JPH0231562A - Recorder - Google Patents

Abstract

PURPOSE:To reproduce all input pictures with high qualities by making the quantizing method for data for low-density ink different from the method for other data. CONSTITUTION:Density data from a picture input section 1-a are inputted to a look-up table(LUT) 1-b and density data for thin and thick ink are outputted at the timing from a timing clock generation circuit 8. The density data for thin ink are inputted to a relational operator 2 where the data are compared with comparison data from a dot design matrix 3 and further inputted to a delay circuit 7 where the data are quantized by a dither method. The density data for thick ink are inputted to an adder 4 and outputted from the adder 4 after the error outputted from a relational subtractor 5 at the timing of clocks is added to the data and binarization is performed on the output by an error diffusing method. Therefore, gradation and resolution can be compatible with each other and all input pictures can be reproduced with high qualities.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device that records images, and more particularly to a recording device that performs quantization processing on input data and performs recording.

[Conventional technology]

Traditionally, recording devices such as inkjet printers
A dither method or a density pattern method is known as a quantization method, such as a binarization method, for reproducing a halftone image.

However, these methods cannot be used when the original is a halftone image.
There are disadvantages in that moiré occurs in the reproduced image, and when the original contains nine line drawing characters, the edges are cut off and the image quality deteriorates. In other words, these methods were unable to achieve both gradation and resolution.

On the other hand, an error diffusion method is known as a binarization method that can achieve both gradation and resolution.

This method calculates the density difference between the image density of the original and the output density for each pixel, and distributes the error amount, which is the result of this calculation, after applying specific weighting to surrounding images.

This error diffusion method is described in the literature R, W, F1oyd.
and L.Steinberg'An A
adaptiveAlgorithm for 5p
eat-al Gray 5cale SID
It was announced in 75 Di gest (1976).

[Problems to be Solved by the Invention] However, since the error diffusion method described above has no periodicity in the method of binarizing input image data, it causes problems with other binarization methods such as the dither method and the density pattern method. However, when processing the highlight portion of an image, the recorded dots become dispersed, making granular noise noticeable and causing a reduction in image quality.

In addition, in order to express a wider range of gradations, there are known recording devices that record images using multiple inks of different densities, but in this case too, when processing is performed using the error diffusion method, highlights become lighter. There was a drawback that the ink dots were dispersed and grainy noise was noticeable.

(Means and effects for solving the problems) The present invention eliminates the above-mentioned drawbacks and provides a recording apparatus that records images using a plurality of inks of different densities. and processing means for quantizing the plurality of data, and the processing means quantizes data of low density ink and other data among the plurality of data. The present invention provides a recording device characterized in that it performs quantization processing using a quantization method.

As a result, the quantization method for data for low-density ink is different from that for other data, so the image quality of highlight parts can be improved, and it becomes possible to reproduce any input image with high quality.

〔Example〕

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

FIG. 1 is a block diagram of a recording apparatus that is an embodiment of the present invention. In the figure, 1-a is an image input section, which is an image reading section 9 consisting of a photoelectric conversion element such as a CCD and a drive device that scans it.A converts the data read by the image reading section into 8-bit digital data for each pixel. It is composed of a /D converter and a correction circuit that performs corrections such as shedding correction. The density data obtained by reading the original image with the image input section 1-a is LU.
T (lookup table) 1-b. 1-
LLIT b is composed of a ROM (read only memory), etc., and when the density data (00□ to FFH) is input from the image input section 1-a, it is processed at the timing of the clock from the timing clock generation circuit 8. Density data is divided into two density data values, one for light ink and one for dark ink, and output. FIG. 2 is a diagram for explaining the relationship between input and output in LUT 1-b.

In FIG. 2, for example, when density data 7FH is input, ADI is used for light ink (and 3 is used for dark ink).
3. Divide into values and output each. The data for light ink is sent to the comparator 2, and the data for dark ink is sent to the adder 4.

2 is a comparison calculator composed of comparators, etc., and 3 is R
It is a dot design matrix composed of OM or RAM. The comparison calculator 2 reads out the comparison pattern value output from the dot design matrix 3 and calculates the
Compare it with the density data value for light ink output from UTI-b, and if the density data value is larger than the comparison pattern value, 1" is transferred to the delay circuit 7, otherwise, "0" is transferred to the delay circuit 7. .

Reference numeral 7 denotes a delay circuit constituted by a shift register, etc., which is used to correct the deviation in recording timing due to position when attaching the light ink head and the dark ink head.

8-a and 6-b are recording heads for inkjet recording method or thermal recording method, 6-a is for light ink, 6-
b is a recording head for dark ink. Recording head 6-a
, 6-b, for the data "110" sent from the delay circuit 7 and the comparator/subtractor 5, "8/
Perform "non-recording".

4 is an adder, and 5 is a comparison subtracter. These two components perform quantization using the error diffusion method on the density data for dark ink sent from LUT 1-b.

The adder 4 adds together the error between the input data and output data generated in the previous pixel obtained by the comparison subtractor 5 and the dark ink density data value of the pixel of interest, and transfers the result to the comparison subtractor 5. The comparison subtracter 5 compares the density data value sent from the adder 4 with the threshold value "8ON", and if the density data value is larger than the threshold value "80)l, it sets it to 1", otherwise it sets "1". 0" to the recording head 6-b. Further, if the density data value is greater than 80o, "density data value -FF□" is sent, and if the density data value is smaller than "80H", "density data value -FF" is sent. 008'' is transferred to the adder 4 as error data to be diffused to the next pixel.

