JP2812476B2 - Ink jet recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus of the type in which energy is applied to a recording liquid to cause a state change, and the recording liquid is discharged by the action force. .

2. Description of the Related Art A conventional gradation recording method for recording an image having a gradation property, that is, a gray-scale image, in an ink jet recording apparatus in which a recording liquid is ejected as droplets and adhered onto a recording medium to perform recording. An area gradation recording method using a dither method, an error diffusion method, or the like is known.

[Problems to be Solved by the Invention] However, in the conventional gradation expression by the area gradation recording method, it is not always difficult to reproduce a natural intermediate gradation, and the resolution is deteriorated. Was. Furthermore, when a halftone dot image is reproduced, moire tends to occur, and the image is significantly deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording apparatus that performs multi-tone expression that enables natural reproduction of intermediate gradations when recording a grayscale image.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides an ejection port for ejecting ink, and communicates with the ejection port to record energy corresponding to an input image signal. A recording head having a liquid ejection unit provided with an ejection energy generating element acting on the liquid is scanned relative to the recording medium, and ink is ejected from the ejection port to record on the recording medium. In an ink jet recording apparatus, a scanning unit for performing a scan for moving the recording head relative to a recording medium, and a method for recording a dot of a first diameter based on density data of an input image signal, By applying a first energy to the ejection energy generating element while performing scanning by a scanning unit, ink is ejected to perform recording, and a second energy having a diameter larger than the first diameter is recorded. In the case of recording a dot having a diameter, while performing scanning by the scanning means, a second energy larger than the first energy is applied to the ejection energy generating element to eject ink to perform recording. In the case of printing a dot having a predetermined third diameter larger than the diameter of 2, the first energy is applied to the discharge energy generating element while discharging the ink while performing the scanning by the scanning means, and the first energy is applied to the first energy. After passing through a first step of recording a dot having a diameter, the ejection energy generating element is subjected to the second step by a scan different from that of the first step.
The second stage of recording is performed by applying the energy of the above to eject the ink and superimposing the dot of the second diameter on the dot of the first diameter recorded in the first stage, thereby forming the dot of the third diameter. The image forming apparatus further comprises a control unit for controlling the driving of the recording head and the scanning unit so as to perform recording.

[Operation] According to the present invention, the energy applied to the ejection energy generating element is gradually increased up to a plurality of types of dots having a diameter smaller than a predetermined diameter in accordance with the gray scale at which the density of the pixel of the input image signal is reproduced. The recording is performed by increasing the size, and for the dot having the predetermined diameter, the large dot is provided so as to at least partially overlap the small dot, and the two are separately provided in different scans. It is possible to realize multi-gradation expression that enables natural reproduction of intermediate gradations.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing a scanning carriage unit of the ink jet recording apparatus according to one embodiment of the present invention.

2, a paper feed motor 40 is a drive source for intermittently feeding the recording paper 38, and includes a paper feed roller 28,
The second paper feed roller 27 is driven via the roller clutch 43.

The scanning motor 35 is a drive source for scanning the scanning carriage 34 in the directions of arrows A and B via the scanning belt 42. In this embodiment, a pulse motor is used for the paper feed motor 40 and the scanning motor 35 because accurate paper feed control is required.

When the recording paper 38 reaches the second paper feed roller 27, the second paper
The roller clutch 43 and the paper feed motor 40 are turned on, and the recording paper is transported on the platen 39 to the paper feed roller 28.

The recording paper is detected by a paper detection sensor 44 provided on the platen 39, and the sensor information is used for position control, jam control, and the like.

When the recording paper 38 reaches the paper feed roller 28, the paper feed second roller clutch 43 and the paper feed motor 40 are turned off, and the platen
A suction operation is performed from the inside of the plate 39 by a suction motor (not shown) to bring the recording paper 38 into close contact with the platen 39.

