JPH07309020A - Image recording apparatus - Google Patents

Abstract

PURPOSE:To always form a stable image by providing a means independently controlling the density characteristics of a plurality of multinozzle heads corresponding to the detection results of a plurality of temp. detection means. CONSTITUTION:The respective color signals 16a, 16b, 16c of yellow, magenta and cyan inputted from a reading part or an image data memory part are inputted to a color processing part 17 and color correction processing such as masking or the like is performed. Next, the corrected color signals are inputted to gamma-correction ROMs 18A, 18B, 18C. The gamma-correction ROMs 18A, 18B, 18C set the respective color signals after color correction to address data and the gamma-correction of the inputted signals is performed by the ROM in which the values calculated by multiplying the respective address data by a gamma-coefficient are stored. Several kinds of gamma-coefficients are stored in this gamma-correction ROM and the optimum gamma-coefficient can be selected by the selection signal from the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus provided with a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to a plurality of recording colors. is there.

[0002]

2. Description of the Related Art Conventionally, an ink jet recording apparatus for forming an image by ejecting ink from a nozzle having a minute diameter is well known. The inkjet recording apparatus is widely used as a color image recording apparatus because it is easy to obtain a color image by superposing and printing inks of a plurality of colors.

FIG. 4 shows three colors of yellow, magenta and cyan.
It shows a method of scanning an inkjet head when a color image is obtained by overlapping color inks.

In the figure, 1A, 1B, and 1C are arranged by a multi-nozzle head while maintaining a distance d, and while ejecting ink from the orifice 2, the recording paper 3 is scanned at a speed υ in the direction of arrow 4. The head 1A is for yellow ink, 1B is for magenta ink, and 1C is for cyan ink, and printing is performed on the recording paper 3 in the order of yellow, magenta, and cyan.

FIG. 5 is a block diagram of image signal processing of such an ink jet recording apparatus.

Input signals 5a to 5c indicating the image densities of the three colors of yellow, magenta and cyan are input to the processing section 6 and subjected to color processing such as masking processing and then to the gradation correction section 7. , Γ correction is performed. After the correction, the yellow signal of the three color signals is sent to the recording head 9A as it is, but the magenta signal and the cyan signal are respectively buffered.
After being stored in 8A and 8B once, the time corresponding to the interval d in the scanning direction of the recording head, that is, the magenta signal is d /
The υ and cyan signals are delayed by 2d / υ and sent to the heads 9B and 9C.

As a result, the yellow, magenta, and cyan color inks are printed at the same location on the recording paper 3, and a color image is reproduced.

In such an ink jet recording apparatus,
The head generates heat when driven, and the temperature of the head rises when printing is continued. Generally, the viscosity of ink decreases as the temperature rises, but the ejection amount of ink from the head increases as the viscosity decreases.

The amount of ink bleeding on the recording paper is also
The lower the viscosity of the ink, the larger the ink. Therefore, the dot area on the recording paper increases due to the temperature rise of the head, and the image density increases.

FIG. 6 illustrates this situation, and shows that the γ characteristic changes as the head temperature changes.

As described above, the image density and the γ characteristic are changed by the temperature rise of the head. Further, as shown in FIG. 4, in an apparatus that forms a color image by ejecting inks of different colors from a plurality of heads, the temperature rise of each head is not uniform, and the temperature rise of each head varies depending on the document. Comes out. For example, the temperature of the cyan head is particularly high in an image with a blue sky as a background, and the temperature of the cyan head is particularly low with an image with a sunset as a background. In such a case, a difference occurs in the γ characteristic of each color, so that there is a drawback that the color balance changes before and after the temperature rise, and stable color reproduction cannot be performed.

Particularly, in a multi-nozzle head having a plurality of nozzles, the temperature change is large for each head, and the change in the density characteristic due to the temperature cannot be ignored.

[0013]

SUMMARY OF THE INVENTION The present invention eliminates the above-mentioned drawbacks of the conventional example and provides an image recording apparatus capable of always obtaining a stable image even if there is a difference in temperature of multi-nozzle heads of a plurality of colors. The purpose is to provide.

[0014]

In order to achieve such an object, the image recording apparatus of the present invention comprises a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to a plurality of recording colors. In the image recording apparatus, a plurality of temperature detecting means are provided corresponding to each of the multi-nozzle heads, and detect a temperature of each of the multi-nozzle heads; And a control means for independently controlling the density characteristics of each of the multi-nozzle heads.

