JPH0829602B2 - Density gradation control type printer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a density gradation control type printer for performing density gradation control.

[0002]

2. Description of the Related Art Generally, in a density gradation control type printer,
A large number (for example, 10 pixels) corresponding to the printing pixels on one printing line.
The thermal head in which the heating elements of 24) are described in a row is used. At the time of printing, these heating elements are pressed against the recording paper via an ink ribbon or the like. Then, each heating element is energized according to the energization time data to supply power to the heating element, and one line of dots is printed from the ink ribbon to the recording paper. For example, in the case of performing gradation expression for each dot using a density gradation control type printer, the number of gradations is equal to the number of gradations for one line printing (up to 256 gradations in 256 gradations).
It is necessary to print multiple times.

FIG. 4 shows a circuit configuration of a conventional density gradation control type printer. Here, for example, the thermal head 116
The number of data inputs is 8, the number of pixels per data input is 128, and the number of heating elements is 1024.

In the thermal head 116, eight serial head data [CK P1J to CK P10 of 1 bit from the data comparison circuit 122 are supplied during the energization time of one printing line.
24J] is continuously transferred 256 times (K = 1 to 256) in a constant cycle. The Fth bit CKPFJ has information as to whether or not to energize the Fth heating element RF. If the bit is "1", the unit energization time ΔT is energized, and if it is "0", the current is not energized.

The image memory 110 stores image data input from an external interface (not shown). Then, when printing is performed, the image data for one line is read and given to the density-energization time conversion ROM 112. In the density-energization time conversion ROM 112, the image data for one line is converted into energization time data representing the energization time.

Next, the energization time data is divided into 128 pieces corresponding to the number of pixels per data input and is divided into RAMs.
It is stored in 114.

The energization time data stored in the RAM 114 for every 128 pieces of data is sequentially read and given to one input terminal of the data comparison circuit 122. The other input terminal of the data comparison circuit 122 is supplied with the gradation data DN output from the gradation counter 120 and indicating the current number of gradations.

Then, the data comparison circuit 122 compares the energization time data with the gradation data, and the output signal of the data comparison circuit 122 is "when the condition of" energization time data> gradation data "is true. 1 ", and the head data CK PFJ (K = 1 to 1 given to the thermal head 116
256) is generated. The above-described operation is repeated for several gradations to print one line.

FIG. 5 shows the relationship between image data and pixel size. For example, when the image data has a size of "255", the heating element of the thermal head 116 is always in the state of "1" during the energization period when the thermal head 116 can be energized. And the power is turned on. At this time, the pixel size becomes maximum. Paper feed of one line pitch is also performed at the same time during the energization period.

[0010]

However, when the image data is "128", energization is performed only for half the energization period. Therefore, the image data is "255".
However, the pixel size is about half that of the above.

As described above, in the head data generating method such as the conventional density gradation control type printer, the print pixel size is proportional to the energization time data. For this,
The print pixel size becomes non-uniform, which adversely affects the print quality.

On the other hand, in addition to the above-described density gradation control type printer, the following multi-gradation printer has been proposed. That is, a table showing the relationship between the energization time and the color density that is measured and determined in advance, a parameter determined by the characteristics of the analog input signal such as a video signal, or a parameter preset by the user, and is uniquely This is a system that has means for creating another table in which the contents of the table are changed, and refers to the other table according to the analog input signal, and determines the energization time based on the content, which is disclosed in JP-A-61-123362. It is shown in the official gazette.

However, in this method, a unique function that gives the energization time for the input signal level having the most appropriate gradation according to the signal is determined from the above-mentioned parameters and another table is created, so that the image quality There are restrictions on points and the configuration becomes complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a density gradation control type printer which can make the printing pixel size uniform and can obtain high image quality. .

[0015]

In order to achieve the above object, a density gradation control type printer of the present invention is provided with an image memory for storing image data and a predetermined direction from the image memory in the printing line direction. Image reading means for reading image data for each unit, and density for converting the image data into energization time data indicating energization time of the thermal head-
Energization number conversion means, serial conversion means for converting the energization time data into serial gradation data for transferring to the print head as serial head data, and data writing means for storing the serial gradation data in RAM. And a data transfer unit for transferring serial gradation data to the print head in the number of gradations of image data or more,
The data transfer means includes reference bit data read means for reading reference bit data stored in advance in the ROM, and head data read means for reading serial gradation data as head data from the RAM in accordance with the reference bit data. It is characterized by that.

[0016]

The image reading means, the data writing means, and the head data reading means are realized by control means for controlling the above-mentioned respective parts in a predetermined procedure.

