JPH0428574A - Image recorder - Google Patents

Abstract

PURPOSE:To prevent conspicuous stripe irregularity of concentration with constant intervals by deciding a record element to be used for image recording dependent on serial scanning. CONSTITUTION:An image signal to be supplied to a record head 9 is being stored in a page memory 10 for 1 page in a sequence as shown by an arrow. A random number generator 11 generates integers '1'-'512' at random. A record element selector section 12 selects a record element with serial numbers in accordance with a random number sent from the random number generator 11 from among 512 record elements. The image signal is sent to a head driver 13 so as to use this record element for image recording. The head driver 13 drives the record element with random number from an end portion from among record elements of the record head 9 so as to perform the image recording. Also, the random number generated at the random number generator 11. is sent also to an auxiliary scanning motor driver 14 and an auxiliary scanning motor 15 is driven dependent on the random number such that images are to be continued.

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.

[Conventional technology]

2. Description of the Related Art With the spread of computers and communication devices, image recording apparatuses that record digital images using inkjet recording heads, thermal transfer recording heads, and the like 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, variations occur in the shape of the nozzle, etc., and in a thermal transfer head, variations occur in the shape, resistance value, etc. of the heater. Non-uniformity in characteristics among these recording elements results in non-uniformity in the size and density of dots recorded by each recording element, resulting in uneven density in the recorded image.

Particularly, in a serial scan type image recording apparatus, density unevenness inherent in the recording head caused by non-uniform characteristics of each recording element is sequentially repeated as a result of serial scanning. Therefore, there is a problem in that striped density unevenness at regular intervals, which is very noticeable to the human eye, occurs in the recorded image, resulting in a significant deterioration of image quality.

In addition, these striped density irregularities at regular intervals are particularly noticeable in halftone parts, and the density irregularities in these parts are a factor in significantly deteriorating image quality.

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

[Means to solve the problem]

In order to solve the above problems, the image recording device of the present invention includes:
A determining means for determining a recording element of a recording head to be used for image recording according to serial scanning, and a supplying means for supplying a corresponding image signal to the recording element of the recording head determined by the determining means. It is characterized by what it did.

[Effect]

According to the above configuration, since the recording element used for image recording is determined according to serial scanning, density unevenness inherent to the recording head is not repeated with serial scanning, which is very noticeable visually. The occurrence of striped density unevenness at regular intervals can be prevented.

〔Example〕

Embodiments in which the image recording apparatus of the present invention is applied to an inkjet recording apparatus will be described in detail below 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 l and 2, and as the sub-scanning motor 15 coupled to the feeding roller 3 is driven, the recording material 5 is moved to f in the figure. sent in the direction. A guide rail 6.7 is placed in parallel across the recording material 5, and an inkjet recording head 9 mounted on a carriage 8 scans left and right.

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 discharge nozzle side in accordance with the discharge of the ink.

This recording head 9 is a so-called bubble jet type recording head that uses thermal energy to cause a state change in the ink such as film boiling, and uses the generated bubbles to eject ink from an ejection port toward a recording material. . In this recording head 9, the size of the heating resistor (heater) provided in each ejection port is much smaller than the piezoelectric element used in conventional inkjet printing devices, and the high density multiplication of ejection ports is possible. It is possible to obtain high-quality recorded images, and has features such as high speed and low noise.

The recording material 5 is intermittently fed by a sub-scanning motor 15 so that recorded images are continuous. When the recording material 5 is stopped, the recording head 9 is operated by a main scanning motor (not shown).
The ink droplets are scanned in the P direction and ejected 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. The image signals supplied to the recording head 9 are stored in the page memory 10 for one page in the order shown by the arrow in FIG.

Note that an image signal is sent to the page memory 10 from a reader or host computer (not shown). Also,
In the figure, H indicates the direction in which the recording elements of the recording head 9 are arranged side by side. Corresponding to the unit recording image I recorded when the recording head 9 is caused to perform one main scan to perform image recording using the maximum usable recording element number (here, 512) of the recording head 9. The signal is called a unit image signal S.