[0015]

According to the present invention, in an image recording apparatus having a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to each of a plurality of recording colors, the temperature of each multi-nozzle head is detected and the detection is performed. By independently controlling the density characteristics of each of the plurality of multi-nozzle heads according to the result, it is possible to always form a stable image.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a block diagram of an image processing unit in an embodiment of the image recording apparatus of the present invention, and FIG. 2 shows a schematic view of the embodiment of the present invention.

In FIG. 2, a yellow head 10A, a magenta head 10B, and a cyan head 10C are supplied with ink by ink supply tubes 11A, 11B, and 11C, respectively, and are printed on the recording paper 12 while being scanned in the direction of the arrow. And a color image is formed. Temperature detecting elements 13A, 13B, 13C such as thermistors are attached to each head, and the temperature signals 14a to 14c of each head are input to the image processing unit 15.

FIG. 1 is a block diagram of the image processing unit of this embodiment.

Yellow, magenta, and cyan color signals 16 input from an unillustrated reading unit or image data storage unit
The signals a, 16b, 16c are input to the color processing unit 17, are subjected to color correction processing such as masking, and then are input to the γ correction ROMs 18A, 18B, 18C. The γ-correction ROMs 18A, 18B, and 18C are ROMs in which each color signal after color correction is used as address data, and a value obtained by multiplying each address by a γ coefficient is stored. By this, the γ-correction of an input signal is performed. Several kinds of γ coefficients are prepared in this γ correction ROM, and the optimum γ coefficient can be selected by a selection signal from the outside.

The temperature signals 14a, 14b, 14c from the temperature detecting elements 10A, 10B, 10C of each head are respectively A / D converters.
After being converted into digital signals by 19A, 19B and 19C, they are input to the γ correction ROMs 18A to 18C as γ coefficient selection signals 20a to 20c. At this time, the temperature signal of each color head is input to the corresponding γ correction ROM for each color.

The γ correction ROMs 18A to 18C select an optimum γ coefficient in accordance with the temperature signal, output a value obtained by multiplying this by an input image signal, and print an ink by a head (not shown) to form an image. Do. The γ coefficient is changed to be small when the head temperature is high and large when the head temperature is low.

For example, when the γ characteristic changes with temperature as shown in FIG. 6, the γ correction is performed with temperature as shown in FIG. 3, that is, when the head temperature is low, the straight line a indicates that the temperature is high. By changing the time with the straight line c, the γ characteristic is kept constant.

In the present invention, since this is further performed for each head, even if the temperature rise of the head differs for each color,
This can be corrected, and stable γ characteristics and color reproducibility can always be maintained.

In the above-described embodiment, the recording head has three colors of yellow, magenta and cyan, but the present invention can be similarly applied to recording with four colors including black.

Further, it is not always necessary to detect the temperature for all the heads, and for yellow, for example, where the hue change of the image is less noticeable even if the γ characteristic changes due to temperature change. Alternatively, the temperature may not be detected.

The point is that the temperature of a plurality of heads is detected and the γ correction of the corresponding color is changed according to the temperature.

[0027]

As described above, according to the present invention,
An image recording apparatus having a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to each of a plurality of recording colors, and a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to each of a plurality of recording colors. In the image recording apparatus, a stable image is always formed by detecting the temperature of each of the multi-nozzle heads and independently controlling the density characteristics of each of the multi-nozzle heads according to the detection result. It is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an image processing unit according to the present invention.

FIG. 2 is a schematic view of the vicinity of a head according to an embodiment of the present invention.

FIG. 3 is a diagram showing γ correction according to an embodiment of the present invention.

FIG. 4 is a schematic view showing the arrangement of a recording head and a scanning method of a conventional example.

FIG. 5 is a block diagram of image processing of a conventional example.

FIG. 6 is a γ characteristic diagram when the head temperature is changed.

[Explanation of symbols]

 1A, 1B, 1C, 9A, 9B, 9C, 10A, 10B, 10C Head 6,7 Color processing section 7 γ correction section 13A, 13B, 13C Temperature detection element 18A, 18B, 18C γ correction ROM

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B41J 2/175 2/12 3/54 B41J 3/04 101 Z 102 Z 104 F

Claims (1)

[Claims] 1. An image recording apparatus comprising a plurality of multi-nozzle heads each having a plurality of nozzles corresponding to each of a plurality of recording colors, wherein each multi-nozzle head is provided corresponding to each of the multi-nozzle heads. A plurality of temperature detecting means for detecting the temperature of the head, and a control means for independently controlling the density characteristics of each of the plurality of multi-nozzle heads according to the detection results of the plurality of temperature detecting means. Characteristic image recording device.