed, the temperature of the head is restarted to prepare for printing (step S7-1), and the error display is stopped. The process returns to the normal display (the number of copies, etc.) (step S7-2).

In the apparatus of the present invention, processing of keys other than the keys on the operation unit described above is also performed. However, since the processing is not directly related to the present invention, the description and description thereof are omitted in FIG.

The RHS (Read) in step S5 in FIG.
The “er Head Shading” operation is the most important operation in the present example, and is an operation for correcting density unevenness using an apparatus reading system. This process eliminates the density unevenness caused by the aging of the recording head as described above.
This is a process in which a certain printed pattern is read by a reading system of the apparatus, and the HS data is updated so that density unevenness is corrected from the obtained data.

The outline of the operation of the apparatus of this embodiment has been described above.

<RHS Operation> In the present embodiment, the apparatus itself has a means for correcting unevenness in density caused by a temporal change of the head. That is, when unevenness occurs, an unevenness measurement pattern shown in FIG. This is read by the CCD 5 of the scanner itself to perform unevenness measurement processing.

As shown in FIG. 28, the original is set on the platen in such a manner that the nozzle direction of the basic pattern (for example, 50% halftone) for measuring density unevenness is perpendicular to the arrangement direction of the CCD line sensor 5. And CCD line sensor 5
, The resolution of the recording head 32 and C
If the resolution of the CD line sensor 5 is the same, one C
By sampling the CD5, density data of a number of pixels corresponding to the number of light receiving elements of the CCD5 can be obtained. If the resolution of the CCD 5 is higher than the resolution of the recording head 32, it is necessary to calculate the density of one pixel recorded from the data of the plurality of light receiving elements of the CCD 5.

The average density data of each nozzle is
5, and a correction table as shown in FIG. 17 is assigned to each nozzle. The correction table number obtained in this way is stored in the gamma correction RAM 1 in FIG.
36 and the γ correction data is updated. However, as described above, in this example, RA
M134 and RAM 136 are shared by one RAM 152.

Next, a specific control flow of RHS is shown in FIG.
It is explained along. The processing is broadly divided into printing of an uneven reading pattern, reading of the same pattern by a reading system, and HS data calculation.

When the RHS key (reference numeral 1006 in FIG. 22) on the apparatus operation section is depressed, printing of the unevenness reading pattern is performed first. The head recovery operation shown in step S14 in FIG. 29 and S15 correspond to this. In step S14, a series of operations are performed to remove fixed ink from the recording head, remove air bubbles by sucking ink from the discharge ports, cool the head heater, and the like, and perform pattern reading for unevenness reading in the RHS operation in the best condition. This is strongly desirable as a preparatory operation for closing.

In step S15, the unevenness reading pattern shown in FIG. 28 is printed out. As described above, the print pattern is formed by printing a halftone of 50% density in the vertical direction of FIG. 4 for each color in four blocks, and has a total of 16 blocks. The pattern is printed at a predetermined position on the recording paper. The physical position is set so as to be convenient for error detection when reading a pattern described later. Each block is formed from three lines of printing. The first and third lines discharge only from the lower and upper 16 outlets of the 128 outlets, and the second line from all 128 outlets. By performing the discharge, a halftone print block having a print width of a total of 160 discharge ports is formed. The reason why each block is recorded with a width corresponding to 160 ejection openings is as follows.

As shown in FIG. 30, when a recording head 32 composed of, for example, 128 discharge ports is used, when the pattern recorded by the recording head 32 is read by the CCD sensor 5 or the like, the ground of the recording paper is obtained. The density data An shows a tendency to drop due to the influence of the color (for example, white). Therefore, if each block is recorded only with 128 ejection ports, the reliability of the density data of the end ejection ports may be lost.
Therefore, in this embodiment, printing is performed with 160 outlets, density data above a certain threshold is treated as valid data, the center of the valid data is regarded as the central outlet, and from that point (the number of outlets)
/ 2 (in this case, 64) data corresponding to the first ejection port and the 128th ejection port, respectively.

