JPH1079842A - Image writer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the image writer which can write an image at double the processing speed, without varying cycles of an image data transfer clock. SOLUTION: A latch part 3 latches input image data divisionally as odd- numbered data and even-numbered data, according to the image data transfer clock sent from an image clock generating part 2 is at a high or low level. An image signal generating part 4 sends one of he odd-numbered and even- numbered data latched by the latch part 3 out, when the image data transfer clock is at the high level and the other data when at the low level. A light source drove control part 5 drives and controls a laser light source 6, according to the alternately sent odd-numbered and even-numbered data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image writing apparatus used for a printer, a facsimile machine, a copying machine, and the like, and more particularly to an improvement in an image writing speed.

[0002]

2. Description of the Related Art A conventional image writing apparatus for writing image data generated by a personal computer, a scanner, or the like, comprises an image data input unit 1, an image clock generation unit 2, and an image data generator, as shown in the block diagram of FIG. It includes a latch section 3a, an image signal generation section 4a, a light source drive control section 5, and a laser light source 6. An image data input unit 1 inputs image data generated by a personal computer, a scanner or the like. The image clock generator 2 includes an oscillator 21, a detector signal generator 22, and a synchronization unit 23. The synchronization unit 23 synchronizes the clock signal generated by the oscillator 21 with the detector signal DET generated by the detector signal generation unit 22 in order to determine the image writing start timing, as shown in the time chart of FIG. As described above, the image data transfer clock VCLK is supplied to the latch unit 3a and the image signal generation unit 4
output to a. The latch unit 3a latches the image data H input to the image data input unit 1 for each period of the image data transfer clock VCLK sent from the image clock generation unit 2. The image signal generation unit 4a reads the image data H latched by the latch unit 3a according to the image data transfer clock VCLK, generates an image signal, and sends it to the light source drive control unit 5. The light source drive control unit 5 controls the drive of the laser light source 6 based on the transmitted image signal.

[0003]

As described above, in the conventional image writing apparatus, the image data is latched in accordance with one cycle of the image data transfer clock, and the latched image data is transmitted to the light source driving circuit. The image writing speed depends on the speed of the image data transfer clock, and it has been difficult to increase the image writing speed.

SUMMARY OF THE INVENTION The present invention has been made to solve such a disadvantage, and an object of the present invention is to provide an image writing apparatus capable of writing an image at twice the processing speed without changing the cycle of an image data transfer clock. It is assumed that.

[0005]

An image writing apparatus according to the present invention includes an image data input section, an image clock generation section, a latch section, an image signal generation section, and a light source drive control section. A data input unit for inputting image data to be written, and an image clock generating unit for synchronizing the timing of scanning the photosensitive member with the laser beam output from the laser light source and the timing of inputting the image data to the laser light source. The transfer clock is sent out, and the latch unit divides the image data input at the image data input unit into odd-numbered data and even-numbered data according to the high level and the low level of the image data transfer clock and latches them. When the image data transfer clock is at a high level, the image signal generator sends out either the odd-numbered data or the even-numbered data latched,
When the image data transfer clock is at a low level, the other latched data is transmitted, and the light source drive control unit drives the laser light source according to the odd-numbered data and the even-numbered data which are alternately transmitted. And

The latch section latches image data as either odd-numbered data or even-numbered data when the image data transfer clock goes high, and latches the image data when the image data transfer clock goes low. It is desirable to latch data as the other data.

An image data variable section is provided between the latch section and the image signal generating section. The image data variable section is provided with odd-numbered data and even-numbered data latched by the latch section in accordance with a process control signal. The pulse width or the voltage level or the pulse width and the voltage level may be varied and output.

Further, the image writing apparatus has a correction data set section and a selector section, and a plurality of gradation data corresponding to the characteristics of the image writing section are set in the correction data set section in advance. Selects the optimum gradation data from among a plurality of gradation data set in the correction data set section according to the odd-numbered data and the even-numbered data latched by the latch section, and the image data variable section selects the odd-numbered data. It is desirable that the pulse width or the voltage level or the pulse width and the voltage level be variably outputted in accordance with the contents of the gradation data selected in accordance with the data No. and the even-numbered data.

