Patent Application
20190243275
The present invention relates to an information processing apparatus that corrects image data, and to an image forming apparatus including the information processing apparatus.
An electrophotographic image forming apparatus forms an electrostatic latent image on a photosensitive member by using an exposure apparatus to expose the photosensitive member that is charged. The exposure apparatus scans the photosensitive member by rotating a polygon mirror to deflect light from a light source. A beam detect (BD) sensor that detects light upstream from the photosensitive member is arranged along the scanning direction of the light (a main scanning direction). The BD sensor outputs a main scanning synchronization signal (BD signal) indicating the timing at which the light has been detected, and determines the timing at which the electrostatic latent image is written onto the photosensitive member with light on the basis of the BD signal.
If noise intermixes with the BD signal, the position in the main scanning direction may shift and produce distortion in the image to be formed. Japanese Patent Laid-Open No. 2017-37260 discloses a configuration that provides an interval, after the BD signal is detected, where the BD signal is not recognized for a predetermined period, which results in the intermixing noise being cut during that interval. The predetermined period is set on the basis of, for example, the shortest scanning period among scanning periods corresponding to a plurality of reflective surfaces. Specifically, an amount of time equivalent to 90% of the shortest scanning period is set as the predetermined period, for example.
The shapes of the surfaces of the polygon mirror that deflects the light differ from surface to surface. When the shapes of the surfaces differ from surface to surface, the amount of time from when the BD signal falls to when the BD signal falls for the first time after the stated fall (that is, the scanning period) differs for each reflective surface of the polygon mirror. If the predetermined period, that is, the period in which the BD signal is not recognized, is set as described in Japanese Patent Laid-Open No. 2017-37260, the period when the BD signal is not recognized in the longest scanning period, among the scanning periods corresponding to the plurality of reflective surfaces, will be shorter than a time equivalent to 90% of that longest scanning period. As a result, when detecting the fall of the BD signal, an erroneous detection may occur due to noise contained in the BD signal. The image that is formed may become distorted as a result.
According to an aspect of the present invention, an information processing apparatus connected with an image forming apparatus including an image forming unit is provided. The image forming unit includes a first receiver configured to receive image data; a photosensitive member; a light source configured to emit light based on the image data received by the first receiver; a rotating polygonal mirror, having a plurality of reflective surfaces that reflect the light emitted by the light source, configured to scan the photosensitive member by being rotationally driven to deflect the light; and a light-receiving unit configured to receive the light reflected by the rotating polygonal mirror and output a predetermined signal having a first level and a second level in response to a reception of the light. The information processing apparatus includes: a second receiver configured to receive the predetermined signal; a detector configured to detect a change from the first level to the second level in the predetermined signal received by the second receiver; a specifier configured to specify a reflective surface, among the plurality of reflective surfaces, used to scan the photosensitive member, based on a timing at which the change is detected by the detector; a corrector configured to correct image data corresponding to each of a plurality of scanning lines constituting an image equivalent to one surface's worth of a recording medium, using correction data corresponding to the reflective surface corresponding to each scanning line; and an output unit configured to output the image data corrected by the corrector to the image forming unit in response to the detector detecting the change. The detector is further configured to, in a period until the specifier specifies the reflective surface, detect the change after a predetermined amount of time has passed after the change has been detected, and after the specifier has specified the reflective surface, detect the change after an amount of time based on the specified reflective surface has passed after the change has been detected.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. It should be noted, however, that the shapes, relative dispositions, and so on of the constituent elements described in these embodiments are to be changed as appropriate depending on the configurations, conditions, and so on of the apparatus to which the invention is applied, and the scope of the invention is not intended to be limited to the embodiments described hereinafter.