The reason why the both-end pattern is printed by the 16 ejection ports is that the capacity of the uneven data temporary storage RAM 152 is saved, and in the case of a small body (A4 machine or the like), the repeated pattern shown in FIG. This is to make it possible.

After the printing of the read pattern is completed, as shown in step S16 of FIG.
Wait for press. The user places the output recording paper 2 in FIG.
The pattern is placed downward on the document table 1 and four blocks of the same color are arranged in the main scanning direction of the CCD sensor 5.
Thereafter, when the RHS key 1006 is pressed, the process proceeds to step S17 in FIG.

Steps S17 to S28 are a part for reading unevenness and calculating HS data. In step S17, the shading processing of the CCD sensor 5 is performed using the reference white plate 1002 in FIG. 22, and the unevenness reading pattern is read in step S18. Here, one line indicates one main scan of the CCD sensor that reads four blocks of a certain color at a time. Therefore, by reading one line in step S18, four blocks of the black pattern are stored in the memory. The read data (density data) of each of the four blocks is printed at a predetermined position on the recording paper so as to fit in a certain predetermined area of the memory. The arrangement on the memory and the size of the data are as shown in FIG. Specifically, the read data storage area is from 0000H to 01FFH for one block, and similarly from 0200H to 03FFH, 0400H to 05FFH, 0600H.
To 07FFH, data for one block is stored.

Next, in step S19, an error is detected for the read data stored in the memory. Since the RHS of this example requires an operation in which a user places a recording medium on which a print sample (test pattern) is formed on a reader, it is strongly desirable to consider a user's erroneous operation. Try to be as strict as possible to check if this is done. Further, even if the user's operation is correct, if inappropriate data is read by the reader, if the processing is not stopped, inappropriate calculation may be performed and unevenness may be increased. Therefore, in the RHS of this example, the following error detection (step S
19), and appropriate processing is performed for each.

First, as a possible error that the print sample does not take the correct reading position, there is a case where the user has shifted the print sample with respect to the reading area of the reader. For example, the print sample of FIG. 28 should be originally placed on the document table 1 as shown in FIG. 31A, but if it is shifted in the main scanning direction of the reader as shown in FIG. Data is 1 as shown in (c).
Some of them are not enough or halfway. Also, if there is a deviation in the sub-scanning direction of the reader as shown in FIG. 31D, data of "0" is read, as shown in FIG. Color data is read. Further, if the print sample is placed in an inclined manner as shown in FIG. 31B, the data of the nozzles in the vicinity of the adjacent nozzle come into the area corresponding to each ejection port as shown in FIG. I will. In any of these cases, correct correction cannot be performed.
It should be detected as an error and reject the read data.

In order to do this, in this embodiment, the reader is
When scanning, if a print area above a certain threshold is not at an appropriate position (address), it is regarded as an error. Here, the print area means a place where a value equal to or more than a predetermined absolute value continues for each color. At this time, if a blank sheet is read and data contains 0, the print area is not recognized. Further, as another error detection method, when the width of the print area is larger than a certain threshold, this is detected as being placed diagonally, and this is also regarded as an error in which the print sample does not take a correct reading position (FIG. 32B). ).

The above method prevents the writing of erroneous RHS data due to misplacement of the print sample. Such error detection corresponds to an incorrect placement of a print sample by a user, and not only to a case where the print sample is simply shifted as described above, but also to a case where the print sample is inverted or turned upside down. In this case, the error can be read again by repositioning the print sample and pressing the RHS button again.

