JPS62284574A - Image recorder - Google Patents

Abstract

PURPOSE:To record high-resolution binary images by modulating recording energy supplied to each dot of a multivalued image recording signal generated by selecting a fixed pattern formed in a matrix according to a multivalued image signal individually according to the binary image signal. CONSTITUTION:The multivalued image signal read out of a line memory 4 is inputted to a multivalued density pattern generator 5. The multivalued density pattern generator 5 is controlled by an X counter 14 and a Y counter 15 for matrix generation to generate the multi valued image recording signal consisting of a multivalued density pattern. A binary image signal read out of a frame memory 8 for binary image storage is inputted as data corresponding to each dot of a thermal head and the recording energy supplied to each dot of the multivalued image recording signal is modulated with this binary image signal. Consequently, high-resolution binary images are recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Objective of the Invention 1 (Industrial Application Field) This invention relates to an apparatus for recording images by a thermal transfer recording method, etc. The present invention relates to an image recording apparatus that performs pseudo halftone expression using a pattern method.

(I! Future technology) The thermal transfer recording method presses a thermal head against the recording paper through an ink film using heat-melting or heat-sublimating ink, and uses the heat generated when the heating resistor of the thermal head is energized. This is a method in which ink on an ink film is transferred to recording paper.

This method is originally suitable for recording binary images with only density levels NJ and rOJ, and when recording multivalued images, that is, images with gradation, it features a special density modulation technology. This 8111 patent describes a conventionally known modulation technique in which the energy supplied to the heating resistor of a thermal head is modulated to control the thermal diffusion area within the ink film to change the size of the recording dot. .

This method has a narrow range of variable density that can be expressed, and in the case of thermal transfer recording, the spread of transferred ink is random, resulting in variations in dot shape and size and unstable gradation. have. In addition, there are also problems such as the recording density shifting over time due to heat storage development peculiar to thermal recording, and it has been difficult to express halftones with this type of method.

Therefore, attempts have been made to perform pseudo-halftone recording in which a halftone image is expressed by dot density or ink occupancy within a certain area. This is a method widely used to express gradation in dot printers that have only binary density expression capability, and the dither method and density pattern method are typical examples. The dither method is a method of binarizing a multilevel image using a threshold pattern as shown in Figure 5, and the density pattern method has a one-to-one correspondence with the gradation level as shown in Figure 6. This is a method of recording a multivalued image using a fixed pattern.

The present inventors have also proposed a multi-IlIIm pattern method, which is a further development of the density pattern method (see Japanese Patent Application No. 16768/1983). In the dither method and the normal density pattern method, the number of gradations necessary to obtain an image without a-color, taking human visual characteristics into account.

Solution 111r! It is difficult to satisfy both of l. In addition, due to the heat storage effect in the thermal head, discontinuities in gradation occur, such as areas that should be treated as white, especially in medium and high turbidity areas, and areas that should be treated as white, especially in low and medium turbidity areas. There are problems such as noticeable roughness in the image due to unstable ink characteristics in the fi region. According to the multilevel density pattern method described above by the present inventors, by actively utilizing the heat storage effect of the thermal head, which has been considered an obstacle to good recording in the past, graininess can be achieved with stable gradation. This makes it possible to record high-quality images with less noise.

For example, as shown in FIG. 7, this multilevel density pattern method
One pixel is composed of a matrix of multiple dots such as 3 x 3, and the density level range of the multivalued image signal is divided into multiple partial density regions, such as a low density region, a medium density w
A Occupation area. The density region is divided into three, and three fixed patterns A to C are used corresponding to each of these partial density regions.

The fixed patterns A to C are multivalued patterns in which the recording energy applied to the dots constituting them can be modulated in accordance with the density level of the multivalued image signal (see FIG. 9).

Specifically, for example, fixed pattern A for low S degree is an isolated dot pattern formed by isolating one dot in one pixel, and the gradation of the low density area is determined by recording energy (energy injected into the thermal head). It is expressed by modulating the dots and changing the size of the dots. Fixed pattern B for medium density is based on the relative movement direction (r) between the thermal head and the recording paper.
It is a striped pattern extending in the yI scanning direction),
The medium 1 degree fabi gradation is expressed by changing the thickness of the stripe depending on the injection energy of the thermal head. Roughly speaking, the fixed pattern C for high 1 degree is an L-shaped pattern with a white part for 2x2 dots, and for high density gradation, the area of the white part is changed by the injection energy of the thermal head. It is expressed by letting. If halftone recording is performed using such a multilevel density pattern method,
The problems encountered in dithering or conventional density patterning methods are eliminated.

However, the above-mentioned multi-value density pattern method or normal density pattern method is designed for recording multi-value images, and when handling binary images, one pixel of image data is N
The data is enlarged to a matrix size of XN and recorded. For this reason, the resolution of the thermal head or the like which is the recording means cannot be fully utilized, resulting in a decrease in the resolution of the recorded image.

