JPS63230367A - Thermal head driving apparatus - Google Patents

Abstract

PURPOSE:To make the height and high speed property of image quality at the output time of an image compatible, by providing two kinds of energy operation parts, that is, an energy operation part for high image quality and an energy operation part for a high speed and changing over operations corresponding to the nature of an image to be outputted. CONSTITUTION:The operation mode of a circuit can be changed over between a high image quality mode and a high speed mode by a mode change-over signal SM. At the time of the high image quality mode, the heat accumulation contributing data SiA based on the pixel from the third ROM 55 is supplied to an operator 56 for operating the heat accumulation data of a heat insulating layer and, in said operator 56, operation is performed on the basis of an operation parameter for high image quality. At the time of the high speed mode, the applying energy data E to an aiming pixel is controlled corresponding to the applying energy of the previous line wherein the effect of heat accumulation to the desired pixel is largest, and the printing data Di+1, Di-1 of adjacent pixels. Therefore, when printing data is continuously applied to the same heat generating element, applying energy advancing heat accumulation and applying energy supressing heat accumulation are alternately applied and depend on the printing data of adjacent pixels.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a thermal head driving device that electrically excites a thermal head in which a plurality of heat generating resistors are arranged, and causes each heat generating resistor to generate heat individually. Regarding.

[Conventional technology and its problems]

There are various types of image recording devices used in copying machines, facsimile machines, etc., one of which is transfer type thermal recording. This transfer-type thermal recording transfers ink from an ink donor sheet onto a recording paper by causing each heating resistor of a thermal head to generate heat individually according to an image signal. Therefore, it is possible to record on plain paper, and it is easy to print in color. For these reasons, transfer type thermal recording has recently come to be widely applied to color printers, color copying machines, plain paper facsimiles, and the like.

In such devices, there is a strong demand for faster transfer type thermal recording and higher image quality.

An application of transfer type thermal recording to a color copying machine is described in Japanese Patent Application Laid-open No. 85675/1983 by the present applicant. As shown in FIG. 4, the recording section 41 is provided with 41Y, 41M, and 41C for each recording color of black, yellow, magenta, and cyan.

In each of these recording units, 42Y, 42M, 42C are applied to the ink donor sheet 42 of each color, and 43Y, 43Y, 42C are applied to the supply roll 43 in synchronization with the conveyance of the recording paper.
3M, 43C to take-up roll 44, 44Y,
Transport to 44M and 44C. As a result, the recording paper is passed through the conveyance path one after another, and each recording section 4
1, 41Y, 41M.

At 41C, to the thermal head 45, 45Y, 4
5J 45C to the ink donor sheet 42, 42
Transfer Y, 42M, and 42C inks to recording paper.

This allows color recording to be performed by overlapping four colors.

Furthermore, during black and white copying, the ink on the ink donor sheet 42 is transferred to the recording paper in the recording section 41K by switching the switching plate of the switching section 46 provided between the black recording section 41K and the yellow recording section 41Y. Later, this JP-A-60, which is directly discharged along the conveyance path B.
By using the configuration described in Japanese Patent No. 85675, each color is transferred continuously, so the copying speed is 1 minute per minute.
This results in a relatively high speed for a color copying machine.

However, even in color copying machines, when making monochrome copies, copying speeds and productivity comparable to those of conventional monochrome-only copying machines are still required. However, since transfer type thermal recording uses heat transfer,
There is a problem that the image forming speed is slow and the black and white copying speed is slower than the xerographic copying speed.

Next, problems when using transfer type thermal recording for color copying will be discussed.

The most important point in color copying is faithful color reproduction, and for this purpose, it is necessary to perform faithful pixel reproduction and record halftone patterns without relying on heat accumulation in the thermal head.

In order to eliminate the effects of heat accumulation, the present inventors proposed a thermal head drive device as described in Japanese Patent Application Laid-Open No. 167577/1983.

FIG. 5 shows a block diagram of the thermal head driving device described in the publication. This calculates the energy to be applied to the heating resistor corresponding to the pixel to be printed by referring to the pixel pattern around the pixel to be printed, and then adjusts the energy to be applied to the heating resistor according to the calculation result. It is something to control.

In the figure, reference numeral 51 denotes a peripheral pattern extraction circuit, which extracts patterns for a group of pixels around the pixel of interest for which applied energy is to be calculated at the present time, based on the image signal Sv, and generates reference data R, , R2. obtain. The reference data R2 corresponds to pixels ■ to [phase] shown in FIG.
The reference data R2 corresponds to pixels ■ to ■. In addition,■
The pixel indicated by is the pixel of interest.

