JP2020016676A - Image forming apparatus and information processor - Google Patents

Abstract

To promptly specify a reflection surface of a polygon mirror of an image forming apparatus used in electrophotographic image formation.SOLUTION: An image forming apparatus 701 includes: a photoreceptor 708; a laser source 1000; a rotary polygon mirror 1002 that has a plurality of reflection surfaces and deviates laser light output from the laser source 1000 to scan the photoreceptor 708; a BD sensor 1004 for detecting laser light reflected on the reflection surfaces during the rotation of the rotary polygon mirror 1002; and a surface determination part 304 for determining the reflection surface on the basis of a cycle in which the laser light is detected by the BD sensor 1004. The surface determination part 304 determines the reflection surface for reflecting the laser light by comparison between a cycle of the laser light detected by the BD sensor 1004 during a period from the start of rotation of the polygon mirror 1002 to a time when the polygon mirror 1002 reaches a target rotational speed.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an information processing apparatus that corrects image data and transmits the image data to the image forming apparatus, and an image forming apparatus to which the information processing apparatus is connected.

  2. Description of the Related Art In an image forming apparatus using an optical scanning device, such as a laser printer or a digital copying machine, a laser beam output from a semiconductor laser scans the surface of a photoconductor (image carrier), so that the surface of the photoconductor becomes static. An electrostatic latent image is formed. Specifically, the laser beam output from the semiconductor laser is reflected on any surface of a rotating polygon mirror (polygon mirror) rotating at a constant speed, so that the surface of the photoconductor is scanned by the laser beam. A line is formed.

  However, since each surface of the rotary polygon mirror has certain non-negligible tolerances such as an angle error in the main scanning direction and a flatness error, the length of the scanning line due to each surface varies, and as a result, the output image Is distorted.

Patent Document 1 discloses an image forming apparatus that counts a signal interval between an FG signal, which is a rotation angle signal corresponding to a rotation angle of a polygon mirror, and a beam detector signal (BD signal). In this image forming apparatus, the reflection surface is specified by comparing the count value stored in advance for each reflection surface of the polygon mirror with the measured count value.
Patent Literature 2 discloses an image forming apparatus that stores in advance a count value of an interval at which an optical sensor detects light for each reflection surface of a polygon mirror in a memory. In this image forming apparatus, the reflection surface of the polygon mirror is identified by comparing the actually measured count value with the count value stored in the memory.

JP 2007-078723 A JP 2013-117699 A

However, the specification of the reflection surface in the image forming apparatuses described in Patent Documents 1 and 2 needs to be performed while the polygon mirror is rotating at a constant speed. Therefore, when a print job is started from a state in which the polygon mirror is stopped, such as at the time of first printing, the process of specifying the reflection surface is started until the polygon mirror reaches the target rotation speed and rotates stably. Can not do. As a result, it takes time to specify the reflection surface, and the first printout time increases. That is, productivity in image formation is reduced.
The present invention has been made in view of the above problems, and has as its object to suppress a decrease in productivity in image formation.

  The information processing apparatus of the present invention has a photoreceptor, a light source that outputs light based on image data, and a plurality of reflection surfaces, and is output from the light source using the plurality of reflection surfaces by rotating. A rotating polygon mirror that deflects the light to scan the photoconductor, a light receiving unit that receives the light deflected by the rotating polygon mirror, and outputs a predetermined signal in accordance with the reception of the light by the light receiving unit And a first output unit that outputs the image data to the image forming unit. The information processing device outputs the image data to the image forming unit after the rotation of the rotary polygon mirror starts. During the period until the rotation speed of the polygon mirror reaches the predetermined speed, the photoconductor of the plurality of reflection surfaces is selected based on a time interval between adjacent pulses of the predetermined signal output from the first output means. For scanning Specifying means for specifying a reflection surface to be used, and the image data corresponding to each of a plurality of scanning lines constituting an image for one recording medium by correction data corresponding to the reflection surface corresponding to each scanning line. Correcting means for outputting the corrected image data for one surface of the recording medium to the image forming means in accordance with the predetermined signal output from the first output means. And

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress that the productivity in image formation falls.

FIG. 1 is a configuration diagram of an image forming apparatus. FIG. 2 is a configuration diagram of a laser scanner unit. 7 is a timing chart of a TOP signal and the like. A graph showing the rotation speed of a polygon mirror. (A) is a graph showing the rotation speed of the polygon mirror, (b) is a graph showing the BD cycle profile on each reflecting surface. FIG. 3 is a functional block diagram of an image control unit. 4 is an example of a BD cycle profile stored in a profile storage unit. 9 is a flowchart illustrating a surface identification process. 5 is a timing chart illustrating a relationship between a BD signal and a BD cycle profile. 12 is an example of a BD cycle profile in the second embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the shapes and relative arrangements of the components described in the embodiment should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. The present invention is not limited to the following embodiments.
[First Embodiment]
<Image forming apparatus>
FIG. 1 is a configuration diagram of an image forming apparatus for describing a first embodiment. The image forming apparatus 701 is a copying machine that forms a monochrome image, but may be a copying machine that forms a color image. The image forming apparatus 701 includes an image reading device 700 such as a scanner. Image reading device 700 generates image data representing a document image read from document 702. The image forming apparatus 701 forms an image corresponding to the image data on a recording medium such as a sheet based on the image data acquired from the image reading apparatus 700.