(Problems to be solved by the invention) In this way, in the density pattern method and the multi-meter density pattern method,
When recording a binary image, there is a problem in that the resolution is lower than in a normal binary image recording method.

Accordingly, an object of the present invention is to provide an image recording apparatus that can record a binary image by making maximum use of the resolution of the recording means without degrading the image quality of the multilevel image.

[Structure of the Invention] (Means for Solving the Problems) The present invention uses the density pattern method or the multi-fai one-degree pattern method for recording multivalued images, that is, in a matrix consisting of a small number of dots representing one pixel. This is performed using a multi-valued image recording signal generated using at least an operation of selecting a fixed pattern formed in the multi-valued image data according to the multi-valued image data. Recording of a binary image is performed by individually modulating the recording energy given to each dot of the multilevel image recording signal in accordance with the binary image signal.

(Function) When a binary image signal is input, the density of the dot for which a binary image is to be recorded is determined from among the series of multilevel image recording signals obtained by selecting a fixed pattern according to the multilevel image signal. The level, ie the recording energy applied to the dot, is modulated in accordance with the binary image recording. Therefore, while the multi-meter, m-degree pattern method or density pattern method is used to record multi-level images, the resolution of recording means such as a thermal head is maximized for binary images, as in normal binary image recording. High-quality recording will be made using the system.

(Example) Figure 1 shows an example of applying the present invention to an image recording unit 11m1t that records a multivalued image using a multi-1111 degree pattern method.
It shows the main points.

In FIG. 1, the CPU is used to operate the entire apparatus 111M, and controls the image capture device 2, the binary image generation circuit 7, and the synchronization signal/clock generation circuit 13.

The image reading device 2 is a device that obtains an image signal by reading an image on a document including halftones, and the image signal is converted and output as a multivalued digital signal (for example, expressed by 8 bits per pixel). .

The multivalued image storage frame memory 3 is an image memory for storing image signals for one page of a document read by the image reading device 2, and is unnecessary if the reading operation and recording output operation are not temporally separated. It is.

The binary image generation circuit 7 is a circuit that generates image signals such as binary graphics and two characters under the control of the CPIJ 1, and the generated binary image record is stored in the frame memory 8 for storing binary images. The data of one pixel in the frame memory 8 for binary image storage is expressed by 1 bit, and the resolution at the time of output is different from that of 1 pixel of the picture a@ stored in the frame memory 3 for multilevel double edge storage. .

Thermal transfer record! The device control circuit 12 is a circuit for controlling the thermal transfer recording device 11, and controls the conveyance of ink ribbons, recording paper, etc. according to commands from the CPU 1.
etc. The synchronization signal/clock generation circuit 13 is
Generates the cycle of one line required when transferring signal data, timing clock for data transfer, etc.
Supplies the necessary circuits.

When performing normal multi-value image recording, that is, halftone recording in the image recording apparatus having the above configuration, first the data of the multi-value image signal stored in the multi-value image storage frame memory 3 is transferred to the line memory 4. Transfer one line to . 1stilIilIr! One pattern generator 5 uses this one line of data to generate a multi-line pattern recorded in NXM dots.
A multivalued image recording signal consisting of an ai 1 degree pattern is output. This multi-valued image recording signal has a spatial size N times greater in the main scanning direction and M times (M lines) in the 81 scanning direction with respect to the multi-valued image signal inputted to the multi-111i density pattern generator 5. Each will be enlarged. Therefore, the line memory 4 stores one line of multi-value 1 for every M lines of the multi-value image recording signal.
The image signal is read out from the frame memory 3 for storing multivalued images.

The multi-value image recording signal output from the multi-value density pattern generator 5 passes through the multi-value/binary switching circuit 9 and is input to the thermal head drive circuit 10. This thermal head drive circuit 10 has multiple &? ! This circuit converts the 1111 degree pattern given by the image recording signal into the pulse width of the thermal head driving pulse, and controls the energy m injected into the thermal head.

Next, a case will be described in which a binary image is combined with a multivalued image and recorded. FIG. 3 is a block diagram showing in more detail the multi-value density pattern generator 5 to the multi-value/binary switching circuit 9 shown in FIG.

In FIG. 3, the multi-IIIIi image signal read out from the first @ line memory 4 is
5 is input. This lot 1ii! The 11 degree pattern generator 5 is controlled by an X counter 14 and a Y counter 15 for matrix generation, and generates a second (multi-tag pattern (formed by a 4×4 matrix in this example) as shown in K(a)). A multivalued image recording signal is generated.

On the other hand, the binary image signal read from the first @ binary image storage frame memory 8 is input to the synthesis mode switching and switching signal generator 9b.

This binary li! ii An example of the signal pattern is shown in Figure 2 (b
). The switching signal output from the synthesis mode switching and switching signal generator 9b is multi-valued depending on the synthesis mode switching signal, and the 1 switching unit 9a outputs mainly a binary image recording signal as shown in FIG. 2(C). This is a signal for switching whether to mainly output a multivalued image recording signal, or a multivalued image recording signal as shown in FIG. In order to determine the recording density of the binary image, the binary image density generator 6 generates a recording dot of exactly 1.
This is a circuit that generates a signal that specifies the recording energy (energy injected into the thermal head) to achieve the dot size. Shows energy.