The extracted reference data R,,R, are the first and second R
OM52.53. These first and second ROMs 52 and 53 determine the heat storage near the heating element from the peripheral pattern. That is, the first ROM 52 predicts the future printing state based on the reference data R1 and outputs future discrimination information FI.

In addition, in the second ROM 53, the heat storage state of the unit heating element corresponding to the pixel of interest, that is, heating resistor heat storage information x1 is determined based on the reference data R2. And a correction energy calculator (indicated by TIA calculator in the figure)
In step 54, the corrected energy T1A is calculated. This correction energy TIA corresponds to the width of the pulse applied to the thermal head. Furthermore, the heating resistor heat storage information X is supplied to the third ROM 55, and the degree to which this contributes to heat storage in the heat insulating layer of the thermal head, etc., is determined.
Heat storage contribution information XiA is calculated.

Heat storage information calculator for heat insulation layer, etc. (indicated by B+calculator in the diagram) 5
6 calculates the heat storage information Bl of the heat insulating layer etc. using the heat storage contribution information x, A and the heat history information B1-1 of the heat insulating layer etc.

Here, the thermal history information 81-1 for the heat insulating layer, etc. is information obtained by delaying the heat storage information B+ for the heat insulating layer, etc. by one line by the RAM 57.

The heat storage information B1 such as the heat insulation layer is supplied to the fourth ROM 58 and converted into pulse width information BiA according to the energy. This pulse width information BIA is used in an applied energy calculator (indicated by TIB calculator in the figure) 59 to correct the correction energies T and A together with the resistance value information R8 indicating the variation in the resistance value of the heating element. Applied energy Ti
B is now being sought.

According to this device, the applied energy is corrected taking into consideration the influence of the heat insulating layer of the thermal head, etc., so that accurate correction is possible. Therefore, there is an effect that even if the recording or displaying operation speeds up, halftones can be accurately expressed.

However, when this device is used to drive a thermal head in a higher speed range, it is necessary to increase the area of interest in the peripheral pattern of the pixel of interest, resulting in an increase in hardware.

On the other hand, line images such as characters are required not to be blurred or crushed, and even if the sizes of the printed dots formed at that time vary, this does not constitute an image quality defect.

From the point of view of controlling the thermal head, consideration of the printing history of the dot of interest can be sufficiently effective in preventing dots from becoming blurred or crushed.

Therefore, in Japanese Patent Application No. 61-138325, the present inventor has proposed a thermal head driving device which has a simple structure, can prevent the effects of heat accumulation to some extent, and can perform recording without chipping or crushing.

FIG. 6 shows its block diagram.

In the figure, 61 is data D of the pixel of interest from the image signal Sv.
1 and its adjacent pixel data Di+1. This is a shift register that stores o and -1. The energy determining unit 62 stores the data Di,..., Di, D=, and the RAM 63.
From the applied energy information Eo of the previous line from
The current applied energy information E is determined. Specifically, when print data is continuously applied to the same heating element, applied energy that promotes heat storage and applied energy that suppresses heat storage are applied alternately, and the amount of this applied energy is applied to adjacent pixels. depend on the print data. In FIG. 2, the pixel of interest is the pixel indicated by ``■'', and the adjacent pixels are the pixels ``■'' and ``■'' surrounded by broken lines.

RAM63 uses the position of each heating element of the thermal head as an address and stores the previous applied energy information E. is used as data.

In this way, in the device shown in FIG. 6, the applied energy information B of the previous line has the greatest influence of heat accumulation on the pixel of interest. and print data Di+l+Dl- of adjacent pixels
1, the applied energy information E to the pixel of interest is controlled. Therefore, when print data is continuously applied to the same heating element, the applied energy that promotes heat storage and the applied energy that suppresses heat storage are applied alternately and depend on the print data of adjacent pixels.

Therefore, according to the apparatus shown in Fig. 6, for line images, fluctuations in heat accumulation in the thermal head are suppressed even during high-speed printing of 1 ms/line, so image quality does not deteriorate and reproducibility is improved. In good condition. However, regarding halftone images, the dot pattern required to express the halftone image becomes uneven, resulting in poor reproducibility.

The present invention has been devised to solve the above-mentioned problems, and when the focus is on halftone dot images, processing is focused on dot reproduction, and when the focus is on character images, processing is performed with emphasis on reproduction of dots. The purpose is to increase the recording speed by processing with emphasis on line image reproduction.