  The image reading device 700 includes an illumination lamp 703 for irradiating the original 702 with light, a color sensor 706, and an optical system for guiding light reflected by the original 702 to the color sensor 706. The optical system has a group of mirrors 704a, 704b, 704c and a lens 705. The optical system forms an image of the light emitted from the illumination lamp 703 and reflected by the document 702 on the color sensor 706. The color sensor 706 reads the original image of the original 702 from the received reflected light for each of the blue (B), green (G), and red (R) color separation lights and converts the read image into an electrical image signal. The image reading device 700 performs a color conversion process on an image signal to generate image data representing a document image. The image reading device 700 transmits the generated image data to the image forming device 701.

  The image forming apparatus 701 has a cassette paper feed unit 718 in which transfer paper as a recording medium is stored, and the transfer paper is fed from the cassette paper feed unit 718. At this time, the transfer paper is fed out by the pickup roller 719 in order from the top one. From the transfer paper fed out by the pickup roller 719, only the uppermost transfer paper is separated by a separation roller pair 722 composed of a feed roller as a conveyance unit and a retard roller as a separation unit. The separated transfer paper is conveyed to the stopped registration roller pair 723 through the plurality of conveyance roller pairs 721 and 720.

The transfer paper sent to the registration roller pair 723 is stopped once when the leading end of the transfer paper abuts the nip of the registration roller pair 723 to form a predetermined loop. The formation of this loop corrects the skew state of the transfer paper.
Next, an image forming method of the image forming apparatus 701 will be described. Image data obtained by the image reading device 700 is corrected by the image control unit 1007, and is input to a laser scanner unit 707 including a laser and a polygon mirror. The photoconductor 708 is rotated clockwise by a motor (not shown), and is uniformly charged by the primary charger 709. Thereafter, exposure of the charged photoconductor 708 with laser light based on the image data input to the laser scanner unit 707 is started, and an electrostatic latent image is formed on the photoconductor 708. This electrostatic latent image is developed by the toner supplied from the developing device 710.

  The transfer paper is sent by a pair of registration rollers 723 to a transfer portion that is a contact portion between the transfer roller 711 and the photoconductor 708, and a toner image is formed on the transfer paper. The transfer paper that has passed through the transfer unit is sent to a fixing device 724 serving as an image fixing unit, and the transfer paper is heated and pressed by rollers in the fixing device 724 to fix the transfer toner image on the transfer paper surface. The transfer paper having undergone the fixing process that has passed through the fixing device 724 is discharged onto a discharge tray 725 outside the apparatus.

  FIG. 2 shows a configuration diagram of the laser scanner unit 707. In the figure, a laser light source 1000 emits laser light from both ends of a laser element under the control of a laser control unit 1008. The operation of the laser scanner unit 707 is controlled by the engine control unit 1009 and the image control unit 1007. In the present embodiment, the substrate on which the engine control unit 1009 is provided is different from the substrate on which the image control unit 1007 is provided. The board on which the engine control unit 1009 is provided is connected to the board on which the image control unit 1007 is provided by a cable. However, the present invention is not limited to this, and an arbitrary configuration such as providing the engine control unit 1009 and the image control unit 1007 on the same substrate can be adopted. Further, the image control unit 1007 has a profile storage unit 302 in which a BD cycle profile described later is stored.

  Laser light emitted from the rear end of the laser light source 1000 is incident on a photodiode (PhotoDiode: PD) 1003, is converted into an electric signal, and is input to the laser control unit 1008 as a PD signal. The laser control unit 1008 controls the output light amount of the laser light source 1000 (Auto Power Control: APC) based on the signal. There is no particular limitation on the control method of APC, and a known general APC control can be used. Laser light emitted from the front end of the laser light source 1000 becomes laser light converged via a collimator lens 1001 and is applied to a polygon mirror (rotating polygon mirror) 1002. The engine control unit 1009 controls the rotation of a polygon motor integrated with the polygon mirror 1002 by a drive signal (Acc / Dec), and the polygon mirror 1002 is driven to rotate counterclockwise.

The laser light applied to the polygon mirror 1002 is reflected and deflected on its reflection surface during rotation of the polygon mirror 1002, and is scanned by rotation. The laser beam that has been rotationally scanned enters a beam detector (Beam Detect: BD) sensor 1004 including a light receiving element as a light receiving unit that receives the laser light.
The BD sensor 1004 generates a BD signal based on the detected laser beam and outputs the signal to the engine control unit 1009. The engine control unit 1009 controls the polygon motor based on the input BD signal so that the rotation cycle of the polygon mirror 1002 becomes a predetermined cycle. When the cycle of the BD signal has a cycle corresponding to the predetermined cycle, engine control section 1009 determines that the rotation cycle of polygon mirror 1002 has reached the predetermined cycle. Note that the BD signal and the imaging BD signal are negative logic signals, and the assertion of the BD signal and the imaging BD signal hereinafter means the fall of each signal.
The engine control unit 1009 outputs an imaging BD signal to the image control unit 1007 according to the input BD signal. The BD signal for image formation is synchronized with the BD signal, and corresponds to a signal indicating one scanning cycle in which the laser beam scans the photosensitive drum 708.
The image control unit 1007 outputs the corrected image data to the laser control unit 1008 according to the input BD signal for image formation. The specific control configurations of the engine control unit 1009 and the image control unit 1007 will be described later.