Prior to the image recording operation on the recording paper 38, the scanning carriage 34 is moved to the position of the home position sensor 41,
Next, forward scanning is performed in the direction of arrow A, and cyan, magenta, yellow, and black inks are ejected from a predetermined position from the recording head 37 to perform image recording. When the image recording for a predetermined length is completed, the scanning carriage 34 is stopped, and conversely, a backward scanning is performed in the direction of arrow B, and cyan and
Magenta, yellow and black ink recording head 37
More ejection image recording is performed. After recording the image for a predetermined length, the scanning carriage 34 is returned to the position of the home position sensor 41. After the backward scanning, the paper is fed by the length recorded by the recording head 37 in the direction of arrow C by driving the paper feed roller 28 by the paper feed motor 40.

Here, the recording head 37 is an ink jet nozzle of a type that forms bubbles by heat and ejects ink droplets at the pressure, and uses four nozzles each having 256 nozzles assembled. .

Next, one embodiment of the present invention is shown in FIG. Here, the scanner unit 1 and the printer unit 3 indicate a scanner unit and a printer unit, for example, in a digital color copying machine in which the ink jet recording apparatus of the present embodiment is used. This is a part corresponding to the recording device.

In FIG. 1, a scanner unit 1 has a charge-coupled device (CCD) 101, an analog signal processing unit 102, and a digital image signal processing unit 103. To enter. Printer unit 3
Has a dither processing circuit 301, a four-level conversion circuit 302, a dither four-level conversion circuit 303, a head driver 304, and a recording head 37. Here, the symbols C, M, Y and BK of the recording head 37
Indicates the colors of cyan, magenta, yellow, and black inks, respectively.

Next, the operation of this embodiment will be described. First, in the scanner section 1, the image information combined on the CCD 101 is converted into an analog electric signal by the CCD 101. The converted image information is serially processed such as red → green → blue and input to the analog signal processing unit 102. The analog signal processing unit 102 performs sample-and-hold, dark level correction, dynamic range control, and other processing for each of the input red, green, and blue colors, and then performs analog processing. The digital image signal is converted into a serial multi-valued digital image signal (8-bit length for each color in this embodiment) and input to the digital image signal processing unit 103. The digital image signal processing unit 103 performs the necessary correction processing on the input serial multi-valued digital image signal in a reading system such as CCD correction or gamma correction in the form of the serial multi-valued digital image signal. Next, after performing image processing such as smoothing processing, edge enhancement, black extraction, and masking processing, serial-parallel conversion is performed, and four-color (cyan, magenta, yellow, and black) multi-valued parallel is converted from the serial multi-valued image signal. An image signal is input to each of the dither processing circuit 301 and the quaternary conversion circuit 302 of the printer unit 3.

As described above, the multi-valued parallel image signals for each of the four colors input from the digital image signal processing unit 103 of the scanner unit 1 to the printer unit 3 are directly converted into the dither processing circuits 301 and Input to each of the conversion circuits 302. In the dither processing circuit 301, four-color multi-values (8-bit values: 256 values) input by a 4 × 4 dither matrix
Is converted into a 4-color binary image signal.

Here, FIG. 3A illustrates a 4 × 4 dither matrix, and FIG. 3B illustrates an 8-bit parallel image signal. FIG. 3 (C) shows the result of processing the parallel image signal of FIG. 3 (B) into a 4-color binary image using the dither matrix of FIG. 3 (A). The values of the image signals shown in each frame of FIGS. 3A and 3B are displayed in hexadecimal. In FIG. 3C, "1" indicates a pixel at which a dot is formed by the printer, and "0" indicates a pixel at which a dot is not formed.

Next, the quaternary circuit 302 converts the input multi-valued (8-bit value: 256-value) parallel image signal into three types of threshold values K ₁ =
_{3FH (63), K 2 =} 7FH (127), and K ₃ = a BFH (191) for processing in parallel the image signal of the 4 values for each color.

FIG. 4 shows a parallel image signal having an 8-bit value for each color illustrated in FIG. 3 (B), and the threshold values K ₁ , K ₂ and K
₃ shows the result of the quaternary processing.

FIG. 3 (C) which has been binarized by the dither processing circuit 301.
And the four-color binary image signal shown in FIG.
The four-color parallel image signal shown in FIG. 4 and quaternized in FIG. 4 is input to the dither quaternization circuit 303.

