JP2006181964A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continue an image-formation operation even if the abnormal detection of a reference signal arises. <P>SOLUTION: If the reference signal is formed, a synchronous reference signal is formed based on the reference signal. If the reference signal is not formed, a false reference signal is formed based on the timing acquired beforehand and at the same time the synchronous reference signal is formed based on the false reference signal. If the reference signal is formed, the reference signal, or if the reference signal is not formed, the false reference signal as its alternative signal, is transmitted to the clock formation section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and in particular, generates a reference signal INDEX (index signal) for detecting a light beam from a light source to a photoconductor to define a writing start position in the main scanning direction. The present invention relates to an image forming apparatus having a function of

  An image forming apparatus that forms an image of one line in the main scanning direction according to image data, and forms an image for one page by repeating image formation for each line in the main scanning direction in the sub-scanning direction. Are known.

  As an example, in an electrophotographic image forming apparatus, a laser beam modulated in accordance with image data is scanned in the main scanning direction, and at the same time, an image carrier (photosensitive member) that rotates in the sub scanning direction. An image is formed on the body drum by the beam light. In this case, the light beam is modulated with image data with reference to a clock signal (pixel clock) called a dot clock.

  In this output image forming apparatus, a part of the beam light scanned from the light source to the photosensitive member is detected by the sensor, and a reference signal INDEX (index signal) for defining the writing start position in the main scanning direction is generated. It has a function.

  Usually, a laser beam for generating a reference signal is forcibly lit outside the effective image area, and a writing reference signal is generated by detecting the beam with a light detection device. Here, when the laser beam is not detected for some reason, the laser beam continues to be lit. When a predetermined time elapses, an abnormality is detected and the image forming operation is forcibly stopped.

For example, Patent Document 1 below describes a solution to the above problem.
JP 2003-89237 A (first page, FIG. 1)

    According to Japanese Patent Laid-Open No. 2003-89237 described above, in a multi-beam type image forming apparatus having a plurality of beams, when a main scanning direction writing reference signal detection abnormality occurs, only a beam in which no reference signal detection abnormality has occurred. By using the polygon motor and changing the number of revolutions of the polygon motor, it is possible to reduce the writing speed in the sub-scanning direction and continue the image forming operation.

  However, although it is a provisional image forming operation in the case where only the main scanning direction writing reference signal detection is not operating normally, the writing speed in the sub-scanning direction is lowered, so that there is a problem that productivity is lowered. Further, since the laser diode (LD) on the side where the reference signal detection is not correctly performed is not used, the LD usage frequency is biased and the laser power of the two laser diodes varies. Will also occur.

  In addition, if the pixel clock generated based on the logic of the reference signal detection signal that controls forced laser beam lighting and the reference signal is a clock (mask clock) that is temporarily stopped when the reference signal is detected, the clock generator is used as a reference. Since the clock is stopped until the signal is input, there is also a problem that the image forming operation cannot be continued simply by ignoring the state of the reference signal detection abnormality.

  Further, the above-described one in Patent Document 1 is based on the premise that the reference signal is normally detected on the side of one laser diode in the multi-beam type image forming apparatus, so that a single laser diode is used. It cannot be applied to existing image forming apparatuses. Further, when the reference signals of both laser diodes are no longer detected in the multi-beam type image forming apparatus, the image forming apparatus is also stopped.

  The present invention has been made in view of the above-described problems. When a part of light beams scanned from a light source to a photosensitive member is detected by a sensor, a reference signal for defining a writing start position in the main scanning direction is generated. Another object of the present invention is to realize an image forming apparatus capable of continuing an image forming operation without reducing productivity even when a reference signal detection abnormality occurs.

That is, the present invention as means for solving the problems is as described below.
(1) According to the first aspect of the present invention, an optical scanning unit that deflects the beam light from the light source and scans the surface of the photosensitive member in the main scanning direction, and a writing start position in the main scanning direction by detecting the beam light A reference signal detection unit that generates a reference signal for defining, a clock generation unit that generates and outputs a pixel clock when the reference signal is supplied, and a reference signal acquired in advance when the reference signal is not generated A control unit for generating a pseudo reference signal based on timing; generating the reference signal when the reference signal is generated; generating the clock as the substitute reference signal when the reference signal is not generated; A reference signal selection unit to be supplied to the image processing unit, an image processing unit that generates image data for driving the light source based on the pixel clock, and an image processing unit based on the image data and the pixel clock. A light source driver for driving to output a beam light corresponding to the image data from the light source, an image forming apparatus having a.