  When the polygon mirror 1002 rotates stably, the transfer of the transfer paper that has been temporarily stopped by the registration roller pair 723 is restarted. A registration sensor 726 is arranged near the registration roller pair 723 to detect the leading edge of the transfer paper. An image drawing start timing signal (TOP signal) is input from the registration sensor 726 to the engine control unit 1009 and the image control unit 1007, and image formation is started according to the timing signal.

  FIG. 3 is a timing chart for explaining the operations of the TOP signal, the BD signal, the BD signal for image formation, and the image data. After the rotation of the polygon mirror 1002 is stabilized and the transfer paper is conveyed by the registration roller pair 723 and passes through the registration sensor 726, a TOP signal is asserted to the image control unit 1007. When the TOP signal is asserted, the image control unit 1007 starts outputting image data to the image forming apparatus 701 in synchronization with the BD signal for image formation. Note that a period shown as “Page 1” in the drawing corresponds to image data for one recording medium.

  The laser control unit 1008 generates laser light for forming an electrostatic latent image on the photoconductor 708 by blinking and driving the laser light source 1000 based on the image data acquired by the image forming apparatus 701.

  The laser beam that has been turned on and off is corrected by passing through the F-θ lens 1005 so that the polygon mirror 1002 starts scanning at a constant angular velocity and scans the photoconductor 708 at a constant speed. The corrected laser beam forms a latent image on the photoconductor 708 via the folding mirror 1006. This electrostatic latent image is developed by the toner supplied from the developing device 710.

  As described above, the transfer paper is sent by the registration roller pair 723 to the transfer portion that is in contact with the transfer roller 711, and the toner image is transferred onto the transfer paper. The transfer paper that has passed through the transfer unit is heated and pressed in a fixing device 724 to fix the transfer toner image on the sheet surface. The transfer paper having undergone the fixing process that has passed through the fixing device 724 is discharged onto a discharge tray 725 outside the apparatus. By the above operation, a copy image can be formed on the transfer paper.

<< Surface identification processing sequence >>
Next, the control of the surface identification processing which is a feature of the present invention will be described.
<Surface identification processing timing>
FIG. 4 is a graph showing the rotation speed of a polygon mirror of a conventional image forming apparatus. In the figure, T1 indicates the surface identification processing timing in the present embodiment, T2 indicates the timing at which the rotation speed of the polygon mirror is stabilized, and T3 indicates the surface identification processing timing in the prior art. In the figure, the vertical axis represents the rotation speed [times / us] of the polygon mirror, and the horizontal axis represents time [us]. In the figure, in an initial state, the rotation of the polygon mirror 1002 is stopped, and the polygon mirror 1002 starts to rotate as time passes, and stably rotates at a target rotation speed. FIG. 4 shows an example of a graph of the transition of the speed from the start of rotation of the polygon mirror 1002 to the stabilization of the rotation speed.

  In order for the rotation speed of the polygon mirror to reach a predetermined speed or a target rotation speed and stabilize the rotation speed, a time period of about several hundred milliseconds from the start of rotation to timing T2 is required as shown by T4 in the figure. It is. In the conventional image forming apparatus, the timing at which the surface identification processing is completed is a timing T3 which is further later than the timing T2 at which the rotation speed of the polygon mirror 1002 is stabilized.

  On the other hand, the image forming apparatus 701 according to the present embodiment performs the surface specifying process at the timing T1 during the rotation speed acceleration period of the polygon mirror 1002 (timing T1). By executing the surface specifying process during the rotation speed acceleration period of the polygon mirror 1002, the surface specifying process can be completed at a timing earlier than the conventional surface specifying process.

<BD cycle profile>
The image control unit 1007 is provided with a profile storage unit 302 in which a BD cycle profile for performing a surface identification process during the acceleration period of the polygon mirror 1002 is stored. The BD cycle profile is profile information of a BD signal cycle corresponding to each reflection surface during the acceleration period of the polygon mirror 1002.

  FIG. 5A is a graph showing a change in rotation speed from the start of rotation of the polygon mirror 1002 to the acceleration of the polygon mirror 1002 to stable rotation at the target rotation speed, similarly to FIG. FIG. 5B shows a BD cycle profile of each reflection surface (surfaces 1 to 4) of the polygon mirror 1002 during the same period of transition of the rotation speed of the polygon mirror 1002 shown in FIG. It is a graph. The BD cycle profile indicates a transition of the cycle of the BD signal for each reflection surface during a period from when the polygon mirror 1002 is stopped to when it is rotated stably. Note that the BD cycle in the present embodiment corresponds to a time interval between adjacent pulses of a BD signal generated by the BD sensor 1004, that is, one scanning cycle of laser light.

  The BD cycle profile is created based on, for example, the cycle of the BD signal measured in advance. Specifically, for example, the BD cycle profile is generated by applying a method such as the least square method to the data of the actually measured values. The BD cycle profile obtained for each reflecting surface is stored in advance in a profile storage unit 302 in an image control unit 1007 described below.

<Image control unit 1007>
Next, an image control unit 1007 that performs control related to the surface identification processing in the present embodiment will be described. FIG. 6 shows an example of a functional block diagram of the image control unit 1007. The image control unit 1007 includes the CPU 100, the DRAM 200, the ROM 210, the surface identification unit 300, the image correction unit 400, the communication I / F 500, and the internal bus 600.

