Patent Grant
9746795
This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2015-052463, filed on Mar. 16, 2015, and 2015-240334, filed on Dec. 9, 2015, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Technical Field
The present invention relates to an optical writing control device, an image forming apparatus, and an optical writing control method.
Description of the Related Art
In recent years, the computerization of information tends to be promoted. Thus, image processing apparatuses such as a printer and a facsimile that are used for outputting the computerized information, and a scanner that is used for computerizing documents have become indispensable apparatuses. Among such image processing apparatuses, an electrophotographic image forming apparatus is widely used as an image forming apparatus used for outputting the computerized documents.
The electrophotographic image forming apparatus performs image formation and image output in the following manner. First, an electrostatic latent image is formed by exposing a photoconductor. Then, the formed electrostatic latent image is developed using developer such as toner, so that a toner image is formed. The toner image is transferred onto a sheet, and the sheet is output.
In such an electrophotographic image forming apparatus, after the toner image developed on the photoconductor is transferred, discharge exposure of exposing the entire surface for eliminating electric charge remaining on the photoconductor is performed. A dedicated light source is provided for this discharge exposure in some cases. In other cases, a light source for forming an electrostatic latent image is also used for the discharge exposure.
On the other hand, in some cases, a linear light source is used as a light source for exposing the photoconductor. In the linear light source, point light sources such as light emitting diode (LED) elements or electro-luminescence (EL) elements are linearly arrayed in a main scanning direction. When the LED elements are arrayed, the linear light source is referred to as an LED Array (LEDA).
In one aspect of the invention, an optical writing control device includes a light source controller to control emission of a light source onto a photoconductor surface in a latent image forming process and a discharge process, the light source including a plurality of linearly-arranged light emission elements. In the latent image forming process, the light source controller causes the light source to emit the light based on image data input to the light source controller to form an electrostatic latent image on the photoconductor surface. In the discharge process, the light source controller causes the light source to emit the light while turning off a part of the plurality of light emission elements to discharge the photoconductor surface. A light emission time of one light emission control in the discharge process is set longer than a light emission time of one light emission control in the latent image forming process.
In another aspect of the invention, an optical writing control device includes a light source controller to control lighting of a light source onto a photoconductor surface in latent image forming process and a discharge process. In the latent image forming process, the light source controller causes the light source to emit the light based on image data input to the light source controller to form an electrostatic latent image on the photoconductor surface. In the discharge process, the light source controller causes the light source to emit the light to discharge the photoconductor surface. A resolution in a sub-scanning direction in the discharge process is set lower than a resolution in a sub-scanning direction in the latent image forming process.
A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In describing example embodiments shown in the drawings, specific terminology is employed for the sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
Referring to the drawings, embodiments of the present invention will be described in detail below using examples.
In a first embodiment, an image forming apparatus serving as a multifunction peripheral (MFP) will be described. The image forming apparatus is an electrophotographic image forming apparatus, which includes a light source for exposing a photoconductor. More specifically, a linear light source in which light emission elements are arrayed in a main scanning direction is used as the light source.
The above-described linear light source is also used in the exposure for eliminating electric charge remaining on the photoconductor from which a toner image has been transferred. As described below, the instantaneous consumed amount of current during a discharge process by the linear light source is reduced, through thinning out light emission elements to be driven to emit light. In order to compensate for the reduction in exposure energy that is incidental to the thinning out, a strobe period, i.e., a light emission time in one light emission control is extended.
The CPU 10 is a processor, which controls entire operation of the image forming apparatus 1. The RAM 11 is a volatile recording medium capable of reading or writing at high speed, and used as a work area for the CPU 10. The ROM 12 is a read-only non-volatile recording medium, and stores programs such as firmware. The engine 13 executes image formation.
The HDD 14 is a non-volatile recording medium capable of reading or writing various data, and stores an operating system (OS), various control programs, an application program, and the like. The I/F 15 connects the bus 18 to hardware, networks, and the like, to perform control in data transmission or reception. The LCD 16 operates as a visual user interface for allowing a user to check the state of the image forming apparatus 1. The operation device 17 operates as a user interface for allowing a user to input information to the image forming apparatus 1, and includes a touch panel, various hardware keys, and the like that may be provided on a screen displayed by the LCD 16.
The CPU 10 performs calculation according to a program stored in the ROM 12, or a program loaded into the RAM 11 from a recording medium such as the HDD 14 or an optical disc, to cooperate with hardware to achieve various functions as described below according to this embodiment.
