JP2013014067A - Image forming apparatus, and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an image quality of a designated area while suppressing radiation noise when printing an image arranged in the designated area by a sublimation printer.SOLUTION: A driver IC 502 for increasing the speed of a transfer clock is indexed on the basis of coordinates of a printing area (designated area). A signal having a period of a clock signal CLK increased in speed by causing the period to be 1/m times a period N of a clock signal CLK in a non-printing area is output to the driver IC 502.

Description

  The present invention relates to an image forming apparatus and a control method for the image forming apparatus, and in particular, while selectively driving a plurality of heating resistors arranged in the main scanning direction, the sheet is conveyed in the sub-scanning direction to the sheet. It is suitable for use in forming an image.

In recent years, with the advance of image input devices such as digital cameras, digital video cameras, and scanners, sublimation printers have attracted attention as image input means for printing out input images.
A sublimation printer uses a heat-sensitive paper as a printing paper and conveys the paper in the sub-scanning direction while selectively driving a plurality of heating resistors (thermal recording heads) arranged in the main scanning direction. Dot-line printing is performed on the paper.

In general inkjet printers that are currently popular, only the binary selection of whether or not to drop a droplet causes a small droplet to land on the paper, and by using a technique such as error diffusion, the apparent resolution and Gradation is obtained.
On the other hand, in a sublimation printer, the controllable heat value in one pixel can be easily changed, so that a large gradation can be obtained for one pixel, which is smoother than that of an ink jet printer. High-quality images can be obtained.

Sublimation-type printers are also remarkably improved in the performance of thermal recording heads and the quality of paper materials, and it is becoming possible to obtain image quality that is not inferior to silver halide photographs in the quality of printed images. In particular, sublimation printers are strong for printing photographs that require smooth gradation such as natural images and human images, and an increasing number of users use sublimation printers as replacements for commercial DPE terminals.
Nowadays, there is an increasing number of users who use the printed photos one by one instead of printing the stored photos one by one (so-called photo book printing). It is attracting attention as a new way to use printers.

Photo books are often printed on the premise of distribution, and users demand high print quality for their printed materials.
As a technique for improving the image quality of a printer, there is a technique disclosed in Patent Document 1. According to such a technique, in an ink jet printer, the head driving conditions such as a transfer clock are increased in accordance with the amount of ink applied on the printed matter, and optimum thermal transfer conditions are given to each portion.

JP 2005-313439 A

FIG. 12 is a diagram illustrating an example of a layout in photobook printing.
As shown in FIG. 12, in photobook printing, the user often prints by arranging (laying out) an image 122 taken by himself / herself on a border (frame 121) prepared in advance. There are two methods for improving the image quality of an image arranged in such a specific designated area.

The first method is a method in which image data larger than normal printing is once expanded on SDRAM and then sent to a recording head using a head control ASIC (Application Specific Integrated Circuit). In this method, the number of gradations per line is increased by doubling the image data input to the head control ASIC. In general, a sublimation printer has many line scanning methods, and by sending data more than double in the sub-scanning direction, the gradation value per line on the recording paper can be increased.
However, this method requires larger image data when printing with higher image quality. This contributes to an increase in the SDRAM capacity in the printer and increases the cost of the printer product.

The second method is a method of shortening a transfer clock that is a control signal of the recording head and a data cycle.
A method of shortening the cycle of the control signal is widely used in printers that perform printing while reciprocating a recording head horizontally such as an ink jet printer. By doubling the number of data output from the recording head, the number of dots printed on the recording paper is increased, and the gradation value per line is increased. The image data is expanded in the head control ASIC and output with a clock faster than usual.

Although this method can achieve high image quality without increasing image data, it is a highly convenient method, but there are some problems.
First, if the data transfer rate is unconditionally increased, the system clock frequency increases, which makes it difficult to take measures against noise.