  The CPU 100 performs surface identification control in the surface identification unit 300 and image correction control for each surface in the image correction unit 400. Further, the CPU 100 reads out and expands the OS and application programs stored in the ROM 210 into the DRAM 200 which is a volatile memory, and executes the readout OS and application programs. Image data, an OS, an application program, and the like handled by the image correction unit 400 are stored in the ROM 210 or the DRAM 200. The processing executed by the image control unit 1007 described below is executed by the CPU 100 unless otherwise specified.

  The surface identification unit 300 determines which reflection surface of the polygon mirror 1002 is used for laser light scanning on the photoconductor 708 based on the time interval between successive pulses of the image forming BD signal input to the image control unit 1007. This is a module for specifying whether or not Hereinafter, the time interval between successive pulses of the imaging BD signal input to the image control unit 1007 is simply referred to as a BD cycle. The surface specifying unit 300 executes the surface specifying process according to the value set in the control register 301 from the CPU 100, and notifies the image correcting unit 400 of the ID for identifying the reflection surface by the surface identification signal after the specification is completed.

  The image correction unit 400 corrects an image according to the characteristics of the reflection surface of the polygon mirror 1002. More specifically, the image correction unit 400 corrects the magnification and the writing start position of the image in accordance with the characteristics of each surface using correction data measured in advance according to the reflection surface specified by the surface identification signal. Do. In particular, in the first embodiment, the image data corresponding to each of a plurality of scan lines forming an image for one recording medium is corrected by correction data corresponding to a reflection surface corresponding to each scan line. After that, the image correction unit 400 outputs the image after the correction based on the correction data. The communication I / F 500 is an interface for performing communication between the image control unit 1007 and the engine control unit 1009.

  The internal bus 600 is an internal bus that connects the CPU 100, the DRAM 200, the surface identification unit 300, the image correction unit 400, and the communication I / F 500, which are internal processing units of the image control unit 1007. To send data to each other. Requests and notification commands related to the rotation control of the polygon mirror 1002 and the printing process are sent to the CPU 100, the surface identification unit 300, and the image correction unit 400 via the communication I / F 500 and the internal bus 600.

  The BD signal for image formation is input to the surface specifying unit 300 and the image correcting unit 400, and the surface specifying unit 300 inputs the surface identification signal to the image correcting unit 400. The image correction unit 400 receives the image forming BD signal and the surface identification signal, and outputs image data to the image forming apparatus 701 under the control of the CPU 100.

<Surface identification unit 300>
Next, the surface specifying unit 300 will be described. The surface identification unit 300 includes a control register 301, a profile storage unit 302, a timer 303, and a surface determination unit 304 as determination means. The control register 301 is a register group including a flip-flop circuit and the like, and stores values indicating settings and states for each control in the surface specifying unit 300 by the CPU 100.

The profile storage unit 302 is configured by a nonvolatile memory such as a flash ROM, and stores the previously measured BD cycle profile of each reflective surface. The BD cycle profile includes information in which the elapsed time from the start of the rotation driving of the polygon mirror 1002 and the time interval corresponding to the reflection surface of the polygon mirror 1002 are associated with each other. The profile storage unit 302 may store data obtained by measurement of the image forming apparatus 701 at the time of shipment from the factory, or may store data measured when the image forming apparatus 701 is first started. Furthermore, data obtained by periodically measuring the BD period of each reflecting surface may be stored.
FIG. 7 shows an example of the BD cycle profile stored in the profile storage unit 302. In the drawing, the BD cycle profile is shown in the form of a table having rows and columns, and each of columns 751 to 756 has an address, a time, a plane 1BD cycle, a plane 2BD cycle, and a plane 3BD cycle. And the surface 4BD period. In addition, in order to simplify the description, the reflection surface 1 is described as a surface 1 in the drawing. The same applies to the reflection surfaces 2 to 4.

  In the present embodiment, since the polygon mirror 1002 has four reflecting surfaces, the BD period is shown for each of the reflecting surfaces 1 to 4 of the polygon mirror 1002 in FIG. As illustrated, the BD cycle of each reflective surface is created in advance at predetermined time unit intervals (100 [us]), and the BD cycle profile includes the value of the BD cycle corresponding to each reflective surface. .

  In detail, the time shown in the column 752 of FIG. 7 indicates the elapsed time from the time when the BD cycle profile is measured (the time when the rotation of the polygon mirror 1002 is started in the present embodiment). In the illustrated example, the elapsed time corresponding to the BD cycle profile created in units of 100 [us] is shown.

  The surface 1 BD cycle shown in the column 753 is a value of the BD cycle corresponding to the first reflection surface of the polygon mirror 1002, and is a value of the BD cycle corresponding to the elapsed time indicated by time. Similarly, the surface 2BD period, the surface 3BD period, and the surface 4BD period are values of the BD periods corresponding to the second, third, and fourth reflecting surfaces of the polygon mirror 1002, respectively, and the BD corresponding to each elapsed time. This is the value of the period. For each of the addresses 1, 2,..., 10000, the corresponding time and the values of the surface 1BD period to the surface 4BD period are created and stored in advance.

  Address 1 stores a surface 1 BD cycle to a surface 4 BD signal at 100 [us] after the polygon mirror starts rotating. Since the elapsed time from the start of rotation of the polygon mirror is short, the rotation speed of the polygon mirror is low, and the BD cycle is long. For example, the surface 1 BD cycle is 3500.

