JP3069413B2 - 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 a recording apparatus, and more particularly, to an image reading unit provided with an image reading unit for correcting unevenness in density of a printed image caused by non-uniform printing characteristics of a plurality of printing elements based on the read result. To a recording device.

[0002]

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

In a copying apparatus that performs recording using a recording head in which a plurality of recording elements are arranged, for example, when recording is performed by an ink-jet method, depending on the manufacturing accuracy of the recording head, the use conditions of the recording head, and the like. 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 to the recording paper uniform between each ejection port, and these conditions depend on the passage of time and environmental fluctuations. Change. When the printing characteristics among a plurality of printing elements vary as described above, these variations may cause density unevenness on a printed image. For this reason, in the above-described copying apparatus, various proposals have been made with respect to reading a pattern on which predetermined recording has been performed by a reading unit for reading a document, and correcting the recording characteristics of each recording element based on the read result. It has been done. Further, even in a general recording apparatus having no original reading unit, for example, a reading unit for reading a predetermined recording pattern is particularly provided, and based on the reading, a density caused by non-uniform recording characteristics of each recording element. A device for preventing the occurrence of unevenness has also been proposed.

[0004]

In a printing apparatus that performs printing using a plurality of printing elements, there is a configuration in which print data of each printing element is affected by print data of another printing element. . For example, in an error diffusion method among various methods for expressing a halftone of a recorded image by binarized display, a value obtained by adding an error-weighted value based on a pixel value around each pixel to a value of each pixel is added. The threshold value processing is performed on the correction value.

As described above, in a print data configuration in which the print data of each pixel is added to the print data of each pixel in advance, even when the above-described density unevenness correction is performed, By taking into account the printing characteristics of the printing elements around the printing element for the correction, more accurate density unevenness correction can be performed.

SUMMARY OF THE INVENTION 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 on a recorded image recorded by a plurality of recording elements to improve recording quality. It is an object of the present invention to provide a recording device capable of causing the recording device to perform the recording.

[0007]

According to the present invention, there is provided:
The multi-valued recording data corresponding to each pixel is binarized by binarizing means for binarizing the multi-valued recording data of the pixel of interest in consideration of the multi-valued recording data of the peripheral pixels of the pixel of interest. In a printing apparatus that performs printing using a printing head having a plurality of printing elements arranged for printing pixels on a printing medium based on data, a test pattern is formed by the plurality of printing elements of the printing head. Pattern forming means, and correction for correcting the multi-valued data in order to equalize the density at the time of image recording by the recording head based on the result of reading the density of the test pattern corresponding to the plurality of recording elements. Data, correction value calculating means for creating corresponding to each of the plurality of recording elements,
Correction value calculating means for creating correction data corresponding to a predetermined printing element based on a density corresponding to the predetermined printing element and a density corresponding to a printing element other than the predetermined printing element. It is characterized by having.

[0008]

According to the above arrangement, in a recording apparatus in which the multi-level recording data of each pixel is binarized, recording data of pixels surrounding the pixel of interest is taken into account. When performing density unevenness correction for the arrayed print heads,
Since the correction is performed in consideration of the density which is the printing characteristic of the printing element other than the printing element related to the correction, this correction is appropriate in consideration of the print data of the peripheral pixels in the binarization. Will be reflected in

[0009]

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

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

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 an R (red), G (green), and B (blue) filter. It is composed of three elements. A reading unit 203 provided with a lamp 204, a lens 205, and a CCD 206 can move on a rail 207 in the left-right direction in the figure, and the rail 207 moves on a rail 208 and a rail 209 extending in a direction perpendicular to the drawing from the front to the back. Can be moved to

As a result, the original placed on the original platen glass 201 is read by the reading unit 203 by the rail 207.
256 pixels are read while moving left and right along.
After moving by 256 elements of CD 206, rail 2
By moving right and left along 07, 256 pixels are read, and by repeating this operation sequentially, the entire document is sequentially read. The document pressing plate 202 is for pressing a document against the platen glass 201. In addition,
A drive system for moving the reading unit 203 is omitted in FIG.

