JPS63242565A - Density gradation control-type thermal printer - Google Patents

Abstract

PURPOSE:To enable a printing image to be reversed between black-and-white as necessary, by selectively reversing the logical values for all the bits of gradation data. CONSTITUTION:An input terminal of an analog switch 30 is connected to an output terminal of a data comparison circuit 16. When the switch 30 is turned to an output terminal 30a gradation data is supplied to a shift register 104 in a print head 100 as it is. When the switch 30 is turned to the other output terminal 30b, the logical values for all the bits of the gradation data are reversed in an inverter 32 and, then, the gradation data is supplied to the shift resister 104. The 64-gradation data reversed in the inverter is supplied to the shift register 104, and heating resistors Rj are selectively electrically energized according to the information of each gradation bit. As a result, a printing of an image reversed between black-and-white can be obtained. In this manner, by reversing the logical value of the bit having information that whether or not a corresponding heating resistor should be electrically energized for a unit conduction time, a printing image which is reversed between black-and-white can be obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention controls the density gradation of each pixel by energizing a heating resistor element for an energizing time that is an integral multiple of the unit energizing time during a predetermined energizing interval. The present invention relates to a density gradation control type thermal printer designed to print monochrome inverted images as required.

(Prior art) Thermal printing (recording) is a recording method that converts electrical signals corresponding to image information into thermal energy using a heating resistor element, and uses this thermal energy to form a visible image (image) on paper. There are two main types: the direct thermal method, in which heat energy is applied directly to heat-sensitive (coloring) paper, and the transfer-type thermal method, in which heat energy is applied to an external coloring source such as an ink ribbon to transfer ink to the paper.

In the transfer type thermal method, recently, video printers have appeared that give each recording dot (pixel) its own density gradation.
It is expected to be used as a heart coffee device that connects to video receivers, image processing devices, personal computers, and the like.

This moisture gradation method generally applies a constant voltage to each heat generating resistor element of the thermal head and controls the energization time to give gradation to the heat generated energy, thereby changing the amount of ink transferred and thus the density of the image. I try to give it some tone.

FIG. 4 shows the energization time/moisture characteristic curve used in the density gradation method. When the heating resistor element is energized for a energizing time tl corresponding to the unit energizing time Δt, a density of gradation level dl is obtained, and when the heating resistor element is energized for a energizing time t2 corresponding to twice the unit energizing time Δt, the gradation level is obtained. A concentration of d2 can be obtained. In this example, the unit energization time Δt is 6
By energizing for a energizing time tli4 corresponding to four times as long, a maximum gradation level dlli4 near the saturation density can be obtained.

FIG. 5 schematically shows the configuration of a conventional density gradation control type thermal printer. The print head 100 includes a plurality of (for example, 1024) heating resistance elements R1 to R1024.
A shift register 104 and a latch circuit 10B each having a bit capacity l equal to the number (1024) of the heat generating resistors are provided. The gradation data supply unit 108 outputs serial gradation data [:C1PI-CI
It is continuously applied to the shift register 104 times (I: 1 to 64). Here, the n-th bit CIPn has information as to whether or not the n-th heating resistance element Rn should be energized for a unit energization time Δt.

That is, if it is '1', it instructs energization, and if it is '&IQ', it instructs de-energization.

After each gray scale data is loaded into the shift register 104, each bit CI P is loaded at a predetermined timing.
I~C1P1024 is sent to the heat generating resistor 102 as an electric pulse via the latch circuit 106, and the heat generating resistor element R1
-R1024 is selectively energized for a unit energization time Δt according to the information content of the corresponding bit. By repeating this operation 64 times (I=t-14) for the gradation data, energization is performed for a cumulative time length equivalent to 64 times the unit energization time Δt at maximum, and one print is produced. One of the density gradation levels in θ4 is given to each pixel in the line.