  On the other hand, the address 10000 stores the surface 1 BD cycle to the surface 4 BD signal at the time of 1,000,000 [us] after the polygon mirror starts rotating. Since the elapsed time from the start of rotation of the polygon mirror 1002 is long, the rotation speed is high, and the BD cycle is short. For example, the surface 1 BD cycle is 500. As shown, the number of addresses is 10000, and the time and the value of the BD cycle of each surface are stored for each of these addresses. In the first embodiment, the BD period of each reflecting surface is stored at an interval of 100 [us], and 10,000 addresses are created over the entire period until the rotation speed is stabilized. However, the present invention is not limited to this, and it is possible to arbitrarily determine an interval for creating addresses, the number of addresses to be created, and a period from when the polygon mirror 1002 starts rotating until the rotation speed becomes stable. it can.

  The timer 303 is a timer circuit for measuring a time interval (period) between adjacent pulses of the BD signal for image input input to the image control unit 1007 and an elapsed time after the rotation of the polygon mirror 1002 is started. . The timer 303 may be configured by a counter circuit that counts in units of time to be measured, or may be configured by a real-time clock circuit or the like generally used for measuring time in a power-off state of the device. The timer 303 includes two timer circuits: a timer circuit that measures the period of a BD signal (not shown) and a timer circuit that measures the elapsed time from the start of rotation of the polygon mirror 1002.

  The count value of the timer circuit that measures the period of the BD signal increases as time passes, and the count value of the counter circuit is reset each time a falling edge of the BD signal is detected. The count value at the time of reset indicates the time from when the counter circuit is reset to when the next fall of the BD signal is detected. The CPU 100 transmits a value obtained by converting the count value at the time of reset to a BD cycle to the surface determination unit 304 as a measured value of the BD signal.

  The timer circuit that measures the elapsed time from the start of the rotation of the polygon mirror 1002 continues the count process without resetting the count value until the surface identification process is completed. Similarly, each time the BD signal is asserted, the timer circuit transmits a value obtained by converting the count value of the counter circuit into time to the surface determination unit 304 as a value of an elapsed time from the start of rotation of the polygon mirror 1002.

  The surface determination unit 304 determines the reflection surface of the polygon mirror 1002 based on the BD cycle measured by the timer 303, the elapsed time from the start of rotation of the polygon mirror 1002, and the BD cycle profile stored in the profile storage unit 302. Details of the processing executed by the surface determination unit 304 will be described later. Information on the reflection surface of the polygon mirror 1002 determined by the surface determination unit 304 is output to the image correction unit 400 as a surface identification signal.

<Surface identification processing sequence>
FIG. 8 is a flowchart illustrating the surface identification processing according to the first embodiment. The CPU 100 transmits a request to start rotation of the polygon mirror 1002 to the engine control unit 1009, and starts rotation of the polygon mirror 1002 (S801).

  Thereafter, the CPU 100 activates a timer circuit for measuring the period of the BD signal in the timer 303 and a timer circuit for measuring the elapsed time from the start of the rotation of the polygon mirror 1002 (S802). The activation of each timer circuit can be performed by an arbitrary method. In the present embodiment, the activation is performed by the CPU 100 setting the corresponding register of the control register 301. Note that there is a predetermined time lag between when the CPU 100 transmits a request to start rotation of the polygon mirror 1002 to the engine control unit 1009 and when the rotation of the polygon mirror 1002 actually starts. Accordingly, each timer circuit in the timer 303 is started after a time corresponding to the predetermined time lag has elapsed.

  When the rotation of the polygon mirror 1002 is started, the engine control unit 1009 emits laser light from the laser light source 1000 and irradiates the polygon mirror 1002 (S803). The surface specifying unit 300 of the image control unit 1007 determines whether the BD signal for imaging output from the engine control unit 1009 has been asserted (S804).

  When the falling edge of the BD signal for image formation is not detected (S804: N), the plane identifying unit 300 executes S804 again. When the fall of the imaging BD signal is detected, the surface identification unit 300 determines that the imaging BD signal has been asserted (S804: Y). In this case, the surface identification unit 300 acquires the value of the BD cycle from the count value of the timer circuit that measures the cycle of the imaging BD signal in the timer 303 (S805).

  The surface identification unit 300 acquires the value of the elapsed time from the start of the rotation of the polygon mirror 1002 from the count value of the timer circuit that measures the elapsed time from the start of the rotation of the polygon mirror 1002 in the timer 303 (S806). The surface specifying unit 300 refers to the BD cycle profile of each reflection surface stored in the profile storage unit 302 in advance, and acquires the value of the BD cycle profile stored at the address corresponding to the acquired elapsed time (S807).

  The surface specifying unit 300 compares the obtained value of the BD period with the value of the BD period profile of each reflection surface (S808). As a result of the comparison by the surface determination unit 304, the surface determination unit 304 sets the reflection surface corresponding to the BD cycle profile having the closest value to the acquired BD period value to the reflection surface corresponding to the asserted BD signal. Is determined (S809). Thereafter, the image control unit 1007 determines whether or not the determination has been completed for all the reflecting surfaces (S810), and if not completed (S810: N), executes S804 again. In this way, the processing of S804 to S809 is repeated until the determination for all the reflecting surfaces is completed. If the determination has been completed for all reflection surfaces (S810: Y), the image control unit 1007 ends the surface identification processing sequence.

  Hereinafter, the processing in S809 will be described in more detail with reference to FIG. FIG. 9 is an example of a timing chart showing the relationship between the BD signal with respect to time and the BD cycle profile for each reflection surface stored in the profile storage unit 302. This timing chart is obtained by enlarging the period corresponding to the period A, which is the acceleration period of the polygon mirror 1002, in the BD cycle profile shown in FIG. 5B. In the figure, T0 to T6 indicate the timing (time from the start of rotation of the polygon mirror 1002) at which the BD signal for image formation is asserted, respectively.