  As described above, the sublimation type printer is generally a line scanning printer. Therefore, the recording head of the sublimation type printer has a configuration in which the heating resistors for one line are subdivided and controlled by a plurality of driver ICs. For example, in the case of a recording head having a 4-inch 1280-dot heating resistor, one driver IC controls ON / OFF of the heating resistors for 128 heating resistors. As disclosed in Patent Document 1, the method of raising the transfer clock to the recording head can perform processing only in units of driver ICs. Therefore, when the driver IC controls the heat generating photosensitive member in the region straddling the end portion of the designated region in the main scanning direction, the following problem occurs.

FIG. 13 is a diagram illustrating the adverse effects that occur on the printed matter when the heat-generating photoconductor is controlled in units of driver ICs.
As described above, a photo book often uses a frame with a fixed gradation and an image layout. In the example illustrated in FIG. 13, the driver IC 1 and the driver ICs (driver ICs 2 to 4 etc.) other than the driver IC 10 are driver ICs that speed up the transfer clock for the recording head 131. Then, the driver IC 2 controls a region that straddles the end of the designated region (image portion) 132 in the main scanning direction. Therefore, not only the designated area (image portion) 132 but also the area printed by the driver IC 2 in the frame 133 is improved in image quality. On the other hand, the areas 135a and 135b subject to control by the driver ICs 1 and 10 are equal resolution areas. Therefore, uneven printing occurs in the regions 136a and 136b at the boundary between the region 134 and the regions 135a and 135b. Therefore, the quality of the printed material is deteriorated.
The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the image quality of a designated area while suppressing radiation noise when printing an image arranged in the designated area with a sublimation printer. And

  The image forming apparatus according to the present invention includes a plurality of drivers for controlling the operation of the heating resistors in units of the heating resistors arranged in the main scanning direction and the plurality of heating resistors included in the heating resistors. And an image forming apparatus that scans the recording head in the sub-scanning direction to form an image on recording paper. The head control circuit derives a driver circuit for forming an image in the designated area from the plurality of driver circuits based on the position of the designated area in the image to be formed on the recording paper. And a transmission cycle of image data transmitted to a driver circuit different from the driver circuit in which the transmission cycle of image data transmitted to the driver circuit for forming an image in the designated area To be shorter than, and having a means for transmitting image data to each of the plurality of driver circuits.

According to the present invention, a driver circuit for generating an image in a specified area is determined, and the image data transmitted to a driver circuit different from the driver circuit is transmitted with a transmission cycle of image data transmitted to the driver circuit. Shorter than the transmission cycle. Therefore, when printing an image arranged in the designated area with the sublimation printer, it is possible to improve the image quality of the designated area while suppressing radiation noise.
According to another feature of the present invention, the gradation value of a region different from the designated region is relatively low with respect to a driver circuit for forming an image in a region across the designated region. Image data having a relatively high gradation value is transmitted. Therefore, it is possible to suppress the occurrence of uneven printing at the boundary of the designated area.

It is a figure which shows the whole structure of a sublimation type printer. It is a figure which shows the structure of the recording head and head control ASIC of a comparison technique. It is a figure which shows an example of the internal structure of the driver IC of a comparison technique. It is a time chart which shows the operation timing of each signal of a comparison technique. FIG. 2 is a diagram illustrating a configuration of a recording head and a head control ASIC according to the first embodiment. 5 is a flowchart for describing printing processing according to the first embodiment. FIG. 4 is a diagram illustrating a positional relationship between a driver IC and a designated area in a recording sheet. It is a time chart which shows the operation timing of each signal of a 1st embodiment. It is a figure which shows the structure of the recording head and head control ASIC of 2nd Embodiment. 10 is a flowchart illustrating print processing according to the second embodiment. It is a time chart which shows the operation timing of each signal of a 2nd embodiment. It is a figure which shows the layout in photobook printing. It is a figure which shows the harmful effect which arises in printed matter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Configuration of sublimation printer of this embodiment)
FIG. 1 is a diagram illustrating an example of an overall configuration of a sublimation printer 100 for printing print data.
In FIG. 1, a CPU 14 controls system control and arithmetic processing of a sublimation printer 100 that is an example of an image forming apparatus. The image processing unit 15 includes an image processing engine that processes image data sent from an external device such as a camera and image data acquired from a storage medium such as an SD card (SD memory card). The image processing unit 15 performs various image processing such as decompression on “image data transmitted from a camera or the like, or image data acquired from an SD card or the like” to generate image data for printing.