Further, it is preferable that a gradation data rewriting unit for rewriting the gradation data set in the correction data setting unit in accordance with the state of the image writing unit is provided.

Further, a delay correction section is provided between the image data variable section and the image signal generating section, and the delay correction section is configured to reduce a delay generated in the odd-numbered data and the even-numbered data which is changed by the image data variable section. It is desirable to correct.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image writing apparatus according to the present invention has an image data input section, an image clock generation section, a latch section, an image signal generation section, a light source drive control section, and a laser light source. The image data input unit inputs image data generated by a personal computer, a scanner, or the like. The image clock generator has an oscillator, a detector signal generator and a synchronization unit. The detector of the detector signal generator detects the laser beam emitted from the laser light source and sends a signal for determining the image writing start timing to the detector signal generator. In response to this signal, the detector signal generator outputs a detector signal. The synchronization unit synchronizes the clock signal generated by the oscillator with the detector signal generated by the detector signal generation unit to determine the image writing start timing, and sets the image data transfer clock to the latch unit and the image signal generation unit. Output to The latch unit has an odd data latch unit and an even data latch unit. The image data input from the image data input unit is at a high level or a low level of the image data transfer clock sent from the image clock generation unit. The data is latched by dividing it into odd-numbered data and even-numbered data according to the level. The image signal generator is composed of AND gate and OR gate logic circuits. When the image data transfer clock is at a high level, the odd data latch or the odd data latched by the even data latch or the even data is latched. Either of the second data is transmitted, and the other data latched by the odd data latch unit or the even data latch unit is transmitted when the image data transfer clock is at the low level. The light source drive control unit controls the drive of the laser light source according to the odd-numbered data and the even-numbered data that are alternately sent. The photosensitive member is scanned by the laser beam from the laser light source to write image data. In this way, the received image data is divided into odd-numbered data and even-numbered data and latched according to the high level and low level of the image data transfer clock, and the odd-numbered data and even-numbered data are latched by the image data transfer clock. Are alternately sent to the light source drive control unit, so that image data can be written at twice the speed of the image data transfer clock.

The latch section latches the input image data as either odd-numbered data or even-numbered data when the image data transfer clock goes high, and the image data transfer clock goes low. When the input image data is latched as the other data, accurate image data can be latched without being affected by noise or the like on the line of the image data transfer clock.

In the above description, the odd-numbered data and the even-numbered data latched by the latch section are directly sent to the image signal generating section. It is also possible to provide an image data variable unit that corrects image degradation and the like due to the above, and send the odd-numbered data and the even-numbered data latched by the latch unit to the image signal generation unit via the image data variable unit. In this case, when performing the process control in accordance with the environmental conditions of the image writing section having the photosensitive member or the like and the secular change, the image data variable section stores the odd-numbered data and the even-numbered data latched by the latch section. The pulse width or the voltage level or the pulse width and the voltage level are varied and output to the image signal generator. By varying the pulse width and the voltage level in this manner, the lighting control signal of the laser light source is varied, and the dot of the dot to be actually written is changed in accordance with the environmental conditions of the image writing section having the photoreceptor and the like and changes with time. The size can be changed, and a good image can always be formed stably.

By providing a correction data set section and a selector section in the image writing apparatus, a multi-valued image having a gradation can be written. In this case, the correction data setting section has, for example, a digital switch or a register in which a plurality of gradation data are set, and is adapted to the characteristics of the image writing apparatus itself such as an image writing section having a photosensitive member or the like. A plurality of gradation data are set in advance. The selector section has an odd selector and an even selector. Among the gradation data of a plurality of gradations set in the correction data set section according to the odd data and the even data latched by the latch section. And selects the optimum gradation data and sends it to the image data variable section. The image data variable unit changes the pulse width or voltage level or the pulse width and the voltage level of the transmitted gradation data and sends it to the image signal generation unit. In this way, the gradation data of a plurality of gradations according to the characteristics of the image writing device itself are set in advance, and the odd-numbered data and the even-numbered data latched from the gradation data of the plurality of gradations are set. Since the optimum gradation data is selected according to the data and the pulse width or the voltage level of the gradation data or the pulse width and the voltage level are changed and sent to the image signal generator, for example, a personal computer or the like is used. The multi-valued image data input from the CPU can be converted into a plurality of gradation data corresponding to the characteristics of the image writing apparatus itself and output. Therefore, the input image data can be corrected according to the characteristics of the image writing device itself, and an image having an optimum gradation can be obtained.