Next, a functional configuration of a control section of the image forming apparatus 1 according to this embodiment will be described with reference to
The controller 20 includes a main controller 30, an engine controller 31, an input/output (I/O) controller 32, an image processing device 33, and a user interface (UI) controller 34. As illustrated in
The display panel 24 serves as an output interface for visually displaying the state of the image forming apparatus 1 (LCD 16), and also serves as an input interface (operation device 17) for the user directly operating the image forming apparatus 1 or inputting information to the image forming apparatus 1, as a touch panel. Thus, the display panel 24 corresponds to the LCD 16 and the operation device 17 in
The controller 20 corresponds to instructions of the CPU 10, which are generated according to a program stored in a memory. The controller 20 functions as a controller for controlling the entire image forming apparatus 1.
The main controller 30 has a function of controlling the components included in the controller 20, and issues a command to the components in the controller 20. The engine controller 31 functions as a driver for controlling or driving the print engine 26, the scanner 22, and the like. The I/O controller 32 inputs signals and commands that are input via the network I/F 28, to the main controller 30. In addition, the main controller 30 controls the I/O controller 32, and accesses another device via the network I/F 28.
According to the control of the main controller 30, the image processing device 33 generates rendering information based on print information included in an input print job. The rendering information refers to information for rendering an image to be formed by the print engine 26 in an image forming operation. In addition, the print information included in the print job refers to image information that has been converted by a printer driver installed on an information processing apparatus such as a PC, into a format recognizable by the image forming apparatus 1. The UI controller 34 displays information on the display panel 24 or notifies the main controller 30 of information input via the display panel 24.
When the image forming apparatus 1 operates as a printer, first, the I/O controller 32 receives a print job via the network I/F 28. The I/O controller 32 transfers the received print job to the main controller 30. Upon receiving the print job, the main controller 30 controls the image processing device 33 to generate rendering information based on print information included in the print job.
When the rendering information is generated by the image processing device 33, the engine controller 31 controls the print engine 26 based on the generated rendering information to form an image on a sheet conveyed from the sheet feed table 25. In other words, the print engine 26 functions as an image forming unit. A document on which an image is formed by the print engine 26 is discharged onto the discharge tray 27.
When the image forming apparatus 1 operates as a scanner, the UI controller 34 or the I/O controller 32 transfers a scanning execution signal to the main controller 30 in response to an operation of the display panel 24 that is performed by the user, or a scanning execution instruction input via the network I/F 28 from an external PC or the like. The main controller 30 controls the engine controller 31 based on the received scanning execution signal.
The engine controller 31 drives the ADF 21 to convey an image capturing target document set on the ADF 21, to the scanner 22. In addition, the engine controller 31 drives the scanner 22 to capture an image of the document conveyed from the ADF 21. In addition, when the document is not set on the ADF 21 but directly set on the scanner 22, the scanner 22 captures an image of the set document according to the control of the engine controller 31. In other words, the scanner 22 operates as an image capturing unit.
In an image capturing operation, an image sensor such as a charge-coupled device (CCD) sensor that is included in the scanner 22 optically scans a document, so that image capturing information is generated based on optical information. The engine controller 31 transfers the image capturing information generated by the scanner 22, to the image processing device 33. According to the control of the main controller 30, the image processing device 33 generates image information based on the image capturing information received from the engine controller 31. The image information generated by the image processing device 33 is stored into a storage medium such as the HDD 14 that is loaded on the image forming apparatus 1. In other words, the scanner 22, the engine controller 31, and the image processing device 33 function as a document reader in conjunction with one another.
In response to an instruction from the user, the image information generated by the image processing device 33 is directly stored into the HDD 14 or the like, or transmitted to an external apparatus via the I/O controller 32 and the network OF 28. In other words, the ADF 21 and the engine controller 31 function as an image input unit.
In addition, when the image forming apparatus 1 operates as a copying machine, the image processing device 33 generates rendering information based on image capturing information that has been received by the engine controller 31 from the scanner 22 or image information generated by the image processing device 33. Similarly to the case of operating as a printer, the engine controller 31 drives the print engine 26 based on the generated rendering information.
Next, the configuration of the print engine 26 will be described with reference to
In addition, the sheet 104 fed from the sheet feeding tray 101 is once stopped by a registration roller 103, and fed to a position where an image is to be transferred from the conveyance belt 105, according to an image forming timing of the image forming unit 106.
The plurality of image forming units 106Y, 106M, 106C, and 106K has a common internal configuration although the colors of formed toner images are different from one another. The image forming unit 106K forms a black image, the image forming unit 106M forms a magenta image, the image forming unit 106C forms a cyan image, and the image forming unit 106Y forms a yellow image. In addition, in the following description, the image forming unit 106Y will be specifically described. The other image forming units 106M, 106C, and 106K are similar to the image forming unit 106Y. Thus, the components of the image forming unit 106M, 106C, or 106K are only illustrated in
The conveyance belt 105 is an endless belt stretched around a driving roller 107 that is to be rotationally driven and a driven roller 108. The driving roller 107 is rotationally driven by a drive motor. The drive motor, the driving roller 107, and the driven roller 108 function as a driver for moving the conveyance belt 105 serving as an endless moving device.
