JPH0592559A - Recording apparatus - Google Patents

Abstract

PURPOSE:To rapidly and accurately correct density irregularity generated corresponding to respective recording elements when recording is performed using a recording head equipped with a plurality of recording elements. CONSTITUTION:The image data read by a source document reader 20-0 corresponding to the respective recording elements of a recording head 218 are obtained as ones considered so that the recording data of the other recording elements are weighted in a smoothing circuit 11. A CPU 13 operates the correction values at every recording elements on the basis of the respective image data. This operation results are stored in an irregularity correction data backup RAM 16 to be used in the correction of the respective image data in a correction circuit 8. A binary-coding circuit 9 weights the corrected image data of the other recording elements on the basis of the image data corrected at every recording elements to use the same to form the drive data of the recording head 218.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly, it has an image reading unit and corrects density unevenness of a recorded image due to nonuniform recording characteristics in a plurality of recording elements based on the reading result. Recording device.

[0002]

2. Description of the Related Art As this type of apparatus, for example, a copying apparatus having a plurality of thermal transfer type or ink jet type recording elements is generally known. In such a copying apparatus, the reading unit includes a photoelectric conversion element such as a CCD,
By scanning this with respect to the document, the image or the like on the document is converted into an electric signal. Recording is performed by driving a plurality of recording elements in the recording head based on the electric signal obtained by this reading, and an original image is reproduced on a recording medium such as recording paper.

In a copying apparatus for recording using a recording head in which a plurality of recording elements are arranged, for example, when recording is carried out by an ink jet method, it depends on the manufacturing accuracy of the recording head and the usage conditions of the recording head. It is difficult to make the ink ejection characteristics such as the size of the ink droplets ejected from each ink ejection port and the ejection angle of the ink on the recording paper uniform among the ejection ports, and these conditions depend on the passage of time and environmental changes. Change. When the recording characteristics among the plurality of recording elements are thus varied, unevenness in density may occur on the printed image due to these variations. Therefore, in the copying apparatus as described above, various proposals have been made for reading a pattern on which a predetermined recording is performed by a reading unit for reading an original and correcting the recording characteristics of individual recording elements based on the reading result. Has been done. Further, even in a general recording apparatus that does not include a document reading unit, a reading unit for reading a predetermined recording pattern is particularly provided, and based on the reading, the density caused by the nonuniformity of the recording characteristics of each recording element is obtained. A device for preventing the occurrence of unevenness has also been proposed.

[0004]

By the way, in a recording apparatus which performs recording by a plurality of recording elements, each of the recording data for each recording element is influenced by the recording data of another recording element. .. For example, in the error diffusion method among various methods for expressing the halftone of a recorded image by binarization, a value obtained by weighting an error based on pixel values around the pixel is added to the value of each pixel. The threshold value processing is performed on this correction value.

As described above, in the recording data structure in which the recording data of each pixel is preliminarily added to the recording data of the surrounding pixels, even when performing the density unevenness correction as described above, If the recording characteristics of the recording elements around the recording element relating to the correction are taken into consideration, more accurate density unevenness correction can be performed.

The present invention has been made based on the above-mentioned viewpoint, and an object of the present invention is to perform more accurate density unevenness correction in a recorded image recorded by a plurality of recording elements to improve recording quality. It is to provide a recording device capable of performing.

[0007]

Therefore, according to the present invention,
In a recording apparatus for recording on a recording medium based on recording information, a recording head having a plurality of recording elements for performing the recording, and recording corresponding to each of the plurality of recording elements of the recording head Driving means for performing the recording by driving the plurality of recording elements based on the recording data in consideration of the recording data of the recording elements other than the recording element, and the driving of the driving means. Read means for reading the information recorded on the recording medium by means of the correction means, and correction value calculation means for calculating a correction value for recording for each of the plurality of recording elements based on the read data read by the reading means. In consideration of the print data of the print elements other than the print element in the calculation, the correction value of the correction value of the print elements other than the print element is considered. Value calculating means, characterized in that comprises a correction means for correcting the recording data in the driving means based on the calculated correction value by the correction value computing means.

[0008]

According to the above configuration, when recording is performed by the recording head having a plurality of recording elements, the recording data of each recording element is used in consideration of the recording data of other recording elements. In the printing apparatus, when the printing by each printing element is corrected, the correction of the other printing element is taken into consideration according to the consideration of the other printing data.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing the internal structure of a copying apparatus according to an embodiment of the present invention. In FIG. 1, an original reading device 200 illuminates an original placed on an original placing glass 201 with an illumination lamp 204, and photoelectrically converts the reflected light by a photoelectric conversion element (CCD) 206 via a lens 205. Obtain the read image signal.

