JPH0428573A - Image recorder - Google Patents

Abstract

PURPOSE:To prevent occurrence of concentration irregularity having stripes with constant intervals by selecting consecutive specific M record elements to be used for image recording from among a plurality of record elements dependent on image signals with a serial scanning unit. CONSTITUTION:A record head 9 comprises 512 record elements arranged in parallel. Among those 512 record elements, the number of record elements to be used for image recording at each scanning of the record head 9 is 256, which are firstly inputted to a half-tone detector 10 to determine whether a half-tone is present or not. A determining area is within a square having a side with a length by a width to be recorded when 3/4 of the usable record elements 256 of the record head 9 perform the image recording. The determination is performed by detecting whether or not all of image signals corresponding to the determining area in unit record image corresponding to unit image signal are included between 50-205.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image recording device, and particularly to an image recording device that records images by serially scanning a recording head in which a plurality of recording elements are arranged side by side in a predetermined direction. Regarding.

[Background Art] With the spread of computers and communication equipment, image recording apparatuses that record digital images using recording heads such as inkjet type and thermal transfer type are rapidly becoming popular. In an image recording apparatus using a recording head, a recording head in which a plurality of recording elements are arranged side by side is generally used in order to improve the recording speed.

For example, in an inkjet recording head,
A multi-nozzle inkjet head with a plurality of nozzles arranged side by side is common, and a thermal transfer head with a plurality of heaters arranged side by side is also common.

[Problem to be solved by the invention] However, it is difficult to uniformly manufacture a plurality of recording elements, and the characteristics of each recording element vary to some extent. For example, in a multi-nozzle inkjet head, the number of nozzles There are variations in the shape, etc., and in thermal transfer thermal heads, there are variations in the heater shape, resistance value, etc. These non-uniform characteristics between recording elements are caused by the size and density of the dots recorded by each recording element. This results in uneven density in the recorded image.

In particular, in serial scan type image recording devices, the image quality is significantly degraded due to density unevenness inherent in the recording head caused by non-uniform characteristics of each recording element, or because the serial scan is repeated sequentially. There was a problem that the

In addition, this striped density unevenness at regular intervals is particularly noticeable in the halftone portion, and the density unevenness in this portion has been a factor in significantly deteriorating the image quality.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and provides an image recording apparatus in which density unevenness inherent in the recording head caused by non-uniform characteristics of recording elements is not repeated during serial scanning. The purpose is to

[Means for Solving the Problems] In order to solve the above problems, the image recording device of the present invention has the following features:
determining means for successively determining N (M<N) printing elements of the printhead to be used for image recording from among N (N>1) printing elements in accordance with the image signal in a serial scanning unit; The present invention is characterized by comprising a supply means for supplying a corresponding image signal to the print element of the print head determined by the determination means.

[Operation] According to the above configuration, since N consecutive recording elements used for image recording are determined from N recording elements according to one image value number in serial scanning units, the unique Density unevenness is not repeated with serial scanning, and the occurrence of striped density unevenness at regular intervals, which is visually very noticeable, can be prevented.

[Example] Hereinafter, an example in which the image recording apparatus of the present invention is applied to an inkjet recording apparatus will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a control system of a first embodiment of the present invention, and FIG. 2 is a schematic perspective view of an inkjet recording apparatus in which the control system shown in FIG. 1 is installed. First, FIG. 2 will be explained. do.

In FIG. 2, the recording material 5 wound into a roll is sandwiched by the feeding roller 3 via the conveying rollers 1 and 2, and as the sub-scanning motor 15 coupled to the feeding roller 3 is driven,
sent in the direction.

A guide rail 6.degree. 7 is placed in parallel across the recording material 5, and a radar 9 scans from side to side toward an inkjet type recording mounted on a carriage 8.

The recording head 9 is a disposable type that can be attached to and detached from the carriage 8, and includes an ink tank (not shown) built therein. This ink tank is filled with ink, and the ink is sequentially supplied to the ink ejection nozzle side as the ink is ejected.

The recording head 9 uses the so-called bubble jet type of recording, which uses thermal energy to cause state changes in ink such as film boiling, and uses generated bubbles to eject ink from an ejection port toward a recording material. It is the head.