[Means for solving problems]

In order to achieve the above object, the present invention provides a thermal head drive device that calculates energy to be applied to a heating resistor corresponding to a pixel to be printed by referring to a pattern of pixels around a pixel to be printed. The present invention is characterized in that it is provided with an energy calculation unit that performs two types of energy calculations, an energy calculation for image quality and an energy calculation for high speed, and a means for switching each of the energy calculations according to a mode switching signal.

The energy calculation unit is provided with a calculation unit that is shared during energy calculation for high image quality and energy calculation for high speed,
By switching the calculation parameters in the calculation unit according to the mode switching signal, it is possible to switch between the energy calculation for high image quality and the energy calculation for high speed.

[Effect]

In the present invention, in a thermal head driving device that controls the energy applied to the heating resistor by calculation from the pattern of surrounding pixels, the type of calculation is switched depending on the type of image to be output. For example, when the image to be output is a halftone image, energy calculation for high image quality is performed, and the halftone dot pattern required to express the halftone image becomes uniform, improving the image reproducibility. Get better. Furthermore, when the image to be output is a line drawing such as a character, high-speed energy calculation is performed, and an image without blur or blur is output at high speed.

Furthermore, the energy calculation for high image quality and the energy calculation for high speed can be performed by a common calculation unit, and in this case, each energy calculation is switched by switching the parameters of the calculation unit using a mode switching signal.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 1 shows a schematic configuration diagram for explaining the present invention.

In this embodiment, a high-quality energy calculation unit 1 with high halftone dot reproducibility and a high-speed energy calculation unit 2 with emphasis on character reproducibility are provided. Then, for example, the switches 3a, 3b, 3c, and 3d are switched by the mode switching signals S and 1 manually inputted from the outside, and either one of the two energy calculation units 1.2 is selected, and the output voltage is adjusted according to the manually inputted image signal Sv. The heat storage calculation algorithm has been changed to control the pulses that excite the thermal head.

That is, in the high image quality mode, switches 3a and 3b are turned on as shown in the figure, and switch 3c is turned on.

3d is turned off and heat storage calculation for high image quality is performed.

In addition, when in high-speed mode, switches 3a, 3b,
3c.

The state of 3d is reversed, and heat storage calculation for high speed is performed.

However, each energy calculation section 1.
2 would increase the scale of the hardware and increase the cost, so it is desirable to share the circuit as described below.

FIG. 2 shows pixels 1 to 2 of the peripheral pattern referred to in the high-quality driving device shown in FIG. 5, and pixels 2 of the peripheral pattern referred to in the high-speed driving device shown in FIG. , ■. In addition, in the figure,
1-3. . . . ~1+2 indicates the order of each line.

As can be seen from Fig. 2, the areas of peripheral pixels of interest ■ and ■ in the method of performing thermal control with a simple configuration shown in Fig. 6 are different from those of the method of performing thermal control with higher precision shown in Fig. 5. It is equal to or narrower than the area of peripheral pixels of interest ■ to ■.

Therefore, the high image quality energy calculation section 1 and the high speed energy calculation section 2 can share a circuit for extracting peripheral patterns. Furthermore, it can be seen that the surroundings of the thermal insulation layer etc. heat storage information calculator 56 in FIG. 5, which corresponds to the energy calculator 1 for high image quality, have the same configuration as the energy determining unit 62, RAM 63, etc. shown in FIG. 6. .

This is done by manually inputting peripheral pattern information instead of the heat storage contribution information XIA to the thermal insulation layer etc. heat storage information calculation unit 56 composed of ROM etc. in FIG. The content of is switched by the mode switching signal Sx, and the output of the thermal insulation layer etc. heat storage information calculator 56 is used as the applied energy Tll1 to the thermal head drive circuit 6.
4 means that both can be realized very efficiently as hardware.

This will be explained in detail with reference to FIG. Note that parts corresponding to those in FIG. 5 are given the same reference numerals.