In the CCD 206 of this embodiment, 256 elements are arranged in a direction perpendicular to the drawing, and each of these elements is provided with R (red), G (green) and B (blue) filters. It is composed of three elements. The reading unit 203 provided with the lamp 204, the lens 205, and the CCD 206 can move in the horizontal direction on the rail 207, and the rail 207 extends on the rail 208 and the rail 209 extending in the direction perpendicular to the drawing from the front to the back. You can move to.

As a result, when the document placed on the document table glass 201 is read by the reading unit 203 on the rail 207.
256 pixels are read while moving to the left and right along with, and then the unit 203 moves along the rail 208 to C.
After moving 256 elements of CD206, similarly move to rail 2
By moving left and right along 07, 256 pixels are read, and by sequentially repeating this operation, the entire original is sequentially read. The original pressing plate 202 is for pressing the original on the original table glass 201. In addition,
A drive system for moving the reading unit 203 is omitted in FIG.

The image data subjected to various image processings is sent to the printer 210. In the printer 210, A1
The roll-shaped recording paper 211 having a size width is the roller 2
The sheet is conveyed onto the platen 216 by 12, 214 and 215, and further conveyed above the printer by the paper discharge roller 217. The recording head 218, which has 256 ink ejection ports arranged as recording elements in the conveyance direction (sub-scanning direction) of the recording paper 211, selectively ejects ink from the 256 ejection ports according to image data. The recording head 218 is C (cyan), M from the front to the back in the direction perpendicular to the drawing.
Four (magenta), Y (yellow), and K (black) inks are respectively provided, and these inks are mounted on the carriage 220 together with the ink tank 219. The carriage 220 can move along a pair of rails 221 extending in a direction perpendicular to the drawing.

In the configuration of the reading device 200 and the printer 210 shown above, the carriage 220 is moved and the recording paper 211 is conveyed in response to the reading operation by the reading unit 203, and the recording head 21 is transferred during this period.
Ink is ejected according to 8. During this time, each time one line of recording is performed, the recording paper 211 is conveyed by one line and the image is reproduced on the recording paper 211. The recording head of the present example includes an electrothermal conversion element corresponding to each ejection port, bubbles are generated in the ink by the thermal energy generated by the electrothermal conversion element, and the ink is generated based on the generation of the bubbles. It is of a discharge type.

The cutter 213 is for cutting the recording paper 211 to a required length. That is, the recording paper 211 on which a predetermined amount of recording has been performed is cut by the cutter 213, and is discharged onto the paper discharge tray 222 by the paper discharge roller 217 through the paper discharge port.

FIG. 2 is a block diagram showing a configuration for image data processing in the image copying apparatus shown in FIG.

In FIG. 2, the read image data of the original read by the original reading device 200 is sequentially sent to the input correction circuit 2. Here, the read image data for each pixel is quantized into digital data, and shading correction for correcting the sensitivity unevenness of the CCD sensor 206 and the illuminance unevenness due to the illumination light source is performed by digital calculation processing.

The pattern generation circuit 3 generates test pattern data used for the density unevenness correction processing. The selector 4 selects either the input image data from the input correction circuit 2 or the test pattern data from the pattern generation circuit 3 according to the recording mode of the printer 210 designated by the CPU 13. The RGB-CMY conversion circuit 5 uses a look-up table to convert the R, G, B image data transferred via the selector 4 into C, M, Y data. The C, M, and Y data are subjected to black extraction calculation by the black extraction circuit 6, and then the masking circuit 7 performs masking processing corresponding to the coloring characteristics of the recording ink. The correction circuit 8 performs a correction process on each of the C, M, and Y data that has been subjected to each of these processes based on the correction data obtained by the calculation described below. The binarization circuit 9 uses Y, M,
The multi-valued image data of each C is quantized into binary data by an error diffusion method in which image data of surrounding pixels are weighted and adopted. In the recording head 218, ink ejection from each ejection port is turned on / off based on the binary data sent from the binarization circuit 9.

The smoothing circuit 11 weights the read image data. The read image data (each pixel 8 bits) weighted by the smoothing circuit 11 is stored in the image memory 12.

Reference numeral 13 denotes a CPU for calculating correction data according to this embodiment and for controlling the entire copying apparatus according to this embodiment. CP
The U13 executes the above control in accordance with the processing procedure stored in the program ROM 14, and uses the RAM 15 as a work area when executing this control. Reference numeral 16 denotes a RAM for storing the unevenness correction data calculated using the weighted image data stored in the image memory 12, and is backed up so that the stored contents are not lost even when the power is cut off.