  (2) According to the second aspect of the present invention, an optical scanning unit that deflects the beam light from the light source and scans the photosensitive member surface in the main scanning direction, and detects the beam light and sets the writing start position in the main scanning direction. A reference signal detector for generating a reference signal for defining; a clock generator for generating and outputting a pixel clock when the reference signal is supplied; and a reference signal when the reference signal is generated A control unit that generates a synchronization reference signal based on the pseudo reference signal based on the pseudo reference signal and generates a pseudo reference signal based on a timing acquired in advance when the reference signal is not generated A reference signal selection unit that supplies the reference signal to the clock generation unit when the reference signal is generated, and the pseudo reference signal as an alternative signal when the reference signal is not generated; An image processing unit that generates image data for driving the light source based on the pixel clock and the synchronization reference signal, and a light beam corresponding to the image data from the light source based on the image data and the pixel clock. An image forming apparatus having a light source driving unit that drives to output.

  (3) The invention according to claim 3 is characterized in that the clock generator stops outputting the pixel clock when the supply of the reference signal is stopped. An image forming apparatus.

  (4) In the invention according to claim 4, the clock generation unit stops outputting the pixel clock when the supply of the reference signal from the reference signal selection unit is stopped, and the pseudo signal is output from the reference signal selection unit. 3. The image forming apparatus according to claim 1, wherein the output of the pixel clock is resumed when a reference signal is supplied as the reference signal.

  (5) In the invention according to claim 5, the control unit switches from the normal operation mode to the provisional operation mode when the reference signal is not detected for a predetermined period, and generates the pseudo reference signal based on the timing acquired in advance. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

  (6) The invention according to claim 6 includes a display unit for displaying various information, and the control unit operates in a provisional operation mode when a pseudo reference signal is generated as a substitute signal for the reference signal. 6. The image forming apparatus according to claim 1, wherein the image forming apparatus displays on the display unit.

As described above, according to the present invention, the following effects can be obtained.
(1) According to the first aspect of the present invention, the light beam from the light source is deflected to scan the photosensitive member surface in the main scanning direction, and the beam light is detected to define the writing start position in the main scanning direction. Generating a reference signal, generating and outputting a pixel clock when the reference signal is supplied, generating image data for driving the light source based on the pixel clock, and generating the image data and the pixel clock; If the reference signal is not generated when the beam light corresponding to the image data is output from the light source based on the pseudo light source, the pseudo reference signal is generated based on the timing acquired in advance, and the reference signal is generated. In some cases, the reference signal is supplied to the clock generation unit as the substitute signal when the reference signal is not generated.

  As a result, when a reference signal for detecting a part of the light beam scanned from the light source to the photosensitive member by the sensor and generating the reference signal for defining the writing start position in the main scanning direction has occurred, Even so, since the pseudo reference signal generated based on the timing acquired in advance is used as a substitute signal for the reference signal, the pixel clock is generated in the same way as in the normal state, which reduces productivity. It is possible to continue the image forming operation without doing so.

  (2) In the invention described in claim 2, the light beam from the light source is deflected to scan the photosensitive member surface in the main scanning direction, and the beam light is detected to define the writing start position in the main scanning direction. Generating a reference signal; generating and outputting a pixel clock when the reference signal is supplied; generating image data for driving the light source based on the pixel clock and the synchronization reference signal; and When outputting the light beam according to the image data from the light source based on the pixel clock, if the reference signal is generated, a synchronization reference signal is generated based on the reference signal, and the reference When the signal is not generated, the pseudo reference signal is generated based on the timing acquired in advance and the synchronization reference signal is generated based on the pseudo reference signal, and the reference signal is generated. The said reference signal, said pseudo reference signal as a substitute signal when the reference signal is not generated, is supplied to the clock generator.

  As a result, when a reference signal for detecting a part of the light beam scanned from the light source to the photosensitive member by the sensor and generating the reference signal for defining the writing start position in the main scanning direction has occurred, Even so, since the pseudo reference signal generated based on the timing acquired in advance is used as a substitute signal for the reference signal, the pixel clock is generated in the same way as in the normal state, which reduces productivity. It is possible to continue the image forming operation without doing so.