In the figure, 51 indicates a peripheral pattern extraction circuit as a whole. After the image signal Sv is launched in the latch 31, it is sent to the 1+1 line memory 32. in the line memory group 32.
, , is written to. 1+1 line memory 32□
+1 is a memory for storing future image signals for one line. This i+1 line memo 1J32i...
The image signal pushed out is latched by the latch 33, and
i+ in the line memory 32 and the shift register group 34
1 line shift register 34. +.

is input. The 1-line memory 32 is a memory that stores the image signal of the line on which recording is currently being performed. The image signal pushed out from the 1-line memory 32+ is latched by the latch 33, and is latched by the 1-1 line memory 32i, 1-line shift register 34. is input. Thereafter, image signals are transferred in the same way, and finally, the memo 'J32 for lines 1-3 in the line memory group 32 is transferred.
The image signal pushed out from =3 is latched by the latch 33 and input to the 1-3 line shift register 34.3.

On the other hand, the image signal S latched by the previous latch 31 is i
It is also input to the +2 line shift register 34i-2. Therefore, each shift register 34i, 2 to 34i-3
are respectively l+2. . . , image signals for six lines of the l-3 line are input.

Each shift register 34I+2 to 34+-3 is a five-stage shift register, and the 1+2 line shift register 34. The reference data output from the third stage of +2 is supplied to the input terminal of the first ROM 52.

Further, parallel reference data output from the second to fourth stages of the l+1 line shift register 34i+ is supplied to input terminals AO to A2 of the first ROM 52. In this way, the output of the location corresponding to pixel O-[phase] shown in FIG. 2 becomes a 4-bit address for the first ROM 52.

Similarly, the outputs of the portions corresponding to pixels 1-0 are supplied to the input terminals AO-AIO of the second ROM 53, forming an 11-bit address.

In this embodiment, the one-line shift register 341
The parallel reference data D+-1+ DI+ Di-+ outputted from the second to fourth stages of the first selector 35
is supplied to input terminal B of. In addition, the first selector 3
The heat storage contribution information XiA, which is the output of the third ROM 2S, is supplied to the input terminal A of No. 5.

The first selector 35 receives a mode switching signal S. In response to the,
Heat storage contribution information xIA from the third ROM 2S or peripheral pattern reference data D from the shift register group 34
, .

Further, the second selector 36 selects either the output of the applied energy calculator 59 or the applied energy information E from the thermal insulation layer etc. heat storage information calculator 56 in accordance with the mode switching signal S8, and selects the final The applied energy is output as TiB.

Now, when the circuit shown in FIG. 3 is operated as the high image quality energy calculating section 1 shown in FIG. 1, the mode switching signal S is used. , the first and second selectors 35 and 36 are switched to the input terminal A side, and the high-speed energy calculation section 2
When operating as
The first and second selectors 35 and 36 are switched to the input terminal B side. Further, in conjunction with this switching, the contents of the ROM table of the thermal insulation layer etc. heat storage information calculator 56, that is, the calculation parameters, are switched by the mode switching signal SH.

Therefore, in the high image quality mode, the heat storage contribution information XIA based on the pixels 1 to [phase] from the third ROM 55 is supplied to the thermal insulation layer etc. heat storage information calculator 56, and in the thermal insulation layer etc. heat storage information calculator 56, the high image quality The calculation is performed based on the calculation parameters for the The thermal insulation layer etc. heat storage information B1 from the thermal insulation layer etc. heat storage information calculator 56 is temporarily stored in the RAM 57 to become thermal insulation layer etc. thermal history information B1-1, and is passed through the fourth ROM 58 to pulse width information. BaA, and the applied energy calculation unit 59 calculates the correction energy T.
A predetermined calculation is performed with IA, and the final applied energy TiE is outputted via the second selector 36. That is, in the high image quality mode, the circuit operates similarly to the circuit shown in FIG. 5.

Further, in the high speed mode, reference data D, from the shift register group 34. l+D+, Di-+ are supplied to the thermal insulation layer etc. heat storage information calculator 56, where the calculation is performed based on high speed calculation parameters, and applied energy information IE is obtained. . In the circuit shown in FIG. 3, the applied energy information ε from the thermal insulation layer etc. heat storage information calculator 56 includes applied energy information E and updated energy information EN shown in FIG.

The output corresponding to the updated energy information is temporarily stored in the RAM 57 and becomes the applied energy information E of the previous line. At the same time, the output corresponding to the applied energy information E is
Directly applied energy TiB via the second selector 36
is output as That is, a pulse having a width corresponding to the amount of correction is applied to the thermal head.

At this time, the table of the heat storage information calculator 56 for heat insulation layer, etc. is as follows:
For example, as shown in Table 1.