The selector circuit 110 arranges the heating resistance elements R1 to R1024 into A group (R1 to R51) in order to avoid excessive power consumption or heat generation when all the heating resistance elements are energized at the same time.
2) and group B (R513 to R1024), and each group is made into a state where it can be energized in a time-divided manner.

FIG. 6 shows the print head 100 printing one frame of a television image. The head 100 has heating resistive elements R1 to R1024 arranged in a vertical direction corresponding to the vertical direction of a television image, and scans in a horizontal direction corresponding to the horizontal scanning direction of the television image. Therefore, each time the head 100 scans one print line at a time, each heating resistor element Rj (j=1-1024) is energized in units according to the information content of the corresponding gradation bit C1PJ (1=1-64). As a result of selectively energizing for an energizing time that is an integral multiple of the time Δt, as shown in FIG.
4 is formed.

(Problems to be Solved by the Invention) As mentioned above, conventional thermal printers of this type can only produce 1/1-tone copies with density gradations corresponding to television images, and are not suitable for daily use. Although this is sufficient for some cases, it may not be sufficient in some cases.

For example, as opposed to making a hard copy of a television image, there is also an application where a photograph is displayed on a television, and in that case it is better to create a television image signal from a negative than from a photographic print to obtain better image quality. However, since such a television video signal is a negative image, if a thermal printer such as the one described above is used, a negative image will be printed, which is inconvenient.

Therefore, in such a case, a thermal printer is required that prints a monochrome inverted image (positive image) from a negative television image.

On the other hand, in the field of design and graphics, it may be desirable to obtain a hard copy of a monochrome inverted image (negative image) from an ordinary television image (positive image). For example, even if the pattern is the same, the positive and negative prints may have different designs. Also, when making prints, you can create a finely grained printed image by attaching a piece of paper with a reversed left-right and black-and-white image to a substrate and engraving it. Even in such a case, it would be convenient to have a thermal printer that prints a monochrome inverted image of the television image.

The present invention has been made in view of such problems, and an object of the present invention is to provide a density gradation control type thermal printer that can invert a printed image in monochrome as required.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a plurality of By generating a predetermined number of gradation data consisting of bits, and sequentially supplying the gradation data to the heating resistor element energizing means at a fixed time period during a fixed energization interval, the density and intensity gradation can be generated for each pixel. The thermal printer is configured to include means for selectively inverting the logical values of all bits of gradation data.

(Function) For example, if 64 gradation bits are set for one pixel, to set the density gradation to 4 out of 64 levels, the logical values of the gradation bits should be from 1st to 4th. is “1” and the subsequent ones (5th to 64th) are “0”. Here, “1
” is information that instructs energization for a unit energization time, and uQ is information that instructs non-energization. As a result, the heating resistor element generates heat for an energization time that is four times the unit energization time, and a pixel having a gradation level (4) is obtained.

However, when the inverting means operates, the logical values of the first to fourth gradation bits are "0" and the logical values thereafter (fifth to 64th) are "1".

As a result, the heat generating resistor element generates heat for an energization time that is 60 times the unit energization time, and the gradation level of the pixel becomes (60), which is a monochrome inversion of gradation level (4).

By performing similar monochrome inversion for other pixels, a print image that is monochrome inverted as a whole is obtained.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the main structure of a density gradation control type thermal printer according to this embodiment. In the figure, parts having the same structure 1 functions as those in FIG. 5 are given the same reference numerals.

A digital monochrome video signal DV is input to the frame memory IO. This digital video signal DV is subjected to predetermined image signal processing in a process circuit 12, and then converted into 8-bit density data FS for each pixel. In this embodiment, each density data FS has a value (gradation level) corresponding to the density of the corresponding pixel within the range of <0><minimum density) to (84) (maximum density). Therefore, the pixels (1024
Density data FSI-FS1024 corresponding to the number of pixels) are temporarily stored in the line memory 14, and then those density data FSI-FS1024 are stored in the data comparison circuit 16.
, where 64 pieces (times) of gradation data [:C1P
It is converted into I-C1P4O10 (1=1 to 84).