Image Forming Operations
Light reflected by a document irradiated by an illumination lamp 703 at a reading position of the reader 700 is guided to a color sensor 706 by an optical system constituted by reflecting mirrors 704A, 704B, and 704C and a lens 705. The reader 700 reads each of the colors blue (“B”, hereinafter), green (“G”, hereinafter), and red (“R”, hereinafter) of the light incident on the color sensor 706, and converts the light into electrical image signals. Furthermore, the reader 700 obtains image data by carrying out a color conversion process on the basis of the intensities of the B, G, and R image signals, and outputs that image data to an image control unit 1007 (mentioned later; see
A sheet holding tray 718 is provided within the image printing device 701. A recording medium held in the sheet holding tray 718 is fed out by a paper feed roller 719, and is conveyed to registration rollers 723, which are in a stopped state, by conveyance rollers 722, 721, and 720. A leading end of the recording medium conveyed by the conveyance rollers 720 in a conveyance direction contacts a nip part of the registration rollers that are in a stopped state. With the leading end of the recording medium in contact with the nip part of the registration rollers 723 that are in a stopped state, the conveyance rollers 720 convey the recording medium even further, which causes the recording medium to flex. As a result, elastic force acts on the recording medium, and the leading end of the recording medium makes contact along the nip part of the registration rollers 723. This corrects skew in the recording medium. After the skew in the recording medium has been corrected, the registration rollers 723 begin conveyance of the recording medium at a timing that will be described later. Note that the recording medium is any medium on which an image can be formed by the image forming apparatus, including paper, a resin sheet, cloth, an OHP sheet, a label, and the like, for example.
The image data obtained by the reader 700 is corrected by the image control unit 1007 and input to a laser scanner unit 707, which includes a laser and a polygon mirror. The outer circumferential surface of a photosensitive drum 708 is charged by a charger 709. After the outer circumferential surface of the photosensitive drum 708 has been charged, the outer circumferential surface of the photosensitive drum 708 is irradiated by the laser scanner unit 707 with a laser beam based on the image data input to the laser scanner unit 707. As a result, an electrostatic latent image is formed on a photosensitive layer covering the outer circumferential surface of the photosensitive drum 708 (a photosensitive member). Note that the configuration through which the electrostatic latent image is formed on the photosensitive layer by the laser beam will be described later.
Next, the electrostatic latent image is developed using toner within a developer 710, and a toner image is formed on the outer circumferential surface of the photosensitive drum 708. The toner image formed on the photosensitive drum 708 is transferred to the recording medium by a transfer charger 711 provided in a position opposite the photosensitive drum 708 (a transfer position). Note that the registration rollers 723 feed the recording medium to the transfer position in accordance with the timing at which the toner image is transferred to a predetermined position on the recording medium. The recording medium, onto which the toner image has been transferred as described above, is fed to a fixer 724, and the toner image is fixed onto the recording medium by being heated and pressed by the fixer 724. The recording medium onto which the toner image has been fixed is discharged to a discharge tray 725 outside the apparatus. An image is formed on the recording medium by the image forming apparatus 100 in this manner. The foregoing has described the configuration and functions of the image forming apparatus 100.
Configuration for Forming Electrostatic Latent Image
Optical Scanning Device
As illustrated in
On the other hand, the laser beam emitted from the other end of the laser light source 1000 passes through a collimator lens 1001 and irradiates the polygon mirror 1002, which is a rotating polygonal mirror. The polygon mirror 1002 is rotationally driven by a polygon motor (not shown). The polygon motor is controlled by a drive signal (Acc/Dec) output from the engine control unit 1009. The laser beam with which the rotating polygon mirror 1002 is irradiated is deflected by the polygon mirror 1002. The scanning of the outer circumferential surface of the photosensitive drum 708 by the laser beam deflected by the polygon mirror 1002 progresses from the right to the left in
The laser beam deflected by the polygon mirror 1002 is incident on a beam detect (BD) sensor 1004, which functions as a light-receiving unit including a light-receiving element that receives the laser beam. In the present embodiment, the BD sensor 1004 is disposed at a position that ensures that the outer circumferential surface of the photosensitive drum 708 is irradiated by the laser beam after the BD sensor 1004 has detected the laser beam, in a period spanning from when the BD sensor 1004 detects the laser beam to when the BD sensor 1004 detects the laser beam again. Specifically, the BD sensor 1004 is disposed, for example, in a part of the region through which the laser beam reflected by the polygon mirror 1002 passes which is outside a region indicated by an angle α and which is on the upstream side in the direction of the scanning by the laser beam, as illustrated in
The BD sensor 1004 generates the BD signal on the basis of the detected laser beam and outputs the generated signal to the engine control unit 1009. On the basis of the input BD signal, the engine control unit 1009 controls the polygon motor so that a rotation period of the polygon mirror 1002 matches a predetermined period. The engine control unit 1009 determines that the rotation period of the polygon mirror 1002 matches the predetermined period when the period of the BD signal becomes a period corresponding to the predetermined period.