However, even if the user places the print sample in the correct position, if the state of the head itself is unstable, the discharge port may suddenly become non-discharged. Should be considered abnormal.
Generally, when only one ejection port is not ejected as shown in FIG. 33 (c), the density of that area does not decrease to the same level as the blank area. Therefore, in the present embodiment, a threshold for non-discharge detection is separately provided, and when data in the print area is lower than this, it is determined that there is non-discharge. At this time, FIG.
If all four of the four print patterns have a non-ejection, this is a complete non-ejection, but if there is no non-ejection outside one area, use the remaining part to calculate. Alternatively, printing may be started again as an RHS error. Also, even if there is a non-ejection in all four areas, if it is possible to cover with the printing of the nozzles on both sides, the calculation processing may be performed as it is, or other colors may be used instead of performing only the color. Only SRA
M may be rewritten. Further, the above-described threshold for the print area may be provided at a slightly higher position without detecting the non-discharge threshold, and the threshold may be detected at the same time. In any case, performing the non-discharge detection is R
Highly desirable for HS.

In this embodiment, the above-described error detection is performed to prevent erroneous data from being written to the SRAM, and the most appropriate data is always stored in the SRAM.

Next, how and how such error processing is performed will be described in detail with reference to FIG. When data for one block of one color is read, the value is first processed in a print position abnormality detection (detection of a shift in the main scanning direction or the sub scanning direction) (step S19-1). The form of the data is usually as shown in FIG. Here, the horizontal axis represents the address of the reader, and the vertical axis represents the density. As described above, the range above a certain density level is set as the print area. Here, it is confirmed whether the address X1 having the density exceeding the threshold for the first time is within a certain allowable range. . If it is assumed that the print start position starts at X from the start of reading by the reader, it is checked whether X1 is within X ± Δx. If the rising condition is not satisfied, it is determined as an error when it is detected, an error is displayed (step S20 in FIG. 29), and the step S20 is performed.
It returns to 16. Upon seeing this, the user replaces the print sample and starts reading again when the RHS button is pressed again.

When the error detection of the printing position abnormality is cleared, the obtained data is processed by the printing width abnormality detection (oblique placement detection) (step S19-2). Since the print pattern has only a fixed width, when the sample is printed using a total of 160 discharge ports as in the present embodiment, the density data is now set at the position of X1 + 160 ± Δx. It must fall below the threshold (X2). If this is not satisfied, it is determined that there is a possibility of the oblique placement as described above, and a display is made in the same manner as the above error (step S21 in FIG. 29), and the process returns to step S16, and the RHS is performed again.
Wait until the button is pressed.

The data for which the above two error detections have been cleared are processed in the non-ejection detection which is the last error detection (step S19-3). Here, the density data in the range from X1 to X2 determined as the print area is taken out one pixel at a time, and it is checked whether the density data is below the threshold for non-ejection. If any one of the places is determined to be non-ejection, an error is made at that point and an error is displayed (step S22 in FIG. 29). However, since this error is an error in the printing stage, when the RHS button is pressed again (step S23 in FIG. 29), the step S1
4 and the RHS starts from the initial state.

Now, the data which has successfully cleared the error detection is input to the arithmetic circuit according to FIG. As shown in this figure, the calculation is a density ratio calculation process (step S2).
4) and one line correction table number calculation processing (step S25). In the density ratio calculation, the ratio between the print density of each ejection port and the average density is calculated. In calculating the one-line correction table number, it is determined which of the 64 types of correction tables prepared in advance should be given to each ejection port having the above-described density ratio. As described above, the output signal changed for each print input signal is written in each table. That is, for a nozzle having a low density, a table may be selected such that the output signal is always converted to a high level with respect to the input signal. Conversely, for a nozzle having a high density, the output signal is always changed What is necessary is just to select a table that appears lower than the input signal.

Here, from the point where the data is actually input in the form as shown in FIG.
Will be sequentially described. First, an average of the rising positions X1 and X2 at both ends is obtained, and a center value of the printing area is obtained.
This is determined to be the center of the ejection port array, that is, between the 64th and 65th ejection ports. Therefore, the data at the position before and after every 64 pixels from the central portion is the density of the first ejection port and the 128th ejection port. As a result, the print density n (i) including the connection portions at both ends is obtained at each ejection port. However, it is very dangerous to use the density data of the area having only the width of one pixel as the density data of the ejection port as it is. This is because, as shown in FIG. 36, it is certain that one pixel in the reading area also includes the density of the dots ejected from the ejection openings on both sides, and that any one of the ejection openings has a right or left position. This is because it is inevitable that it depends. Further, it is desirable to take into account that the density unevenness seen by the human eye is affected by the surrounding situation including the pixel of interest. Therefore, in this embodiment, before determining the density of each discharge port, FIG.
As shown in FIG. 7, the average value of the density data (A _i−1 , A _i , A _{i + 1} ) of three pixels including the pixel and the pixels on both sides is sequentially obtained, and this is calculated as the ejection port density ave (i). And