During image formation, the first image forming unit 106Y transfers a yellow toner image onto the rotationally-driven conveyance belt 105. The image forming unit 106Y includes, for example, a photoconductor drum 109Y serving as a photoconductor, and a charging device 110Y, an optical writing device 111, a developing device 112Y, a photoconductor cleaner 113Y that are arranged around the photoconductor drum 109Y. The optical writing device 111 irradiates the photoconductor drums 109Y, 109M, 109C, and 109K (hereinafter, collectively referred to as a “photoconductor drum 109”) with light.
In image formation, the outer circumferential surface of the photoconductor drum 109Y is uniformly charged by the charging device 110Y in the dark, and then, writing is performed using light from the optical writing device 111 that is emitted from a light source corresponding to a yellow image, so that an electrostatic latent image is formed. The developing device 112Y visualizes the electrostatic latent image as a visible image, using yellow toner. Through the process, a yellow toner image is formed on the photoconductor drum 109Y.
This toner image is transferred onto the conveyance belt 105 by the function of a transfer device 115Y, at a position where the photoconductor drum 109Y and the conveyance belt 105 come into contact with each other or come closest to each other (transfer position). Through the transfer, a yellow toner image is formed on the conveyance belt 105. When the toner image transfer is completed, unnecessary toner remaining on the outer circumferential surface of the photoconductor drum 109Y is swept away by the photoconductor cleaner 113Y, and then, the photoconductor drum 109Y stands by for next image formation.
The yellow toner image that has been transferred onto the conveyance belt 105 by the image forming unit 106Y in the above-described manner is conveyed to the next image forming unit 106M by the roller driving of the conveyance belt 105. In the image forming unit 106M, a magenta toner image is fainted on the photoconductor drum 109M through a process similar to an image forming process in the image forming unit 106Y. Then, the magenta toner image is transferred to be superimposed onto the already-formed yellow image.
The yellow and magenta toner images transferred onto the conveyance belt 105 are further conveyed to the next image forming units 106C and 106K. Through similar operations, a cyan toner image formed on the photoconductor drum 109C and a black toner image formed on the photoconductor drum 109K are transferred to be superimposed onto the already-transferred images. In this manner, a full color intermediate transfer image is formed on the conveyance belt 105.
The sheets 104 stored in the sheet feeding tray 101 are sequentially fed from the uppermost sheet 104, and the intermediate transfer image formed on the conveyance belt 105 is transferred onto the surface of the fed sheet 104 at a position where a conveyance path of the sheet 104 comes into contact with or comes closest to the conveyance belt 105. Through the process, an image is formed on the surface of the sheet 104. The sheet 104 having the image formed on its surface is further conveyed, and the image is fixed by a fixing device 116. Then, the sheet 104 is discharged to the outside of the image forming apparatus 1.
In addition, a belt cleaner 118 is provided for removing toner remaining on the conveyance belt 105 without being transferred onto the sheet 104. As illustrated in
When one print job is completed in this manner, the optical writing device 111 performs a discharge process. In the discharge process, the optical writing device 111 exposes the entire surfaces of the photoconductor drums 109 of the respective colors to eliminate electric charge remaining on the surfaces of the photoconductor drums 109 from which the toner images have been transferred.
In addition, an intermediate transfer method of transferring the images formed on the conveyance belt 105, onto the sheet 104 has been described as an example with reference to
Next, the optical writing device 111 according to this embodiment will be described.
Each of the LEDAs 132 serves as a light emission element array including a plurality of LED elements serving as light emission elements that is arrayed in the same direction as the direction in which a corresponding LEDA 132 is arrayed. Each LED element included in each of the LEDAs 132 performs irradiation corresponding to one pixel.
In addition, a plurality of driving circuits 133 for driving the respective LEDAs 132 to emit light is provided within the substrate 131. The driving circuits 133 correspond to the respective LEDAs 132 on a one-to-one basis.
Based on rendering information input from the controller 20, a controller included in the optical writing device 111 controls, for each main scanning line, the lighted lunminated state of each of LEDs arranged in the LEDA print head 130 in the main scanning direction. As a result, the surface of the photoconductor drum 109 is selectively exposed, so that an electrostatic latent image is formed thereon.
As illustrated in
In addition, as illustrated in
In the process, if light emission driving periods of the LEDA print heads 130 corresponding to different colors overlap with one another, the amount of power required in the overlapped period further increases. Thus, as illustrated in
In such a configuration, the optical writing device 111 controls to reduce the instantaneous consumed amount of current in the above-described discharge process. The control mode in the discharge process will be described below.