The engine control unit 1009 outputs an image creation BD signal (a timing signal) to the image control unit 1007 in accordance with the input BD signal. The image creation BD signal is a signal synchronized with the BD signal, and corresponds to a signal indicating one scanning period in which the laser beam scans the photosensitive drum 708. The image control unit 1007 outputs corrected image data to the laser control unit 1008 in accordance with the input image creation BD signal. Note that the detailed control configurations of the engine control unit 1009 and the image control unit 1007 will be described later.
The laser control unit 1008 causes the laser light source 1000 to light up on the basis of the input image data, thus generating the laser beam for forming an image on the outer circumferential surface of the photosensitive drum 708. In this manner, the laser control unit 1008 is controlled by the image control unit 1007, which is an information processing apparatus. The outer circumferential surface of the photosensitive drum 708 is irradiated with the generated laser beam through the above-described method.
A distance L from the position where a sheet sensor 726 detects the recording medium to the transfer position is longer than a distance x from the position on the outer circumferential surface of the photosensitive drum 708 irradiated by the laser beam to the transfer position with respect to the rotation direction of the photosensitive drum 708. Specifically, the distance L is a distance obtained by adding, to the distance x, a distance by which the recording medium is conveyed during a period spanning from when the sheet sensor 726 detects the leading end of the recording medium to when the laser beam is emitted from the laser light source 1000. Note that image data correction is carried out by the image control unit 1007, the laser control unit 1008 is controlled by the image control unit 1007, and so on in the period spanning from when the sheet sensor 726 detects the leading end of the recording medium to when the laser beam is emitted from the laser light source 1000. The foregoing has been a description of the configuration of the optical scanning device.
Method for Specifying Polygon Mirror Surface
The image control unit 1007 outputs the corrected image data to the laser control unit 1008, in order from the image data furthest upstream in the sub scanning direction, in accordance with the period of the image creation BD signal that has been input. The laser control unit 1008 forms an image on the outer circumferential surface of the photosensitive drum 708 by controlling the laser light source 1000 in accordance with the input image data. Although the polygon mirror 1002 has four surfaces in the present embodiment, it should be noted that the number of surfaces in the polygon mirror 1002 is not limited to four.
The image formed on the recording medium is formed by the laser beam deflected by the plurality of reflective surfaces of the polygon mirror 1002. Specifically, as illustrated in
When a polygon mirror having four reflective surfaces is used as the polygon mirror for deflecting the laser beam, the angle formed by two adjacent reflective surfaces of the polygon mirror 1002 may not be a perfect 90° angle. Specifically, viewed from the rotation axis direction of the polygon mirror having four reflective surfaces, the angle formed by two adjacent sides may not be a perfect 90° angle (that is, the shape of the polygon mirror as viewed from the rotation axis direction may not be a perfect square). Note that when a polygon mirror having n reflective surfaces (where n is a positive integer) is used, the shape of the polygon mirror as viewed from the rotation axis direction may not be a perfect n-sided polygon.
