JPH05127499A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To enhance visual printing quality even in the case that graphic data using a dither pattern is printed by making focus variable. CONSTITUTION:A means for supporting an LED head 3 is provided in order to change a distance between a photosensitive drum 2 and the head 3, and the focus is corrected by changing the distance between the drum 2 and the head 3 by the supporting means. Then, a control panel is provided and operated to instruct the correction of the focus on a printed image. In the case of receiving the instruction of correcting the focus from the control panel, the supporting means is controlled and the distance between the drum 2 and the head 3 is changed by a previously set length. Therefore, the focus on the printed image is corrected and the change of gradation is smoothed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer capable of correcting the focus of a printed image according to the print content.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer, a charged photoconductor drum is irradiated with a light source to form an electrostatic latent image on the surface thereof, and toner is attached to the electrostatic latent image for development. After that, the toner image is transferred onto a recording medium and fixed. In this case, the light source includes a light emitting diode array, a laser beam, and the like. However, whichever light source is used, the light flux emitted from the light source is printed so that the print image is not out of focus and out of focus. The size of the dots is converged and the surface of the photoconductor drum is irradiated with the light.

For example, in an electrophotographic printer using a light emitting diode array as a light source, a converging rod lens array is provided between the light emitting diode array and the photosensitive drum to converge the light beam and focus on the surface of the photosensitive drum. The relative position of each member is fixed so that the focus does not shift with time.

[0004]

However, in the above-mentioned conventional electrophotographic printer, since the focus is adjusted regardless of the type of print data, the print quality is deteriorated. For example, when printing graphic data using a dither pattern that expresses gradation by changing the area ratio of black and white, it is better to shift the focus of the print image because the gradation change becomes smoother and the visual print quality is improved. However, the focus cannot be corrected because the focus is set for printing the character data.

The present invention provides an electrophotographic printer which solves the problems of the conventional electrophotographic printer described above and can improve the visual print quality even when printing graphic data using a dither pattern. The purpose is to do.

[0006]

Therefore, in the electrophotographic printer of the present invention, L is provided facing the photosensitive drum.
An ED head is provided, and the charged photoconductor drum is illuminated by the LED head to form an electrostatic latent image on the surface thereof. The electrostatic latent image is developed into a toner image by a developing device, and the toner image is transferred and fixed on a recording medium by a transfer device and a fixing device.

Means is provided for supporting the LED head so that the distance between the photoconductor drum and the photoconductor drum can be changed.
The focus of the printed image can be corrected by changing the distance between the ED heads. Therefore, an operation panel is provided, and the focus correction can be instructed by operating the operation panel. When a focus correction instruction is received from the operation panel, the distance between the photosensitive drum and the LED head can be changed by a preset amount.

Further, without instructing the focus correction of the print image by operating the operation panel, the print data received from the host device is analyzed to determine whether the print content is graphic data using a dither pattern. It is possible to correct the focus of the printed image. Further, the focus correction amount corresponding to the dither pattern type is stored in the memory, the focus correction amount corresponding to the dither pattern type is read from the memory, and only the correction amount is applied between the photosensitive drum and the LED head. You can change the distance.

It is also possible to send a command from the host device to the controller section, analyze the command received by the controller section, and change the distance between the photosensitive drum and the LED head by the amount instructed by the command.

[0010]

According to the present invention, the LED head is arranged so as to face the photoconductor drum as described above, and the charged photoconductor drum is illuminated by the LED head to form an electrostatic latent image on the surface thereof. To form. The electrostatic latent image is developed into a toner image by a developing device, and the toner image is transferred and fixed on a recording medium by a transfer device and a fixing device.

Means is provided for supporting the LED head so that the distance between the photoconductor drum and the photoconductor drum can be changed.
The focus of the printed image can be corrected by changing the distance between the ED heads. Therefore, an operation panel is provided, and an instruction to correct the focus of a print image can be issued by operating the operation panel. When a focus correction instruction is received from the operation panel, the supporting means is controlled to change the distance between the photosensitive drum and the LED head by a preset amount.

Therefore, the focus of the printed image is corrected, and the gradation change becomes smooth. Also, without instructing to correct the focus of the printed image by operating the operation panel,
The focus of the print image can be corrected by analyzing the print data received from the host device and determining whether the print content is graphic data using a dither pattern. In this case, since it is not necessary to instruct by the operation panel, even if the character data and the graphic data using the dither pattern are mixed for each page, the focus is corrected without stopping the printing operation of the electrophotographic printer. be able to.