(3) In the invention described in claim 3, in the above (1) or (2), when the supply of the reference signal is stopped, the clock generator stops outputting the pixel clock.
That is, even when the pixel clock is temporarily stopped at the time of detecting the reference signal (mask clock), the pseudo reference signal generated based on the timing acquired in advance is used as an alternative signal for the reference signal. A pixel clock is generated as in the normal state, and it is possible to continue the image forming operation without reducing productivity.

  (4) In the invention according to claim 4, in the above (1) or (2), the clock generation unit stops outputting the pixel clock when the supply of the reference signal from the reference signal selection unit is stopped. Then, when the pseudo reference signal is supplied as the reference signal from the reference signal selection unit, the output of the pixel clock is resumed.

  In other words, since this is a clock (mask clock) that temporarily stops the pixel clock when the reference signal is detected, even if the pixel clock is temporarily stopped due to a reference signal detection error, the timing is acquired in advance. Since the pseudo reference signal generated based on the reference signal is used as a substitute signal for the reference signal, a pixel clock is generated as in the normal state, and the image forming operation can be continued without reducing productivity. It becomes possible.

  (5) In the invention according to claim 5, in the above (1) to (4), when the reference signal is not detected for a predetermined period, the normal operation mode is switched to the provisional operation mode, and based on the timing acquired in advance. Generate a pseudo reference signal.

  In other words, since the pixel clock is temporarily stopped when the reference signal is detected (mask clock), even if the pixel clock is temporarily stopped due to a reference signal detection error, provisional operation is started from the normal operation mode. Since the pseudo reference signal generated based on the timing obtained by switching to the mode and used in advance is used as the substitute signal for the reference signal, the pixel clock is generated in the same way as in the normal state, which reduces the productivity. It is possible to continue the image forming operation.

  (6) In the invention described in claim 6, in the above (1) to (5), when a pseudo-reference signal is generated as a substitute signal for the reference signal, the display unit displaying various information is provisionally. The display unit displays that it is operating in the operation mode.

  As a result, when a reference signal for detecting a part of the light beam scanned from the light source to the photosensitive member by the sensor and generating the reference signal for defining the writing start position in the main scanning direction has occurred, Even so, since the pseudo reference signal generated based on the timing acquired in advance is used as a substitute signal for the reference signal, the pixel clock is generated in the same way as in the normal state, which reduces productivity. Thus, it is possible to continue the image forming operation without making it clear, and it is possible to clearly indicate that the operation is performed with the pseudo reference signal as the provisional operation mode.

  The best mode (embodiment) for carrying out the present invention will be described below in detail with reference to the drawings. An image forming apparatus to which the present embodiment is applied is configured to deflect a light beam from a light source to scan a photoconductor surface in a main scanning direction, detect the light beam, and define a writing start position in the main scanning direction. Generating a reference signal; generating and outputting a pixel clock when the reference signal is supplied; generating image data for driving the light source based on the pixel clock and the synchronization reference signal; and And an image forming apparatus that outputs a beam light corresponding to the image data from the light source based on the pixel clock.

Hereinafter, the electrical configuration of the first embodiment of the multi-beam image forming apparatus 100 of the present embodiment will be described in detail with reference to FIG.
In this embodiment, when a reference signal for defining a writing start position in the main scanning direction is generated by a sensor by detecting a part of the beam light scanned from the light source to the photosensitive member, an abnormality in detection of the reference signal is detected. Even when this occurs, the description will focus on the structural requirements necessary to perform the operation for continuing the image forming operation without reducing the productivity as in the normal case. Therefore, it is common for an image forming apparatus, and well-known constituent elements are omitted.

  Reference numeral 105 denotes a display unit that displays various states of the image forming apparatus 100, various information, and various messages. A control unit 110 is configured by a CPU or the like to control each unit of the image forming apparatus 100.

  The control unit 110 includes an overall control unit 111 that performs overall control of the apparatus, an operation mode control unit 112 that controls an operation mode such as a normal operation mode or a provisional operation mode, and an LD control unit that controls a light source (LD). 113 and a synchronization reference signal generation unit 114 that generates a synchronization reference signal based on a reference signal or a pseudo reference signal.

  The operation mode control unit 112 generates a normal operation mode and a provisional operation mode determination signal DMY_MOD when the reference signal detection is abnormal, and supplies it to each function unit in the control unit 110 and each circuit outside the control unit 110. In addition, the LD control unit 113 supplies an LD control signal to the LD drive unit (not shown), and also supplies a reference signal detection signal IND_SRH to the pixel clock generation unit.