11 is a random number generator, which randomly generates integers from "1" to "512". The recording element selection processing section 12 selects a number of consecutive recording elements according to the random number sent from the random number generator 11 from among the 512 recording elements. Then, an image signal is sent to the head driver 13 so that this recording element is used for image recording. Then, the head driver 13 drives a random number of recording elements of the recording head 9 from the end (the upper end in FIG. 3).
Record images. At this time, the width of the image actually recorded is narrower than that of the unit recording image.

The random numbers generated by the random number generator 11 are also sent to the sub-scanning motor driver 14, and the sub-scanning motor 5 is driven in accordance with the random numbers so that the recorded images are continuous.

Here, details of the recording element selection processing section 12 described above will be explained with reference to FIGS. 4 and 5.

The recording element selection processing unit 12 inputs the image signal stored in the page memory 10 shown in FIG.
As shown in Figure (b), a unit image signal having a width (512 pixels) corresponding to the unit recording image I that is continuous to the previously recorded image signal is generated. Furthermore, the generated unit image signal (
4(b) and FIG. 5(a)) are rearranged as shown in FIG. 5(b) according to the random numbers input from the random number generator 11.

That is, the image signals corresponding to the random number are left as they are, and the other image signals are erased (deleted) and rearranged so that the recording elements are not driven.

In this way, by changing the number of recording elements used for image recording for each scan of the recording head 9, density unevenness inherent to the recording head 9 caused by non-uniform characteristics of the recording elements can be prevented from being repeated with serial scanning. You will no longer have to worry about it. Therefore, striped density unevenness at regular intervals, which is very noticeable to the human eye, does not occur, and the image quality is significantly improved.

[Second Embodiment] Next, a second embodiment of the present invention will be described. This embodiment is designed to provide substantially the same effects as the first embodiment at a lower cost.

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

The print head in this embodiment is similar, and the 512 print elements are 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 "8".

The recording element selection processing unit 12 selects consecutive drive blocks of the number 8 according to the random number supplied from the random number generator 11.
Choose from three driving blocks. Then, an image signal is sent to the head driver 13 so that the recording elements of this drive block are used for image recording. The rest is the same as the first 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. 6. 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. In addition,
In FIG. 6, parts having functions corresponding to those in FIG. 1 are given corresponding symbols.

In this embodiment, the random number generator 61 selects a number of consecutive drive blocks according to the random numbers supplied from 1". At this time, the recording head 61 of each color (C, M, Y, BK)
Driving blocks for each color are selected so that the driving blocks used for recording images of 9C, 69M, 69Y, and 69Bk are shifted one block at a time in the sub-scanning direction. For example, when the generated random number is "5", the drive blocks of each color selected are cyan: 1st block to 5th block, magenta: 2nd block to 6th block, and yellow: 3rd block.
Block to 7th block, black: 4th to 8th block. The subsequent processing is performed in the same manner as in the second embodiment.

By configuring as described above, one of the carriages 8
Since the joints between unit recording images recorded by multiple scans are shifted for each color, it is possible to visually prevent the occurrence of joints that are particularly likely to occur in full-color image recording. Furthermore, the first. Similar to the second embodiment,
It is also possible to prevent the occurrence of striped density irregularities at regular intervals that are easily noticeable to the human eye.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described with reference to the block diagram of FIG. 7. This embodiment prevents the occurrence of striped density unevenness at regular intervals that is very noticeable to the human eye when there is a halftone part, and performs high-speed image recording when there is no halftone part. It is something.

Note that in FIG. 7, parts having functions corresponding to those in FIG. 1 are given corresponding symbols.

In the figure, the unit image signal generation process M72a includes the fourth unit image signal generation process M72a.
As shown in the figure, the image signal stored in the page memory 70 is input and a unit image signal is generated. This unit image signal is supplied to a halftone detection section 77, and it is determined whether or not there is a halftone portion. This determination is made when 3/4 of the maximum usable recording elements (384 in this case) of the recording head 79 are located within a square whose side is the width of the image recorded. It is determined whether or not all of the image signals (assumed to be 8-bit signals) corresponding to the judgment area in the unit recording image corresponding to the unit image signal are between 50 and 205. This is done by detecting. In other words, if there is a part that falls between 50 and 205, it is determined that the halftone part is present, and any of the image signals corresponding to the above judgment area does not fall between 50 and 20δ. In this case, it is determined that the halftone part is "absent".