As illustrated in
In contrast,
In the case illustrated in
To cope with such a problem, control called time division driving is performed in some cases. In the time division driving, all the LED elements included in the LEDA print head 130 are divided into a plurality of groups, and light emission driving is performed at timings different for each group in one line cycle. According to the time division driving, the number of LED elements simultaneously turned on corresponds to the number of LED elements included in one group. Thus, the instantaneous consumed amount of current can be reduced.
In the case of the time division driving, however, there is a disadvantage in that, by performing light emission driving at different timings, respective irradiation positions on the photoconductor drum 109 of pixels included in an image corresponding to one line become different for each group. In contrast, in the case of the discharge process, a problem of an irradiation position shift does not occur because it is sufficient that the surface of the photoconductor drum 109 is exposed.
In other words, in the case of the discharge process, only an advantage of reducing the instantaneous consumed amount of current can be obtained without regard to the disadvantage in the time division driving. It is therefore considered that the control of concurrently turning on LED elements corresponding to one line is performed during the exposure for image formation output, and the time division driving is employed during the discharge process.
Nevertheless, in the case of employing a method of switching a light emission driving mode between the image formation output and the discharge process, the configuration for controlling the LEDA print head 130 is complicated in the optical writing device 111. Thus, in this embodiment, a method for reducing the instantaneous consumed amount of current without using the time division driving will be described.
Consequently, as illustrated in
To avoid such a problem, the optical writing device 111 extends a strobe period during which each LED element is driven to emit light in the discharge process. A basic light emission driving timing is as described above with reference to
In contrast, in the discharge process, as illustrated in
As illustrated in
In the example illustrated in
A control mode is switched between the control mode illustrated in
In contrast, in the case of alternately controlling LED elements to light up, the number of light emission drivings becomes inconsistent between LED elements controlled to light up and LED elements not controlled to light up during the discharging. This consequently generates a difference in time degradation. When there arises a difference in state among LED elements included in the same LEDA print head 130, even if the LED elements are driven under the same condition, light emission amounts become different from one another. As a result, a difference in image density is generated on a main scanning line.
In addition, in the case of alternately controlling LED elements to light up in a similar manner, as illustrated in
In contrast, by using a mode while switching between the mode illustrated in
As described above, the discharge exposure is executed by the optical writing device 111 every time one job is completed. It is therefore considered that a mode is switched in such a manner that the mode in
In addition, by employing the mode illustrated in
In this manner, the exposure energies applied by the surrounding LED elements driven to emit light decrease according to a distance from the LED elements driven to emit light.
In each of
In this case, when a distance between adjacent LED elements is set to “1”, in the case illustrated in
In the example illustrated in
According to the example illustrated in
It is therefore preferable to select an optimum light emission pattern from among those illustrated in
On the other hand, as described above, in the example illustrated in
On the other hand, an exposure energy may be adjusted by a strobe period. More specifically, in a case in which an exposure energy at the position indicated by the star sign exceeds 100% as in the example illustrated in
Next, control blocks of the optical writing device 111 according to this embodiment will be described with reference to
As illustrated in
In this manner, similarly to the hardware configuration described with reference to
The LEDA writing controller 210 serves as a control circuit for controlling the light emission of the LEDA print head 130 based on rendering information input from the controller 20, and includes an integrated circuit and the like. The LEDA writing controller 210 operates according to the control of the CPU 202.
The frequency converter 211 outputs the rendering information input from the controller 20, in accordance with an operating frequency of the LEDA writing controller 210. Thus, the frequency converter 211 temporarily stores the rendering information input from the controller 20, into the line memory 204 provided for frequency conversion, and outputs the rendering information in accordance with an operating frequency of the LEDA writing controller 210. The frequency converter 211 also functions as an image information acquisition unit for acquiring image information input from the controller 20.
The image processor 212 performs various types of image processing on image data that has been output after having been subjected to the frequency conversion. Examples of image processing performed by the image processor 212 include image size change, trimming processing, the addition of an internal pattern, and the like. In addition, the image processor 212 performs binarization processing of converting the rendering information input from the frequency converter 211 as multi-tone image information, into a duotone of chromatic and achromatic, and finally generating pixel information for performing light emission control of the LEDA print head 130.