  The synchronization reference signal generation unit 114 generates a signal LSYNC synchronized with the pixel clock MSK_CLK with respect to the reference signal INDEX, and supplies the signal LSYNC to the image processing unit 140. The pseudo reference signal generation unit 115 is based on the operation mode determination signal DMY_MOD supplied from the operation mode control unit in order to prevent the pixel clock MSK_CLK from being stopped when a reference signal detection abnormality occurs. (Pseudo reference signal) DMY_IND is generated. It should be noted that each control unit operates using DMY_IND as a reference signal only in the provisional operation mode.

  That is, the control unit 110 switches the operation mode from the normal operation mode to the temporary operation mode even when the pixel clock is temporarily stopped due to the reference signal detection abnormality, and is based on the timing acquired in advance. To generate a pseudo reference signal and use the pseudo reference signal as a substitute signal for the reference signal.

  A clock generation unit 120 generates a pixel clock MSK_CLK as a mask clock that is temporarily stopped when the reference signal is detected from the original write clock PCLK based on the logic of the reference signal INDEX and the reference signal detection signal IND_SRH that controls forced laser beam lighting. It is. The clock generation unit 120 includes a write clock generation unit 121 that generates an original write clock PCLK, and a pixel clock generation unit 122 that generates a pixel clock MSK_CLK as a mask clock.

  Here, the pixel clock generation unit 122 generates a pixel clock synchronized with the write clock PCLK. Based on the logic of the reference signal detection signal IND_SRH and the reference signal INDEX generated when generating the reference signal INDEX, a pixel clock in which the write clock PCLK is temporarily stopped during the detection of the reference signal is generated, and the image forming apparatus is used as the pixel clock MSK_CLK. Use at 100. The pixel clock MSK_CLK maintains a state where the clock is temporarily stopped when the reference signal INDEX is not input.

  Reference numeral 130 denotes a reference signal selection unit 130 that selects a reference signal or a pseudo reference signal. Based on the operation mode determination signal DMY_MOD from the control unit 110, the reference signal INDEX is used in the normal operation mode, and the pseudo reference signal DMY_IND is used in the provisional operation mode. Is supplied to the clock generation unit 120 (pixel clock generation unit 122).

  An image processing unit 140 generates image data for driving an LD as a light source based on the pixel clock and the synchronization reference signal. The image processing unit 140 generates a signal LSYNC generated by the synchronization reference signal generation unit 114 in synchronization with the pixel signal MSK_CLK with respect to the reference signal INDEX, and processes image data in synchronization with the LSYNC. To do.

  An LD driving unit 150 drives the LD 160 as a light source, and drives the LD 160 so that beam light corresponding to the image data is output from the light source based on the image data and the pixel clock.

  Reference numeral 170 denotes a polygon mirror (rotating polygonal mirror) that deflects the beam light from the LD 160 as a light source in the main scanning direction and performs exposure with the beam light that scans the surface of the photosensitive drum 180 in the main scanning direction.

  In 180, an electrostatic latent image corresponding to image data is formed by exposure of light beams scanned in the main scanning direction and rotation operation in the sub-scanning direction, and the electrostatic latent image is developed to form a toner image. This is a photosensitive drum as an image carrier. The charging for forming the electrostatic latent image, the toner image formation by developing the electrostatic latent image, the transfer of the toner image onto the recording paper, the fixing of the toner image on the recording paper, etc. are generally used as an image forming apparatus. Therefore, the description is omitted.

  Reference numeral 190 denotes a reference signal detector that detects a light beam and generates a reference signal for defining a writing start position in the main scanning direction. That is, in the reference signal detection unit 190, the laser beam that is forcibly emitted for detecting the reference signal is detected by an optical sensor and converted into an electric signal to generate the reference signal INDEX. Normally, writing control in the main scanning direction is performed based on the reference signal INDEX.

  Hereinafter, the operation of the image forming apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG. 2 and the timing charts of FIGS. 3 and 4. Here, FIG. 2 roughly shows the overall operation of the image forming apparatus 100 of the present embodiment, and there are a normal operation mode and a provisional operation mode. 3 shows the operation timing in the normal operation mode, and the time chart in FIG. 4 shows the operation timing in the provisional operation mode.

<Normal operation mode>
First, an operation based on control from the control unit 110 in the image forming apparatus 100 in the normal operation mode will be described with reference to FIG.