The FLASHROM 19 stores a system control program for the sublimation printer 100 and the like. The SDRAM 20 is a storage medium used for temporary storage of image data and data processing work. The SD card 21 is a storage medium for storing data files and the like.
The card connector 22 is for attaching the SD card 21 to the sublimation printer 100. The LCD 23 displays images and operation menus. The LCD driver 24 is for driving the LCD 23.

The communication control unit 16 controls communication with an external device (such as a camera) connected to the sublimation printer 100. The operation unit 17 is a part where an instruction is input by the user. The head control ASIC 13 (thermal head ASIC) converts the image data for printing generated by the image processing unit 15 into an electrical signal and outputs it to the recording head 12 (thermal head). The recording head 12 converts the electrical signal output from the head control ASIC 13 into thermal energy, and performs recording on photographic paper. The head temperature sensor 18 and the environmental temperature sensor 11 measure the temperature of the recording head 12 and the environmental temperature around the sublimation printer 100, respectively. The ink ribbon remaining amount meter 25 detects the remaining amount of the ink ribbon.
The configuration shown in FIG. 1 is a general system configuration of a sublimation printer, and the sublimation printer 100 having the same configuration shown in FIG. 1 is used in both the first and second embodiments described later. be able to.

(Configuration compared to this embodiment)
First, the structure compared with this embodiment is demonstrated.
FIG. 2 is a diagram illustrating an example of a circuit configuration of the recording head 12 and the head control ASIC 13.
In FIG. 2, the recording head 12 includes a heating resistor group 201 and a plurality of driver ICs 202 that are examples of driver circuits. Each transmission line for transmitting an output signal from the driver IC 202 is connected to each heating resistor of the heating resistor group 201 one by one. In the sublimation type printer, an image is formed on a recording sheet by the recording head 12 scanning in the sub-scanning direction while selectively driving the heating resistor. The heating resistors are arranged in the main scanning direction. Normally, a driver IC 202 is assigned to about 100 heat generating resistors in one unit, and these driver ICs 202 control ON / OFF of each heat generating resistor assigned to itself.

  The head control ASIC 13 is an example of a head control circuit, decodes the data D received from the CPU 14, and generates a signal for the recording head 12. There are three types of signals for the recording head 12: serial data, latch signals, and clock signals. Serial data is separately input to each driver IC 202, and a clock signal and a latch signal are commonly used by each driver IC 202. The driver IC 202 sends data to the heating resistor to be energized using the clock signal and serial data. At this time, the driver IC 202 determines data to be transmitted to the heating resistor based on the latch signal, and causes the heating resistor to generate heat in units of the driver IC 202.

FIG. 3 is a diagram illustrating an example of the internal configuration of the driver IC 202. FIG. 4 is a time chart showing an example of the operation timing of each signal transferred from the head control ASIC 13 to the recording head 12.
In FIG. 3, the driver IC 202 includes one shift register 301 for each heating resistor included in the recording head 12. Each shift register 301 receives “serial data SD, latch signal LCH, and clock signal CLK” transmitted from the head control ASIC 13.
As shown in FIG. 4, serial data SD is output from the head control ASIC 13 in synchronization with a clock signal CLK having a fixed period N. Serial data SD output from the head control ASIC 13 is taken into the shift register 301 in the driver IC 202 one by one. The serial data SD stored in each shift register 301 is output to the heating resistor in the recording head 12 as head data HD by the latch signal LCH.