FIG. 4 is a timing chart showing the operation of FIG.
It corresponds to the dot recording time.

The multi-value image signal is switched once every four periods of the dot clock, and during this period the multi-value density pattern generator 5 switches the X counter 14.
A four-dot multi-valued image recording signal is generated under the control of the four dots. A binary image signal is input as data corresponding to one dot on the thermal head, and this binary image signal l! The recording energy given to each dot of the multilevel image recording signal is modulated by the i-image signal. That is, the recording energy given to the dot where the binary image signal is "1" in the series of multi-value image recording signals is determined by the combination of the multi-value image and the binary image shown in FIG. 2(C) or (d). It is switched according to the mode, and finally the recording signal output 1 or 2 shown in FIG. 4 is obtained.

In this way, we can create a multivalued image using the multi-11!1 degree pattern method and a two-dimensional image in which one pixel corresponds to one dot of the thermal head.
It becomes possible to perform mixed recording with tiijm.

Note that the present invention is not limited to the above embodiments,
For example, the multi-dimensional pattern generator 5 in FIG. Binary image density generator6. It is also possible to configure the multi-value/binary switch 9a, ffi, synthesis mode I, 7J switching and switching signal generation B9b by replacing them with a ROM pattern table 16 as shown in FIG.

Furthermore, in the present invention, the binary image signal may be a signal obtained by performing processing such as edge detection or two thin line character detection on a multivalued image signal and converting it into a binary signal.

In addition, in the above embodiment, the recording of a multivalued image is performed using the multilevel pattern method explained using FIGS. 8 and 9, that is, the density level range of a multivalued image signal is
A fixed pattern is selected depending on which partial density area the multi-valued image signal exists, and the recording energy given to the dots constituting the selected fixed pattern is adjusted to the 1-degree level of the multi-valued image signal. The conventional density pattern method shown in Fig. 7 was used, that is, the one-time pattern method using a fixed pattern that corresponds one-to-one to the gradation level of the multivalued image. It is also effective when

In this normal density pattern method, since the recording energy of each dot takes only binary values, a binary a degree generator is not required.

In addition, when recording an image from a color 11i image reading means, a color image sensor (low resolution) and a monochrome image sensor (high resolution) are used as the image reading means, and based on the ii* signal from the monochrome image sensor. It is also possible to determine whether the image is a binary image or a multivalued image.

Furthermore, although thermal transfer recording has been described in the above embodiments, the present invention can also be applied to wire tod type impact printers and electrophotographic recording devices.

In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[Effect of R Light] According to the present invention, in an image recording device that records one pixel by selecting a fixed pattern formed in a matrix represented by a plurality of dots, when recording a binary image, one pixel can be made to correspond to one dot of the recording means, and it is possible to record a high-resolution binary image determined by the resolution of the recording means without degrading the image quality of the multivalued AIII image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an image recording apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a schematic configuration of an image recording apparatus according to an embodiment of the present invention. A diagram for explaining how to apply recording energy to each dot, FIG. 3 is a block diagram showing the configuration of the main part of FIG. 1 in detail, FIG. 4 is a time chart showing the operation of FIG. 3, and FIG. FIG. 5 is a block diagram showing the configuration of main parts according to another embodiment of the present invention, and FIGS. 6 to 9 are diagrams for explaining a conventional multi-level image recording method. 3... Frame memory for multi-value image storage, 5... Multi-value density pattern generator (multi-value ii!i@recording signal generation means), 6... Binary image density generator, 7... Binary image generation circuit, 8... Frame memory for binary image storage, 9.
. . . Multivalue/211 switching circuit, 10 . . . Thermal head drive circuit, 11 . . . Thermal transfer recording device. Applicant's agent Patent attorney Takehiko Suzue CPU Bus Rhino 1st prisoner 2nd figure

Claims (3)

[Claims] (1) Means for generating a multivalued image recording signal by configuring one pixel as a matrix of a plurality of dots and selecting a fixed pattern formed within the matrix according to a multivalued image signal; An image recording apparatus comprising means for individually modulating recording energy given to each dot of a value image recording signal according to a binary image signal. (2) The means for generating a multi-valued image recording signal divides the density level range of the multi-valued image signal into a plurality of partial density regions, and a fixed pattern is formed depending on which partial density region the multi-valued image signal exists. 2. The image recording device according to claim 1, wherein the image recording device selects the fixed pattern and modulates the recording energy applied to the dots constituting the selected fixed pattern in accordance with the density level of the multivalued image signal. . (3) Image recording according to claim 1, wherein the means for generating the multi-valued image recording signal uses a fixed pattern that corresponds one-to-one to the gradation level of the multi-valued image. Device.