Although the correction data set section previously sets a plurality of gradation data according to the characteristics of the image writing apparatus itself, the gradation data set in the correction data set section is used. By providing a gradation data rewriting unit for rewriting data, the gradation data rewriting unit is set in the correction data setting unit in the case of a process control in which the diameter of the dot is varied according to the aging of the photosensitive member or the like. A plurality of gradation data can be varied. As described above, the preset gradation data of a plurality of gradations is rewritten into gradation data corresponding to the aging of the photosensitive member or the like, so that the optimum gradation data is stored in the correction data set section. Can be set, and an image having an optimum gradation can always be formed.

The image data variable section is selected according to the odd-numbered data and even-numbered data latched by the latch section or the odd-numbered data and even-numbered data sent from the latch section by the selector section. The odd-numbered data and the even-numbered data are sent directly to the image signal generation unit by changing the gradation data, but due to differences in the line pattern routing of the image data variable unit and delays caused by the parasitic capacitance of the circuit board, etc. There is a possibility that the dot diameter formed by the selected gradation data differs depending on the data or the odd-numbered data and the even-numbered data. Therefore, a delay correction unit is provided at the output stage of the image data variable unit to minimize the delay caused by the parasitic capacitance of the circuit board. In this way, it is possible to obtain an accurate dot diameter having no difference between the gradation data selected according to the odd-numbered data and the even-numbered data or the gradation data selected according to the odd-numbered data and the even-numbered data.

[0017]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, the image writing device includes an image data input unit 1, an image clock generation unit 2, a latch unit 3, an image signal generation unit 4, a light source drive control unit 5, and a laser light source 6. An image data input unit 1 inputs image data generated by a personal computer, a scanner or the like. Image clock generator 2
Has an oscillator 21, a detector signal generator 22, and a synchronization unit 23. The detector 24 of the detector signal generator 22 is, as shown in the schematic diagram of the optical system in FIG. 2, an end of a laser scanning range that is emitted from the laser light source 6, reflected by the polygon mirror 7 and scans the photoconductor 8. The laser beam reflected by the beam detector mirror 9 provided in the section is detected, and a signal for determining the image writing start timing is sent to the detector signal generator 22. In response to this signal, the detector signal generator 22 outputs a detector signal DET. The synchronization unit 23 synchronizes the clock signal CLK generated by the oscillator 21 with the detector signal DET generated by the detector signal generation unit 22 to determine the image writing start timing, and latches the image data transfer clock VCLK. Output to the unit 3 and the image signal generation unit 4. The latch unit 3 has an odd data latch unit 31 and an even data latch unit 32. The image data input from the image data input unit 1 is transmitted from the image clock generator 2 to the image data transfer clock. The odd-numbered data ODD and the even-numbered data EVEN are divided and latched according to the high or low level of VCLK. The image signal generator 4 is ORed with the AND gates 41 and 42.
The odd data latch unit 3 is constituted by a logic circuit of a gate 43 and when the image data transfer clock VCLK is at a high level.
Either the odd-numbered data ODD or the even-numbered data EVEN latched by the 1 or even-numbered data latch unit 32 is transmitted, and the odd-numbered data latch unit 31 or the even-numbered data is latched when the image data transfer clock VCLK is at a low level. -Taratch section 3
The other data latched in step 2 is transmitted. The light source drive control unit 5 controls the drive of the laser light source 6 according to the odd-numbered data ODD and the even-numbered data EVEN sent alternately. The photosensitive member 8 is scanned by the laser beam from the laser light source 6 to write image data.

The operation of writing the image data sent from a host device such as a personal computer on the photosensitive member 8 by the image writing apparatus constructed as described above will be described with reference to the time chart of FIG. explain.