(Left below) Table 1 In Table 1, Snake+, E2. E3 indicates the applied energy that advances the heat storage of the unit heating element, and E3
Defined as +-[]+/η [12-(Q+/η)10L B3-(1)I/η)+2L. Further, EN indicates updated energy information. However, shi indicates the printing energy that promotes heat storage in the unit heating element, η indicates the thermal efficiency, and L indicates the energy flowing from the pixel of interest to the adjacent pixel. Note that the printing energy L means the energy used for printing the pixel of interest.

In addition, IEIRI E2RI E3RI E4a indicates the applied energy that reduces the heat storage of the unit heating element, and is defined as [i+t+-02/η E2R-(02/η)+LE3R-(Ω2/η)+2L . However, Q2 indicates printing energy that compensates for the progress of heat storage.

Applied energy information E is a 2-bit signal (0, 0) (
Previous applied energy information 8° and data D1°I+D with three types of states expressed as 0, 1) and (1, 0)
Determined by I+DI-1.

For example, the previous applied energy information E. is (1, 1), and the data D, . Assuming that I+ Dt+ ol-1 are all 1, the applied energy E becomes IE, R, and the updated energy information B8 becomes (1, 0).
is output.

In this way, in the high-speed mode, the applied energy information E of the previous line has the greatest influence of heat accumulation on the pixel of interest.

The applied energy information E to the pixel of interest is controlled according to the print data Dl+1+ot-1 of the adjacent pixel. Therefore, when print data is continuously applied to the same heating element, the applied energy that promotes heat storage and the applied energy that suppresses heat storage are applied alternately and depend on the print data of adjacent pixels. That is,
The operation is similar to that of the circuit shown in FIG. 6.

As described above, according to this embodiment, the operation mode of the circuit can be switched between a high-quality mode suitable for halftone images and a high-speed mode suitable for line images using the mode switching signal SM.

Furthermore, by applying this drive device to the color copying machine shown in Fig. 4, the speed of black and white copying can be increased to at least twice the speed of color copying, which is a problem especially when thermal recording is applied to a copying machine. The poor productivity of black and white copying can be improved. That is, since black and white originals are often composed of line images such as characters, when copying a black and white original with a color copying device, the copying speed can be increased by operating the circuit in high speed mode.

〔Effect of the invention〕

As described above, in the present invention, two types of energy calculation sections, a high image quality energy calculation section and a high speed energy calculation section, are provided, and the calculations are switched depending on the nature of the image to be output. As a result, for a halftone image, the dots of the halftone dot pattern necessary to express the halftone image become uniform, so that the reproducibility of halftones is improved.

Furthermore, for line images such as characters, images that are not blurred or crushed can be outputted at high speed, and the recording speed can be increased. Note that even if the sizes of printed dots formed during high-speed output vary, this does not cause an image quality defect in line images. Therefore, according to the present invention, it is possible to achieve both high image quality and high speed when outputting an image.

In addition, if a part of the energy calculation section for high image quality and the energy calculation section for high speed are shared, and the energy calculation for high image quality and the energy calculation for high speed are switched by switching the calculation parameters, the circuit configuration can be simplified. Both energy calculations can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the basic configuration of the thermal head driving device according to the present invention, FIG. 2 is an explanatory diagram showing areas of interest during energy calculation for high image quality and energy calculation for high speed, and FIG. The figure is a block diagram showing an embodiment of the thermal head drive device according to the present invention, Figure 4 is a schematic sectional view of a color copying machine using thermal transfer, and Figure 5 is a conventional thermal head drive that performs energy calculation for high image quality. FIG. 6 is a block diagram of a previously proposed thermal head driving device that performs high-speed energy calculation. 3a, 3b, 3c, 3d: Switch 32 Second line memory 34: Shift register group 35; First selector 36: Second selector 51; Peripheral pattern extraction circuit Patent applicant: Fuji Xerox Co., Ltd.
Masato Kobori (and 2 others)
Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. In a thermal head driving device that calculates energy to be applied to a heating resistor corresponding to a pixel to be printed by referring to a pattern of pixels around a pixel to be printed, an energy source for high image quality is provided. A thermal head drive device, comprising: an energy calculation section that performs two types of energy calculations, a calculation and a high-speed energy calculation, and means for switching between the energy calculations in accordance with a mode switching signal. 2. The energy calculation section is provided with a calculation unit that is used in common for high image quality energy calculation and high speed energy calculation, and the high image quality is achieved by switching the calculation parameters in the calculation unit according to the mode switching signal. 2. The thermal head drive device according to claim 1, wherein the thermal head drive device switches between high-speed energy calculation and high-speed energy calculation.