(First embodiment)
Next, a first embodiment of the present invention will be described.
FIG. 5 is a diagram illustrating an example of a circuit configuration of the recording head 12 and the head control ASIC 13.
In FIG. 5, the recording head 12 includes a heating resistor group 501 and a plurality of driver ICs 502. One transmission line for transmitting each output signal of the driver IC 502 is connected to each heating resistor of the heating resistor group 501 one by one. Normally, one driver IC 502 is assigned in units of about 100 heating resistors, and these driver ICs 502 control ON / OFF of each heating resistor assigned to itself.

The head control ASIC 13 decodes the data D received from the CPU 14 and generates a signal for the recording head 12. Serial signals, latch signals, and clock signals are output from the head control ASIC 13 to the recording head 12 as signals for the recording head 12.
In this embodiment, the serial data SD, the clock signal CLK, and the latch signal LCH are separate signals for each driver IC 502 and are individually input to each driver IC 502 in the recording head 12. The driver IC 502 uses the clock signal CLK and the serial data SD to send data to the heating resistor that is energized. At this time, the driver IC 502 determines data to be transmitted to the heating resistor based on the latch signal LCH, and causes the heating resistor to generate heat in units of the driver IC 502.
Unlike the configuration of the sublimation printer compared to the above-described embodiment, in this embodiment, the head control ASIC 13 individually outputs the latch signal LCH and the clock signal CLK for each driver IC 502. As a result, it is possible to select a control signal of the driver IC 502 corresponding to the region where resolution is to be increased, and to speed up the transfer of the signal output to the driver IC 502.

Next, an example of printing processing in the sublimation printer 100 of this embodiment will be described with reference to the flowchart of FIG.
First, the head control ASIC 13 inputs the horizontal coordinate and the vertical coordinate (number of lines) of a designated area (for example, a designated area in photobook printing) for high resolution from the CPU 14 (step S1).
Next, the head control ASIC 13 derives the number of the driver IC 502 that speeds up the transfer clock from the coordinate value input in step S1 (step S2).
Next, the head control ASIC 13 determines whether or not there is a driver IC 502 that controls printing of an area that straddles a designated area for high resolution (step S3). FIG. 7 is a diagram showing an example of the positional relationship between the driver IC 502 and the designated area in the recording paper. Specifically, FIG. 7A is a diagram illustrating an example of the positional relationship between the driver IC 502 and the designated area in the recording paper when there is no driver IC 502 that controls printing of the area across the designated area. FIG. 7B is a diagram showing an example of the positional relationship between the driver IC 502 and the designated area in the recording paper when there is a driver IC 502 that controls printing of the area across the designated area. In FIG. 7, the paper feeding direction of the recording paper 701 is the direction from the top to the bottom of the paper (see the arrow shown in FIG. 7).
In the example shown in FIG. 7B, the driver ICs 502a and 502d are driver ICs 502 that control printing of an area across the designated area 702.

As a result of the determination in step S3, if it is determined that there is a driver IC 502 that controls printing of an area that straddles the specified area, the process proceeds to step S4. Then, the head control ASIC 13 receives image data for one line (for 1H) from the CPU 14 (step S4).
Next, the head control ASIC 13 performs a clip process in which the gradation value outside the designated area 702 is made lower (smaller) than the gradation value in the designated area 702 (step S5). For example, it is assumed that the period of the clock signal in the printing area (designated area) that is increased in speed with respect to the period N of the clock signal CLK in the non-printing area is N / m (m is a positive integer). In this case, the head control ASIC 13 performs a process of multiplying the gradation value outside the designated area 702 by 1 / m among the gradation values of the image data for one line held in step S4. On the other hand, the gradation value of the designated area 702 is not changed.