When a polygon mirror having four reflective surfaces is used, and the angle formed by two adjacent reflective surfaces of the polygon mirror is not a perfect 90° angle, the position, size, and so on of the image formed by the laser beam will differ from reflective surface to reflective surface. As a result, the image formed on the outer circumferential surface of the photosensitive drum 708 will become distorted, and distortion will also arise in the image formed on the recording medium.
Accordingly, in the present embodiment, the image data is corrected (writing position correction or the like) on the basis of a correction amount (correction data) corresponding to each of the plurality of reflective surfaces of the polygon mirror 1002. In this case, it is necessary to provide a configuration for specifying the surface by which the laser beam is deflected. An example of a method for specifying the surface by which the laser beam is deflected will be described hereinafter. In the present embodiment, a surface specifying unit 1010 provided in the image control unit 1007 specifies the surface, among the plurality of reflective surfaces of the polygon mirror 1002, that deflects (reflects) the laser beam.
In
The surface specifying unit 1010 specifies the surface by which the laser beam is deflected (the surface number) through the following method. Specifically, the surface specifying unit 1010 sets surface numbers A through D for four consecutive scanning periods of the BD signal, as illustrated in
The surface specifying unit 1010 then specifies which of the surface numbers A through D correspond to the surface numbers 1 through 4 on the basis of the calculated periods and the periods T1 through T4 held in the memory 1010a. In this manner, the surface specifying unit 1010 specifies the number of the surface by which the laser beam is deflected (the reflective surface, among the plurality of reflective surfaces of the polygon mirror 1002, that is used to scan the photosensitive drum 708) on the basis of the BD signal that is input.
Engine Control Unit
Control carried out by the engine control unit 1009 according to the present embodiment will be described next.
When a print job is started, in S101, the engine control unit 1009 starts driving the motor (the polygon motor) that rotationally drives the polygon mirror 1002. Once the rotation period of the polygon mirror 1002 matches the predetermined period in S102, the engine control unit 1009 starts outputting the image creation BD signal in S103. Then, in S104, the engine control unit 1009 is notified by the image control unit 1007, via a communication I/F 1012, that the surface specifying process is complete, and the processing then moves to S105.
Then, in S105, an instruction to form an image on the recording medium (an instruction to execute printing) is output from the image control unit 1007 to the engine control unit 1009 via the communication I/F 1012. After this, in S106, the engine control unit 1009 starts driving the registration rollers 723. The conveyance of the recording medium starts as a result.
Then, in S107, a signal indicating that the sheet sensor 726 has detected the leading end of the recording medium is input to the engine control unit 1009. After this, in S108, the engine control unit 1009 begins counting the pulses of the image creation BD signal that has been output using a counter 1009a. Note that the engine control unit 1009 counts the falls of the pulses of the image creation BD signal that is output, for example.
When in S109 the number of counted pulses reaches a number of pulses corresponding to one sheet's worth of the recording medium, in S110, the engine control unit 1009 stops counting the pulses of the image creation BD signal that is output, and in S111, the engine control unit 1009 resets the count number.
Furthermore, in S112, the engine control unit 1009 stops driving the registration rollers 723. Then, in S113, if the print job is not to be ended, the processing returns to S105. On the other hand, if in S113 the print job is to be ended, the engine control unit 1009 stops the output of the image creation BD signal in S114, and in S115, the engine control unit 1009 stops driving the polygon mirror 1002 and ends the processing of this flowchart. The foregoing has been a description of the control carried out by the engine control unit 1009.
Image Control Unit
Control carried out by the image control unit 1007 will be described next. As illustrated in
The surface specifying unit 1010 includes a timer 1010c that measures an amount of time spanning from when the pulse of the BD signal falls, to the first time the BD signal falls again after the stated fall of the BD signal. The surface specifying unit 1010 carries out the process of specifying the reflective surface through the above-described method on the basis of the measurement result from the timer 1010c and the periods T1 through T4 stored in the memory 1010a.