  In this example, the surface identification processing is performed in a period A, which is an acceleration period of the polygon mirror 1002. The timing at which the BD signal for image formation is asserted is T0 = 26900 [us], T1 = 30000 [us], T2 = 31800 [us], T3 = 36500 [us], and T4 = 42200 [us]. . The value of the elapsed time from the start of rotation of the polygon mirror 1002 acquired in S806 is the same as the value of T0 to T4, and is 26900 [us], 30000 [us], 31800 [us], 36500 [us], 42200 [us].

  In this example, at the timings of T1 to T4, the values of the period of the BD signal actually acquired in S805 are 3100 [us], 1800 [us], 4700 [us], and 5800u, respectively. On the other hand, the value of the BD cycle profile stored in the profile storage unit 302 is the same as the value shown in FIG. When the BD signal for imaging is asserted at the timing of T1, the surface determination unit 304 determines from the profile storage unit 302 the BD cycle of each reflective surface stored in the address 300 corresponding to the time 30000 [us] at T1. get. As a result, the surface determination unit 304 acquires values of 3000 [us], 1800 [us], 4800 [us], and 6000 [us] as values of the surface 1 BD period to the surface 4 BD period.

  The cycle of the BD signal asserted at the timing of T1 is 3100 [us]. The surface determination unit 304 refers to the values of the surface 1 BD period to the surface 4 BD period stored in the address 300 and determines the reflection surface having the BD period closest to 3100 [us]. Since the value of the surface 1BD period is 3000 [us], the surface determination unit 304 determines that the BD signal asserted at T1 is a signal generated on the first reflection surface of the polygon mirror 1002.

  In the first embodiment, the surface determination unit 304 obtains the absolute value of the difference between the detected period of the BD signal and the value of the surface 1BD period to the surface 4BD period. It is determined that the BD cycle having the smallest absolute value is the BD cycle having the closest value to the value of the acquired BD cycle. However, the criterion for determining the closest value is not limited to the simple difference between the values as described above, and another criterion may be used. For example, the difference between the logarithm of each value of the surface 1BD period to the surface 4BD period and the logarithm of the acquired BD value may be obtained, and the reflective surface having the smallest difference may be determined.

  Similarly, when the imaging BD signal is asserted at the timing of T2 (31800 [us]), the surface determination unit 304 determines the BD of each reflection surface stored in the profile storage unit 302 at the address 318 corresponding to T2. Get the period value. As a result, the surface determination unit 304 acquires values of 2950 [us], 1770 [us], 4720 [us], and 5900 [us] as values of the surface 1 BD period to the surface 4 BD period.

  The cycle of the BD signal asserted at the timing of T2 is 1800 [us]. The surface determination unit 304 refers to the values of the surface 1 BD period to the surface 4 BD period stored in the address 318 and determines the reflection surface having the BD period closest to 1800 [us]. Since the value of the surface 2BD cycle is 1770 [us], the surface determination unit 304 determines that the BD signal asserted at T2 is a signal generated on the second reflection surface of the polygon mirror 1002.

  When the BD signal for image formation is asserted at the timing of T3, the surface determination unit 304 acquires the value of the BD cycle of each reflection surface stored in the address 365 corresponding to T3 from the profile storage unit 302. As a result, the surface determination unit 304 acquires values of 2900 [us], 1740 [us], 4640 [us], and 5800 [us] as values of the surface 1 BD period to the surface 4 BD period.

  The cycle of the BD signal asserted at the timing of T3 is 4700 [us]. The surface determination unit 304 refers to the values of the surface 1 BD period to the surface 4 BD period stored at the address 365 and determines the reflection surface having the BD period closest to 4700 [us]. Since the value of the surface 3BD cycle is 4640 [us], the surface determination unit 304 determines that the BD signal asserted at T3 is a signal generated on the third reflection surface of the polygon mirror 1002.

  When the BD signal for image formation is asserted at the timing of T4, the surface determination unit 304 acquires the value of the BD cycle of each reflective surface stored in the address 422 corresponding to T4 from the profile storage unit 302. As a result, the surface determination unit 304 acquires the values of 2850 [us], 1710 [us], 4560 [us], and 5700 [us] as the values of the surface 1 BD period to the surface 4 BD period.

  The cycle of the BD signal asserted at the timing of T4 is 5800 [us]. The surface determining unit 304 refers to the values of the surface 1 BD period to the surface 4 BD period stored in the address 422 and determines the reflective surface having the BD period closest to 5800 [us]. Since the value of the surface 4BD period is 5700 [us], the surface determination unit 304 determines that the BD signal asserted at T4 is a signal generated by the fourth reflection surface of the polygon mirror 1002.

  In this way, the surface determination unit 304 can determine which of the reflection surfaces of the polygon mirror 1002 the asserted BD signal is a signal generated from. In the first embodiment, the determination of the reflection surface by the surface determination unit 304 is performed four times T1 to T4. However, the number of reflection surface determinations is not limited to four, and it is sufficient to execute the minimum number of times necessary to accurately determine the reflection surface.