When the image data input unit 1 receives the image data sent from the host device, the latch unit 3 changes the input image data to the high level of the image data transfer clock VCLK sent from the image clock generator 2. The image data is divided and latched into odd-numbered data ODD and even-numbered data EVEN according to the level and the low level. The image signal generation unit 4 sends out the odd-numbered data ODD latched by the latch unit 3 to the light source drive control unit 5 when the image data transfer clock VCLK is at a high level, for example, and outputs the even-numbered data EVEN latched by the latch unit 3. When the image data transfer clock VCLK is at a low level, it is sent to the light source drive control unit 5. The light source drive control unit 5 controls the drive of the laser light source 5 by the image signal H including the odd-numbered data ODD and the even-numbered data EVEN which are sent alternately. As described above, the received image data is divided into the odd-numbered data ODD and the even-numbered data EVEN and latched according to the high level and the low level which are half the cycle of the image data transfer clock VCLK, and the image data transfer clock VCLK The odd-numbered data ODD and the even-numbered data EVEN are alternately sent to the light source drive control unit 5 in the half cycle of the above, so that the image data is written at twice the speed of the image data transfer clock VCLK. be able to.

When the image data is latched by the latch unit 3 as described above, a latch circuit composed of elements such as 74LS373 is used for the latch unit 3, and when the image data transfer clock VCLK goes high. One of the input image data is latched as odd-numbered data ODD or even-numbered data EVEN, and an image data transfer clock is latched.
It is preferable that the image data input when VCLK goes low is latched as the other data. By using the level type latch in this manner, for example, compared to latching at the rising or falling edge of the image data transfer clock VCLK, the line of the image data transfer clock VCLK can be accurately controlled without being affected by noise or the like. Image data can be latched.

In the above embodiment, the case where the odd-numbered data ODD and the even-numbered data EVEN latched by the latch unit 3 are directly sent to the image signal generation unit 4 has been described. Image data variable units 10a and 10b are provided between the image signal generators 4 to correct the deterioration of the image due to environmental changes or changes over time. The odd-numbered data ODD and the even-numbered data latched by the latch unit 3 are provided. The EVEN may be sent to the image signal generator 4 via the image data variable units 10a and 10b. That is, the image data variable units 10a and 10b are composed of, for example, a PWM control circuit, a PM control circuit, or a PWM + PM control circuit, and control the process control according to the environmental conditions of the image writing unit having the photoreceptor 8 and the like and the aging. Then, the pulse width or voltage level or the pulse width and voltage level of the odd-numbered data ODD and the even-numbered data EVEN latched by the latch unit 3 are changed and output to the image signal generation unit 4. By varying the pulse width and the voltage level in this manner, the duty ratio and power of the lighting control signal of the laser light source 6 are varied, and the environmental conditions and the aging of the image writing unit having the photoconductor 8 and the like are changed. The size of the dots actually written can be changed according to changes, etc.
A good image can always be formed stably.

As described above, the image data variable units 10a, 1
0b, when the pulse width and the like of the odd-numbered data ODD and the even-numbered data EVEN are variable, the image data variable unit 1
There is a possibility that the dot diameter formed by the odd-numbered data ODD and the even-numbered data EVEN may be different due to a difference in routing of the 0a and 10b line patterns and a delay caused by the parasitic capacitance of the circuit board. Therefore, the delay correction units 11 are provided at the output stages of the image data variable units 10a and 10b, respectively.
a and 11b are provided to minimize the delay caused by the parasitic capacitance of the circuit board. Thus, the odd-numbered data OD
An accurate dot diameter with no difference can be obtained between D and the even-numbered data EVEN.

Although the above embodiment has been described in connection with the case of writing a binary image, a multi-valued image having a gradation can also be written. An embodiment in this case will be described with reference to the block diagram of FIG.

As shown in FIG. 5, the image writing apparatus includes an image data input unit 1, an image clock generation unit 2, a latch unit 3, image data variable units 10a and 10b, and delay correction units 11a and 11b.
11b, an image signal generator 4, a light source drive controller 5, and a laser light source 6, as well as a correction data set 12 and a selector 1.
3 The correction data set section 12 has, for example, 256 sets of digital switches and registers in which 8-bit gradation data is set, and has characteristics of an image writing apparatus itself such as an image writing section having the photoconductor 8 and the like. Is set in advance. The selector section 13 has an odd-numbered selector 13a and an even-numbered selector 13b, and the odd-numbered data ODD and the even-numbered data EVE latched by the latch section 3 are provided.
256 set in the correction data set unit 12 in accordance with N
The optimum gradation data is selected from the gradation data of the gradation.