  The write clock generation unit 121 in the clock generation unit 120 generates a continuous write clock as shown in FIG. 3C for the basic operation of each unit in the image forming apparatus 100. In response to this write clock, the pixel clock generation unit 122 generates a pixel clock as the mask clock MSK_CLK (FIG. 3E) (S1 in FIG. 2).

  Here, the reference signal detection signal IND_SRH (FIG. 3B) for generating the reference signal INDEX is supplied to the pixel clock generation unit 122 from the control unit 110, and the reference signal detection signal IND_SRH is valid (High). The pixel clock mask control signal CS_MSK (FIG. 3 (d)) becomes valid (Low level (hereinafter L level)) in response to the change to the level (hereinafter H level)) (S2 in FIG. 2).

  The pixel clock MSK_CLK (FIG. 3E) outputs the write clock PCLK as it is when the pixel clock mask control signal CS_MSK is invalid (H level), and is at the L level when the pixel clock mask control signal CS_MSK is valid (L level). (Output stop state, (1) in FIGS. 3D and 3E) is held (S3 in FIG. 2).

  When the reference signal INDEX (FIG. 3 (a)) is generated (Y in FIG. 2S) while the pixel clock MSK_CLK is stopped (FIG. 3 (1)), when its rise (change from H to L) occurs, The pixel clock mask control signal CS_MSK returns to invalid (H level). Accordingly, since the pixel clock mask control signal CS_MSK changes to the H level thereafter, the output of the pixel clock MSK_CLK corresponding to the write clock PCLK is resumed (S5 in FIG. 2).

  When the reference signal INDEX (FIG. 3 (a)) rises (changes from L to H) while the pixel clock MSK_CLK is stopped (FIG. 3 (1)), the clear signal CNT_CLR (FIG. 3) of the internal counter CNT of the control unit 110 is generated. 3 (g)) becomes valid for one cycle of the write clock PCLK.

  In response to the internal counter clear signal CNT_CLR valid (H level), the value of the internal counter CNT of the control unit 110 is reset to the minimum value “1” (FIGS. 3G, 3K, and 2).

  In this normal operation, the internal counter CNT counts +1 in synchronization with the rising edge of the write clock PCLK. The internal counter CNT count value “N1” when the internal counter clear signal CNT_CLR is valid is taken in by the internal counter value holding signal CNT_HLD (FIG. 3 (l)), and the count value “N1” is the value until the next internal counter clear signal CNT_CLR is valid. Hold.

  That is, the count value “N1” serves as a means for measuring the interval between the input of the reference signal INDEX and the input of the next reference signal INDEX. In the initial state such as when the image forming operation starts or when returning from the stopped state, the internal counter CNT is stopped when the first reference signal INDEX is input, so that the value cannot be taken into CNT_HLD, and the second reference signal INDEX Since the count value cannot be compared with the internal counter CNT at the time of input, the initial value of the internal count value holding signal CNT_HLD is set in advance by register setting.

  Usually, since the interval from the input of the reference signal INDEX to the input of the next reference signal INDEX is constant, the initial value is set based on the specifications of the image forming apparatus. The internal count value holding signal CNT_HLD can fetch the count value when the count value holding selection signal CNT_SEL (FIG. 3 (m)) is at the L level.

  The count value holding selection signal CNT_SEL (FIG. 3 (m)) is H level in the initial state, so that the counter value fetching is prohibited, but the internal counter clear signal CNT_CLR is valid (H level), and the count value holding selection signal CNT_SEL is L It changes to the level, and the internal count value can be taken in (FIGS. 3 (i) (m) (3)).

  Further, the synchronization reference signal LSYNC (FIG. 3 (f)) from the synchronization reference signal generation unit 114 is a register signal based on the timing at which the pixel clock mask control signal CS_MSK changes to H level and the pixel clock MSK_CLK starts to be output. It is generated by controlling LS_START and LS_WIDTH settings (FIGS. 3 (f) and (4)).

In the control unit 110, the interval from the reference signal INDEX to the synchronization reference signal LSYNC is measured using the internal counter CNT and the internal counter clear signal CNT_CLR.
Here, the rising signal LSY_UP_1ST (FIG. 3 (h)) of the synchronization reference signal LSYNC is generated, and the rising signal LSYNC_UP_1ST of the synchronization reference signal LSYNC is generated from the H level (FIG. 3 (k) (2)) of the internal counter clear signal CNT_CLR. The time is counted up to the H level, and the count value is held in LS_DLY_CNT (FIG. 3 (j)). In addition, the next reference signal INDEX is received, and the time is measured again in the same manner. In the specific example of FIG. 3, the count value “7” is held.