This recording head 9 has heating resistors (
The size of the heater) is much smaller than the piezoelectric elements used in conventional inkjet recording devices, and it is possible to have multiple ejection ports at a high density, resulting in high-quality recorded images, high speed, It has features such as low noise.

The recording material 5 is intermittently fed by the sub-scanning motor 15 so that the recorded images are continuous.

When the recording material 5 is stopped, the recording head 9 scans in the P direction by a main scanning motor (not shown) and discharges ink droplets according to the supplied image signal. In this way, a desired recorded image is formed over the entire surface of the recording material 5 due to the relative movement between the recording head 9 and the recording material 5.

Next, a control system for controlling the inkjet recording apparatus shown in FIG. 2 will be explained with reference to the block diagram shown in FIG. 1.

In FIG. 1, the recording head 9 has 512 recording elements (
In the case of this embodiment, 512 ink ejection nozzles) are arranged in parallel. Of these 512 recording elements, the number of recording elements used for image recording during each scan of the recording head 9 is 256.

A signal corresponding to a unit recording image recorded when the recording head 9 is scanned once in the main scan using these 256 recording elements is called a unit image signal. The signal is input to the tone detection section 10, and it is determined whether or not there is an 8-ft tone part. This determination is made as a percentage of the number of usable recording elements of the recording head 9 (256
In this case, 192 pieces), the determination area is within a square whose side is the length of the width recorded when the image is recorded,
This is done by detecting whether or not all of the image signals (assumed to be 8-bit signals) corresponding to the determination area in the unit recording image corresponding to the unit image signal are between 50 and 205. In other words, if there is a part that falls between 50 and 205, it is determined that the halftone part is present, and if any of the image signals corresponding to the determined area does not fall between 50 and 205. In this case, the halftone part is determined to be "absent".

If it is determined that the halftone part is "absent", the unit image signal is directly sent to the head driver 13 at the end of the recording head 9, that is, from the upper end t in FIG.
56 recording elements are sent for use in image recording. Then, the recording head 9 records a unit recording image according to the drive signal from the head driver 13. However, before the unit recording image is recorded by the recording head 9, an 8-ftone part "no" signal is sent to the sub-scanning motor driver 14, and the recording is performed by 256 recording elements from the end of the recording head 9. The sub-scanning motor 15 is driven so that the unit recording image is continuous with the unit recording image recorded by the previous scan of the recording head 9 (the first
This does not apply to the second scan of the recording head 9).

On the other hand, if it is determined by the halftone detection unit 10 that there is a halftone part, it is determined that there is a halftone part.
A signal is sent to random number generator 11. Further, the unit image signal is sent to the recording element selection processing section I2. The random number generator 11 receives the halftone part "presence" signal and generates "l" to "256".
A random number is generated and the generated random number is sent to the recording element selection processing unit 12.The recording element selection processing unit 12 selects an image from among the 512 recording elements according to the sent random number. 256 consecutive recording elements used for recording are selected.

To explain in more detail, the end of the recording head 9 (1s2
The recording elements corresponding to the above random number are not used for image recording, counting from the recording element at the top end in the figure, and are "random number + 1".
A unit image signal is sent to the head driver 13 so that 256 recording elements starting from the th recording element are used for image recording. Then, the recording head 9 is driven according to the drive signal from the head driver 13, and a unit recording image is recorded.

Further, the random number generated by the random number generator 11 is transmitted to the recording head 9.
Before the unit recording images are recorded, the image is sent to the sub-scanning motor driver 14, and the sub-scanning motor 15 is driven so that the unit recording images are continuous.

By repeating such processing for one page, one page of images is recorded.

As described above, in this embodiment, when printing a halftone part, by randomly changing the printing elements used for image printing for each scan of the printing head 9,
In the halftone portion, density unevenness inherent to the print head is not repeated during serial scanning. This makes it possible to prevent the occurrence of striped density unevenness at regular intervals that is very noticeable to the human eye in halftone areas, which is the main cause of significant deterioration in image quality.

Also, if there is no halftone part, there is always a certain level of I.
By using F (256 pieces from the top) recording elements for image recording and not performing the above-described random selection process, it is possible to shorten the image recording time.

[Second Example] Next, a second example of the present invention will be described. This embodiment is designed to provide substantially the same effect at a lower cost than the first embodiment.