Additionally, the surface specifying unit 1010 includes a surface counter 1010b that stores information of the specified reflective surface. After specifying the reflective surface, the surface specifying unit 1010 updates the surface information in the surface counter each time the image creation BD signal is input (that is, each time the falling edge of the image creation BD signal is detected), and outputs that surface information.
Masking Processing Unit
The image creation BD signal input to the image control unit 1007 (or the falling edge of the image creation BD signal) is detected by a receiving unit 1013. The image creation BD signal may be erroneously detected if noise is intermixed with the image creation BD signal input to the image control unit 1007. Accordingly, in the present embodiment, the receiving unit 1013 is provided with a masking processing unit 1014 that carries out a masking process for the detection of the image creation BD signal, as illustrated in
In the present embodiment, during a period spanning until the surface specifying unit 1010 has successfully specified the surfaces, the masking processing unit 1014 sets the BD masking signal to “H” from when the falling edge of the image creation BD signal is detected by the receiving unit 1013 to when a predetermined amount of time Tm has passed. Note that the predetermined amount of time Tm is set on the basis of the shortest period among the scanning periods T1, T2, T3, and T4. Specifically, the predetermined amount of time Tm is an amount of time shorter than the shortest of the scanning periods T1, T2, T3, and T4 by a predetermined amount of time (margin), and is a pre-set amount of time. The predetermined amount of time Tm is stored in memory 1014a provided in the masking processing unit 1014.
Tm=T2−T6/2 (1)
The descriptions given below will use the following as examples of specific numerical values: T1=313.7345 (μs); T2=312.9556 (μs); T3=313.3329 (μs); and T4=313.1770 (μs). As further specific examples of numerical values, the polygon mirror 1002 is assumed to rotate once in 313.3 (μs), and 10.4 (ns) of rotational unevenness can arise. The rotational unevenness of 10.4 (ns) is rotational unevenness for a single rotation of the polygon mirror 1002, and T6 is therefore 10.4 (ns). As such, according to Expression (1), Tm=312.9504 (μs).
Once the predetermined amount of time Tm has passed after the BD masking signal 611 has been set to “H”, the masking processing unit 1014 switches the BD masking signal 611 from “H” to “L”. In the above-described masking process, the amount of time Tm for which the BD masking signal 611 is “H” is set on the basis of the shortest period among the scanning periods T1, T2, T3, and T4. In this case, the amount of time for which the BD masking signal 611 is “L” becomes longer in the order of the second surface, the fourth surface, the third surface, and the first surface, as illustrated in
As described above, the surface specifying unit 1010 outputs the surface information once the process for specifying the reflective surfaces is complete. As illustrated in
On the basis of the surface information, the masking processing unit 1014 carries out the masking processes corresponding to the respective reflective surfaces. Specifically, a BD masking period Tmk for the kth surface (where k is 1 to 4) is set according to the following Expression (2).
Tmk=Tk−T6/2 (2)
Applying the aforementioned specific numerical values results in the following:
Note that Tm1, Tm2, Tm3, and Tm4 are pre-set values and are stored in the memory 1014a provided in the masking processing unit 1014.
Image Data Correction
The image correction unit 1011 corrects the image data in order from image data A, which is the image data, among the plurality of pieces of data constituting one page's worth of an image as illustrated in
According to this configuration, the laser beam based on the image data corrected by the correction data corresponding to surface number “n” (where n is an integer from 1 to 4) is deflected by the reflective surface corresponding to the surface number “n”. The image correction unit 1011 carries out the above-described processing until the correction of the image data corresponding to one sheet of the recording medium is complete.
The image correction unit 1011 outputs the image data corrected on a region-by-region basis as described above to the laser control unit 1008 on a region-by-region basis, in order from the upstream side (i.e., from the image data A). Note that the image correction unit 1011 outputs a single piece of image data to the laser control unit 1008 each time the falling edge of the image creation BD signal is detected (i.e., in accordance with the period of the image creation BD signal). Although the image correction unit 1011 corrects the image data and outputs the corrected image data in synchronization with the image creation BD signal in the present embodiment, the configuration is not limited thereto. For example, the configuration may be such that the image correction unit 1011 corrects the image data in advance on the basis of the surface numbers from the surface counter 1010b, and outputs the pre-corrected image data to the laser control unit 1008 in synchronization with the image creation BD signal.