Further, the focus correction amount corresponding to the type of dither pattern is stored in a memory, and the focus correction amount corresponding to the type of dither pattern is read from the memory, and the distance between the photosensitive drum and the LED head is read. Can be changed. In this case, the focus of the print image is corrected by the optimum correction amount corresponding to the type of dither pattern.

The host device can send a command to the controller section to instruct the focus correction amount. In this case, the controller section analyzes the received command and changes the distance between the photosensitive drum and the LED head by the amount designated by the command.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is an exploded perspective view of an essential part of an electrophotographic printer of the present invention, FIG. 2 is a schematic view of an electrophotographic printer of the present invention, FIG. 3 is a sectional view of an essential part of an electrophotographic printer of the present invention, and FIG. It is a control block diagram of the electrophotographic printer which shows an Example.

In FIG. 2, reference numeral 1 denotes an electrophotographic printer, 2
Is a photosensitive drum, and 3 is an LED head. 1 and 3, the LED head 3 includes a light emitting diode array (LED array) 31, a frame 32 for fixing the LED array 31, and a light emitting portion of the LED array 31 is accurately positioned at one focus position. As described above, the converging rod lens array 33 is fixed to the frame 32, and the reference holes 34 and 35 for controlling the relative positions of the photosensitive drum 2 and the LED head 3 are provided.

Reference numeral 40 denotes a photosensitive drum unit, which is composed of the photosensitive drum 2, flanges 42 and 43, and photosensitive drum frames 48 and 49. The photosensitive drum 2 is rotated by the photosensitive drum frames 48 and 49. Support shafts 44 and 45 for making the LED head 3 and the guide shafts 46 and 47 for maintaining the parallelism between the LED head 3 and the photosensitive drum 2 are integrally formed.

The LED head 3 has a spring 46.
a through the guide shaft 4 through the reference holes 34 and 35.
The photoconductor drum unit 40 by passing through 6, 47
Loaded to. The distance between the LED head 3 and the photosensitive drum 2 can be changed by pressing the LED head 3 from the outside while maintaining the parallelism. 5
0 and 51 are eccentric cams for pressing the LED head 3,
A shaft 52 supports and connects the eccentric cams 50 and 51. The two eccentric cams 50 and 51 have the same eccentricity and shape so that the left and right sides of the LED head 3 can be pressed with the same force, and are fixed to the shaft 52 in an aligned state. 54 is a motor for rotating the shaft 52, 53 is the motor 54 and the shaft 52
The reference numeral 55 denotes a potentiometer for electrically detecting the rotation angle of the shaft 52 and is fixed to the shaft 52.

In the electrophotographic printer 1 having the above structure,
When the motor 54 is rotated, the eccentric cams 50 and 51 rotate, and the pressing force applied to the LED head 3 changes equally to the left and right. As a result, the distance between the LED head 3 and the photosensitive drum 2 changes while maintaining parallelism. Therefore, it is possible to adjust the distance and shift the surface of the photosensitive drum 2 from the focal position of the converging rod lens array 33 to correct the focus of the printed image.

Next, the control device of the electrophotographic printer 1 of the present invention will be described. In FIG. 4, the electrophotographic printer 1 includes a controller unit 1a that receives print data from the terminal 4 and a printer unit 1b that performs printing. The controller unit 1a is provided with an external connection interface unit 5 such as a Centronics interface, a reception buffer 6, a microprocessor 7, a font memory 8a, an image memory 8b, a general-purpose memory 8c, a printer interface unit 9 and an operation panel 10. The print data sent from the terminal 4 is supplied to the reception buffer 6 via the external connection interface unit 5.

Further, the printer section 1b is provided with a print sheet supply section 11 for automatically supplying a standard recording medium, that is, a print sheet on the right side surface side. Further, inside the printer unit 1b, a registration roller 12 for starting the running of the printing paper from the printing paper supply unit 11, a clutch driving type hopping roller 13 for feeding the printing paper to the registration roller 12, and an outer peripheral photosensitive member. A photoconductor drum 2 having a body surface, a charger 15 for uniformly and evenly charging the photoconductor surface, an LED head 3 for forming an electrostatic latent image corresponding to image data on the photoconductor surface, a developing device 17, and a transfer device. 1
8, a fixing device 19 and a cleaner 24 are provided. A discharge unit 20 is provided on the left side of the printer unit 1b to discharge the printed printing paper.