Further, ave (1) to ave (12)
The average value AVE up to 8) is obtained, and this is set as the average density of all the ejection openings. Next, the ratio with this average density is obtained for all the ejection ports. It should be noted here that the value d (i) to be obtained is the reciprocal of the value for each outlet density. That is, d (i) = AVE / ave
(I). For a low-density image, a correction with a large gradient to increase the density is required, and for a high-density image, a correction with a small gradient to reduce the density is required. For later calculation processing,
It is more convenient to find the reciprocal in this way.
When the 128 density ratios d (i) are obtained, the density ratio calculation ends, and the data is used for calculating a one-line correction table.

Here, first, the density ratio d (i) obtained by reading the unevenness this time and the density ratio D
Multiplication D (i) = d (i) × D (i) with (i) is performed.
When the degree of correction in such an arithmetic processing is increased, all of the past d (i) are included while being multiplied. The density unevenness changes gradually, and it is meaningful to add data up to that time to the arithmetic processing in applying the correction. Next, the table is determined. The determination formula at this time is T (i) = (D (i) −1) × 100 + 32, where T (i) is the table number. As described above, 64 correction tables are prepared, and the inclination is gradually increased / decreased centering on table number # 32.

The relationship between the correction table and the above equation will be described again in detail with reference to FIG. In FIG. 17, the table number # 32 is a straight line having a slope 1 in which the input value and the output value are always equal. This is a table that should be taken by the ejection ports for calculating the average density of the 128 ejection ports. The remaining curve above and below is 50% density equal to the print sample.
At (80H), a table exists at 1% intervals around # 32. Therefore, T obtained by the above equation
(I) means that the signal value conversion consistent with the density ratio is always performed in the input signal of 80H. When 128 T (i) are obtained in this way, the one-line correction table number calculation ends.

When the reading of the unevenness of one line, that is, one color, and the calculation of the HS data (γ correction table number) in which the unevenness has been corrected from the data are completed, the heads of four lines, that is, four colors, in step S26. It is checked whether or not the same processing has been completed. When the HS data for four colors has been calculated, the γ correction memory is updated in the next step S27. The latest HS data (γ correction table number) before the RHS processing is stored in the γ correction memory, and is replaced with the calculated latest HS data.

Subsequently, in step S28, the HS data in the RHS data buffer of the backup memory of the printer unit is replaced with the latest HS data.

The description of the control flow of the RHS process has been completed.

As is clear from the above, in this embodiment, when the head is replaced with a new head, the EEPRO in the head is changed.
The M HS data (γ-correction data) is written into the SRAM 136, and the data in the SRAM 136 is updated in accordance with the above-mentioned operation with respect to the subsequent aging. Therefore, in this embodiment, the latest HS data is stored in the RA in the printer control unit so that the updated data is stored even when the power is turned off.
M (not shown), and this RAM is backed up by a battery.

In the density ratio calculation of step S25 in FIG. 29, as shown in FIG.
Instead of obtaining a moving average of pixels, the following can be performed.

FIG. 38 shows a procedure for explaining the density ratio calculation according to another embodiment.
1 is performed by the adder 132 and the averaging circuit 1 shown in FIG.
33.