Furthermore, in the discharge process, the image processor 212 generates data for performing thinned-out lighting control of LED elements (may be referred to as the “discharge data”) as described with reference to
In the discharge process, the image processor 212 generates data for realizing the lighting states as illustrated in
The skew corrector 213 corrects the skew of an image that arises from various factors such as an arrangement error of the LEDA print head 130 and the photoconductor drum 109. Parameter values related to skew correction are stored in a storage device included in the optical writing controller 201, and are set in the skew corrector 213 according to the control of the CPU 202. The skew corrector 213 stores image data input from the image processor 212, into the line memory 205 for each main scanning line, and reads the image data from the line memory 205 according to the set parameter values to execute skew correction.
In a state in which pixel data corresponding to a plurality of main scanning lines are stored in the line memory 205, the skew corrector 213 shifts a line from which pixel data is to be read, at a predetermined position on a main scanning line, according to the skew of an image that is to be corrected. For example, when pixel data is read from the first line, at a predetermined position on a main scanning line (hereinafter, referred to as a “shift position”), the main scanning line from which pixel data is read is switched to the second line. Through such a process, the skew of the image can be corrected.
In addition, as described above, data for realizing the lighting state as illustrated in
The omission of skew correction is realized by, for example, setting a parameter indicating non-existence of skew, as a parameter set by the CPU 202 as described above. As a result, the skew corrector 213 directly reads image data written into the line memory 205. Thus, an image shift in the sub-scanning direction is not performed.
In addition, data may be directly input to the LEDA controller 214 by bypassing the skew corrector 213.
Based on pixel information output from the skew corrector 213, the LEDA controller 214 controls the light emission of the LEDA print head 130 according to an operating frequency. In other words, the LEDA controller 214 functions as a light source controller.
As illustrated in
Next, specific configurations of the LEDA controller 214 and the LEDA print head 130 will be described with reference to
The register 301 is a storage for storing parameter values set by the CPU 202. Based on a reference clock CLK input from the outside of the LEDA controller 214, the signal generator 302 generates and outputs a line cycle signal LSYNC indicating a light emission cycle of the LEDA print head 130 of each main scanning line. The LSYNC corresponds to a main scanning synchronization signal indicating the cycle of each main scanning line. The signal generator 302 generates and outputs the LSYNC for each color of CMYK.
The data transfer unit 303 transfers, to the LEDA print head 130, image data DATA input from the skew corrector 213, according to the timing of the LSYNC input from the signal generator 302. The data transfer units 303 are provided so as to correspond to the respective LEDA print heads 130 of the respective colors of CMYK. In addition, the skew corrector 213 inputs image data DATA of the respective colors of CMYK to the data transfer units 303 corresponding to the respective colors.
According to the timing of the LSYNC input from the signal generator 302, the light emission controller 304 outputs a strobe signal STRB for performing light emission control of the LEDA print head 130. The light emission controllers 304 are provided so as to correspond to the respective LEDA print heads 130 of the respective colors of CMYK. Thus, the signal generator 302 outputs LSYNCs generated for the respective colors of CMYK, to the light emission controllers 304 corresponding to the respective colors.
At this time, in normal image formation output, the light emission controllers 304 each output the strobe signal STRB in the mode illustrated in
In the LEDA print head 130 of each color of CMYK, a light emission signal input unit 135 acquires the STRB input from the light emission controller 304, and inputs the STRB to the driving circuits 133 corresponding to the respective LEDAs 132.
A data signal DATA input from the data transfer unit 303 is acquired by an image data input unit 134 in the LEDA print head 130, and input to the driving circuits 133 corresponding to the respective LEDAs 132. The image data input unit 134 develops the data signal DATA input as serial data, into parallel data. Thus, the image data input unit 134 includes, for example, a shift register.
Based on the DATA input from the image data input unit 134, the driving circuits 133 switch the lighted/unlighted state of a plurality of LED elements included in the LEDAs 132, and drive the LEDAs 132 to emit light, according to the strobe signal STRB input from the light emission signal input unit 135.
In the discharge process, the data signal DATA of the image data corresponding to the lighting control for the discharge process that has been generated by the image processor 212 as described above is transferred from the data transfer unit 303 to the image data input unit 134. The data is input from the image data input unit 134 to the driving circuits 133, so that the lighting states as illustrated in
As described above, in an image forming apparatus equipped with an optical writing device, a discharge process is performed by a linear light source for performing optical writing. During the discharge process, thinned-out lighting control of thinning out, at equal intervals, LED elements caused to emit light is performed for reducing the instantaneous consumed amount of current.
To avoid a state in which sufficient exposure cannot be performed because exposure energies applied to the surface of the photoconductor drum 109 become insufficient due to such thinned-out lighting control, a strobe period in one lighting control is made longer than that in normal image formation output. Such a mode enables both sufficient discharge exposure and the reduction of the instantaneous consumed amount of current in the discharge process.