If it is determined that the halftone portion is "absent", the unit image signal is sent as is to the head driver 73. At this time, image recording is performed using the maximum number of usable recording elements (512 in this case) of the recording head 79 (at this time, the image actually recorded is equal to a unit recording image). In addition, a halftone part "absence" signal is sent to the sub-scanning motor driver 74, and the recording material (paper) 5 is moved by the width that would be recorded if image recording was performed using 512 recording elements. It is driven to be sent as the sub-scanning motor 75 rotates. Furthermore, the halftone detection section 77 sends a halftone portion "absence" signal to the unit image signal generation processing section 72a. Upon receiving this signal, the unit image signal generation processing unit 72a causes the page memory 7
The next unit image signal from among the image signals stored in 0 is sent to the halftone detection section 77.

On the other hand, when it is determined by the halftone detection unit 77 that there is a halftone part, the halftone part "present" is detected.
A signal is sent to random number generator 71. Further, the unit image signal is sent to the unit image signal recombination processing section 72b.

The random number generator 71 receives the halftone part "present" signal, generates random numbers from "1" to "512", and sends the generated random numbers to the unit image signal recombination processing section 72b.

The unit image signal recombination processing section 72b recombines the unit image signals from the halftone detection section 77 according to random numbers as shown in FIG. 5, and sends the recombined image signals to the head driver 73.
supply to. The head driver 73 performs image recording using a random number of recording elements of the recording head 79 starting from the end (upper end in FIG. 3). At this time, the width of the image actually recorded is narrower than the unit recording image.

Further, the random numbers generated by the random number generator 71 are sent to the sub-scanning motor driver 74, and the sub-scanning motor 75 is rotated according to the random numbers so that the images are continuous. Furthermore, the random numbers generated by the random number generator 71 are transmitted to the unit image signal generation processing section 7.
Sent to 2a. In the unit image signal generation processing section 72a,
The image signals stored in the page memory 70 are rearranged according to the sent random numbers to generate the next unit image signal as shown in FIG. 4, and the generated signal is supplied to the halftone detection section 76.

By repeating the above process for one page, 1
Image recording of the page will be performed. Note that the number of image signals sent to the final halftone detection unit 77 of page l is less than or equal to the unit image signal.

As described above, in this embodiment, when recording a halftone portion, by randomly changing the number of recording elements used for image recording for each scan of the recording head 79, the halftone portion is unique to the recording head. Density unevenness will not be 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 a major cause of significant deterioration in image quality.

In addition, when there is no halftone part, image recording is performed using the maximum number of usable recording elements, so the number of recording elements used for image recording is calculated for every scan of the recording head 79. The image recording time can be shortened compared to the case where the values are changed randomly.

[Fifth Example] Next, a fifth example of the present invention will be described. This embodiment is designed to provide substantially the same effects as the fourth embodiment at a lower cost.

The recording head in this embodiment is 512 in FIG.
The recording elements are divided into 8 blocks each having 64 recording elements, and each block is time-divisionally driven.

The block diagram of this embodiment is the same as that shown in FIG. However, the random number generator 71 generates random numbers from "1" to "8" and sends them to the unit image signal recombination processing section 72a.

The unit image signal recombination processing section 72a recombines the unit image signals from the halftone detection section 77 according to the sent random numbers, and sends the recombined image signals to the head driver 73. The head driver 73 performs image recording using a random number of drive blocks from the end (upper end in FIG. 3) of the eight blocks of the recording head 79.

By adopting such a configuration, the unit image signal generation processing section 72b, the unit image signal recombination processing section 72a, etc. are simplified, and it becomes possible to achieve cost reduction.

[Sixth Embodiment] Next, a sixth embodiment of the present invention will be described with reference to the block diagram shown in FIG. 8. In this embodiment, the present invention is applied to an image recording apparatus equipped with a reader that reads an original by serially scanning a reading head. Note that in FIG. 8, parts having functions corresponding to those in FIG. 7 are given corresponding symbols.