In the average value data obtained in step S31, a moving average is calculated between the average value data and the close ejection port in step S32. In this example, as shown in FIG. 39, the weighting is performed on the close ejection ports, and the density average value of the recorded image density is calculated. For example, A in FIG.
To find the density of pixel data corresponding to ₀ ,
The density data (A _{-4 to} A ₄ ) of the eight pixels before and after that are obtained,
As shown in FIG. 39 (b), a weighted average of them is taken. This takes into account that the density unevenness seen by the human eye is affected by the surrounding situation including the pixel of interest. In step S23, the average D of all the discharge ports is obtained from the moving average value D _n (n is the discharge port number) corresponding to each of the discharge ports thus obtained. Next, the process proceeds to step S34, where the reciprocal 1 / α _n ¹ (= D _n / D) of the density ratio with respect to the average value D of each ejection port of the recording head 32 is obtained. The reason for taking the reciprocal here is that the ejection port having a lower density than the average value D,
That is, for the ejection port _where (D _n / D) <1,
The correction curve shown in FIG. 17 having a slope of (D _n / D)> 1 is selected, the input of the γ correction circuit 94 is output by multiplying by D / D _n , and the density is controlled to be higher than the actual output. That's why.

Conversely, for a nozzle having a higher density than the average value D, the density is controlled to be lower than the actual value by D / D _n (<1) and output.

In step S35, the multiplication value α _n of the reciprocal α _n ¹ of the density ratio obtained in the current density unevenness measurement and α _n ⁰ up to the previous time is obtained. That is, when the density unevenness measurement basic pattern is recorded with the correction coefficient α _n ⁰ , the density ratio is now D _n / D (= 1 / α _n ¹ ). As a result, no further correction of α _n ¹ must be made. Means no longer. Therefore, if these operations are repeated twice, three times _,.
Changes as α _n = α _n ⁰ · α _n ¹ · α _n ² · α _n ³ . From the α _n thus obtained, the calculation of the table number, that is, the selection of the correction curve can be performed in the process of step S25 in FIG.

<Configuration of Control Unit 150> As one of the features of this embodiment, as described above, the RAMs 122 to 125 for storing the γ correction table numbers of the γ correction circuit of FIG. 18 and the density unevenness measurement unit of FIG. Block density unevenness data is temporarily shared with the RAM 134. The internal allocation of the RAM 134 is shown in FIG. The unevenness processing circuit 1 shown in FIG.
12 is as shown in FIG. 12, and the control unit 150 was constituted by a gate array as described above.

FIGS. 40 to 43 are block diagrams of the control unit 150, and show that reference numerals C1 to C4 in the respective drawings are connected to the same reference numerals in the other drawings.

There are three operation modes: a CPU mode in which the CPU accesses the SRAM, a copy mode in which the head shading function is performed, and a head shading mode (HS mode) in which unevenness of the head is read.

First, the HS mode will be described. As described above, in order to first measure the current density unevenness, the halftone data is converted from the binarization processing circuit 96 shown in FIG.
4 and the density is sampled by the CCD line sensor 5 shown in FIG.
In order to save the memory area of the RAM 152 (see FIG. 12), modified three-line printing is performed. That is, printing is performed using only the 128 outlets only for the center line, and only 16 outlets are printed for the front and rear lines. By doing this,
The RAM area for storing patterns 1 to 4 can be saved. That is, one pattern can be accommodated within 512 bytes. The relationship between the pattern and the RAM address is shown on the right side of FIG. 28 (see also FIG. 15).

WINDOW 161, ADD shown in FIG.
The calculation result is stored in the SRAM via the ER 162 and the DIVIDER 163, and this part is an average value circuit. That is, in order to calculate the density of the dots hit by a certain ejection port, 128 data (the set number can be changed by changing the set value of the register corresponding to the sampling number in the register group 160 in FIG. 40). ) Is calculated (FIG. 30 has already schematically shown this state). This average value is the VE signal (video en
able) is an average of predetermined sampling data within a period. Here, the VE signal period is one scanning period of the CCD 5. In the WINDOW circuit 161, as shown in FIG. 42, the data input range of the CCD 5 (BVE signal: block
For video enable), a data capture area is specified. The density average value data corresponding to each ejection port determined in this way is temporarily stored in the RAM address shown in FIG. 15, and this address is generated by the selector 167 in FIG. 43 selecting the HS mode. It is checked whether the average value data thus obtained is suitable for performing density unevenness calculation. For example, if a non-ejection portion as shown in FIG. 33C occurs in each color pattern, a measure such as removing the pattern from the calculation target is taken. The CPU calculates the average data thus obtained in accordance with the procedure described in FIG.
Finally, a density correction table number corresponding to each nozzle is obtained. Next, the CPU stores the obtained table number in the SRAM 15
Write to 2. At this time, the CPU switches the control unit to the CPU mode. In this example, as shown in FIG. 15, the density table number was selected in the last area of the SRAM address.