[0018]

According to the above construction, the image data to be printed which is fetched from the outside is stored in the image memory. In the image data stored in the image memory, for example, if the thermal head is of the 128-data 8-input type, the data (8 bits) is read every 128 times 8 times, and the 8 data is converted into energization time data. After that, it is converted into serial data by the serial conversion means.

At the same time, a data address indicating the first of 128 data is given to the lower address of the RAM. Then, the eight serial data output from the serial conversion means are sequentially given, for example, from the LSB (least significant bit) side, a position address indicating a bit position is given to the RAM, and each serial data is converted into a predetermined address eight times. Store. In reality, since the 128 data 8-input system is used, this operation is repeated until the data address becomes 128, and the data is stored in the RAM as energization data.

Next, when the energization data is transferred to the thermal head, a data address indicating the position of 128 data of the thermal head is given to the RAM, and further, the energization data of MSB (most significant bit) to LSB of the serial data. Reference data indicating whether to refer to
Energization data is given to the thermal head. Then, this operation is repeated until the data address becomes 128, and this operation is repeated 256 times or more for 256 gradations.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a circuit configuration of a density gradation control type printer according to an embodiment of the present invention. However, this is the case where the number of data inputs of the thermal head 18 is 8, the number of pixels per data input is 128, and the number of heating elements is 1024. The number of data transfers to the thermal head 18 is 768
Let's do it.

In the thermal head 18, the head data [CKP] is sent from the RAM 16 during the energization time of one printing line.
1J to CK P1024J] is 768 times (K = 1 to 7) in a constant cycle.
68, J = 1 to 8) Transferred continuously. The Fth bit CKPFJ has information as to whether or not to energize the Fth heating element RF. If the bit is "1", the unit energization time ΔT is energized, and if it is "0", the current is not energized.

At this time, in the serial gradation data stored in the RAM 16, the data of the bit referred to by the reference bit data read from the reference bit data ROM 22 according to the value indicated by the data transfer counter 22 is read as head data. . When the printing operation as described above is completed for one printing line, the paper feeding of one line pitch is completed, and the printing operation for the next printing line is performed.

Next, the serial gradation data stored in the RAM 16 is created as follows. First, image data for one screen is externally stored in the image memory 10 (not shown).
Is entered. Image data [DN, D from the image memory 10
N + 128, DN + 256, DN + 384, DN + 512, DN + 640, DN
+768, DN + 898] are sequentially read out. N indicates the number of the pixel at present for one data input of the thermal head 18. However, N = 1 to 128
Is. The read image data is provided to the density-energization number conversion ROM 12, respectively. In the density-energization number conversion ROM 12, the image data is converted into energization number data [EN, EN + 128, EN + 256, EN + 384, EN + 512,
EN + 640, EN + 768, EN + 898].

Next, these eight energization frequency data are
The signals are sequentially supplied to the serial conversion circuit 14. The serial conversion circuit 14 converts the given eight energization count data from a parallel data string into a serial data string, and converts each energization count data into 8-bit serial gradation data. Then, the serial gradation data is sequentially output from the LSB bit side. At the same time, the remaining 7 serial gradation data are also output from the LSB bit side,
In total, eight pieces of serial gradation data are given to the RAM 16 and sequentially stored.

At this time, the following data is given to the address input of the RAM 16. The lower address is provided with bit data output from the bit counter 26 and indicating what number bit the serial gradation data is currently. At this time, the select circuit 28 is selected so as to give the bit data to the RAM 16. Dot data that is output from the dot counter 30 and indicates the number of the pixel at present for one data input of the thermal head 18 is given to the upper address.

Next, the serial gradation data stored in the RAM 16 is read as head data [CK P1J to C] as follows.
K P1024J]. The data transfer counter 22 outputs data indicating the number of times the data is currently transferred, and the data is supplied to the reference bit data ROM 24. Reference bit data ROM 24 to RAM
Reference bit data indicating which bit of the serial gradation data stored in 16 is selectively referred to is read out. At this time, the select circuit 28 is selected so as to give the reference bit data to the RAM 16, and the reference bit data is given to the lower address of the RAM 16. Dot data indicating the number of the pixel for one data input of the thermal head 18 is given to the upper address.

As shown in FIG. 2, the serial gradation data referred to by the address thus specified is read out as head data from the RAM 16 in synchronization with the clock signal CLK for data transfer, and as the data signal DATA. It is given to the thermal head 18. Then, the thermal head 18 is supplied with a latch signal LATCH for fetching head data inside. Then, the strobe signal STB, which is the energization permission signal for the thermal head 18,
The heating element is energized according to the state of the data signal DATA only during the period of 0 ".