In the image writing apparatus configured as described above, when the image transfer clock VCLK is at the high level, the 8-bit multi-valued odd-numbered data ODD latched by the latch unit 3 is sent to the odd-numbered selector 13a. When the image transfer clock VCLK is at a low level, the multi-valued even-numbered data EVEN latched by the latch section 3 is sent to the even-numbered selector 13b. Each time the odd-numbered data ODD is transmitted, the odd-number selector 13a refers to the transmitted odd-numbered data ODD and selects one of the 256-gradation data set in the correction data set unit 12. The image data variable unit 1 selects the optimum gradation data corresponding to the odd-numbered data ODD sent.
Send to 0a. Even-numbered selector 13b also has even-numbered data EV
Each time EN is sent, the data set in the correction data set unit 12 is referred to by referring to the sent even-numbered data EVEN.
Even-numbered data sent from gradation data
The optimum gradation data corresponding to EVEN is selected and sent to the image data variable unit 10b. Image data variable units 10a, 10b
The pulse width or voltage level of the transmitted grayscale data or the pulse width and voltage level are varied so that the delay correction unit 11a,
The image signal is sent to the image signal generator 4 via 11b. In this manner, multi-valued image data input from, for example, a personal computer or the like can be converted into 256-level gradation data corresponding to the characteristics of the image writing apparatus itself and output. Therefore, the input image data can be corrected according to the characteristics of the image writing device itself, and an image having an optimum gradation can be obtained.

In the above embodiment, the correction data set 1
The case where the gradation data of 256 gradations according to the characteristics of the image writing apparatus itself are set in advance in FIG. 2 has been described. However, as shown in the block diagram of FIG.
Is provided with a gradation data rewriting section 14 for rewriting the set gradation data, so that the process diameter can be varied in accordance with the aging of the photosensitive member 8 or the like. The gradation data of 256 gradations set in the correction data set section 12 can be changed. As shown in FIG. 6, the gradation data rewriting unit 14 stores a plurality of systems of gradation data corresponding to the temporal change of the photosensitive member 8 and the like.
41, a CPU 142, and a decoder 143. When a control signal corresponding to a temporal change of the photosensitive member 8 or the like is input during the process control, the CPU 14
2 sends to the decoder 143 a rewrite signal of gradation data according to the input control signal. The decoder 143 sends the gradation data corresponding to the transmitted rewrite signal to the register of the correction data setting unit 12, and rewrites the gradation data set previously. In this way, the optimum gradation data according to the aging of the photosensitive member 8 and the like can be set in the correction data set section 12, and an image having the optimum gradation can always be formed.

[0027]

As described above, according to the present invention, the half cycle of the image data transfer clock for synchronizing the timing of scanning the photosensitive member with the laser beam output from the laser light source and the timing of inputting the image data to the laser light source. The received image data is divided into odd-numbered data and even-numbered data and latched according to the high level and the low level, and the odd-numbered data and even-numbered data are alternated in the half cycle of the image data transfer clock. Since the image data is sent to the light source drive control section, the image data can be written at twice the speed of the image data transfer clock without changing the period of the image data transfer clock.

When the image data transfer clock goes high, one of the image data is latched as odd-numbered data or even-numbered data, and when the image data transfer clock goes low, the image data is latched. Since the data is latched as the other data, accurate image data can be latched without being affected by noise even if noise is generated on the line of the image data transfer clock. Image data can be written.

Further, the pulse width or voltage level or pulse width or voltage level of the odd-numbered data and the even-numbered data latched by the latch unit in accordance with the environmental conditions of the image writing unit having the photoreceptor and the like and the change with time. Since the size of the dots to be written is changed by changing the level, a good image is always formed stably without being affected by the environmental conditions of the image writing section having the photoreceptor and the like, and changes over time. be able to.