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

In the above-described configuration of the reading apparatus 200 and the printer 210, the carriage 220 is moved and the recording paper 211 is conveyed in response to the reading operation by the reading unit 203.
8 is performed. During this time, the recording paper 211 is conveyed by one line each time recording for one line is performed, and an 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, and generates bubbles in the ink by the thermal energy generated by the electrothermal conversion element. This is a method of discharging.

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 discharge tray 222 through the discharge port by the discharge roller 217.

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

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

The pattern generating circuit 3 generates test pattern data used for the density unevenness correction processing. The selector 4 selects one of the input image data from the input correction circuit 2 and the test pattern data from the pattern generation circuit 3 according to the recording mode of the printer 210 specified by the CPU 13. The RGB-CMY conversion circuit 5 uses a look-up table to convert the R, G, and B image data transferred via the selector 4 into C, M, and Y data. Each of the C, M, and Y data is subjected to a black extraction operation in a black extraction circuit 6, and then a masking process is performed in a masking circuit 7 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 subjected to these processes based on correction data obtained by a calculation described later. The binarization circuit 9 includes Y, M,
The multi-valued image data of each of C is quantized into binary data by an error diffusion method which takes in the image data of surrounding pixels by weighting. In the recording head 218, the 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 (8 bits for each pixel) weighted by the smoothing circuit 11 is stored in the image memory 12.

Reference numeral 13 denotes a CPU for calculating the correction data according to the present embodiment and controlling the entire copying apparatus of the present embodiment. CP
U13 executes the above-described control according to the processing procedure stored in the program ROM 14, and uses the RAM 15 as a work area in this execution. Reference numeral 16 denotes a RAM for storing 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 shut off or the like.

When the density unevenness is corrected in the configuration shown in FIG. 2, first, the pattern generating circuit 3 generates a 50% (tone intermediate value) uniform pattern which 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 (no unnecessary processing is performed during this time), and is input to the binarization circuit 9. The binarization circuit 9 converts the binary signal by an error diffusion method.
It performs binarization and outputs binary data. Based on the binary data, as shown in FIG.
A test pattern 300 consisting of lines is recorded.

Here, it is considered that the three lines are recorded because, when the recording head is driven at the time of recording, a temperature change occurs in the recording head, so that the influence of the temperature change on the test pattern image is reduced. This is to reduce the influence of unevenness in the feeding of the recording paper and unevenness in the 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 sequentially scanning the reading unit 203 as shown in FIG.
The read image data is weighted by the smoothing circuit 11 and then stored in the image memory 12. At this time, the R (red) signal is used to perform density unevenness correction on the cyan ink recording head, the B (blue) signal is used for the yellow ink recording head, and the G (green) signal is used for the magenta and black ink recording heads.
(Green) signals are stored. Calculation of unevenness correction data (the details of the calculation will be described later) is performed based on the weighted data, and the calculated correction data is stored in the backup RAM 16.

In normal image copying, the correction circuit 8
Corrects an image signal for each ejection port of each recording head 218 based on the correction data stored in the backup RAM 16, thereby eliminating unevenness in density due to variation between each ejection port in a recorded image, and producing 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 binarization methods for image information, image data processing using a binarization method for binarizing information of a target pixel in consideration of information of peripheral pixels, such as an error diffusion method. In this case, the correction of the signal value of the target pixel when performing the density unevenness correction adversely affects the peripheral pixel information.

That is, when a uniform signal S (i) is given to a certain ejection port i in the main scanning direction of the recording head, the number of dots to be formed in the main scanning area for N pixels is represented by d.
(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 surroundings, and d (i) = f (..., s (i-1), s
(I), S (i + 1),...).

[0028]

(Equation 1)

## EQU2 ## Taking the inverse transformation of this expression,

[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, ie, d
When it is desired to set (i) to a desired value in which the weighting by the error diffusion method or the like appropriately reflects the correction, these values d
The linear combination obtained by multiplying (k) by the weight b _ik 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 the present embodiment, this is performed on read image data as described above.