When density unevenness correction is performed in the configuration shown in FIG. 2, the pattern generating circuit 3 first generates a 50% (gradation intermediate value) uniform pattern that is a test pattern for detecting image density unevenness. .. This pattern is input as an image signal by the selector 4, passes through each processing circuit (while unnecessary processing is not performed), and is input to the binarization circuit 9. The binarization circuit 9 uses 2 by the error diffusion method.
It digitizes and outputs binary data. Based on this binary data, as shown in FIG.
The test pattern 300 consisting of lines is recorded.

The three-line recording here is considered to cause a temperature change in the recording head when the recording head is driven during recording, so as to reduce the influence of the temperature change on the test pattern image, and This is to reduce the influence of uneven feeding of recording paper and unevenness of connection between lines on the test pattern image.

When the recording of the test pattern is completed, the recording paper discharged from the printer 210 is placed on the original placing glass 201.
The test pattern image 300 is read by placing it on top and scanning the reading unit 203 sequentially as shown in FIG.
The read image data that has been read is weighted by the smoothing circuit 11 and then stored in the image memory 12. At this time, an R (red) signal is used to correct the density unevenness of the cyan ink recording head, a B (blue) signal is used to record the yellow ink recording head, and a G (magenta and black ink) recording head is used.
Memorize each (green) signal. The uneven correction data is calculated based on the weighting data (details of the calculation will be described later), and the calculated correction data is stored in the backup RAM 16.

The correction circuit 8 is used during normal image copying.
Corrects the image signal for each ejection port of each recording head 218 based on the correction data stored in the backup RAM 16, thereby eliminating the density unevenness due to the variation between the ejection ports in the recorded image, and forming a high-quality image. Obtainable.

The weighting of the correction value, which is a feature of the present invention, will be described below.

Among the image information binarizing methods, image data processing using a binarizing method, such as the error diffusion method, which binarizes the information of the target pixel by adding the information of the peripheral pixels. Then, the correction of the signal value of the pixel of interest when performing the density unevenness correction adversely affects the peripheral pixel information.

That is, when a uniform signal S (i) is applied to a certain ejection port i in the main scanning direction of the recording head, the number of dots to be printed in the main scanning area of N pixels is d.
Assuming that (i), the number of dots d (i) is ideally d
(I) = (N / 255) s (i). However, when a binarization method such as an error diffusion method is used, d (i) is affected by the surroundings, and d (i) = f (..., s (i-1), s
(I), S (i + 1), ...), which is actually a linear combination of signals,

[0028]

[Equation 1]

It is represented by Taking the inverse transformation of this equation,

[0030]

[Equation 2]

It can be written as follows. That is, when it is desired to change the density recorded by the ejection port i to a desired value by correction in order to correct the density unevenness, that is, d
When it is desired to set (i) to a desired value in which the weighting by the error diffusion method or the like is appropriately reflected in the correction, these values d
The linear combination of the values obtained by multiplying (k) by the weighting _bik may be used as the signal correction value s (i). This weighting may be performed after the correction value calculation or may be performed on the initial image data. In this embodiment, the read image data is processed as described above.

The calculation of the correction value in the density unevenness correction processing will be specifically described below.

The read image data stored in the image memory 12 is composed of 256 × 1024 pixel data f (i, j), and this pixel data has a value of 0 to 255 in 8 bits. The stored pixel data has already been weighted by the smoothing circuit 11 according to the above-described principle, and the pixel data f (i, j) is represented in the form of s (i) in the above equation (2). I have been told. Pixel data f (i,
Since j) is the luminance data, first the density data g (i,
j). The conversion is performed by the table created by the following equation.

[0034]

[Equation 3]

Next, g (i, j) is added and averaged for i and converted into h (j).

[0036]

[Equation 4]

The density data h (j) accurately reflecting the characteristics of each ejection port can be obtained by performing the averaging for i corresponding to the main scanning direction of printing.

Next, h (j) is sliced at a plurality of levels as shown in FIG. 5, and the central value of the image data is obtained from the values of h (j) at the respective slice levels.

[0039]

[Equation 5]

The array range of the ejection ports arrayed in the print head is specified on the basis of the center value Jcenter. That is, at both ends of this range, Jstart = Jc
enter-128, Jend = Jcenter + 1
It is represented by 27. After that, the density data is specified for each ejection port of the print head. That is,

[0041]

## EQU6 ## q (k) = h (Jstart + k) (6) (k = 0 to 255) The density correction value r (k) is obtained from the data q (k) corresponding to each of these ejection ports. That is, r (k) = 100− {100 × q (k) / T} + p (k) That is, the increase / decrease in the density with respect to the predetermined value T is expressed as a percentage, and the correction is increased / decreased by that ratio. Where p (k)
Can be correction data when the correction was performed last time, or predetermined uniform data.