The image correction unit 1011 includes a counter (not shown) that counts the number of pieces of image data that have been output, and stops the output of the image data once the count of that counter reaches one sheet's worth (one page's worth) of the recording medium.
After the input of the image creation BD signal from the engine control unit 1009 to the image control unit 1007 is started in S201, the process moves to S202. In S202, the CPU 151 controls the masking processing unit 1014 to set the BD masking signal 611 to “H” for the predetermined amount of time Tm following the detection of the falling edge by the receiving unit 1013. As a result, the masking process is carried out for the detection of the image creation BD signal for a period equivalent to the amount of time Tm.
Next, in S203, the CPU 151 controls the surface specifying unit 1010 to carry out the surface specifying process on the basis of the image creation BD signal. The surface specifying process by the surface specifying unit 1010 is started as a result. Once the surface specification of S204 is complete, in S205, the CPU 151 controls the masking processing unit 1014 to carry out the masking process on a reflective surface-by-reflective surface basis. As a result, the masking process is carried out for the detection of the image creation BD signal for a period equivalent to the amount of time Tmk, i.e., in accordance with the reflective surface. Then, in S206, the CPU 151 notifies the engine control unit 1009 that the surface specification is complete, via the communication I/F 1012.
Then, in S207, the CPU 151 outputs an instruction to form an image on the recording medium to the engine control unit 1009. As a result, the engine control unit 1009 starts driving the registration rollers 723. In S208, the engine control unit 1009 notifies the image control unit 1007 that the sheet sensor 726 has detected the leading end of the recording medium, after which the CPU 151 moves the processing to S209. Upon the image creation BD signal being input in S209, in S210, the CPU 151 controls the image correction unit 1011 to correct the image data on the basis of the surface number indicated by the surface counter 1010b. As a result, the image correction unit 1011 corrects the image data on the basis of the surface number indicated by the surface counter 1010b.
Then, in S211, the CPU 151 controls the image correction unit 1011 to output the image data, which has been corrected in S210, to the laser control unit 1008 in synchronization with the image creation BD signal. As a result, the corrected image data is output to the laser control unit 1008 in synchronization with the image creation BD signal. The image control unit 1007 repeats the processing for S209 to S211 until image data corresponding to one sheet (one page) of the recording medium is output. The CPU 151 repeats the above-described processing until the print job is complete.
In this manner, before a reflective surface has been specified, the masking process is carried out on the basis of the amount of time Tm, which is set on the basis of the shortest of the scanning periods T1, T2, T3, and T4; after the reflective surface has been specified, the masking process is carried out on the basis of the amount of time Tmk, which is set on the basis of the scanning period of that reflective surface. According to this configuration, the period for detecting the BD signal can be shortened, and thus erroneous detections of the image creation BD signal caused by noise can be suppressed. In other words, a situation where the formed image is distorted can be suppressed.
Parts of the configuration of the image forming apparatus that are the same as those in the first embodiment will not be described. In the first embodiment, a BD masking period is set in accordance with the minimum BD period up until the reflective surface that reflects the laser beam is specified. In the present embodiment, a detection unit corresponding to each reflective surface of the polygon mirror 1002 is provided, and the detection units detect the BD signal in parallel.
As indicated in
According to the present embodiment, the time for detecting the BD signal after the reflective surface reflecting the laser beam has been specified can be shortened, which makes it possible to prevent erroneous operations caused by the intermixing of noise. Additionally, the reflective surface reflecting the laser beam can be specified by the detection units detecting the BD signal, which makes it possible to quickly specify the reflective surface.
Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiments and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiments, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiments and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiments. The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2018-018518, filed on Feb. 5, 2018, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-018518 | Feb 2018 | JP | national |