Hereinafter, the calculation of the correction value in the density unevenness correction processing will be specifically described.

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

[0034]

(Equation 3)

Next, g (i, j) is averaged with respect to i and converted into h (j).

[0036]

(Equation 4)

By performing averaging for i, which corresponds to the main scanning direction of printing, density data h (j) accurately reflecting the characteristics of each ejection port can be obtained.

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

[0039]

(Equation 5)

The arrangement range of the ejection ports arranged in the recording head is specified based on the center value Jcenter. That is, both ends of this range are Jstart = Jc
enter-128, Jend = Jcenter + 1
27. Thereafter, density data is specified corresponding to each ejection port of the recording head. That is,

[0041]

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

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

FIG. 6 is a block diagram showing a configuration for image data processing according to the second embodiment of the present invention.
Is similar to the configuration shown in FIG.

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

[0045]

(Equation 7)

There are characteristics such that a _ik ,
b _ik is not an integer. For this reason, by increasing the number of steps only when weighting the correction value, fine unevenness can be changed for each ejection port.

In the above-described two embodiments, the processing of the read image data of the copying apparatus has been described. However, the image data to be corrected is not limited to this, and any image data used for recording may be used. Such data may be, for example, image data from a host device. Therefore, the application of the present invention is not limited to a printer of a copying apparatus, and the present invention can be applied to a wide range of general printers. Also, the recording head used in the printer is not limited to the ink jet method,
For example, a thermal transfer type thermal head may be used.

(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-angle liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat.
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, and an aperture for absorbing a pressure wave of thermal energy is provided. 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 with the apparatus main body or ink from the apparatus main body by being attached to 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.

Further, it is preferable to add ejection recovery means for the recording head, 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.

Regarding the type and number of recording heads to be mounted, for example, in addition to the recording head provided with only one corresponding to a single color ink, the recording head corresponds to 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 system 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.

In addition, the form of the ink jet recording apparatus of the present invention is not limited to 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 take a form.

[0057]

As is apparent from the above description, according to the present invention, when binarizing multi-valued recording data for each pixel, the recording data of pixels surrounding the pixel of interest is taken into account. When performing density unevenness correction of a print head in which a plurality of print elements are arranged in a printing apparatus, the correction is performed in consideration of the density which is a print characteristic of print elements other than the print elements related to the correction. Is appropriately reflected in consideration of the recording data of the peripheral pixels at the time of the binarization.

As a result, accurate density unevenness correction can be easily performed in a shorter time, and a high-quality image can be obtained.

[Brief description of the 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 the correspondence between density data and printheads.

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 unevenness correction data RAM 200 original reading device 206 Photoelectric conversion element (CCD) 210 Printer 218 Recording head

Claims (3)

(57) [Claims] 1. Multi-value recording data corresponding to each pixel is stored in a note
The multi-level recording data of the pixel of interest is converted to the multi-level data
Binarization is performed by binarizing means that takes record data into account.
Value on the recording medium based on the binary data.
To a recording in which a plurality of recording elements are
In a printing apparatus that performs printing using a head, a test pattern is formed by a plurality of printing elements of the printing head.
Pattern forming means for forming a test pattern, and a density of the test pattern corresponding to the plurality of recording elements.
The recording head based on the result
The multi-valued data in order to equalize the density during image recording
Correction data for correcting the
Correction value calculation means created in correspondence with
The creation of the correction data corresponding to the recording element
Density corresponding to the element and recording other than the predetermined recording element
Correction value calculating means for performing based on the density corresponding to the element
Recording apparatus being characterized in that comprises the a. 2. The test path recorded on a recording medium.
Further comprising reading means for reading the density of the turn,
The correction value calculating means may be read by the reading means.
The recording apparatus according to claim 1 , wherein the correction data is created based on the density obtained by the correction . 3. The recording head has an ejection port for ejecting ink, and the recording element generates heat energy.
3. The recording apparatus according to claim 1 , wherein the element discharges the ink from the discharge port based on generation of bubbles generated in the ink by the thermal energy. 4.