In addition, in the above-described embodiment, the description has been given of an example case of setting a strobe period in the discharge process to the double of a strobe period in the normal image formation output. This, however, is an example. It is preferable to extend the strobe period without excess and deficiency to such an extent that the shortage in exposure energy that is caused by thinned-out lighting control can be compensated for.
Thus, if the doubled strobe period is not sufficient, a strobe period exceeding the doubled strobe period needs to be set. On the other hand, one exposure needs to be finished within one line cycle, and exposures for four colors of CMYK need to be finished within one line cycle as illustrated in
In addition, in the above-described embodiment, alternate lighting control of turning on either odd-numbered elements or even-numbered elements as illustrated in
As an example of another mode, the following modes can be employed. One example mode performs control so as to turn off one element every time causing two elements to emit light, in the main scanning direction. Another example mode similarly performs control so as to turn off four elements after causing four elements to emit light. The control mode is not limited to these modes, and any mode can be realized as long as the mode has a configuration in which groups of LED elements caused to emit light and groups of LED elements caused not to emit light are periodically arranged.
Nevertheless, by employing alternate lighting control, exposure energies at positions corresponding to turned-off LED elements can be compensated for by exposure energies applied by LED elements arranged on the both sides of the turned-off LED elements. As a result, the above-described supplementation of exposure energies by extending a strobe period can be suitably achieved.
While the above-described embodiment is an example of performing optical writing using a linear light source, the following second embodiment is an example of performing optical writing using a rotating reflection light source operated by reflection on a polygon mirror. In addition, the technical features described with reference to
As illustrated in
The laser beams emitted from the LD light sources 281 are reflected by a reflecting mirror 280. The laser beams are guided to respective mirrors 282BK, 282Y, 282M, and 282C (hereinafter, collectively referred to as a mirror 282) through an optical system such as an fθ lens (not illustrated), and further through an optical system provided ahead thereof, the laser beams are scanned over the surfaces of the respective photoconductor drums 109BK, 109M, 109C, and 109Y.
The reflecting mirror 280 is a hexahedral polygon mirror. By rotating, the reflecting mirror 280 can scan a laser beam corresponding to a line in the main scanning direction for each surface of the polygon mirror. The optical writing device 111 divides four light source devices into two each including light source devices of two colors, i.e., the LD light sources 281BK and 281Y, and the LD light sources 281M and 281C, and performs scanning using different reflection surfaces of the reflecting mirror 280. This enables simultaneous writing onto four different photoconductor drums, with a more compact configuration than that in a method of performing scanning using only one reflection surface.
In addition, a horizontal synchronization detection sensor 283 is provided near a scanning start position in a range in which the laser beams are scanned by the reflecting mirror 280. When a laser beam emitted from the LD light source 281 enters the horizontal synchronization detection sensor 283, the timing of a scanning start position of a main scanning line is detected, so that a control device for controlling the LD light source 281 and the reflecting mirror 280 are synchronized.
Meanwhile, as illustrated in
In addition, by performing the discharge process while maintaining the rotating speed of the photoconductor drum 109 in the print output, the downtime of the image forming apparatus 1 that is caused by the discharge process can be minimized.
Next, a relationship between an arrangement state of an exposure spot on the photoconductor drum 109, and an exposure energy will be described.
In addition,
As illustrated in
In the case illustrated in
In contrast,
In the case illustrated in
In the case illustrated in
Thus, also in the mode illustrated in
In normal print output, for higher image quality and finer skew correction of an image, the optical writing device 111 performs lighting control of the light source devices using high resolution as illustrated in
In the case of the linear light source illustrated in
Thus, in the case of using a rotating reflection light source, the optical writing device 111 adjusts the resolution in the sub-scanning direction by thinning out main scanning lines.
As illustrated in
Next, control blocks of the optical writing device 111 will be described with reference to
As illustrated in
In this manner, similarly to the hardware configuration described with reference to
The writing controller 210a serves as a control circuit for controlling the light emission of the LEDA print head 130 and the LD light source 281 based on rendering information input from the controller 20, and includes an integrated circuit and the like. The writing controller 210a operates according to the control of the CPU 202.
The frequency converter 211 outputs the rendering information input from the controller 20, in accordance with an operating frequency of the writing controller 210a. Thus, the frequency converter 211 temporarily stores the rendering information input from the controller 20, into the line memory 204 provided for frequency conversion, and outputs the rendering information in accordance with an operating frequency of the writing controller 210a. The frequency converter 211 also functions as an image information acquisition unit for acquiring image information input from the controller 20.
The image processor 212 performs various types of image processing on image data that has been output after having been subjected to the frequency conversion. Examples of image processing performed by the image processor 212 include image size change, trimming processing, the addition of an internal pattern, and the like. In addition, the image processor 212 performs binarization processing of converting the rendering information input from the frequency converter 211 as multi-tone image information, into a duotone of chromatic and achromatic, and finally generating pixel information for performing light emission control of the LEDA print head 130 or the LD light source 281.