  This LS_DLY_CNT (FIG. 3 (j)) is data used when generating the synchronization reference signal LSYNC in a provisional operation mode to be described later. That is, on the premise of use in the provisional operation mode, provisional counter clear signal IND_DIFF (FIG. 3 (n)) and provisional counter DIFF_CNT (FIG. 3 (o)) are generated, and even in the normal operation mode, provisional A counter operation is performed by the counter DIFF_CNT (FIG. 3 (o) (6)). The temporary counter clear signal IND_DIFF changes to the H level in response to the H level of the internal counter clear signal CNT_CLR when the count value holding selection signal CNT_SEL is at the H level (FIG. 3 (5)).

  When CNT_SEL is at the L level, the value of the internal counter CNT and the value of the internal count value holding signal CNT_HLD are compared and matched (FIGS. 3 (m) and (7)), and the signal changes to the H level (FIG. 3). (N) (8)). Then, the provisional counter DIFF_CNT receives the provisional counter clear signal IND_DIFF and starts counter clearing and counting (FIG. 3 (o) (9)).

As described above, under the control from the control unit 110, a signal for use in the provisional operation mode described later is activated in advance even in the normal operation mode.
<Provisional operation mode>
Here, an operation based on control from the control unit 110 in the image forming apparatus 100 in the provisional operation mode will be described with reference to FIG. That is, FIG. 4 shows a timing chart for the transition operation from the normal operation mode to the temporary operation mode due to the reference signal detection abnormality.

  The write clock generation unit 121 inside the clock generation unit 120 generates a continuous write clock as shown in FIG. 4C for the basic operation of each unit in the image forming apparatus 100. In response to this write clock, the pixel clock generator 122 generates a pixel clock as a mask clock MSK_CLK (FIG. 4E) (S1 in FIG. 2).

  Here, the reference signal detection signal IND_SRH (FIG. 4B) for generating the reference signal INDEX is supplied from the control unit 110 to the pixel clock generation unit 122, and the reference signal detection signal IND_SRH is valid (H The pixel clock mask control signal CS_MSK (FIG. 4 (d)) becomes valid (L level) in response to the change in level (FIG. 2S2).

  The pixel clock MSK_CLK (FIG. 4E) outputs the write clock PCLK as it is when the pixel clock mask control signal CS_MSK is invalid (H level), and is at the L level when the pixel clock mask control signal CS_MSK is valid (L level). (Output stop state, (1) in FIGS. 4D and 4E) is held (S3 in FIG. 2).

  Here, even if the reference signal detection signal IND_SRH becomes H level and the reference signal INDEX is ready for detection, if the reference signal INDEX is not input (N in FIG. 2S4) (FIG. 4 (1) broken line portion), the reference signal INDEX Since the internal counter clear signal CNT_CLR generated based on the above is not generated (FIG. 4 (g) (1 ′)), the value of the internal counter CNT of the control unit 110 is originally counted at the timing when the reference signal INDEX is input. The value is not reset and continues to count up as it is (FIGS. 4 (g) (k) (2)).

  Here, although the internal counter clear signal CNT_CLR cannot be generated (FIG. 4 (g), broken line (1 ′)), for the temporary counter clear signal IND_DIFF, the count value of the internal counter CNT and the value of the internal count value holding signal CNT_HLD match. When this happens, it becomes H level (FIGS. 4 (n) (3)), the count value of the temporary counter DIFF_CNT is cleared, and the count starts again from the minimum count value (FIGS. 4 (o) (4)).

  When there is no input of the reference signal INDEX for a predetermined period by register setting, the reference signal detection abnormality signal IND_SRH_ERR becomes valid (H level) by the operation mode control unit 121 (FIG. 4 (p) (5)).

 In response to the validity of the reference signal detection abnormality signal IND_SRH_ERR (FIG. 4 (p) (5)), the count value holding selection signal CNT_SEL becomes H level (FIG. 4 (m) (6)), and the internal counter holding signal CNT_HLD Count value fetching is prohibited, and provisional operation mode signal DMY_MOD is made valid (H level) (FIGS. 4 (q) and (7)).

   The reference signal detection signal IND_SRH (FIG. 4B) is also set to the L level in response to the provisional operation mode signal DMY_MOD being valid (FIGS. 4B and 8). In other words, when the provisional operation mode signal DMY_MOD is valid, the operation mode control unit 112 controls each unit so as to operate as a provisional operation mode (S6 in FIG. 2).