Further, gradation data of a plurality of gradations according to the characteristics of the image writing device itself are set in advance, and the odd-numbered data and the even-numbered data latched from the gradation data of the plurality of gradations are set. The optimum grayscale data is selected in accordance with the data of the grayscale data, and the pulse width or voltage level or the pulse width and the voltage level of the grayscale data are varied. Since the data is converted into a plurality of gradation data corresponding to the characteristics of the image writing device and output, the input image data is converted according to the characteristics of the image writing device itself. Thus, it is possible to always obtain an image in which the gradation is expressed with the optimum gradation even if the input device changes.

Further, in the case of a process control in which the diameter of the dot is varied in accordance with the aging of the photosensitive member or the like, a plurality of gradation data corresponding to the characteristics of the image writing apparatus itself set in advance. Since the data is rewritten to the gradation data according to the aging of the photoreceptor or the like, the optimum gradation data can be set in the correction data set section, and the photoreceptor and the like in the image writing section can be set. It is possible to always form a good image in which the gradation is expressed with the optimum gradation without being affected by the change with time.

Further, the delay caused by the difference in the line pattern of the odd-numbered data and the even-numbered data and the delay caused by the parasitic capacitance of the circuit board are minimized, so that the difference between the odd-numbered data and the even-numbered data is minimized. It is possible to obtain an accurate dot diameter and obtain a good image without any defect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an outline of an optical system of the embodiment.

FIG. 3 is a time chart showing an operation when writing an image on a photoconductor.

FIG. 4 is a block diagram showing a configuration of a second embodiment.

FIG. 5 is a block diagram showing a configuration of a third embodiment.

FIG. 6 is a block diagram illustrating a configuration of a gradation data rewriting unit according to a fourth embodiment.

FIG. 7 is a block diagram showing a configuration of a conventional device.

FIG. 8 is a time chart showing an operation of writing an image on a photoconductor of a conventional apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image data input part 2 Image clock generation part 3 Latch part 4 Image signal generation part 5 Light source drive control part 6 Laser light source 10 Image data variable part 11 Delay correction part 12 Correction data set part 13 Selector part 14 Gradation data Rewriting section 31 Odd data latch section 32 Even data latch section

Claims (6)

[Claims] An image data input section, an image clock generation section, a latch section, an image signal generation section and a light source drive control section are provided. The image data input section inputs image data to be written,
The image clock generator sends out an image data transfer clock for synchronizing the timing of scanning the photoreceptor with the laser beam output from the laser light source and the timing of inputting image data to the laser light source, and the latch unit inputs image data. The image data input by the section is divided into odd-numbered data and even-numbered data according to the high level and the low level of the image data transfer clock and latched. In this case, either the odd-numbered data or the even-numbered data latched is transmitted, and when the image data transfer clock is at a low level, the other latched data is transmitted, and the light source drive control unit is alternately transmitted. An image writing apparatus for driving a laser light source according to odd-numbered data and even-numbered data. 2. The latch section latches image data as either odd-numbered data or even-numbered data when the image data transfer clock goes high, and when the image data transfer clock goes low. 2. The image writing apparatus according to claim 1, wherein the image data is latched as the other data. 3. An image data variable section between the latch section and the image signal generating section, wherein the image data variable section has odd-numbered data and even-numbered data latched by the latch section in response to a process control signal. 3. The image writing apparatus according to claim 1, wherein the pulse width or the voltage level or the pulse width and the voltage level are variably output. 4. The image writing apparatus has a correction data set section and a selector section, and sets a plurality of gradation data according to the characteristics of the image writing section in the correction data set section in advance. Selects the optimum gradation data from among a plurality of gradation data set in the correction data set section according to the odd-numbered data and the even-numbered data latched by the latch section, and the image data variable section selects the odd-numbered data. 4. The image writing apparatus according to claim 3, wherein a pulse width or a voltage level or a pulse width and a voltage level are variably outputted in accordance with the contents of the gradation data selected in accordance with the data and the even-numbered data. 5. An image writing apparatus according to claim 4, further comprising a gradation data rewriting section for rewriting gradation data set in said correction data set section in accordance with a state of the image writing section. 6. A delay correcting section between the image data variable section and the image signal generating section, wherein the delay correcting section is configured to reduce a delay generated in the odd-numbered data and the even-numbered data which is changed by the image data variable section. 6. The image writing device according to claim 5, wherein the correction is performed.