Furthermore, in the discharge process, the image processor 212 generates data for turning on LED elements or the LD light sources 281 for the discharge process (hereafter, referred to as “discharge data”). In the discharge process, the discharge energy E0 is applied to the entire surface of the photoconductor drum 109. Thus, the discharge data is, for example, a solid image.
On the other hand, the discharge data does not have to be a solid image as long as the discharge energy E0 can be obtained from exposure energies corresponding to adjacent pixels as described above with reference to
The skew corrector 213 corrects the skew of an image that arises from various factors such as an arrangement error of the LEDA print head 130 and the photoconductor drum 109 and an arrangement error of the LD light source 281 and the reflecting mirror 280. Parameter values related to skew correction are stored in a storage device included in the optical writing controller 201, and are set in the skew corrector 213 according to the control of the CPU 202. The skew corrector 213 stores image data input from the image processor 212, into the line memory 205 for each main scanning line, and reads the image data from the line memory 205 according to the set parameter values to execute skew correction.
In a state in which pixel data corresponding to a plurality of main scanning lines are stored in the line memory 205, the skew corrector 213 shifts a line from which pixel data is to be read, at a predetermined position on a main scanning line, according to the skew of an image that is to be corrected. For example, when pixel data is read from the first line, at a predetermined position on a main scanning line (hereinafter, referred to as a “shift position”), the main scanning line from which pixel data is read is switched to the second line. Through such a process, the skew of the image can be corrected.
In addition, as described above, the discharge data generated by the image processor 212 in the discharge process is also input from the image processor 212 to the skew corrector 213 in a similar manner to normal image data. Nevertheless, it is not necessary to perform skew correction in the discharge process. Thus, in the discharge process, the control of omitting skew correction performed by the skew corrector 213 is preferable.
The omission of skew correction is realized by, for example, setting a parameter indicating non-existence of skew, as a parameter set by the CPU 202 as described above. As a result, the skew corrector 213 directly reads image data written into the line memory 205. Thus, an image shift in the sub-scanning direction is not performed. In addition, data may be directly input to the lighting controller 215 by bypassing the skew corrector 213.
Based on pixel information output from the skew corrector 213, the lighting controller 215 controls the light emission of the LEDA print head 130 or the LD light source 281 according to an operating frequency. In other words, the lighting controller 215 functions as a light source controller.
Next, a specific configuration of the lighting controller 215 will be described.
The register 301 is a storage for storing parameter values set by the CPU 202. Based on a reference clock CLK input from the outside of the lighting controller 215, the signal generator 302 generates and outputs a line cycle signal LSYNC indicating a light emission cycle of the LEDA print head 130 of each main scanning line. The LSYNC corresponds to a main scanning synchronization signal indicating the cycle of each main scanning line. The signal generator 302 generates and outputs the LSYNC for each color of CMYK.
Here, the cycle of the LSYNC output by the signal generator 302 is a cycle corresponding to
The data transfer unit 303 transfers, to the LEDA print head 130, image data DATA input from the skew corrector 213, according to the timing of the LSYNC input from the signal generator 302. The data transfer units 303 are provided so as to correspond to the respective LEDA print heads 130 of the respective colors of CMYK. In addition, the skew corrector 213 inputs image data DATA of the respective colors of CMYK to the data transfer units 303 corresponding to the respective colors.
According to the timing of the LSYNC input from the signal generator 302, the light emission controller 304 outputs a strobe signal STRB for performing light emission control of the LEDA print head 130. The light emission controllers 304 are provided so as to correspond to the respective LEDA print heads 130 of the respective colors of CMYK. Thus, the signal generator 302 outputs LSYNCs generated for the respective colors of CMYK, to the light emission controllers 304 corresponding to the respective colors.
In the LEDA print head 130 of each color of CMYK, a light emission signal input unit 135 acquires the STRB input from the light emission controller 304, and inputs the acquired STRB to the driving circuits 133 corresponding to the respective LEDAs 132.
A data signal DATA input from the data transfer unit 303 is acquired by an image data input unit 134 in the LEDA print head 130, and input to the driving circuits 133 corresponding to the respective LEDAs 132. The image data input unit 134 develops the data signal DATA input as serial data, into parallel data. Thus, the image data input unit 134 includes, for example, a shift register.
Based on the DATA input from the image data input unit 134, the driving circuits 133 switch the lighted/unlighted state of a plurality of LED elements included in the LEDAs 132, and drive the LEDAs 132 to emit light, according to the strobe signal STRB input from the light emission signal input unit 135.