8 is a timing clock generation circuit that generates a timing clock, which includes LUTI-b, comparator 2, adder 4.
Delay circuit 7. Comparison subtractor 5° recording head 6-a, 6
-b are all operated by clock pulses from the timing clock generation circuit 8 of this line, and each output data is sequentially input to the next circuit in a vibrating line system.

Next, a manner in which a recording operation is performed using the configuration described above will be explained. First, when the density data sent from the image input unit 1-a is input to the LUTI-b, at the rising edge of the timing clock from the timing clock 78, the density data for light ink and the density data for dark ink are Output based on the diagram. The density data for light ink is provided by comparison calculator 2.
It is compared with the comparison data value read from the dot design matrix 3 at the next rising edge of the timing clock, and if "density data value > comparison data value", it is set as "1", otherwise it is set as "1". The dot design matrix 3 is configured as shown in FIG. 3, for example, and a value is read out in the X direction every clock, and the same value is read out repeatedly every four clocks. Furthermore, when the comparison of - rows is completed, +t in the Y direction
The number of rows extending beyond a is incremented, and the same row is read out every fourth row. Furthermore, the output of comparison subtracter 2 is delayed.
It is input to circuit 7. The delay circuit 7 is for correcting the difference in printing timing due to the position of the light ink recording head 6-a and the dark ink recording head 6-b, and is composed of, for example, an n-stage shift register. If so,
Input data is output by n clocks. The binary data output from the delay circuit 7 is input to the recording head 6-a for light ink, and is latched at the rising edge of the timing clock. If it is 1", it is recorded, and if it is "0", it is not recorded. The density data for light ink is quantized using a dither method.

On the other hand, the density data for dark ink outputted by LUTI-b is inputted to the adder 4, and is added to the error outputted by the comparator/subtractor 5 using a timing clock and outputted. Furthermore, the output of the adder 4 is input to the comparator/subtracter 5, and “
80H, and if the input data value is greater than the threshold "80H", it outputs "1", otherwise it outputs "0". Also, the comparison subtractor simultaneously outputs "0" when the input data value is greater than the threshold "80H".
ON", "input data value - FFH" is output, otherwise "input data value -00M" is output as error data to be diffused to the next pixel, and this is output to adder 4.
The concentration data is added to the concentration data input at the next rising edge of the timing clock. The binary data output from the comparator/subtractor 5 becomes an input to the recording head 6-b, is latched at the rising edge of the timing lock, and becomes "1".
”, it will be recorded; if it is “0”, it will not be recorded.

As explained above, according to this embodiment, it is possible to reproduce a wide range of gradations by recording with light ink and dark ink, and furthermore, the data for dark ink is binarized using the error diffusion method. Therefore, it is possible to reproduce an image with both gradation and resolution. Furthermore, since the data for light ink is binarized using the dither method, it is possible to prevent grainy noise in the highlight portions of the image and obtain a high-quality image.

FIG. 4 is a block diagram showing another embodiment of the present invention. In FIG. 4, the same components as in FIG. 1 are given the same reference numerals, and their explanations will be omitted. In the above embodiment, the density data for light ink and dark ink are divided into two by the dither method and error diffusion method using pipeline processing.
was converted into value data, but in this example, RA
It has a line memory 9 of one code constituted by M,
After storing density data for - lines in advance in the line memory 9, the MPU 9 (microprocessor unit)
Read out the density data stored in , and store the data binarized using the dither method for light ink into the binarized data storage memory 10 for light ink, and the data binarized using the error diffusion method for dark ink. are stored in the dark ink binary data storage memory 11, the recording heads 6-a and 6-a, respectively.
6-b.

Note that the present invention is not limited only to the above-mentioned embodiments,
Various modifications are possible.

For example, in the above-mentioned embodiment, the error during binarization is reflected only in neighboring pixels due to the error diffusion method, but by having multiple line memories and adders, the error is reflected in more pixels. It is possible to reflect the

In addition, the comparison pattern matrix in the dither method is also 2
It is possible to adopt various configurations such as x2, 4x4, 8x8, etc.

Further, the processing for density data for light ink is not limited to the dither method, and other binarization methods such as the density pattern method can also be used.

Furthermore, the present invention can be realized by adopting a similar configuration for each color even when performing color recording.

〔Effect of the invention〕

As explained above, according to this embodiment, since the quantization method is different for low-density ink data and other data, the image quality of highlight areas can be improved, and any input image can be reproduced with high quality. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the operation of the LUT, FIG. 3 is an explanatory diagram showing the contents of the dot design matrix, and FIG. 4 is an explanatory diagram showing the contents of the dot design matrix. FIG. 2 is a block diagram showing an example. 1-a... Image input unit 1-b... Lookup table 2... Comparison calculator 3... Dot design matrix 4... Adder 5... Comparison subtractor 6-a, 6 -b... Recording head 7... Delay circuit 8... Timing clock generation circuit

Claims (2)

[Claims] (1) In a recording device that records an image using a plurality of inks having different densities, the apparatus comprises means for dividing input image data into a plurality of data according to the plurality of inks, and quantizing the plurality of data. A recording apparatus, comprising: a processing means, wherein the processing means quantizes low-density ink data and other data among the plurality of data using different quantization methods. (2) The processing means quantizes low-density ink data using a dither method, and quantizes other data using an error diffusion method. Recording device described in ).