Next, the CPU mode will be described. FIG.
3, in the CPU mode, the selector 167 sets the SR
The lower 10 bits of the AM152 address bus are
Connected to address bus. The upper 3 bits are
Given by register. The data of the SRAM 152
Write and read are the CPU licenses, respectively.
Signal generated from the read signal WRN and the read signal RDN
(S in FIG. 41 WEN 1 and S OEN).

Next, the copy mode will be described. In the copy mode, the address bus of the SRAM 152 is connected to the nozzle corresponding counter 166 by the selector 167.
The count is incremented in synchronization with the read pixel signal of CD5, and the density correction table number storage area in FIG. 15 is accessed. In FIG. 42, 1T and 2T, which are upper addresses, are head color discrimination signals. As a result, the SRAM 152 outputs the density correction table number corresponding to each ejection port, and this output becomes the table ROM 126 (the upper address in FIG. 12).
As shown in FIG. 13, the contents of the table ROM have 64 types of tables for each color. That is, the SRAM 15
The output of 2 specifies the table number. Also, the 8-bit image signal becomes the lower address of the table ROM 126,
This is the data value on the horizontal axis in FIG. As a result, table R
The data is output to the data bus of the OM 126. Table ROM
The output of 126 is sent to the subsequent binarization processing circuit shown in FIG.

SRAM 1 in each mode described above
The configuration of the address bus 52 is summarized in FIG.

In this example, the control unit 150 shown in FIG. 12 was constituted by a gate array. Since the density correction table number in the SRAM 152 needs to be stored even when the power is turned off, the SRAM is backed up by a battery in this example. However, the density correction table number in the EEPROM 854 shown in FIG. It may be newly updated. In this case, the head always has the latest HS data, for example, when several heads are prepared by the same machine, so the head temperature has reached an abnormally high temperature in continuous printing, for example. In such a case, it becomes possible to immediately restart image output without density unevenness by replacing the head.

Further, even when a head is mounted on another apparatus main body, it is possible to realize image output without density unevenness.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, a recording head fixed to the apparatus main body, or an electric connection to the apparatus main body or ink from the apparatus main body by being mounted on the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

It is preferable to add a recording head ejection recovery means, a preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type and number of recording heads to be mounted are not limited to those provided only for one color ink, for example, and for a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

[0135]

As described above, according to the present invention,
Image processing for various zoom recordings, especially band processing
Even for zooming recording when employing a configuration that performs, first stores data (HS data) for specifying a correction table for image processing conditions corresponding to the recording element which is subjected to the suppression of occurrence of density unevenness (2) It is possible to easily cope with the situation by appropriately selecting the access range to the storage means or rewriting according to the magnification. Also, for example, even if the ink jet recording head changes over time, resulting in density unevenness, the apparatus itself measures the density unevenness, and after a predetermined calculation process, newly corrects the density correction table for each discharge port. By doing so, it is possible to appropriately suppress the occurrence of density unevenness, and it is possible to always maintain high quality image quality.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration example of a color copying machine using an ink jet recording apparatus as one embodiment of the ink jet recording apparatus of the present invention.

FIG. 2 is an explanatory diagram for explaining a configuration of a CCD line sensor used in the color copying machine.

FIG. 3 is an external perspective view illustrating an example of an inkjet recording head applicable to the present invention.