Further, the printer unit 1b is provided with a microprocessor 21 for communicating with the controller unit 1a and controlling the entire printer unit 1b. A bidirectional serial interface 22 for communication between the controller section 1a and the printer section 1b and a signal line for transferring and controlling print data formed by image data are provided. They are connected by the video interface 23 they have.

Here, the serial interface 22
Is the printer interface unit 9 of the controller unit 1a.
The microprocessor 7 and the microprocessor 21 of the printer unit 1b are connected to each other via the video interface 2
Similarly, 3 also includes a microprocessor unit 7 and a printer unit 1b via the printer interface unit 9 of the controller unit 1a.
Is connected to the LED head 3. In addition, the LED head 3 includes the microprocessor 21 of the printer unit 1b and an LED.
It is connected by the position control signal line 14 of the head 3.

When the electrophotographic printer 1 having the above-described configuration receives print data from a host device (not shown) via the terminal 4 and the external connection interface section 5, the print data is fetched into the reception buffer 6. When one page of print data is fetched into the reception buffer 6, the photoconductor drum 2 rotates, the surface of the photoconductor is uniformly and evenly charged by the charger 15, and the development in the developing device 17 is performed. A preliminary operation such as stirring the agent is performed. When the preliminary operation is completed, the clutch of the hopping roller 13 is turned on, the printing paper is taken out from the printing paper supply unit 11 and sent to the registration roller 12.

On the other hand, the microprocessor 7 reads the character code contained in the print data fetched in the reception buffer 6, creates image data by referring to the font memory 8a, and writes the image data in the image memory 8b. In the image memory 8b, for example, image data for one page of printing paper is edited and stored. Further, image data is directly sent as print data from a host device (not shown), and the terminal device 4 and the external connection interface unit 5 are connected.
When it is transmitted to the reception buffer 6 via the, the microprocessor 7 writes it as it is in a predetermined address of the image memory 8b.

In the case of printing graphic data, the graphic data is sent in the form of a graphic command from the host device, so the print data is edited and calculated by the microprocessor 7 and directly stored in the image memory 8b as image data. Written. In this way, when the analysis and editing of the image data are completed, the printing paper reaching the registration roller 12 is conveyed toward the transfer device 18. In parallel with this, the microprocessor 7
The image data is supplied to the LED head 3 via the video interface 23, the LED head 3 is driven, and an electrostatic latent image is formed on the surface of the photosensitive drum 2. When the photosensitive drum 2 rotates in the direction of arrow a in the figure,
The electrostatic latent image is developed by the developing device 17 and transferred to the printing paper by the transfer device 18. After that, the printing paper is fixed in the fixing device 19 and is discharged to the discharge unit 20. The developer remaining on the photosensitive drum 2 after the transfer is removed by the cleaner 24.

In this way, the image based on the print data received from the host device is printed on the printing paper. By the way, the distance between the LED head 3 and the photosensitive drum 2 is controlled by a position control signal output from the microprocessor 21 of the printer unit 1b. Therefore, the microprocessor 21 detects the distance with the potentiometer 55 and changes the distance by rotating the motor 54.
In this case, the microprocessor 21 uses the LED head 3
The distance between the photosensitive drum 2 and the photosensitive drum 2 is convergent rod lens array 3
The focal length of 3 is controlled so as to be the same.

When printing graphic data using a dither pattern, the operator operates the operation panel 10 prior to printing, and the LED head 3 and the photosensitive drum 2 are operated.
Instruct to change the distance between them, that is, to correct the focus. The microprocessor 7 of the controller unit 1a that manages the operation panel 10 reads this instruction and transmits it to the microprocessor 21 of the printer unit 1b using the serial interface 22. Upon receipt of this instruction, the microprocessor 21 of the printer unit 1b outputs a position control signal for the LED head 3 and changes the distance between the LED head 3 and the photosensitive drum 2 by an amount obtained in advance by an experiment.