  Here, the provisional operation mode signal DNY_MODE is received, and the internal counter CNT stops the count operation (FIGS. 4 (k) and (9)). In addition, although the reference signal detection abnormality signal IND_SRH_ERR is received and the transition to the temporary operation mode is automatically performed, the provisional operation mode transition presence / absence is set in the register setting, and the reference signal detection abnormality signal is set when the provisional operation mode transition is not set. The image forming operation may be stopped when IND_SRH_ERR is valid (similar to when a reference signal detection abnormality occurs in normal operation). In addition, when switching is possible by register setting, a maintenance person may switch the provisional operation mode transition setting from the operation unit.

  By transitioning to the provisional operation mode, the counter used to generate the reference signal detection signal IND_SRH is switched from the internal counter CNT (FIG. 4 (k)) to the provisional counter DIFF_CNT (FIG. 4 (o)), and the reference is based on the DIFF_CNT count value. A signal detection signal IND_SRH is generated (FIGS. 4B and 10).

  The temporary counter clear signal IND_DIFF (FIG. 4 (n)) compares the internal count value holding signal CNT_HLD (FIG. 4 (l)) with the temporary counter DIFF_CNT (FIG. 4 (o)). 4 (n) (11)), the temporary counter DIFF_CNT count value is cleared.

  Since the value “NQ” held in the internal count value holding signal CNT_HLD is the cycle of the reference signal INDEX in the original normal mode, the count value of the provisional counter DIFF_CNT is cleared in the cycle of “NQ”. It operates at the same timing as the original reference signal INDEX.

  In response to the rise of the temporary counter clear signal IND_DIFF (FIG. 4 (n) (11)), a temporary reference signal (pseudo reference signal) DMY_IND is generated (FIGS. 4 (r) and (12)). The start timing of the temporary reference signal <pseudo reference signal> DMY_IND is controlled by the rising edge of IND_DIFF, and the end timing is controlled by setting the signal width in the register DIND_WIDTH and comparing it with the temporary counter DIFF_CNT count value.

  By inputting a temporary reference signal (pseudo reference signal) DMY_IND as a substitute signal for the reference signal INDEX to the pixel clock generation unit (shown in FIG. 1) via the reference signal selection unit 130, the pixel clock mask control signal CS_MSK is obtained. It becomes invalid (FIGS. 4D and 13), and the output of the pixel clock MSK_CLK is restarted (FIGS. 4E and 14).

  In the normal operation mode, the synchronization reference signal LSYNC is generated based on the output start timing of the pixel clock MSK_CLK (FIG. 3 (f) (4)), but in the temporary operation mode, the temporary counter clear signal IND_DIFF (FIG. 4 (n) ( 11)). In the normal operation mode, the interval from the internal counter clear signal to the start of LSYNC is counted, and when the value held in LS_DLY_CNT is compared with the value of the temporary counter DIFF_CNT, the synchronization reference signal LSYNC is started (FIG. 4 (f) (15 )).

  The LSYNC signal width is controlled by using the register LS_WIDTH set value in the same manner as in the normal operation mode and comparing with the temporary internal counter DIFF_CNT count value. By measuring the interval of the reference signal in advance in the normal operation mode and using it in the provisional operation mode, it is possible to prevent the operation timing shift due to the difference in the mode, and the image forming operation by the provisional reference signal (pseudo reference signal) The image misalignment can be minimized.

  Note that the continuation of the image forming operation in the provisional operation mode (S6 in FIG. 2) is a provisional measure based on the provisional reference signal <pseudo reference signal> created in a pseudo manner, so that the provisional mode is being used on the display unit or the like. Is preferably displayed (S7 in FIG. 2). In addition, it is further desirable to display on the display section that maintenance is necessary, and to encourage the user to perform maintenance.

  In the case of continuing the image forming operation in the above provisional operation mode, the pixel clock is stopped by image formation for one main scanning line immediately after the reference signal INDEX is not detected, but the pseudo reference signal is output from the next main scanning line. As a result, the pixel clock is restarted, so that an image forming operation comparable to that in the normal operation mode is continued.

  In the above embodiment, the number of laser beams (the number of light sources) is not mentioned. However, according to this embodiment, the write reference signal can be used for one laser beam or a plurality of laser beams. It is possible to continue the image forming operation when a detection abnormality occurs. Therefore, when using a plurality of light sources, since any one of the light sources is not stopped, there is no problem such as a decrease in speed in the sub-scanning direction and a variation in use time of the plurality of light sources. . Further, even if a reference signal detection abnormality occurs for all of the plurality of light sources, it is possible to continue image formation without any problem.