In the figure, 90 is a reader, which reads a portion of the document corresponding to the unit image signal by one scan of the reading head. The read unit image signal is sent to a halftone detection processing section 87, as in the fourth embodiment, and the presence or absence of a halftone portion is determined.

If it is determined that there is no halftone portion, the unit image signal is sent as is to the head driver 83, and image recording is performed using the maximum usable number of recording elements. Further, the halftone part "absence" signal is sent not only to the sub-scanning motor driver 84 but also to the reader sub-scanning motor driver 91 to drive the reader sub-scanning motor 92 so that the images are connected.

On the other hand, if it is determined that there is a halftone part, a halftone part "present" signal is sent to the random number generator 81, and a unit image signal is sent to the unit image signal recombination processing section 82b. Similar processing is performed.

However, the random numbers generated by the random number generator 81 are sent to the unit image signal recombination processing section 12b, the sub-scanning motor driver 84, and the reader sub-scanning motor driver 91. The subsequent processing according to the random numbers sent to the unit image signal recombination processing section 82b and the sub-scanning motor driver 84 is the same as in the fourth embodiment.

The reader sub-scanning motor driver 91 causes the next reading head to scan according to a random number, so that the unit recorded image corresponding to the read unit image signal is continuous with the recorded image actually recorded by the previous scanning of the recording head 89. like,
The reader sub-scanning motor 92 is driven.

According to the above configuration, in addition to the same effects as in the fourth embodiment, the memory capacity of the reader 90 is sufficient for a unit image signal, and it is possible to eliminate the need for a page memory.

Note that in the above-described embodiment, the printing elements of the print head were determined using random numbers, but 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 inkjet recording methods (for example, it is also applicable to thermal transfer recording methods).

C. Effects of the Invention] As explained above, according to the present invention, the density unevenness inherent to the recording head is not repeated during serial scanning, so it is possible to prevent the occurrence of striped density unevenness at regular intervals. This makes it possible to improve the quality of recorded images.

[Brief explanation of drawings]

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.
3 to 5 are explanatory diagrams explaining the operation of one embodiment,
FIGS. 6 to 8 are block diagrams showing other embodiments of the present invention. 9, 69C, 69M, 69Y, 698,
79.89...recording head 10, 60. 70...Page memory 11, 61.
71.81...Random number generator 12.62C, 62M,
62Y, "62Bk... Recording element selection processing section 15, 65. 75. 85... Sub-scanning motor 77
, 87... Halftone detection section 72a... Unit image signal generation processing section 72b, 82b... Unit image signal recombination processing section. (a) Unit image signal Figure 5

Claims (6)

[Claims] (1) In an image recording apparatus that performs image recording by serially scanning a recording head in which a plurality of recording elements are arranged side by side in a predetermined direction, the recording elements of the recording head to be used for image recording are adjusted according to the serial scanning. 1. An image recording apparatus comprising: determining means for making a determination; and supply means for supplying a corresponding image signal to the recording element of the recording head determined by the determining means. (2) The image recording apparatus according to claim 1, wherein the determining means randomly determines the recording element of the recording head to be used for image recording for each of the serial scans. (3) The image recording apparatus according to claim 1, wherein the determining means determines the recording element of the recording head to be used for image recording in accordance with the image signal to be recorded. (4) The image signal to be recorded is a unit image signal corresponding to a unit recording image recorded in one scanning period using all recording elements of the recording head. ). (5) If there is no halftone part in the unit image signal, it is decided to use all the recording elements of the recording head to record the unit image signal, and if there is no halftone part in the unit image signal. 5. The image recording apparatus according to claim 4, wherein in some cases, it is randomly determined to use fewer recording elements than all the recording elements of the recording head for recording the unit image signal. (6) The recording element of the recording head includes an ejection port that ejects ink, and is provided at the ejection port to cause 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. 6. The image recording apparatus according to claim 1, further comprising thermal energy generating means for forming flying droplets.