  In particular, in the first embodiment, the values of the BD periods of the reflecting surfaces 1 to 4 are different from each other, and the difference between the periods is at least 200 [us] or more. For example, even at the address 10000 where the BD cycle becomes the shortest, the BD cycle is 500, 300, 800, and 1000 [us], and each cycle has a difference of 200 [us] or more. Therefore, determination failure due to a measurement error, an error, or the like is unlikely to occur. In the first embodiment, the determination of the reflective surface (S809) is performed for all the reflective surfaces (S810), but the number of determinations is not limited to four. Depending on the difference between the periods in the reflection surfaces 1 to 4, the number of determinations may be only one. On the other hand, if, for example, the periods of the reflecting surface 1 and the reflecting surface 2 are the same or close to each other, the reflecting surface cannot be determined by one determination. In this case, it is necessary to determine two or more reflecting surfaces. Therefore, it is preferable that the number of times of measurement of the reflecting surface in S810 be changed according to the cycle of the reflecting surfaces 1 to 4.

As described above, the image forming apparatus 701 of the first embodiment executes the surface identification processing during the acceleration period of the polygon mirror 1002 by creating the BD cycle profile during the acceleration period of the polygon mirror 1002 in advance. Therefore, by executing the surface identification processing during the acceleration period, the preparation processing required for image formation including the image correction in accordance with the characteristics of each reflection surface in the image correction unit 400 is started at an early timing. Can be. Since the preparation processing can be completed at an earlier timing, the first printout time can be reduced.
In particular, in the first embodiment, since the surface identification processing is completed during this acceleration period, the first printout time can be further reduced.

[Second embodiment]
In the first embodiment described above, the BD cycle profile stored in the profile storage unit 302 is created for the entire period from the start of rotation of the polygon mirror 1002 to steady rotation at the target rotation speed. Accordingly, over the entire period during which the polygon mirror 1002 is accelerating, the time from the start of rotation (column 752) and the value of the BD cycle (columns 753 to 756) of each surface are stored in the profile storage unit 302 for each address (column 751). Is stored. However, in this case, the address area of the profile storage unit 302 required for storing these values increases, and as a result, the required memory capacity increases.
For this reason, in the second embodiment, a period for performing the surface identification processing is set in advance, and only the BD cycle profile corresponding to the set period is stored in the profile storage unit 302. The details are described below.

<Address control sequence>
FIG. 10 shows an example of a BD cycle profile stored in the profile storage unit 302 in the second embodiment. In the drawing, each of columns 751 to 756 represents an address, a time, a surface 1BD period, a surface 2BD period, a surface 3BD period, and a surface 4BD period, as in FIG.
In the second embodiment, a period from 30,000 [us] to 49900 [us] is set as a period for performing the surface identification processing. Therefore, in the BD cycle profile shown in FIG. 7, the time at address 0 is 100, whereas the time at address 0 in FIG. 10 is 30,000. Further, the time at address 0 in FIG. 10 and the values of the surface 1 BD cycle to the surface 4 BD cycle match the values at address 300 in FIG.

  As shown, the BD cycle profile of the second embodiment has addresses 0 to 199, and each address is generated at intervals of 100 [us]. Further, since the time of the address 0 in the surface identification processing period is 30000 [us] and the end time is 49900 [us], 200 addresses (address 0 to address 199) are stored in the BD cycle profile. .

  Therefore, in the second embodiment, as shown in FIG. 10, the size of the address area required for the profile storage unit 302 is 200. In the first embodiment shown in FIG. 7, since the address area required for the profile storage unit 302 is 10,000, the address area required for the profile storage unit 302 is greatly reduced in the second embodiment. Is shown. The addresses 0, 18, 65 and 122 of the BD cycle profile in FIG. 10 have the same values as the addresses 300, 318, 365 and 422 corresponding to the respective timings of T1, T2, T3 and T4 shown in FIG. Is stored. As described above, in the second embodiment, while the address area required for the profile storage unit 302 is reduced, the reflection surface of the polygon mirror 1002 by the surface determination unit 304 at the timings T1 to T4 as in the first embodiment. Can be determined. As a result, the surface identification processing in the second embodiment is executed in the same manner as the surface identification processing described in the first embodiment.

  The image forming apparatus 701 according to the second embodiment generates a BD cycle profile for a predetermined part of the period during which the polygon mirror 1002 is rotating. By using the BD cycle profile generated for a part of the period as described above, the capacity required for the profile storage unit 302 can be reduced. Further, similarly to the image forming apparatus 701 of the first embodiment, the first printout time can be reduced.

  As described above through the first embodiment and the second embodiment, according to the present invention, the reflection surface of the polygon mirror 1002 is specified during the period in which the polygon mirror 1002 is accelerated from the stopped state to the target speed. To start. In particular, in the first and second embodiments, control is performed to complete the target speed. Therefore, in comparison with the prior art in which the specification of the reflecting surface cannot be started until the polygon mirror 1002 reaches the target rotation speed, the present invention starts the specifying of the reflecting surface earlier and specifies the reflecting surface earlier. Can be completed. In particular, in the first embodiment and the second embodiment, the specification of the reflection surface can be completed before the polygon mirror 1002 reaches the target rotation speed. Therefore, the time required for specifying the reflection surface is reduced, and the first printout time can be shortened.