FIG. 4 is a perspective view showing a configuration example of the substrate.

FIGS. 5A and 5B are a circuit diagram showing a circuit configuration of a heater board in the recording head of the present example and a circuit diagram of an EEPROM, respectively.

FIG. 6 is a timing chart of drive signals of the circuit of FIG.

FIGS. 7A and 7B are explanatory diagrams showing the relationship between ejection ports of a recording head and recorded dots. FIG. 7A shows an ideal state, and FIG. 7B shows an actual recording dot state. is there.

FIG. 8 is a characteristic diagram illustrating a relationship between driving energy for ink ejection applied to a heating element of a recording head and a drop diameter of ejected ink.

FIGS. 9A and 9B are a diagram showing a 50% halftone printing result by an ideal printing head and a halftone printing result after density correction processing by an actual printing head, respectively. FIG.

FIG. 10 is a block diagram illustrating a configuration of an image processing circuit according to the present embodiment.

11 is a characteristic diagram illustrating a relationship between an input signal and an output signal of the γ conversion circuit in FIG.

12 is a block diagram schematically showing an electrical configuration of a density unevenness control circuit in FIG.

FIG. 13 is an explanatory diagram for describing internal allocation of a head shading table of a ROM in FIG. 12;

FIG. 14 is a functional block diagram illustrating details of a density unevenness measuring unit and a head shading circuit in FIG. 10;

FIG. 15 is an explanatory diagram showing internal allocation of a RAM in FIG. 12;

16 is a characteristic diagram illustrating an example of a relationship between an input signal and an output signal of the γ correction circuit in FIG.

FIG. 17 is a characteristic diagram showing another example of the relationship between the input signal and the output signal.

18 is a block diagram illustrating a circuit configuration example of the gamma correction circuit in FIG.

FIG. 19 is an explanatory diagram for explaining a relationship between reading by a scanner unit and recording by a printer unit in a reduction mode.

20 is an explanatory diagram showing a relationship between details of an HS data storage area in FIG. 15 and a use area at the time of zooming.

FIG. 21 is an explanatory diagram showing a method of storing HS data when only the first to 64th discharge ports are used at the time of zooming.

FIG. 22 is a schematic perspective view illustrating an example of an external configuration of a color copying machine according to an embodiment.

FIG. 23 is a general flowchart schematically showing an overall control procedure of the color copying machine according to the embodiment.

FIG. 24 is an explanatory diagram for describing an HS data storage area.

FIG. 25 is a flowchart illustrating an example of an HS data reading processing procedure in FIG. 23;

FIG. 26 is a flowchart illustrating an example of a copying operation procedure in FIG. 23;

27 (a) and 27 (b) are flowcharts respectively showing an example of a processing procedure at the time of door opening and at the time of door shut in FIG. 23.

FIG. 28 is an explanatory diagram for describing an unevenness measurement pattern and a reading method.

FIG. 29 is a flowchart illustrating an example of a processing procedure during an RHS operation in FIG. 23;

FIG. 30 is an explanatory diagram showing a relationship between a density unevenness measurement pattern and a CCD line sensor.

FIGS. 31A to 31D are explanatory views showing various states in which a recording sheet on which a test pattern is recorded can be placed on a reader.

32 (a) to (d) show FIGS. 31 (a) to (d).
FIG. 9 is an explanatory diagram of a read state of a test pattern corresponding to the placement state of (d) and the content of read density data.

FIGS. 33 (a) to (c) are explanatory diagrams for explaining means for detecting an error from density data read by a reader.

FIG. 34 is a flowchart illustrating an example of an error detection processing procedure in FIG. 29;

FIG. 35 is an explanatory diagram for explaining assignment of density data read by a reader to each ejection port.

FIG. 36 is an explanatory diagram of a dot formation state in a test pattern.

FIG. 37 is an explanatory diagram of moving average calculation for obtaining density data for each ejection port.

FIG. 38 is a flowchart showing another example of the density ratio calculation processing in FIG. 29.

FIG. 39 is an explanatory diagram of moving average calculation in the processing.