In the dither quaternizing circuit 303, the dither processing circuit 301 sets "1"
Is processed in accordance with the output of the quaternizing circuit 302. That is, for example, the output of the dither processing circuit 301 shown in FIG.
When the quaternary processing is performed according to the output of the quantifying circuit 302, the result shown in FIG. 5 is obtained.

In the first illustrated head driver 304 according to this example, there are two types of electrothermal transducers (hereinafter, referred to as heaters) that apply thermal energy for ejection to the recording liquid, namely, a heater.
A pulse having an amplitude of 1/2 Vop [V] and Vop [V] can be applied.

FIG. 6 shows the relationship between the amplitude of the pulse applied to the heater and the recording dot diameter of the recording liquid droplet discharged from the head.

In FIG. 6, for example, a pulse 40 having an amplitude of 1/2 Vop
When 1 is applied to the heater for 10 μs, the recording dot diameter becomes 50
μm. FIG. 6 shows the pulse amplitudes 0, 1, and 4 which have been quaternized by the dither quaternization circuit 303.
A few quaternary image signals are shown in association.

Next, an example of image recording performed using the apparatus shown in FIG. 2 will be described. Here, when performing image recording by scanning the scanning carriage 34 in the direction A, the amplitude of the pulse applied to the heater is set to 1/2 Vop [V]. On the other hand, when performing image recording by scanning the scanning carriage 34 in the B direction, the amplitude of the pulse applied to the heater is set to Vop [V].

As shown in FIG. 6, the amplitude of the pulse applied to the heater is 0 at the pixel of the image signal “0”.
The head does not record. 1/2 Vop amplitude for image signal "1"
Since the pulse of [V] corresponds, in the case of the pixel of the image signal "1", printing is performed by applying a pulse of amplitude 1/2 Vop [V] to the heater when scanning the scanning carriage 34 in the A direction. . Since a pulse having an amplitude Vop [V] corresponds to the image signal "2", a pulse having an amplitude Vop [V] is applied to the heater when the scanning carriage 34 is scanned in the B direction when the pixel is an image signal "2". To record. Since the image signal “3” corresponds to a pulse of amplitude (1 + 1/2) Vop [V], when the pixel of the image signal “3” is used, first, when the scanning carriage 34 is caused to scan in the direction A, the heater has an amplitude of 1 After applying a pulse of / 2 Vop [V] and performing printing, when the scanning carriage 34 is caused to scan in the B direction, printing is performed by applying a pulse of amplitude Vop [V] to the heater.

In the above, the image signal is quaternized, and the two signals of 1/2 Vop [V] and Vop [V] are corresponded to the pixels of these image signals.
The embodiment in which a high-gradation image is recorded by applying pulses having different amplitudes to the heater has been described. However, the invention is not limited to the scope of the embodiments described above,
By increasing the number of types of pulse corresponding to the multi-valued image signal by performing four or more multi-value processing on the image signal, it is possible to obtain an image with higher gradation.

Incidentally, as shown in FIG. 7 as another embodiment, since there is a correlation between the amplitude of the pulse applied to the heater and the diameter of the recording dots ejected from the head, the number of image signals of four or more is large. Corresponding to the binarization process, the types of pulse amplitude can be increased.

Further, as another embodiment, the type of the pulse applied to the heater can be increased not only by changing the amplitude of the pulse but also by changing the ON period τ of the energizing pulse applied to the heater even when the amplitude is constant, that is, by changing the pulse width. it can. FIG. 8 shows the relationship between the pulse width applied to the heater and the recording dot diameter d of the recording liquid droplet discharged from the recording head.

Furthermore, the type of pulse applied to the heater is the seventh.
Based on the relationship between the pulse amplitude and the recording dot diameter of the recording liquid droplet shown in the figure, and the relationship between the pulse width and the recording dot diameter of the recording liquid droplet shown in FIG. 8, both the pulse amplitude and the pulse width were changed. More gradations can also be obtained by appropriately combining them. In this way, the number of types of pulses applied to the heater is increased, and as shown in this embodiment, for each pixel of the image signal, a recording dot is printed a plurality of times at the same position corresponding to the pixel on the recording medium. By doing so, it goes without saying that the number of gradations for reproducing the shading of the image signal can be further increased.