In this way, the focus of the print image formed on the surface of the photosensitive drum 2 is corrected and the print image can be blurred. In the embodiment described above, in order to instruct the operation panel 10 to correct the focus of the print image, the printing operation is temporarily stopped and an instruction to correct the focus is given before printing the graphic data using the dither pattern. There must be. Therefore, when a page for printing character data and a page for printing graphic data using a dither pattern coexist, continuous printing cannot be performed.

Therefore, in the second embodiment of the present invention, the controller unit 1a analyzes the print data for one page received from the host device, and the print content uses the dither pattern according to the control information in the print data. It is determined whether or not the graphic data has been deleted. Then, if it is graphic data using a dither pattern, an instruction to correct the focus of the print image is given to the microprocessor 21 of the printer unit 1b.

FIG. 5 is a flow chart of an electrophotographic printer showing a second embodiment of the present invention. Step S1 Waits until print data is received from the host device. Step S
2 It processes the print data received from the host device.
In step S3, it is determined whether the print data for one page has been received. When it is completed, the process proceeds to step S4, and when it is not completed, steps S1 to
The operation of S3 is repeated. In step S4, it is determined whether the print content is graphic data using a dither pattern. In step S5, the printer unit 1b is instructed to change the distance between the LED head 3 and the photosensitive drum 2 and correct the focus of the printed image. Step S6 Printing is performed. In step S7, the printer unit 1b is instructed to return the focus of the print image to the original state to prepare for printing the next page. Then, the above operation is repeated.

When the print content is not the graphic data using the dither pattern, after printing in step S6, the printer unit 1b is instructed to restore the focus of the print image in step S7. In this case, Since the printer unit 1b is originally in focus, it is not necessary to restore the actual focus. With the above processing, when the print content is graphic data using a dither pattern, the focus can be corrected by the printer's own judgment, and character data and graphic data using a dither pattern are mixed in page units. Even in this case, continuous printing can be performed.

Next, a third embodiment of the present invention will be described. When it is determined whether or not the print content is the graphic data using the dither pattern, the print quality is merely improved on average with respect to the graphic data using the various dither patterns. That is, the optimum focus correction cannot be performed according to the type of dither pattern.

FIG. 6 is a flowchart of the electrophotographic printer showing the third embodiment of the present invention. Step T1 Waits until print data is received from the host device. Step T
2 It processes the print data received from the host device.
In step T3, it is determined whether the print data for one page has been received. When it is completed, the process proceeds to step T4, and when it is not completed, steps T1 to
The operation of T3 is repeated. Step T4: It is judged whether or not the print content is graphic data using a dither pattern. Step T5 If the print content is graphic data using a dither pattern, the print data is further analyzed and the type of dither pattern is determined from the control information. Step T6 The printer unit 1b is instructed to correct the focus of the print image. Step T7 The printer unit 1b is instructed to correct the focus according to the type of dither pattern. The optimum correction amount corresponding to the type of dither pattern is obtained by experiments or the like, and is stored as data in advance in the general-purpose memory 8c inside the controller unit 1a. When the type of dither pattern is determined in step T5, the optimum correction amount can be read. Further, the printer unit 1b has a motor 54
The distance between the LED head 3 and the photosensitive drum 2 is changed by controlling the rotation angle of the controller 1a.
Correct only the amount indicated by. Step T8 Printing is performed. Step T9 The printer unit 1b is instructed to return the focus to the preparation for printing the next page. Then, the above operation is repeated.

In step T4, if the print content is not the graphic data using the dither pattern, printing is performed without correcting the focus, as in the second embodiment. With the above processing, it is possible to perform correction so that the focus of the printed image is optimal according to the type of dither pattern.

Next, a fourth embodiment of the present invention will be described. When printing graphic data that is not defined as a dither pattern, such as graphic data read from a scanner, the controller unit 1
Even if the print data is analyzed in a, it is not possible to determine whether focus correction is necessary. Therefore, a command sent from the host device and executable by the electrophotographic printer 1 is defined in advance, and the command is used to instruct a numerical value for the focus correction amount. The above commands allocate unused ones that do not affect the conventional commands. When the above command is received, the controller unit 1
b transmits the focus correction amount designated by the host device to the printer unit 1b, and the printer unit 1b corrects the focus according to the correction amount.