In the first embodiment and the second embodiment, the surface determination process is performed in a period indicated by period A in FIG. The reason is that, during the period A, the difference between the BD cycle of each reflecting surface and the BD cycle of the other reflecting surfaces is large, and it is easy to determine. For example, after the rotation indicated by T2 in the drawing is stabilized, the difference between the surface 1BD period and the surface 2BD period of the polygon mirror 1002 is the smallest. On the other hand, in the period A, the difference between the surface 4BD period and the surface 3BD period is the smallest. Then, since the difference between the surface 4BD period and the surface 3BD period in the period A is larger than the difference between the surface 1BD period and the surface 2BD period in T2, the surface determination can be performed more accurately in the period A. .
Therefore, the surface determination process is preferably performed during a period in which the difference between the BD periods of the respective surfaces is larger as described above.

  Further, in the first and second embodiments, the surface specifying unit 300 is provided in the image control unit 1007 of the image forming apparatus 701. However, the surface specifying unit 300 may be an information processing device separate from the image forming apparatus 701. . In this case, the surface determination unit 304 receives the work BD signal from the image forming apparatus 701, and transmits the determination result of the reflective surface to the image correction unit 400 of the image forming apparatus 701. This makes it possible to add the surface determination unit 304 to the existing image forming apparatus or replace the surface identification unit 300 to correct or update the surface determination processing of the surface determination unit 304 and the BD cycle profile. .

Claims (10)

A photoreceptor,
A light source that outputs light based on image data,
A rotating polygon mirror that has a plurality of reflecting surfaces and deflects the light output from the light source using the plurality of reflecting surfaces by rotating to scan the photoconductor,
A light receiving unit that receives the light deflected by the rotating polygon mirror,
First output means for outputting a predetermined signal in accordance with the reception of the light by the light receiving unit,
In an information processing apparatus connected to an image forming apparatus having an image forming unit including, and outputting the image data to the image forming unit,
During the period from the start of rotation of the rotary polygon mirror to the rotation speed of the rotary polygon mirror reaching a predetermined speed, a time interval between adjacent pulses of the predetermined signal output from the first output unit is determined. Specifying means for specifying a reflection surface used for scanning the photosensitive member among the plurality of reflection surfaces,
The image data corresponding to each of a plurality of scanning lines constituting an image for one recording medium is corrected by correction data corresponding to the reflection surface corresponding to each scanning line, and the corrected one surface of the recording medium is corrected. Correction means for outputting the image data of the minute to the image forming means in accordance with the predetermined signal output from the first output means;
An information processing apparatus comprising: The information processing apparatus includes a storage unit configured to store information in which an elapsed time since rotation driving of the rotary polygon mirror is started in the period and the time interval corresponding to the reflection surface are associated with each other. ,
2. The method according to claim 1, wherein the specifying unit specifies the reflection surface based on an elapsed time from when rotation driving of the rotary polygon mirror is started and the information stored in the storage unit. An information processing apparatus according to claim 1. The information stored in the storage means includes a value of the time interval determined for each of the reflecting surfaces according to an elapsed time since the rotation driving of the rotary polygon mirror was started, Do
The information processing device according to claim 2. The information stored in the storage means includes, during a period from when the rotation driving of the rotary polygon mirror is started to when the predetermined speed is reached, the time determined for each of the reflection surfaces according to the elapsed time. Characterized in that the value of the interval is included,
The information processing device according to claim 3. The information stored in the storage means includes, for a part of a period from when the rotation driving of the rotary polygon mirror is started to when the predetermined speed is reached, for each of the reflection surfaces according to the elapsed time. Wherein the value of the time interval defined in is included,
The information processing device according to claim 3. The value of the time interval defined for each of the reflecting surfaces according to the elapsed time since the rotation driving of the rotary polygon mirror included in the information stored in the storage unit is the rotary polygon mirror. Characterized in that it is a value obtained from an actual measurement value measured during rotation of
The information processing device according to claim 3. The image data is corrected by the correction data corresponding to the specified reflection surface, and further includes a control unit configured to output the light to the light source according to the corrected image data,
The information processing apparatus according to claim 1. The specifying means specifies the reflection surface reflecting the light received by the light receiving unit by the number of reflection surfaces of the rotary polygon mirror until the rotating polygon mirror reaches the predetermined speed. Characterized by
The information processing device according to claim 1. The specifying means, by the time the rotating polygon mirror reaches the predetermined speed, completes the specification of the reflection surface that reflects the light received by the light receiving unit,
An information processing apparatus according to claim 1. An image forming apparatus comprising: a generating unit configured to generate image data; and an image forming unit configured to form an image on a recording medium based on the image data generated by the generating unit.
The image forming unit includes:
A photoreceptor,
A light source that outputs light based on the image data,
A rotating polygon mirror that has a plurality of reflecting surfaces and deflects the light output from the light source using the plurality of reflecting surfaces by rotating to scan the photoconductor,
A light receiving unit that receives the light deflected by the rotating polygon mirror,
First output means for outputting a predetermined signal in accordance with the reception of the light by the light receiving unit,
Has,
The generation means,
During the period from the start of rotation of the rotary polygon mirror to the rotation speed of the rotary polygon mirror reaching a predetermined speed, a time interval between adjacent pulses of the predetermined signal output from the first output unit is determined. Specifying means for specifying a reflection surface used for scanning the photosensitive member among the plurality of reflection surfaces,
The image data corresponding to each of a plurality of scanning lines constituting an image for one recording medium is corrected by correction data corresponding to the reflection surface corresponding to each scanning line, and the corrected one surface of the recording medium is corrected. Correction means for outputting the image data of the minute to the image forming means in accordance with the predetermined signal output from the first output means;
An image forming apparatus comprising:

Images