In addition, in the above example, an ink jet recording apparatus including a recording head using a heater for applying thermal energy as an element for generating ejection energy for applying energy for ejection to the recording liquid has been described. The element may be an electric / mechanical energy conversion element such as a piezo element.

[Effects of the Invention] As is clear from the above, according to the present invention, a plurality of types of pixels having a diameter smaller than a predetermined diameter corresponding to the gray level to be reproduced are represented by the gray scale representation of the pixels of the input image signal. Recording is performed by gradually increasing the energy applied to the ejection energy generating element up to the dot, and for the dot having the predetermined diameter, a large dot is applied so as to at least partially overlap a small dot, and both are applied. Since the scanning is performed in different scans, dots having a diameter smaller than the predetermined diameter are printed in one scan, so that the printing speed does not decrease. Therefore, a large amount of ink is not applied at a time to perform printing, so that ink bleeding can be reduced, and a multi-gradation expression that enables natural reproduction of intermediate gradations can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory view of a scanning carriage unit according to the embodiment shown in FIG. 1, and FIG. 3 is an image signal processing by a dither processing circuit in FIG. , FIG. 4 is an explanatory diagram of image signal processing in a quaternary circuit, FIG. 5 is an explanatory diagram of image signal processing in a dither quaternary circuit, and FIG. 6 is also applied to a heater. FIG. 7 is an explanatory diagram of the relationship between the pulse amplitude and the recording dot diameter, FIG. 7 is an explanatory diagram of the relationship between the pulse amplitude applied to the heater and the recording dot diameter in another embodiment, and FIG. FIG. 4 is an explanatory diagram of a relationship between a pulse width applied to a heater and a recording dot diameter. 1 scanner unit 3 printer unit 27 paper feed second roller 28 paper feed roller 34 scanning carriage 35 scanning motor 37 recording head 38 recording Paper 39 Platen 40 Paper feed motor 41 Home position sensor 43 Second paper feed roller clutch 44 Paper detection sensor 101 Charge-coupled device (CCD) 102, an analog signal processing unit, 103, a digital image signal processing unit, 301, a dither processing circuit, 302, a quaternary circuit, 303, a dither quaternary circuit, 304, a head driver.

Continuation of the front page (72) Inventor Yukio Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shigemi Kumagai 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kimiyoshi Hayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-57-95470 (JP, A) JP-A-57-95469 (JP, A) JP-A-63-53052 (JP, A) JP-A-63-312155 (JP, A) JP-A-60-49953 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/205 B41J 2/13 B41J 2/21

Claims (2)

(57) [Claims] 1. A recording apparatus comprising: a discharge port for discharging ink; and a liquid discharge section provided with a discharge energy generating element which communicates with the discharge port and applies energy corresponding to an input image signal to a recording liquid. In an ink jet recording apparatus that performs scanning for moving a head relative to a recording medium and performs recording on the recording medium by discharging ink from the discharge ports, the recording head is moved relative to the recording medium. Scanning means for performing scanning to move the first energy to the ejection energy generating element while performing scanning by the scanning means based on density data of an input image signal. The recording is performed by ejecting the ink by applying the voltage, and when the dot having the second diameter larger than the first diameter is recorded, the scanning by the scanning unit is not performed. By applying a second energy larger than the first energy to the ejection energy generating element, ink is ejected to perform recording, and a dot having a predetermined third diameter larger than the second diameter is formed. In the case of recording, after performing a first step of applying the first energy to the discharge energy generating element while performing scanning by the scanning means and discharging ink to record the dot of the first diameter, the first step is performed. The second energy is applied to the ejection energy generating element by a different scan from the first step to eject ink, and the second diameter dot is superimposed on the first diameter dot recorded in the first step. An ink jet apparatus comprising: the scanning unit; and a control unit that controls driving of the recording head so as to perform recording of the third diameter dot by performing two-stage recording. Recording device. 2. An ink jet recording apparatus according to claim 1, wherein said ejection energy generating element is a thermal energy generating element.