As a result, the focus of the print image can be arbitrarily instructed from the host device, and optimum focus correction can be performed in any graphic data printing. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0038]

As described in detail above, according to the present invention, it is possible to instruct the correction of the focus of the print image by operating the operation panel and change the distance between the photosensitive drum and the LED head. Therefore, when printing the graphic data using the dither pattern, it is possible to correct the focus of the print image, smooth the gradation change, and improve the print quality.

The focus of the print image can be corrected by analyzing the print data received from the host device and determining whether the print content is graphic data using a dither pattern. In this case, since it is not necessary to instruct by the operation panel, even if the character data and the graphic data using the dither pattern are mixed for each page, the focus is corrected without stopping the printing operation of the electrophotographic printer. be able to. Therefore, the printing quality is improved in printing both the character data and the graphic data.

Further, the focus correction amount corresponding to the dither pattern type is stored in the memory, the focus correction amount corresponding to the dither pattern type is read from the memory, and only the correction amount is applied to the photosensitive drum and the LED. The distance between the heads can be changed. In this case, the focus can be corrected to an optimum value corresponding to the type of dither pattern.

It is also possible to send a command from the host device to the controller section, analyze the command received by the controller section, and change the distance between the photosensitive drum and the LED head by the amount designated by the command. Therefore, when printing data read by a scanner or the like, it is possible to freely instruct focus correction even if it is not possible to determine whether the data is graphic data using a dither pattern even if the print data is analyzed. be able to.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of essential parts of an electrophotographic printer of the present invention.

FIG. 2 is a schematic diagram of an electrophotographic printer of the present invention.

FIG. 3 is a cross-sectional view of essential parts of the electrophotographic printer of the present invention.

FIG. 4 is a control block diagram of an electrophotographic printer showing an embodiment of the present invention.

FIG. 5 is a flowchart of an electrophotographic printer showing a second embodiment of the present invention.

FIG. 6 is a flowchart of an electrophotographic printer showing a third embodiment of the present invention.

[Explanation of symbols]

 1 Electrophotographic Printer 1a Controller 1b Printer 2 Photoreceptor Drum 3 LED Head 7,21 Microprocessor 8c General-purpose Memory 10 Operation Panel 14 Position Control Signal Lines 34,35 Reference Holes 46,47 Guide Shafts 46a, 47a Spring

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Claims (4)

[Claims] 1. A charged photosensitive drum is irradiated by an LED head to form an electrostatic latent image on the surface thereof, and the electrostatic latent image is developed to form a toner image, and the toner image is recorded on the recording medium. In an electrophotographic printer that transfers and fixes to
(A) means for supporting the LED head so that the distance to the photosensitive drum can be changed, and (b)
A means for instructing the focus correction of the print image by operating the operation panel, and (c) changing the distance between the photosensitive drum and the LED head by a preset amount when receiving the focus correction instruction from the operation panel. An electrophotographic printer having means. 2. A charged photosensitive drum is irradiated with an LED head to form an electrostatic latent image on the surface thereof, and the electrostatic latent image is developed to form a toner image. The toner image is recorded on the recording medium. In an electrophotographic printer that transfers and fixes to
(A) means for supporting the LED head so that the distance to the photosensitive drum can be changed, and (b)
A means for analyzing print data received from a higher-level device to determine whether or not the print content is graphic data using a dither pattern; and (c) a print content being graphic data using a dither pattern, An electrophotographic printer comprising means for changing the distance between the photosensitive drum and the LED head by a set amount. 3. (a) means for analyzing print data received from a host device to determine the type of dither pattern;
(B) A memory for storing the focus correction amount corresponding to the type of dither pattern, and (c) a focus correction amount corresponding to the type of dither pattern is read from the memory, and the photosensitive drum and the LED head are read by the correction amount. The electrophotographic printer according to claim 2, further comprising means for changing a distance therebetween. 4. A charged photosensitive drum is irradiated by an LED head to form an electrostatic latent image on the surface, the electrostatic latent image is developed to form a toner image, and the toner image is recorded on the recording medium. In an electrophotographic printer that transfers and fixes to
(A) means for supporting the LED head so that the distance to the photosensitive drum can be changed, and (b)
An electrophotographic printer comprising means for analyzing a command received from a host device and changing a distance between the photosensitive drum and the LED head by an amount designated by the command.