Next, the head control ASIC 13 speeds up the clock signal CLK and the latch signal LCH for the driver IC 502 having the number derived in step S2 (step S6). On the other hand, the clock signal CLK and the latch signal LCH for the driver IC 502 other than the numbers derived in step S2 are not accelerated. As a result, the cycle of the clock signal CLK and the latch signal LCH for the driver IC 502 with the number derived in step S2 is relatively shorter than the cycle of the clock signal CLK and the latch signal LCH for the other driver ICs 502. Therefore, the cycle of the serial data SD transferred to the driver IC 502 having the number derived in step S2 is also relatively shorter than the cycle of the serial data SD for the other driver ICs 502.
Next, the driver IC 502 performs printing for one line based on “serial data SD, latch signal LCH, and clock signal CLK” output from the head control ASIC 13 (step S7).
Then, the head control ASIC 13 determines whether or not printing for one page has been completed (step S8). As a result of this determination, when printing for one page is completed, the process proceeds to printing for the next page. On the other hand, if the printing for one page is not completed, the process returns to step S4, and the process for the next line is performed.

If it is determined in step S3 that there is no driver IC 502 that controls the printing of the area across the specified area, the process proceeds to step S9. The head control ASIC 13 receives image data for one line (for 1H) from the CPU 14 (step S9).
Next, the head control ASIC 13 increases the speed of the clock signal CLK and the latch signal LCH for the driver IC 502 having the number derived in step S2 (step S10).

Next, the driver IC 502 performs printing for one line based on “serial data SD, latch signal LCH, and clock signal CLK” output from the head control ASIC 13 (step S11).
Then, the head control ASIC 13 determines whether or not printing for one page has been completed (step S12). As a result of this determination, when printing for one page is completed, the process proceeds to printing for the next page. On the other hand, if the printing for one page is not completed, the process returns to step S9, and the process for the next line is performed.

  FIG. 8 is a time chart showing an example of the operation timing of each signal transferred from the head control ASIC 13 to the recording head 12. The operation timing shown in FIG. 8 corresponds to the operation timing of each signal in step S7 or S11 in FIG. In FIG. 8, it is assumed that the driver IC 502 having the number derived in step S2 is the driver IC 2 and the driver IC 3. In this case, a signal obtained by increasing the cycle of the clock signal CLK to 1 / m times the cycle N of the clock signal CLK in the non-printing area is output to the driver IC2 and the driver IC3. As a result, “clock signal CLK, serial data SD, and latch signal LCH” each having a cycle of N / m are output.

As described above, in the present embodiment, the driver IC 502 that speeds up the transfer clock is determined from the coordinates of the print area (designated area of the image formed on the recording paper). Then, the driver IC 502 outputs a signal in which the cycle of the clock signal CLK is increased to 1 / m times the cycle N of the clock signal CLK in the non-printing area. Therefore, it is possible to suppress the increase of the system clock frequency as much as possible by unconditionally increasing the data transfer rate (shortening the transmission cycle), and to easily take measures against noise. Can do. Therefore, it is possible to improve the image quality of the designated area while suppressing radiation noise.
In this embodiment, if there is a driver IC 502 that controls printing of an area that crosses the designated area for high resolution, the floor of the area outside the designated area 702 among the areas drawn by the driver IC 502 is displayed. The key value was dropped. Therefore, it is possible to suppress as much as possible that the area other than the designated area is improved in image quality, or that uneven printing occurs at the boundary between the designated area and the other areas.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
FIG. 9 is a diagram illustrating an example of a circuit configuration of the recording head 12 and the head control ASIC 13.
In FIG. 9, the recording head 12 includes a heating resistor group 901 and a plurality of driver ICs 902. One transmission line for transmitting each output signal of the driver IC 902 is connected to each heating resistor of the heating resistor group 901 one by one. Normally, one driver IC 902 is assigned to a unit of about 100 heating resistors, and these driver ICs 902IC control ON / OFF of each heating resistor assigned to itself.