  As described above in detail, in an image forming apparatus using a mask clock as a pixel clock, even if a writing reference signal detection abnormality occurs, a provisional reference signal (pseudo reference signal) is generated and an image is formed as a reference signal. As a result, the image forming operation can be continued. In the past, if a write reference signal detection error occurred, the machine stopped, and it was impossible to use the machine until the maintenance person performed the maintenance of the machine. The machine can be temporarily used by generating the reference signal (pseudo reference signal).

  When the reference signal detection abnormality is recovered for some reason and the reference signal INDEX is normally detected again, the state automatically returns to the state shown in the time chart of FIG. The operation may be continued as follows.

  However, once the temporary operation mode is entered, it is considered that some abnormality exists in any part. Therefore, even if the reference signal detection abnormality is recovered, the error display should be continued on the display unit. Also good.

<Other embodiments>
In the above embodiment, an electrophotographic image forming apparatus using light beams has been described, but the present invention is not limited to this. For example, each embodiment of the present invention can be applied to various image forming apparatuses such as a laser imager that exposes photographic paper using light beams, and good results can be obtained.

1 is a block diagram illustrating an electrical configuration of an image forming apparatus according to an embodiment of the present invention. 6 is a flowchart illustrating an overall operation state of the operation of the image forming apparatus according to the embodiment of the present invention. 6 is a time chart for explaining an overall operation state in a normal operation mode of the image forming apparatus according to the embodiment of the present invention. 6 is a time chart for explaining an overall operation state in a provisional operation mode of the image forming apparatus according to the embodiment of the present disclosure.

Explanation of symbols

100 Image forming apparatus 110 CPU
110 Image processing unit 120 Clock generation unit 130 Reference signal selection unit 140 Image processing unit 150 LD driving unit 160 LD light source (LD)
170 Polygon mirror 180 Photosensitive drum 190 Reference signal detector (index sensor)

Claims (6)

An optical scanning unit that deflects the light beam from the light source and scans the surface of the photoreceptor in the main scanning direction;
A reference signal detector that detects the light beam and generates a reference signal for defining a writing start position in the main scanning direction;
A clock generation unit that generates and outputs a pixel clock when the reference signal is supplied; and a control unit that generates a pseudo reference signal based on a timing acquired in advance when the reference signal is not generated;
A reference signal selection unit that supplies the reference signal to the clock generation unit when the reference signal is generated, and the pseudo reference signal as an alternative signal when the reference signal is not generated;
An image processing unit for generating image data for driving the light source based on the pixel clock;
A light source driving unit configured to drive the light source according to the image data from the light source based on the image data and the pixel clock;
An image forming apparatus. An optical scanning unit that deflects the light beam from the light source and scans the surface of the photoreceptor in the main scanning direction;
A reference signal detector that detects the light beam and generates a reference signal for defining a writing start position in the main scanning direction;
A clock generator that generates and outputs a pixel clock when the reference signal is supplied;
When the reference signal is generated, a synchronization reference signal is generated based on the reference signal, and when the reference signal is not generated, a pseudo reference signal is generated based on a previously acquired timing and the pseudo reference is generated. A control unit that generates a synchronization reference signal based on the signal;
A reference signal selection unit that supplies the reference signal to the clock generation unit when the reference signal is generated, and the pseudo reference signal as an alternative signal when the reference signal is not generated;
An image processing unit for generating image data for driving the light source based on the pixel clock and the synchronization reference signal;
A light source driving unit configured to drive the light source according to the image data from the light source based on the image data and the pixel clock;
An image forming apparatus. The clock generation unit stops outputting the pixel clock when the supply of the reference signal is stopped;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The clock generation unit stops output of a pixel clock when the supply of the reference signal from the reference signal selection unit is stopped, and the pseudo reference signal is supplied as the reference signal from the reference signal selection unit Restart the pixel clock output,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The control unit switches from the normal operation mode to the temporary operation mode when the reference signal is not detected for a predetermined period, and generates a pseudo reference signal based on a timing acquired in advance.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. It has a display unit that displays various information,
When the control unit is generating a pseudo reference signal as an alternative signal to the reference signal, the control unit displays on the display unit that it is operating in a provisional operation mode.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.