In the discharge process, the data signal DATA of the image data corresponding to the lighting control for the discharge process that has been generated by the image processor 212 as described above is transferred from the data transfer unit 303 to the image data input unit 134. The data is input from the image data input unit 134 to the driving circuits 133, and the light emission controller 304 outputs the STRB based on the LSYNC adjusted according to the setting performed in the register 301. Through the process, the lighting states as illustrated in
According to a pixel clock input from the pixel clock generator 410, the LD controller 401 performs lighting control of the LD light source 281 based on pixel data input from the skew corrector 213. The polygonal motor controller 402 controls the reflecting mirror 280 to rotate. The LD controller 401 and the polygonal motor controller 402 each perform the above-described control according to the setting values written by the CPU 202 in the register 403.
The synchronization detection lighting controller 404 inputs a lighting signal to the LD controller 401 for forcibly turning on the LD light source 281 at a timing when a laser beam reflected by the reflecting mirror 280 enters the horizontal synchronization detection sensor 283. At first, the synchronization detection lighting controller 404 forcibly turns on the LD controller 401 to acquire a signal from the horizontal synchronization detection sensor 283, thereby identifying the cycle of a horizontal synchronization detection signal from the horizontal synchronization detection sensor 283. Thereafter, the synchronization detection lighting controller 404 inputs a lighting signal to the LD controller 401 according to the cycle of the horizontal synchronization detection signal that has been identified in this manner.
The pixel clock generator 410 includes a reference clock generator 411, a voltage controlled oscillator (VCO) clock generator 412, and a phase synchronization clock generator 413. In addition, using these functions, the pixel clock generator 410 generates a pixel clock for the LD controller 401 performing lighting control corresponding to each pixel on one main scanning line.
The reference clock generator 411 generates and outputs a reference clock based on the setting value written by the CPU 202 in the register 403. The VCO clock generator 412 generates and outputs a VCO clock based on the reference clock. The phase synchronization clock generator 413 synchronizes the VCO clock with a horizontal synchronization signal input from the horizontal synchronization detection sensor 283, and outputs the resultant clock as a pixel clock.
In such a configuration, in either odd-numbered main scanning lines or even-numbered main scanning lines, the LD controller 401 does not turn on the LD light sources 281 irrespective of pixel data input from the skew corrector 213, as described with reference to
In addition, an adjustment amount of the resolution in the sub-scanning direction in the case of using the rotating reflection light source is not limited to the above-described mode of turning off either odd-numbered main scanning lines or even-numbered main scanning lines, i.e., the mode of halving the resolution. For example, in the case of turning on only one line in three lines, the resolution in the sub-scanning direction can be controlled to be one-third.
In the case of using the rotating reflection light source in this manner, by setting, in the register 403, a frequency of lighting up the LD light sources 281 for each main scanning line, the lighting controller 215 can control the resolution in the sub-scanning direction to be one-integer-th of the original resolution.
As illustrated in
Thus, based on a charging bias applied to the photoconductor drum 109 by the charging device 110, the CPU 202 calculates such a resolution in the sub-scanning direction that the discharge energy E0 is satisfied on the entire surface of the photoconductor drum 109. Then, based on the calculation result, the CPU 202 sets the resolution in the sub-scanning direction, in the register 301 or 403 of the lighting controller 215.
In the above-described calculation of the resolution in the sub-scanning direction, as illustrated in
The CPU 202 then sets the resolution R in the sub-scanning direction that has been obtained by the above-described Formula (1), in the register 301 or 403. As a result, the resolution in the sub-scanning direction in the discharge process is changed by the function described with reference to
As described above, in an image forming apparatus equipped with an optical writing device, the optical writing device executes exposure for discharging, and a resolution adjusted to be lower than that in a normal print process is set as a resolution in the sub-scanning direction in the discharge process. The resolution adjusted to be lower is set so that the discharge energy E0 can be obtained on the entire surface of the photoconductor drum 109, considering that the discharge energy E0 is satisfied by the superimposition of exposure energies obtained by different pixels as described with reference to
With this configuration, the amount of consumed power can be reduced while keeping an exposure energy required for discharging. The present invention is applicable to any of the case of using a linear light source and the case of using a rotating reflection light source as described above, as long as such control can be performed. Thus, the reduction in the amount of power consumed in the case of performing a discharge process of a photoconductor using an optical writing device for forming an electrostatic latent image can be achieved irrespective of the type of a light source device.
In addition, at the end of each print job, a discharge process is executed while maintaining the rotating speed of the photoconductor drum 109. Thus, the downtime of an apparatus that is caused by the discharge process can be minimized while maintaining a discharge effect.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-052463 | Mar 2015 | JP | national |
| 2015-240334 | Dec 2015 | JP | national |
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