In the first embodiment described above, the calculation of the correction value is performed after weighting the read image data, but the weighting may be performed after performing the calculation.

FIG. 6 is a block diagram showing the arrangement for image data processing according to the second embodiment of the present invention.
The configuration is the same as that shown in FIG.

In this example, the read image data is directly stored in the image memory 612, a correction value calculation based on the image data is performed, a weighting calculation is performed, and the result is stored in the unevenness correction data RAM 616. In addition, the correction circuit 6
A circuit 608 for converting from 8 bits to 12 bits can be added in the preceding stage of 09 to perform more accurate correction. That is, the weighting coefficients a _ik and b _ik are

[0045]

[Equation 7]

There is a characteristic such that, in general, a _ik ,
b _ik is not an integer. Therefore, by increasing the number of steps only when weighting the correction value, it is possible to make a fine variation in unevenness in units of one ejection port.

In the above-described two embodiments, the processing of the read image data of the copying apparatus has been described, but the image data to be corrected is not limited to this, and any image data used for recording can be used. It may be present, and such data may be image data from the host device, for example. Therefore, the present invention is not limited to the printer of the copying apparatus, but the present invention can be widely applied to general printers. Further, the recording head used in the printer is not limited to the inkjet method,
For example, a thermal transfer type thermal head may be used.

(Others) In particular, the present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, particularly in the ink jet recording system. The present invention provides excellent effects in a recording head and a recording apparatus of the type in which the thermal energy causes a change in ink state. This is because such a system can achieve high density recording and high definition recording.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the 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 nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal as a result
This is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection openings to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned respective specifications. U.S. Pat. No. 4,558,333, U.S. Pat. No. 44, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The configuration using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in Japanese Patent Laid-Open No. 59-138461. That is, according to the present invention, recording can be surely 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 which can be recorded by the recording apparatus. 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 recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the electrical connection to the main body of the apparatus or the ink from the main body of the apparatus by being attached to the main body of the apparatus. 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 integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add the ejection recovery means of the recording head, the auxiliary auxiliary means, etc. because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping means, a cleaning means, a pressure or suction means for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be either integrally formed of the recording heads or a combination of a plurality of them. The present invention is also very effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to adjust the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. At times, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in a standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP 54-56847 A or JP 60-7.
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the 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.

In addition, as the form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function It may be in a form or the like.

[0057]

As is apparent from the above description, when recording is performed by the recording head having a plurality of recording elements, the recording data of each recording element takes the recording data of other recording elements into consideration. In a recording device that uses recorded data,
When the recording by each recording element is corrected, the correction of the other recording element is taken into consideration in the correction in accordance with the consideration of the other recording data.

As a result, it is possible to easily perform accurate density unevenness correction in a shorter time and obtain a high-quality image.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an entire copying apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration for image data processing in the device.

FIG. 3 is a schematic diagram showing a recorded test pattern.

FIG. 4 is a schematic diagram showing reading of a recorded test pattern.

FIG. 5 is an explanatory diagram for explaining correspondence between density data and recording heads.

FIG. 6 is a block diagram showing an image data processing configuration according to a second embodiment of the present invention.

[Explanation of symbols]

 3,603 pattern generation circuit 8,608 correction circuit 9,610 binarization circuit 11 smoothing circuit 12,612 image memory 13,613 CPU 14,614 RAM 15,615 ROM 16,616 uneven correction data RAM 200 original reading device 206 Photoelectric conversion element (CCD) 210 Printer 218 Recording head

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 1/23 102 B 9186-5C

Claims (4)

[Claims] 1. A recording apparatus for recording on a recording medium based on recording information, comprising: a recording head having a plurality of recording elements for performing the recording; and a plurality of recording elements of the recording head. Driving data for individually performing recording by driving the plurality of recording elements based on the recording data in consideration of the recording data of the recording elements other than the recording element, A reading unit for reading information recorded on a recording medium by driving the driving unit, and a correction for calculating a correction value for recording in each of the plurality of recording elements based on the read data read by the reading unit A value calculation means, which determines a correction value of a recording element other than the recording element in consideration of recording data of the recording element other than the recording element in the calculation. And consider the correction value calculating means for calculation, the recording apparatus being characterized in that comprises a correction means for correcting the recording data in the driving means based on the calculated correction value by the correction value computing means. 2. The recording apparatus according to claim 1, wherein in the correction value calculation means, the correction values of recording elements other than the recording element are considered by weighted averaging. 3. The recording apparatus according to claim 2, wherein the weighted average area and the weighted value are determined according to a binarization method of the recording data. 4. The recording element has an ejection port for ejecting ink, and ejects the ink from the ejection port based on generation of bubbles generated in the ink by thermal energy. The recording apparatus according to any one of 1 to 3.