The head control ASIC 13 decodes the data D received from the CPU 14 and generates a signal for the recording head 12. As signals for the recording head 12, serial data SD, latch signals LCH 1 and LCH 2, and clock signals CLK 1 and CLK 2 are output from the head control ASIC 13 to the recording head 12.
In the present embodiment, the serial data SD is a separate signal for each driver IC 902 and is individually input to each driver IC 902 in the recording head 12. On the other hand, one clock signal CLK1, CLK2 and one latch signal LCH1, LCH2 are prepared for high speed and constant speed, respectively, and distributed from the selector 903 to each driver IC 902. The selector 903 determines a distribution destination of the clock signals CLK1 and CLK2 and the latch signals LCH1 and LCH2 based on a selection signal (not shown). The driver IC 902 uses the clock signal CLK and the serial data SD to send data to the heating resistor that is energized. At this time, the driver IC 902 determines data to be transmitted to the heating resistor based on the latch signal LCH, and causes the heating resistor to generate heat in units of the driver IC 902.

  Unlike the configuration of the sublimation printer compared to the above-described embodiment, in this embodiment, the head control ASIC 13 has two transmission lines for the latch signal LCH and the clock signal CLK. One transmission line outputs a latch signal LCH and a clock CLK that are relatively faster than the other transmission line. In this embodiment, a selector 903 is provided outside the head control ASIC 13 so that one of the two control signals can be selected and output to each driver IC 902. As a result, it is possible to select the control signal of the driver IC 902 corresponding to the designated area where the resolution is to be increased, and to speed up the signal output to the driver IC 902.

Next, an example of print processing in the sublimation printer 100 of this embodiment will be described with reference to the flowchart of FIG.
Since the processes of steps S21 to S25, S30, and S31 are the same as steps S1 to S5, S9, and S10 of FIG. 6, detailed descriptions thereof are omitted.
After the process of step S25 or S31, the CPU 14 determines the driver IC 902 selected by the selector 903 so that the accelerated clock signal CLK is input to the driver IC 902 having the number derived in step S22 (step S26, S26). S31). On the other hand, the CPU 14 determines the driver IC 902 selected by the selector 903 so that the driver IC 902 other than the number derived in step S22 is input with the (normal) clock signal CLK that is not accelerated. The determination of the driver IC 902 is performed by outputting a selection signal (setting value) of the driver IC 902 from the CPU 14 to each selector 903.

Next, the selector 903 outputs the high-speed “clock signal CLK and latch signal LCH” to the driver IC 502 having the number derived in step S22 (steps S27 and S32).
Henceforth, since the process of step S28, S29, S33, S34 is respectively the same as S7, S8, S11, S12 of FIG. 6, those detailed description is abbreviate | omitted.

FIG. 11 is a time chart showing an example of the operation timing of each signal transferred from the head control ASIC 13 to the recording head 12. The operation timing shown in FIG. 11 corresponds to the operation timing of each signal in step S28 or S33 in FIG. In FIG. 11, when the driver ICs 902 having the numbers derived in step S22 are the driver IC2 and the driver IC3, the selector 903 outputs a selection signal (setting value) for selecting the driver IC2 and the driver IC3. The driver IC 2 and the driver IC 3 output a signal obtained by increasing the cycle of the clock signal CLK in the printing region (designated region) to 1 / m times the cycle N of the clock CLK in the non-printing region.
Even if it does as mentioned above, the effect similar to having demonstrated in 1st Embodiment can be acquired.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

(Other examples)
The present invention is also realized by executing the following processing. That is, first, software (computer program) for realizing the functions of the above embodiments is supplied to a system or apparatus via a network or various storage media. Then, the computer (or CPU, MPU, etc.) of the system or apparatus reads and executes the computer program.