Normally, when driving a print head that has multiple print elements, the print elements are divided into multiple blocks and a drive IC etc. is provided for each block in order to save drive current, etc., and these ICs etc. are time-divided and driven. Is it common to do so?

Similarly, the print head in this embodiment has 512 print elements divided into 8 blocks of 64 print elements, and each block is time-divisionally driven. The control system of this embodiment is the same as that of the first embodiment, and the block diagram showing its configuration is the same as that shown in FIG. However, the random number generator 11 generates random numbers from 1" to "4".

In the recording element selection processing unit 12, the blocks corresponding to the above random number are not used for image recording, counting from the block at the end of the print head 9, and the blocks corresponding to the 4th block from the "random number + 1"th block are not used for image recording.
A unit image signal is sent to the head driver 13 so that the block (corresponding to 256 recording elements) is used for image recording.
send to The rest is the same as the NSL embodiment.

With such a configuration, the recording element selection process can be simplified and costs can be reduced.

[Third Embodiment] Next, a third embodiment of the present invention will be described with reference to the block diagram of FIG. 3. In this embodiment, the present invention was implemented using four recording heads each having 512 recording elements for cyan (C), magenta (M), yellow (Y), and black (BK). This is applied to an inkjet recording device that performs full-color image recording. Note that in FIG. 3, parts having functions corresponding to those in FIG. 1 are given corresponding symbols.

In this embodiment, the random number generator 31 is
A random number up to 8" is generated. The C recording element selection processing section 32C receives the random number (referred to as X) generated by the random a generator 11.
The M, Y, and BK recording element selection units 32M, 32Y, and 328K have adders 36M and 36Y, respectively.

368 is added to the line X+15. )D32.
X+4817) numerical values are input respectively. Other processing is the same as in the first embodiment.

However, if at least one of the C, M, and YBK unit image signals satisfies the above-mentioned conditions, it is determined that there is a halftone portion.

With the above configuration, the joints between the unit images recorded by one scan of the carriage 8 are shifted for each color, visually preventing the occurrence of seams that are particularly likely to occur in full-color image recording. I can do that. Furthermore, as in Example 1.2, it is possible to prevent the occurrence of density unevenness in the form of stripes at regular intervals that are easily noticeable to the human eye.

Note that although in the above-described embodiment, the printing elements of the print head were determined using random numbers, the present invention is not limited to this. For example, recording elements may be determined periodically.

Further, in the above-described embodiment, the printing elements of the print head were determined for each serial scan, but the determination may be made for each plurality of serial scans.

Furthermore, the present invention is not limited to the inkjet recording method, but can also be applied to, for example, a thermal transfer recording method.

[Effects of the Invention] As explained above, according to the present invention, the density unevenness inherent to the recording head is not repeated in serial scanning according to the image signal. This makes it possible to prevent this occurrence, and improve the quality of recorded images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the image recording apparatus of the present invention, and FIG. 2 is an overview perspective view showing the configuration of the embodiment.
FIG. 3 is a block diagram showing another embodiment of the present invention. 9.39G, :19M, 39Y, 39BK... Recording head 10, 30... Halftone detection section 11...
Random number generators 12.32G, 32M, 328 - Recording element selection processing unit 15.35... Sub-scanning motor

Claims (4)

[Claims] (1) In an image recording device that performs image recording by serially scanning a recording head in which N recording elements (N>1) are arranged side by side in a predetermined direction, each serial scanning unit is used for image recording according to an image signal. determining means for successively determining M (M<N) recording elements of the recording head from among the N recording elements; and supply means for supplying a corresponding image signal. (2) The image signal to be recorded is
The image recording apparatus according to claim 1, wherein the unit image signal is a unit image signal corresponding to a unit recording image recorded in one scanning period using two recording elements. (3) When there is no halftone part in the unit image signal, the predetermined M number of recording elements to be used for recording the unit image signal is determined from the N recording elements, and If there is a halftone part in the image, the M recording elements to be used for recording the unit image signal are randomly determined from the N recording elements. Recording device. (4) The recording element of the recording head includes an ejection port that ejects ink, and a device provided at the ejection port that causes a state change in the ink due to heat, and causes the ink to be ejected from the ejection port based on the state change. 4. The image recording apparatus according to claim 1, further comprising thermal energy generating means for forming flying droplets.