The gradation counter 18 provides a total of up to 64 count pulses QP to the data comparison circuit 16 at time intervals corresponding to the unit energization time Δt in each energization interval. Then, when the gradation counter 18 generates the count pulse QP, the DMA controller 20 accesses the line memory 14 in synchronization with it and reads out the density data FS1-FS1024.

The data comparison circuit 16 calculates the cumulative value N of the count pulses QP.
The gradation level DN corresponding to the gradation level DN is compared with each density data FSj as a comparison reference value, and when the latter is equal to or larger than the former, a gradation bit CI Pj of "1" is generated.

For example, concentration data FSI, FS2. When the values of FS3 are <10>, <2>, and <1>, respectively, the comparison reference value is (1) in the first comparison in response to the first count pulse QP, so it is output at this time. First gradation bits CI Pl, CI P2. ClF3 is “1” respectively.
", '1", 41". In the second comparison in response to the second count pulse QP, the comparison reference value is (2).
Therefore, the second gradation bit C2P output at this time
I, C2P2. C2P3 is "1", '1', '
Then, when the third count pulse QP is given, the comparison reference value becomes (3), and the third gradation bits C3Pl, C3P2.C3P3 each become "1".
, '0'', '0''.

In this way, each concentration data FSj (j = 1 to 024) is compared with the comparison reference value (1 to 64) incremented by 1 during one energization interval, and the 84 pieces (times) of gradation data [CIPl, C
I P2. CI P3. ...CI P1024] ~ [
CG4P1. C64P2. CG4P3. ...CG4
P 1024] are sequentially output from the data comparison circuit 16.

Now, according to this embodiment, the input terminal of the analog switch 30 is connected to the output terminal of the data comparison circuit 18. When this switch 30 is switched to one output terminal 30a, the gradation data is supplied as is to the shift register 104 of the print head 100. but,
When the switch 30 is switched to the other output terminal 30b,
The gradation data is supplied to the shift register 104 after the logical values of all bits are inverted by the inverter 32 .

That is, the gradation data [CI PI, CI P2 . CI P3. ...C
IPI024] is, for example, [:1, 1 . O,...1]
When , the inverted data co, o, i, ... 0
] will be supplied to the shift register 104.

Such switching of the switch 30 is performed by the switching control signal SW from the CPU 22.
When SW is "1", the switch is switched to the output terminal 30a, and when SW is "0", the switch is switched to the output terminal 30b. C
The PU 22 sets the SW to "1" in the normal mode, but sets the SW to "0" when the monochrome inversion button 36 is pressed.
”

Now, as described above, the 64-time gradation data [C1Pl, CI P2 . CI P3. ...
・CI P1024] (1=1 to 84) is supplied to the shift register 104, and the heating resistor element Rj is selectively energized according to the information content of each gradation bit CIPj, so that the result is as described below. A print of a monochrome inverted image can be obtained by this action.

That is, taking one pixel formed by the heating resistive element RJ as an example, and assuming that the value of the density data FSJ for this pixel is (10), in this case, the corresponding 64 gradation bits CI Pj-CG4Pj are the first 1st from the
Up to 0 times (CI PJ - C10PJ) are each "1"
”, from the 11th to the 64th (CIOPj-Cll
i4PJ) is “0”.

Therefore, in the normal mode, the heating resistance element Rj is energized continuously from the 1st to the 10th time, and is not energized thereafter, resulting in energization for a cumulative time length corresponding to 10 times the unit energization time Δt. As a result, pixels of density gradation level dlO are obtained.