  13 Head control ASIC, 501 Heating resistor group, 502 Driver IC

Claims (8)

A group of heating resistors arranged in the main scanning direction;
A recording head comprising a plurality of driver circuits for controlling the operation of the heating resistor in units of the plurality of heating resistors included in the heating resistor group;
A head control circuit for transmitting image data to the driver circuit,
An image forming apparatus that scans the recording head in the sub-scanning direction to form an image on recording paper,
The head control circuit derives a driver circuit for forming an image in the designated area from the plurality of driver circuits based on the position of the designated area of the image to be formed on the recording paper; ,
The plurality of image data so that a transmission cycle of image data transmitted to a driver circuit for forming an image in the designated area is shorter than a transmission cycle of image data transmitted to a driver circuit different from the driver circuit. An image forming apparatus comprising: means for transmitting image data to each of the driver circuits. The head control circuit individually transmits the image data and a clock signal for synchronizing the output of the image data to the plurality of driver circuits,
A clock signal having a relatively short cycle is transmitted to a driver circuit for generating an image in the designated area, and a clock signal having a relatively long cycle is transmitted to a driver circuit different from the driver circuit. The image forming apparatus according to claim 1. A selector for selecting one of the driver circuits;
The head control circuit individually transmits the image data to the plurality of driver circuits, and a clock signal having a relatively short cycle and a cycle as a clock signal for synchronizing the output of the image data. Means for transmitting a relatively long clock signal to the selector;
The selector outputs a clock signal having a relatively short cycle to a driver circuit for generating an image in the designated area, and the cycle is relatively to a driver circuit different from the driver circuit. 2. The image forming apparatus according to claim 1, further comprising means for outputting a long clock signal. The head control circuit determines whether or not the driver circuits for forming an image in an area across the designated area are in the plurality of driver circuits;
For a driver circuit for forming an image in an area that crosses the designated area, image data that has a relatively low gradation value in an area different from the designated area and a relatively high gradation value in the designated area. The image forming apparatus according to claim 1, further comprising a transmission unit. A group of heating resistors arranged in the main scanning direction;
A recording head comprising a plurality of driver circuits for controlling the operation of the heating resistor in units of the plurality of heating resistors included in the heating resistor group;
A head control circuit for transmitting image data to the driver circuit,
A control method of an image forming apparatus that scans the recording head in a sub-scanning direction to form an image on recording paper,
A derivation step of deriving a driver circuit for forming an image in the designated area from the plurality of driver circuits based on the position of the designated area of the image to be formed on the recording paper;
The plurality of image data so that a transmission cycle of image data transmitted to a driver circuit for forming an image in the designated area is shorter than a transmission cycle of image data transmitted to a driver circuit different from the driver circuit. And a transmission step of transmitting the image data to each of the driver circuits. The transmitting step is a step of individually transmitting the image data and a clock signal for synchronizing the output of the image data to the plurality of driver circuits, respectively.
A clock signal having a relatively short cycle is transmitted to a driver circuit for generating an image in the designated area, and a clock signal having a relatively long cycle is transmitted to a driver circuit different from the driver circuit. The method of controlling an image forming apparatus according to claim 5. As a clock signal for synchronizing the output of the image data from the selector that selects one of the driver circuits to the selected driver circuit, a clock signal having a relatively short period and a clock having a relatively long period An output step for outputting any of the signals,
The transmitting step transmits the image data individually to the plurality of driver circuits, and transmits the clock signal having a relatively short period and the clock signal having a relatively long period to the selector. ,
The output step outputs a clock signal having a relatively short cycle to a driver circuit for generating an image in the designated area, and the cycle is relative to a driver circuit different from the driver circuit. 6. The method of controlling an image forming apparatus according to claim 5, wherein a long clock signal is output. A determination step of determining whether or not a driver circuit for forming an image in an area straddling the designated area is in the plurality of driver circuits;
In the transmission step, the gradation value of the area different from the designated area is relatively low and the gradation value of the designated area is relatively low with respect to the driver circuit for forming an image in the area across the designated area. The image forming apparatus control method according to claim 5, wherein high image data is transmitted to the image forming apparatus.

Images