40 is a block diagram illustrating a detailed configuration example of a control unit in FIG.

FIG. 41 is also a block diagram.

FIG. 42 is a block diagram of the same.

FIG. 43 is also a block diagram.

FIG. 44 shows an SRAM in each control mode of the control unit.
FIG. 4 is an explanatory diagram of an address selector of FIG.

[Description of Signs] 1 Platen 2 Document 5 CCD run sensor 7 Main scanning carriage 9 Sub scanning unit 24 Reader unit 32 Recording head 34 Printer main scanning carriage 44 Printer unit 85 Print board 91 Shading correction circuit 92 LOG conversion circuit 93 Bk generation / UCR circuit 94 Head shading circuit (γ correction circuit) 95 γ conversion circuit 96 Binarization processing circuit 97 Density unevenness measurement unit 100 Density unevenness control unit 126 EPROM 130 Color signal selection unit 131 Latch circuit 132 Adder 133 Averaging circuit 134 Data Temporary storage unit 135, 151 Operation unit (CPU) 136, 152 RAM 150 Control unit 854 EEPROM

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norifumi Koitabashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yasuhiro Numata 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-2-214667 (JP, A) JP-A-2-136244 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2 / 205 B41J 2/01 B41J 2/21 H04N 1/23 101

Claims (7)

(57) [Claims] 1. An ink jet recording apparatus which forms an image by scanning an ink jet recording head having a plurality of ejection ports a plurality of times , wherein energy used to cause ink ejection from the plurality of ejection ports is used. and suppressing correcting means occurrence of density unevenness in image formation by correcting at least one of the image processing conditions corresponding to each of the plurality of elements to occur, the scan
The multi-valued image corresponding to the scan
Using a multi-valued image corresponding to the connection between the can
A conversion unit for converting the image data into binary image data , wherein the correction unit is a first storage unit that stores a correction table group of the at least one image processing condition, and is accessed to perform the correction during recording. second memory means for storing correction data for identifying the correction table to correspond to each of the plurality of elements, in accordance with the recording magnification, the plurality of element on the second storage means
The access range corresponding to the child
Means for controlling change so as to include the element . 2. An ink jet recording apparatus for forming an image by scanning an ink jet recording head having a plurality of ejection ports a plurality of times , wherein energy used for causing the plurality of ejection ports to eject ink is used. and suppressing correcting means occurrence of density unevenness in image formation by correcting at least one of the image processing conditions corresponding to each of the plurality of elements to occur, the scan
The multi-valued image corresponding to the scan
Using a multi-valued image corresponding to the connection between the can
A conversion unit for converting the image data into binary image data , wherein the correction unit is a first storage unit that stores a correction table group of the at least one image processing condition, and is accessed to perform the correction during recording. A second storage unit for storing correction data for specifying the correction table corresponding to each of the plurality of elements ; and the link unit on the second storage unit according to a recording magnification.
The contents of the access area corresponding to the
Means for controlling change to the correction data of the corresponding element . 3. The ink jet recording apparatus according to claim 1, wherein the correction unit corrects the density of the multi-valued image data . 4. A device for performing a process for determining the contents of said second storage means, said means comprising means for causing said inkjet recording head to form a test pattern, and means for reading said test pattern. The ink jet recording apparatus according to any one of claims 1 to 3, wherein 5. The test pattern is applied to a certain scan.
And more of the plurality of all formed by discharge ink from a portion of the discharge port, it is formed by discharge ink from a portion of said plurality of discharge ports in succession to the scan on both sides of the portion The ink jet recording apparatus according to any one of claims 1 to 4, comprising: 6. The device according to claim 1, wherein the element is provided corresponding to each of the plurality of discharge ports.
6. The ink jet recording apparatus according to any one of claims 1 to 5. 7. The ink-jet recording head according to claim 1, wherein the ink-jet recording head has an electrothermal conversion element used for causing ink to eject the ink by causing film boiling. The inkjet recording apparatus according to any one of the preceding claims.