However, in monochrome inversion mode, the same density data FS
Even if PJ
~shi1UPJJfli? From the 11th to the 64th (CIIPJ -CG4Pj) is "1" in n dere-U-'
becomes. Therefore, the heating resistance element Rj in this case is the first
The current is not applied from the 11th time to the 10th time, and the current is applied continuously from the 11th time to the 64th time, and as a result, the density gradation level d5 is reached by energization for a cumulative time length corresponding to 54 times the unit energization time Δt. pixels will be obtained.

As shown in Figure 4, the gradation level is 1 degree and the bell d54 is yQ.
This level is almost in contrast to the degree gradation level dlO.

Similarly, by giving monochrome-inverted gradation levels to other pixels, a monochrome-inverted print image can be obtained as a whole.

Note that in this embodiment, in addition to monochrome reversal, left-right reversal is also possible. This left/right reversal changes the line memory 14 to L I F O (Last In, First 0u
t). That is, when the line memory 14 performs LIFO operation, the arrangement order of the concentration data FSI-FS 1024 is reversed. Then, the data comparison circuit 16 receives the FS voltage 024. F
S1023. ...FS2. The gray scale bits are supplied in the order of FSI, and in the monochrome inversion mode, the order of grayscale bits input to the shift register is CI P4O10, CIP102
3. ...CI P2. Became CI PI, CIPJ
Ol controls the energization of the heat generating resistor element R1, and CI Pi controls the heat generating resistor element R1024.

As a result, when the print head 100 performs print scanning,
A print image 120 as shown in FIG. 2 is formed, and when it is turned upside down, it becomes something like the one shown in FIG. Available.

In FIG. 1, the left/right reversal button 38 is a button used when a left/right reversed print image as described above is desired.
When this is pressed, the CPU 22 responds and switches the line memory 14 from normal FIFO to LIFO via the DMA controller 20.

Note that the CPU 22 selects group A (
An instruction signal SE is given to instruct whether to enable energization of R1-R512) or to enable energization of group B. latch·
The strobe generation circuit 30 responds to the count pulse QP and provides the latch circuit 14 with a latch timing signal LT and the selector circuit 14 with a voltage application timing signal VT. Shift register 104. The latch circuit 106 and the heat generating resistor 102 constitute a heat generating resistor energizing means.

(Effects of the Invention) As described above, the present invention provides monochrome inversion by inverting the logical value of a bit that has information on whether or not to energize one heating resistor corresponding to it for a unit energizing time. The present invention has the effect of greatly expanding the usage and range of applications of this type of thermal printer.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main configuration of a density gradation control type thermal printer according to an embodiment of the present invention. FIG. 2 is a printing operation of the thermal printer of FIG. 1 in monochrome reversal and horizontal reversal mode. FIG. 3 is a schematic plan view showing a printed image obtained by the printing operation shown in FIG. 2; FIG. 4 is a diagram showing an energization time e moisture characteristic curve used in the density gradation method; FIG. 5 is a block diagram showing the main configuration of a conventional density gradation control type thermal printer, and FIG. 6 is a schematic plan view showing how the print head in FIG. 5 prints one frame of a television image. , FIG. 7 is a schematic plan view showing a print image obtained by the printing operation shown in FIG. 6. In the drawings, 14... line memory, 16... data comparison circuit, 18... gradation counter, 20... DMA controller, 22... CPU, 30... analog Switch, 32... Inverter, 36... Monochrome inversion button, 100... Print head, 1
02... Heat generating resistor, 104... Shift register, 106... Latch circuit, R1, R2,...
R1024...Heating resistance element. Figure 1 Figure 2 Figure 3 Figure 4 Figure 6 Figure 7

Claims (1)

[Scope of Claims] Generate a predetermined number of gradation data consisting of a plurality of bits in which each bit has information on whether or not to energize one heating resistor corresponding to it for a unit energization time,
In a thermal printer in which a density gradation is given to each pixel by sequentially supplying the gradation data to a heating resistor element energizing means at a fixed time period during a certain energization interval, all bits of the gradation data are A density gradation control type thermal printer characterized by comprising means for selectively inverting logical values.