Next, FIG. 3 shows the relationship between image data-pixel size and print density according to the present invention. Due to the relationship between the image data and the pixel size, the pixel size is constant regardless of the size of the image data. Further, the print density increases in proportion to the size of the image data due to the relationship between the print density and the pixel data.

In order to perform such density gradation control,
Reference bit data is stored in the reference bit data ROM 22 as shown below. The number of density gradations is 256 in order to read serial gradation data evenly during the energization period.
8-bit data in gradation (data is LS of 8-bit data
The first bit, the second bit, ... The eighth bit from the B bit. ), The reference count is 256 transfers of 1
As a cycle, the first bit is once, the second bit is twice ... The eighth bit is 128 times and the reference number is 2N-1 times (N = 1 to 8) for the Nth bit. Become.

This cycle is repeated 3 times 768
Data transfer once.

Further, in order to temporally reduce the number of simultaneously energized heating elements of the thermal head 18, the reference bit data is divided into four groups for each pixel of one input of the thermal head 18 and divided into four groups. The type of reference bit data is stored and sequentially selected by the select circuit 28 in one data transfer cycle, and the RAM 16 is selected.
Give to. Therefore, the data SN for referring to the Nth bit is stored in groups of 2N-1 * 3 so that the same bit is not referred to in each data transfer cycle for each group.

By storing the reference bit data in the reference bit data ROM 24 in advance in this manner, it becomes possible to read out the serial gradation data evenly during the energization period. In this way, it becomes possible to give a linear characteristic to the relationship between the image data and the print density.

In the embodiment of the present invention, in order to read serial grayscale data on average, the number of data references per 256 transfer times is 2N-1. However, it is also possible to set the reference frequency of each bit according to the characteristics of the ink ribbon or the like.

In the embodiment, the number of data transfers is 768.
Although the number of times of transfer is set, it is possible to set an arbitrary number of times of transfer.

In the embodiment, the reference bit data is transferred to the head 1
Although the pixels of one input of 8 are divided into four groups and four types of reference bit data are stored, the pixels can be divided into arbitrary groups.

[0037]

Since the present invention has the above-mentioned structure, it has the following effects.

In the density gradation control type printer of the present invention, since the reference bit of the serial gradation data is selected on the basis of the reference bit data stored in advance, it is possible to transfer the density gradation several times or more. Therefore, the density gradation control becomes easy and the gradation property can be improved.

Further, by storing the reference bit data so that each bit of the serial gradation data is averaged and referred to during the energization period, each heating element of the thermal head can be uniformly energized. Therefore, the print pixel size becomes uniform, and high image quality can be realized.

The reference bit data is divided into arbitrary groups for one input pixel of the thermal head, and the reference bit data is set for each group. It is possible to control the number, and it is possible to reduce the load on the thermal head power supply.

Further, since the reference bit data is stored in the ROM in advance, even if the type of the ink ribbon is changed, it can be changed easily and good printing can be realized.

By using the ROM as the reference bit data, experimental or statistical data can be used, and
Data processing can be performed at high speed.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a density gradation control type printer of the present invention.

FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG.

FIG. 3 is a diagram showing the relationship among image data, pixel size, and print density according to the density gradation control method of the present invention.

FIG. 4 is a configuration diagram of a conventional density gradation control type printer.

FIG. 5 is a diagram showing a relationship between image data and a pixel size according to a conventional density gradation control method.

[Explanation of symbols]

 10 image memory 12 density-energization number conversion ROM 14 serial conversion circuit 16 RAM 18 thermal head 20 system control unit 22 data transfer counter 24 reference bit data ROM 26 bit counter 28 select circuit 30 dot counter

Claims (1)

[Claims] 1. A density gradation control type printer for gradation printing by supplying predetermined power to a plurality of heating elements arranged in a printing line direction, an image memory for storing image data, and the image memory. Image reading means for reading out image data for each predetermined unit in the printing line direction, density-energizing number converting means for converting the image data into energizing time data indicating energizing time of the thermal head, and the energizing Serial conversion means for converting the time data into serial gradation data for transferring to the print head as serial head data, data writing means for storing the serial gradation data in the RAM, and more than the gradation number of the image data. A data transfer means for transferring the serial gradation data to the print head; A reference bit data reading means for reading the reference bit data stored in the OM;
A density gradation control type printer comprising head data reading means for reading serial gradation data as head data from the RAM according to the reference bit data.